The problem of particle field diagnosing using holography can be met in many areas. But single frame hologram can only catch one moment of the fast event, which can’t reveal the change process of an unrepeatable fast event. For events in different time-scale, different solution should be used. We did this work to record a laser induced particle field in the time-scale of tens of micron seconds. A laser of pulse sequence mode is applied to provide 10 pulses, the energy and time interval of whom is 150mJ and 1μs. Four pockels cells are employed to pick up the last four pulses for holographic recording, the other pulses are controlled to pre-expose the photopolymer based recording material, which can enhance photosensitivity of the photopolymer during the moment of holographic recording. The angular multiplexing technique and volume holography is accepted to avoid shifting the photopolymer between each shot. Another Q-switch YAG laser (pulse energy 100mJ, pulse width 10ns) is applied to produce the fast event. As a result, we successfully caught the motion process of the laser induced particle field. The time interval of each frame is 1μs, the angular range of the four references is 14°, and the diffraction efficiency of each hologram is less than 2%. After a basic analysis, this optical system could catch more holograms through a compact design.
A robot scanning system consisting of a portable laser 3-D scanner and an industrial robot is demonstrated. In this system, the scanner is precalibrated by the traditional nonlinear two-step approach. In addition, by using a criterion sphere as the calibration object, a new robot tool center point (TCP) calibration approach is proposed for calibrating the relation between the precalibrated laser 3-D scanner and the robot. In this approach, two different translational motions of the robot are first made to determine the rotation part, and then at least three different rotational motions are made to determine the translation part. During the process, the extrinsic camera parameters are not recalibrated for each robot motion, so the calibration errors brought by camera calibration can be decreased. Moreover, the calibration error due to robot positioning error can be decreased by making use of the differences of different robot positions in calculations. An experiment was performed on a portable laser 3-D scanner and an ABB IRB-4400 industrial robot to test the validity of the proposed calibration approach. The experimental results show that this approach is simple and accurate compared to the conventional robot TCP calibration approach.
A novel method for the fabrication of continuous micro-optical components is presented in this paper. It employs a computer controlled digital-micromirror-device(DMDTM) as a switchable projection mask and silver-halide sensitized gelatin (SHSG) as recording material. By etching SHSG with enzyme solution, the micro-optical components with relief modulation can be generated through special processing procedures. The principles of etching SHSG with enzyme and theoretical analysis for deep etching are also discussed in detail, and the detailed quantitative experiments on the processing procedures are conducted to determine optimum technique parameters. A good linear relationship within a depth range of 4μm was experimentally obtained between exposure dose and relief depth. At last, the microlensarray with 256.8μm radius and 2.572μm depth was achieved. This method is simple, cheap and the aberration in processing procedures can be corrected in the step of designing mask, so it is a practical method to fabricate good continuous profile for low-volume production.
A high-quality single-layer panchromatic dichromated gelatin material is achieved successfully by employing new types of multi-color photosensitizers and photochemical promoters to conventional photo-crosslinking gelatin system. Its holographic recording characteristics such as spectral response, the photosensitivity of three primary colors, spectral selectivity of volume reflection hologram, angular and wavelength selectivity of volume transmission hologram, are studied in detail. Using red, green and blue lasers, namely three primary colors, the bright volume transmission and reflection holograms can be recorded on the panchromatic material at the exposure level of 30 mJ/cm2. Some preliminary results of space, angle and wavelength multiplexing holographic storage for storing multiple binary and grey-tone optical images, are also reported in this paper.
A red-sensitive acrylamide-based photopolymer based on multiple polymerizable monomers is developed in this paper for holographic applications. In order to improve the spatial resolution of this photopolymer system, a new strategy of employing low molecular-weight polyvinyl alcohol as binder is proposed. The comparative experiments of different photosensitive system with various molecular weights (72000,15000, 9000) are conducted to study their effects on the diffraction efficiency and spatial resolution. The experimental results show that the photosensitive system with low molecular weight of 9000 has much higher resolution and diffraction efficiency, and bright volume transmission grating with spatial frequency of 3000 lines/mm and diffraction efficiency higher than 85% can be recorded successfully on the optimum photopolymer material at the exposure level of 40 mJ/cm2. Some preliminary applications of spatial and angular multiplexing holographic storage for storing multiple binary and grey-tone optical images, are successfully demonstrated.
Thick resist lithography is a rather complicated process, which involves quite a few nonlinear factors, so surface profile is largely affected by process conditions such as baking, exposure and development parameters. In this paper, the photochemical reaction mechanism of the thick diazonaphthoquinone(DNQ)-Novolak based photoresists is discussed in detail, and then the effect of exposure intensity on the photochemical reaction speed is investigated by using kinetic model. Numerical simulation and experimental results are presented and agree well with each other. Through comparison between the simulated and experimental results for thick DNQ-Novolak based resists, the photochemical reaction speed is obviously affected by the intensity magnitude during exposure, which will lead to the failure of exposure reciprocity law. This phenomenon is caused by the increase in temperature of resists, due to the highly exothermic reaction during exposure. These results are useful for the lithographic process optimization of thick film resists.
A novel method for the fabrication of continuous micro-optical components is presented in this paper. It employs a computer controlled spatial-light-modulator (SLM) as a switchable projection mask and silver-halide sensitized gelatin (SHSG) as recording material. By etching SHSG with enzyme solution, the micro-optical components with relief modulation can be generated through special processing procedures. The principles of digital SLM-based lithography and enzyme etching SHSG are discussed in detail, and microlens arrays, micro axicon-lens arrays and gratings with good profile were achieved. This method is simple, cheap and the aberration in processing procedures can be in-situ corrected in the step of designing mask, so it is a practical method to fabricate continuous profile for low-volume production.
In this paper, a red-sensitive photopolymer based on multiple polymerizable monomers is developed for holographic applications. The detailed quantitative experiments on the reagent concentrations, the exposure, the thickness of the photosensitive layer, are conducted to determine an optimum recipe, and bright volume phase holograms with high diffraction efficiency are obtained in our experiments at the exposure level of 4mJ/cm2. This photopolymer also has higher resolution and self-development capacity. This makes it very convenient and useful for the applications of both real-time and double exposure holographic interferometry, some preliminary experiments of holographic interferometry are demonstrated in this paper for the nondestructive testing and measurement of minor distortion and displacement.
By employing new types of multi-color photosensitizers and photochemical promoters to photo-crosslinking gelatin system, a high-quality single-layer panchromatic dichromated gelatin material is achieved for color holography. Some preliminary results of spectral response, photosensitivity, and spectral selectivity are reported in this paper. Using red, green and blue lasers, namely three primary colors, the bright volume transmission and reflection holograms can be recorded successfully on the panchromatic material at the exposure level of 30 mJ/cm2. It can be expected to have practical applications in the fields of true-color display holography, wavelength multiplexing holographic storage, and holographic optical elements.
Experimental and theoretical analysis indicates that many nonlinear factors existing in the exposure process of thick resist can remarkably affect the PAC concentration distribution in the resist. So the effects should be fully considered in the exposure model of thick resist, and exposure parameters should not be treated as constants because there exists certain relationship between the parameters and resist thickness. In this paper, an enhanced Dill model for the exposure process of thick resist is presented, and the experimental setup for measuring exposure parameters of thick resist is developed. We measure the intensity transmittance curve of thick resist AZ4562 under different processing conditions, and extract the corresponding exposure parameters based on the experiment results and the calculations from the beam propagation matrix of the resist films. With these modified modeling parameters and enhanced Dill model, simulation of thick-resist exposure process can be effectively developed in the future.
In this paper, as far as we know, it is the first time that a novel acousto-optic pure rotational Raman lidar based on acousto-optic tunable filter (AOTF) is put forward for the application of atmospheric temperature measurements. AOTF is employed in the novel lidar system as narrow band-pass filter and high-speed single-channel wavelength scanner. This new acousto-optic filtering technique can solve the problems of conventional pure rotational Raman lidar, e.g., low temperature detection sensitivity, untunability of filtering parameters, and signal interference between different detection channels. This paper will focus on the PRRS physical model calculation and simulation optimization of system parameters such as the central wavelengths and the bandwidths of filtering operation, and the required sensitivity. The theoretical calculations and optimization of AOTF spectral filtering parameters are conducted to achieve high temperature dependence and sensitivity, high signal intensities, high temperature of filtered spectral passbands, and adequate blocking of elastic Mie and Rayleigh scattering signals. The simulation results can provide suitable proposal and theroetical evaluation before the integration of a practical Raman lidar system.
In this paper, a new technique is presented for adjusting the playback wavelength of Lippmann holograms recorded in methylene-blue sensitized dichromated gelatin (MBDCG). The main feature of this technique is introducing a water-soluble organic reagent into MBDCG photosensitive layer as preswelling reagent and wavelength adjuster. This method has wide wavelength adjustment range and high signal-to-noise ratio, can be applied to adjust the playback wavelength of reflection hologram quantitatively by changing the concentration of preswelling reagent. Its possible applications include color image display, holographic optical elements, and optical anti-counterfeiting.
The CSG’s physical performance is decided by its structural parameters, such as width of grating stair, height of grating
stair, and the shape of stair edge. Consideration of the practical fabrication process, an error model of CSG’s structure is built to express the relationship between CSG’s performance and its structural parameters. In this model, each structural parameter of CSG is expressed as a variable, and the structural parameter error induced by fabrication process is expressed as minute disturb of relative variable. Through analysis and simulation, we obtained a general estimation standard for the structural parameter errors of CSG, which provides a theoretical direction for CSG’s fabrication and usage.
In this paper a new method has been developed for fabricating micro-optical element by exposing silver-halide sensitized gelatin (SHSG) through real-time mask and etching SHSG with enzyme solution. The principle of etching SHSG with enzyme solution is given in detail and the optimum technique parameters of this process are presented, furthermore the theoretical analysis and solving scheme for the nonlinearities which come from the absorption of light energy by film are given. It is experimentally obtained a good linear relationship in a range of 4µm deep. At last, the micro-cylindrical lens and micro axicon array are achieved by experiment, and the results are evaluated for experiments by stylus profiling instrument and interference microscope.
A new method is presented to encode and decode images with computer-generated hologram of fractional Fourier transform. The fractional Fourier transform computer-generated holograms (FRT-CGH) of several objects with different orders are respectively recorded on one holographic plate. In order to reconstruct images of the objects, several fractional Fourier transform systems of certain orders are needed. This method is agile and convenient on design and fabrication. It can be encoded and decoded either by numerical method or by optical method. Because of its particularity of image reconstruction, FRT-CGH is regarded as a new optical security system and may be widely used in the future.
In this paper, we present a new technique for adjusting and controlling the playback wavelength of Lippmann holograms recorded in methylene-blue sensitized dichromated gelatin (MBDCG). During the preparation of photosensitive layer, a water-soluble organic reagent, acrylamide is added homogeneously into our optimum MBDCG recipe as preswelling reagent. It will be dissolved completely into water during the postprocessing procedure and result in the uniform shrink of the fringe planes of reflection hologram, which will makes the playback wavelength shift relatively to shorter wavelength. This method can be applied to adjust the playback wavelength of reflection hologram quantitatively by changing the concentration ofpreswelling reagent.
The photopolymeriable gelatin (PPG) system we have studied comprises a mixture of acrylamide (AM), N,N'-methyknebisacylamide (BAM), triethanolaimine (TEA), methylene blue and gelatin. After wet processing, there is a thin layer of white fog, which results in the image noise of fabricated hologram. The factors which influence the noise in PPG system were studied in detail. They include monomer concentration ratio, TEA concentration, exposure energy and processing condition. The optimal condition that attributes to the lowest noise of PPG system is: (1) AM:BAM 30:1; (2) TEA%1%; (3)28°C of the washing temperature in the post-processing.
A new red sensitiver holographic recording material has been studied by our group. The composition of the material is as follows: polyvinyl alcohol as binder, acrylamide and methylene bisacrylamide as monomer, methylene blue as sensitizer, triethanolamine as electron donor and other additive reagents. We get the optimum recipe through many tests. By adding other reagents that were designed by us, we obtain a high quality red-sensitive holographic recording material. The diffraction efficiency of transmission holographic grating is up to 95%, when the exposure energy is 3mJ/cm2. The post-processing is simple, the hologram has high diffraction efficiency, high signal-to-noise ratio, and excellent environmental stability.
In this paper, based on the photosensitive characteristics of a photopolymer recording material — Photoetching Cellulose Film (PCF), some effective post-processing techniques such as delay-development, ultraviolet (UV) uniform post-exposure, and chemical etching development, are investigated to increase the diffraction efficiency and relief depth of PCF micro-optical and holographic elements. The delay development technique can obtain an enhancement factor of more than 50%, while both the UV post-exposure and chemical development techniques can achieve up to 100% enhancement factor.
Cleaving-etch method was presented for improving relief modulation resolution in gelatin. The principle of the method was introduced. Using the cleaving-etch method, a sine relief grating was obtained with 200 lines/mm spatial frequency and 0.4 micrometers relief depth. Comparison between enzyme-etching-imaging method and the cleaving-etch method was given and the reason why resolution of the latter much higher than the former was presented.
The problem connected with the color desaturation of reflection holograms on Russian PFG-03C panchromatic plate, has gained much attention. In this paper, we explore a new processing procedures to reduce emulsion shrinkage and wavelength shift and improve the color rendition and image quality.
During studying anti-humidity of dichromated-gelatin holograms by taking off strongly adsorbing humidity groups of gelatin, the phenomenon that both the amino groups and carboxyl groups of gelatin did participate in chelations with Cr is observed.
An investigation that the diffraction efficiency of dichromated gelatin (DCG) holograms is stable in the high humidity (RH equals 85%) environment is reported. In this study, the amino group, one strong absorbing humidity groups of gelatin in DCG, is modified with acetic anhydride and changed into weak absorbing humidity groups, amide groups. The procedures of the molecule enclosure did not obviously affect the diffraction efficient of DCG holograms.
In this paper, a novel photoetching cellulose film (PCF) is presented. The basic photochemical reaction process and the mechanism of image formation is discussed by means of electron spin resonance spectra and infrared spectra. The mixed absorption and phase modulation caused by color change and hotodegradation reaction leads to the stronger real-time effect, and developed PCF hologram is generated by pure positive surface relief modulation.
The stability of the latent image recorded in TMG-MBDCG was studied by means of investigating on the real-time diffraction efficiency. We found that the latent image will decline under low exposure, and such phenomenon can be reduced by heating. The mechanism of such decline is discussed in this paper also.
Available lifetime of red-sensitive-gelatin (RSG) system was investigated, experiments tells it is affected by concentration of electron donor essentially, there exists a relationship that is conditioning each other between improvement of sensitivity and the lifetime, this paper gives the analysis and directed by it, an optimized RSG recipe with its preparing process is reported herein.
In this paper, a novel photoetching cellulose film is presented. The basic photochemical reaction process and the mechanism of image formation is discussed by means of electron spin resonance spectra and infrared spectra. Meanwhile, its characteristics such as stronger real- time effect, higher spatial resolution, linear surface relief modulation capacity and delay development effect are investigated experimentally.
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