This PDF file contains the editorial “Disappearing City Stories” for OE Vol. 48 Issue 07

Experimental results about efficient band-edge light coupling into two-dimensional planar photonic crystals by the use of a gradual interface are reported. It is shown that a chirp of both the lattice period and the hole diameter on short lengths below 3 μm allows maintaining high optical transmission spectra close to the band-gap frequency where strongly dispersive phenomena can be exploited. If compared with nonoptimized structures, increased optical levels by 15 to 20 dB are obtained using gradual tapering stages.

The purpose of this study was to develop a mathematical model that could be used to obtain the approximate focal length of O-ring-driven liquid-filled lenses. An O-ring-driven liquid-filled lens is composed of a base plate, a glass-covered liquid reservoir, a pliable membrane, an O-ring, a spring, and three actuators. The movement of the ring changes the focal length or the focus position. In previous studies, the commercial software ANSYS was used to find the membrane deformation and ZEMAX was used to find the focal length. The procedures used in those previous studies are complicated and generally require considerable design work. The proposed mathematical method employs the principle of liquid volume conservation to simplify the calculations that approximate the focal length of the lens. The result is confirmed on ZEMAX to ensure that the method is practicable. Consequently, focal lengths of lenses with different ring thicknesses, radii, and squeezing depths to contact the membrane can be calculated immediately.

A novel technique was proposed to fabricate a three-dimensional photonic crystal by self-assembling microspheres and the autocloning technology. The autocloning thin-film layers were superimposed on the prepared two-dimensional structural substrates using self-assembled microspheres. The thin-film process allows the three-dimensional periodic structure to be easily modified in the thickness dimension to structure as needed. We analyzed the etching effect using the unified process model according to the surface movement and surface velocity of the film to achieve the surface profile of the SiO₂ adjusting layer. Finally, 17 layers of Ta₂O₅/SiO₂ multilayers were stacked on the SiO₂ adjusting layer successfully.

We report on a high-precision, real-time photon beam localization and characterization instrument. The device uses a 2-D (image) sensor coupled to a hardware image processing system. The system uses two different algorithms that both run in parallel on field programmable gate array logic using data from a single active pixel array sensor. The first algorithm mimics the ubiquitous quadrant photodiode design that features high precision but has limited range and requires calibration cycles. The second algorithm calculates the location of the center of gravity. We compare the merits of both methods by measuring the displacement of a light beam. It is shown that the center of gravity (or centroid) method offers the advantage of large dynamic range with excellent linearity. By the method of operating on identical image data captured from these experiments, we aim to investigate both algorithms and compare their performance.

Two important aspects of surface engineering are measurement and analysis. While the acquisition of 3-D surface data is largely improved by optical profilometry, there has also been much research about their evaluation. Although the fractal-based or multiscale analysis of surface roughness is well known, these methods are not tailored for the characterization of the roughness of important machined surface textures produced by turning, grinding, honing, etc. In this work, a multiscale model of rough groove textures for 3-D surface measurements is introduced. Under the assumption of fractal groove profiles, the groove textures are modeled as superpositions of orthogonal ridge functions by the ridgelet packet transform. This provides a compact representation of groove textures. This allows a restoration of roughness components from accurate optical measurements, so that precise characterization can be achieved based on restoration. This method is validated for restoration of honing textures for real optical surface measurements on a cylinder liner.

Interferometric surface profilers using a single wavelength offer excellent vertical resolution, but have an ambiguity-free range of less than half a wavelength. Multiple-wavelength or white light interference techniques are used to overcome the problem. We discuss a three-wavelength interferometric technique used with a phase-shifting phase evaluation procedure. The phase evaluation at the three wavelengths gives wrapped phase at any pixel corresponding to these wavelengths. We use the fact that the variation of phase with wavenumber for a given profile height is linear to determine the absolute value of the profile height. The height is then used to ascertain the fringe order. The fringe order, along with the wrapped phase, gives the profile height with a resolution given by the phase-shifting technique. Experimental results for large step height measurement on etched silicon samples are presented.

Most 3-D shape measurements for a dynamic object always require that the obtained images not be blurred by motion. We show that it is not necessary to avoid the blurred image when projected fringe profilometry is employed. For objects that move within one period of the projected fringes, 3-D surfaces can be retrieved directly from the blurred fringes. Consequently, the presented method intensively reduces the cost of the detection system.

A technology for establishing best focus of an optical system is described. This technology was recently used to establish best focus of the Orbiting Carbon Observatory spectrometers while the instrument was undergoing thermal-vacuum testing. Three piezo-actuated motors were used to adjust the tip, tilt, and piston of a focal plane assembly relative to the spectrometer's optical system. A set of optical displacement sensors measured tip-tilt-piston throughout the focusing process. With best focus established and confirmed using a pupil-slicing technique, the corresponding sensor measurements were used to specify the geometry and dimensions of a precision-ground shim ring.

We have employed ink-jet printing (IJP) technology to fabricate self-positioning microlens arrays (MLAs). The glass substrates were first prepatterned through microcontact printing (μCP) hydrophobic self-assembled monolayers (SAMs) to divide the surface into hydrophobic and hydrophilic regions. After IJP of the hydrophilic prepolymer liquids, the lenses were effectively repelled by the patterned SAMs. We obtained high-quality MLAs having diameters of 75 and 100 μm after polymerization of the prepolymers. The lenses' shapes could be controlled by varying the number of printed droplets.

Laser beam angular scan accuracy measurement plays an important role in many fields. A sub-microradian laser beam scan precision measurement method that utilizes the wavefront interference method with a Zygo interferometer is proposed. The experimental results show that the measurement accuracy is approximately 0.04 μrad, and the new method is very effective and feasible.

A crossed-cosine spatial filter suitable for Lyot coronagraphy is presented. With respect to other proposed designs, this filter presents the advantage of being usable for low-order wavefront sensing. Wavefront measurement accuracies were simulated numerically and found to be better than λ/10 peak-to-valley and λ/100 root mean square, which is a performance comparable to the best currently available wavefront measuring techniques. The crossed-cosine filter could be integrated into a cascaded coronagraph, either spaceborne or ground-based, of which it would constitute the first stage.

We describe the wavefront measurement interferometry technologies suitable for microlenses. It is common for microlenses to exhibit large aberrations and microlens arrays can introduce additional negative effects from the array when the wavefront aberration is measured. In the case of a microlens array, stray light may be generated by the rest of the microlenses during measurement. A single-pass interferometer, such as the Mach-Zehnder interferometer, is a good solution. It is sometimes difficult to maintain a conjugate condition due to large aberrations when a double-pass interferometer, such as a Fizeau interferometer, is used. Interferometers usually use a software aperture to define the calculation area for wavefront aberration measurement. But we determine the effectiveness of the hardware aperture in reducing the noise in the interferometer optics compared to the use of the software aperture. The result of a theoretical investigation shows the effects of the hardware, and the software apertures are almost the same. An experimental investigation is also made using a Mach-Zehnder interferometer with both hardware and software apertures. The hardware aperture is inserted into the interferometer optics and is projected to reduce the effective size of aperture on the pupil of the microlens to avoid the Fresnel diffraction. Finally, the theoretical and experimental results show good correspondence. We show the necessity of the wavefront aberration measurement interferometer technologies for microlenses.

We propose a new technique to extract the steadystate capacitance-voltage (C-V) characteristics of an active-matrix liquid crystal display (AMLCD) using its transient luminance responses. We show how to determine the capacitance of pixels in an AMLCD using the charge conservation law in a pixel and the one-to-one relation between the luminance and capacitance of LC molecules. The C-V data extracted at the ends of the first and second frame times match very well with each other, which confirms that our technique is valid. By using the extracted C-V data, we calculate overdrive voltage values according to transitions. The results show that the overdrive voltages have a linear relation with the transition voltage difference. The linear characteristics can help the overdrive hardware to be extremely simple. The ease of implementation of the overdrive technology with the linear voltage relation should facilitate further adoption and expansion of LCD products with faster response times.

By using a reflective-type semiconductor saturable absorber mirror (SESAM), we design a laser cavity to obtain a single mode-locked laser output beam. To our knowledge, this is the first report of a Nd:GdVO₄ laser attaining a single mode-locked output beam with a reflective SESAM using this cavity design. A mode-locked average output power of 3.027 W is attained at a pump power of 10.07 W, with pulse duration 7.6 ps and repetition rate 90 MHz. In the actual applications, the single output laser can make full use of the output laser with nearly twice the efficiency of pump power, in comparison with lasers having two output laser beams. Thus, this laser has great promise in other applications.

We investigate fabrication of functional conductive carbon paste onto a plastic substrate using a laser. The method allows simultaneous sintering, patterning, and functionalization of the carbon paste. Experiments are carried out to optimize the laser-processing parameters. It is shown that sheet resistance values obtained by laser sintering are close to the one specified by the manufacturer using the conventional sintering method. Additionally, a heat transfer analysis using numerical methods is conducted to understand the relationship between the temperature during sintering and the sheet resistance values of sintered carbon wires. The process developed has the potential of producing carbon-based electronic components on low-cost plastic substrates.

A three-power-level method for obtaining efficient thermo-optical modulation in an all-silicon waveguide-integrated Fabry-Perot thermo-optic modulator is discussed by means of a thermo-optical analytical model and demonstrated. The thermal system is represented as a two-pole model where, at every time, the temperature in the waveguide core is modified by means of a heater. This temperature is calculated and used in turn for calculating the refractive index. In this way, the impact of the driving signal shape on the device speed performance is assessed. Results clearly indicate that the application of a thermal bias holding the modulator at a higher average temperature with respect to the substrate heat sink allows increasing the modulator speed. An application-specific integrated circuit has been designed and developed in order to test the new modulation logic. The system's electronics is implemented in a 0.8 μm, 5 V, CMOS process. The experimental results of this new three-power-level driver method are reported, showing the shortening of the characteristic transient times.

We propose a novel system of broadband source generation using a common soliton pulse (i.e., with center wavelength at 1.55 μm) propagating within a nonlinear micro-ring resonator system. The system consists of a micro-ring resonator system incorporating an add/drop filter, whereby the large-bandwidth signals can be generated, stored, and regenerated within the system. By using the appropriate parameters relating to the practical device such as micro-ring radii, coupling coefficients, and linear and nonlinear refractive index, we found that the obtained multisoliton pulses have shown the potential of application for dense wavelength-division multiplexing (DWDM), whereby the different center wavelengths of the soliton bands can be obtained via the add/drop filter, which can be used to increase the communication channel capacity in the communication network. The best free spectra range (FSR) and FWHM of the results obtained are 14 nm and 100 pm, respectively, which allows an increase in channel capacity of at least 10 times in only one center wavelength.

We first demonstrate that by inserting an appropriate section of unpumped erbium-doped fiber (EDF) in an erbium-doped superfluorescent fiber source (SFS) of double-pass backward configuration, a stable L-band SFS can be achieved. The fiber-length arrangement of unpumped fiber are shown to have significant effects on the output properties of the L-band SFS. The spectral linewidth is broadened, and the variation of mean wavelength versus pump power is eliminated to achieve a wideband and mean wavelength stable L-band SFS by optimizing the fiber-length ratio of the pumped fiber length to the total fiber length. For a 19-m-long total EDF with fiber-length ratio of 0.84, a mean wavelength stable L-band SFS with a spectral linewidth of 49.6 nm, an output power of 46.3 mW, and a mean wavelength of 1583.20 nm was experimentally achieved.

Simultaneous wired and wireless link services in a novel optical line terminal for orthogonal frequency-division multiplexing (OFDM)-wavelength-division-multiplexed passive optical network compatible with radio-over-fiber system is proposed and experimentally demonstrated. In the optical line terminal, optical carrier suppression modulation scheme is used to generate a 40-GHz optical millimeter-wave (mm-wave). 2.5-Gb/s OFDM signal is carried by the 40-GHz optical mm-wave. In the base station, we can provide simultaneous wired and wireless services. The downstream OFDM lightwave can be reused to carry 2.5-Gb/s on-off Keying nonreturn-to-zero (OOK-NRZ) upstream data without erasure of the downstream data.

Frequency-domain optical coherence tomography (FD-OCT) has the advantages of an improved sensitivity and a reduced acquisition time since it enables cross-sectional images of the sample of interest to be obtained using a broadband source or a swept source. The phase-shifting method can always be applied to reduce the additional noise within FD-OCT and provide accurate signal processing. We present a phase-shifting method in which a parallel diffraction grating pair is inserted into the reference arm of the OCT system. The gratings separate the spectrum of the illuminating light and stretch the optical pulse in time thereby producing a linear group delay between the adjacent wavelengths in the superluminescent diode light source. The simulation results show that the proposed group-delay-based phase-shifting method improves the precision of the sample parameters extracted using the FD-OCT procedure compared to those obtained using traditional techniques such as the λ0/4 phase-shifting method.

Based on a finite-conjugate objective lens with numerical aperture of 0.62 for a 650-nm wavelength, an optical pickup head composed of a multifunction beamsplitter and a diffractive optical element is designed be used in a swing-arm-type optical pickup head. The diffractive optical element is a lens with an elliptical four-level phase profile to provide both focusing and astigmatism. It is also designed with the goal to simplify the overall optical configuration and provide linear characteristics for the focus error signal.

A nonlinear material-based all-optical switching mechanism is utilized here to realize the J-K and J-K master-slave (J-K M-S) flip-flops. As the flip-flops are sequential logic circuits, the present states of outputs are dependent not only on the present inputs but also on the past outputs. In our present scheme, the outputs are fed back to the former stages as well as the input stages. The output of each flip-flop and its complement are obtained simultaneously in our scheme.

A liquid crystal panel for a video projector is often used for holographic television. However, its pixel size and pixel number are not enough for practical holographic 3-D display. Therefore, a multipanel configuration is generally used to increase the viewing window and displayed image size, and many spatial light modulators should be used in them. We propose a novel method to increase the viewing window of a holographic display system. The proposed method, which is implemented by using a mirror module and 4-f lens set, is to reconfigure the beam shape reflected by a spatial light modulator. The equipment is applied to a holographic display system, which has only a single spatial light modulator; a hologram could be displayed in a wider viewing window by the equipment than that of the conventional method. By the proposed method, the resolution of the reconfigured spatial light modulator has double resolution in the horizontal direction. Inversely, the vertical resolution is decreased. Even if the vertical resolution is decreased, a viewer could get 3-D effect because humans get more 3-D information in the horizontal direction. We have experimented using a liquid crystal on silicon (LcOS), whose resolution is 4096×2160 pixels. The reconfigured resolution by the mirror module is 8192×1080 pixels. From the experiments, the horizontal viewing window is almost two times wider than that without the mirror module. As a result, the hologram can be observed binocularly.

We describe a model to predict the minimum resolvable temperature (MRT) performance of thermal imagers. Although MRT is a common measurement, it is difficult to achieve consistent results. The operator is permitted but not mandated to change gain, level, and sample phasing for each bar pattern viewed. Changing the sensor control settings affects the resulting MRT. However, the state of the imager is not recorded along with the temperature data. The model predicts the effect of gain, level, and sample phase on MRT results. Model predictions are compared to measurements to demonstrate theory validity. The comparisons also demonstrate the variability that results from ignoring the sensor state when reporting MRT.

A high-order statistical-based, blind deconvolution algorithm is proposed for x-ray powder diffraction profiles. Maximizing the kurtosis amplitude of the deconvolved data ensures that only the data with maximized kurtosis amplitude is extracted. The ill-posed nature of deconvolution is, thus, bypassed. Using simulation and experiments, this method is seen to be very robust with respect to noise. The profile resolution is enhanced considerably, and the deconvolved profile fits the pseudo-Voigt profile nicely. However, noise is enhanced in the deconvolved data, so the algorithm may be invalid for experimental data with low signal-to-noise.

An energy-discriminating x-ray camera is useful for performing monochromatic radiography using polychromatic x rays. This x-ray camera was developed to carry out K-edge radiography using iodine-based contrast media. In this camera, objects are exposed by a cone beam from a cerium x-ray generator, and penetrating x-ray photons are detected by a cadmium telluride detector with an amplifier unit. The optimal x-ray photon energy and the energy width are selected out using a multichannel analyzer, and the photon number is counted by a counter card. Radiography was performed by the detector scanning using an x-y stage driven by a two-stage controller, and radiograms obtained by energy discriminating are shown on a personal computer monitor. In radiography, the tube voltage and current were 60 kV and 36 μA, respectively, and the x-ray intensity was 4.7 μGy/s. Cerium K-series characteristic x rays are absorbed effectively by iodine-based contrast media, and iodine K-edge radiography was performed using x rays with energies just beyond iodine K-edge energy 33.2 keV.

A cellular neural network (CNN)-based moving object segmentation algorithm in the H.264 compressed domain is proposed. This algorithm mainly utilizes motion vectors directly extracted from H.264 bitstreams. To improve the robustness of the motion vector information, the intramodes in I-frames are used for smooth and nonsmooth region classification, and the residual coefficient energy of P-frames is used to update the classification results first. Then, an adaptive motion vector filter is used according to interpartition modes. Finally, many CNN models are applied to implement moving object segmentation based on motion vector fields. Experiment results are presented to verify the efficiency and the robustness of this algorithm.

Gaze tracking technology is a convenient interfacing method for mobile devices. Most previous studies used a large-sized desktop or head-mounted display. In this study, we propose a novel gaze tracking method using an active appearance model (AAM) and multiple support vector regression (SVR) on a mobile device. Our research has four main contributions. First, in calculating the gaze position, the amount of facial rotation and translation based on four feature values is computed using facial feature points detected by AAM. Second, the amount of eye rotation based on two feature values is computed for measuring eye gaze position. Third, to compensate for the fitting error of an AAM in facial rotation, we use the adaptive discrete Kalman filter (DKF), which applies a different velocity of state transition matrix to the facial feature points. Fourth, we obtain gaze position on a mobile device based on multiple SVR by separating the rotation and translation of face and eye rotation. Experimental results show that the root mean square (rms) gaze error is 36.94 pixels on the 4.5-in. screen of a mobile device with a screen resolution of 800×600 pixels.

Time-of-flight range sensors with on-chip continuous-wave correlation of radio frequency-modulated signals are increasingly popular. They simultaneously deliver depth maps and intensity images with noise and systematic errors that are unique for this particular kind of data. Based on recent theoretical findings on the dominating noise processes, we propose specific variants of normalized convolution and median filtering, both adaptive and nonadaptive, to the denoising of the range images. We examine the proposed filters on real-world depth maps with varying reflectivity, structure, overexposure, and illumination. The best results are obtained by adaptive filters that locally adjust the level of smoothing using the estimated modulation amplitude as a measure of confidence.

We present an image fusion method for determining optical length in radiography of dense objects. We first show that the scatter received in the screen-films (SFs) can be treated as a constant when a grade collimation is arranged properly in the radiographic image system. Then the nonlinear radiographic imaging process can be demonstrated by a monotonous nonlinear function, which is determined by the whole system. The optical length of the fused image is derived from a weighted sum of the optical length conversed from the single image directly, and the weight of the optical length is determined by the greatest derivation of the function. Experiment results show that the algorithm has improved the signal-to-noise ratio (SNR) of the fused image and extended the dynamic range of the receivers.

Superresolution reconstruction produces a high-resolution image from a set of low-resolution images. Accurate subpixel image registration is critical in image superresolution reconstruction. The existence of outliers, which are defined as data points with different distributional characteristics from the assumed model, will produce erroneous image registration estimates that lead to undesirable results. Several solutions have been proposed to handle registration errors as a part of the regularized solution in the reconstruction step; however, they are invalid for videos that contain localized outliers, such as moving objects in the frames. We present a new robust image superresolution method to handle the localized motion outliers. We first separate the low-resolution image into several layers. After identifying the motion models of the layers, we calculate these separately. Then, we can obtain an accurate subpixel image registration of the background that contains important information. Finally, we fuse them into a high-resolution image. The effectiveness of our model is demonstrated with results from superresolution experiments with both synthetic and real sequences in the presence of localized motion outliers.

The jigsaw puzzle has been popular from past to present, and there are many jigsaw puzzle images on the Internet. This paper proposes a novel method to hide secret data in jigsaw puzzle images. First, a digital image is taken as input and divided into blocks. Then, a semicircle is drawn and attached to the right and bottom sides of each block. The secret data are embedded through the attached positions and orientations of the semicircles according to a stegokey. The resulting image looks like those jigsaw puzzle images appearing on many jigsaw puzzle Web sites. Experiments show that the proposed method is undetectable under the passive warden and robust to format conversion, lossy compression, and lossy recompression.

We describe a new algorithm to construct pseudo-3-D videos out of conventional 2-D videos at the viewing end, where no additional 3-D information is attached at the source of 2-D video production. We name such constructed videos pseudo-3-D on the grounds that the converted video is not true 3-D but presents a perceptual 3-D effect when viewed with a pair of polarized glasses. The proposed algorithm consists of two video processing stages: (1) semantic video object segmentation; and (2) estimation of disparities. In the first stage, we propose a constrained region-growing and filtering approach to improve existing segmentation techniques based on change detections. Such a processing stage ensures that disparities are estimated in terms of semantic video objects rather than textured regions, and thus improve the pseudo-3-D effect in terms of human visual perception. In the second stage, we propose a video object (VO)-size-based disparity estimation to construct additional video frames for the proposed pseudo-3-D video conversion. Experiments carried out demonstrate that the proposed algorithm effectively produces perceptually harmonious pseudo-3-D videos with the advantages of simplicity and low computing cost.

Thien and Lin [Comput. and Graphics 26(5), 765-770 (2002)] proposed a threshold scheme to share a secret image among n shadows: any t of the n shadows can recover the secret, whereas t-1 or fewer shadows cannot. However, in real life, certain managers probably play key roles to run a company and thus need special authority to recover the secret in managers' meeting. (Each manager's shadow should be more powerful than an ordinary employee's shadow.) In Thien and Lin's scheme, if a company has less than t managers, then manager's meeting cannot recover the secret, unless some managers were given multiple shadows in advance. But this compromise causes managers inconvenience because too many shadows were to be kept daily and carried to the meeting. To solve this dilemma, a weighted sharing method is proposed: each of the shadows has a weight. The secret is recovered if and only if the total weights (rather than the number) of received shadows is at least t. The properties of GF(2^r) are utilized to accelerate sharing speed. Besides, the method is also a more general approach to polynomial-based sharing. Moreover, for convenience, each person keeps only one shadow and only one shadow index.

We propose an asymmetric-resolution stereoscopic video codec that can be used for commercially available stereo displays. Currently, most stereo video displays are designed for displaying not only stereo video but also conventional single-view video in order to make them compatible to single-view video services. In these systems, the resolution of each input video for stereo mode is half the input resolution for a single-view mode. We propose a stereoscopic video codec to support both single-view and stereo-view services by encoding full-resolution left images and horizontally downsampled right images. However, it is not possible to employ the conventional disparity estimation between the two views because the resolution of the left image is different from that of the corresponding right image. So we propose a stereoscopic video codec based on a new disparity estimation/compensation method that makes use of all the information of the left reference image without downsampling. We achieved a 0.5- to 0.8-dB coding gain with the proposed stereoscopic codec, compared with several conventional stereoscopic coding algorithms.

Creating a visual codebook is an important problem in object recognition. Using a compact visual codebook can boost computational efficiency and reduce memory cost. A simple and effective method is proposed for visual feature codebook construction. On the basis of a feedforward hierarchical model, a robust local descriptor is proposed and an a priori statistical scheme is applied to the class-specific feature-learning stage. The experiments show that the proposed approach achieves reliable performance with shorter codebook length, and incremental learning can be easily enabled.

To findout how many clusters exist in a sample set is an old yet unsolved problem in unsupervised clustering. This problem inevitably occurs in region merging/growing, a well studied and popular technique in image segmentation. Region merging usually needs a stop criterion. The stop criterion is not automatically determined and often has to be set manually to arrive at a sensible segmentation, which is rather difficult for natural images. To address this problem, we present a robust stop criterion that is based on a novel distinctness predicate for adjacent regions. The predicate discerns distinct regions by examining the evidence of the boundary between neighboring regions. Requiring that every region should be distinct from each other, the proposed method is able to choose a stop point where a natural partition is most likely. Under a region merging framework, we demonstrate the effectiveness of the stop criterion using two merging criterion: one based on optimizing a global functional, and another based on a local criterion. Experimental results and comparison are given at the end.

A set of laser beam shaping optics is designed by an iterative method using an adaptive additive algorithm to transform a Gaussian beam into a pitchfork beam. Two diffractive optical elements are designed based on Fresnel diffraction to reduce the amount of energy in the first-order diffraction ring and to increase the depth of focus for the optical system. These two beam properties are found to depend on the diameter of the desired beam and the Airy disk diameter. If the diameter of the desired beam is large, then the optical system yields better results in achieving the above-mentioned two beam properties. The performance of the diffractive optical elements is compared to a previous laser beam shaping system designed by the ray-tracing technique. A pinhole scanning power meter is used to measure the laser irradiance profile at the focal plane to verify the existence of the pitchfork beam. The irradiance profile measurement shows that diffractive optical elements allow better control for reducing the amount of energy in the diffraction side lobes.