The authors propose a method to increase the information recording density in optical storage by means of optical immersion. The influences of parameters of information carrier substrate and moving immersion liquid flow on the aberrations of information recording-reading optical channel are investigated. It has been shown that in the case of optical immersion data recording the most acceptable information carrier was a carrier shaped as an optical cylinder. The information recording in such an optical cylinder is performed on its internal surface. The recording media and the method of depositing these media on the cylinder's internal surface are analyzed. The technical characteristics for the immersion type optical storage are given.
This paper states several unique advantages of holograms as carriers of book information. After comparing several methods of book information storage, the paper draws the conclusion that holographic libraries will be the main form of paperless information storage in the future. The paper gives a detailed report on the technological preparation and series of products which the author's corporation has made in the development of a holographic library. A computer external unit -- an ultrafiche scanner -- has been researched successfully. This scanner, which is no larger than a book, can display, print, and fax book information of the ultrafiche by the microcomputer. The author considers two special technologies still needed for the widespread use of holographic libraries: (1) how to develop holographic embossing techniques to produce cheaper ultrafiche on a large scale and, (2) research a micro-personal book reader. The author regards the realization of holographic libraries as a revolution for book information storage.
Phase conjugation of a wave scattered from a real object was performed for the first time in the geometry of a double phase-conjugate mirror using a photorefractive crystal with the sillenite structure. The variation of intensity of the phase-conjugate wave is studied under different conditions of observation. The possibility to use this geometry in interferometry is discussed.
We have studied that the dynamic behavior of our national products Bi12SiO20, Fe:KNbO3, etc., for real-time holographic recording and display. The potential applications of these crystals to image storage and freezing, real-time interferometry, and optical switching are described. The results of experiments are also given.
The practical feasibility of designing an integrated optical head for disk holographic memory has been studied. Computation procedure for topology design of refractive waveguide lenses and planar optical systems has been developed. Fundamental factors causing the bit rate limitation when recording the information on the optical disk of a planar head have been revealed. A prototype of a 12-bit head has been fabricated and experimentally investigated.
Systems for reading data from optical disks are suggested. In these systems a diffractive lens simultaneously executes the functions of a focusing objective and the dispersive element of dynamical autofocusing device. The design of diffractive lens structure is given for two cases. In the first case the objective focusing semiconductor laser emission consists of a single diffractive lens. In the second case, it consists of a diffractive and homogeneous lens with spherical surfaces. When designing the diffractive lens structure, one must consider that semiconductor lasers have a heat instability of emission frequency and emission wavelength spread from one sample to another.
In this report, two modified models of artificial neural networks based on the Hopfield model are suggested. The composition of the memory matrices is revised for the models and an optical system constructed with a spatial light modulator PROM is set up to implement the models that are executed by computer simulation. The experimental results show that the storage capacity and the searching-identification of the neural network for associative memory are improved.
A real-time optical associative memory, which uses the self-pump PCM as feedback and a thresholding operation device, is developed in this paper. The memory uses the He-Ne laser as a light source instead of the Ar+ laser. It can recover the complete image desired even though the input information is only 25% of a stored object.
In this paper we discuss recent advances in holographic data storage using ferroelectric SBN as the recording medium. A novel optical architecture involving an array of SBN fibers is discussed that allows 2 - 3 orders of magnitude faster access times than for conventional magnetic data storage devices of Gbyte size. To realize this potential we are studying fundamental materials issues related to SBN fiber growth and photorefractive processes underlying prolonged readout in SBN.
We have for the first time used four-wave mixing to determine the maximum angle of deviation of the reconstructed wave from a crystal volume grating under conditions departing from the Bragg's low. The result shows that there are limitations when the traditional coupled- wave theory is used to interpret the crystal volume grating.
Several multifacet holographic elements have been fabricated using dichromated gelatin. A two-dimension associated memory system has been achieved in which the holo-lens array is used as the interconnector and a liquid-crystal elevision is also used as a programmable two- dimensional spatial light modulator. The experimental results have been demonstrated.
A three-layer neural network implemented by optical and electronic techniques for pattern recognition is described in this paper. The principle, the architecture, and the experimental results of the hardware system for pattern recognition are presented.
Holographic optical elements such as holographic filters and holo-lenses have been fabricated in methylene blue sensitized gelatin (MBG) and dichromated polyvinyl alcohol (DCPVA). Holographic filters fabricated in MBG exhibit high diffraction efficiency (approximately equals 90%) at low exposure energy of approximately equals 46 mJ/cm2, while holo-lenses fabricated in DCPVA have approximately equals 60% diffraction efficiency.
Techniques are described for the design and fabrication of a holographic field-lens (HFL) which is made at 0.488 micrometers for use in the red or infrared light. The HFL has low aberration and large field of view under the Bragg condition. The nonlinear terms are eliminated by the two operations when the holographic filed-lens is used for measuring the angle of a monochromatic beam.
An eye holographic recording method with wide-angle illumination of fundus without using cornea contact lens and optical fibers is presented in this paper. A clear holographic eye image in full depth, keeping the original refraction state and illuminating a large area of fundus, was reconstructed from the hologram. In order to avoid problems in arranging and adjusting the optical components, a special-purpose holographic optical element was developed which allowed the eye holographic recording to be implemented with only one collimated beam.
This paper analyzes the noise caused by the quantization effects of computer generated holograms (CGHs). To utilize a fabrication that is compatible with VLSI processing techniques, a CGH having only two levels of phase is fabricated. The binarization not only reduces the maximum efficiency of CGH but also causes some optical noise which may lead to signal crosstalk. The maximum deflection angle of CGH is determined by the smallest written spot of the hardware. The divergence angle of semiconductor laser signal transmitter causes a decrease of the maximum deflection angle of the CGH. Here we present a way of increasing the maximum deflection angle by using the divergence angle of a semiconductor laser.
The possibility of fulfilling integral transforms of coherent light fields by phase diffraction gratings was studied. To realize the family of Hilbert integral transforms in a prescribed diffraction order, a binary grating consisting of two parts of equal width but different cross size-to-period ratios of rectangular grooves was suggested. Grating geometries permitting the Hilbert transform with the maximum intensity concentration to be performed in a given diffraction order were described. The mapping effect of the integral beam images in Fresnel zones of the suggested phase gratings was discovered. The observation conditions and possible ways of using the effect are also outlined.
Recent developments in China on holography applications are discussed, including the International Conference on Holography Applications in 1986, display holography, and new HOEs, as well as other important developments and events.
The concept of holographic optical pixel (HOP) used for large screen displays is proposed in this paper. The complex holographic optical elements in HOP and off-plane filters have been designed. The HOP has a higher utilization of light energy than optical pixels and large color space compared to the conventional optical pixel and the CRT color pixel. The experiment results are satisfactory.
A polarization holographic method which allows us to reconstruct the polarization state of an object wavefront along with phase, amplitude, and frequency has been described. The theoretical grounds of the method and its possible applications to different problems has been discussed.
The physical principles and methods of creating dynamic photopolarized medium for holography are considered. The medium is based on the phenomenon of the electron photopolarization of the oriented charge-transfer complex molecules. The photopolarization transforms the molecular complexes with life time 10-4 - 10-9 s into ion-radical form. It is shown that such photopolarizated medium can achieve speed of response equal to 104 - 108 Hz by high values of the photosensitivity (106 cm2/J), the resolution (1000 mm-1), and the diffraction efficiency (34%). The medium is of interest for creation of an optical computer's memory, optical memory for real-time correlative information processing, formation of interconnections in optical neural networks, and light beam control.
Holography with a red sensitive photopolymer system is described. Our photosensitive medium is composed of a sensitizer, initiator, monomer, inhibitor, and polymeric film- forming binder. This is a type of phase holographic recording material, using wet developing and fixing method. The material has high diffraction efficiency, high resolution, and higher sensitivity. It possesses advantages of both silver plate and dichromated gelatin plate.
Recording-readout processes in real-time scale for amplitude-phase gratings are investigated in monolayers and multilayer structures made from light-sensitive chalcogenide glasses As-S(Se). Effects of image relief relaxation and stabilization are considered. They are operated by a layer composition, temperature, or formation of multilayer structures, which are similar to superlattices.
Until recently, the paradigm of computing was the Turing machine and its numerous equivalents. All operations are made with state machines. Each operation is irreversible and brings about an increase of entropy and, therefore, an expenditure of energy of at least kTln2 per bit. We show that optics allows the first practical quantum mechanical digital processors. These processors require digital input and produce digital output but need no intermediate state machines. We show that, in the sense of not requiring material devices which would otherwise be required, nothing is superior to something for computing.
We describe an opto-electronic hybrid system with the programmable LCTVs for implementing binary logic operations. A digital optical adder is constituted by a polarization encoder and Wollaston prisms.
Compact optical logic unit and ripple carry adder method have been proposed and demonstrated. It can be easily controlled and its structures are compact. The processors can do parallel data series instruction flow operations.
In this paper we consider the problems of realizing an optical associative memory for use in new generation supercomputers. The problem of creating a fast high-capacity associative memory is solved by combining several associative memory modules into the whole system.
A new design of the correlation filter is proposed. The spectral iterative technique and the Fourier-Mellin descriptor are used in the filter design. Targets are detected by rotating this filter in the Fourier plane to determine points of constant intensity. The results of computer simulation show that distortion (translation, rotation, scale, and intensity) invariant pattern recognition can be achieved.
A hybrid optical-digital system consisting of a holographic mask, two lenses, a CCD detector, and a microcomputer is presented to compute the invariant moments of images in real-time. Some English letters are tested as input patterns to extract invariant moments. Experimental results show that the invariant moments of a letter are largely independent of shift and rotation, and the moments are distinct with different letters.
On the basis of hybrid optical-digital power spectrum analysis methods and statistical pattern recognition technology, the pattern recognition method of the dactylogram and similar items are investigated. Two class fingerprints with different dactylotype were studied experimentally. The experimental results are satisfactory.
In this paper, we developed and demonstrated a liquid crystal light valve and photorefractive spatial light modulators, utilizing these devices to build up a real-time correlation pattern recognition system. The performance parameters of these devices were measured, and some of the experimental results are given.
An optical fiber holographic interferometric geometry with a single optical fiber (single-mode or multi-mode fiber) for both object illuminating and reference beams is described in this paper. Also given is the effect of the laser speckle field emitted from the optical multimode fiber on the resolution, diffraction efficiency, and the contrast of the interference fringes of the hologram.
In this paper, the dependence of measurement accuracy on coherent degrees is described, with some comparison of imaging quality evaluation using coherent and incoherent processing. The results of measurements are presented.
In this paper, the method for the electro-optical information processing in the heterodyne profilometer we have made is described. It is based on optical heterodyne interferometry and phase detection techniques. Height variations are less than 1 nm and lateral resolution is less than 2 micrometers . More than ten parameters of surface roughness could be calculated and a real profile of the measured surface could be obtained.
Fringe scanning technique is widely used to test the shape of optical element surfaces. In this paper, a method of image information modulation and processing for a fringe scanning optical profile used to measure surface roughness of precision machinery parts is presented. The reference mirror of a classical Linnik microinterferometer is driven by a piezoelectrical transducer (PZT) modulated using saw-wave, and the phase of interfering fringe is shifted linearly. The image data acquisition system, including a CCD array, PZT, DMAC6844, AD7820, has realized high synchronous data sampling frequency of 250 KB/sec and 10 bit A/D converting. The experimental results show that the converted Linnik microinterferometer can measure the roughness of precision surface where Ra is less than 0.01 m and obtain various standard parameters of roughness. Therefore, the function and precision of the instrument could be enhanced significantly.
An optical fiber holographic endoscope (OFHES) has been developed, in which the reference beam, illuminating object beam, and the image of the object are transmitted by a single-mode fiber, a multimode fiber bundle, and a multimode fiber image bundle (MFIB) respectively. The resolution of OFHES is 30 lin/mm higher, field depth 30 mm more, and measuring range 30 X 30(mm)2 larger. Based on understanding the image transmitted characteristic of MFIB, we describe the effect of the multimodes and crosstalk in MFIB on the hologram recorded in the system by the OFHES.
For the purpose of measuring strain field in the vicinity of a crack tip accurately, a novel grating strain method based on the diffraction analysis is presented in this paper and an electro-photo detection system is developed. The experimental results show this method is reasonable and practical.
A new laser illumination receiver has been developed. This receiver is made of a holographic lens and a position sensitive device. The parameters of holo-lens are acquired by ray tracing. The field of view of the receiver is 45 degree(s) in the horizontal, 34 degree(s) in the vertical. The resolution is 0.2 degree(s) in the horizontal and 0.2 degree(s) in the vertical. This receiver has the features of a simple structure, low cost, and large field of view.
An optical measuring system with high precision, high speed, and a simple configuration is introduced. The surface profile of a 3-D diffuse object is obtained by measuring the phase of the intensity distribution deformed by the surface. The phase-shifting technique is performed with an electro-optic modulator, with a CCD used to detect the distorted images and a 286AT computer to process the data. The experimental result of a mannequin head is presented, which shows that a range up to 10 cm and a resolution better than 0.065 mm are available.
A forward scattering particle image velocimetry is presented in which a low power cw laser and a band pass filter are used. The experimental results measuring the rising velocities of oil droplets of low density are given.
This paper presents a method of real-time processing to retrieve the wavefront distortion in single-pass with optical phase conjugation. The wavefront only passes through the phase distorting medium once.
Some results on theoretical and experimental investigation of acousto-optical devices based on paratellurite single-crystals are presented. The operation principle of the devices is based on optical beam diffraction by acoustic diffractional gratings in TeO2 during a non-collinear geometry of interaction as well as in near-collinear regime of scattering. The devices use light diffraction on shear acoustic waves propagating along (110) axis of paratellurite and close to this direction. Depending on the directions of acoustic and optical beam propagation in acousto-optical cells, three regimes of acousto-optical interaction were realized with different selectivity of Bragg anisotropic scattering. Some peculiarities of device operation are analyzed in the paper and possible applications of the acousto-optical devices for optical information processing are discussed.
An acousto-optic system containing opto-electronic feedback through diffraction maxima of different orders is investigated theoretically and experimentally. Taking into account nonlinear characteristics of generalized view, the existence of bistable state are found in the system. Peculiarities of three regimes of system operation with switching by electrical or optical impulses or by frequency change are studied. A possibility of realizing a multistable regime is demonstrated.