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We propose to enhance the capabilities of the human visual system by performing optical image processing directly on an observed scene. Unlike previous work which additively superimposes imagery on a scene, or completely replaces scene imagery with a manipulated version, we perform all manipulation through the use of a light modulation display to spatially filter incoming light. We demonstrate a number of perceptually motivated algorithms including contrast enhancement and reduction, object highlighting for preattentive emphasis, colour saturation, de-saturation and de-metamerization, as well as visual enhancement for the colour blind. A camera observing the scene guides the algorithms for on-the-fly processing, enabling dynamic application scenarios such as monocular scopes, eyeglasses and windshields. [ABSTRACT FROM AUTHOR]

The nonlinear response of light transmission characteristics of a liquid crystal (LC) spatial light modulator (SLM) is studied. The results show that the device exhibits a wide range of variations with different control parameters and input settings. Experiments were performed to obtain intensity modulation that is best described by either power-law or sigmoidal functions. Based on the inverse transformation, an appropriate pre-processing scheme for electrically addressed input gray-scale images, particularly important in several optical processing and imaging applications, is suggested. Further, the necessity to compensate the SLM image nonlinearities in a volume holographic data storage and retrieval system is demonstrated. [ABSTRACT FROM AUTHOR]

Spatial characteristics of thermal infrared (TIR) images are generally described by image-derived point spread function (IDPSF) for sampled imaging system. Most investigators working on IDPSF on-orbit evaluation focus on visible and near-infrared images and pay little attention on TIR ones, the reason of which lies on the fact that the assumption of an observed target with an ideal step profile is not suitable for TIR band. A new approach for TIR images is proposed here based on a more common slope-profile model, where the transition features, i.e., the sample number (Nslope) and the beginning position of slope interval, are extracted from the observed signals. Simulation results show that the estimation performance will be increased, with lower noise level as well as higher system modulation transfer function value at half of normalized spatial frequency (MTF0.5) or smaller Nslope. For a good performance system with noise squared-root variance (SRV) nomore than 1.0 count and MTF0.5 between 0.3 and 0.4, the relative error between simulated and estimated MTF0.5's is less than 20%. The IDPSF of FY-2C satellite TIR band is estimated, and the derived MTF0.5 is properly close to on-ground testing results. The image quality of FY-2C TIR band has been improved by using Wiener filtering and the estimated IDPSF, which eventually benefits the cloud detection product with more detectable low fractus and increased detection accuracy by about 1% in winter. Considering a step-profile target as a special case of this model, the proposed approach is also suitable for visible and near-infrared images. [ABSTRACT FROM AUTHOR]

Abstract: We investigate the change of higher diffraction order images in holographic image storage and reconstruction process. In experiments, an s-polarized Ar+ laser (488.0nm) was used to record permanent grating in the dye-doped liquid crystal, 4,4′-n-entylcyanobiphenyl (5CB) doped with 1wt% methyl-red (MR), at a small incident angle. Higher diffraction order images were observed when the signal beam was focused in front of and behind the film. Then the film was illuminated by an s-polarized He–Ne laser (632.8nm) in the direction perpendicular to the surface. The higher diffraction order images were reconstructed. A theory about the change of higher diffraction order images is developed, which is in good agreement with experimental results. The results show that the higher diffraction order provides a useful method for optical information processing. [Copyright &y& Elsevier]

We investigated the use of an analog self-electrooptic effect device based on GaAs multiple quantum wells as an image processor chip to early vision processes. We focused our attention at the edge detection process using layouts of photo detectors to extract Laplacians of images. Laplacians of linear, constant, step, and Gaussian intensity profiles agree with the expected values. These results show that the device works properly as an edge detector. [ABSTRACT FROM AUTHOR]

In this paper, we examine the accuracy of manifold coordinate representations as a reduced representation of a hyperspectral imagery (HSI) lookup table (LUT) for bathymetry retrieval. We also explore on a more limited basis the potential for using these coordinates for modeling other in water properties. Manifold coordinates, are chosen because they are a data-driven intrinsic set of coordinates, which naturally parameterize nonlinearities that are present in HSI of water scenes. The approach is based on the extraction of a reduced dimensionality representation in manifold coordinates of a sufficiently large representative set of HSI. The manifold coordinates are derived from a scalable version of the isometric mapping algorithm. In the present and in our earlier works, these coordinates were used to establish an interpolating LUT for bathymetric retrieval by associating the representative data with ground truth data, in this case from a Light Detection and Ranging (LIDAR) estimate in the representative area. While not the focus of the present paper, the compression of LUTs could also be applied, in principle, to LUTs generated by forward radiative transfer models, and some preliminary work in this regard confirms the potential utility for this application. In this paper, we analyze the approach using data acquired by the Portable Hyperspectral Imager for Low-Light Spectroscopy (PHILLS) hyperspectral camera over the Indian River Lagoon, Florida, in 2004. Within a few months of the PHILLS overflights, Scanning Hydrographic Operational Airborne LIDAR Survey, LIDAR data were obtained for a portion of this study area, principally covering the beach zone and, in some instances, portions of contiguous river channels. Results demonstrate that significant compression of the LUTs is possible with little loss in retrieval accuracy. [ABSTRACT FROM AUTHOR]

Image analysis using polarizing methods allows removing the polarized light component from recorded images. This is known as polarization difference imaging (PDI). The use of liquid crystals (LC) in PDI was proposed in 2002. Modified LC unit with a properly oriented LC layer was proposed by the authors. The main parameters which characterize an imaging system, employing a circular LC filter, were determined and presented in previous papers. In this work, the basics of the circular LC filter construction and theory are presented. Two application configurations of PDI imaging systems are shown. Experimental results of image processing based on object’s polarization properties are discussed. [ABSTRACT FROM AUTHOR]

High-speed optical reconstruction of 3D-scenes can be achieved using digital holography with binary digital micromirror devices (DMD) or a ferroelectric spatial light modulator (fSLM). There are many algorithms for binarizing digital holograms. The most common are methods based on global and local thresholding and error diffusion techniques. In addition, hologram binarization is used in optical encryption, data compression, beam shaping, 3D-displays, nanofabrication, materials characterization, etc. This paper proposes an adaptive binarization method based on a combination of local threshold processing, hologram division into blocks, and error diffusion procedure (the LDE method). The method is applied for binarization of optically recorded and computer-generated digital holograms of flat objects and three-dimensional scenes. The quality of reconstructed images was compared with different methods of error diffusion and thresholding. Image reconstruction quality was up to 22% higher by various metrics than that one for standard binarization methods. The optical hologram reconstruction using DMD confirms the results of the numerical simulations. [ABSTRACT FROM AUTHOR]

The article presents a paper which proposes the use of indexed composite filters (ICFs) for multiple pattern recognition. It discusses the advantages of the proposed ICF over the usual composite filters such as its potential for identifying the object of the learning class being detected at the output. The results of computer simulation conducted using alphabetic input scenes illustrating the method's efficiency are also presented.

Methods of polarization analysis in imaging systems are quite new approach. It allows to remove the polarized light component from recorded images, and is known as Polarization Difference Imaging (PDI). The use of liquid crystals (LC) in PDI was proposed in 2002. Modified LC unit with properly oriented LC layer was proposed by the authors. In this work specific LC filter and set-up for image analysis are presented. The examination of the azimuthal detectivity of PDI system is performed. The method of digital analysis of acquired images and detectivity determination is presented. Obtained results are shown and discussed. [ABSTRACT FROM AUTHOR]

Abstract: A digital holography interference pattern generated by a computer calculation (computer generated hologram, CGH) is one of the most expensive contents and its usage is being expanded. Thus, it is highly necessary to protect the ownership of a digital hologram. This paper introduces a watermarking scheme, a method to protect the ownership of digital holograms using the DCT domain data as the ones to be watermarked. This scheme shows very high imperceptibility and strong robustness against the anticipated attacks. We expect that the conclusions of this paper will be a very useful basis for further work in the area of electronic watermarking schemes for the digital holograms. [Copyright &y& Elsevier]

Abstract: The tendency today is to replace high-dynamic light modulators by high-speed binary ones (of which the micromirror is the best example). This kind of spatial light modulators (SLM) fulfils all the present needs in displays. They are used in optical communications as binary systems and also in display applications (video projectors) with temporal multiplexing, in order to generate greyscale or colour images. In optical processing, and in the majority of coherent applications, temporal dithering introduces some distortions. In this paper, this point is studied with simulations. We point out that temporal multiplexing cannot be used in the Fourier plane. In the imaging plane, the distortion is weak if the filter has a positive impulse response. [Copyright &y& Elsevier]

The article reports on all-optical multifunctional logic gates for image information using photorefractive two-wave mixing. The optical setup is simply configured compared with other all-optical logic gates for image information. The logic operations can be switched by means of the on-off control of the signal and the pump beam illumination. The spatial distribution of beam intensity in the logic gates are analyzed using a finite difference beam propagation method.

Abstract: A method for omnidirectional real-time optical edge extraction is proposed. The method consists on the design of a complex filter that is implemented in a Vander Lugt like optical processor. It is emphasized the rotation invariance of the technique, as its equivalence with the Canny edge detector. Numerical simulations have been performed to compare the proposed implementation with some frequently used edge detectors and enhancers. Experimental results are presented to show the very good performance of the method. [Copyright &y& Elsevier]

Abstract: We report some photorefractive higher-order diffraction phenomena of a liquid crystal polymer composite. The photorefractive composite consists of the polymer poly[N-vinylcarbazole] (PVK) doped with the chromophore 4,4′-n-entylcyanobiphenyl (5CB) and the sensitizer C60. In two-wave coupling experiments, the signal beam was interfered by a mutually coherent reference beam within composite materials at a small incident angle. Results are given when the composite was placed behind the focal plane, in front of the focal plane, and in the focal plane. Higher-order diffraction images were obtained by amplification and reduction. A theory of the properties of higher-order diffraction images in a photorefractive liquid crystal polymer composite is developed. The theory is in good agreement with the results of experimental work. The experiments demonstrate the feasibility of optical image processing. [Copyright &y& Elsevier]

The images recorded by optical telescopes are often degraded by aberrations that induce phase variations in the pupil plane. Several wavefront sensing techniques have been proposed to estimate aberrated phases. One of them is phase diversity, for which the joint least-square approach introduced by Gonsalves et al. is a reference method to estimate phase coefficients from the recorded images. In this paper, we rely on the asymptotic theory of Toeplitz matrices to show that Gonsalves' technique provides a consistent phase estimator as the size of the images grows. No comparable result is yielded by the classical joint maximum likelihood interpretation (e.g., as found in the work by Paxman et at). Finally, our theoretical analysis is illustrated through simulated problems. [ABSTRACT FROM AUTHOR]

In vivo fluorescence molecular imaging and tomography has facilitated monitoring of genomics and proteomics over time and on the same animal. A highly important issue, however, has been the robust registration of animals imaged at different time points to obtain accurate description of activity and location. This paper presents a method for aligning temporal data of small animals based on surface anatomical features and improving the accuracy of monitoring fluorophore distribution. The method can account for differences in the positioning and compression of small animals and can be extended to three-dimensional as well as to other imaging modalities. [ABSTRACT FROM AUTHOR]

An efficient, physics-based remote bathymetry method for the littoral zone is described and illustrated with applications to QuickBird, Littoral Airborne Sensor: Hyper- spectral (LASH), and Airborne Visible/Infrared Spectrometer (AVIRIS) spectral imagery. The method combines atmospheric correction, water reflectance spectral simulations, and a linear unmixing bathymetry algorithm that accounts for water surface reflections, thin clouds, and variable bottom brightness, and can incorporate blends of bottom materials. Results include depth maps, bottom color visualizations, and in favorable cases, approximate descriptions of the water composition. In addition, atmospheric correction was advanced through new capabilities added to the Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes (FLAASH) and Moderate Resolution Transmittance (MODTRAN) codes, including characterization of the aerosol wavelength dependence and a discrete-ordinate-method radiative transfer scaling technique for rapid calculation of multiply scattered radiance. [ABSTRACT FROM AUTHOR]

Roberts-operator-based edge detection is implemented using polarization-encoded optical shadow casting. The proposed technique yields better results than the previously reported shadow-casting edge detectors. [ABSTRACT FROM AUTHOR]

Multi-slice ptychography is a diffractive imaging technique that can reconstruct the information of a 3-D object from its diffraction intensities. In this article, we propose a multi-slice ptychographic encoding method for the encryption of multiple and color images. Full-phase images to be encrypted together with inserted phase keys are transformed into diffraction intensities (i.e., cipher texts) via multi-slice ptychographic encoding and double random phase encoding. The multi-slice ptychographic encoding refers to the process of using ptychographic scanning and recording to encrypt a multi-slice object that is composed of secret images and inserted phase keys. During decryption, an iterative phase retrieval algorithm is modified. The feasibility, robustness and security of the proposed method are analyzed. Numerical simulation results show that the proposed method can achieve high-quality decryption, and has high security and robustness against noise, compression, and occlusion. • The 3-D diffractive imaging technique, multi-slice ptychography, is applied to encrypt multi-image and color image. • With inserted phase keys, the proposed method can achieve fast and high-quality image decryption. • The system security is enhanced by the inserted phase keys that can effectively enlarge the key space. • The proposed method is robust to noise, compression and occlusion attack. [ABSTRACT FROM AUTHOR]

Optical implementation of pattern fuzzy logic based on shadow casting is reported. In particular, a new spatial encoding method for fuzzy logic variables is proposed to optically realize the maximization and minimization operations needed by fuzzy logic. Experimental results are also given, © 1992 John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]