Optical Engineering

The field of digital image processing is reviewed with reference to its origins, progress, current status, and prospects for the future. Consideration is given to the evolution of image processor display devices, developments in the functional components of an image processor display system (e.g. memory, data bus, and pipeline central processing unit), and developments in the software. The major future trends include: increased performance through very large scale integration and integral array processors, the use of the optical video disc as an image storage medium, and automatic image analysis.

A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

A novel region-based active contour model (ACM) is proposed in this paper. It is implemented with a special processing named Selective Binary and Gaussian Filtering Regularized Level Set (SBGFRLS) method, which first selectively penalizes the level set function to be binary, and then uses a Gaussian smoothing kernel to regularize it. The advantages of our method are as follows. First, a new region-based signed pressure force (SPF) function is proposed, which can efficiently stop the contours at weak or blurred edges. Second, the exterior and interior boundaries can be automatically detected with the initial contour being anywhere in the image. Third, the proposed ACM with SBGFRLS has the property of selective local or global segmentation. It can segment not only the desired object but also the other objects. Fourth, the level set function can be easily initialized with a binary function, which is more efficient to construct than the widely used signed distance function (SDF). The computational cost for traditional re-initialization can also be reduced. Finally, the proposed algorithm can be efficiently implemented by the simple finite difference scheme. Experiments on synthetic and real images demonstrate the advantages of the proposed method over geodesic active contours (GAC) and Chan-Vese (C-V) active contours in terms of both efficiency and accuracy.

I ntegration of images from different sensing modalities can produce information that cannot be obtained by viewing the sensor outputs separately and consecutively. This paper introduces a hierarchical i mage merging scheme based on a multiresolution contrast decomposition (the ratio of a low-pass pyramid). The composite images produced by this scheme preserve those details from the input images that are most relevant to visual perception. The method is tested by merging parallel registered thermal and visual images. The results show that the fused i mages present a more detailed representation of the depicted scene. Detection, recognition, and search tasks may therefore benefit from this new image representation.

Poly(vinylferrocenium) perchlorate/poly(3,4-ethylenedioxythiophene) (PVF + /PEDOT) composite film was synthesized electrochemically on Pt electrode in a methylene chloride solution containing a mixture of poly(vinylferrocene) (PVF) polymer and 3,4-ethylenedioxythiophene monomer. PVF polymer in composite film was used as an electron transfer mediator in the electrochemical oxidation of compounds due to its perfect reversible redox properties. The resulting composite film was characterized electrochemically, spectroscopically and conductivity measurements. Ascorbic acid (AA) was selected as a model compound to evaluate the electrocatalytical ability of the PVF + /PEDOT composite film-coated electrode. The resulting coating exhibits significant electrochemical activity toward AA in 0.1 M phosphate buffer solution at pH 7, with high sensitivity and a wide linearity range. The steady state current vs. the concentration of AA are linear in the range of 2.22 × 10 −4 -6.4 × 10 −2 mol L −1 and 6.4 × 10 −2 -2.16 × 10 −1 mol L −1 , respectively, for two linear regions. Limit of detection (LOD) was found to be 6.67 × 10 −5 mol L −1 at 0.35 V vs. SCE. The interaction of AA with PVF + and PEDOT homopolymer films was investigated electrochemically and spectroscopically. The results showed that the catalytic activity of PEDOT-coated electrode was improved by the addition of PVF + . Applicability of the composite film was investigated by using pharmaceutical tablets, employing amperometric I-t method.

This paper presents the activities in the field of shearography in chronological order and highlights the great potential of this holographic measurement technology. After a brief introduction, the basic theory of shearography is presented. Shear devices, phase-shift arrangements, and multiplexed shearography systems are described. Finally, the application areas where shearography has been accepted and successfully used as a tool are presented.

A new methodology for fusing satellite sensor imagery, based on tailored filtering in the Fourier domain is proposed. Finite-duration Impulse Response (FIR) filters have been designed through an objective criterion, which depends on source image characteristics only. The designed filters allow a weighted fusion of the information contained in a fine spatial resolution image (PAN) and in a multispectral image (MULTI), respectively, establishing a trade-off between spatial and spectral quality of the resulting fused image. This new technique has been tested with Landsat Enhanced Thematic Mapper Plus (ETM+) imagery. Spatial and spectral quality of the fused images was compared with the results provided by Mallat's Wavelet algorithm. The images fused by the proposed method were characterized by a spatial resolution very close to the PAN image, and by the spectral resolution of the MULTI image.

CONTENTS 1. Introduction 2. Theory 3. Experiment and data 3.1. Experiment 3.2. Data 4. Comparison of ß2 values to theory 4.1. Two-photon absorption theory 4.2. Comparison to theory 5. Self-refraction 6. Optical limiter 7. Conclusion 8. Acknowledgments 9. References Abstract. Two-photon absorption coefficients ß2 of ten direct gap semiconductors with band-gap energy Eg varying between 1.4 and 3.7 eV were measured using 1.06 pm and 0.53 pm picosecond pulses. ß2 was found to scale as E93, as predicted by theory for the samples measured. Extension of the empirical relationship between ß2 and Eg to InSb with Eg = 0.2 eV also provides agreement between previously measured values and the predicted ß2. In addition, the absolute values of ß2 are in excellent agreement (the average difference being <26 %) with recent theory, which includes the effects of nonparabolic bands. The nonlinear refraction induced in these materials was monitored and found to agree well with the assumption that the self-refraction originates from the two-photon-generated free carriers. The observed self-defocusing yields an effective nonlinear index as much as two orders of magnitude larger than CS2 for comparable irradiances. This self-defocusing, in conjunction with twophoton absorption, was used to construct a simple, effective optical limiter that has high transmission at low input irradiance and low transmission at high input irradiance. The device is the optical analog of a Zener diode.

We present a new design for simultaneous strain and temperature measurement using a high-birefringence fiber loop mirror (HiBi-FLM) concatenated with a temperature-insensitive long-period grating (LPG) written in a photonic crystal fiber (PCF). The FLM acts as a sensor head, while the LPG in PCF serves as a filter to convert wavelength variation to optical power change. By measuring the wavelength variation and the power difference of two near peaks in the spectral response of this configuration, simultaneous strain and temperature measurement is obtained.

In this paper, a power and bandwidth efficient pulsed modulation technique for optical wireless (OW) communication is proposed. The scheme is called optical spatial modulation (OSM). In OSM, multiple transmit units exist where only one transmitter is active at any given time instance. The spatially separated transmit units are considered as spatial constellation points. Each unique sequence of incoming data bits is mapped to one of the spatial constellation points, i.e., activating one of the transmit units. This is the fundamental concept of the spatial modulation (SM) technique. In OW communication systems, the active transmitter radiates a certain intensity level at a particular time instance. At the receiver side, the optimal SM detector is used to estimate the active transmitter index. An overall increase in the data rate by the base 2 logarithm of the number of transmit units is achieved. The optical MIMO (multiple-input multiple-output) channel and the channel impulse response are obtained via Monte Carlo simulations by applying ray tracing techniques. It will be shown in this paper that the optical MIMO channel is highly correlated if transmitter and receiver locations are not optimized, which results in a significant power penalty. The power efficiency can be improved by increasing the number of receive units to enhance receive diversity and/or by using soft and hard channel coding techniques. Conversely, it is shown that aligning transmit and receive units creates nearly uncorrelated channel paths and results in substantial enhancements in system performance even as compared to the diversity or coding gain. The resultant aligned scheme is shown to be very efficient in terms of power and bandwidth as compared to on-off keying, pulse position modulation, and pulse amplitude modulation. In this paper also, the upper bound bit error ratios of coded and uncoded OSM are analyzed. The analytical results are validated via Monte Carlo simulations and the results demonstrate a close match.

A method to merge images from different sensing modalities for visual display was introduced by Toet, van Ruyven, and Valeton in 1989, which produces a fused image by nonlinear recombination of the ratio of low-pass (RoLP) pyramidal decompositions of the original images. The appearance of merged images that are produced by this scheme is highly dependent on the contrast and mean gray level of the input images. That nonlinear multiplication of the successive layers of a ratio of lowpass pyramid results in a contrast-enhanced image representation that i s highly invariant for changes in the global gray-level characteristics of the original image is shown. Application of this nonlinear multiplication procedure in the image fusion process results in composite images that appear highly independent of changes in lighting and gray-level gradients i n the input images. The method is tested by merging different degraded versions of parallel registered thermal (FLIR) and visual (CCD) images.

The high-energy/high-power section of the NIF laser system contains 7360 meter-scale optics. Advanced optical materials and fabrication technologies needed to manufacture the NIF optics have been developed and put into production at key vendor sites. Production rates are up to 20 times faster and per-optic costs 5 times lower than could be achieved prior to the NIF. In addition, the optics manufactured for NIF are better than specification giving laser performance better than the design. A suite of custom metrology tools have been designed, built and installed at the vendor sites to verify compliance with NIF optical specifications. A brief description of the NIF optical wavefront specifications for the glass and crystal optics is presented. The wavefront specifications span a continuous range of spatial scale-lengths from 10 µm to 0.5 m (full aperture). We have continued our multi-year research effort to improve the lifetime (i.e. damage resistance) of bulk optical materials, finished optical surfaces and multi-layer dielectric coatings. New methods for post-processing the completed optic to improve the damage resistance have been developed and made operational. This includes laser conditioning of coatings, glass surfaces and bulk KDP and DKDP and well as raster and full aperture defect mapping systems. Research on damage mechanisms continues to drive the development of even better optical materials. Table 1. Summary of the number and types of large aperture (~0.5 to 1.0 m) optics used on the NIF Optic Number required Key material(s) Amplifier slabs 3072 Phosphate glass Mirrors and polarizers 1600 HfO 2 /SiO 2 coating on BK-7 Windows and lenses 1728 SiO 2 Crystals 576 DKDP and KDP Gratings 192 SiO 2 Debris shields 192 SiO 2 Total: 7360

The concentration of the main minerals present in human hair is measured on several subjects by Calibration-Free Laser-Induced Breakdown Spectroscopy ͑CF-LIBS͒ and compared with the results obtained through a commercial analytical laboratory. The possibility of using CF-LIBS for mineral analysis in hair is discussed, as well as its feasibility for the fast and inexpensive determination of the occurrence of heavy-metal poisoning in hair.

We review the history and current status of ion exchanged glass waveguide technology. The background of ion exchange in glass and key developments in the first years of research are briefly described. An overview of fabrication, characterization and modeling of waveguides is given and the most important waveguide devices and their applications are discussed. Ion exchanged waveguide technology has served as an available platform for studies of general waveguide properties, integrated optics structures and devices, as well as applications. It is also a commercial fabrication technology for both passive and active waveguide components. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

Half a century has passed since Theodore Maiman's small ruby rod crossed the threshold of laser emission. The breakthrough demonstration earned headlines, but in the early years the laser was called "a solution looking for a problem," and there was a germ of truth in the joke. Years of development since then have vastly improved laser performance, and tremendously increased their variety, earning lasers important roles in scientific research, consumer products, telecommunications, engineering, medicine, materials working, and a host of other applications. This article reviews the highlights of those developments and puts them into context, showing how laser technology has evolved to meet application requirements.

A pixel-based color-mapping algorithm is presented that produces a fused false color rendering of two gray-level images representi ng different sensor modalities. The resulting images have a higher information content than each of the original images and retain sensorspecific image information. The unique component of each image modality is enhanced in the resulting fused color image representation. First, the common component of the two original input images is determined. Second, the common component is subtracted from the original i mages to obtain the unique component of each image. Third, the unique component of each image modality is subtracted from the image of the other modality. This step serves to enhance the representation of sensor-specific details in the final fused result. Finally, a fused color image is produced by displaying the images resulting from the last step through, respectively, the red and green channels of a color display. The method is applied to fuse thermal and visual images. The results show that the color mapping enhances the visibility of certain details and preserves the specificity of the sensor information. The fused images also have a fairly natural appearance. The fusion scheme involves only operations on corresponding pixels. The resolution of a fused image is therefore directly related to the resolution of the input images. Before fusing, the contrast of the images can be enhanced and their noise can be reduced by standard image-processing techniques. The color mapping algorithm is computationally simple. This implies that the investigated approaches can eventually be applied in real time and that the hardware needed is not too complicated or too voluminous (an important consideration when it has to fit in an airplane, for instance). © 1996 Society of Photo-Optical Instrumentation Engineers .

Free space laser system performance is limited by atmospheric turbulence that has been described for many years by Kolmogorov's power spectral density model because of its simplicity. Unfortunately several experiments have been reported recently that show Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly, in particular in portions of the troposphere and stratosphere. In this paper we present a Non-Kolmogorov power spectrum which uses a generalized exponent instead of constant standard exponent value 11/3 and a generalized amplitude factor instead of constant value 0.033. Using this new spectrum in weak turbulence, we carry out, for horizontal path, analysis of Long Term Beam Spread, Scintillation index, Probability of fade, mean SNR and mean BER as variation of the spectrum exponent.

Commercial EUV lithographic systems require multilayers with higher reflectance and better stability than those published to date. This work represents our effort to meet these specifications. Interfaceengineered Mo-Si multilayers with 70% reflectance and 0.545-nm bandwidth at 13.5-nm wavelength and 71% reflectance with 0.49-nm bandwidth at 12.7-nm wavelength were developed. These results were achieved with 50 bilayers. These new multilayers consist of alternating Mo and Si layers separated by thin boron carbide layers. Depositing boron carbide on the interfaces leads to reduction in molybdenum silicide formation of the Mo-on-Si interfaces. Bilayer contraction is reduced by 30%, implying that there is less intermixing of Mo and Si to form silicide. As a result, the Mo-on-Si interfaces are sharper in interface-engineered multilayers than in standard Mo-Si multilayers. The optimum boron carbide thicknesses have been determined and appear to be different for the Mo-on-Si and Si-on-Mo interfaces. The best results were obtained with 0.4-nm-thick boron carbide layers for the Mo-on-Si interfaces and 0.25-nm-thick boron carbide layers for the Si-on-Mo interfaces. The increase in reflectance is consistent with multilayers having sharper and smoother interfaces. A significant improvement in oxidation resistance of EUV multilayers has been achieved with ruthenium-terminated Mo-Si multilayers. The best capping-layer design consists of a Ru layer separated from the top Si layer by a boron carbide diffusion barrier. This design achieves high reflectance and the best oxidation resistance during EUV exposure in a water-vapor (oxidizing) environment. Electronbeam exposures of 4.5 h (in an effort to simulate EUV exposure perturbation of the top layers) in the presence of 5ϫ10 Ϫ7 -Torr water-vapor partial pressure show no measurable reflectance loss and no increase in the oxide thickness of Ru-terminated multilayers.

During the last decade, significant advances in the field of remote detection of ultrasound have taken place. Optical systems with increasing sensitivity for monitoring ultrasound on samples with optically rough surfaces have been developed, so that some designs are now moving from the research laboratory into industrial environments. In this review, a range of optical techniques is presented. These techniques are analysed regarding their use for the measurement of ultrasonic waves. They include the use of optical self-mixing, phase modulators and photorefraction-based interferometers. For the case of
established instruments such as two-beam interferometers and Fabry–P´erot interferometers,various newly developed configurations with associated ultrasonic transfer functions are
described. Many interferometers have broadband frequency responses that extend up to several hundred megahertz. Some systems offer in-plane ultrasonic measurement, whilst most offer out-of-plane measurements. Emphasis is placed on their potential for industrial applications, taking into account the likely sample-surface roughness and environmental vibration.

This paper addresses a novel robust watermarking method for digital images using local invariant features. Most previous watermarking algorithms are unable to resist geometric distortions that desynchronize the location where copyright information is inserted. We propose a watermarking method that is robust to geometric distortions. In order to resist geometric distortions, we use a local invariant feature of the image called the scale-invariant feature transform ͑SIFT͒, which is invariant to translation and scaling distortions. The watermark is inserted into the circular patches generated by the SIFT. Rotation invariance is achieved using the translation property of the polar-mapped circular patches. Our method belongs to the blind watermark, because we do not need the original image during detection. We have performed an intensive simulation to show the robustness of the proposed method. The simulation results support the contention that our method is robust against geometric distortion attacks as well as signal-processing attacks. We have compared our results with those of other methods, and our method outperforms them.

We propose adaptive anomaly detectors that find materials whose spectral characteristics are substantially different from those of the neighboring materials. Target spectral vectors are assumed to have different statistical characteristics from the background vectors. We use a dual rectangular window that separates the local area into two regions-the inner window region (IWR) and outer window region (OWR). The statistical spectral differences between the IWR and OWR is exploited by generating subspace projection vectors onto which the IWR and OWR vectors are projected. Anomalies are detected if the projection separation between the IWR and OWR vectors is greater than a predefined threshold. Four different methods are used to produce the subspace projection vectors. The four proposed anomaly detectors have been applied to HYDICE images and the detection performance for each method has been evaluated.

We have proposed and demonstrated a novel radio-overfiber (ROF) architecture by using only one phase modulator and one optical filter to generate DWDM optical millimeter (mm) signals and realize wavelength reuse for upstream data connection. There is no additional laser source for the upstream data generation in the base station and no dc-bias controller for phase modulator. By this method, we simplify the configuration of the DWDM ROF system and reduce the cost of the system. Figure 5 BER curves for both down-link and up-link data.

We propose and experimentally verify a scheme to engineer arbitrary states of traveling light field up to the two-photon level. The desired state is remotely prepared in the signal channel of spontaneous parametric down-conversion by means of conditional measurements on ...

An iterative method is introduced for determining the exposure schedule for multiplexing holograms in saturable recording materials, such as photopolymers. This method is designed to share all or part of the available dynamic range of the recording material among the holograms to be multiplexed. Using exposure schedules derived from this method, the authors find that the diffraction efficiency of DuPont's HRF-150 38-and 100-m photopolymer scale is (2.2/M) 2 and (6.5/M) 2 respectively, where M is the number of holograms recorded. Finally, 1000 holograms were multiplexed at a single location in the 100-m thick photopolymer using an exposure schedule derived with this method.

Restoration for actual atmospherically blurred images is performed using an atmospheric Wiener filter that corrects simultaneously for both turbulence and aerosol blur by enhancing the image spectrum primarily at those high frequencies least affected by the jitter or randomness in a turbulence modulation transfer function (MTF). The correction is based on weather-predicted rather than measured atmospheric MTFs. Both turbulence and aerosol MTFs are predicted using meteorological parameters measured with standard weather stations at the time and location where the image was recorded. A variety of weather conditions and seasons are considered. Past results have shown good correlation between measured and predicted atmospheric MTFs. Here, the predicted MTFs are implemented in actual image restoration and quantitative analysis of the MTF improvement is presented. Corrections are shown also for turbulence blur alone, for aerosol blur alone, and for both together.

A method to perform a predictive search for a given amplitude and phase modulation response in twisted nematic liquid crystal displays is presented. The algorithm is based on a simple physical model that we recently proposed and that considers the effect of liquid crystal layers located in the vicinity of the edges, which are not capable to tilt. This model was demonstrated to explain accurately the experimental transmittance modulation curves. Here the model is applied to perform a predictive search for an optimized modulation by changing the input and output polarization configuration. A generalized configuration to generate and detect elliptically polarized light is proposed. The method is applied for searching two different configurations useful for optical image processors: phase-only modulation and amplitude-only modulation. The excellent agreement with the experimental measurements validates the potentiality of the proposed method.

The continuing development of new and fundamentally different classes of imaging spectrometers has increased the complexity of the field of imaging spectrometry. The rapid pace at which new terminology is introduced to describe the new types of imaging spectrometers sometimes leads to confusion, particularly in discussions of the relative merits of the different types. In some cases, multiple different terms are commonly used to describe the same fundamental approach, and it is not always clear when these terms are synonymous. Other terminology in common use is overly broad. When a single term may encompass instruments that operate in fundamentally different ways, important distinctions may be obscured. In the interest of clarifying the terminology used in imaging spectrometry, we present a comprehensive system for classification of imaging spectrometers based on two fundamental properties: the method by which they scan the object spatially, and the method by which they obtain spectral information. © 2005 Society of Photo-Optical Instrumentation Engineers.

With the rapidly increasing aggregate bandwidth requirements of data centers there is a growing interest in the insertion of optically interconnected networks with high-radix transparent optical switch fabrics. Silicon photonics is a particularly promising and applicable technology due to its small footprint, CMOS compatibility, high bandwidth density, and the potential for nanosecond scale dynamic connectivity. In this paper we analyze the feasibility of building silicon photonic microring based switch fabrics for data center scale optical interconnection networks. We evaluate the scalability of a microring based switch fabric for WDM signals. Critical parameters including crosstalk, insertion loss and switching speed are analyzed, and their sensitivity with respect to device parameters is examined. We show that optimization of physical layer parameters can reduce crosstalk and increase switch fabric scalability. Our analysis indicates that with current state-of-the-art devices, a high radix 128×128 silicon photonic single chip switch fabric with tolerable power penalty is feasible.  The applicability of silicon photonic microrings for data center switching is further supported via review of microring operations and control demonstrations. The challenges and opportunities for this technology platform are discussed.

We examine some fundamental theoretical limits on the ability of practical digital holography ͑DH͒ systems to resolve detail in an image. Unlike conventional diffraction-limited imaging systems, where a projected image of the limiting aperture is used to define the system performance, there are at least three major effects that determine the performance of a DH system: ͑i͒ The spacing between adjacent pixels on the CCD, ͑ii͒ an averaging effect introduced by the finite size of these pixels, and ͑iii͒ the finite extent of the camera face itself. Using a theoretical model, we define a single expression that accounts for all these physical effects. With this model, we explore several different DH recording techniques: off-axis and inline, considering both the dc terms, as well as the real and twin images that are features of the holographic recording process. Our analysis shows that the imaging operation is shift variant and we demonstrate this using a simple example. We examine how our theoretical model can be used to optimize CCD design for lensless DH capture. We present a series of experimental results to confirm the validity of our theoretical model, demonstrating recovery of super-Nyquist frequencies for the first time. © 2009 Society of Photo-Optical Instrumentation Engineers.

The work done to provide images sensors (CCDs and CMOS) with a wide dynamic range is reviewed. The different classes of solutions, which consist of logarithmic sensors, `clipped&#x27; sensors, multimode sensors, frequency-based sensors, and sensors with control over integration time are described. The pros and cons of each solution are discussed, and some new experimental results are shown. Active pixel

All-optical networking can be the sole approach to provide the huge bandwidth required for future networks. The essential elements in such an optical network are optical switches. A number of options have been proposed in order to implement them efficiently. We focus on thermooptical switches. First, the physical principles of the thermo-optic effect are briefly introduced. A description of the most common technologies used for the fabrication of thermo-optic switches is provided along with the values of thermo-optic coefficient for a number of materials. The main steps useful in order to design thermo-optical switches are also briefly introduced. Finally, a bird's-eye view of the main and recent proposals of switches based on the thermo-optic effect is reported and their performances compared. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

Soft X-ray tomography (SXT) is becoming a powerful imaging technique to analyze eukaryotic whole cells close to their native state. Central to the analysis of the quality of SXT 3D reconstruction is the estimation of the spatial resolution and Depth of Field of the X-ray microscope. In turn, the characterization of the Modulation Transfer Function (MTF) of the optical system is key to calculate both parameters. Consequently, in this work we introduce a fully automated technique to accurately estimate the transfer function of such an optical system. Our proposal is based on the preprocessing of the experimental images to obtain an estimate of the input pattern, followed by the analysis in Fourier space of multiple orders of a Siemens Star test sample, extending in this way its measured frequency range.

It has been a challenge to finish optical glass surface due to their hard and brittle nature. Moreover tight tolerances of surface figure and finish make polishing a more critical operation. This work reports the results of an experimental study performed for full aperture polishing of BK7 optical glass. Flat samples of BK7 glass are polished using optical pitch polisher and cerium oxide slurry. Taguchi’s L9 orthogonal array is used for design of experiments. Abrasive concentration, pressure and overarm speed are taken as variable process parameters. Polishing is performed for duration of 120 minutes for each combination of parameters. Material removal is measured using the precision weighing balance. Surface roughness was measured using Form Talysurf PGI 120 profiler. Abrasive slurry concentration is observed to be one of the most significant parameters in optical polishing process. It affects material removal rate as well as surface roughness. Pressure applied at workpiece-polisher interface affects material removal rate but variation of pressure is not found to affect surface roughness significantly. Relative motion at workpiece-polisher interface is also observed to be significant in defining final polishing outputs.

The tutorial describes essential features of moiré patterns, as well as the circumstances, when the moiré patterns appear and how to estimate their characteristics (parameters) such as the orientation and period. The moiré effect is described in two domains, the image space (spatial domain) and in the spectral domain using the complex numbers. The tutorial covers the indicial equation method, the coplanar and noncoplanar sinusoidal gratings, the moiré effect in a spatial object (a cylinder), as well as explains the moiré wave vector, the moiré spectra, the spectral trajectories, and summarizes behavior of the visible patterns in moved/rotated gratings. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.