CN2729863Y - Polarization holographic optical storage device using photochromic material film as recording medium - Google Patents

Abstract

A polarization holographic storage device using a photochromic material film as a recording medium, using a spatial light modulator as a page-type information input element, an image acquisition device as an information readout device, using a photochromic material film as a recording medium, and placing it Record holograms on the spectral surface of Fourier transform lenses, use the light-induced anisotropy of photochromic materials, and use mutually orthogonal linearly polarized light or orthogonal circularly polarized light as the object light and reference light to record polarization-modulated holograms , to improve the signal-to-noise ratio of the reproduced image. The bacillus rhodopsin film or fulginic anhydride film is used as the rewritable holographic recording medium, which has the advantages of high photosensitive sensitivity, high spatial resolution, many rewritable times, good fatigue resistance and stability, and long service life. The device reproduces a holographic image with a high signal-to-noise ratio, can simultaneously space multiplex and angle multiplex, and greatly improves data storage density and capacity.

Description

Polarization holographic optical storage device with photochromic material film as recording medium

technical field

The utility model relates to a holographic optical storage device, in particular to a Fourier transformation angle multiplexing polarization holographic optical storage device which uses a photochromic material film as a recording medium.

Background technique

High density, large capacity, and high access speed are the development directions of optical storage technology. Holographic optical storage has become one of the important development directions of optical storage because of its high storage density, large storage capacity and high data access speed. The key to improving storage density and capacity of holographic optical storage is to use multiplexing technologies, such as angle multiplexing, wavelength multiplexing, spatial multiplexing, etc.; because holographic optical storage uses parallel information writing and reading methods, one write and read The amount of data can be very large, so the data access speed is high. Holographic recording medium is one of the key factors of holographic optical storage. There are many holographic recording media, such as silver halide salts, dichromate gelatin, photopolymers, photorefractive crystals, photochromic materials, etc.; among them, silver halide salts, dichromate gelatin, and photopolymers are disposable Use recording media; photorefractive crystals and photochromic materials are rewritable recording media, and do not require post-processing such as developing and fixing, so they have significant technical advantages. At present, most holographic optical storage devices use bulk photorefractive crystals as rewritable holographic recording media or photopolymer thin films as write-once-read-multiple-read holographic recording media. storage. This hologram records an intensity-modulated grating, and the object light and reference light must have the same polarization component. If the polarization directions of the object light and reference light are perpendicular to each other, the light intensity of the synthetic light field will not be modulated, and no intensity modulation will be formed. raster. However, if the recording medium has light-induced anisotropy (photobirefringence or photodichroism), the absorption coefficient or refractive index of the medium for polarized light will be modulated and changed under the irradiation of the synthetic light field, so that the polarization can be recorded. Modulation grating. When a hologram is illuminated with polarized light, an object wave orthogonal to its polarization state is reproduced. The necessary condition for the realization of polarization holography is that the recording medium has light-induced anisotropy, and its advantage is that it can obtain a reconstructed image with a higher signal-to-noise ratio than ordinary holography.

Contents of the invention

The purpose of this utility model is to provide a high-density holographic optical storage that uses photochromic material film as a rewritable holographic recording medium, uses its light-induced anisotropy to perform orthogonal polarization holographic recording, and obtains a reproduced image with a high signal-to-noise ratio. The device solves the technical problem of the low signal-to-noise ratio of the reproduced image of the common holographic optical storage device in the background art.

The technical solution of the utility model is: a polarization holographic optical storage device with a photochromic material film as a recording medium, including a read-write laser 1, a total shutter 2, a polarization beam splitting prism 3, an object optical path, a reference optical path, and a holographic recording medium 12. The total shutter 2, the polarizing beam splitter prism 3, and the object optical path are sequentially arranged in the propagation direction of the light beam emitted by the read-write laser 1; the object optical path includes an object light shutter 4, a beam expander collimating lens group 5, and a spatial light modulation 6, the first Fourier transform lens 7, the object light space filter stop 8, the first inverse Fourier transform lens 9 and the second Fourier transform lens 11, wherein the spatial light modulator 6 is located at the front focal plane of the first Fourier transform lens 7 , the object light space filter diaphragm 8 is positioned at the back focal plane of the first Fourier transform lens 7, the front focal plane of the first inverse Fourier transform lens 9 coincides with the back focal plane of the first Fourier transform lens 7, the first inverse Fourier transform lens The rear focal plane of 9 coincides with the front focal plane of the second Fourier transform lens 11, and the holographic recording medium 12 is positioned at the rear focal plane of the second Fourier transform lens 11; Optical space filter diaphragm 16, rotating reflector 17, first lens 18 and second lens 19, wherein reflector 13 is arranged on the direction of light beam propagation reflected by polarization beam splitter prism 3, first lens 18 and second lens 19 constitute 4F structure , the rotating mirror 17 is located on the front focal plane of the lens 18 , and the holographic recording medium 12 is located on the back focal plane of the lens 19 .

Above-mentioned object optical path also comprises the quarter-wave plate 10 for object light that is arranged between the first Fourier transform lens 9 and the second Fourier transform lens 11; Above-mentioned reference optical path also includes being arranged at light intensity attenuator 14 and reference light A quarter-wave plate 15 is used for the reference light between the spatial filtering diaphragms 16 .

The above-mentioned holographic optical storage device comprises a polarizer 21, a second inverse Fourier transform lens 22, a diffractive optical shutter 23, and an image acquisition device 24 which are sequentially arranged in the beam propagation direction of the read-write laser 1, wherein the polarizer 21 is located between the holographic recording medium 12 and the Between the second inverse Fourier transform lens 22, the front focal plane of the second inverse Fourier transform lens 22 coincides with the rear focal plane of the second inverse Fourier transform lens 11, and the photosensitive surface of the image acquisition device 24 is positioned at the second inverse Fourier transform lens 22. back focal plane.

Above-mentioned object optical path comprises the quarter-wave plate 10 for object light that is arranged between the first inverse Fourier transform lens 9 and the second Fourier transform lens 11; A quarter-wave plate 15 is used for the reference light between the filter apertures 16 ; a quarter-wave plate 20 for diffracted light is arranged between the holographic recording medium 12 and the polarizer 21 .

The above-mentioned holographic optical storage device includes an erasing laser 25, which is a continuous or pulsed laser whose output wavelength is close to the metastable absorption peak of the photochromic material. Intersect and overlap on the medium 12.

The above-mentioned holographic recording medium 12 is a photochromic material film with light-induced anisotropy, and the photochromic material film is a bacillus rhodopsin film in a biomolecular material or a fulginic anhydride film in an organic molecular material.

The utility model has the following advantages:

1. Use biomolecular photochromic material—bacteriorhodopsin film or organic photochromic material—fulginic anhydride film as rewritable holographic recording medium, which has high photosensitivity, high spatial resolution, fatigue resistance and stability Good performance and long service life.

2. Utilize the light-induced anisotropy of photochromic materials, and use orthogonal linearly polarized light or orthogonal circularly polarized light to record polarization-modulated holograms. The recording medium has light-induced anisotropy (photo-induced birefringence or photo-dichroism), and the absorption coefficient or refractive index of the medium for polarized light will undergo a modulation change under the irradiation of a synthetic light field, so that the polarization-modulated grating can be recorded , when the hologram is illuminated with polarized light, the object light wave orthogonal to its polarization state will be reproduced, thereby obtaining a reconstructed image with a higher signal-to-noise ratio than ordinary holograms.

3. The hologram is recorded on the spectral surface of the Fourier transform lens, which can simultaneously multiplex the angle and space, and improve the data storage density and capacity.

Description of drawings

Fig. 1 is a schematic diagram of a polarization holographic optical storage device in which a photochromic material film is used as a recording medium;

Fig. 2 is the law of the periodic variation of the polarization state of the interference field in the recording medium when the orthogonal linearly polarized light and the orthogonal circularly polarized light are recorded;

Fig. 3 is the relationship between the polarization state of the diffracted light and the polarization state of the reference light when the hologram recorded by the orthogonal linearly polarized light and the orthogonal circularly polarized light is reproduced;

Figure 4 is a schematic diagram of using 4F structure in the reference light path and realizing angle multiplexing by rotating the mirror, which is characterized in that although the incident angle of the reference light changes, the position of the incident point on the recording medium remains unchanged, and it is always a plane wave;

Fig. 5 is the absorption spectrum of the ground state (B state) and the metastable intermediate state (M state) of the biomolecular photochromic material-bacillus rhodopsin film in the embodiment.

Detailed ways

A photochromic material film with light-induced anisotropy is used as a rewritable holographic recording medium. In the embodiment, a biomolecular photochromic material—bacteriorhodopsin or an organic photochromic material—fulginic anhydride is used. The bacillus rhodopsin film or fulgid anhydride film is a film prepared by mixing bacillus rhodopsin or fulgid anhydride with a high molecular weight polymer (such as gelatin, polyvinyl alcohol, PMMA, etc.) in a certain proportion on a transparent glass. A transparent protective layer is applied to protect the film from mechanical damage. Bacteriorhodopsin is a light-sensitive protein extracted from halophilic bacteria. The full name is bacteriorhodopsin (bacteriorhodopsin), referred to as bacteriorhodopsin or BR. Bacillus rhodopsin can be wild type, chemically modified or genetically modified. What used in the present embodiment is a kind of genetically modified BR-D96N bacillhodopsin film, film thickness about 80m, accompanying drawing 5 is the absorption spectrum of its ground state (B state) and metastable intermediate state (M state), The absorption peak of the B state is at 570nm, and the absorption peak of the M state is at 410nm. In this embodiment, a continuous He-Ne laser with a wavelength of 633 nm and a power of 2 mW is selected as the recording and reading light source. The light source for erasing the hologram is a semiconductor laser with a wavelength of 405nm.

When orthogonal linearly polarized light is used for recording, the polarization holographic optical storage device with a photochromic material film as the recording medium includes a read-write laser 1, a total shutter 2, a polarization beam splitter prism 3, an object optical path, a reference optical path, and a holographic recording medium 12; The total shutter 2, the polarization beam splitting prism 3, and the object optical path are sequentially arranged in the propagation direction of the light beam emitted by the read-write laser 1; Transformation lens 7, object light spatial filter diaphragm 8, first inverse Fourier transform lens 9 and second Fourier transform lens 11, wherein spatial light modulator 6 is located at the front focal plane of first Fourier transform lens 7, and object light space filters light Stop 8 is positioned at the back focal plane of first Fourier transform lens 7, and the front focal plane of first Fourier transform lens 9 coincides with the back focal plane of first Fourier transform lens 7, and the back focal plane of first Fourier transform lens 9 coincides with The front focal planes of the second Fourier transform lens 11 overlap, and the holographic recording medium 12 is positioned at the rear focal plane of the second Fourier transform lens 11; the reference optical path includes a mirror 13, a light intensity attenuator 14, a reference light spatial filter diaphragm 16, a rotating Reflector 17, first lens 18 and second lens 19, wherein reflector 13 is arranged on the polarized beam splitter 3 reflected light beam propagation direction, first lens 18 and second lens 19 constitute 4F structure, and rotating reflector 17 is positioned at lens 18 The front focal plane of the holographic recording medium 12 is located at the back focal plane of the lens 19 .

When adopting orthogonal circular polarized light recording, a quarter-wave plate 10 for object light can be set between the first inverse Fourier transform lens 9 and the second Fourier transform lens 11 in the object light path, and the light intensity is attenuated in the reference light path A quarter-wave plate 15 for reference light is set between the filter 14 and the reference light spatial filter diaphragm 16 .

When using orthogonal linearly polarized light to read, the holographic optical storage device also includes a polarizer 21, a second inverse Fourier transform lens 22, a diffractive optical shutter 23, and an image acquisition device 24, which are sequentially arranged in the beam propagation direction of the read-write laser 1 , wherein the polarizer 21 is located between the holographic recording medium 12 and the second inverse Fourier transform lens 22, the front focal plane of the second inverse Fourier transform lens 22 coincides with the back focal plane of the second Fourier transform lens 11, and the image acquisition device 24 The photosensitive surface is located at the rear focal plane of the second inverse Fourier transform lens 22 .

When adopting orthogonal circularly polarized light to read out, a quarter-wave plate 10 for object light can be set between the first inverse Fourier transform lens 9 and the second Fourier transform lens 11 in the object light path, and the light intensity in the reference light path A quarter-wave plate 15 for reference light is provided between the attenuator 14 and the spatial filter diaphragm 16 for reference light, and a quarter-wave plate 20 for diffracted light is provided between the hologram recording medium 12 and the polarizer 21 .

When the hologram needs to be erased, the holographic optical storage device can be equipped with an erasing laser 25, the erasing laser 25 is a continuous or pulsed laser whose output wavelength is close to the metastable absorption peak of the photochromic material, and its beam is the same as the beam of the read-write laser 1 Intersect and overlap on the holographic recording medium 12 .

As shown in FIG. 1 , the unpolarized He-Ne laser 1 is split by a polarization beam splitter 3 to form mutually orthogonal linearly polarized object light (horizontal polarization) and reference light (vertical polarization). The object light uniformly illuminates the spatial light modulator 6 after passing through the beam expander collimator 5 . The first Fourier transform lens 7 and the first inverse Fourier transform lens 9 form a 4F structure, the spatial light modulator 6 is located at the front focal plane of the first Fourier transform lens 7, and the object light spatial filter diaphragm 8 is located at the first The rear focal plane of a Fourier transform lens 7; the first inverse Fourier transform lens 9 carries out Fourier inverse transform to the frequency spectrum after spatial filtering, and forms the image of the spatial light modulator 6 after low-pass filtering on its rear focal plane . The second Fourier transform lens 11 is confocal with the first inverse Fourier transform lens 9 , and the image of the front focal plane of the second Fourier transform lens 11 forms a frequency spectrum on its rear focal plane after Fourier transform. The second Fourier transform lens 11 and the second inverse Fourier transform lens 22 form another 4F structure, and the holographic recording medium 12 is located at the back focal plane of the second Fourier transform lens 11 to record the Fourier transform spectrum hologram, after After the inverse Fourier transform of the second inverse Fourier transform lens 22 , an image is formed at its rear focal plane. The CCD image acquisition device 24 is located at the rear focal plane of the second inverse Fourier transform lens 22 to capture object images and diffraction images.

The reference light path first folds the light path through the reflector 13, and then intercepts the part with a relatively uniform light intensity in the center of the Gaussian beam through the reference light spatial filter diaphragm 16, and then reflects the reference light to the holographic recording medium 12 and the object light through the rotating reflector 17. coincide. The reference light and the object light are incident on the same side of the holographic recording medium 12 at an angle of 90°, and may be symmetrical or asymmetrical to the normal direction of the holographic recording medium 12 . In order to realize angle multiplexing, another 4F structure composed of a first lens 18 and a second lens 19 is set between the rotating mirror 17 and the holographic recording medium 12, so that the reference light incident angle can be changed by rotating the mirror 17, and at the same time To ensure that the incident spot position of the reference light on the holographic recording medium 12 remains unchanged, the schematic diagram of the optical path is shown in Figure 4, and the change of the reference angle is twice the rotation angle of the mirror.

During holographic recording, the diffractive light shutter 23 is closed to prevent the object light from entering the image acquisition device 24, the object light shutter 4 is opened, and the recording exposure time is controlled by controlling the total shutter 2. The continuously adjustable light intensity attenuator 14 is used to adjust the intensity ratio of the object light and the reference light. By rotating the rotating mirror 17 to different angles, multiple holograms can be recorded on the same spatial position of the holographic recording medium 12 . By moving the holographic recording medium 12, multiple holograms can also be recorded in different spatial positions. If adopting orthogonal circular polarized light to record, it is necessary to add object light quarter-wave plate 10 and reference light quarter-wave plate 15 respectively in object light and reference light paths, and object light and reference light become left-handed and Right-handed polarized light.

During holographic reproduction and readout, the object light shutter 4 is closed to block the object light, the diffracted light shutter 23 is opened to receive diffracted light, and the total shutter 2 is controlled for reproduction and readout. Adjusting the light intensity attenuator 14 can control the reproduction light intensity. Rotating the rotating mirror 17 to the corresponding angle during holographic recording can respectively select and read out each hologram to be reproduced. By moving the holographic recording medium 12 to the corresponding position during holographic recording, holograms recorded in different spatial positions can be read out. The polarizer 21 is used to selectively block scattered noise through diffracted light, so as to improve the signal-to-noise ratio. If the recording mode is the orthogonal circular polarized light recording, then it is necessary to add a diffracted light quarter-wave plate 20 before the polarizer 21, so that the diffracted light and scattering noise of the orthogonal circular polarization are converted into the diffracted light and the scattered noise of the orthogonal linear polarization. scattered noise.

Principle of the utility model:

Ordinary holography uses the interference of object light and reference light with the same polarization direction to form a light intensity modulation grating. The object light and reference light of orthogonal polarization holography have mutually orthogonal polarization directions (mutually orthogonal linearly polarized light or mutually orthogonally polarized light), and the light intensity distribution of the formed interference field is uniform, and cannot produce intensity Modulation grating. However, the polarization state of the interference field generated by the orthogonal polarization is periodically modulated, and a polarization state modulation grating can be formed, as shown in FIG. 2 . For isotropic recording media that respond only to light intensity, polarization-modulated gratings cannot be recorded. For recording media with light-induced anisotropy, molecules can respond to the polarization state of light, and the periodic changes in the polarization state of the interference field will cause periodic changes in the orientation of the molecular electric dipole moment, and the molecules will generate a wave along the long axis of elliptically polarized light. Or the optical axis of the polarization direction of linearly polarized light, the orientation of the electric dipole moment is perpendicular to the optical axis direction, resulting in properties similar to uniaxial crystals. Some photochromic materials have this light-induced anisotropy, so that the orthogonally polarized hologram recording of two beams of light whose polarization states are orthogonal to each other can be realized.

When the hologram is reproduced with polarized reference light, the polarized grating recorded on the holographic recording medium diffracts the reference light to form a diffraction image including intensity, phase and polarization information. The polarization state of the diffracted light is related to the polarization state of the reproduction reference light and the polarization state of the recording light, as shown in FIG. 3 . The diffraction efficiency is related to the polarization state of the recording light and the polarization state of the reproduced reference light. When the original reference light is reproduced, the highest diffraction efficiency can be obtained, and the polarization of the diffracted light is always orthogonal to the polarization of the reproduced light. That is, if the orthogonal line When polarized light is recorded and reproduced with the original reference light, the diffracted light is linearly polarized light orthogonal to the reference light; if it is recorded with orthogonal circular polarized light and reproduced with the original reference light, the diffracted light is orthogonal to the reference light circular polarized light. The diffraction efficiency of the hologram recorded with orthogonal circularly polarized light is equivalent to that of the ordinary same-polarized recorded hologram; the diffraction efficiency of the hologram recorded with orthogonal linearly polarized light is about half of the former.

Scattering noise is generally partially polarized light, mostly components of the same polarization state as the reproduced reference light. For the case of orthogonal linearly polarized light recording, an analyzer can be placed in front of the image acquisition device during readout, and the diffraction image can be selected to prevent the scattering noise orthogonal to it from entering the image acquisition device; for the case of orthogonal circular polarized light recording, In addition to placing the analyzer in front of the image acquisition device during reproduction and readout, a quarter-wave plate needs to be placed in front of the analyzer, so that the mutually orthogonal circular polarized light becomes mutually orthogonal linearly polarized light, Then use the analyzer to separate the diffraction image to prevent the scattering noise and achieve the purpose of improving the signal-to-noise ratio.

Claims (6)

1, a kind of photochromic material film is characterized in that as the polarization holography light storage device of recording medium: described holographic optical memory storage comprises read write laser (1), gross shutter (2), polarization splitting prism (3), thing light path, reference path, holographic recording medium (12); Described gross shutter (2), polarization splitting prism (3), thing light path are successively set on the direction of propagation of read write laser (1) emission light beam; Described thing light path comprises thing optical shutter (4), beam-expanding collimation lens combination (5), spatial light modulator (6), first fourier transform lens (7), thing light spatial filtering diaphragm (8), the first inverse fourier transform lens (9) and second fourier transform lens (11), its spatial light modulator (6) is positioned at the front focal plane of first fourier transform lens (7), thing light spatial filtering diaphragm (8) is positioned at the back focal plane of first fourier transform lens (7), the front focal plane of the first inverse fourier transform lens (9) overlaps with the back focal plane of first fourier transform lens (7), the back focal plane of the first inverse fourier transform lens (9) overlaps with the front focal plane of second fourier transform lens (11), and holographic recording medium (12) is positioned at the back focal plane of second fourier transform lens (11); Described reference path comprises catoptron (13), variable optical attenuator (14), reference light spatial filtering diaphragm (16), rotating mirror (17), first lens (18) and second lens (19), wherein catoptron (13) is arranged on polarization splitting prism (3) the folded light beam direction of propagation, first lens (18) and second lens (19) constitute the 4F structure, rotating mirror (17) is positioned at the front focal plane of lens (18), and holographic recording medium (12) is positioned at the back focal plane of lens (19).

2, photochromic material film according to claim 1 is characterized in that as the polarization holography light storage device of recording medium: described thing light path comprises the thing light quarter-wave plate (10) that is arranged between the first inverse fourier transform lens (9) and second fourier transform lens (11); Described reference path comprises the reference light quarter-wave plate (15) that is arranged between variable optical attenuator (14) and the reference light spatial filtering diaphragm (16).

3, photochromic material film according to claim 1 is as the polarization holography light storage device of recording medium, it is characterized in that: described holographic optical memory storage comprises the polaroid (21) that is successively set on read write laser (1) direction of beam propagation, the second inverse fourier transform lens (22), diffraction light shutter (23), image acquisition device (24), wherein polaroid (21) is positioned between the holographic recording medium (12) and the second inverse fourier transform lens (22), the front focal plane of the second inverse fourier transform lens (22) overlaps with the back focal plane of second fourier transform lens (11), and the photosurface of image acquisition device (24) is positioned at the back focal plane of the second inverse fourier transform lens (22).

4, photochromic material film according to claim 3 is characterized in that as the polarization holography light storage device of recording medium: described thing light path comprises the thing light quarter-wave plate (10) that is arranged between the first inverse fourier transform lens (9) and second fourier transform lens (11); Described reference path comprises the reference light quarter-wave plate (15) that is arranged between variable optical attenuator (14) and the reference light spatial filtering diaphragm (16); Be provided with diffraction light quarter-wave plate (20) between described holographic recording medium (12) and the polaroid (21).

5, according to claim 1 or 2 or 3 or 4 described photochromic material films polarization holography light storage device as recording medium, it is characterized in that: described holographic optical memory storage comprises wipes laser instrument (25), the described laser instrument (25) of wiping is the continuous or pulsed laser of output wavelength near photochromic material metastable state absorption peak, and its light beam is gone up to intersect at holographic recording medium (12) with the light beam of described read write laser (1) and overlapped.

6, photochromic material film according to claim 5 is as the polarization holography light storage device of recording medium, it is characterized in that: described holographic recording medium (12) is for having the photochromic material film of photoinduced anisotropy, and described photochromic material film is bacteriorhodopsin,BR film in the biological molecular material or the fulgide film in the organic molecule material.

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