Coherent Image Processing Research Articles

An overview of image-processing methods for Affymetrix GeneChips

We present an overview of image-processing methods for Affymetrix GeneChips. All GeneChips are affected to some extent by spatially coherent defects and image processing has a number of potential impacts on the downstream analysis of GeneChip data. Fortunately, there are now a number of robust and accurate algorithms, which identify the most disabling defects. One group of algorithms concentrate on the transformation from the original hybridisation DAT image to the representative CEL file. Another set uses dedicated pattern recognition routines to detect different types of hybridisation defect in replicates. A third type exploits the information provided by public repositories of GeneChips (such as GEO). The use of these algorithms improves the sensitivity of GeneChips, and should be a prerequisite for studies in which there are only few probes per relevant biological signal, such as exon arrays and SNP chips.

Acousto-optic image processing in coherent light

The results of recent studies on coherent acousto-optic image processing performed at the chair of physics of oscillations at the Department of Physics of Moscow State University are reported. It is shown that this processing method is based on the filtration of the spatial spectrum of an optical signal in an acousto-optic cell. The main attention is paid to the analysis of the dependence of the transfer function of the cell on the crystal cut, geometry of acousto-optic interaction, and acoustic-wave parameters. It is shown that an acousto-optic cell allows the image differentiation and integration as well as the visualisation of phase objects. The results of experiments and computer simulation are presented which illustrate the possibilities of acousto-optic image processing.

Real-time edge-enhanced optical correlation with a cerium-doped potassium sodium strontium barium niobate photorefractive crystal

The nonlinear diffraction property of a volume grating written by two-wave mixing in a cerium-doped potassium sodium strontium barium niobate crystal is applied in a coherent image processing system to obtain real-time image edge enhancement as well as edge-enhanced optical correlation. The theoretical analysis of the correlator is given, and the experimental results of optical correlation are presented, which are compared with the computer-simulated results.

High-quality image processing architecture for facsimiles

A total and coherent image processing architecture for G3/G4/ISDN facsimiles is proposed that features high-quality multi-level processing by means of correlative area scanning and a software-oriented processing architecture. This image processing LSI controller includes a resolution converter and error diffusion halftone processing circuits in 4000 gates. A semi-superfine scanning mode is evaluated, which will be adopted as a new CCITT G3 optional mode.

Atomic Imaging of Crystals using Large-Angle Electron Scattering in STEM

It is well known that conventional atomic resolution electron microscopy is a coherent imaging process best interpreted in reciprocal space using contrast transfer function theory. This is because the equivalent real space interpretation involving a convolution between the exit face wave function and the instrumental response is difficult to visualize. Furthermore, the crystal wave function is not simply related to the projected crystal potential, except under a very restrictive set of experimental conditions, making image simulation an essential part of image interpretation. In this paper we present a different conceptual approach to the atomic imaging of crystals based on incoherent imaging theory. Using a real-space analysis of electron scattering to a high-angle annular detector, it is shown how the STEM imaging process can be partitioned into components parallel and perpendicular to the relevant low index zone-axis.It has become customary to describe STEM imaging using the analytical treatment developed by Cowley. However, the convenient assumption of a phase object (which neglects the curvature of the Ewald sphere) fails rapidly for large scattering angles, even in very thin crystals. Thus, to avoid unpredictive numerical solutions, it would seem more appropriate to apply pseudo-kinematic theory to the treatment of the weak high angle signal. Diffraction to medium order zero-layer reflections is most important compared with thermal diffuse scattering in very thin crystals (<5nm). The electron wave function ψ(R,z) at a depth z and transverse coordinate R due to a phase aberrated surface probe function P(R-RO) located at RO is then well described by the channeling approximation;

Coherent image processing using coupled prisms

The total internal reflection (TIR) phenomenon and the coupling of prisms through evanescent waves have been used in the context of several image processing requirements. Results are reported for the spatial filtering of bleached photographic transparencies. It is possible to obtain a positive-negative pair of images in the transmission and reflection modes, the relative amplitude of which can be varied.

The role of prior knowledge in coherent image processing

Models that encode prior knowledge about a scene provide a means for interpreting image data from that scene in more detail than would otherwise be so. Information about both background clutter and target characteristics should be included in this prior knowledge. We demonstrate the use of a generalized noise model to represent a variety of naturally occurring random terrain clutter textures observed in high-resolution synthetic aperture radar (SAR) images. In addition a similar approach is adopted for the simulation of such textures. Having established the background properties we next introduce prior knowledge about any target within the scene and exploit this in achieving a cross-section reconstruction having improved resolution compared with the original image. Examples of such a super-resolution method based on singular value decomposition are demonstrated and the limits of the technique are indicated.

A Formal Representation of Abbe's Theory of Microscopic Image Formation

Continuing previous work, the well known theory of coherent image processing is reformulated using the mathematical tools of Fourier optics. A general wave optical image equation is established from which imperfect imaging, as well as techniques to affect the process of image formation can be derived. This is demonstrated for two methods, known in the field of microscopic mineral diagnostics as Becke's line and the Schroeder-Van Der Kolk Criterion. The observed phenomena are correctly interpreted within the wave optical theory.

Hybrid pattern recognition by features extracted from object patterns and Fraunhofer diffraction patterns: development of a more useful method

A shift-, rotation-, and scale-invariant pattern recognition method is proposed. In this method, an object image is observed by a movable sensing head, and then simple features, which are invariant under shift, rotation, and change of scale of the object image, are extracted by digital image processing. At the same time, the Fourier spectrum of the edge-enhanced object image is obtained by coherent optical image processing, and the shift-, rotation-, and scale-invariant features are derived from the spectrum. Classification of the object is carried out by a small-scale digital processor using both features obtained by digital and analog image processing.

Real time edge enhancement by active spatial filtering via five wave mixing in photorefractive BSO

A technique for active spatial filtering is described which used the degenerate four wave mixing (DFWM) configuration in BSO (Bi 12SiO 20) plus an additional image modification beam. A dynamic hologram is produced in the BSO between a reference wave and the Fourier transform of the object for spatial filtering. The fifth beam is used to selectively erase certain spatial frequencies of the object, producing a modified reconstructed image beam. Good quality edge enhancement is demonstrated, and a real time, fast coherent image processing system is proposed.

Coherent optical generation of Hartley transform of real images

A new method to generate optical Hartley transform (OHT) for 2D real images is proposed. The method is based on polarization encoding of the coherent optical beam. Different coherent optical image processing techniques are discussed.

Fourier Transform Properties of an All-mirror System

An all-mirror system for application in coherent image processing is described. A system with a parabolic mirror offers advantages such as unit magnification, panchromatic correction and the introduction of minimal scattering noise into the Fourier transform plane and the final image. The Fourier transform properties of this system are acceptable for many applications.

Imaging and Fourier transform properties of an all-spherical-mirror system

An all-spherical-mirror system for applications in coherent image processing is described and analyzed. This one-to-one system is panchromatic and can be made to have minimal cosmetic defects. Such a system offers advantages such as multiple wavelength operations and the introduction of minimal scattering noise into the final image. A sample design that is diffraction-limited (for f/8) over the entire area of a standard 35-mm slide is given. The Fourier transform properties of this system are acceptable for many applications.

Coherent optical analog-to-digital conversion using a single halftone photograph

Analog-to-digital (A-D) conversion of intensity transmittance (or reflectance) can be accomplished through nonlinear coherent optical image processing. Theoretically speaking, for any given positive integer N, 2(N) discrete levels of transmittance (or reflectance) can be digitized into binary form simultaneously via pure optical means, involving the proper design and fabrication of a specific halftone screen. The digital outputs of the N bit-planes are selected at the Fourier plane by spatial filtering the (2(n) - 1)th diffraction order, where n = 1, 2, ..., and N, respectively. The specific halftone screen must have (2(N) - 1) gray levels, and it should be emphasized that only a single halftone photograph is required for the optical A-D conversion. The general principle of this new method and a preliminary experimental result of an eight-level A-D conversion are described in this paper.

Holography in Medicine

This book is an interesting collection of 29 papers that were presented by 42 authors at the Holography Symposium in New York in 1973. The book appropriately begins with an excellent summary of the birth and growth of the field of holography written by Nobel Laureate Dennis Gabor, who conceived of the concept of holography in 1947 before the coming of laser in 1962. The articles that follow discuss recent technological advances that offer intriguing possibilities to the advancement of ophthalmology and medicine. The first seven articles of the book are devoted to the basics of holography and aid in the understanding of the subsequent papers. Acoustical and synthetic aperture holograms, applications to microscopy, computer holography, and coherent optical image processing are discussed in this section. The next section discusses holography as a diagnostic tool. Methods are being explored whereby holographic interferometric techniques are used to study bone deformation and

Partially coherent image processing by laser scanning

We describe a class of image-processing optical systems, based on a laser scanner, whose output is an electronic video signal from a simple photodetector. We show that certain image-processing properties of these systems are exactly equivalent to the properties of conventional, partially coherent, image-processing optical systems. These systems are of interest when we want to combine optical image processing with further electronic processing. Some applications, such as electronic read out of phase-encoded images, are discussed.