CN1697038A - 3D disk type hologram storage method and system - Google Patents

Abstract

A 3D disc holographic storage method is separation orbit storage which works as overlapping partially all holograms on adjacent orbits, recording and reading out all holograms without adjusting angle of reference light and illuminating light, using disc rotation to finalize addressing of hologram in the same orbit and using read - write optical system and disc flat motion to finalize addressing of hologram on different orbit, applying separation orbit heat - fixing as storing method. The 3D disc holographic storage system is also disclosed.

Description

3 D disk type hologram storage method and system

Technical field

3 D disk type hologram storage method and system belong to field of optical storage technology.

Background technology

The high speed development of information science technology is had higher requirement to information storage technology.The body holographic storage technology is carried out information storage and retrieval at the whole volume of storage medium concurrently in the mode of page hologram, these characteristics make advantages such as it has the storage density height simultaneously, memory capacity is big, data transmission rate is high, the data search time is short, become a kind of optical storage techniques of high density data storage.

With the body holographic memory of block photorefractive crystal, adopt proximal surface input path and pure angular multiplexed mode usually as storage medium.But because the limited dynamic range of photorefractive crystal, particularly trailer record is to the erasure effect of stored hologram, make and be difficult in the whole volume of material, promote, thereby total memory capacity is restricted the superelevation storage density that in the small volume in part, can realize.Adopt the storage medium of plate-like, can make full use of whole volumes of material, help realizing high density disc type holographic memory.

The patent No. is 3 D disk type storage means and the system in the invention of ZL96102463.1, though be to adopt the method storage of disc type by track form document image, memory image in each concentric circular tracks can be overlapped each other, increased storage density to a certain extent, but because interorbital image can not be overlapping, hologram on the whole holographic optical disk is distributed be in the track intensive and the sparse form of interorbital distributes, storage organization on the whole storage medium is inhomogeneous, because track space is bigger, limited the storage density of hologram.Adopt thing light and the not aplanatic light path of reference light because device is gone up in addition, it is very long that its coherent length to laser is required, and limited actual application.For storage medium is the material of photorefractive crystal, because the erasure effect that hologram repeatedly writes down, density and picture quality variation that hologram is stored.Because three-dimensional holographic storage uses is the laser of single mode, there is Gaussian distribution in the light spot energy of light beam in addition, can make the energy of interference hologram of storage inhomogeneous, the center is bright, dark on every side, not only the picture quality of influence storage also influences the reproduction of canned data.

The device of present body holographic memory exists that volume is big, complex structure, can not break away from optical table, thing light and the unequal situation of reference light light path.Can not reset after storage medium takes off in addition, influence correctly reading of its canned data.These all are unfavorable for the practicability of three-dimensional holographic storage.

Summary of the invention

The objective of the invention is to propose the 3 D disk type hologram storage method that a kind of memory capacity is big, the canned data holding time is long.Can solve the aforesaid drawbacks and deficiency, the method of this invention not only can make the memory image in each concentric circular tracks overlap, and realized that the image of storing between the track also overlaps, in storing process,, adopted branch track photographic fixing Thermal Fixing in order to prevent wiping of interorbital image.

3 D disk type hologram storage method of the present invention, be a kind of at a plurality of holograms of holographic optical disc recording, adjacent Fourier transform hologram is overlapping on space segment ground (not to be to separate fully, neither be overlapping fully) method, wherein, each hologram is an information page (two-dimensional arrangements of numerical data, or image) Fourier transform hologram, hologram is distributed on the concentric circular tracks of holographic disk, adjacent hologram can have the overlapping of part on the same track, it is characterized in that: the overlapping of part also arranged, all hologram records and do not need to adjust the angle of reference light and illumination light when reading between the hologram on the adjacent orbit; Addressing (tangential addressing) to hologram in the same track is finished by the card rotation, and not co-orbital addressing (radially addressing) is finished with the relative translation of card by the read-write optical system; Adopt the storage means of dividing the track heat fixation; Its storage and to read process as follows:

1) at first select and definite holographic optical disk on the hologram addressing mode of being stored;

1. the angular selectivity Δ X of computed hologram in surface level and the angular selectivity Δ Y in vertical plane, wherein, reference light, thing light and card normal are in same plane, and this plane is called " surface level ", vertical plane, plane is called " vertical plane " therewith, and its computing method are:

$\mathrm{\ΔX}\≈\frac{2\mathrm{\λ}}{d(\sin {\mathrm{\θ}}_R+\sin {\mathrm{\θ}}_s)}\×\frac{\sqrt{n^2-{\sin }^2{\mathrm{\θ}}_R}}{{\cos }^2{\mathrm{\θ}}_R}{r}_R,$ $\mathrm{\ΔY}\≈\frac{2\sqrt{r_R\mathrm{\Δ}\sin {\mathrm{\θ}}_R}}{\cos {\mathrm{\θ}}_R}$

Wherein n and d are respectively the refractive index and the thickness of storage medium, r _RBe the distance of spherical wave center to the hologram center, θ _RAnd θ _SBe respectively the angle between reference light and thing light and the card normal.

Specifically can be about angular selectivity Δ X and the angular selectivity Δ Y in vertical plane referring to Fig. 1,5 and 12 expression Δ X among the figure; 4,8,11 expression Δ Y; The platform displacement Δ L of the change track of 6 certain position of expression.According to top hologram multiplexing method of the present invention, according to the density targets of storage, each hologram center distance each other above the calculation holographic CD.

2. determine the orientation of original records point on card of hologram, the spacing of hologram (selectivity) depends on the angular selectivity Δ X of volume hologram in surface level and the angular selectivity Δ Y in vertical plane on the card, select the horizontal component of the interval delta S of adjacent hologram in the same track to be not less than Δ X, the spacing of two of adjacent orbit holograms is not less than Δ Y on the same perpendicular line, the measuring point of azimuth angle alpha between 30 °～60 ° is as the original records point, the interorbital addressing of level can be realized in this position, reduces the addressing difficulty; Make the distribution of hologram on card even relatively simultaneously.When the dynamic range of recording materials has in limited time, in fact the interval of hologram can be obtained greater than above calculated value, to guarantee lower crosstalk noise.

Among Fig. 11,2,3, represent three different original records positions respectively.Under this addressing scheme, the position 2 among Fig. 1 is determined each circuit orbit of the present invention original records point on card.7 is the centre distance Δ S of adjacent hologram in the track among the figure, and 9 is the azimuth angle alpha of hologram correspondence.When track addressing direction during along the perpendicular diameter of card (position 1), tangential selectivity (selectivity in the track) is Δ X, and radially selectivity (interorbital selectivity) is Δ Y.When track addressing direction during along the horizontal diameter of card (position 3), tangential selectivity (selectivity in the track) is Δ Y, and radially selectivity (interorbital selectivity) is Δ X.

2) begin storage: the time shutter t that calculates each hologram _{I, j}Sequence with these times.

First track is from the circuit orbit of the maximum radius of holographic optical disk, the edge of this orbital distance holographic optical disk is 2～3mm, from first hologram of position angle opening entry of selecting, each holographic optical disk rotates a small angle, Δ X and Δ Y according to the addressing mode of holographic optical disk race way diameter and previous calculations calculate, and this angle is between 0.006 °～0.06 °.Write down next width of cloth hologram of same track, up to this orbit rotation to the initial orientation angle.Change write down this track after, by holographic optical disk move radially Δ L, to the direction translational that the holographic optical disk radius diminishes, the radius of change track, the hologram of opening entry next one track.Dynamic range performance according to crystalline material, be that monorail is fixedly the time storage time when design divides track heat fixation writing information, after first track has been stored, carry out step 3), storage time when design divides track heat fixation writing information is for the multiple road fixedly the time, deposit a plurality of tracks, carried out step 3).

3) carry out branch track heat fixation, owing to the principal element of storage density in the photorefractive crystal is that this reason of limited dynamic range of material makes the interorbital of present holographic optical disk and the erasure effect that the doubling of the image produced in the track make doubling of the image degree very little, therefore in order to improve storage density, to store Thermal Fixing in batches and combine, develop into the disc type holographic storage technology of branch track heat fixation with the disc type storage.Not only can improve storage density, and realize non-volatile memories, canned data is preserved for a long time.Its main points are:

1. with step 2) in the holographic disk of M hologram in a record track (or a plurality of track) take off, be placed in the heating furnace of controlled temperature, be heated to 140 ℃, and held warm 20 minutes, be cooled to room temperature;

2. crystal is put back to the position of former storage, repeating step 2) and this step in step 1., all hologram records that need write down on whole these holographic optical disks are finished;

3. with uniform incoherent light irradiation holographic disk, disposable record and the fixing hologram of making displays, and promptly develops.

4) during reading of data, with fixing and develop after holographic optical disk be installed on the precision positioner, the initial orientation angle when holographic optical disk is gone to record is shone with aforesaid reference light, rotate holographic optical disk, just can realize the reading of hologram on each track.

Described 3 D disk type hologram storage method is characterized in that: the storage time (exposure time series) during according to minute track heat fixation storage computation writing information, for the photorefractive crystal recording materials, the main points of calculating M hologram exposure sequential are as follows:

Each track hologram all is the access time of determining each hologram according to exposure time series, because the radius difference of track, so the quantity of the hologram that each track is stored is different with exposure time series.For corresponding to above-mentioned hologram addressing mode, for fear of between the track because the overlapping caused erasure effect of hologram, need new storage means and time shutter computing method, the present invention proposes the storage means (method sees following explanation for details) of branch track heat fixation storage, and the method for dividing the storage of track heat fixation, the storage time when having proposed new writing information (exposure time series) computing method.

1) at first under room temperature and pure angular multiplexed condition, measures the write time constant τ of material _W, erasing time constant τ _EWith saturated diffraction efficiency _Saturated

2) adopt the interorbital erasing time constant τ of the method analogue measurement material of a small amount of grating of heat fixation in batches _F

3) according to size and the interval delta X between the adjacent hologram and the Δ Y of single hologram, calculate wipe matrix W (i, j)

$\mathrm{\α}={\tan }^{-1}\sqrt{\frac{d_H^2}{{\left(j{\mathrm{\Δ}}_x\right)}^2+{\left(i{\mathrm{\Δ}}_y\right)}^2}-1}$ (j=l-k wherein; I=m-n)

Promptly $\mathrm{\α}={\tan }^{-1}\sqrt{\frac{d_H^2}{{(l-k)}^2{{\mathrm{\Δ}}_x}^2+{(m-n)}^2{{\mathrm{\Δ}}_y}^2}-1}$

d _HBe the hologram diameter, the centre distance Δ of two adjacent holograms in the same track _xWith two interorbital interval delta _yStore M groups (batch) hologram, every group (on each track) can store N _M

4) target diffraction efficiency target as requested and aforesaid parameter are calculated the time shutter t of last hologram _M:

5) introduce parameter ν and be expressed as following formula:

6) utilize reverse method, go out exposure time series by following formula recursion:

$[1-\exp (-\frac{t_{i,j}}{{\mathrm{\τ}}_w})]\×\exp (-\frac{T_{R,C}^{\mathrm{SAM}}}{{\mathrm{\τ}}_E})=v$

$T_{R,C}^{\mathrm{SAM}}=\underset{i=0,j=1}{\overset{{\mathrm{\μ}}_x-1}{\mathrm{\Σ}}}W(i,j)t_{\mathrm{ij}}+\frac{{\mathrm{\τ}}_E}{{\mathrm{\τ}}_F}\underset{i=1}{\overset{{\mathrm{\μ}}_y-1}{\mathrm{\Σ}}}\underset{j=-1({\mathrm{\μ}}_x-1)}{\overset{{\mathrm{\μ}}_x-1}{\mathrm{\Σ}}}W(i,j)t_{\mathrm{ij}}$

t _{I, j}The time shutter of representing i the j width of cloth hologram on the track, realized the algorithm of above-mentioned exposure time series by programming, required suitable exposure time series in the time of can calculating extensive storage quickly.A collection of hologram can be a track, also can be a plurality of tracks, and the aforementioned calculation formula all is suitable for both of these case.

Described 3 D disk type hologram storage method is characterized in that: when storage medium is photorefractive crystal, adopt reflection type optical path, the optical axis of crystal is vertical with card, employing can obtain higher diffraction efficiency and optionally orthogonal polarized light write; When storage medium is photopolymer, adopt transmitted light path.

Described 3 D disk type hologram storage method is characterized in that: the sphere reference wave of adopt assembling when reading, this is because the parasitic light of sphere reference wave when more helping suppressing to read than the sphere reference wave of dispersing.

Adopt 3 D disk type hologram storage method of the present invention, reduced the track space of holographic optical disk, increased the number of tracks in the whole holographic optical disk, can increase substantially the memory capacity of unit volume.The addressing mode of this programme can make hologram be arranged in uniformly on the card of whole holographic optical disk, and it is tight in orbit to have overcome hologram, and the unevenness of interorbital distance improves storage density more than several times, reduces the bit error rate.The present invention has overcome the key issue of photorefractive crystal as disk storage medium, improved the effective dynamic range of photorefractive crystal, overcome the volatibility of photorefractive material storage, increased the holding time of canned data, realized the long-time preservation of canned data.

In order to realize the hologram storage method of aforementioned said 3 D disk type multiple trace overlap, the present invention has designed 3D hologram disc type storage system.For spherical wave reference light, it is very strict to read and write fashionable Prague matching condition.In order to realize multiple road storage and to divide the heat fixation of track holographic optical disk, still can realize the effect of Prague coupling after reaching storage medium destage resetting repeatedly, the present invention has designed high precision holographic disk steady arm in storage system.

3 D disk type hologram memory system index path of the present invention is referring to Fig. 2, system diagram is referring to Fig. 3, high precision holographic disk steady arm is referring to Fig. 4～Fig. 6, storage system is formed from the holographic optical disk 48 of two sides incident jointly by writing system, read-out system and by thing light and reference light, it is characterized in that: holographic optical disk 48 is fixed by steady arm, steady arm is connected with precise rotating platform 40 by pitman shaft 41, the base of precise rotating platform 40 is connected on the accurate straight-line displacement platform 39, these two devices 39,40 all by the Data Control line by external computer control.Described steady arm is by backstay 50, the locating slot 43 that matches with backstay 50, the steady arm coupling nut 42 that is connected with locating slot, the retaining ring 45 that can on locating slot, slide, and the locating wedge 47 in the locating slot, set nut 44 on the retaining ring 45, stop screw 46 is formed, wherein an end of backstay loads holographic optical disk 48 by the step of setscrew nut 49 and backstay itself by face, the other end has three face a, b, c be respectively as the confined planes of backstay, and a side a ' in the groove of face a and locating slot 43 cooperates, guarantee the location of backstay gyratory directions, i.e. anti-rotation; Face b cooperates with b ' face on the locating slot 43, guarantees the location of axial upper edge axis direction, promptly prevents axial motion; Locating surface c cooperates with the inclined-plane of locating wedge 47, guarantees to be subjected under the situation of set nut 44 pressure, and set nut 44 withstands on the inclined-plane e, backstay can be stressed axially and component radially, make its closely with locating slot 43 close fit mutually; The axis of set nut 44 can also guarantee the upwards location of backstay, vertical footpath by the diametric(al) of locating slot 43.

Described 3 D disk type hologram memory system, it is characterized in that: writing system is by the polarization beam splitter prism 13 that incident light is divided into thing light and reference light, and be positioned at thing optical shutter 14 on the thing light light path successively, spatial filter 15, thing optical alignment lens barrel 16, thing optical alignment lens 17, thing light Gaussian beam homogenising device 18, spatial light modulator (SLM) 20, SLM seat 21, Fourier transform camera lens 22, tapered wave filter 23, reach the reference light shutter 38 that is positioned at successively on the reference light light path, spatial filter 37, reference light collimation lens 35, reference light Gaussian beam homogenising device 34, catoptron 31, reference light camera lens 29 is formed jointly, wherein collimates the Gaussian beam homogenising device 18 based on non-spherical lens that the lens barrel front ends all are connected with two, 34 are made up of two lens, and the lens of the plane of incidence are plano-concave lens, the lens of exit facet are plano-convex lens, and the curved surface of two lens is aspheric surface, and the lens face shape of the plane of incidence and exit facet is the plane, and clear aperture is identical with the clear aperture of the collimation lens that is mated, plano-convex lens relative aperture plano-concave lens is twice above, and two aspheric curvature relationship satisfy the following relationship formula:

$R\left(r\right)=\frac{R_0{[1-\exp \left(\frac{-r^2}{{\mathrm{\ω}}^2}\right)]}^{1/2}}{{[1-\exp \left(\frac{-{r_0}^2}{{\mathrm{\ω}}^2}\right)]}^{1/2}}$

Wherein, R is the radius-of-curvature of convex surface, and r is the radius-of-curvature of concave surface, R ₀Be the radius of the collimated light beam after the homogenizing of output, r ₀Be the collimated light beam radius before the homogenising, ω is the back diameter of Gaussian beam, and r, and R is a variable.18 and 34 the difference be that the lens barrel bright dipping diaphragm diameter of homogenising device is different, thing light ratio reference light about 10%～30%.

Described 3 D disk type hologram memory system is characterized in that: be provided with after the Gaussian beam homogenising device 18 on thing light light path can make the object beam optical axis direction produce 90 ° of angular deflections, refractive index makes the pentagonal prism, right-angle prism of the light path coupling of thing light and reference light light beam or other can change the prism 19 of optical axis angle.

Described 3 D disk type hologram memory system is characterized in that: holographic optical disk 48 is that photorefractive crystal, photopolymer or other holographic storage material are made.

The principle of work of 3 D disk type hologram memory system of the present invention is:

(1) light that is sent by laser instrument incides polarization beam splitter prism 13, is divided into the mutually perpendicular two-beam in polarization direction: straight saturating thing light and 90 ° of reference lighies of deflection.This two-beam passes through respectively by computer-controlled shutter 14 and 38, by the time of computer program by the opening and closing of interface card control shutter, when shutter is opened, light beam enters into spatial filter 15 and 37 through shutter and expands bundle and filtering, forms larger-diameter collimation Gaussian beam through collimation lens 17 and 35 again.

(2) go into to inject Gaussian beam homogenising device 18 when collimating Gaussian beam in the position of waist spot, after 34, to can't harm the lost territory with the hot spot cross section energy of Gaussian distribution and be converted into equally distributed circular light spot, and spot diameter can increase be twice about, and export with collimating status.So just can obtain even distribution of light spot energy and diameter and satisfy thing light and reference light request for utilization.

(3) wherein uniform object beam goes into to inject the window that the optical axis front end is placed prism 19, at the inner secondary reflection that takes place of prism, this prism can make the object beam optical axis direction produce the deflection at 90 ° of angles, then to penetrate from the another one window under the situation that does not change former polarization state, shine with its same optical axis on the spatial light modulator 20 that is positioned at Fourier transform camera lens 22 front focal plane positions on.Prism has two important effects: the one, and the angle that can accurately turn back light path and need is to reduce the size of whole optical path; The 2nd, by selecting the rational optical parametric of prism, the model, clear aperture and the glass refraction that comprise prism, make object beam light through the internal reflection of prism, remedy the optical path difference with reference beam just, obtain the system of thing light and the equilibrium of reference light light path.

(4) has the store image information that loads by computer control system on the spatial light modulator (SLM) 20.Uniformly the thing rayed is on it, each pixel of SLM with printing opacity and lighttight form image construction the information page of hologram.

(5) polaroid on the spatial light modulator can produce the thing polarization state of light to input page and rotate to the direction identical with reference light.This thing light forms the spectrum face through Fourier transform camera lens 22 then on its back focal plane, a tapered wave filter that has rectangular aperture is arranged in the rear end of Fourier transform camera lens 22, and the spectrum inferior all the other grades filters, and only keeps the zero level spectrum of diffracted intensity maximum.

(6) on the another one direction, reference light is also through after expanding bundle, filtering, collimation, homogenising, be radiated on the catoptron 31 that is positioned on the front slideway 33, enter reference light camera lens 29 along the axis direction reflection, by the adjustment seat 32 of adjustment catoptron and the position and the angle of reference light camera lens adjustment rack, can obtain the convergence sphere reference light of an anaberration.

(7) a certain position of thing light behind the Fourier transform camera lens of the sphere reference light of this convergence and process Fourier transform camera lens 22 overlaps and forms interference pattern, holographic optical disk just places this position, usually this position is that decide according to the thickness of recording materials the out of focus position the locating of the front 2～3mm of the back focal plane of Fourier transform camera lens 22.

(8) by adjusting the strength ratio of suitable laser power and thing light, reference light, under the situation that the shutter of thing light and reference light is all opened, just can make the reference light of information thing light with input page and convergence form interference pattern at the holographic optical disk material internal, in the described in front time shutter, interferogram is written in the medium of holographic optical disk.

(9) sense data the time, only open the reference light shutter, use reference light to shine on the memory location of holographic optical disk, just can reproduce the interferogram of having stored, carry out inverse Fourier transform through imaging lens 24, the original image of input page is reverted on the ccd detector, with complete the reading out of image information of storage.

(10) when storage, with 2 positions among Fig. 1 of being registered to of holographic optical disk, this position and belongs to certain position between between level and vertical centering control not on the diametric(al) of holographic optical disk.Use precise rotating platform 39 to realize the edge of holographic optical disk and the concentric circular tracks rotation of precise rotating platform 39 revolving shaftes, small angle of precise rotating platform 39 each rotations just can write down or read an image on the track of holographic optical disk.The a plurality of images of realization are stored and are read in same circuit orbit.

(11) realize with accurate straight-line displacement platform 39 for not co-orbital conversion and interorbital addressing.Computer program is controlled accurate straight-line displacement platform 39 and is driven whole turntable along doing the straight line microdisplacement on the direction parallel with the holographic optical disk strictness, can change the radius of each concentric circles storage track on each holographic optical disk like this, to realize the change of track.

(12) principle of work of the steady arm of disc type crystal precision positioning is as follows:

1) the holographic optical disk precision positioner has the positioning function of two aspects, and the one, after resetting, holographic disc type on the central axis of dish, do not take place to change around the anglec of rotation of this central shaft; The 2nd, the surface of dish does not have relative planar offset with the original position in when record, guarantees that promptly the crystal dish can be because of the installation runout error of loading and unloading generation card repeatedly.Can guarantee that like this page of data of storing does not produce the offset error of the page, the accurate storage that realizes page of data with read.

2) because the precision of steady arm requires very high, end at backstay 50 on location structure designs with three face a, b, c is a locating surface, as shown in Figure 3, the locking by set nut 44 can apply acting force by e on an inclined-plane of backstay 50, and this acting force can produce the component on the both direction, these two component can act on respectively on two the face a that cooperate and c with backstay, and backstay 50 closely is pressed in the locating slot 43; Locating wedge 48 has an inclined-plane, and when backstay 50 was subjected to the component of both direction to be pressed on the locating wedge 48, three locating surface of backstay was closely pressed together on three reference fields of locating slot 43 and locating wedge 48.So just can unclamping and locking and guarantee the holographic optical disk off-line and reset the back: 1. by set nut 44. on the pitman shaft axis, relatively rotate error; 2.. along the error that moves forward and backward on the axis direction; 3.. pitching and these three kinds of errors of stagger on the radial section of vertical pitman shaft axle can both be restricted in the scope of permission.

3) backstay 50 that holographic optical disk is housed is taked to load and unload up and down to locating slot 43 loading and unloading the time, promptly in the angular position of holographic optical disk original records, with the direction of vertical pitman shaft, positions and reset operation.See shown in Figure 4.Can fully compress the space between former and later two Fourier transform camera lenses like this, make more miniaturization of system.

Satisfied reducible requirement behind the holographic disk destage according to the designed three-dimensional holographic storage of 3 D disk type storage means of the present invention, and the three-dimensional holographic storage of the present invention's design is fully integrated on a base with all devices, have small-sized, stable, flexible characteristic, also improve the quality of memory image, can reduce the bit error rate.

Description of drawings

Hologram geometric relationship synoptic diagram when Fig. 1 writes down hot spot and is in different orientations;

1. the hot spot of upright position distributes, 2. the initial position of hot spot of the present invention distributes, 3. the hot spot of horizontal level distributes, 4. the angular selectivity Δ Y of the upright position at adjacent orbit 1 place in the position, 5. the angular selectivity Δ X in the surface level of same track, 6. the platform displacement Δ L that represents the change track of certain position, 7. be the centre distance Δ S of adjacent hologram in the track, 8. the angular selectivity Δ Y of the upright position at adjacent orbit 2 places in the position, 9. be the central angle alpha of adjacent hologram correspondence, 10. the holographic optical disk center of circle, 11. the angular selectivity Δ X in the angular selectivity Δ Y of the upright position at adjacent orbit 3 places, the not co-orbital surface level in 12. positions 3 in the position

Fig. 2 system light path figure;

Fig. 3 entire system wiring layout;

Among Fig. 2-3,13. polarization beam splitter prisms, 14. thing optical shutters, 15. spatial filter, 16. thing optical alignment lens barrels, 17. thing optical alignment lens, 18. Gaussian beam homogenising device, 19. pentagonal prisms, 20. spatial light modulators (SLM), 21.SLM seat, 22. Fourier transform camera lens FTL1,23. tapered wave filters, 24. Fourier transform camera lens FTL2,25. camera lenses are adjusted platform, 26.CCD planar array detector, 27. two micrometric displacement platforms, platform, 29. reference light camera lenses are adjusted in 28. 6 fine motions, 30. the camera lens adjustment rack, 31. catoptrons, 32. catoptrons are adjusted seat, 33. guide rail, 34. diaphragms, 35. reference light collimation lenses, 36. reference light collimation lens barrel, 37. spatial filters, 38. reference light shutters, 39. accurate straight-line displacement platform, 40. precise rotating platforms, 41. pitman shafts, 42. the steady arm coupling nut, 43. backstays, 44. set nuts, 45. retaining rings, 46. stop screw 47. locating wedges, 48. holographic optical disks, 49. nuts, 50. base, 51. catoptron, 52. catoptrons, 53. laser instruments.

Fig. 4 disc type crystal precision positioner sectional view;

A-A sectional view among Fig. 5 Fig. 4;

Fig. 6 disc type crystal precision positioner stereographic map;

Fig. 7 stores the part reproduced image of 10000 width of cloth holograms;

(a) the 1st width of cloth (track 1); (b) the 3637th width of cloth (track 2); (c) the 8499th width of cloth (track 3); (d) the 10000th width of cloth (track 4)

Embodiment

Specifically introduce the preferred embodiments of the present invention below in conjunction with accompanying drawing:

Storage means embodiment of the present invention:

(1) use the 3 D disk type hologram memory system of the present invention's design to carry out the data storage example.At first selecting storage medium material is photorefractive crystal: singly mix iron 0.03wt%, and the lithium columbate crystal of growth attitude, and at this plane of crystal plating 532nm anti-reflection film.According to the refractive index and the thickness of storage medium, the spherical wave center is to the distance at hologram center, and the angle between reference light and thing light and the card normal etc. calculates Δ X and Δ Y.Its orbital spacing is 0.8mm like this, adjacent hologram centre distance 15 μ m, and the hologram diameter is 3.0mm, equivalent single-point reusing degree is 750.Volume 0.875cm ³Circular photorefractive crystal dish in, store 10000 width of cloth holographic pages altogether.

(2) carry out the calculating of exposure time series then: with the target diffraction efficiency is 6.0 * 10 ^-5' carry out the multiplexing experiment of small-scale earlier, utilize trial and error to determine in the multiplexing recording process of storage medium material crystal the write and erase time constant, calculate rational exposure time series in view of the above.4 tracks are stored 10000 panel height resolution holograms, calculate 3.277 seconds the longest time shutter, minimum exposure time 1.461 seconds, and 10000 width of cloth holograms exposed 25467.8 seconds altogether.

(3) carry out data storage according to foregoing step then, under the normal temperature holographic optical disk is loaded on the disc type crystal precision positioner, from first track of distance plate edge 3mm beginning, wherein position angle 9 is 45 ° of opening entries, writes down the hologram of the track that finishes, and holographic optical disk is forwarded to the position at position angle 9, holographic disk is taken off the heating furnace that is placed into controlled temperature from disc type crystal precision positioner, be heated to 140 ℃, and held temperature 20 minutes, be cooled to room temperature; Holographic optical disk is refilled on the disc type crystal precision positioner then, holographic optical disk is moved horizontally to disc centre, making orbital spacing is 0.8mm.

(4) process after the opening entry of multiple above-mentioned (3) is finished until 4 whole hologram records of track;

(5) shone holographic disk 20 minutes with uniform incoherent light then, record and fixing hologram are displayed.

(6) at last by reading to the storage data.This example has adopted the disc type holographic storage technology of dividing the track heat fixation, improves storage density and information holding time.Utilize this scheme to divide 4 batches of 4 tracks storages and off-line to fix 10000 panel height resolution holograms in same crystal, realized non-volatile memories, storage surface density reaches 50bits/ μ m ², volume density reaches 10Gb/cm ³The image of storage obtains high fidelity and reproduces, and the diffraction efficiency of reproduced image is even, and details is clear, and average signal-to-noise ratio (SNR) is 3.6, and being equivalent to the original bit error rate is 1.6 * 10 ^-4

Fig. 7 has provided the reproduction picture of part hologram.

The small-sized disc type hologram memory system that the method according to this invention is designed

1. the major parameter of 3 D disk type hologram memory system is:

3 D disk type hologram memory system optics and physical construction as shown in Figures 2 and 3, writing system is by polarization beam splitter prism 13, thing optical shutter 14, spatial filter 15, thing optical alignment lens 17, Gaussian beam homogenising device 18,. pentagonal prism 19 .SLM 20, Fourier transform camera lens FTL ₁22,23. tapered wave filters are formed.Read-out system is by reference light shutter 38, spatial filter 37, reference light collimation lens 35, Gaussian beam homogenising device 18, catoptron 31, reference light camera lens 29, Fourier transform camera lens FTL ₂24, platform 28 is adjusted in 27, six fine motions of 26, two micrometric displacement platforms of CCD planar array detector and relevant adjustment rack is formed.Wherein several core component parameters are:

(1) SLM:1024 * 768 pixels, CCD:1024 * 1024 pixels, single width hologram data capacity 0.786Mbit.

(2) the Fourier transform camera lens is to FTL ₁And FTL ₂: distortion is less than 0.01%, and wave aberration is less than 1/4～1/10 λ, and the focal distance ratio of transform lens and imaging len is 13: 6, can realize 1: 1 pixel coupling between principal plane.

(3) prism 19 is pentagonal prisms, pentagonal prism model W II-90, and bore 38.1 adopts K9 glass, reduces the overall dimensions of light path effectively, and the light path difference of indemnity light and reference light makes it less than 5mm.

(4) catoptron 31 of reference light is positioned on the slide block on the guide rail, can do certain limit (0～150mm) reference light (0～120 °) angular setting.

(5) Gaussian beam homogenising device is made up of two non-spherical lenses, and the lens of the plane of incidence are plano-concave lens, and the lens of exit facet are plano-convex lens, incident bore 30mm, outgoing bore 50mm, the hot spot of homogenising make in the image of storing and reading, and image view picture illumination is even.

(6) drive part of holographic optical disk is by turntable-platform addressing mechanism, and the holographic optical disk precision positioner is formed, and wherein: the holographic optical disk precision positioner: card resets runout error less than 0.002mm, and the angle reset error is less than 0.001 °.Turntable-platform addressing mechanism: rotate resolution and unidirectional repeatability: 0.001 °, translation resolution and unidirectional repeatability: 0.2 μ m.For the photorefractive crystal of diameter 80mm, thickness 5mm, can be more than holographic Figure 20 ten thousand width of cloth of addressing under software control.

2. adopt the multiplexing sphere reference wave in empty angle to combine with convergence.Reflected light for fear of reference light is brought noise into imaging system, adopts asymmetric light path (50 ° of thing angles of light, 22 ° of reference light incident angles).Optical system imaging quality is good, system's miniaturization (600 * 400 * 180mm).

Claims (9)

1, a kind of 3 D disk type hologram storage method, be a kind of at a plurality of holograms of holographic optical disc recording, adjacent Fourier transform hologram is overlapping on space segment ground, not to separate fully, neither overlapping fully method, wherein, each hologram is a two-dimensional arrangements that information page is a numerical data, or the Fourier transform hologram of image, hologram is distributed on the concentric circular tracks of holographic disk, adjacent hologram can have the overlapping of part on the same track, it is characterized in that: the overlapping of part also arranged, all hologram records and do not need to adjust the angle of reference light and illumination light when reading between the hologram on the adjacent orbit; Addressing (tangential addressing) to hologram in the same track is finished by the card rotation, and not co-orbital addressing (radially addressing) is finished with the relative translation of card by the read-write optical system; A storage means of adopt dividing the track heat fixation, its storage and to read process as follows:

1) at first select and definite holographic optical disk on the hologram addressing mode of being stored;

1. the angular selectivity Δ X of computed hologram in surface level and the angular selectivity Δ Y in vertical plane, wherein, reference light, thing light and card normal are in same plane, and this plane is called " surface level ", vertical plane, plane is called " vertical plane " therewith, and its computing method are:

$\mathrm{\ΔX}\≈\frac{2\mathrm{\λ}}{d(\sin {\mathrm{\θ}}_R+\sin {\mathrm{\θ}}_s)}\×\frac{\sqrt{n^2-{\sin }^2{\mathrm{\θ}}_R}}{{\cos }^2{\mathrm{\θ}}_R}{r}_R,$ $\mathrm{\ΔY}\≈\frac{2\sqrt{r_R\mathrm{\ΔX}\sin {\mathrm{\θ}}_R}}{\cos {\mathrm{\θ}}_R}$

Wherein n and d are respectively the refractive index and the thickness of storage medium, r _RBe the distance of spherical wave center to the hologram center, θ _RAnd θ _SBe respectively the angle between reference light and thing light and the card normal;

2. determine the orientation of original records point on card of hologram, the spacing of hologram is that selectivity depends on the angular selectivity Δ X of volume hologram in surface level and the angular selectivity Δ Y in vertical plane on the card, select the horizontal component of the interval delta S of adjacent hologram in the same track to be not less than Δ X, the spacing of two of adjacent orbit holograms is not less than Δ Y on the same perpendicular line, the measuring point of position angle (9) between 30 °～60 ° is as the original records point, the interorbital addressing of level can be realized in this position, reduces the addressing difficulty; Make the distribution of hologram on card even relatively simultaneously; When the dynamic range of recording materials has in limited time, the interval of hologram can be obtained greater than above calculated value, to guarantee lower crosstalk noise;

2) begin storage:

1. calculate the time shutter t of each hologram _{I, j}Sequence with these times;

2. first track is from the circuit orbit of the maximum radius of holographic optical disk, the edge of this orbital distance holographic optical disk is 2～3mm, from first hologram of position angle opening entry of selecting, each holographic optical disk rotates a small angle, Δ X and Δ Y according to the addressing mode of holographic optical disk race way diameter and previous calculations calculate, and this angle is between 0.006 °～0.06 °; Write down next width of cloth hologram of same track, up to this orbit rotation to the initial orientation angle; Change write down this track after, by holographic optical disk move radially Δ L (6), to the direction translational that the holographic optical disk radius diminishes, the radius of change track, the hologram of opening entry next one track; Dynamic range performance according to crystalline material, be that monorail is fixedly the time storage time when design divides track heat fixation writing information, after first track has been stored, carry out step 3), storage time when design divides track heat fixation writing information is for the multiple road fixedly the time, deposit a plurality of tracks, carried out step 3).

3) carry out branch track heat fixation, its main points are:

1. with step 2) in the holographic disk of M hologram in record a track or a plurality of track take off, be placed in the heating furnace of controlled temperature, be heated between 120 ℃～150 ℃, and held warm 10～30 minutes, be cooled to room temperature;

2. crystal is put back to the position of former storage, repeating step 2) in hologram record and the step in this step 1., all hologram records that need write down on whole these holographic optical disks are finished;

3. with uniform incoherent light irradiation holographic disk, disposable record and the fixing hologram of making displays, and promptly develops;

4) during reading of data, with fixing and develop after holographic optical disk be installed on the precision positioner initial orientation angle when holographic optical disk is gone to record, the aforesaid reference light irradiation of usefulness, rotate holographic optical disk, just can realize the reading of hologram on each track.

2. 3 D disk type hologram storage method according to claim 1 is characterized in that: according to a minute track heat fixation storage, the write time t of computed hologram _{I, j},, i.e. the sequence of the time shutter of the j width of cloth hologram on i track and these times, for the photorefractive crystal recording materials, the main points of calculating M hologram exposure sequential are as follows:

1) at first under room temperature and pure angular multiplexed condition, measures the write time constant τ of material _W, erasing time constant τ _EWith saturated diffraction efficiency _Saturated

2) adopt the interorbital erasing time constant τ of the method analogue measurement material of a small amount of grating of heat fixation in batches _F

3) according to size and the interval delta X between the adjacent hologram and the Δ Y of single hologram, calculate wipe matrix W (i, j):

$\mathrm{\α}={\tan }^{-1}\sqrt{\frac{d_H^2}{{\left(j{\mathrm{\Δ}}_x\right)}^2+{\left(i{\mathrm{\Δ}}_y\right)}^2}-1}$ (j=l-k wherein; I=m-n)

Promptly $\mathrm{\α}={\tan }^{-1}\sqrt{\frac{d_H^2}{{(l-k)}^2{{\mathrm{\Δ}}_x}^2+{(m-n)}^2{{\mathrm{\Δ}}_y}^2}-1}$

d _HBe the hologram diameter, the centre distance Δ x and the two interorbital interval delta y of two adjacent holograms in the same track; Store M groups/batch hologram, every group is can store N on each track _M

4) target diffraction efficiency as requested _TargetWith aforesaid parameter, calculate the time shutter t of last hologram _M:

5) introduce parameter v and be expressed as following formula:

6) utilize reverse method, go out exposure time series by following formula recursion:

$[1-\exp (-\frac{t_{i,j}}{{\mathrm{\τ}}_w})]\×\exp (-\frac{T_{R,C}^{\mathrm{SAM}}}{{\mathrm{\τ}}_E})=v$

$T_{R,C}^{\mathrm{SAM}}=\underset{i=0,j=1}{\overset{{\mathrm{\μ}}_x-1}{\mathrm{\Σ}}}W(i,j)t_{i,j}+\frac{{\mathrm{\τ}}_E}{{\mathrm{\τ}}_F}\underset{i=1}{\overset{{\mathrm{\μ}}_y-1}{\mathrm{\Σ}}}\underset{j=-({\mathrm{\μ}}_x-1)}{\overset{{\mathrm{\μ}}_x-1}{\mathrm{\Σ}}}W(i,j)t_{\mathrm{ij}}$

t _{I, j}The time shutter of representing i the j width of cloth hologram on the track, realized the algorithm of above-mentioned exposure time series by programming, required suitable exposure time series in the time of can calculating extensive storage quickly.A collection of hologram can be a track, also can be a plurality of tracks, and the aforementioned calculation formula all is suitable for both of these case.

3. 3 D disk type hologram storage method according to claim 1 is characterized in that: when storage medium is photorefractive crystal, adopt reflection type optical path, the optical axis of crystal is vertical with card, adopts orthogonal polarized light s polarization; When storage medium is photopolymer, adopt transmitted light path.

4. 3 D disk type hologram storage method according to claim 1 is characterized in that: adopt the sphere reference wave of assembling when reading, thing light and reference light are complete aplanatisms.

5. 3 D disk type hologram storage method according to claim 1 and the 3 D disk type hologram memory system that designs, form jointly from the holographic optical disk (48) of two sides incident by writing system, read-out system and by thing light and reference light, it is characterized in that: holographic optical disk (48) is fixed by steady arm, steady arm is connected with precise rotating platform (40) by pitman shaft (41), the base of precise rotating platform (40) is connected on the accurate straight-line displacement platform (39), these two devices (39), (40) all by the Data Control line by external computer control; Described steady arm is by backstay (50), the locating slot (43) that matches with backstay (50), the steady arm coupling nut (42) that is connected with locating slot, the retaining ring that can on locating slot, slide (45), and the locating wedge (47) in the locating slot, set nut (44) on the retaining ring (45), stop screw (46) are formed, and wherein an end of backstay loads holographic optical disk (48) by the step of setscrew nut (49) and backstay itself by face; The other end has three faces (a), and (b), (c) respectively as the confined planes of backstay, the side (a ') in the groove of face (a) and locating slot (43) cooperates the location of assurance backstay gyratory directions, i.e. anti-rotation; Face (b) cooperates with (b ') face on the locating slot, guarantees the location of axial upper edge axis direction, promptly prevents axial motion; Locating surface (c) cooperates with the inclined-plane of locating wedge (47), assurance is subjected under the situation of set nut (44) pressure, set nut (44) withstands on the inclined-plane (e), backstay can be stressed axially and component radially, make its closely with locating slot (43) close fit mutually; The axis of set nut (44) can also guarantee the upwards location of backstay, vertical footpath by the diametric(al) of locating slot (43).

6. 3 D disk type hologram memory system according to claim 5, it is characterized in that: writing system is by the polarization beam splitter prism (13) that incident light is divided into thing light and reference light, and be positioned at thing optical shutter (14) on the thing light light path successively, spatial filter (15), thing optical alignment lens barrel (16), thing optical alignment lens (17), thing light Gaussian beam homogenising device (18), spatial light modulator (20), spatial light modulator seat (21), Fourier transform camera lens (22), tapered wave filter (23), reach the reference light shutter (38) that is positioned at successively on the reference light light path, spatial filter (37), reference light collimation lens (35), reference light Gaussian beam homogenising device (34), catoptron (31), reference light camera lens (29) is common to be formed.

7. 3 D disk type hologram memory system according to claim 6, it is characterized in that: the described Gaussian beam homogenising device (18) that all is connected with two collimation lens barrel front ends based on non-spherical lens, (34) form by two lens, the lens of the plane of incidence are plano-concave lens, the lens of exit facet are plano-convex lens, and the curved surface of two lens is aspheric surface, and the lens face shape of the plane of incidence and exit facet is the plane, clear aperture is identical with the clear aperture of the collimation lens that is mated, plano-convex lens relative aperture plano-concave lens is twice above, and two aspheric curvature relationship satisfy the following relationship formula:

$R\left(r\right)=\frac{R_0{[1-\exp \left(\frac{-r^2}{{\mathrm{\ω}}^2}\right)]}^{1/2}}{{[1-\exp \left(\frac{-{r_0}^2}{{\mathrm{\ω}}^2}\right)]}^{1/2}}$

Wherein, R is the radius-of-curvature of convex surface, and r is the radius-of-curvature of concave surface, R ₀Be the radius of the collimated light beam after the homogenizing of output, r ₀Be the collimated light beam radius before the homogenising, ω is the back diameter of Gaussian beam, and r, and R is a variable.

8. 3 D disk type hologram memory system according to claim 6 is characterized in that: the Gaussian beam homogenising device (18) on thing light light path be provided with afterwards can make the object beam optical axis direction produce 90 ° of angular deflections, refractive index makes the pentagonal prism, right-angle prism of the light path coupling of thing light and reference light light beam or other can change the prism (19) of optical axis angle.

9. 3 D disk type hologram memory system according to claim 5 is characterized in that: holographic optical disk (48) is that photorefractive crystal, photopolymer or other holographic storage material are made.

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