DE2045080B2 - Method for storing holograms - Google Patents

Description

ty -ο _r j, light beam on a beam splitting mirror

The foundation relates to a process for dividing the food and using a diffusion lens on top of it of holograms with an information area of a transparent object (e.g. a Storage disk containing several holograms, the information disk) to scatter (electronics, 1968, due to the mutual interference of a body light booklet 6 S 182)

Beam and a reference light beam are formed, the object of the invention is to provide a

rfct! μ P ¹ T- ^ TT ^Bestra Wung the reference 40 drive to save holograms to scha '

light beam is reproduced on the holograms. that is able to record holograms without the Vc ₁ -

τ ^ f? ^D u ^{em Cor} P ^{he attachments} arrive outside of a coherent application of a Lichtablenkanordnune to reproduzie light beam is disposed, the light beam is r. This is bent in the procedure mentioned at the beginning and a signal wave is formed, which is resolved by the fact that the reference light beam is formed as an iniormationm with regard to the shape and the position of the reference wave which contains the body information corpus and deviating * LT ^S % ·? a = Sestrah t, interferes the reference signals are allocated, and that, without distraction "PKW reference wave to an interference effect of the reference light beam to produce only the information area, and this interference zone can signal of a single, dasBezuessignal and Shlna ^Tr ° ^CKEN , ^{pla "e} photographed be. A hologram 50 of the beam body formed repro-hologram of this drying, by developing is duced

feuchtefw !! - ^d d ^et w ^V rH ^rd H ^en \ ^Wen f 1f ^{S Holo} f ^{amm be} "Preferably the reference ^{signal is reproduced by a SpTr 0} Ih η signal wave and given assignment signal plate that includes the body in real B ₁ Id and a virtual image are emitted by corresponding information and one imagines the Te2 ΐΤ ^8? ^ ^ ^{1? 3} ™ ^{5 gG "55} Sang signal controller Alloc-T IAE ^nS if ^the GERSTEL receives voltage signal and the transmission factor

^{ird all8e} S ^ ^{d Stdl d} ZdUll

?! / IF ^icheran - The following is the principle and then

rente1 nlS »ir ^P '* the transparent ⁶ ° an embodiment of the invention described, b iiSiS I · S ^ chneben, a hologram is through an interference area

rpers used and that of a Signalwellft d i B llf

turn off thieiSinS I · S ^ chnext are, a hologram is through an interference area

at, mile of said body used and that of a signal wavefront and a reference wavefront

g & JE ^ iT ¹¹¹ UW ¹¹⁰ ; f ^{rd at a 40} ^ t ^{and a} signal wavefront is reprZ-

Control of the storage disk is formed and then it is decorated if one of the reference wavefronts is identical

3S5

while according to the invention a reference signal accordingly an information disc to the Be ^ igswelle is given. A plurality of holograms is saved on an information storage disk the movement of a sheet mask is formed, each hologram being formed by an interference region of an information signal wave from an information disc and a reference signal wave corresponding to the information disc is being built. A reference signal is applied to the entire area of the information storage disk thus diffused by a diffusion lens in front of the associated signal plate emitting the reference signal that a hologram passing through an interference region of the information signal wave and the reference signal wave is constructed can be formed on any area of the information storage disk. It is necessary to form a hologram in a designated address. Different information signals are stored in the holograms formed in this way and various reference signals v.esden also added to the holograms. When reproducing, therefore, an information signal can from the Hologram formed by the signal identical to the reference signal can be reproduced, by using a reference signal to the coherent reference light by any assignment signal the diffusion lens and the assignment signal plate to illuminate the entire area the information storage disk is pushed.

Thus, the essence of the invention lies in the fact that in the formation of holograms scattered reference signal waves, which are different from each other, are used and scattered in reproduction Reference signal waves are radiated to reproduce only the information signal from the hologram, which is constituted by the same reference signal and the information signal wave.

The invention employs the principle of the information conversion operation. Assuming that a Fourier transform hologram is reproduced by using a Fraunhofer diffraction wave of a body of c (w, v) by using a Fraunhofer diffraction wave of the information disc of α (w, v) as an information wave front and a Fraunhofer diffraction wave of the assignment plate of b (u, v) is applied as the reference signal wavefront, where a, b and c have real amplitude distributions, the direct image ad ' and the conjugate ac' of α (κ, ν) can be expressed as

ad ' - a (#) (b * c) and ac = a * (a (#) c),

where * the correlation and (*) the convolution integratino are.

Similarly, bd ' and bc ¹ of b («, v) can be expressed as

bd ' = b *) (a * c) and bc' = b * {a @ c).

Therefore, α is reproduced as the direct image when b * c = ö (<5 is Dirac's ύ function), and b is reproduced as the direct image when a * c - ö. When α and b have structures that are close to are arbitrary, b is reproduced in other words, when the lighting is formed by the diffraction wave of α wirdj Urid α is reproduced when the lighting is performed by the diffraction wave of b. According to the invention, of course, a hologram is produced by the diffraction waves of α and b , and α is reproduced by the diffraction wave of b. However, the invention must be distinguished from the simple information conversion process, although the invention uses the principle of information conversion. According to the invention, holograms! made by changing b for each α , unc then an arbitrary b is given and α becomes au; the hologram reproduced, which is formed by the b to said identical b.

Thus, the invention differs from the known method in that the requirement! the use of a deflection arrangement in reproduction can be completely avoided there the formation and reproduction of the hologram! through the use of an allocation signal platform can be executed.

Details of the memory arrangement emerge from the following description of an exemplary one Embodiment with reference to the drawing, in which are

F i g. 2 is a perspective view of the main part: the storage arrangement,

F i g. 3 α and 3 b are perspective views showing a method for forming holograms with an allocation signal plate having different light screen patterns corresponding to the information plates,

F i g. Fig. 4 is a perspective view for explaining the process of reading the information au; the memory arrangement according to FIG. 2 and

F i g. 5 is a perspective view of an allocation signal plate; used in the memory array.

Referring to FIG. 2 is the formation of holograms, i. H. the writing of Informa functions.

A beam 7 of coherent light from a laser light source 6, such as a helium-neon gas laser is divided into two beams 9 and 10 by means of the amplitude dendivisicn by a half mirror 8 and de beam 9 is enlarged by the magnifying lens 11 and then converted into a parallel light beam directed to the information plate 13 by the collimator lens 12, whereby the information signal waves are formed. The information plate 13 can be, as in the known Vorrichlunj a glass plate at the designated locations, au the codes written from black dots who the. In front of the information disc 13, a diffusion lens 14 suitable for de information disc 13, such as a scanning beam lens for scattering the informa tion signal waves from the information disc 13 to the information storage disc 15, is provided. In the storage device, it is made possible to provide the diffusion lens 14 and the information disc T.

On the other hand, the laser beam 10 generated by the Amplitudendivi sion through the reflector K reflected, enlarged by the magnifying lens 17 and converted into a parallel light beam delt assigned to the assignment signal plate 19 by dii Collimator lens 18 is directed, whereby the Be reference waves are formed. Thus, the result is light source 6, the half mirror 8, the magnifying lens 11 and the collimator lens 12 an apparatus Forming a coherent beam of light that leads to the In formation plate is directed, and the laser light

2 0454080

source 63 of the half mirror 8, the reflector 16, the magnifying lens 17 and the collimator lens 18 provide a further device for forming a coherent light beam which is directed towards the assignment signal plate. The transfer factor or s refractive index of a particular portion of the ZuprdnungssignalpläUe 19 is changed when a Zuprdnuagssignal is received from the input control device 20 by the allocation signal plate 19, and the Zuordnüngssignälplatte 19 10 'then outputs a reference signal to the reference time of the coherent light beam. The input signal controller 20 generates various allocation signals corresponding to a plurality of information discs. In the in F i g. Allocation signal plate 19 shown in FIG. 2 is shielded from light by the oblique line portions by the application of a voltage between opposing electrodes out of the electrode groups 21 and 22 provided on the plate. In the present example, the reference signal is given to the reference paths of the coherent light beam through the patterns of the shielding portions represented by oblique lines. The diffusion lens 23 is arranged in front of the assignment ^{signal plate 19, so that c 1} is the reference signal can be scattered over the entire surface of the information storage plate. B. can be used as diffusion lens 23, since the Lichiabschirmabschnitt the assignment signal plate have the structure of a Longitudinaibar.Jes. It is actually possible to use a scanning beam lens as the diffusion lens 23. S <^ ~ iit interferes with the information signal wave mn the reference signal wave and eii; Hologram 26 is formed on the information storage disk 15 constituting the amplitude hologram, the interference of the information signal wave being carried out through a hole 25 in the leaf mask 24 provided immediately in front of the storage disk 15. Signal light beams of the information disc 13 and the extension signal plate 19 are all contained in the hologram 26. A plurality of holograms 26 are formed at different locations on the information storage disk by moving the sheet mask 24 along a plurality of information disks. When an information disc 01 is provided, as shown in FIG. 3 a, the allocation signal disc has a pattern R 1 and a hologram P 1 is formed on the information storage disc 15. When an information disc 02 is provided. As shown in Fig. 3b, the assignment signal disk has a pattern R 2 and in this example the sheet mask is shifted to the right in the drawing and the hologram P 2 is formed on the information storage disk 15. Thus, the association signal disk has different patterns corresponding to the information disks, and a plurality of holograms are formed on the information storage disk 15.

In the case of the storage arrangement, the sheet mask used for forming the holograms can be moved provided along the information discs and is, as described above, immediately in front of the Information storage disk arranged when writing the information. The information storage disk is provided with a light-sensitive layer on which amplitude holograms and phase holograms can be formed. Many photosensitive materials developed so far can be used for this purpose be turned. In general, a photographic dry plate can be used and also a photochromic glass can be used. This photochromic glass was made by Cqrning Com pany, USA, and the use of this glass can make a semi-solid storage device * because a hologram is created by the application of light with a greater wavelength al the coherent light used in forming the hologram can be erased.

The reproduction of the holograms in the storage device, ie the reading of the information from the storage arrangement, will now be described with reference to FIG. 4 described. The arrangement of the F i g. 4 is part of the arrangement according to FIG. 1 and is provided with a device for finding the reproduced image from a hologram. This finding device is part of the storage device.

The wavelength of the reproduced light can be different, but the direction of the reproduced light falls Light on the information storage disk 15 to preferably with the direction of the be the reference signal wave used in forming the hologram. For the sake of simplicity The structure, the shape and the position of the arrangement according to FIG. 4 can therefore be completely identical the arrangement of FIG. 2 can be made. There; reproduced light can be from a laser oscillator source 6 of FIG. 2 can be obtained from the oscillator source 6 laser beam 27 picked up and reflected by the reflector passes through the magnifying lens 17 and the collimator lens 18 u: i.J is converted into a coherent, parallel light beam which is directed towards the allocation signal plate 19 and is diffused by the lenticular lens 23. The allocation signal plate 19 receives a Allocation signal from the input signal controller 20 and a particular pattern is created on the band-shaped light screen portions of the assignment signal plate 19 formed.

The coherent light beam, to which a reference signal is given via the assignment signal disk 19, is given onto the entire surface of the information storage disk 15, which has a plurality of holograms, the reference signal waves given via the assignment signal disk and the information disks in the above-described writing process given information signal waves are formed. A reproduced image 28 can be formed only from the hologram Pc formed by the reference signal wave to which a reference signal identical to the reference signal has been given and the information signal wave from the plurality of holograms. This reproduced image 28 is a real image of the information disc 13 giving the information signal. In fact, a virtual image can also be formed, and in this case, a virtual image can be formed through a lens. A retrieval device such as a photoelectric element matrix 29 for retrieving the reproduced image is provided at the position where the reproduced image is formed, and the signal retrieved by this retrieval device and the address of the signal are e.g. B. transferred to an electronic computer. An information processing

2 045 # 8O

processing at high speed is made possible, by coupling the storage device to an electronic calculator. In this In the event, the input control device 20 is controlled by the electronic computer. Preferably wild an integrated circuit as a photovoltaic one Element matrix used. Thus, the need may the use of a laser beam diffraction arrangement in the reproduction completely excluded '. The problem of precisely controlling the laser beam deflector can be solved and the manufacture of the holographic memory device can be facilitated.

The allocation signal plate will be described in detail with reference to FIG. After this Reading a voltage between opposing electrodes 21 from the by an electronic Computer controlled input signal control unit 20 is held between the electrodes Signal cell 30 optically opaque and a spatial filter is formed. The pattern of the spatial filter can be done arbitrarily by the financial sisnal controller being controlled. Polarized lenses can also be used.

In the case that the allocation signal plate is applied to the above-mentioned embodiment a polarizer 31 and an analyzer 32 can be attached to the rear surface and the front TTa> hc of the 7uordnunsssisnn1plaite provided wtrden. A stick-shaped piece, rbs dii'ch Cutting lithium niobate in front of lithium tantalum in a direction vertical to the Γ axis is pebiid. can be used as a Sisn; sl cell 30 and a electrically variable filler with high speed can be produced by applying an electric field that is higher than the voltage sake Is the wavelength at the Y-face or the Y-face. Voltages of 2Q00 V and 25OOV are respectively to the sisnal cells made of lithium niohar and titanium tantalate with a length of 1 cm, if the Sirnal / ellen are in the Retricbsstatus.

In the case of the assignment table 19, as above described, based on the reading of a voltage no between eeeeniibe. -leemden electrodes T icht by the signal vial held between these electrodes 30 shields. i.e. the signal cell 30 becomes optically opaque and a special reference signal becomes the reproduced light of the coherent light through this light screen pattern eeccbfi The particular reference signal cannot be obtained just by changing the transmission factor of a particular Place of the signal plate is changed, but also by changing the refractive index of the particular Place the signal plate. The index of refraction a particular position can be changed by z. B. an ultrasonic wave oscillation in a particular Sisnal cell is effected. Although d ^ e Allocation signal plate 19 is referred to as a signal plate is "to explain that the allocation signal plate 19 contains all the light modulators, which Assignment signals received from the input signal control device 2 * 0 and output special reference signals.

In the memory device, it is also possible to use a convex lens with a set focal length between the information disc 13 and the storage disc 15 and another convex lens with to provide a set focal length between the assignment signal plate 19 and the memory plate 15, around a Fourier transfer formatipnsholoJlram to build. In this case the lenses can be between the mapping signal disk and the storage disk graze away during reproduction.

A memory arrangement with which very good results can be obtained has the following qualifications:

ίο 1. A holographic storage arrangement contains a device for forming a coherent light beam which is directed onto an information plate and an allocation signal plate, a plurality of information plates with information signals which are provided within one of the coherent light beams, a convex diffusion lens, the rear .M ^- an information disc and is arranged at a distance of the focal length / from the information disc, a diffusion plate of a coherent light beam for scattering a reference signal wave on the whole area of an information storage disc, an allocation signal split. where the transfer factor or the refractive index of a particular point of the Ziurdnuigssignal-

plate on the basis of the receipt of an assignment signal from an input signal control device according to each information plate is changed to a reference sign

to give another coherent ray of light,

an information storage stick for forming of a hologram with a scattered information signal wave from an information plate and with a scattered Bezusssignalwellc of

of the assignment signal plate, an Eilattmaskc.

provided in front of the information storage disk is for sequentially forming sheet holograms on the information storage disk by moving along the

mation plates. a locator.

provided behind the information storage disk for finding a reproduced image from a single hologram formed with a reference signal wave. which is identical to the reference signal wave. and a convex lens which is provided in front of the finding device and at a distance of the focal length f from the finding device.

2. A holographic memory array contains a device for forming a coherent Light beam directed onto an information disc and an allocation signal disc, a diffusion plate of a coherent light

Beam, the λόγ arranged an information disc is around an information signal wave to the entire area of an information storage wave to scatter, a plurality of information disks, the information signals on-

point and successively behind "a diffusion lens Are provided a convex diffusion lens behind an information disc and is arranged at a distance of the focal length / from the information disc, a diffusion

plate of a coherent beam of light to the

Scattering a reference signal wave over the entire area of an information storage disc, an allocation signal plate, whereby the over-

409521/309

factor or the refractive index of a specific location on the assignment signal plate Reason for receiving an assignment signal from an input signal control device accordingly each information disc is changed to provide a reference signal coherent to the other Light beam to give an information storage disk for forming a hologram with a scattered information signal wave from an information disc and with a scattered reference signal wave from the assignment signal plate, a sheet mask placed in front of the information storage disk to successively flash holograms on the information storage disk by moving longitudinally of the information discs to form a retrieval device behind the information storage disc is provided for finding a reproduced image from a single hologram which is associated with a reference signal wave identical reference signal wave is formed, and a convex lens placed in front of the locator and is provided at the distance of the focal length / from the locating device.

When reproducing a hologram in a memory arrangement, as described above, it is necessary to illuminate the coherent beam of light that was previously only used on the allocation base plate became. The direct image of an information disc is displayed on the finder surface of the finder educated. With this arrangement, it is necessary, therefore, the optical system and the Invert information storage disk also when reproducing a three-dimensional hologram. While the write and read operations, which in a preferred embodiment Memory array have been described above, it should be noted that the The essence of the invention does not lie in the components of the memory arrangement, but in the memory loss, and therefore the constituent parts of the structure can be changed arbitrarily according to the systems in which the storage arrangement is turned to, and also other components, which can perform equivalent operations as a substitute for the components described to serve. In addition, various functions can be combined to build wires to make it more attractive.

For this purpose 2 sheets of drawings

Claims (1)

a plurality of information discs, i.e., of claims: scrolling moved to form the holograms on the storage disc in the form of a matrix. 1. Method for storing holograms- When reading a memory, ie the reproductions with an information storage disk, the 5 tion of a hologram, laser light is transmitted through the several holograms, which are generated by the use of an ultrasonic wave or an electrical interference of a Body light beam trooptischen effect polarized and an arbitrary and a reference light beam are formed, wo- ches'hologram is illuminated and by a _{: found} in the body by irradiating the reference photoelectric element matrix, the light beam reproduced on the holograms is attached to a reproduced image area . is characterized in that Fig. 1 shows a perspective view of the the reference right ray as a reference wave diagram of a memory reading device at a bedet is, the holographic storage arrangement corresponding to the body information, wherein Cending and deviating reference 1 a laser light source, 2 a beam deflector, 3 Signals are assigned, and that without deflection 15 a storage disk. 4 a reproduced image area of the reference light beam is only the information signal and 5 is a photoelectric element matrix, from a single one, through the reference signal and in such a memory device it is essential Body light beam formed hologram really borrowed, a light detector precisely controllable in the is produced. Direction of the Z axis and the direction of the _ -. Method according to Claim 1, characterized in providing the y-axis. There is a deflection of light Indicates that the reference signal through a difficult and in particular is a deflection of /.assignment signal plate (19) is given, the light is very detrimental in the event of any access corresponding to the body information and lig. The loss of light energy in the deflection from an input signal controller (20) is also very large. It is also a holographic memory array transmission factor a special point of the opening with a device for forming a kohaz order signal plate changes. renten light beam, also with information plates with information signals, which are arranged in the coherent light beam, and with a detection 30 training device behind the information storage disk is provided is known (Bell Laboratories Record, Nov. 1968, pp. 318 to 325). It is also known to be a coherent