We explore current technology and research in the field of optic materials properties for information optics, conducted at the S. I. Vavilov State Optical Institute, which is the largest such institute in the continent.
The physicochemical principles of the abnormal dispersion liquids (ADiL) creation are determined here for the first time. These principles allow liquids required for practical tasks that have the following optical characteristics to be found: values of γg-e such that γg-e = (ng - ne)/(nF - nC), where λg = 435.8 nm, λF = 486.l nm, λe = 546.1 nm, and λC = 656.3 nm, and of v'e = (ne - 1 )/ng - nC. The studies carried out show that it is possible to synthesize ADiLs to be effectively used as the materials for scattering and for collecting lenses within a lens system.
The photothermoplastic (PTP), photo- and thermoplastic molecular heterostructure materials, which are based on the new principles ofthe donor-acceptor sensibilizations, real-time optical processing methods, the PIP recording cameras, and optical information processing devices with new properties are considered. It is shown that such molecular heterostructure materials have high values of photosensitivity (20 to 100 ASA) and line resolution (above 600 line pairs/mm) and reversibility of over 1000 cycles. For a consistent recording regime a high reproducibility of parameters is achieved. The practical applications of PIP recording for operational holographic memory devices and optical modulation and bit recording systems are analyzed.
Experimental and theoretical results are presented of photosensitive semiconductor structures as well as the main developments of modern semiconductor photoresistors, photodiodes, including injection ones, based on polycrystalline and monocrystalline materials, multilayer structures and superlattices for the visual-far infrared spectral range. Performance of multielement photodetectors based on lead chalcogenides, germanium and silicon, AIIIBV compounds, and CMT structures is described.
A brief review is given of the problems one may be faced with in developing selective multicomponent photodetectors for a wide wavelength range of electromagnetic radiation-from approximately 0.1 μm in the ultraviolet to 50 μm in the infrared spectrum regions. The limits of this range are mainly defined by spectral distribution of brightness of the solar direct or scattered radiation and by the spectrum of thermal radiation of the earth and objects on its surface.
A review is given of works on nonselective thermal radiation detectors, published and discussed in recent years in the USSR. All types of thermal detectors are used in the USSR in various parts of the infrared region. Every two years a scientific conference on thermal detectors takes place, at which papers are presented on the following topics: pyroelectrical detectors, bolometers, thermoelectrical detectors, optoacoustical detectors, radiometric devices, optical materials used in detectors, and metrology in the infrared region.
A new version of the DEMOS program is presented. DEMOS (design, evaluation, and modeling of optical systems) is integrated dialog software for automatic modeling to estimate and design optical systems with conventional and hologram optical elements. The theoretical principles and the current state of the primary possibilities and application principles of the DEMOS program for optical systems design and simulation on computers are discussed.
From the viewpoint of up-to-date requirements, fundamental scientific and technological problems arising in the design and manufacture of optical reflecting telescopes are formulated as compared to those of the refracting systems. Nontraditional materials, such as beryllium, silicon, and silicon carbide, are shown to be capable of successful competition with traditional optical materials for the telescope mirror. A brief overview is given of the development of beryllium-based mirrors.
The main achievements in the development of optically pumped atomic magnetometers are reviewed. The best up-to-date magnetometers have sensitivities up to 0.1 pT/(Hz)1/2 and absolute accuracy of about 0.1 nT, permitting notless than 10 readings per 1 s. The main applications are earth field gradiometry and variometry.
The basic concepts of surface electromagnetic waves (SEWs) in the optical band, the unique features of their excitation by light at the boundary of condensed media, and the participation of SEWs in the
formation of periodic structures and other photophysical processes that occur on surfaces due to the influence of high-intensity laser radiation are presented. The use of middle infrared SEW for measuring optical characteristics of materials is considered. A method, developed by the authors, for measuring the real part of the SEW wave vector to obtain metal plasma frequency directly, is presented.
The properties of a pseudodeep hologram are studied. This new term refers here to an inclined thin hologram on which a one-dimensional line object is recorded by a sagittal system of beams. In this case the reconstructed image is read out only within the line corresponding to the object. It is shown that, similar to a deep 3-D hologram, the pseudodeep hologram has high angular and spectral selectivity. A simple graphic method for the construction of the images restored by the pseudodeep hologram is presented. A reference-free hologram has been recorded with the help of such a system. When reading out such a hologram for a part of the object recorded on it, the associative image of the object as a whole was reconstructed. The possibilities of using the pseudodeep hologram for performing different operations are considered, including heteroassociative readout of information by the keys associated with it, recognition of pages of information when illuminating the hologram by the objective wave, and multiple recording of information in the same region of the photographic material. In conclusion, the associative memory scheme in which the information pages are recorded on separate stripes of the pseudodeep hologram with the use of different reference sources as the keys associated with these pages has been considered. The retrieval of the pages is performed by illuminating the entire surface of the hologram with one of the reference sources.
The principles of holographic storage and the reconstruction of short light pulses based on spatial spectral decomposition of radiation are described. This method may be designated as time-domain Fourier transform holography or spectral holography. Also described are various transformations of optical time signals based on holographic spectral filtering and dynamic interaction of spectral decomposition waves in nonlinear media. A system of methods of time signal processing based on spectral holography is proposed. Among these methods are shaping optical pulses, space-time conversions of signals, matched filtering, and recognition oftime optical signals. In addition, the possibilities for realizing time-division multiplexing of data streams using dynamic spectral holography are shown.
Specific laser applications in information systems for two important cases-nonlinear digital computing optical systems and coherent information laser systems-are described. Some new results obtained at the S. I. Vavilov State Optical Institute are presented. The state-of-the-art and possible applications of feedback nonlinear optical systems for digital parallel data processing are discussed. New possibilities produced by employing high-quality laser radiation in transverse distributed wide-aperture bistable systems are presented, and the main properties of such systems (spatial hysteresis, diffraction autosolitons, and switching waves) are discussed. A discussion of coherent information laser systems is included. The results obtained with high-performance neodimium-doped lasers are reviewed. The amplification of single-frequency cw laser radiation in a pulsed solid state amplifier is discussed. Finally, some theoretical and experimental results concerning the frequency purity of amplified signals are presented.
A scheme is presented for an optical spatial switch in which independent and arbitrary switching is realized using diffraction of light beams by a programmable microhologram array (MA). It is shown that a bacteriorhodopsin film can be used as a recording medium for an MA. If the throughput of each channel is up to several Gbit/s, the capacity of such a switch can reach 104 x 104 channels, with the time of an arbitrary switching not more than 100 ms. The experimental results given prove the possibility of implementing a switch having these characteristics
An input pattern weighting method is proposed for increasing the efficiency of the recognition of high-correlated patterns. Numerical simulation results are given. An optical implementation of the high-order associative memory model using an inner product scheme with the weighting method is suggested.
TOPICS: Pulsed laser operation, Distance measurement, Laser processing, Detection and tracking algorithms, Target detection, Transmitters, Signal detection, Signal processing, Data processing, Algorithm development
The problems of obtaining and processing information in pulsed laser rangefinders in order to determine ranging object characteristic feature selection and identification under permanent echo conditions are considered, including the influence oftarget spatial length, radiation beam nonuniformity, and random rangefinder target guidance error. Automatic target selection algorithms and circuits are also considered. The principle of target signal selection and identification based on reflected pulse data is proposed.
A package of applied image processing programs is described that was developed for general-purpose computers of the VAX and IBM PC/AT family functioning under the control of VMS-type and MS-DOS-type operating systems.
The problems of using optical coherent information processing techniques for the design of machine vision systems for updatable robotic complexes are studied. The construction of holographic correlators insensitive to distortions of the input image with respect to a reference one is analyzed, and a holographic on-line correlator is presented that performs image input, holographic matched filter synthesis, and real-time image processing. The choice of the optical processors' basic components-the pulsed solid state laser, the image input device based on photoconductor-liquid crystal structure, and the reversible recording medium FTIROS based on vanadium dioxide film is validated. The problems of holographic filter synthesis are also analyzed. The correlator prototype is described and the results of its experimental study for image input by means both of the optical system and the CRT are discussed.
A single optical component, a square prism with a spherical end cap, has been proposed for generating multipie real images of a single object. Ray-tracing computations show that a miniature tunnel lens of this type can multiplex coherent fiber optic arrays and perform digital optical computing operations with high efficiency and no crosstalk.
beam-scanning binary logic (BSBL) and its implementation using a beam-scanning laser diode (BSLD) are proposed. The BSBL is categorized as spatial coding information processing, which operates with spatially coded light signals. A basic BSBL unit consists of two photodetectors, two amplifiers, a light source, and a beam scanner. A unit with three output photodetectors can execute eight types of binary two-inputs/one-output optical logic operations with small modifications: FALSE, AND, XOR, OR, NOR, XNOR, NAND, and TRUE.
The refractive index of an optical glass sample in the form of a wedge is measured by comparison with that of a reference liquid. This holographic technique can also be applied to the measurement of the refractive index of the immersion liquid, if the refractive index of the glass wedge is known. The accuracy ofthe method with respect to index matching, glass wedge preparation, and fringe position measurement on the interferogram is discussed.
The relationship between the diffraction efficiency of a reflection hologram and the thickness and absorption coefficient of the recording medium was studied. The diffraction efficiency of a reflection hologram was found to increase monotonically with a decrease in the absorption coefficient a of the recording medium, but varies nonmonotonically with an increase of the thickness T of the recording medium. Maximum diffraction efficiency was obtained when T and α satisfied the relationship T= 1/α. Finally, we suggest a method to improve the quality of reflection holograms.
An objective image quality measure based on the digital image power spectrum of normally acquired arbitrary scenes is developed. This image quality measure, which does not require imaging either designed targets or a constant scene, utilizes the previously known invariance property for the power spectra of arbitrary scenes. The measure incorporates a representation of the human visual system, a novel approach to account for directional differences in perspective (scale) for obliquely acquired scenes, and a filter developed to account for imaging system noise as specifically evidenced in the image power spectra. The primary application is to assess the quality of digital images relevant to the image task of detection, recognition, and identification of man-made objects from softcopy displayed versions of visible spectral region digital aerial images. Experimental verification is presented demonstrating very good correlation (r=0.9) of this objective quality measure with visual quality assessments.
We show that global and local characteristic features of thermal images undergo considerable diurnal changes. In particular, the standard deviation of the gray-level distribution of thermal images increases with the intensity of the solar flux and the diversity of the microtopography, while the spatial correlation length decreases under the same conditions.
Imagery from infrared sensors was used for automatic object recognition using a digital simulation of an optical correlator with binary phase-only filters (BPOFs). The method was tested primarily for applications that involve objects with a nonrepeatable signature. In imagery from actual sensors, object boundaries can be poorly defined, and the same object can vary in shape significantly, depending on a host of variables. Digital image processing techniques were used to threshold gray-level images before correlation so that variations due to environmental conditions and other variables can be limited. A synthetic discriminant function made from a training set of thresholded imagery was used to create BPOFs. The potential of the recognition method was evaluated with imagery that varied in an unknown or nonrepeatable manner. The method presented here reduced the sensitivity of a BPOF to changes in an object's appearance when the object varied in an unknown way.
A new method (algorithm and computer implementation) has been developed to define the 3-D shape of a surface based on an analysis of the shadow moiré patterns of the object. The approach is based on a phase-shifting technique enhanced by the solution of a set of overdetermined nonlinear equations involving the light intensities acquired by means of the shadow moiré method. Such an approach allows the accuracy of the measurements to be improved by utilizing excess information. Because the method uses a conventional white-light source, it can be applied to measure the geometry of human faces and bodies as well as the out-of-plane surface deformation of a loaded structure. The theory of the algorithm is described, together with test results. The results obtained show that the described approach can resolve the shape of an object with an average error of less than 2%.
The behavior of the power efficiency Peff of an optical fiber with a bulk distribution of source in its cladding is analyzed. The expressions derived make use of the exact field solution of a cylindrical fiber, whereas previous work has made use of the weakly guiding approximation. Although more complicated and harder to interpret, the formulas presented allow the analysis of the power injection efficiency of fibers with arbitrary differences in indices of refraction. The results obtained are relevant to the design of more efficient optical fiber fluorosensors. The conclusions follow. Previous results using the weakly guiding approximation were confirmed. However, we have found that Peff does not always increase with the V number; it does, however, increase with the difference in the indices of refraction, ncore - nclad, and the wavelength λ. It also decreases with the fiber core radius a. Finally, a new independent variable, a/λ, was found.
The conversion factor in a CCD device is determined by the photon transfer technique in a region where pure shot noise is not dominating, i.e., where noise of the readout electronics must be taken into account. The method is based on the measurement of the noise standard deviation, dependent on the intensity of the signal and the fifing of a simple model incorporating shot noise and signal-independent noise. The result is a linear equation system. From its solution the conversion factor and the standard deviation of the signal-independent noise of the device are determined. The mean number of generated charges is determined from the measured mean signal by means of the estimated conversion factor.
An electronic speckle-pattern interferometer with a polarization phase-shift technique for the deformation measurement of a diffuse surface is proposed. A common-path optical phase-shift arrangement is
adopted in the interlerometer to improve the stability of the optical system. A polarization phase-shift technique is used to obtain precisely phase-shifted interferograms. A phase map of a fringe pattern, which is capable of distinguishing surface depressions from elevations, can be automatically and accurately obtained from four interferograms by the computer data processing. The numerical data representing the deformation over the entire field can be easily extracted from the phase map. An example of deformation measurement using this interferometer is presented.