This PDF file contains the editorial “Beyond Print” for OE Vol. 46 Issue 07

To achieve the full complex modulated range of the cascaded twisted nematic liquid crystal spatial light modulator (TNLC-SLM), we propose and demonstrate a novel amplitude compensated technique. Optical reconstructions of complex digital holograms with higher image quality are discussed in both analytical and experimental results.

Ultrawide-band microwave amplification in the optical domain is proposed that covers the frequency range from 10 MHz to 10 GHz with over 10 dB gain. A partly carrier-suppressed optically carried microwave signal is generated and amplified by erbium-doped fiber amplifier (EDFA) in this scheme.

A simple method is found to align multielement cylindrical lenses. The method employs only equipment found in most optical shops: a precision flat mirror and a Fizeau interferometer. A combination of narrow reflection interferograms from the lens surfaces, combined with cat-eye double-pass interferograms, is employed to align the elements.

The design and performance test of a cholesteric liquid crystal depolarizer (CLCD) is presented. This new depolarizer is a wedge-shaped cell filled with cholesteric liquid crystal material. By placing a CLCD in its path, the incident light beam is divided into a great number of micro beams in space, and each micro light beam has different polarization state and orientation, hence achieving the depolarization effect. Over a conventional optical depolarizer, the CLCD is easy built and insensitive to the polarization orientation of incident light.

This paper tackles the problem of quadric mirror estimation for omnidirectional imaging systems, as well as the poses of the camera relative to the mirror and to the world reference system. These estimates are obtained for quadric-shaped mirrors (including elliptic, parabolic, hyperbolic, and spherical mirrors) where the positions of the camera and mirror are unconstrained (fully noncentral configurations). The apparent contour of the mirror can be used to reduce the uncertainty in the estimation. Although it can enhance both the accuracy of the estimation (allowing the method to converge from farther initial configurations) and also its performance, its use is not strictly required. The intrinsic parameters of the camera model (pinhole or orthographic) are assumed to be known, as well as the structure of a calibration object in local coordinates. The method is nonlinear, and we use a genetic algorithm in conjunction with the Nelder-Mead simplex algorithm to minimize the objective function. Experimental results using real data are presented, demonstrating the accuracy of this calibration method, comparing its accuracy with and without the apparent contour, and computing its reprojection error. Because the mirror quadric is estimated, this method can also be used to identify and classify the mirror.

This paper deals with a novel approach for achieving real-time surface recognition. The aim of this study is to detect different kinds of surfaces using a phase-shift range finder and a neural network (NN). The NN architecture is a multilayer perceptron with two inputs, three processing neurons in the hidden layer, and one output neuron. The first and the second inputs receive respectively the amplified and filtered photoelectric signal and the range finder output signal. The NN output is compared with threshold voltages in order to classify the tested surfaces. This recognition system has been studied with data from experimental measurements, achieved with four kinds of surfaces (a plastic surface, a glossy paper, a painted wall, and a porous surface), at a remote distance between the range finder and the target varying from 0.5 to 2 m and with a laser beam incidence angle with respect to the target varying between -π5 and π/5.

Advances in digital image optics have increased the significance of lateral color aberration because it is easily seen in the projected area. The choice of optical glass plays a role in the elimination of lateral color aberration. Current optical software still has difficulty in finding the optimal combination of optical glasses for twelve or more elements in a projection lens, the choice being among at least 300 optical glasses that have been developed. Even the modern damped least squares, a ray-tracing-based method, is limited, owing to its inability to identify an enhanced optical system configuration. As an alternative, this research proposes a new optimization process by using algorithms involving the theory of geometric optics in a projector lens, real encoding, multiple dynamic crossover, and random gene mutation techniques. Results and conclusions show that attempts to achieve negligible axial and lateral color aberration are successful.

In an Offner spectrometer, unlike other spectrometers, the dispersion need not be in the plane of the instrument (defined as the plane that includes the mirror vertices and the center of the entrance slit). If the entrance slit is short, better performance can be obtained when the dispersion is perpendicular to this plane. The reasons for this are briefly discussed, and design examples given.

Propagation along an optical fiber modifies the spectrum of an ultrashort laser pulse due to interaction of the pulse with the fiber nonlinearity. These spectral modifications can be correlated with the input pulse parameters like the pulse power, pulse width, chirp, and pulse shape. We have shown earlier by numerical calculation that a small change in any of the pulse parameters is magnified in the fiber-modified spectrum due to the nonlinear nature of the interaction. We had proposed a differential spectrum monitoring technique for detecting such small changes. We now show experimentally that this technique can provide a sensitive and practical method for monitoring small changes in ultrashort pulses. Thus it can serve as a practical on-line monitor for laser stability during experiments with ultrashort pulses.

Coherent interferometric absolute distance metrology is one of the most interesting techniques for length metrology. Without movement, measurements are made without ambiguity, by using either one or several synthetic wavelengths resulting from the beating of two or more wavelengths (multiple-wavelength interferometry), or a frequency sweep (frequency-sweeping interferometry). Sensors based on the latter are relatively simple devices and can fulfill an important role in dimensional metrology. In addition, their parameterization flexibility allows trade-offs to be performed, either technology-driven or application-related. We present in detail a theoretical model of frequency-sweeping interferometry and its uncertainty budget, discuss different parameterizations, present a method for drift error compensation, and demonstrate and evaluate sensor performance and robustness with a prototype sensor composed of a mode-hop-free frequency-sweep external-cavity diode laser, a high-finesse Fabry-Pérot interferometer (to measure accurately the frequency sweep range), homodyne detection, and data processing. Results have shown that the inaccuracy will not exceed 10 μm for distances up to 1 m, at an affordable degree of complexity.

A novel sensor for use in displacement metrology is proposed. It is based on grating imaging, which conventionally uses two amplitude gratings to generate a sinusoidal image. In the conventional method, the poor signal-to-noise ratio of the displacement output is one of the barriers to precise measurement, because 75% of the illumination light is trapped by the two amplitude gratings. In the proposed sensor a cylindrical lens array and a sine phase grating are used as the first and the second grating, respectively. Therefore, the illumination light is intercepted by neither, so that four times higher displacement signal amplitude than that of the conventional sensor can be expected. Consequently, four times higher signal-to-noise ratio can be obtained. Furthermore, the proposed sensor generates a sinusoidal output with little distortion by using the sine phase grating with optimized conditions, so that accurate measurement can be expected. In our prototype, a cylindrical lens array with a 200-μm period and a reflective sine phase grating with a 100-μm period were used.

The application of the optical vortex interferometer (OVI) to small-angle rotation measurements is presented. The OVI is based on a regular lattice of optical vortices. In our experimental setup a regular lattice of optical vortices is produced by the interference of three plane waves. The vortex points are stable, pointlike structures within the interference field. Distortion of one, two, or three of the interference waves results in a characteristic vortex lattice deformation. This deformation can be measured and related to the physical quantities being investigated. We show the ability of the OVI to measure the deflection angle and the orientation of the wave vector in a single measurement. Two different methods that allow comparing the geometry of the vortex lattice are used to analyze the results of the experiment. They are compared with the method based on standard two-beam interferograms. The results show that the OVI system can be successfully used to measure the deflection and orientation of the wave vector. The vortex methodology is more accurate than classical two-beam interferometry for rotation angles in the range of a few arcseconds.

The long chain of a polymer molecule often has intrinsic linear birefringence and/or dichroism, which lead to macroscopic properties when the molecules have a preferred orientation under nonequilibrium conditions, such as flow of a polymer melt. Measurements of properties, including linear birefringence, in a polymer melt can in turn lead to valuable insights into its structure, morphology, and rheology. We demonstrate that a spectropolarimeter based on an acousto-optic tunable filter can measure linear birefringence in real time during the manufacture of polymers, at hundreds of wavelengths, within 5 min, and thus provides more information than use of a spectrometer or laser-based polarimetry alone. In this work, optical properties of different molten ethylene vinyl acetate samples were measured with a spectropolarimeter based on an acousto-optic tunable filter and a photoelastic modulator in the near infrared. Regression models of the results indicate good correlation between the melt indices of the samples and the measured spectra.

Fabry-Perot microcavity luminescent screens for optically written display are presented. The screens consist of dielectric mirrors sandwiching a luminescent layer. An incident 975-nm laser source excites the luminescent medium by upconversion for emission in red, green, or blue. The Fabry-Perot microcavity serves to narrow the emission band, leading to more saturated color. The design and fabrication are described. The display creates good images with an unprecedented color gamut.

This article analyzes the efficacy of the light sources and their limitations in theory and in technology. The LED's spectra were simulated by a Gaussian model to calculate the efficacy. The conventional light sources have been compared with LEDs; the results show that significant increase of LEDs' internal quantum efficiency and extraction efficiency is essential for LED application in general lighting.

A single-longitudinal-mode (SLM) fiber ring laser is demonstrated by introducing internal lasing injection and self-injection feedback. Internal lasing, generated in an auxiliary cavity, interacts with the laser oscillation in a main cavity to suppress mode hopping. Self-injection feedback loops are incorporated in the main cavity to serve as laser mode filters. Neither an ultra-narrow bandpass filter nor a precise control for laser cavity length is required in achieving stable SLM operation.

The main properties of acousto-optic modulators (AOMs) applied in laser technology are presented and discussed. The critical review of application of AOMs in several types of diode-pumped solid-state lasers (DPSSLs) is given. A short description of few DPSSLs developed in our group is presented. The parameters of a simple AO Q-switched Nd:YVO₄ laser (peak power up to 60 kW, pulse duration 5 to 15 ns, repetition rate 10 to 100 kHz, with average power above 5 W) are satisfactory for various applications. The achieved brightness of 10¹⁷ W/m²/sr is comparable to that of the strongest technological Q-switched lasers of kilowatt average power. The main aim of paper is to present novel type of laser with acousto-optic modulation, namely, the AO Q-switched and mode locked (QML) laser. We have designed a 3.69-m-long Z-type cavity with resonance frequency matched to the rf of the AOM. As a gain medium an Nd:YVO₄ crystal end-pumped by a 20-W laser diode was applied. The envelope energy of the QML pulse train was up to 130 μJ with subnanosecond mode-locked pulses of 30-μJ maximum energy.

A simple and practical method for the study of polymer thermal and mechanical properties using a fiber Bragg grating (FBG) sensor is presented for the first time, in which the FBG is embedded in a typical epoxy polymer. By measuring the sensitivity change of the FBG sensor, changes of the thermal-mechanical properties of the polymer with temperature and pressure can be measured. The experimental results show that this technique is capable of providing continuous in-line monitoring such properties with high sensitivity during transformation between the glassy state and the rubbery state of a polymer within the temperature and pressure range of 20 to 180°C and 0 to 15 MPa.

This work demonstrates waveguide devices based on a novel photocrosslinkable fluorinated poly(arylene ether ketone). A new molecular design has enabled waveguide fabrication to be achieved for the first time using this kind of polymer, through direct UV patterning and a wet-etch process, which is faster and more convenient and economical than the process based on standard reactive-ion etching that has been applied to previously reported poly(arylene ether ketone) materials. High-quality waveguides with smooth, well-defined sidewalls have been produced, and optical splitter devices based on directional coupling are demonstrated. Optical characterization of these devices suggests that the waveguide quality is comparable to that of waveguides fabricated using a dry-etch process, and the experimental data obtained from the fabricated optical splitters are in excellent agreement with theoretical predictions.

We demonstrate the generation of an 160-GHz optical pulse train using a 40-GHz driven phase modulator followed by two stages of delayed interferometers. The simulation shows that the pulse width of the generated chirp-free 160-GHz carrier-suppressed return-to-zero optical pulse train is 3.13 ps

A simple and straightforward method is applied to experimentally obtain the wavelength dependence of the intercore beat length for two different types of twin-core microstructured polymer optical fiber. The results are compared with numerical calculations using a full-vectorial plane-wave expansion method, which shows good agreement.

We have analyzed the temperature-dependent birefringence of a polarization-maintaining photonic crystal fiber. The temperature-coefficient of birefringence, dB/dT, for a commercially available polarization-maintaining photonic crystal fiber was found to be approximately -2.0×10^-9 K^-1. This is 35 times smaller than that of a standard polarization-maintaining fiber, which was approximately -7.0×10^-8 K^-1. Based on numerical analysis of the fiber structures, we determined that the temperature-dependence of the birefringence of the polarization-maintaining photonic crystal fiber is mainly due to a combination of temperature-dependent structure and index change. Due to thermal expansion of the silica, the photonic crystal structure of the fiber deforms, resulting in the shifting of the photonic band gap, which results in the birefringence change. Temperature-dependent refractive index change of the silica also causes a shift in the photonic band gap and thus a birefringence change. The numerically calculated dB/dT of the photonic crystal fiber was found to be approximately (-4±2)×10^-9 K^-1, and is in excellent agreement with the experimental results.

An enhanced code structure for spectral amplitude coding in optical code division multiple access systems based on double weight (DW) code families is proposed. Enhanced double weight (EDW) codes possess ideal cross-correlation properties such as maximum cross correlation of 1 and a weight that can be any odd number greater than 1. It has been observed through theoretical analysis and experimental simulation that EDW codes perform significantly better than Hadamard and modified frequency-hopping (MFH) codes. In this study, point-to-point transmission with three EDW-encoded channels was tested at the bit rate of 10 Gbit/s per channel.

We design and simulate a nonsymmetric vernier type of multiple ring resonator (MRR) filters to achieve wider free spectral range (FSR) with different ring radii. The expanded FSR is determined by the least common multiple of the FSRs of the individual ring resonators. The dependence of the transmission characteristics of the MRR on the coupling coefficients of directional couplers is studied. The improvement in suppression of interstitial resonances by using high-order vernier filters is also investigated. A graphical approach with a signal flow graph has been found very useful for quickly deriving the optical transfer functions of filters in the Z domain.

A white light interferometer is developed to measure the distributed polarization coupling in high-birefringence polarization-maintaining fibers (PMFs). Usually the birefringence dispersion between two orthogonal eigenmodes of PMFs is neglected in such systems. Theoretical analysis and experimental results show that the birefringence dispersion becomes a nonnegligible factor in a long-fiber test. Significant broadening of interferograms and loss of longitudinal coherence are observed. The spatial resolution and measurement sensitivity of the system decrease correspondingly. Optimum spectrum width selection is presented for better spatial resolution and measurement range.

A novel contention resolution scheme for optical burst switching (OBS) networks is proposed. Traffic payload is classified into two types at the edge nodes, and they are transferred through the core nodes using two different routing algorithms—least-hop first routing and shortest-path first routing, respectively, leading to balanced traffic loads among fiber links. By using this contention resolution scheme, active avoidance of burst contention is achieved. Performance evaluation and simulation results indicate that the new scheme outperforms the commonly used shortest-path first routing and is robust under both Poisson and self-similar traffic. Furthermore, the new scheme can provide quality-of-service (QOS) differentiation when used with wavelength conversion, and the implementation of this scheme is easy, which makes OBS technology more applicable in network engineering.

We experimentally demonstrate a novel decimal optical buffer scheme based on a multiloop configuration and a single switch element-an optical crosspoint switch (OXS) matrix. Its variable-delay range is of 1 to 999 times the basic delay unit. The buffer dynamic reconfiguration can be achieved at nanosecond switching speed. Our results show that by using a differential phase-shift keying (DPSK) payload in the buffer it can outperform an on-off keying payload with 4-dB sensitivity improvement owing to its alleviation of patterning-induced degradation, clearly validating DPSK as a promising modulation format to overcome nonlinear impairments and to extend number of hops in all-optical packet-switching network.

A method for improving the accuracy of surface shape measurement by multiwavelength holography is presented. In our holographic setup, a Bi₁₂TiO₂₀ photorefractive crystal was the holographic recording medium, and a multimode diode laser emitting in the red region was the light source in a two-wave mixing scheme. On employing such lasers the resulting holographic image appears covered with interference fringes corresponding to the object relief, and the interferogram spatial frequency is proportional to the diode laser's free spectral range (FSR). Our method consists in increasing the effective free spectral range of the laser by positioning a Fabry-Perot étalon at the laser output for mode selection. As larger effective values of the laser FSR were achieved, higher-spatial-frequency interferograms were obtained and therefore more sensitive and accurate measurements were performed. The quantitative evaluation of the interferograms was made through the phase-stepping technique, and the phase map unwrapping was carried out through the cellular-automata method. For a given surface, shape measurements with different interferogram spatial frequencies were performed and compared with respect to measurement noise and visual inspection.

A method for selective imaging using multiwavelength digital holographic reconstructions and the phase response of a sound source is demonstrated. Several sound measurements, using laser vibrometry, and digital reconstructions are made for several frequencies of the sound field emitted from two ultrasound transducers with different phase characteristics. Adding the reconstructed complex amplitudes together and applying a filter derived from the standard deviation over the phases for the different reconstructions makes possible a selective imaging of primary sources. When the imaging method is calibrated for a certain phase response, only primary sources with that particular phase response are imaged. Other sources and unwanted speckles are efficiently suppressed. The depth resolution obtained is 3 wavelengths.

The paper deals with the computer-aided tomographic reconstruction of radar images of objects behind opaque dielectric walls that are illuminated by microwave radiation emerging from moving ultrawideband (UWB) radars. Tomographic techniques such as filtered backprojections are used here, in conjunction with some available electromagnetic computational codes such as X-Patch, to create the desired target images. The use of UWB radars to penetrate through the walls and image the objects behind them is novel and of obvious desirability. It is only possible if the walls are not too thick and not too lossy. In the present work, several wall types of different dielectric compositions and thicknesses are used to simulate a room that encloses two human targets placed at specified locations. The UWB radar moves along the room's front wall in a straight path with its beams directed normal to the wall and pointing towards its interior. Some basic principles of classical tomography are reviewed, and the reconstruction process via the X-Patch computational code and present-day backprojection techniques is completed for all the walls and targets here considered. This simulation demonstrates that under the specified conditions, the reconstruction of the radar images of the two humans is clearly achievable in all but in very adverse conditions. Furthermore, the dimensions and wall characteristics of the rooms can be estimated from the resulting radar images.

Infrared (IR) images derived from cloudy skies are always too spatially varied for tiny targets to be detected, especially for single-frame detection. Using the neural networks (NN) nonlinear regression, discrimination, and self-leaning capability, an NN-based method is proposed for tiny point target detection in single-frame IR images with high background clutter. First, the background was estimated by an improved NN-based morphologic filter, the structure element of which was optimized by a two-layer NN. Second, noise characteristics were well studied, and thus a two-level segmentation is presented to delete noises as well as to further remove remaining background components. Last, images with several potential targets were fed to a BP NN that predicted the identity of the input, which was either a target or a pseudo-target. It is these two neural networks that separate target from background and pseudo-target, respectively, with different training destinations, thus avoiding the over-training problem. Results on real data indicate that, given the false alarm probability, the detection probability by this method reaches 98.3%, which is improved by 11.02% compared to the traditional approach with fixed SE and without trained NN.

We analyze the efficacy of various point target detection algorithms for hyperspectral data. We present a novel way to measure the discrimination capability of a target detection algorithm; we avoid being critically dependent on the particular placement of a target in the image by examining the overall ability to detect a target throughout the various backgrounds of the cube. We first demonstrate this approach by analyzing previously published algorithms from the literature; we then present two new dissimilar algorithms that are designed to eliminate false alarms on edges. Trade-offs between the probability of detection and false alarms rates are considered. We use our metrics to quantify the improved capability of the proposed algorithms over the standard algorithms.

A novel spatiotemporal method is proposed for detection of and recovery from dirt sparkles on degraded color films. Firstly, a confidence measurement of dirt is extracted by comparing pixel values per color component after global motion compensation. Then, candidate dirt is detected by filtering and thresholding this confidence measurement. For each candidate region of dirt, bidirectional local motion compensation is employed, and motion-compensated pixels are selected according to their confidence values, using an improved ML3Dex filter to preserve details and avoid oversmoothing of images. Experiments on real data demonstrate that our method outperforms several well-established algorithms in accuracy, efficiency, and robustness.

Since the current rate control schemes in H.264 do not present the capability of efficient frame-level bit allocation, the video quality varies greatly for sequences with scene cuts or large motions. To overcome that limitation, we propose a rate control scheme based on the incremental proportional-integral-differential (PID) algorithm. That algorithm is introduced to control the buffer and decrease the influence of buffer surface fluctuation on the process of frame-level bit allocation. Extensive simulation results show that this rate control scheme, without expensive computational complexity added, decreases the average video quality variations by 21.07%.

In practical use, objects in still images and videos are easy to misappropriate with handy image-processing tools and need to be protected. However, the few proposals for object watermarking suffer from resynchronization problems. In this study, we develop an object-based watermarking method based on efficient segmentation using lines parallel and perpendicular to two principal axes in the spatial domain. A patchlike scheme is designed to embed and extract invisible watermarks. In contrast with the previous object-based watermarking schemes, extra information for resynchronization is not required to be stored in our method. Experimental results show the robustness of the proposed method against many kinds of geometrical attacks.

A new imaging configuration whose trajectory is a multisegment straight line is investigated, and a practical reconstruction algorithm is proposed. It is a natural extension of an imaging configuration with a straight-line trajectory. These kinds of scanning systems may be useful in industry and security inspections. As is known, projection data from a single straight-line trajectory are incomplete and their reconstruction suffers from a limited-angle problem. A multisegment straight-line trajectory can be used to compensate for this deficiency. To reconstruct images, a practical reconstruction algorithm is derived. It is of the Feldkamp-Davis-Kress (FDK) type, and is efficient and straightforward. Like the FDK algorithm, our reconstruction is exact in the midplane and can be exact everywhere if the density of the scanned object is independent of the direction z, though the integral of the reconstructed image along z is no longer preserved. Numerical simulations validate our method.

Blind image restoration means estimating the true image from an observed degraded image, with incomplete or little prior knowledge of the blur function and the true image. Commonly, iterative or recursive methods are applied to this problem, but they are usually time-consuming, uncertain, and divergent. Focusing on a limited but significant class of point spread functions (heavy-tailed Lévy processes), a noniterative blind image restoration method is proposed, which directly estimates the point spread functions from the degraded image's Fourier amplitude and restores the image by general slow evolution of a continuation boundary. This method is based on the fast Fourier transform, so it can accomplish the blind restoration of a 512×512 image in seconds of CPU time on a current desktop platform. From several experiments on synthetic blurred images and on actual images, it is found that the quality of the restored images has been greatly improved, and many fine details are restored, by applying this method.

Principal components analysis (PCA) and independent-component analysis (ICA) are widely used transforms to perform various tasks. Mixing both transforms has not been investigated. This paper develops a new transform, called the mixed PCA/ICA transform, which combines m principal components (PCs) produced by PCA and n independent components (ICs) generated by ICA to form a new set of m+n mixed components to be used for hyperspectral image analysis. Four problems need to be addressed. One is to determine the total number of components, p, needed to be generated for the mixed (m,n)-PCA/ICA transform. The second is how to combine the PCA and ICA in a single transform. Since the ICA does not prioritize its generated ICs in the same way that the PCs are ranked by the PCA using data variances, how to generate an appropriate set of n ICs becomes a third problem. Finally, the fourth problem is to decompress the compressed data based on the mixed PCA/ICA components if there is a need to reconstruct the original data. This paper solves these four problems and further conducts experiments to demonstrate the utility of the mixed PCA/ICA transform in subpixel detection and mixed pixel classification and quantification.

The Mirau interference microscope features a very compact interferometer incorporated in a single microscope objective. We describe a simple modification that results in the exiting beams being orthogonally polarized. This modification makes it possible to introduce achromatic phase shifts in the two beams, facilitating the use of the Mirau interferometer for white-light phase-shifting interference microscopy.

We propose a new approach to image compression based on the principle of Shapiro's embedded zero-tree wavelet (EZW) algorithm. Our approach, the efficient EZW (E-EZW), uses six symbols instead of the four used in the original Shapiro's algorithm to minimize the redundant symbols, and optimizes the coding by binary regrouping of the information. This approach can produce results that have a significant improvement over the peak signal-to-noise ratio and compression ratio obtained by Shapiro without affecting the computing time. These results are also comparable to those obtained using the set partitioning in hierarchical trees (SPIHT), set partitioning embedded block (SPECK), and JPEG2000 algorithms.

We examine the performance of illumination-invariant face recognition in outdoor hyperspectral images using a database of 200 subjects. The hyperspectral camera acquires 31 bands over the 700- to 1000-nm spectral range. Faces are represented by local spectral information for several tissue types. Illumination variation is modeled by low-dimensional spectral radiance subspaces. Weighted invariant subspace projection over multiple tissue types is used for recognition. The experiments consider various face orientations and expressions. The analysis includes experiments for images synthesized from indoor face reflectance images of 200 subjects, using a database of more than 7,000 outdoor illumination spectra. We also examine a set of images of 10 subjects of the 200 that were acquired under outdoor conditions using a calibrated hyperspectral camera.

We present an analysis of the dynamics of conical waves partially obstructed by opaque objects. The analysis yields the incoming and outgoing conical waves that form the Bessel beams (or any other propagation-invariant beams) when opaque obstructions are set on and off axis. The results show that the invariance of Bessel beams with finite transverse extension is no longer maintained under the mentioned conditions.

Surface scattering effects are merely diffraction phenomena resulting from random phase variations induced on the reflected wavefront by microtopographic surface features. The Rayleigh-Rice and Beckmann-Kirchhoff theories are commonly used to predict surface scattering behavior. However, the Rayleigh-Rice vector perturbation theory is limited to smooth surfaces, and the classical Beckmann-Kirchhoff theory contains a paraxial assumption that confines its applicability to small incident and scattering angles. The recent development of a linear systems formulation of nonparaxial scalar diffraction phenomena, indicating that diffracted radiance is a fundamental quantity predicted by scalar diffraction theory, has led to a reexamination of the classical Beckmann-Kirchhoff scattering theory. We demonstrate an empirically modified Beckmann-Kirchhoff scattering model that accurately predicts nonintuitive experimental scattering data for rough surfaces at large incident and large scattering angles, yet also agrees with Rayleigh-Rice predictions within their domain of applicability for smooth surfaces.

This PDF file contains the errata for “OE Vol. 46 Issue 07 Paper 2768976” for OE Vol. 46 Issue 07