SU1513519A1 - Device for searching for data in holographic memory with moving carrier - Google Patents

Abstract

The invention relates to the field of computer technology and can be used in solving information retrieval tasks using a holographic memory. The purpose of the invention is to increase the speed of the device. The device comprises a read light beam forming unit 1, a light beam scanning unit 2, a moving medium 3 with an array of holograms, a restoring lens 4, a two-dimensional spatial light modulator 5 to set the source data for the search, an anamorphic lens 6, a multi-element photo receiving unit 7 and an electronic unit 8 data processing. Accompanying the moving holograms with light beams allows for a tenfold increase in the time for reading information from the carrier without distortion, without reducing the speed of the carrier. 2 Il.

Description

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The invention relates to a computing technique and can be used in solving information retrieval tasks using a holographic memory.

The aim of the invention is to improve the speed of the device.

Figs 1 and 2 in two projections show a schematic diagram of the device.

The device contains a unit 1 forming light beams, a unit 2 scanning light beams, moving. a hologram array 3, a restoring lens 4 with a focal distance F located at a distance from the hologram plane, a two-dimensional spatial light modulator 5 for specifying the source data for the search, located at the focal distance from the lens 4 , anamorphic lens 6, having focal lengths F, (and Fu. on the orthogonal coordinates X and Y, set at a distance D from the ICP; multielement photoelectric block 7., installed at a distance D from the anamorphic lens and the electronic unit 8 processed These data, moreover, the distance D 1 and 1), 2, satisfy the conditions 1 / D + 1 / 0.2 l / F, j.5 and the distance D between the plane of position of the bare gram and the restoring lens is equal to

 (Di - Fx) -F2

D F +

D, D2- (,,) F,

The device operates as follows. The light beam forming unit 1 forms N parallel light beams lying in the XZ plane. Such a unit may consist, for example, of N lasers or of a single laser and a light beam splitter providing foplofraction of N parallel Swat beams of the same diameter and equal power. The light beams are then passed through the light beam scanning unit 2 and illuminate a line of N moving in the direction of the holograms in the memory module 3, so that each light beam illuminates one hologram. The memory module 3 may be implemented, for example, in the form of a rotating optical disc or drum or a moving tape.

or plates with holograms placed on them. The unit 2 for scanning the light beams parallelly displaces the illuminating light beams in space along the y coordinate synchronously with the movement of the hologram along this coordinate so that during the movement of the holographic module 1-1 of the memory module 3 in the direction of the N line of the hologram remains fully illuminated during the interval time T D / V, where D is the size of the hologram, V is the speed of movement of the hologram and the light beam illuminating it in the y direction (during this time the scanning unit of the light beams follows the line eki of N headings {reading light beams). Then, the unit 2 for scanning the light beams deflects the illuminating light beams to its original position to begin tracking the next line of N holograms placed on a moving medium close to the previous line of N holograms, etc. The unit 2 for scanning light beams can be performed, for example, on the basis of optical radiation deflectors (electromechanical, acoustic, or the fastest - electro-optical). During the time interval T, the images of the data pages, needing a kind of matrices of dimension N ,; N (, reconstructed by lens 4 simultaneously with each of the N illuminated holograms and aligned in the plane of the ICP 5. The location of the images of data pages does not depend on the displacement of the holograms during movement, since the holograms are Fourier holograms and their registration is performed in a scheme with parallel light beams As an ICP, various controlled transparencies (acousto-optic, liquid crystal, etc.) can be used, which provide modulation of the reading light beam in intensity. The source data for the search is the query word, which is also represented as a matrix similar to the image of the data page recovered from the hologram. The query word has K NX Nu binary bits and is set to the ICP as a matrix of dimension N, where N and NU are according to the number of columns and page

5 15 matrices. The images of the data pages at the output of the ICP are modulated according to the query word. Anamorphic lens 6 is used to integrate the resulting light distribution over the X coordinate by projecting the image of each of the N holograms onto its column of photodetectors 7 along this coordinate. The dimension of the multi-element photoreceiver 7 (N) X. (NU) elements. According to the Y coordinate, the light fluxes are separated in the plane of the photodetector 7 in accordance with the positions of the NIP lines of the query with the query word (matrix) assigned to them, since the coordinate of the ICP plane is projected into this position of the photodetector. The condition that sets the mode of projection of the ICP plane to the photodetector plane along the Y coordinate is determined by the ratio 1 / D, + 1 / D I / FU. According to the X coordinate, the projection of the hologram plane in the photo-receiver plane is carried out by two objectives 4 and 6, which is achieved when the ratio

(Br - FX) D

D F +

D, (D, + D2) F /

The resulting light beam, corresponding to each individual hologram (each data page), is distributed to the photodetector column corresponding to this heading e, consisting of Nu photodetector

items. Signals from each of these

the photodetector elements are proportional to the scalar products of the corresponding rows of N bits of the matrix with the query word and the matrix representing the data page. The consistency of the NN signals from each column of Pi photodetectors completely determines the scalar derivative of the two K-merp vectors, but is represented as a set of NU partial scalar products of fragments of these vectors of length II. bits each. Since the line from the individual holograms is read at the device input, i.e. if one-time data page is restored, then at the output of the multi-element photodetector 7 N scalar products of different

5 0 5 About

0

. ,

K-dimensional vectors with one K-dimensional

query word, presented in the form of N groups of signals corresponding to N columns of photodetectors. The Kazkdoy of scalar products is represented by a group of Nu signals taken from individual photodetectors corresponding to partial scalar products of fragments of these vectors, with a fragment length of N bits. In case paraphase coding of data recorded in a holographic memory (a memory module with an hologram array) is used, i.e. 1 is represented by a combination of bits 10, and O is a combination of 01, and the inverse paraphase coding of the query word (1 corresponds to 01, and O is 10), then if the data corresponding to one hologram coincides with the query word, the scalar product corresponds to K-dimensional vectors takes a zero value. The partial scalar products of the fragments of these vectors also take on zero values. As a result, with N | i photodetectors located in the column corresponding to such a hologram, bullet signals are removed.

In the electronic data processing unit, a logical combination of NU signals is taken from each of the columns of a multi-element photo-receiver. The result of such a logical union is represented by a U-dimensional vector (word), the numbers of the zero components of which unambiguously determine the numbers of the corresponding holograms containing the data pages that matched the query specified in the ICP.

The time T, during which images of data pages can be restored, from the same moving hologram line in the proposed device, is substantially longer than the time during which data from the holograms in the known device can be read. This is due to the fact that in the known device there is no invariance to the displacement of the holograms, since the plane of location of the holograms and the plane of the photodetectors in this device are optically conjugated. As a result, when displaced (moved) by the head, their images are 715

They are transmitted from photodetectors, which leads to distortion of the output signal from the photodetectors and thus to the limitation of the time during which a light signal can be produced. Thus, in a known device, the time during which holograms are available for reading information from them is only a few percent (1-2%) of the time of change of holograms T (from the time during which the hologram shifts by a distance equal to its size). The use in the device of the scanning unit of the light-emitting beams 5, similar to that used in the spun device, does not give any polmmeltelno effect.

since it allows increasing

At the time of illumination of the same film, but it does not eliminate the effect of displacing its image from the photodetector element, and hence the effect of distorting the signal from the photoreceiver. In the proposed device, the plane of the holograms is projected into the plane of the photodetector only along one coordinate X, in the direction of which the holograms in the memory module (and hence their images along this coordinate in the plane of the photodetector) are not displaced. The holograms in the memory module are shifted (moved) only along the y coordinate (accompanied by light beams using the scanning unit 2 also along the coordinate y), and since in the plane of the photodetector 7 along this coordinate the plane of the W1C is projected, where the pages with holograms and since the characteristics of the light distributions reconstructed from the holograms do not depend on the displacements of the holograms themselves (the Fourier holograms are used), the coordinate y in the plane of the photodetector also does not change and light distributions due to the movement of the hologram along this coordinate. Thus, in the proposed device, in contrast to the known invariance of the displacement of holograms along the coordinate y, resulting in the movement of holograms with light beams, carried out using a scanning unit of light beams, turns out to be effective because

Q

0

5 5 5 0

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Claims (1)

It increases the time during which the information from moving holograms can be read without distortion without reducing their speed of movement. During this time, not a single query can be specified on the ICP, but a whole sequence of M queries, differing in, for example, different masking options for any word word in the query. As a result, the performance of the device increases M times in comparison with the known. Invention Formula A device for searching data in a holographic memory with a moving medium, comprising a block, forming light beams, a moving medium with an hologram array, optically coupled through a restoring lens with a two-dimensional spatial light modulator, a multi-element photo receiving unit whose output is connected to the input A data processing unit, the output of which is an information output of the device, characterized in that, in order to increase the speed of the device, a beam scanning unit is inserted into it and an anamorphic lens, the output of the light beam forming unit is optically coupled to the input of the light beam scanning unit 5 whose output is optically coupled with the moving carrier of the hologram array, the anamorphic lens is optically coupled with a two-dimensional spatial light modulator and a multi-element photo-irradiating unit and placed from them at distances x that satisfy the condition 1 / D, + I / Da 1 / F ,, the restoring lens is mounted from the plane of the moving carrier of the hologram array at a distance D D F + D, DQI - (D, +0) FX where F is the focal distance of the restoring lens; D is the distance from the anamorphic lens to the spatial light modulator; - DO — distance from the anamorphic lens to the multi-element photodetector unit; F, FU are the focal lengths of the anamor-photon lens along the orthogonal coordinates X and Y. Editor G. Gerber Compiled by S. Semutsevich Tehred L. Oliynyk Proofreader N. King Order 6088/52 Circulation 558 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 "M to Subscription