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This PDF file contains the front matter associated with SPIE Proceedings volume 7064, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.
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In this study we focus on the aluminium nitride (AlN). This material shows a large number of advantages associated with
good piezoelectric properties. Therefore, AlN is an excellent candidate for MEMS actuation where low dielectric loss,
low thermal drift and high signal-to-noise ratios are required. In this paper, the case of AlN driven cantilevers composed
of three thin layers deposited on the silicon substrate will be considered. Precise knowledge of physical and material
parameters of AlN applied in these simple elements are necessary for their further applications. However, up to now,
AlN still represents a technological challenge and many of its micromechanical and piezoelectric properties are not
precisely described. That is why, our study has been concentrated on determination of such parameters like the residual
thin film stresses, thermal expansion coefficient α and piezoelectric coefficient d31. In this paper the interactions between
the theoretical solution, the numerical FEM simulations and experimental results were performed. This hybrid
methodology allows to identify the main source of behaviors discrepancy between the physical and numerical model of
tested cantilevers. Obtained knowledge leads to optimization of the technological process and required parameters of
actuator functionality achievement by better understanding of the tested microdevices properties. In experimental
procedure, it was used nanoindentation tests for obtaining an elastic properties of AlN, interferometric techniques for
performing the static and dynamic measurements of cantilevers and scanning electron microscope for measuring
topography.
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In the context of this article we demonstrate a novel Fizeau interferometric system that copes with the presence of
vibrations. Besides the conventional high spatial, but low temporal resolution detector system (the CCD camera) used in
phase shifting interferometry, an additional high temporal, but low spatial resolution detector system was integrated, in
order to measure the random phase shifts that are induced under the influence of the vibrations. The additional sensor
consists of three photodiodes. The acquired analog signals enable the measurement of the occurring phase shifts at three
non-collinear locations on the test surface. The resulting phase shifts at the three individual locations enable the
determination of the random phase shifts over the entire image aperture. To avoid the smear phenomenon at very short
exposure time, a beam shutter was integrated. Another alternative is to integrate a pulsed laser diode, for this purpose the
concept of a wavelength meter is proposed. While the random oscillations of the test object are continuously measured,
the CCD camera acquires several interferograms. In consequence, a phase shifting algorithm for random phase shifts was
applied. In order to proof the validity of the new interferometer, a test surface of known topography was measured. The
results of the measurements in presence of vibrations show very good concordance with the surface data given by the
supplier. The analysis of the root mean square (RMS) over ten different measurement show a measurement repeatability
of about 0.004 waves (approximately 2.5 nm for 632.8 nm laser wavelength).
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In recent years a wide variety of liquid based optical elements have been conceived, designed and fabricated even for
commercial products like digital cameras. The impressive development of microfluidic systems in conjunction with
optics has led to the creation of a completely new field of investigation named optofludics. Among other things, the
optofluidic area deals with the investigation and the realization of liquid micro-lenses. Different methods and
configurations have been proposed in literature to achieve liquid variable micro-lenses.
This paper reports about the possibility to achieve lensing effect by a relatively easy to accomplish technique based
on an open microfluidic system consisting of a tiny amount of appropriate liquid manipulated by the pyroelectric effect
onto a periodically poled LiNbO3 substrate. Basically, an electrowetting process is performed to actuate the liquid film
by using the surface charges generated pyroelectrically under temperature variation. The configuration is electrode-less
compared to standard electrowetting systems, thus improving the device flexibility and easiness of fabrication. The
curvature of the liquid lenses has been characterized by interferometric techniques based on the evaluation of the phase
map through digital holography. The results showing the evolution of the lens curvature with the temperature variation
will be presented and discussed.
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The measurement accuracy in non contact profilometric techniques is generally limited by mechanical vibrations and by
geometrical defaults of the micro-scanning table. In order to free the measurement from these environnemental
perturbations, we describe a novel type of interferometric microscopy based on the well-known Spectroscopic Analysis
of White Light Interferograms (SAWLI). The originality of the presented set-up lies in the fixation of the reference plate
on the inspected object. As reference plate and sample are fixed together, the mechanical vibrations do not affect the
measurements. As a result the potential nanometric accuracy of interferometric microscopy is effective. This method
consists in measuring the air gap thickness between the reference plate and the sample. At the output of the spectral
interferometric microscope a channelled spectrum is observed. From this signal, the spectral phase is calculated using a
numerical seven points phase shifting algorithm allowing the measurement of the local height of the analyzed surface.
These preliminary results demonstrate the ability of this method as a point sensor. Then this technique will be
implemented in a high frequency scanning STIL technology named MPLS 180.
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The lateral shearing interferometer was applied to in vivo investigate the stability of the tear film surface covering
the contact lenses. The 8 mW HeNe laser was used as the light source. The sequences of interferograms were recorded
by CCD camera in real time during the inter-blink intervals at 25 fps, stored in a computer memory and numerically
processed. Every frame illustrates the pattern of interference fringes that corresponds to temporal stage of prelens tear
film surface. Fast Fourier Transform was used to quantitative evaluate tear film surface irregularities and the numerical
measure M2 was used to obtain quantitative description of the tear film smoothness. The M2 index is the lowest for the
smooth and regular surface of the tear film and its values increase if the prelens tear film begins to be unstable.
The proposed way of analysis of each interferogram gives opportunity to calculate the credibility of given M2 index and
automatically reject a part of a frame, that is not covered by interference fringes with an appropriate contrast due to eye
movement. The tear film smoothness has been measured on different types of soft contact lenses of 4 companies. The
significance differences in tear film stability have been noticed between low and high water content materials of contact
lenses. The tear film was less stable on low water content materials.
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Based on the discovery that cutting signals contain fractal patterns, a recurrence plot based methodology called
recurrence quantification analysis (RQA) is applied to the time series constructed using information contained in speckle
images of machined surface for chatter detection in turning operation. Variations in the roughness of machined surface
created by virtue of chatter, manifests as changes in the statistical properties of speckle images of the surface when
examined frame by frame along the axis of the machined part. A significant parameter of such images, the frame wise
average intensity value is extracted separately and arranged in sequence for constructing the time series. Since this time
series is found to be non-stationary in nature and due to the fact that the turning operation is low dimensional chaotic, the
nonlinear time series analysis methodology of RQA is used for analyzing the time series. The present study ascertains
that the derived time series do have a deterministic origin and it further investigates the sensitivity of the different RQA
variables to chatter cutting by analyzing this time series and demonstrates that this methodology is capable of capturing
the transition from regular cutting to the chatter cutting.
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Machine tool chatter is an unfavorable phenomenon during metal cutting, which results in heavy vibration of cutting
tool. With increase in depth of cut the cutting regime changes from chatter- free cutting to one with chatter. In this paper,
we propose the use of permutation entropy (PE), a conceptually simple and computationally fast measure to detect the
onset of chatter from the time series generated using laser speckle pattern recorded using Charge Couple Device (CCD)
camera. Laser speckle is an interference pattern produced by light reflected or scattered from different parts of the
illuminated surface. It is the superposition of many wave fronts with random phases, scattered from different parts of the
rough surface. If a speckle pattern is produced by coherent light incident on a rough surface, then surely the speckle
pattern, or at least the statistics of the speckle pattern, must depend upon the detailed surface properties. Therefore we
propose PE as an ideal measure, which can efficiently distinguish regular and complex nature of any signal, to extract
information about the roughness of the reflecting surface. In the present study two work pieces, one taper cut and one
step cut are machined to form cylindrical pieces, by continuously varying the depth of cut. As the depth of cut increases
the surface finish is expected to deteriorate, mainly due to the onset of chatter vibrations. To analyze the surface texture
characteristics, the speckle pattern is obtained by illuminating this curved surface using a collimated laser beam (5mW
Diode Laser at 676nm wavelength.). The laser beam is made to incident obliquely to the curved surface of the work
piece, and the speckle pattern is recorded using a CCD camera. The beam is scanned along the axis of the work-piece
and the speckle pattern is recorded at different regions at constant intervals. A time series is generated from the speckle
data and analyzed using PE.
Permutation entropy is a complexity measure suitable for regular, chaotic, noisy or reality-based signals. PE work
efficiently well even in the presence of dynamical and/or observational noise. Unlike other nonlinear techniques PE is
easier and faster to calculate as the reconstruction of the state space from time series is not required. Increasing value of
PE indicates increase in complexity of the system dynamics. PE of the time series is calculated using a one-sample shift
sliding window technique. PE of order n>=2 is calculated from Shanon entropy where the sum runs over all n!
permutations of order n. PE gives the information contained in comparing n consecutive values of the time series. The
calculation of PE is fast and robust in nature. Under situations where the data sets are huge and there is no time for
preprocessing and fine-tuning, PE can effectively detect dynamical changes of the system. This makes PE an ideal
choice for online detection of chatter, which is not possible with other conventional methods.
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We report application of phase shifting interferometric measurements to study of the spatially resolved quantum
efficiency (QE) of the semiconductor solar-cells. In our method solar-cell is illuminated by two sets of mutually spatially
orthogonal fringe patterns of known frequency, and varying phase (shifted phase). We report theoretical results obtained
using simple analytical model describing properties of small spot size defects, and preliminary experimental results
validating this method. The new method and new apparatus can be also used for studies of spectrally resolved QE.
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The authors have been working on the development of a white light interferometer to measure both inner and external
cylindrical surfaces. High precision diamond turned conical mirrors were used to shape the light beam appropriately.
Collimated light from a Michelson-like white light interferometer was directed to the conical mirror. The reflected light
was radially directed to the cylindrical part to be measured. A telecentric lens system captured the image of the measured
cylindrical part reflected on the conical mirror surface. Scanning of the measured volume was performed in cylindrical
coordinates by linear displacement of a flat mirror in the reference arm of the interferometer. A cloud of points was
directly built in cylindrical coordinates. The present paper focus on two main topics of recent development: wear
measurement of cylinders and cylindrical part alignment. An appropriate mathematical model was developed to fit the
cylindrical cloud of points to the experimental data. The use of the least absolute method instead of the least squares
method for fitting the model is presented and discussed. This model is used to align two measured cloud of points to a
same reference coordinate system, one acquired before and the other after a wearing test. Direct comparison between
both clouds of points allowed computing the volume of the removed material by wearing. Results are presented and
discussed for both cases.
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In characterizing the performance of a phase-shifting interferometer, the dependence of the measured height on the
spatial frequency is rarely considered. We describe a test mirror with a special height relief that can be used to measure
the height transfer function for the interferometer in a fashion analogous to the measurement of the modulation transfer
function for the optical imaging system. We fabricated the test mirror at the National Institute of Standards and
Technology (NIST) using a lithography-based process. The test mirror has several patterns (reminiscent of moth
antennae) with variable spacing in radial direction. We describe the fabrication of the test mirror and its application to
test the performance of the interferometer.
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In previous work, wavefront coding technology has been applied on an off-axis three mirror
anastigmatic optical system. The secondary mirror is selected as the wavefront coded element.
After redesigned the surface of secondary mirror becomes an unusual unrotational-symmetric
surface with cubic term, which can not be tested by traditional null testing with compensator. For
preparing for manufacturing and testing this kind of elements, a simple cubic surface whose
equation is z=3λ(x3 + y3) (where x, y is normalized coordinate, λ=0.6328 μm) is polished.
The final surface figure is 0.327λ(PV) and 0.023λ(RMS). The manufacture of this surface is
introduced in this paper. The tilt component is subtracted to minimize the material removal. Also a
non-null method is described for testing the experimental element. The deviation from a reference
plane of the cubic surface is regarded as system error. In another words, the ideal cubic surface is
set as the reference artificially. A special system error file for interferometer can be created so that
the cubic term can be extracted during the testing process automatically. The residual error is just
the departure from the ideal figure of the surface under machining by this way. The error and
effective range is also presented. But the method may not be practical for the secondary mirror as
wavefront coded element because the surface of that kind is convex asphere added cubic term. An
improved non-null method is discussed for testing this kind of surface.
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CSIRO's Australian Centre for Precision Optics has recently finished the production of a high-precision concave
spherical mirror. The specifications were very ambitious: numerical aperture 0.75; asphericity below 5.5 nm rms and
27.3 nm P-V. The available reference transmission sphere had to be calibrated to enable adequate accuracy. Due to the
high numerical aperture of the mirror, sub-aperture measurements had to be stitched together to form a complete surface
map of the mirror.
Phase-shifting interferometry at high numerical aperture suffers from phase-step non-uniformity because of the large off-axis
angles. We present what we believe to be a new interpretation of this phenomenon as a focus error, which clarifies
where in the interferometer the phase-shift error occurs.
We discuss the ball-averaging method for calibrating the reference transmission sphere and present results from the
averaging process to ensure an uncertainty commensurate with the certification requirement.
For carrying out the sub-aperture measurements, we constructed a two-axis gimbal mount to swivel the mirror around the
focus of the test wavefront. If the centers of curvature of the transmission sphere and the mirror coincide, the mirror can
be tilted without losing the interferogram. We present a simple and effective alignment method, which can be generally
applied to optical tests where the wavefront comes to a focus.
The mirror was coated with protected aluminum and tested in its mount. No effect on the sphericity error from the
coating was found, and the specifications were exceeded by approximately 30%. We discuss subtleties of the stitching
process on curved surfaces and report final results.
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Wavefront curvature sensing with phase error correction system is carried out using phase retrieval based on a partially-developed
volume speckle field. Various wavefronts are reconstructed: planar, spherical, cylindrical, and a wavefront
passing through the side of a bare optical fiber. Spurious fringe pattern in the reconstructions due to a small tilt in the
plane illumination wave is detected and numerically corrected for. Difference in the curvatures of two spherical
wavefronts is also evaluated. Possible applications include angular displacement and range measurements.
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The Space Interferometry Mission - Planet Quest Lite (SIM-PQL) Guide 2 telescope system is currently being developed
at JPL. The SIM-PQL is a new mission concept to perform micro-arcsecond narrow-angle astrometry to search
approximately 50 nearby stars for Earth-like planets, and to perform global astrometry with an accuracy of six micro-arcseconds
in position and parallax. The novel cost and mass reducing "Lite" concept includes reduction in
interferometer baselines and replacing the second guide interferometer (Guide 2) with a telescopic system. The resulting
simplification still allows meeting most science goals without significant performance degradation. The Guide 2
telescope employs a nulling pointing control system that utilizes a Fast Steering Mirror (FSM) as an actuator and a star
tracking CCD camera as a control sensor. Under the nulling closed loop control, the modulated attitude motion of the
instrument is picked off by a metrology FSM tip-tilt sensor (AMET). The Guide 2 pointing control system requires mili-arcsecond
class fine pointing, maintenance of low jitter and thermal stability and a sub-nanometer class metrology
system that ties the sensor bench to rest of the instrument. This paper presents the Guide 2 telescope pointing control
system design and resulting performance estimates. The pointing control requirements are first stated followed by the
descriptions of the system architecture, algorithm design and simulation results. Concept and algorithm validation is
conducted on a workstation-based simulation testbed, specifically developed to capture critical sensor/actuator behavior
and environmental disturbances.
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The technology path to produce low cost microinterferometric heads in plastic and the optical methods for quality
investigations of these elements are presented. Specifically the interferometric and photoelastic tomography methods,
applied for the 3D studies of refractive index (n) and birefringence (B) in photonics components replicated by means of
hot embossing (HE) technology, are investigated. The enhanced automated measurement and data analysis procedures
are described and the experimental results obtained for micro-objects working in transmission are given. Also the
methodology to combine the tomographic data for full characterization of internal structure of 3D photonics elements is
provided. The samples under test are massive waveguide microinterferometerers in the form of cuboids produced by hot
embossing process characterized by a variety of parameters. The systematic tomographic studies of 3D distribution of n
and B provided important information for extending knowledge about the process and optimization hot embossing
technology. The tomographic measurements are supported by measurements of top and side walls profile and roughness.
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A white-light interferometer with new signal analysis techniques provides 3D top surface and thickness profiles of
transparent films. With an additional change from conventional object imaging to pupil-plane imaging, the same
instrument platform provides detailed properties of multilayer film stacks, including material optical properties. These
capabilities complement conventional surface-topography measurements on the same platform, resulting in a highly
flexible tool.
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We present a numerical technique for automatic extended focused imaging and three-dimensional analysis of
microparticle field observed in a digital holographic microscope working in transmission. We use Fourier method
for the extraction of complex amplitude from the single exposition digital holograms. We create a synthetic
extended focused image (EFI) using the focus plane determination method based on the integrated amplitude
modulus. We apply the refocusing criterion locally for each pixel, using small overlapping windows, in order to
obtain a depth map and a synthetic image in which all objects are refocused independent from their refocusing distance. The obtained synthetic EFI allows us to perform image segmentation and object detection. We improve the accuracy of vertical localization using an additional refining procedure in which each particle is treated separately. A successful application of this technique in the analysis of microgravity particle flow experiment is presented.
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The paper deals with the analysis of the uncertainty of high precision long range three-dimensional Nanopositioning and
Nanomeasuring Machines (NPMM). Those high-tech instruments consisting of precision 3d-guides, interferometers, a
3d-reference-mirror and nanoprobes, connected by a stabile frame are subject of research. Especially the interferometer
mirror system characterizes the precision of such machines. Therefore a new vectorial metrological model will be
described to characterize this machine part. Its properties and advantages are shown and the model is used to analyze the
uncertainty budget of a concrete Nanopositioning and Nanomeasuring Machine.
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Spatial light modulators (SLM) are used in different microscopy setups. Examples are optical tweezers, programmable
phase contrast imaging, confocal imaging, and aberration correction. We report on a method that
measures and corrects specimen-induced aberrations in wide-field microscopy without additional optical components
(e.g. Shack-Hartmann sensors) by taking advantage of the SLM that is already used in the setup.
Different local gratings are written into the SLM which is positioned in a plane conjugate to the pupil of the
imaging system. Multiple images are recorded and based on the shift of subimages we deduce the wavefront. We
demonstrate first experimental results of this method for a system using a high resolution LCoS modulator.
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In the paper the multiwavelength interferometer with automatic data analysis based on phase fraction method is
described. It is used to extend measurement range without losing sensitivity, especially to calibrate long gauge blocks.
Numerical simulations and experimental work results have been shown to confirm proper functioning of this method.
However, stabilization of environmental conditions and light sources has significant influence on correctness of
measurement results. To match those requirements measurement system, which will be built for Polish Central Office of
Measures, has been designed. This design is based on Twyman-Green interferometer and assumes usage of two highly
stabilized laser sources. Optical and mechanical design of this system has been shown. Moreover, system for monitoring
and stabilization of environmental conditions is required.
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Deep Proton Writing (DPW) is a rapid prototyping technology allowing for the fabrication of micro-optical and micro-mechanical
components in PMMA, which are compatible with low-cost replication technologies. Using DPW, a high-precision
2D fiber connector featuring conically-shaped micro-holes for easy fiber insertion, was realized. When
populating these fiber connectors by fiber insertion and fixation, a critical issue is the accurate control of the fiber
protrusion. The use of laser interferometry to measure the fiber's facet position with respect to the connector surface to
within a few micrometers, is inconvenient in view of the measurement range as compared to the fiber dimensions. In this
paper, we propose an interferometric method for in-situ monitoring of the fiber insertion depth, based on the
phenomenon of low temporal coherence light interference in a Twyman - Green setup. In addition, achieving a few
micrometers measurement range with low coherence light requires vertical scanning of the sample under test. The design
of the experimental setup and the achieved measurement results are shown and discussed.
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By using a CGH test plate fabricated with our equipment and techniques, we measured a
perfect sphere surface. The measurement result is quantified into four parts: the figure error from the
spherical surface under test; the figure error from the spherical reference surface; the error from
hologram and the adjustment error from misalignment. The measurement result removed from the later
three errors, shown excellent agreement with Zygo test of the same sphere surface. This verified that
the measurement accuracy by using this kind of CGH could be very high.
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An interesting problem that has concerned forensic scientist for many years, is their need for accurate, reliable
and objective methods for performing fracture matching examinations. The aim of these fracture matching
methods is to determine if two broken object halves can be matched together, e.g., when one half is recovered
at a crime scene, while the other half is found in the possession of a suspect. In this paper we discuss the use
of a commercial white-light profilometer system for obtaining 2D/3D image surface scans of multiple fractured
objects. More specifically, we explain the use of this system for digitizing the fracture surface of multiple facing
halves of several snap-off blade knives. Next, we discuss the realization and evaluation of several image processing
methods for trying to match the obtained image scans corresponding to each of the broken off blade elements
used in our experiments. The algorithms that were tested and evaluated include: global template matching
based on image correlation and multiple template matching based on local image correlation, using so-called
"vote-map" computation. Although many avenues for further research still remain possible, we show that the
second method yields very good results for allowing automated searching and matching of the imaged fracture
surfaces for each of the examined blade elements.
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In order to determine the properties of thin films with the required performance and reliability, a sensing system for
dynamic monitoring is proposed to measure the thickness of thin films. The system is based on the principle of
white-light interference, and is combination of spectrum analysis and optical fiber techniques. When two reflected lights
interfere within white-light coherent length range, relationship of between interference intensity and the wavelength of
incident light is achieved according to the equation of interference light's intensity. According to different thickness of
film, the relevant method is selected to calculate the thickness of thin film. So the interference can be analyzed in
spectral domain. The scheme of the system is set up including white-light source, multi-mode optical fiber, beam splitter,
spectrometer. With the help of optical fiber, the interference pattern is captured by spectrometer. When thickness of thin
film is varying, spectra curve will shift. The original spectra curve is processed in the computer. In order to determine
accurate extreme points, many methods of curve processing are used to decrease the noise. The spectra curve is
smoothed by signal processing method called empirical mode decomposition (EMD). This method is suitable for
non-linear and non-stationary data processing. The experimental data is contrast to the calibrated value. The results
show that the relative error of this method is lower 1%. This method has advantages over other measuring methods, such
as higher accuracy, low-cost instrument, extensive measurement range, simple structure and non-destructive.
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The design and system performance of a far-infrared interferometer with which to test rough aspheric surfaces are
presented. It is based on the optical configuration of classical Fizeau interferometer. A CO2 laser is used as a light source
operating at a 10.6μm wavelength. A He-Ne laser is introduced into the interferometer to solve problems concerning
with alignment. The measuring error(RMS) of the interferometer is less than λ/200(λ=10.6μm), this accuracy is able to
fulfill the need of grinding primary mirror.
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In this study, a simple method for measuring the small displacements is presented. When a circularly polarized
heterodyne light beam reflected from a mirror is incident into a hemi-spherical prism and is reflected at the base of the
prism. Then the reflected light beam passes through an analyzer for interference. With properly chosen azimuth angles of
transmission axis of the analyzer, the phase difference between s- and p- polarized light is sensitive to the incident angle
near the internal reflection polarization angle. The phase difference can be accurately measured with the heterodyne
interferometry. The small displacement of the mirror causes a small variation of incident angle and a phase change.
Therefore, substituting the phase difference into special derived equations; the small displacement can be determined.
The proposed method has advantages of common-path configuration and heterodyne interferometry.
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In ophthalmology, the laser excimer corneal surface ablation used to correct the refractive eye defects, such as myopia,
astigmatism and hyperopia and, more recently, presbyopia is known as refractive surgery. Typically, the characterization
of the corresponding technique, as well as the laser accuracy, is performed by analyzing standard ablation profiles made
on PMMA (polymethylmethacrylate) plates. A drawback of this technique is that those plates do not necessarily
represent the dimensions of the cornea during the ablation. On the other hand, due to the time varying process of the eye
aberrations, the direct eye refractometric measurements can produce some errors. We report in this work the
interferometric analysis of the ablation profile obtained with refractive surgery, applied directly on a contact lens. In this
case, the resultant ablation profile might be closer to the real profile as well as time invariant. We use, as a reference, a
similar contact lens without ablation. The preliminary results of the characterization of the corresponding ablation profile
are also presented.
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The concept of spatial coherence wavelet has been introduced some years ago with very productive results. It has given
new insight on the fundamental optical phenomena, and has predicted novel light characteristics like polarizations
domain and transverse energy transference. The concept of marginal power spectrum emerges as the amplitude of the
wavelet and provides a phase-space representation of the optical field in any state of spatial coherence. Its values have
energy units and are carried by the spatial coherence wavelets along specific paths or rays. Some of them, called carrier
rays, are corresponding to the radiant energy of the field, but the rest, called dark (or tamasic) rays, do not contribute to
the radiant energy, i.e. they take on positive and negative values, symmetrically distributed, which are responsible for the
constructive and destructive interference after redistributing the radiant energy of the field. This description of
interference is illustrated by analyzing the Young experiment, gratings and one-dimensional apertures. Furthermore, the
principle of spatial coherence modulation is introduced, showing its feasibility for practical applications in beam
shaping.
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