A digital phase-measurement interferometer using a tunable SHG blue laser at 410nm was developed. This system enables us to test high NA lenses used in high-density optical storage devices. Excellent features such as wavelength tunability, narrow spectral linewidth, and wavelength stability, make the SHG laser very suitable as a light source for a phase-shifting interferometer working at blue-violet wavelength region. We investigated the tuning characteristic of the SHG laser as a function of DBR-section current and found that the wavelength-changing ratio was 0.0017nm/mA. An unbalanced Twyman-Green interferometer with the SHG laser was composed to measure the transmitted wavefront of an optical pickup lens with a NA of 0.85. The theory and experimental results are presented.

A super oblique incidence interferometer is proposed by using an anti-reflection prism with sub-wavelength structure. Since the sensitivity of interferogram depends on incident angle it can be achieved lower than ordinary interferometer. A sub-wavelength structure on the prism works an increasing transmittance under the condition of the vicinity of critical angle. A shape of this structure is a triangle with sub-wavelength order of height and width periodically and works matching a difference reflective index between prism and air. The experimental results of transmittance are agreed well with the calculated results by the rigorous coupled wave analysis. Its incident angle of the oblique interferogram can be achieved at 86 degrees. Simulation and experimental results are shown.

A method is proposed for accurately measuring a sectional profile of a thread gauge. In this method a sinusoidally vibrating sinusoidal intensity (SVSI) is used to generate an exact spatial scale along one direction. Lights from top points of a thread gauge surface are extracted by spatial filtering in an afocal imaging system to form an image of the top points. A time-varying signal is detected in the image, and a sectional profile of the thread gauge is measured from the phase of the detected signal on a position where the amplitude of the signal has a maximum value. Detection of the amplitude and the phase is carried out easily and exactly with sinusoidal phase-modulating interferometry.

A profile measurement technique for objects with spatially isolated surfaces is presented. The technique is based on the Fourier fringe analysis combined with temporal phase unwrapping. A sequence of sinusoidal fringe patterns with a varying pitch is projected onto objects, and the temporal variation of the fringe signal is recorded with a CCD camera. The phase of the temporal fringe signal is detected at each pixel by the Fourier transform method, and is temporally phase unwrapped, independently from other pixels. The temporal frequency of the fringe signal estimated from the time slope of the unwrapped phase provides the information about the absolute surface heights of the objects. It will be shown that, because of its filtering function that can exclude higher order harmonics, the Fourier transform method is more robust to the nonlinear characteristics of a LCD projector and a CCD image sensor, than the phase shift technique that assumes a pure sinusoidal fringe signal. The measurement of objects with large discontinuities and/or spatially isolated surfaces is demonstrated by experiment.

The rough surface of a aluminum cylindrical drum cut by turning tool is measured with a fast scanning method by detecting angular deflection of a laser beam. Reflection pattern from the surface extended into a large region, and contained two kinds of components of narrow and wide patterns. To detect rough surface's slope, the barycentric position of the wide pattern was measured with a PSD, and a beam diameter of 5mm on the surface was adopted. After a proportionality coefficient to convert from PSD output to the surface's slope was determined, an one-dimensional surface profile measurement of the rough surface was performed without a vibration isolator. Measurement error was estimated to be 0.27μm.

Coherent all-solid-state light source in deep ultra-violet (DUV) region is widely required for many applications that include sensing and imaging. One of the promising candidates is a combination of an infrared solid-state laser and nonlinear optical crystals that enable DUV generation. Recently, crystal quartz is remarked as a nonlinear optical material of quasi-phase matching (QPM) in addition to the existing nonlinear optical crystals. It is an excellent optical material that has good transparency to 160nm and high damage threshold to laser light. It also has the χ⁽²⁾ coefficient that allows optical second harmonic generation (SHG). Previously, it is not recognized as a practical nonlinear material due to the impossibility of the birefringent phase matching (BPM). In this work we fabricated a 125 mm-period twin structure for third-order QPM-SHG of 1064nm and performed the SHG experiments.

Based on three-fiber optic Moiré interferometric technique, a novel profilometry has been proposed and demonstrated in this paper. The square and hexagon grid interferometric fringe pattern formed by fiber optic interferometric grid generator have been designed and performed. The designing and realizing methods of the fiber optic interferometric grid pattern by using three PM fibers are discussed. Theoretically, the three-fiber coherence optical field intensity distribution has been deduced and the simulation results are also presented. The configuration of the fiber optic Moiré three-dimensional shape measuring system is introduced. For example, a small half-sphere has been used to demonstrate how to reconstruct the three-dimensional shape by fiber optic Moiré interferometric technique.

Rocket engine is a hard-core part of aerospace transportation and thrusting system, whose research and development is very important in national defense, aviation and aerospace. A novel vision sensor is developed, which can be used for error detecting in arc length control and seam tracking in precise pulse TIG welding of the extending part of the rocket engine jet tube. The vision sensor has many advantages, such as imaging with high quality, compactness and multiple functions. The optics design, mechanism design and circuit design of the vision sensor have been described in detail. Utilizing the mirror imaging of Tungsten electrode in the weld pool, a novel method is proposed to detect the arc length and seam tracking error of Tungsten electrode to the center line of joint seam from a single weld image. A calculating model of the method is proposed according to the relation of the Tungsten electrode, weld pool, the mirror of Tungsten electrode in weld pool and joint seam. The new methodologies are given to detect the arc length and seam tracking error. Through analyzing the results of the experiments, a system error modifying method based on a linear function is developed to improve the detecting precise of arc length and seam tracking error. Experimental results show that the final precision of the system reaches 0.1 mm in detecting the arc length and the seam tracking error of Tungsten electrode to the center line of joint seam.

In recent years, Al_xGa_1-xN semiconductor alloys, with a direct bandgap tunable between 3.4eV and 6.2eV, become the most suitable materials for the fabrication of UV detectors. In this paper we describe the fabrication and characteristics of an UV 64×1 focal plane array (FPA) based on front illuminated GaN p-i-n photodiodes. The diode structure consists of a base n-type layer of GaN followed by unintentionally doped and p-type layers deposited by metal organic chemical vapor deposition on GaN buffered sapphire substrate. Standard photolithographic, Ar⁺ ion beam etching, SiO₂ passivation and metallization procedures were employed to fabricate the devices. I-V, responsivity and spectral response were tested. The linear photodiode array was indirectly hybridized to a silicon readout integrated circuit (ROIC) chip. The ROIC chip consists of capacitor feedback transimpedance amplifier (CTIA) input circuits, correlated double sampling (CDS) circuits, shift registers etc. The 64×1 UV linear FPA was packaged into a 28-pin chip carrier. The response ununiformity is 1.86%. The mean detectivity is about 2.0×10⁹cmHz^1/2W^-1.

An auto-focusing and auto-alignment system based on digital image processing and the computer control technology was developed for 3-LCD projector manufacture. We analyzed the imaging characteristic of the optical system, and developed a mathematical model to realize the accurate focusing of each LCD panel and accurate alignment among three LCD panels. Based on the model, the experimental facility was set up, which is compose of five CCD detectors that are placed on the screen at different filed of view to capture images and regulating mechanism of LCD’s six-dimensional degree of freedom droved by stepper motors. Appropriate defocusing evaluation function and alignment algorithm were also presented in this paper. The images captured by CCDs are processed to get the defocusing amount of every panel by the variance function and displacement amount of the three LCD panels by the gravity model approach. Then commands are sent to regulating mechanism to control the movement of each panel. After several turns of auto-correction, all the panels are in the proper position. Experiment results show that with the proper algorithm, the system can provide high accuracy and good performance in projector manufacture. The whole focusing and alignment process can be finished within ten minutes which is far superior to that made by man more than half an hour. With this system, completely automatic product lines can be established, which can provide 3-panel LCD projector light engines with considerable focusing and alignment accuracy.

A non-contact vehicle wheel alignment parameters measurement system based on line-structured laser sensors is described. The spatial position of vehicle wheel is determined by the tangent plane of the vehicle wheel tire. Three line-structured sensors conduct each wheel, and the tangent plane is calculated by 3D coordinate of each point on three characteristic curves of the tire. Consequently it is important to ascertain the tangent plane of the tire precisely for this system. This paper details the working principle of the system and coordinates unification technique of multiple line-structured laser sensors. Furthermore it presents a specific method for determining the tangent plane according to the characteristic of the laser image. It is composed of ellipse fitting in 2D space and searching algorithm in 3D space. Experimental results show that the algorithm is reasonably efficient, practical and reliable. And the deviations of alignment parameters are less than 2'.

High precision, repeatability, and quality are the three vital requirements in laser welding production. For accurate real-time tracking and inspecting the laser welding process, the high-performance sensors are extremely demanded. Monitored signal reliability can be significantly increased by using high resolution, digital CMOS sensors and high-speed, real-time image processing technologies. This feature presents the latest developments in high-performance optical joint tracking systems and optical inspection systems based on these technologies. Using a coaxially aligned CMOS imaging detector, the optical signals emission of the plasma during CO2 laser welding was studied. The camera images taken from the process were analyzed with image-processing algorithms. Compared with the lateral systems, coaxial arrangement of the camera allows observing the significant process characteristics. Experimental evidence shows that the system can monitor the instability of the keyhole, the gap caused by the welding distortion, and the deviations from the desired welding path. By the image analysis, the spatially distribution intensity of the plasma emission was analyzed, and it can be correlated to the penetration state and the penetration depth. Thus the laser welding process and the weld quality can be evaluated.

The cascaded forward stimulated Brillouin scattering (SBS) in the S band distributed G652 fiber Raman amplifier forward pumped and backward pumped by the tunable power fiber laser and signal source is a tunable narrow spectral bandwidth(<100MHz)ECL have been studied. Forward SBS does not obey the common theory, that only weaken backward-SBS lines existed, according to conservation of energy and momentum and wave vector selected rule. Because the wave-guide character weaken the wave vector rule. The forward transmit sound wave-guide Brillouin scattering lines are generated and amplified in FRA. Forward SBS that is amplified phenomena of transmit sound wave Brillouin scattering in the FRA, during pump power is larger than the threshold value of SBS in a S band G652 FRA. The 2 orders Stokes forward Brillouin lines are present during forward pump power of FRA is 920mW, the pump power of BP line is 7.7dBm and the FRA gain is 15.05dB, the power of first order Brillouin lines is smaller than the second Brillouin scattering line. When pump power is further increased, cascaded SBS lines and comb profile are observed. The even order SBS lines is stronger than odd order SBS lines, The odd order SBS lines are named Brillouin- Rayleigh scattering lines.

Two kinds of displacement sensors are described in which sinusoidal phase-modulating interferometers with optical fibers are utilized. Light reflected at an end face of the fiber is used as reference light in an interferometer of Fizeau type. A sensor is constructed with a laser diode interferometer in which the sinusoidal phase-modulation (SPM) of 1.5MHz-frequency is produced by modulating the injection current of the laser diode. The measurement time of the phase of the interference signal is 0.25μs and a displacement of an object is measured with an error less than 20nm. Another sensor is constructed with a superluminescent diode interferometer in which the SPM is produced by vibrating an output end of the optical fiber in the first interferometer of Fizeau type. A large displacement is measured by finding positions of a mirror in the second interferometer of Michelson type where the optical path difference is zero before and after the displacement. The sensor measures a distance in the range of 10mm with an error less than 20 nm.

Based on the radiation transmission theory, a model of backscattering light and signal light for atmospheric range-gated imaging system has been developed. This model gives time dependent irradiance of backscattering light and signal light on photocathode during the propagation of illuminating pulsed laser in atmosphere. The model could be used to predict and optimize parameters of range-gated imaging systems. Examples with typical system parameters under fog conditions are computed with this model. The results can lead to several conclusions. The first one is that the photocathode irradiance of object image could be higher than that of the background even if optical signal power is lower than optical backscattering power. The second one is that increase in peak power of illumination laser could not improve the image contrast between an object and its background. The last one is that image contrast could be improved by reducing laser pulse width while keeping average laser power unvaried, reducing sensors’ field-of-view, or increasing the separation between transmitter and receiver.

A novel digital speckle pattern interferometry system including multi lower power He-Ne lasers to measure large object is presented in this paper. Multi lower power He-Ne lasers and optical switches are set in it. Through the control of computer, the different laser can illuminate the different area of large object at different time. Then the phase maps corresponding to different area are jointed together to obtain the measurement result of entire object by using proper image mosaic algorithm. Using this method, the contradiction between laser power and size of object to be measured is overcome. In this system, the high coherence of He-Ne laser and the power of multi lasers are comprehensively used, which makes it be able to measure the large object in practical engineering. At the same time, the speckle pattern fringes with high quality can be obtained.

A novel displacement sensor based on diode-end-pumped solid-state laser technology has been investigated theoretically and experimentally. The investigation results indicate that provided the average radius of the pump beam in the gain medium is much smaller than the radius of the waist of the TEMoo laser beam, the exponential of the laser output power will change in a manner of a Gaussian function when the waist of the pump beam is displaced axially. Both the measurement range and the sensitivity of the displacement sensor depend on the pump power, the measurement range will be enlarged and the sensitivity be enhanced when the pump power is increased. For the experimental system of the diode-end-pumped 1064-nm Nd:YAG laser sensor, the measurement range and the sensitivity are 13.045-mm and 0.148-mW/μm, respectively, when the input optical power is 7.24-Watt (corresponding to a maximum output power of 1.926-Watt). Several main error sources that affect measurement accuracy of the displacement sensor have also been analyzed.

This paper describes a technique that inspects the dust emission volume by scattering-light energy characteristic of the dust particles. The scattering-light energy characteristic information, including total energy, peek value energy and the positions of peek value energy, are extracted from the scattering light received by a two-dimension cuneal image sensor. A common inspecting principle of dust emission volume and the two-dimension cuneal image sensor that realizes the measurement of scattering-light energy are discussed. According to the characteristic that the real part of refractive index influences less on the normalized distribution of scattering light the angle smaller than 30°, the center of a two-dimension cuneal image sensor is placed at the optical axis of focal plane of Fourier lens and is capable of receiving scattering light energy within forward angle 2.8°. Experiments were made with a simulating dust emitting experimental instrument and obtained scattering light energy characteristic information for dust emission volume 50mg, 100mg, 150mg, 200mg, 300mg, 400mg, 500mg and 600mg. We point out that dust emission volume can be inspected by scattering-light energy characteristic, and suggest that it is necessary to establish a database that shows the relationship between dust emission volume and scattering-light energy and to measure the size distribution of dust particles.

Photonic crystal fibers (PCFs) have special wave-guiding properties that cannot be achieved in conventional optical fibers. The properties of PCFs can be controlled via the geometry of their microstructured cladding. This opens up new opportunities for numerous applications in the areas of light transmission, nonlinear optics, fiber-optic components and sensors. In this paper, we overview the applications of PCF in photonic sensing.

This article has put forward a new optical fiber strain sensor, based on the spiral bending loss of single mode fiber. It uses the theory of backward Rayleigh scatter and anlong with OTDR composes of distributed fiber optic sensing system so as to realize the measurement at a certain precision. The paper has also proceeded the theory analysis and experimental investigation on the optical fiber sensing system, and has proved its good sensing characteristics.

The temperature-dependent characteristics of fluorescence of transient-metal doped and/or rare-earth-doped YAG has made these materials the focus of fluorescence thermometer. This article reports growth and fluorescence characteristics of Cr³⁺: YAG crystal fiber used for thermometer based on fluorescence decay time. Using a long pure YAG crystal fiber as the seed and a 0.1 at. % Cr₂O_3-doped Y₃Al₅O₁₂ sintered powder rod as the source rod, a YAG fiber thermal probe with Cr³⁺-ions doped end was grown by laser heated pedestal growth method. The crystal fiber shows good optical properties and mechanical strength and offers advantages of compact construct, high performance and ability to withstand high temperature. The fluorescence decay characteristics of the crystal fiber, including the temperature dependence of both fluorescence decay time and intensity, were comprehensively investigated. The experimental results indicated the Cr³⁺:YAG crystal fiber showed a monotonic relationship between the fluorescence lifetime and temperature over a wide temperature range from cryogenic to high temperature(>500°C). The fiber was found to be an excellent candidate material to be used as a fiber thermometer based on fluorescence lifetime. This thermometer may be used as temperature monitor in microwave treatment and Medium Voltage substations.

For very high data rates, intersatellite optical communications hold a potential performance edge over microwave communications. Acquisition and Tracking problem is critical because of the narrow transmit beam. A single array detector in some systems performs both spatial acquisition and tracking functions to detect pointing errors, so both wide field of view and high update rate is required. The past systems tend to employ CCD-based camera with complex readout arrangements, but the additional complexity reduces the applicability of the array based tracking concept. With the development of CMOS array, CMOS-based cameras can employ the single array detector concept. The area of interest feature of the CMOS-based camera allows a PAT system to specify portion of the array. The maximum allowed frame rate increases as the size of the area of interest decreases under certain conditions. A commercially available CMOS camera with 105 fps @ 640×480 is employed in our PAT simulation system, in which only part pixels are used in fact. Beams angle varying in the field of view can be detected after getting across a Cassegrain telescope and an optical focus system. Spot pixel values (8 bits per pixel) reading out from CMOS are transmitted to a DSP subsystem via IEEE 1394 bus, and pointing errors can be computed by the centroid equation. It was shown in test that: (1) 500 fps @ 100×100 is available in acquisition when the field of view is 1mrad; (2)3k fps @ 10×10 is available in tracking when the field of view is 0.1mrad.

Rare-earth-element-doped fibers are wildly used in fiber amplifiers, fiber lasers and fiber sensors. Fiber Bragg Gratings (FBGs) are very important optical components in optical communication and sensing. Combining these two types of fiber products can give us a new type of fiber components, which is called fluorescence fiber grating here. The fluorescence fiber grating consists of fiber amplifiers and fiber gratings. It has serials of special characters. The method to fabricate the fluorescence fiber grating is writing the grating configuration to a rare-earth-elements-doped fiber. Normally, these fibers need pretreatment, for example, loading hydrogen. Differing to a fiber laser, the fluorescence fiber grating has a whole-length grating configuration along the rare-earth-elements-doped fiber. The emission of the fluorescence signal will occur along the whole components. There are no a clear fluorescence light source and clear reflection areas. When the pump light goes through the fluorescence fiber grating, the fluorescence light emits as incoherent signal. The intensity of the output light from the ends of the grating is the sum of the light intensity from the all parts of the fluorescence fiber grating. The coupling mode theory is used to explain the character of the fluorescence fiber gratings. The fluorescence light emitting from a part of the fluorescence fiber grating will be reflected by double sides of the grating. Then the sum of light intensity from the every part will give the spectrum of the output light. The shape of the spectrum of the output light depends on both the length and the modulation depth of the grating.

Micro drop fiber sensors are effective tools for measuring characters of liquids. These types of sensors are wildly used in biotechnology, beverage and food markets. For a fiber micro drop sensor, the signal of the output light is wavy with two peaks, normally. Carefully analyzing the wavy process can identify the liquid components. Understanding the reason of forming this wavy signal is important to design a suitable sensing head and to choose a suitable signal-processing method. The dripping process of a type of liquids is relative to the characters of the liquid and the shape of the sensing head. The quasi-Gauss model of the light field from the input-fiber end is used to analyse the distribution of the light field in the liquid drop. In addition, considering the characters of the liquid to be measured, the dripping process of the optical signal from the output-fiber end can be expected. The reflection surface of the micro drop varies as serials of spheres with different radiuses and global centers. The intensity of the reflection light changes with the shape of the surface. The varying process of the intensity relates to the tense, refractive index, transmission et al. To support the analyse above, an experimental system is established. In the system, LED is chosen as the light source and the PIN transform the light signal to the electrical signal, which is collected by a data acquisition card. An on-line testing system is made to check the theory discussed above.

Metallic nanostructures can have strong effects on the polarization state of light and present significant polarization sensitivity. However, quite often these phenomena have only negligible effects thus passing our attention without careful analysis. We show that these effects can be enhanced by using resonance effects arising from waveguide modes propagating along the surface. This enables the use of metallic nanostructures as artificial media components modulating the polarization state of light.

A lower-cost monochrome CCD camera, which can detect the twenty-five frames of picture in one second, provides a rapid method to measure two-dimensional luminance distributions of the screen. According to the two-dimensional luminance distribution ratios of three primary colors captured by the CCD camera and the chromaticity coordinates of R, G, and B calibrated by the spectrometer, the chromaticity coordinates of combination colors of the LCD projector can be computed quickly. The algorithm of removing the black stimulus values and the precise calibration in five gray levels of CCD are employed to diminish the error. The two-dimensional distribution maps of chromaticity coordinates of combination colors of five levels are represented in this paper. The data show that the maximum difference between the chromaticity coordinate measured by CCD-based system and by the spectrometer is 0.009, which can present the color uniformity of LCD projector properly.

This paper proposes an APS based Autonomous Star Tracker (AAST). The image sensor used in the star tracker is CMOS Active Pixel Sensor (APS). APS has many advantages to construct small, light weight, power saving and inexpensive star tracker for microsatellite application where power consumption and mass are critical. With the special design of optics, electronics and software, the proposed AAST can performance image sensing and process, star identification and attitude estimation all by itself and can output attitude data directly. The design concept of lower sensitivity with wider field of view enables the star tracker to perform whole sky independent star pattern recognition in the lost-in-space circumstance. These autonomous and independent features provide great convenience for the proposed star tracker to be applied in the future space mission. The total mass and power consumption of the AAST prototype are less than 1000g and 5W. The estimated accuracy is about 5" in the cross boresight direction and about 30" in the boresight direction.

EFPI(extrinsic Fabry-Perot interferometer) and FBG(fiber Bragg grating) sensors are two kinds of the most promising sensors for structure health monitoring and can resolve the problem of cross sensitivity of sensing well when they are used simultaneously for strain and temperature measurement. A parallel demodulation method for the two types of sensors is developed for the goal, which based on a set of Michelson interferometer and combined the methods of low coherence interference and Fourier transform spectrum. The signals from EFPI and FBG sensors are obtained at the same time by scanning one arm of Michelson interferometer, and an algorithm model is established to retrieve the information of wavelength of FBG and cavity length of EFPI, which then be used to determine the information of strain and temperature. The experiment shows the demodulation precision of FBG is 14.4 pm and that of EFPI is 0.203μm.

The temporal actions of free photoelectrons and shallow trapped photoelectrons in the AgBrI-T grain emulsion were obtained with the microwave absorption and dielectric spectrum technique at the same time. The results indicate that the electron trap effect of sensitization center changes from shallow to deep with the increase of sensitization time. When the function of chemical sensitization center is shallow electron trap effect, the decay of electron is slower and the decay time and lifetime of the photoelectron in sensitized sample are longer than that in unsensitized sample because the sensitization center holds back the recombination between the electron and the hole. When the function of chemical sensitization center is deep electron trap effect, the decay of electron is quicker and the decay time and lifetime of the photoelectron in sensitized sample are shorter than that in unsensitized sample because the sensitization center deeply traps the electrons. The optimal sensitization time is gained according to the relationship between decay time of photoelectron and sensitization time.

Photorefractive properties of Fe, Mn, and Rh doped 0.91Pb(Zn_1/3Nb_2/3)O₃-0.09PbTiO₃ (0.91PZN-0.09PT) are investigated. Relaxor ferroelectric crystals are expected to show large photorefractive effect due to its large piezoelectric effect near morphotropic phase boundary (MPB). Crystals are grown by flux solution method, then cut, polished, and poled along [110] direction. Absorption spectrum, photorefractive two-beam coupling gain, and response speed were measured as functions of the grating period, and light intensity, at several wavelengths for each doped and undoped samples. Photoconductivity and photochromism in Fe doped crystal were estimated. Fe doping enhanced the photorefractive effect and net two-beam coupling gain of 19 cm^-1was obtained. Rh doping increased the gain at 633 nm compared to the undoped sample. From the intensity dependence of the two-beam coupling gain, two-center model is suitable for explaining the photorefractive properties of Fe doped samples. For all samples, doping of the ions slowed down the response speed because of the decrease of the photoconductivity.

The phase-demodulation scheme by using a discrete Hilbert transform that can change the interferometric phase by π/2 has been investigated. In-quadrature components of a fringe pattern are obtained from one captured interferogram by using a one-dimensional (1-D) discrete Hilbert transform and a 1-D discrete high-pass filtering that are based on a digital signal processing technique. The 1-D discrete Hilbert transform can be extended to two-dimensional calculation with a raster scanning procedure.

Position measurement in 2D plane plays an important role in many fields such as production controlling, automatic aiming , multimedia, and so on. The application of planar array CCD in 2D position measurement is facile. But it is difficult if both cost and precision to be taken into account. This paper proposed a method realizing 2D position measurement using linear array CCD to solve this problem. A special optical system is designed, including a main lens, an inverting prism, and a combination of a spherical lens and a cylindrical lens, by which the spots equidistant from the basic shaft(eg. x shaft) can be imaged into the same line. With a linear array CCD normal to the axis of the cylinder, the distance from the line to the basic shaft is measured, through which one value of the coordinate(eg. y) can be computed according to the object-to-image conjugate relationship. An inverting prism, eg. DOVE prism, rotating at a palstance of ω followed by the image at 2ω,makes it possible to measure each value of 2D coordinate when the DOVE is in the initial point or turns to 45°(image turns to 90°). A possible application is also given.

The nanostuctured YSZ (Yttria Stabilized Zirconia) membranes on Si(110) substrates are successfully prepared by sol-gel technology derived from inorganic salts ZrOCl₂•8H₂O, H₂C₂O₄•2H₂O and Y(NO₃)₃•6H₂O. By means of controlling the supersaturation and diffusion velocity in solution when the zirconyl oxalate xerogels are repeptized, spherical colloidal paricles with different distributions are obtained. we propose that the peptization of xerogels can be considered as a process of nucleation and growth of colloidal particles. The membranes are preparated by spinning the modified sols on Si(110) substrates. After calcining at 800°C for 1 hour, the membranes are crack-free and mirrorlike. The membranes consist of monodisperse fine spherical crystallines in the range of 20~220nm in diameter, which microstructures are controlled by changing the size and distribution of colloidal particles in sols.

A smart temperature sensor is performed based on the high birefringence (HB) fiber loop mirror. The sensing can be achieved by simply detecting the light intensity, utilizing a single mode laser diode (LD) as the source. In the range of 25°C-35°C, the resolution and linear regression are 0.05°C and 0.9986, respectively. The sensor can be employed to precise temperature measurement and the range can expand further when selecting shorter HB fiber in the loop mirror.

A high-sensitivity fiber Bragg grating (FBG) pressure sensor has been designed and studied. Confining some gas inside a glass cylinder with a close glass piston which can move smoothly along the cylinder, and sticking two ends of a fiber Bragg grating on the outer side of the cylinder and piston respectively. The variation of the external pressure results in the change of the tension that the fiber grating is subjected to and then the pressure can be measured by the measurement of the Bragg wavelength of the FBG. The pressure sensitivity coefficient is up to -0.7676/MPa, which is about 3.88×10⁵ times the value of bare fiber Bragg gratings, the highest sensitivity ever reported. The sensor can be used to potential applications in the measurement of air pressure, hydraulic pressure and vibration in the range of low pressure.

In this study, tin precursor layers were deposited on ITO glass substrates by thermal evaporation, and sulphurised in a vacuum furnace at the temperature range between 423-673K, in order to translate the tin layers into compound SnS layers. All the layers synthesized were characterized with X-ray diffractograms, microstructure analysis. It was found that the best SnS films were synthesized for sulphurisation at temperature 573-673K, and they were polycrystalline with a strong {111} preferred orientation, and they had orthorhombic crystal structure with a grain size of a few hundred nanometers and exhibited near stoichiometric SnS composition. The near stoichiometric SnS film was measured to have a p-type electrical conductivity and a resistivity of the order of 10² Ω.cm , and its optical properties were investigated using spectrophotometric measurements of the transmittance and reflectance at normal incidence in the wavelength range 400-2500nm, the films were transparent for a wavelength >1250nm.

In this paper, SnS films were cathodically electrodeposited on ITO glass substrates from aqueous solution containing 5mM SnSO4 and 25mM Na2S2O3 with pH of 2-3. When the deposition potential (E) was varied from -0.60 to -1.1V vs SCE, the corresponding SnS films were characterized with X-ray diffractograms, microstructure and composition analysis. It was found that, the composition ratio Sn/S of the film varied with E, the ratio Sn/S significantly increased and exceeded 1 at E more cathodic than -0.75V vs SCE, and the ratio Sn/S significantly decreased and was less than 1 at E larger than -0.7V vs SCE. The stoichiometric SnS film was synthesized at -0.72~-0.75V vs SCE . The structural and optical properties of the film have been studied. The X-ray diffraction pattern of the film showed that it was polycrystalline and of orthorhombic structure. The estimated optical bandgap energy was 1.31eV.

The light deflector is one of the key components in laser scanning and imaging system, such as rotating holographic gratings, galvanometric mirrors, acoustooptical scanners and rotating polygonal scanners, etc. Of these scanning elements the most commonly used scanner is rotating polygonal scanner. This paper will first briefly discuss the operating principle of rotating polygon and two different polygon scanning configurations: a post-objective scanning scheme and a so-called pre-objective scanning scheme using flat-field scan lens (f-theta scan lens). The emphases will be put on the analysis of the relationship between scanning error and some important error factors of polygon used in the pre-objective scanning scheme. A set of formulae are developed to calculate the tolerance of polygonal reflecting surface, divided angle, the degree of malalignment between reflect surface and the axis of rotation and rotating speed error etc. It provides a reliable foundation for the constitution of the tolerance polygon and rotating speed.

In this paper the photoelectric characteristics of three-channel bulk charge-coupled device (BCCD) are simulated in the region of near-IR. The results show that the germanium three-channel BCCD cannot realize multispectral imaging in the region of near-IR because of germanium’s absorption coefficient. Basing on the result of theoretical research the absorption coefficient curve of a new substrate material has been found, which can realize multispectral imaging in the region of near-IR. The simulating results show that the spectral photosensitivity of three-channel BCCD made by the new material have three maximal positions at 1.0μm,1.1μm and 1.26μm respectively.

A new method for position error correction of position-sensitive detector (PSD) using least squares support vector machine (LS-SVM) is presented. The LS-SVM is established based on the structural risk minimization principle rather than minimize the empirical error commonly implemented in the neural networks, LS-SVM achieves higher generalization performance than the MLP and RBF neural networks in solving these machine learning problems. Another key property is that unlike MLP’ training that requires non-linear optimization with the danger of getting stuck into local minima, training LS-SVM is equivalent to solving a set of linear equations. Consequently, the solution of LS-SVM is always unique and globally optimal. A difference with the RBF neural networks is that no center parameter vectors of the Gaussians have to be specified and no number of hidden units has to be defined because of Mercer's condition. The position error correction procedure has been illustrated using 2D PSD as example. The results indicate that this approach is effective, and the position detection errors can be reduced from ±300μm to ±10μm.

Reverse engineering of free-form surfaces is one of the most challenging technologies in advanced manufacturing. With the development of industry more and more sculptured surfaces, such as molds and turbine blades, are required to measure quickly and accurately. Optical non-contact probes possess many advantages, such as high speed, no measuring force, in comparison with contact ones. The ability of stereo vision probe with CCD cameras in gathering a large amount of information simultaneously makes it the most popularly used one in sculptured surface measurements. So a non-contact measurement system is built which consists of CMM and a vision probe with many techniques. It distinguishes itself by high efficiency, high accuracy and reliability, as well as applicability for on-line measurement of complicated sculptured surfaces. With a virtual 3D target in form of a grid plate, all the intrinsic and extrinsic parameters of CCD camera including the uncertainty of image scale factor and optical center of camera can be readily calibrated. Through measuring cylindrical section and surface of gauge block, this system is viable to measure free-form surface and high-reflective metallic surface.

In this paper, firstly the spectral response of transmission-type GaAs photocathode is measured online by the spectral response-testing instrument. Then the cathode is sealed in the third generation intensifier and put into the instrument again to get another spectral response curve. The variation of spectral response curves was compared. The results show that through the seal process, the spectral response in the long wavelength decrease. Based on these curves, the spectral matching factors of GaAs photocathode for green vegetation and rough concrete are calculated. The calculated performance parameters show that the variation of the spectral response in the seal process is an important influence factor on the performance of the intensifier in the use of night vision.

Water content measurement technologies are very important for quality inspection of food, medicine products, chemical products and many other industry fields. In recent years, requests for accurate low-water-content measurement in liquid are more and more exigent, and great interests have been shown from the research and experimental work. With the development and advancement of modern production and control technologies, more accurate water content technology is needed. In this paper, a novel experimental setup based on near-infrared (NIR) spectral technology and fiber-optic sensor (OFS) is presented. It has a good measurement accuracy about ∓ 0.01%, which is better, to our knowledge, than most other methods published until now. It has a high measurement resolution of 0.001% in the measurement range from zero to 0.05% for water-in-alcohol measurement, and the water-in-oil measurement is carried out as well. In addition, the advantages of this method also include pollution-free to the measured liquid, fast measurement and so on.

BP Neural Network Method and Linear Partition Method are proposed to search the mapping relationship between space points and their image points in CCD cameras, which can be adopted to calibrate three-dimensional digitization systems based on optical method. Both of the methods only need the coordinates of calibration points and their corresponding image points’ coordinates as parameters. The principle of the calibration techniques includes the formula and solution procedure is deduced in detail. Calibration experiment results indicate that the use of Linear Partition Method to coplanar points enables its measuring mean relative error to reach 0.44 percent and the use of BP Neural Network Method to non-coplanar points enables its testing accuracy to reach 0.5-0.6 pixels.

Dissolved Gas-in-oil Analysis is one of the most effective methods to diagnose the potential inner faults of power transformers. To overcome the disadvantages of the current sensing methods including gas chromatographic and Fourier Transform InfraRed techniques, photoacoustic spectroscopy has been introduced for both online and offline monitoring of transformer fault gases. Pulsed infrared sources are recommended and the wavelengths for each diagnostic gas are suggested. For hydrogen has no absorption in Infrared band, in no way can it be detected by infrared spectroscopy. Therefore, a novel technique is introduced to detect hydrogen via the phase shift of photoacoustic signals. The detailed sensing principle gives that the relative time shift of the photoacoustic signals by the adding of each fault gas is proportional to the added concentration of the very gas. By subtracting the effect of all the other fault gases, the added concentration of hydrogen can be calculated. Analyses show that the error of this method may be smaller than that of measuring other fault gases; the lowest sensible limits from 5ppm to 60ppm may require the time resolution of the system to be within the range of 10^-6~10^-9 and they are tested to be reachable by simulations on LabVIEW.

A self-mixing laser Doppler velocimeter is designed based on dual frequency laser. We can receive two beat signals and analyze them in frequency domain. The value of Doppler frequency shift is half of the distance between the two components in the power spectrum while the sign of Doppler frequency shift can be easily determined by the relative position of the two components in the power spectrum.

A high accuracy and flexible method for calibrating intrinsic parameters of CCD camera is presented. The intrinsic parameters of camera is determined from collinear constraint and computed through bundle adjustment algorithm. Calibration is carried out by moving an optical feature point with CMM and forming a virtual stereo calibration board. The images of this virtual board are taken by the calibrated camera which in different locations and orientations. Due to take infrared LED as feature point and the light intensity of these feature points can be automatically controlled according to the distance between camera and feature point, the imaging feature points have uniform intensity profile and high contrast with background, and hence the calibration accuracy is improved. This method has been used for calibrating the Kodak MegaPlus 1.4i CCD cameras, which used in large-scale stereo vision coordinate online measurement system, and obtained higher measurement precision.

In the interference phase measurement of slow-changing process, by use of the phase-shifting technology in the initial state, the background and amplitude of interference fringes can be obtained, and a novel phase unwrapping method based on cosine function is proposed. The holograms of the changing process are recorded, and then the phase cosine functions can be obtained by removing the background and amplitude from the holograms. The arccosine functions of phase cosine functions, which are called phase cosine wrapping function in this paper, can be unwrapped by utilizing the additional normal orientation information. The experimental analyses show that the residual noise and the phase-shifting errors have great influence on the accuracy of unwrapped phase. The tangent wrapping phase can’t be filtered by traditional method due to the π phase jumps, and the existing phase unwrapping algorithms are very complex. The phase-shifting errors can only influence the positions of phase jump points in the tangent wrapping phase. It is difficulty to optimize the tangent wrapping phase further. Compared with tangent wrapping phase, the phase cosine wrapping function is consecutive and can be filtered, and the unwrapping process is easier than that of tangent wrapping phase. The influence of phase-shifting errors on phase cosine function is not only positions but values of the wave crest and wave trough. The more precise the phase-shifting is, the closer the values of cosine function to ±1 at wave crest and wave trough are. The Experiment results show that cosine unwrapping method has the equivalent precision with tangent unwrapping method.

The drop profile is one of the evident differences for different liquids. An image drop sensor is developed for capturing the drop profile images real-timely in various stages during the drop growth. The drop head for forming the uniform and satiated liquid drop is designed. The original profile records of pure water and 100% ethanol during their drop growth will be presented. Edge extraction methods on drop profile are discussed. Curve fitting based on third-order polynomial linear regression is used to mathematically describe the detected edge curves of the drop profile in sequential drop formation.

The contact resistivity of Ni/Au contact on p-type GaN was drastically decreased through the surface treatments in sequence using alcohol-based HCl and KOH solution. The surface oxide on p-type GaN formed during epitaxial growth was removed in the alcohol-based HCl and KOH solution, The O 1s and C 1s core-level peaks in the x-ray photoemission spectra showed that the alcohol-based HCl treatment was more effective in removing of the surface oxide layer. Compared to the KOH solution treated sample, the alcohol-based HCl-treated sample showed a Ga 2p core-level peak which was shifted toward the valence-band edge by 0.3 eV, indicating that the surface Fermi level was shifted toward the valence-band edge. These results suggest that the surface barrier height for hole injection from Ni/Au metal to p-type GaN be lowered by the surface treatment, which results in a drastic reduction in specific contact resistance.

The online measurement of wheel set wear parameters is important for ensuring the safety of train vehicle and increasing the reliability and efficiency of maintaining. The paper researched an automatic measuring method of wheel set parameters based on CCD and image processing. The method used precision laser displacement sensor, CCD, digital image processing and motion control technology to realize the non-contact automatic measuring of wheel set parameters. These parameters include the flange thickness, flange height, wheel diameter, rim inside distance, rim inside thickness, rim width, scotching and flaking on wheel tread. The tread and flange profile were captured using laser source and high resolution CCD sensor. The image SNR was gained through narrow band-pass optical filters which wavelength matched with laser source. In order to detect the irregular tread failures formed in running of train vehicle, the paper used precision laser displacement sensor to scan the tread and acquire the position while the wheel set was rotating. The displacement data of different positions were transformed to digital image. Then digital image processing was used to distinguish and judge the failures. The measuring accuracy of geometrical parameters, scotching depth and flaking length were 0.2mm, 0.1mm and 0.5mm respectively. The repeatability and accuracy can meet the demand of non-contact online wheel set maintaining.

There are two kinds of auto-focus methods in a digital imaging system: Depth from focus (DFF) and Depth from defocus (DFD). Depth from defocus is a method, which acquired distance information from blurred image. Because of necessity of establishment of defocus model and accurate calibration of imaging system, the application of DFD is confined. As a search focusing technology, Depth from focus has some advantages, such as high accuracy, robust performance, so it is adopted in our apparatus. In this paper, an auto-focus apparatus based on digital signal processor has been designed and constructed. DSP receives image series from a CMOS sensor firstly, then performs the auto-focus action with the following steps: analyzing focus measure of image, moving motorized lens and finding the best imaging position. For focus measures, the frequency spectrum functions, the gradient functions and the entropy function are analyzed in detail. In order to improve the sensitivity of focus measure curve, the weighting factor - distance between direct current component and alternating current component - was introduced into revising frequency spectrum functions. A series of focus experiments have been performed on the auto-focus apparatus, and the veracity and the reliability of the system have been proved to be excellent.

In this paper, an interferometric autocorrelator based on two-photon-absorption (TPA) detector is demonstrated. It can be used in the measurement of ultrashort pulse at 1.55 um wavelength region. From the second order autocorrelation trace of optical field, we can infer the pulse width. Accompanied with a linear detector, we can fully characterize the optical pulse, including intensity and phase profiles. A novel phase retrieval algorithm is proposed. It is a combination of an iterative loop and an evolution process. Simulation results show that our algorithm converges stably and can give a better approximation of the optical field than traditional algorithm.

High-quality Sulfur doped n-type diamond thin films have been successfully synthesized via glow plasma assisted hot filament chemical vapor deposition using gas mixtures of methane, hydrogen, Argon and hydrogen sulfide. Impacts of the volume ratio of hydrogen sulfide to methane R_S/Con the structural and physical properties of the films have been systematic ally studied using various techniques such as Hall effect measurement, x-ray diffraction (XRD) and atom force microscope. We found that the carrier mobility is 474 cm²V^-1S^-1 and the electrical conductivity is 1.45Ω^-1·cm^-1at R_S/C=6800ppm. The sheet resistivities of the films increase with increase of R_S/C, reach the maximum at RS/C of 6200ppm, and then begin to decrease. Also, with increase of R_S/C, a linear increase in the conductivities of the films is found, which is believed that higher R_S/Cis favorable for the increase of electrical conductivity of sulfur doped diamond thin films.

Monte Carlo simulations are adopted to study the space distribution of the particles in the mixture of CH₄/H₂/H₂S/Ar considering the avalanche collision and dissociative ionization of electrons based on the theory of glow discharge in electron-assisted chemical vapor deposition (EACVD) system. The relationship between the space distribution and the recombination rate of H and CH₃, CH₃₊ fragment particles is given. The dynamic process of the n-type doped diamond film is simulated under different gas pressure. The particle distributions of S, S⁺ and Ar⁺ are also obtained. The result is very important for investigation of n-type diamond film doping at low temperature.

Theoretical foundation and principle programmer will be studied in this paper that special photosensitive Si-PSD (Si-Position Sensitive Detector) is rebuilt into electron bombardment mode device, which is based on minimal weak light detecting technical demands and exciting principle of high-energy electronic beam acting on silicon semiconductor. At the same time we will bring forward new concept device of electron bombardment mode PSD. According to the theoretical foundation and principle programmer, we present the practical measurement result that semiconductor gain of electron bombardment mode device is obtained. When incident electron energy is more than 4KeV, then obtained more than 10³ gain. We have produced high-sensitivity photon-counting imaging detector (MCP-PSD tube) with 10⁸~10⁹ gain, which combined the research of microchannel plate (MCP) cascade applications with electron bombardment mode device. This paper also will present the substantial photograph of electron bombardment mode PSD device and MCP-PSD tube. Finally we will bring forward prospect realizing detection of minimal weak light photon-counting imaging.

The MCP ion barrier film in low-light-level imaging tube and its process techniques were introduced in this paper. The electron transmittance of this film was studied. The results of half field-of-view testing comparisons and the concept of dead voltage were presented. The dead voltage curve and the relation between dead voltage and thickness of film were tested. The composition of film was analyzed by XPS.

The paper presents the approach of image super-resolution reconstruction based on genetic algorithm. We use genetic algorithm as an optimizing tool, considering the image set as initial population, and thus establish an algorithm based on genetic algorithm aiming at image super-resolution reconstruction. Simulating experiments have been carried out, which proves that the algorithm we put forward can enhance the resolution and quality of the image and the result is satisfactory.

In avigation, navigation and other fields, electrical image stabilization technique (EIS) is applied widely. Recent research for electrical image stabilization is focused on motion vector estimation, which influences accuracy of image stabilization and its applicable scope directly, and pay less attention to the relation between image stabilization algorithm and structure character of image sensor. In fact, while image sensors are interline transfer CCD, 2D rigid motion model is not accurate enough for the image stabilization algorithm. There exist the displacement between the rows in a frame, for the different rows are exposed at different time. In order to compensate the interline displacement caused by the movement of the sensor both in horizontal and vertical direction, an image revision method based on correlation was put forward for the structure character of interline transfer CCD. During exposure of each frame, the motion of camera is along uniform direction and approximately even (otherwise it is beyond application scope of EIS), so it is feasible to revise image according to the displacement at the top and the bottom of image. Image sequence was acquired by telescope with function of optical image stabilization, and then was processed by electrical image stabilization algorithm. Experiment results showed that the image fidelity has been improved remarkably after image revision processing.

The stadia is an important index of low light level imaging system. It indicates the combination detection property of low light level imaging system. In this paper, taking the low light level night vision system, which is composed of objective, image intensifier and eye lens, as the object of study, experiment and analysis on the stadia of low light level imaging system are carried out in detail. First the stadia theory analysis model of low light level night vision system is described. And then all kinds of factors, which influence the stadia of low light level imaging system, are discussed and analyzed. These factors include the observation effect grade and object equivalent optical transform, 3-dimension Dfτequal stadia chart, MTF, equivalent spatial frequency interval, contrast deterioration coefficient, snow-flower noise and noise factor. At last the measures and advices, which are used to improve the stadia of low light level night vision system, are proposed. The research results of this paper have important meaning on the design, evaluating and manufacturing of new low light level night vision system.

Colloidal TiO₂ was prepared by hydrolyzing tetra-n-butyl titauate. Composite multilayer films of Poly(sodium 4-styrensulfonate), PSS, and colloidal TiO₂ particles were electrostatically self-assembled onto optic fibers and microscope glass slides. As the PSS/TiO₂ film was deposited onto the end face of a glass fiber, the reflected optic intensity periodically oscillated as the bilayer number of the film increased. After a 24-bilayer film was coated onto the both sides of a glass slide, the transmittance at 850 nm decreased more than 20%, which means that the film could serve the function as a reflection-enhancing coating. Data of X-ray diffraction and TEM electron diffraction analysis show that the main crystalline phase of the colloidal TiO₂ particles is brookite and that the PSS/TiO₂ films are polycrystalline films. Scratching experiments indicate that the composite films are of relatively high hardness.

Aimed at the influence of turbulent atmosphere effect on laser pulse detection, it discusses the key factors that affect the signal test in this paper. Based on it, the article also discusses two key techniques, namely, floating threshold value and AGC (Automatic Gain Control) technology in detail, especially about the technique of floating threshold value. According to discussion about intelligent detection technology of laser pulse, the system designs a low noise detecting unit of laser pulse, tests its performance by the experiment, and validates correctness of the results.

Aimed at improving the detection ability of the night vision system, a new method to design the optimum spectral band is presented. The new method uses MRC (Minimum Resolvable Contrast) as the criteria of the system performance and brings the spectrum characteristic of the scene and the night vision system into the MRC evaluation. According to the MRC variety of the night vision system under the different working spectral bands, the optimum spectral band is the one which can maximize the scent contrast and doesn't obviously decrease the cut-off spatial frequency of the MRC curve. Finally by the design method and the MRC model, the optimum spectral band of a night vision system example under the special scene is given.

Although many methods, such as bacteria plate count, flow cytometry and impedance method have been broadly used in the dairy industry to quantitate bacteria numbers around the world, none of them is a quick, low cost and easy one. In this study, we proposed to apply the color difference theory in this field to establish a mathematic model to quantitate bacteria number in fresh milk. Preliminary testing results not only indicate that the application of the color difference theory to the new system is practical, but also confirm the theoretical relationship between the numbers of bacteria, incubation time and color difference. The proof of the principal study in this article further suggests that the novel method has the potential to replace the traditional methods to determine bacteria numbers for the food industry.

Ce:Mn:LiNbO3 crystals with different Li/Nb mole ratios in the melts (Li/Nb = 0.94, 1.05, 1.20, 1.38) have been grown for the first time. The growing conditions varied greatly on the Li/Nb ratio. With the increase of Li/Nb ratio in crystals, the Curie temperature raises while the melting point drops. The infrared spectra of crystals were measured. The exponential gain coefficient, response time and diffraction efficiency were measured by two wave coupling experiments with He-Ne laser (632.8nm). The near-stoichiometric Ce:Mn:LiNbO₃ crystal grown from the melt with Li/Nb ratio 1.38 exhibits the largest exponential gain coefficient (33cm^-1) and shortest response time (19s), which is attributed to its larger photoconduction. Combined with spectrum analysis we deduced that the increase of photoconduction may be due to the decrease of anti-site (Nb_Li)⁴⁺in crystals.

A color-encoded technique for 3D measurement is presented in this paper. In this technique, a color pattern that is composed of RGB components is created by software on a computer screen and projected to an object by a digital light processing, which is controlled by the computer. The image of the object is captured by a CCD color digital camera positioned at an angle different from that of the digital projection system. The color of each pixel of the image has a one-to-one correspondence with the projection angle. The 3D depth map of the object is obtained by way of computer decoding and calculating of the color image captured. This paper mainly introduces the errors analysis and the computer simulation method. The results of the example shows that the relatively errors of the 3D measuring system are smaller than 1%. Simulations have been performed and the results validate the method.

A novel confocal endoscopic imaging system is designed for imaging thick sample. The lateral and axial detected image intensity is deduced and calculated based on point spread function (PSF). The analysis of influence of pinhole and fiber on resolution is given. Our researches show that the lateral resolution improvement is much more sensitive to pinhole size than the axial resolution. Confocal system has narrower half width at half maximum (HWHM) and higher lateral and axial resolution for smaller pinhole. At last a criterion for pinhole size is introduced first of all to ensure confocal imaging and maximize signal-to-noise ratio, which is very helpful in the practical design of confocal endoscopic imaging system.

Accurate grading is necessary to ensure the quality of tiles. The quantity of color difference is an important base for grading tiles. For this reason it is necessary to quantify the color differences of tiles. This paper presents a new method of using computer vision technology to measure color differences tiles. It uses CCD image sensors to obtain color images of tiles. The images are then processed with computer to produce the RGB of the color image. The image is then converted from RGB space to CIE1976L*a*b* color space. The character colors are then obtained. The color differences is then determined based on the character colors. A measure system and the color difference computing software were designed. Results from experiments were also given in this paper that color difference values with the different color index are larger than the same color index. The experimental results show that this measuring method can be used for real-time measuring for ceramic tiles.

The gain of a TDI CCD camera is the conversion between the number of electrons recorded by the TDI CCD and the number of digital units (counts) contained in the CCD image[1]. TDI CCD camera has been a main technical approach for meeting the requirements of high-resolution and lightweight of remote sensing equipment. It is useful to know this conversion for evaluating the performance of the TDI CCD camera. In general, a lower gain is better. However, this is only true as long as the total well depth (number of electrons that a pixel can hold) of the pixels can be represented. High gains result in higher digitization noise. System gains are designed to be a compromise between the extremes of high digitization noise and loss of well depth. In this paper, the mathematical theory is given behind the gain calculation on a TDI CCD camera and shows how the mathematics suggests ways to measure the gain accurately according to the Axiom Tech. The gains were computed using the mean-variance method, also known as the method of photon transfer curves. This method uses the effect of quantization on the variance in the measured counts over a uniformly illuminated patch of the detector. This derivation uses the concepts of signal and noise. A linear fit is done of variance vs. mean; the resulting slope is the gain of the TDI CCD. We did the experiments using the Integration Sphere in order to get a flat field effects. We calculated the gain of the four IT-EI-2048 TDI CCD. The results and figures of the four TDI CCD are given.

Many applications, such as industrial inspection and overhead reconnaissance benefit from line scanning architectures where time delay integration (TDI) significantly improves sensitivity[5]. Images with linear response have become the backbone of the imaging industry. But each pixel of the TDI CCD has unique light sensitivity characteristics. Because these characteristics and the lens of the optical system affect camera’s linearization and its performance, they must be removed through calibration. The process by which a CCD image is calibrated is known as nonuniformity correction. This paper discusses several methods of nonuniformity correction[2]. The first is one-point correction technique, which requires only one calibration point. This approach is to shift each curve toward the nominal curve by subtracting the offset from or adding the offset to the average. The second is two-point correction technique, which requires two calibration points. Each point is rotated and aligned so that all the detectors have the same response under the same radiance. The third is multipoint correction. It is recommended that more calibration points be implemented at appropriate regions of the response curve. Depend on the linear photoelectric response of the TDI CCD, we use two-point calibration and the standard deviations for the images are given before and after the correction.

Small satellites are capable of performing space explore missions that require accurate attitude determination and control. However, low weight, size, power and cost requirements limit the types of attitude sensor of small craft, such as CCD, are not practical for small satellites. CMOS APS is a good substitute for attitude sensors of small craft. Some of the technical advantages of CMOS APS are no blooming, single power, low power consumption, small size and little support circuitry, direct digital output, simple to system design, in particular, radiation-hard characteristic compare with CCD. This paper discusses the application probability of CMOS APS in star tracker for small satellites, further more, a prototype ground-based star camera based on STAR250 CMOS image sensor has been built. In order to extract stars positions coordinates, subpixel accuracy centroiding algorithm has been developed and tested on some ground-based images. Moreover, the camera system star sensitivity and noise model are analyzed, and the system accuracy is been evaluated. Experimental results indicate that a star camera based on CMOS APS is a viable practical attitude sensor appropriate for space small satellites.

In this paper, the vision sensor is made up of four laser devices (LD) and four cameras. Standard difference value contrast method of calibration is put forward. The whole system’s parameter calibration is consisted by four sub-system’s calibration independently. Special target probe moves in standard grid mode in the measured two-dimensional plane. Gray-level centroid method is used to acquire four groups standard grid node. From the difference of standard grid node the segment linear calibration equations are obtained. The whole measured section is divided as grid block by every adjacent group standard mean coordinate values Z and Y. In the grid block all the measured coordinate values are calibrated by segment linear equations along Z and Y axis direction. The whole system is calibrated only by getting data once. The system calibration result shows the system measurement errors is less than 0.2 mm within 100 mm depth measurement.

Three-Line CCD Camera is a multi-channel solid mapping camera. There are three signal channels in one camera, and twelve channels in three cameras for the three-line CCD camera. Because there is a little difference between different channels, the image grey of different camera channels is a little difference for the same region. Those differences include in two aspect: the difference between the cameras each other and the difference between different channels of the same camera. So they make a mistake when the images of different channels are matched. In the paper, the camera response curves have been described through ground radiation calibration to the multi-channel camera, furthermore, the channels calibration coefficients have been gotten based on making a certain the output basis channel. So the differences between different channels are reduced through radiation calibrating each channel, and the outputs of all channels are almost same, the accuracy of matching image is improved.

Laser tracking method for space coordinates measurement is a newly developed technique that possesses the characteristics of high accuracy, large measuring range, flexible and dynamic measurement and so on. Laser tracking interferometer system based on this method has become an important measuring tool in many industrial fields. However, the control system sometimes acts nonlinearly because of long-range measurement and various applications. To solve this problem, artificial neural network (ANN) controller is introduced as an advanced adaptive control configuration in laser tracking interferometer system. The reason is that artificial neural network which is an important branch of intelligent control area has great potential ability in dealing with high nonlinearity and indeterminate factors. Then the simulation of tracking control system based on either conventional PID controller or ANN controller is carried out separately and the result of comparison is given.

CMOS image sensors now become increasingly competitive with respect to their CCD counterparts, while adding advantages such as no blooming, simpler driving requirements and the potential of on-chip integration of sensor, analogue circuitry, and digital processing functions. A safety monitoring system for taxi based on cmos imager that can record field situation when unusual circumstance happened is described in this paper. The monitoring system is based on a CMOS imager (OV7120), which can output digital image data through parallel pixel data port. The system consists of a CMOS image sensor, a large capacity NAND FLASH ROM, a USB interface chip and a micro controller (AT90S8515). The structure of whole system and the test data is discussed and analyzed in detail.

APT system is the key technology in free space optical communication system, and acquisition and tracking detector is the key component in PAT system. There are several candidate detectors that can be used in PAT system, such as CCD, QAPD and CMOS Imager etc. The characteristics of these detectors are quite different, i.e., the structures and the working schemes. This paper gives thoroughly compare of the usage and working principle of CCD and CMOS imager, and discusses the key parameters like tracking error, noise analyses, power analyses etc. Conclusion is given at the end of this paper that CMOS imager is a good candidate detector for PAT system in free space optical communication system.

The paper discusses practical aspects of LED measurements and problems about how to improve the measurement accuracy of LED spectral properties when using linear CCD sensor. Designed and implemented an instrument for LED spectral measurement based on linear CCD sensor. The CCD sensor has 2048 pixels and ultra-high sensitivity. The duration of one measurement is about 10ms. For reducing the effect of CCD output noise, a software filtering method is introduced. After software calibration, the accuracy of color temperature is 40K in the range of 1300K to 25000K, and accuracy of wavelength is 0.2nm in the range of 360nm to760nm. The accuracy of chromaticity coordinated (x, y) or (u, v) is better than 0.003.

Experiments of a lateral semi-insulating GaAs photoconductive switch, both linear and nonlinear mode of the switch were observed when the switch was triggered by 1064 nm laser pulses, with energy of 1.9 mJ and the pulse width of 60 ns, and operated at biased electric field of 4.37 kV/cm. It’s wavelength is longer than 876nm, but the experiments indicate that the semi-insulating GaAs photoconductive switches can absorb 1064 nm laser obviously, which is out of the absorption range of the GaAs material. It is not possible to explain this behavior by using intrinsic absorption mechanism. We think that there are two mostly kinds of absorption mechanisms play a key part in absorption process, they are the two-steps-single-photon absorption that based on the EL2 energy level and two-photon absorption.

Fiber optical Fabry-Perot (F-P) interferometric sensors have been used for the measurement of various physical parameters. A novel miniature asymmetric F-P interferometric cavity applied to fiber optical sensors is designed in this work; and its structure consists of fiber, complex metallic thin films, air or dielectric tunable layer, in which the reflectance of the cavity in response to phase thickness of the tunable layer can be approximated to saw wave function so it can improve the degree of linearity and the dynamic range of the sensors. The measurand to sense, which modulates the optical path of the tunable layer to change the reflectance of the structure, can be detected and demodulated. The response of the reflectance of the structure to the phase thickness of the tunable layer has been calculated and analyzed with optical thin film characteristic matrix method, and an expression for the response of this structure has been described. The design method to obtain optimal parameters of the F-P interferometric cavity has been concluded in this work. The result indicates that this miniature structure possess a high degree of linearity, sensitivity and dynamic range.

A wavelength-shifting interferometer has been constructed by using a wide-tunable Ti:sapphire laser for three-dimensional range measurement. The phase shifts in five steps by wavelength changes can be measured with an Schwider-Hariharan algorithm in conjunction with sub-fringe measurements by PZT movements in four steps. Experimental results for a step object have been shown.

Laser-diode phase-conjugate interferometer with two self-pumped (cat) phase-conjugate mirrors instead of two ordinary mirrors is constructed for distance measurements over extended ranges. The measurement is based on frequency-modulated continuous wave techniques. An external-cavity laser diode (ECLD) is used as a light source in a phase-conjugate wavefront-matched interferometer. The interferometer is insensitive to spatially nonuniform phase distortion, but can only detect the spatially uniform phase change introduced by the displacement of one cat mirror. The error due to the nonlinear frequency chirping of an ECLD can be free from the reference interferometer of fixed arms with a known optical path difference.

Ultrafast measurement system for transient electrical signals using a scanning tunneling microscope has been developed. The key of the system is a probe integrated with a low-temperature grown GaAs photoconductive switch that is used as a sampler of transient signals generated by ultrashort laser pulses with another photoconductive switch. The tunneling tip is attached to a coplanar strip transmission line with an integrated photoconductive switch. The probe fabrication process and tip characteristics have been reported here. A topographic STM image scanned with such a probe on a gold sample on Si substrate is given. A transient signal with 1.2 ps pulse width in tunneling mode and 2.0 ps in contact mode were observed with the probe.

A non-contact optical microscopy system is described. It adopts basic Michelson structure to measure the characteristic of end surface of the fiber connector. We take use of the Fourier transform to process interference pattern. Getting the high information of two-dimension section picture. We take use of the First Derivative is extremum and Second Derivative is zero to detect the edge jump points. And we take use of Least Square Method etc. curve fitting method to describe the two-dimension section picture. We analyze the method to measure geometrical parameters of end surface. Then we can measure the characteristic of end surface. For example: the geometric parameters and roughness.

A system for two-dimensional small rotation-angle measurement is proposed and demonstrated. Because the measurement is not conducted by the interference but the fringe projection, it is basically robust for the external disturbance. While the setup is very simple, there is no requirement on the size of the object. We also proposed two-dimensional two-grating method and a unit that miniaturizes the system. Several measurements confirm us that the measurement accuracy of our proposed system is ~0.4 arcsec.

A disturbance-free sinusoidal phase modulating laser diode interferometer using integrating bucket method is described. Several techniques make it suitable for use in the in-process measurement: the charge-coupled device (CCD) based additive operation on integrating-buckets shares the burden of data processing imposed on the computer; the modulating signal is matched with the CCD camera’s exposure time easily and exactly by using a dedicated waveform generator; the use of high speed shutter function of the CCD camera enables each bucket collection to be insensitive to the noise, while the interference signal’s stability is enhanced with the feedback control during entire measurement time. A surface profile measurement on a diamond-turned aluminum disk was demonstrated to evaluate the performance of this system.