CN115631774A - Independently calibrated holographic storage optical path system - Google Patents
Independently calibrated holographic storage optical path system Download PDFInfo
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- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
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- G11B7/0065—Recording, reproducing or erasing by using optical interference patterns, e.g. holograms
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
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Abstract
The invention relates to the field of holographic storage, and discloses an independently calibrated holographic storage light path system. The system includes a signal optical path, a reference optical path, a reproduction optical path, a servo optical path, and a storage medium; the storage medium comprises a recording layer and an address layer, wherein a plurality of calibration holographic bit marks and data holographic bit marks are arranged on a light path of the address layer; the signal light path and the reference light path both comprise relay lens groups, and the relay lens groups are used for adjusting the irradiation angles and positions of the signal light and the reference light; the servo light path is independent of the signal light path and the reference light path and is used for identifying the calibration holographic bit mark and the data holographic bit mark; the servo light path includes a collimating lens for adjusting the position of the servo light impinging on the storage medium and a photodetector for receiving and analyzing the servo light reflected back from the address layer of the storage medium. The method is used for solving the problem of how to calibrate and optimize the relative positions of the reference light and the servo light when the holographic storage light path system is reproduced.
Description
Technical Field
The invention relates to the field of holographic storage, in particular to an independently calibrated holographic storage optical path system.
Background
Holographic optical storage uses interference of optical waves to record data page information in a form of hologram in a photosensitive medium, and compared with the conventional optical storage technology, the holographic optical storage has the advantages of large storage capacity, high data transmission rate, short addressing time and the like. In the holographic optical storage technology, a laser beam is divided into two beams, namely reference light and signal light, wherein the signal light carries data page information after being transmitted or reflected by a spatial light modulator, and the signal light and the reference light are interfered in a photosensitive material layer of a storage medium and exposed to form a hologram, so that the information is recorded.
The holographic storage medium is internally provided with an address layer, and annular or spiral grooves or ridge-shaped light paths are distributed on the address layer; the annular groove or the convex ridge is detected by the servo light sensing system to realize accurate positioning, so that quick and convenient data access and storage are realized. The introduction of the servo light path into the holographic optical storage light path system can effectively improve the storage and retrieval efficiency of data.
When reading the hologram, it is necessary to irradiate the same reference light as that used in recording to reproduce the hologram in the storage medium; when the grating stripes in the storage medium are slightly deformed due to external factors, the incident angle and the irradiation position of the reproduced reference light should be slightly changed, so that the wave vectors of the reproduced reference light meet the Bragg matching condition of the hologram, and the signal light is effectively reproduced. In addition, in order to ensure that the data can be completely read when the holographic optical disk recorded with data is read on the same holographic optical drive or other holographic optical drives, the servo beam and the reference beam must be calibrated. Therefore, it is necessary to establish an effective calibration system for calibrating the servo beam and the reference beam so that the head can read the data from the hologram completely during high speed movement.
Disclosure of Invention
The present invention is directed to overcome at least one of the deficiencies of the prior art, and provides an independently calibrated holographic storage optical path system, which is used to solve the problem of how to calibrate and optimize the relative positions of the reference light and the servo light when the holographic storage optical path system is reproduced.
The invention adopts the technical scheme that an independently calibrated holographic storage light path system comprises a signal light path, a reference light path, a reproduction light path, a servo light path and a storage medium; the signal light path and the reference light path respectively generate signal light and reference light, the signal light and the reference light respectively irradiate the storage medium at a certain angle, and the interference exposure is carried out to generate a hologram; the reproduction light path is used for converting the reproduction signal light diffracted by the reference light into a data page image and collecting the data page image; the storage medium comprises a recording layer for storing holograms and an address layer consisting of a number of tracks. A plurality of calibration holographic bit marks and data holographic bit marks are arranged on the light path; the calibration holographic bit mark is used for positioning and recording the calibrated hologram; the data holographic bit mark is used for positioning a hologram for recording data; the signal light path and the reference light path both comprise relay lens groups, and the relay lens groups are used for adjusting the irradiation angles and positions of the signal light and the reference light; the servo light path is independent of the signal light path and the reference light path and is used for identifying the calibration holographic bit mark and the data holographic bit mark; the servo optical path includes a servo laser for generating servo light, a collimating lens for adjusting an irradiation position of the servo light on the storage medium, and a photodetector for receiving and analyzing the servo light reflected from the address layer of the storage medium.
The relay lens group is arranged in the signal light path and the reference light path, so that the irradiation angles and positions of the signal light and the reference light can be adjusted; by providing a collimating lens in the servo light path, the irradiation position of the servo light can be adjusted. The position of the recording layer corresponding to the calibration holographic bit mark on the storage medium records a calibrated hologram, i.e. a calibration hologram. The data hologram bit marks on the storage medium record a hologram of data, i.e. a data hologram, at the corresponding location of the recording layer. In the scheme, before recording the data hologram, the recording of the calibration hologram is carried out at the position of the calibration hologram bit mark of the storage medium. Before the data hologram is reproduced, the calibration hologram is reproduced at the position of the calibration holographic bit mark, the diffraction efficiency and the signal to noise ratio of the calibration hologram are detected through a reproduction light path, the wavelengths of the relay lens group and the reference light are synchronously adjusted, and when the diffraction efficiency and the signal to noise ratio of the calibration hologram reach maximum values, the calibration of the optimal irradiation angle, the optimal position and the optimal wavelength of the reference light is completed. Before the data hologram is reproduced, servo light reflected from an address layer of a storage medium is detected and analyzed by a photoelectric detector, and a calibration lens is synchronously adjusted to finish the calibration of the optimal position of the servo light. The method calibrates the position of a calibration lens, the position of a relay lens group and the irradiation position and angle of a reference beam in a holographic storage optical path system to the best, and then reproduces the data hologram.
The reconstruction path of the present solution comprises a fourth fourier lens for imaging and an image sensor for collecting the data page image and analyzing the diffraction efficiency and the signal-to-noise ratio. In order to convert the frequency domain light field of the data page reproduced by the reference light into spatial domain light field imaging, a fourth fourier lens is arranged in front of the image sensor. The fourth Fourier lens performs inverse Fourier transform on the frequency domain light field and projects the spatial domain image onto a target surface of the image sensor.
Preferably, the servo light is perpendicularly incident on the storage medium, and the signal light and the reference light are obliquely incident on the storage medium at the same or different angles, respectively. The incident angle between the signal light and the reference light may be an acute angle or an obtuse angle, and when the incident angle between the signal light and the reference light is 90 °, the storage performance is optimal.
Preferably, the servo optical path further comprises a first half wave plate, a quarter wave plate, a first polarization beam splitter and an astigmatic focusing lens group; the first half-wave plate is used for converting the servo light into P-polarization servo light; the quarter-wave plate is used for converting incident P-polarization servo light into circular polarization servo light and converting the circular polarization servo light reflected by the storage medium into S-polarization servo light; the first polarization beam splitter is used for reflecting the S-polarization servo light; the astigmatic focusing lens group is used for converging the S-polarized servo light. The servo light is converted into P-polarization servo light through the first half-wave plate, the P-polarization servo light is converted into circular polarization servo light through the quarter-wave plate after passing through the first polarization beam splitter, and the circular polarization servo light vertically irradiates an address layer of a storage medium and then returns to the original path. The reflected circular polarization servo light is converted into S polarization servo light through the quarter wave plate, and the S polarization servo light is reflected to the astigmatic focusing lens group through the first polarization beam splitter and finally captured by the photoelectric detector. According to the scheme, the photoelectric detector analyzes the reflected locking error signal and the reflected tangential push-pull signal of the servo light path, and the irradiation position of the servo light can be detected.
When the servo light convergence light spot is positioned in the middle of the calibration holographic bit mark or the data holographic bit mark, the track locking error signal and the tangential push-pull signal are both positioned at a zero value between a positive maximum value and a negative maximum value.
The track locking error signal is used for detecting the condition that the servo light spot deviates from the track, and when the servo light spot is positioned on the central line of the track, the track locking error signal is 0; when the servo light spot gradually deviates from the track, the track locking error signal gradually tends to a maximum value or a minimum value; when the servo light spot is completely off track, the tracking error signal becomes 0.
The tangential push-pull signal is used for detecting a calibration holographic bit mark or a data holographic bit mark of a track, namely a holographic bit mark, the holographic bit mark can be a notch, and when a servo light spot is positioned in the center of the notch, the tangential push-pull signal is 0; when the servo light spot gradually deviates from the notch, the tangential push-pull signal gradually tends to a maximum value or a minimum value; when the servo light spot is completely out of the notch, the tangential push-pull signal becomes 0.
The signal light and the reference light are spherical waves, and the holograms are recorded by using the spherical waves for shift multiplexing and wavelength multiplexing, so that the capacity of the holograms stored on the same track can be improved, and the storage capacity of the storage medium is improved.
Preferably, the signal optical path and the reference optical path both include a common read-write laser and a common beam expander, the read-write laser is configured to generate read-write light, and the beam expander is configured to perform beam expansion on the read-write light.
Preferably, the signal optical path and the reference optical path comprise nyquist filters for intercepting unwanted spatial frequency components to control hologram size.
According to the scheme, the beam expander is used for expanding the beams of the reading and writing light so as to solve the problem that the reading and writing light emitted by the reading and writing laser is uneven; the light of the middle uniform part is selected by a Nyquist filter to obtain uniform signal light and reference light.
Preferably, the relay lens group includes a fixed first fourier lens and a movable second fourier lens, and the irradiation positions and angles of the signal light and the reference light are adjusted by moving the second fourier lens. The signal optical path and the reference optical path comprise a first Fourier lens and a second Fourier lens, wherein the position of the first Fourier lens is fixed, and the position of the second Fourier lens is movable. The signal optical path and the reference optical path in the scheme can share the first Fourier lens and the second Fourier lens, or can not share the first Fourier lens and the second Fourier lens.
Further, the signal optical path includes a second polarization beam splitter and a spatial light modulator, the second polarization beam splitter is configured to split the read-write light into the signal light and the reference light, and the spatial light modulator is configured to load the data page image to the signal light.
Further, the signal optical path and the reference optical path comprise a third polarization beam splitter, and the relay lens group and the nyquist filter are shared by the signal optical path and the reference optical path; the signal light and the reference light are split by a third polarization beam splitter and are irradiated to the storage medium at the same or different angles, respectively.
Compared with the prior art, the invention has the beneficial effects that:
the holographic storage optical path system is provided with a servo unit, addresses on a storage medium are addressed and positioned through the servo unit, and a hologram is stored in a designated position of the storage medium. In the reading process, the irradiation position and angle of the reference light can be adjusted by moving the second Fourier lens, and the diffraction efficiency and the signal-to-noise ratio of the hologram can reach the maximum value by combining the wavelength of the reference light and the movement of the storage medium. After the diffraction efficiency and the signal-to-noise ratio are optimized to the maximum values, the horizontal position and the vertical position of a servo light spot are adjusted through a calibration lens in a servo unit, so that the holographic bit mark can be locked by the servo light again, and the data page information can be reproduced by the reference light with a high signal-to-noise ratio on the whole storage medium when the servo light is positioned on the holographic bit mark. In the scheme, even under the condition that the storage medium shrinks and expands, the data in the storage medium can be accurately read; meanwhile, the compatibility of reading the data stored in the hologram among different devices is enhanced.
Drawings
Fig. 1 is a schematic diagram of a holographic storage optical path system according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of the irradiation of signal light, reference light and servo light onto a storage medium according to the present invention.
Fig. 3 is a schematic diagram of a holographic storage optical path system according to another embodiment of the present invention.
Description of the reference symbols: servo light 1, reference light 2, signal light 3; recording layer 120, address layer 121, data hologram bit mark 122, calibration hologram bit mark 123;
a servo laser 10, a first half wave plate 20, a first polarization beam splitter 30, a quarter wave plate 40, an astigmatic focal lens group 50, a photodetector 60, and a collimating lens 140;
the optical pickup comprises a read-write laser 70, a beam expander 80, a second half-wave plate 21, a third half-wave plate 22, a fourth half-wave plate 23, a second polarization beam splitter 31, a third polarization beam splitter 32, a spatial light modulator 90, a first Fourier lens 130, a second Fourier lens 131, a third Fourier lens 160, a reference light objective lens 170, a fourth Fourier lens 180, an image sensor 190 and a Nyquist filter 200.
Detailed Description
The drawings are only for purposes of illustration and are not to be construed as limiting the invention. For a better understanding of the following embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
As shown in fig. 1 and 2, the present invention adopts the technical solution that an independently calibrated holographic storage optical path system includes a signal optical path, a reference optical path, a reconstruction optical path, a servo optical path, and a storage medium; the signal light path and the reference light path respectively generate signal light 3 and reference light 2, the signal light 3 and the reference light 2 respectively irradiate to a storage medium at a certain angle, and interference exposure is carried out to generate a hologram; the reproduction optical path is used for converting the reproduction signal light 3 diffracted by the reference light 2 into a data page image and collecting the data page image; the storage medium includes a recording layer 120 for storing holograms and an address layer 121, the address layer 121 being composed of several tracks. A plurality of calibration holographic bit marks 123 and data holographic bit marks 122 are arranged on the light path; the alignment holographic bit mark 123 is used for positioning and recording the alignment hologram; data holographic bit marks 122 are used to locate holograms that record data; the signal light path and the reference light path both comprise relay lens groups, and the relay lens groups are used for adjusting the irradiation angles and positions of the signal light 3 and the reference light 2; the servo optical path is independent of the signal optical path and the reference optical path and is used for identifying the calibration holographic bit mark 123 and the data holographic bit mark 122; the servo optical path comprises a servo laser 10, a collimating lens 140 and a photodetector 60, the servo laser 10 being adapted to generate servo light 1, the collimating lens 140 being adapted to adjust the position of the servo light 1 on the storage medium, and the photodetector 60 being adapted to receive and analyze the servo light 1 reflected back from the address layer 121 of the storage medium.
The scheme is characterized in that relay lens groups are arranged in a signal light path and a reference light path, so that the irradiation angles and the positions of the signal light 3 and the reference light 2 can be adjusted; by providing the collimating lens 140 in the servo light path, the irradiation position of the servo light 1 can be adjusted. The position of the recording layer 120 corresponding to the alignment hologram bit mark 123 on the storage medium records an alignment hologram, i.e., an alignment hologram. A hologram of data, i.e., a data hologram, is recorded at a position of the recording layer 120 corresponding to the data hologram bit mark 122 on the storage medium. In the scheme, before recording the data hologram, the recording of the calibration hologram is firstly carried out at the position of a calibration hologram bit mark 123 of the storage medium. Before the data hologram is reproduced, the calibration hologram is reproduced at the calibration hologram bit mark 123, the diffraction efficiency and the signal to noise ratio of the calibration hologram are detected through a reproduction light path, the wavelength of the relay lens group and the wavelength of the reference light 2 are synchronously adjusted, and when the diffraction efficiency and the signal to noise ratio of the calibration hologram reach maximum values, the calibration of the optimal irradiation angle, the position and the wavelength of the reference light 2 is completed. In this scheme, before the data hologram is reproduced, the servo light 1 reflected from the address layer 121 of the storage medium is detected and analyzed by the photodetector 60, and the alignment lens 140 is synchronously adjusted to complete the alignment of the optimum position of the servo light 1. The scheme calibrates the position of the calibration lens 140, the position of the relay lens group and the irradiation position and angle of the reference light 2 beam in the holographic storage optical path system to the optimal value, and then reproduces the data hologram.
The reconstruction path of the present solution comprises a fourth fourier lens 180 for imaging and an image sensor 190 for collecting the data page image and analyzing the diffraction efficiency and the signal-to-noise ratio. In order to convert the frequency domain light field of the data page reproduced by the reference light 2 into spatial domain light field imaging, a fourth fourier lens 180 is arranged in front of the image sensor 190. The fourth fourier lens 180 performs an inverse fourier transform on the frequency domain light field and projects a spatial domain image onto the target surface of the image sensor 190.
Preferably, the servo light 1 is perpendicularly incident on the storage medium, and the signal light 3 and the reference light 2 are obliquely incident on the storage medium at the same or different angles, respectively. The incident angle between the signal light 3 and the reference light 2 can be an acute angle or an obtuse angle, and when the incident angle between the signal light 3 and the reference light 2 is 90 degrees, the holographic optical storage performance is optimal.
Preferably, the servo optical path further comprises a first half wave plate 20, a quarter wave plate 40, a first polarizing beam splitter 30 and an astigmatic focal lens group 50; the first half-wave plate 20 is used for converting the servo light 1 into P-polarization servo light; the quarter-wave plate 40 is used for converting the incident P-polarization servo light into circular polarization servo light, and simultaneously converting the circular polarization servo light reflected by the storage medium into S-polarization servo light; the first polarization beam splitter 30 is used for reflecting the S-polarization servo light; the astigmatic focusing lens group 50 serves to condense the S-polarized servo light. The servo light 1 of the scheme is converted into P-polarized servo light through the first half-wave plate 20, the P-polarized servo light is converted into circular-polarized servo light through the quarter-wave plate 40 after passing through the first polarization beam splitter 30, and the circular-polarized servo light vertically irradiates on the address layer 121 of the storage medium and returns to the original path. The reflected circular polarization servo light is converted into S polarization servo light through the quarter wave plate 40, and the S polarization servo light is reflected to the astigmatic focusing lens assembly 50 through the first polarization beam splitter 30 and finally captured by the photodetector 60. According to the scheme, the photoelectric detector 60 analyzes the reflected locking error signal and the reflected tangential push-pull signal of the servo light path, and the irradiation position of the servo light 1 can be detected.
The track-locking error signal and the tangential push-pull signal are detected by the photodetector 60, the position of the servo light 1 convergence spot is detected, and when the servo light 1 convergence spot is located in the middle of the calibration holographic bit mark 123 or the data holographic bit mark 122, the track-locking error signal and the tangential push-pull signal are both located at zero between the positive and negative maximum values.
The track locking error signal is used for detecting the condition that the servo light spot deviates from the track, and when the servo light spot is positioned on the central line of the track, the track locking error signal is 0; when the servo light spot gradually deviates from the track, the track locking error signal gradually tends to a maximum value or a minimum value; when the servo light spot is completely off track, the tracking error signal becomes 0.
The tangential push-pull signal is used for detecting a calibration holographic bit mark 123 or a data holographic bit mark 122 of a track, namely a holographic bit mark, the holographic bit mark can be a notch, and when a servo light spot is positioned in the middle of the notch, the tangential push-pull signal is 0; when the servo light spot gradually deviates from the notch, the tangential push-pull signal gradually tends to a maximum value or a minimum value; when the servo light spot is completely out of the notch, the tangential push-pull signal becomes 0.
The signal light 3 and the reference light 2 are both spherical waves, and the holograms are recorded by using the spherical waves to perform shift multiplexing and wavelength multiplexing, so that the capacity of the holograms stored on the same track can be improved, and the storage capacity of the storage medium is improved.
Preferably, the signal optical path and the reference optical path both include a common read-write laser 70 and a common beam expander 80, where the read-write laser 70 is configured to generate read-write light, and the beam expander 80 is configured to perform beam expansion on the read-write light.
Preferably, the signal optical path and the reference optical path include a nyquist filter 200 located on a spectrum plane of the signal light 3, the nyquist filter 200 being for intercepting unnecessary spatial frequency components on the spectrum plane of the signal light 3 to control a hologram size.
In the present scheme, the beam expander 80 expands the beam of the reading/writing light to overcome the problem that the reading/writing light emitted from the reading/writing laser 70 is non-uniform.
Preferably, the relay lens group includes a fixed first fourier lens 130 and a movable second fourier lens 131, and the irradiation positions and angles of the signal light 3 and the reference light 2 are adjusted by moving the second fourier lens 131. The signal optical path and the reference optical path share a first Fourier lens 130 and a second Fourier lens 131, the position of the first Fourier lens 130 is fixed, and the position of the second Fourier lens 131 is movable.
Further, the signal optical path includes a second polarization beam splitter 31 and a spatial light modulator 90, the second polarization beam splitter 31 is configured to split the reading and writing light into the signal light 3 and the reference light 2, and the spatial light modulator 90 is configured to load the data page image to the signal light 3.
Further, the signal and reference optical paths include a third polarization beam splitter 32, and the relay lens group and the nyquist filter 200 are shared by the signal and reference optical paths; the signal light 3 and the reference light 2 are split by a third polarization beam splitter 32 and are irradiated to the storage medium at the same or different angles, respectively.
In the present embodiment, most of the signal optical path and the reference optical path share the same propagation path in the process from the laser light source to the storage medium. The signal light 3 and the reference light 2 are split by the third polarization beam splitter 32 at the end of the optical path thereof, near the storage medium, and then irradiate the storage medium at the same or different angles. The specific optical path propagation path is as follows:
the read-write laser 70 generates read-write light, and the read-write light is adjusted to be read-write light with a certain polarization direction by the second half-wave plate 21 after being expanded by the beam expander 80. The read-write light passes through the second polarization beam splitter 31 and is converted into signal light 3 in the P polarization direction and reference light 2 in the S polarization direction. The reference light 2 and the signal light 3 are orthogonal in the off-normal direction, and the ratio is 1:1. The signal light 3 in the P polarization direction carries data information after passing through the spatial light modulator 90. The signal light 3 in the P-polarization direction and the reference light 2 in the S-polarization direction sequentially pass through the first fourier lens 130, the nyquist filter 200, the second fourier lens 131, and the third half-wave plate 22 to be converted into the reference light 2 in the P-polarization direction and the signal light 3 in the S-polarization direction. The reference light 2 in the P polarization direction passes through the third polarization beam splitter 32 and then passes through the fourth half-wave plate 23, and is converted into the reference light 2 in the S polarization direction. The signal light 3 in the S-polarization direction passes through the third polarization beam splitter 32 and the third fourier lens 160 in this order. Finally, the signal light 3 in the S-polarization direction interferes with the reference light 2 in the S-polarization direction in the recording layer 120 of the storage medium to form interference fringes. The hologram is stored in the recording layer 120 of the storage medium in the form of interference fringes.
During reproduction, the spatial light modulator 90 has no input signal, only the reference light 2 irradiates on the hologram recorded in the storage medium, the obtained diffracted light continuously propagates along the propagation direction of the original signal light 3 after passing through the storage medium, and the data page image is reproduced through collection of a reproduction light path.
In another embodiment, as shown in fig. 3, the signal and reference optical paths have separate first and second fourier lenses 130 and 131 and nyquist filters 200, respectively. The second fourier lens 131 that moves the signal optical path can adjust the irradiation position and angle of the signal light 3. The irradiation position and angle of the reference light 2 can be adjusted by moving the second fourier lens 131 of the reference light path.
The method for inscribing the calibration hologram and the data hologram comprises the following steps:
s11, moving the calibration lens 140 and the second Fourier lens 131 to initial positions, so that under the condition that a convergence spot of the servo light 1 is focused on the address layer 121, a hologram generated by interference exposure of reference light 2 and signal light 3 is effectively positioned on the recording layer 120 of the storage medium;
s12, fixing a calibration lens 140 and a second Fourier lens 131, moving a storage medium, enabling a servo light spot to be located at a calibration holographic bit mark 123, and recording a calibration hologram at the calibration holographic bit mark 123;
s13, moving the storage medium to enable the servo light spot to be located at the other calibration holographic bit mark 123, and recording the next calibration hologram at the calibration holographic bit mark 123;
s14, repeating the step S13 for a plurality of times to ensure that a plurality of calibration holograms are successfully recorded;
s15, moving the storage medium to enable the servo light spot to be located at the data holographic bit mark 122, and recording a data hologram at the data holographic bit mark 122;
s16, moving the storage medium to enable the servo light spot to be located at another data holographic bit mark 122, and recording a next data hologram at the data holographic bit mark 122;
s17, repeating the step S16, and recording the whole disc of data hologram;
in step S11, the method for moving the collimating lens 140 and the second fourier lens 131 to the initial positions is: the light path simulation design ensures that the converging light spot of the servo light 1 is on the plane of the track of the storage medium (i.e. the address layer 121), and meanwhile, the interference area of the reference light 2 and the signal light 3 can effectively cover the storage medium, and the positions of the collimating lens 140 and the second fourier lens 131 at this time are initial positions.
The calibration of the reference light 2 and the servo light 1 and the reading method of the data hologram in the scheme are specifically as follows:
s21, moving a storage medium, moving a convergence light spot of the servo light 1 to the position near the calibration holographic bit mark 123, and fixing the positions of the calibration lens 140 and the storage medium;
s22, adjusting the wavelength of the reference light 2 and finely adjusting the positions of the second Fourier lens 131 and the storage medium, and when the diffraction efficiency and the signal-to-noise ratio of the calibration hologram at the calibration holographic bit mark 123 reach the best, fixing the position of the second Fourier lens 131 and the parameters of the reference light 2;
s23, moving the position of the calibration lens 140 to enable the servo light spot to be located at the position of the calibration holographic bit mark 123 and fixing the position of the calibration lens 140;
s24, moving the storage medium to enable the servo light spot to be located at the next calibration holographic bit mark 123 and reproducing the calibration hologram at the calibration holographic bit mark 123;
s25, repeating the step S24 for a plurality of times to ensure that the reproduced signal-to-noise ratio of the plurality of calibration holograms meets the minimum signal-to-noise ratio requirement after the second Fourier lens 131 and the calibration lens 140 are fixed;
s26, moving the storage medium, enabling the servo light 1 to converge light spots to be located at the data holographic bit marks 122, and reproducing data holograms at the data holographic bit marks 122;
and S27, repeating the step S26 to reproduce the whole disk data hologram.
It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the technical solutions of the present invention, and are not intended to limit the specific embodiments of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the claims of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. An independently calibrated holographic storage optical path system comprises a signal optical path, a reference optical path, a reproduction optical path, a servo optical path and a storage medium; the signal light path and the reference light path respectively generate signal light and reference light, the signal light and the reference light respectively irradiate the storage medium at a certain angle, and the interference exposure is carried out to generate a hologram; the reproduction light path is used for converting the reproduction signal light diffracted by the reference light into a data page image and collecting the data page image; the storage medium comprises a recording layer and an address layer, wherein the recording layer is used for storing the hologram, and the address layer consists of a plurality of light paths; it is characterized in that the preparation method is characterized in that,
a plurality of calibration holographic bit marks and data holographic bit marks are arranged on the light path; the calibration holographic bit mark is used for positioning and recording the calibrated hologram; the data holographic bit mark is used for positioning a hologram for recording data;
the signal light path and the reference light path both comprise relay lens groups, and the relay lens groups are used for adjusting the irradiation angles and positions of the signal light and the reference light;
the servo light path is independent of the signal light path and the reference light path and is used for identifying the calibration holographic bit mark and the data holographic bit mark;
the servo optical path includes a servo laser for generating servo light, a collimating lens for adjusting an irradiation position of the servo light on the storage medium, and a photodetector for receiving and analyzing the servo light reflected from the address layer of the storage medium.
2. The system of claim 1, wherein the servo light is incident perpendicularly to the storage medium, and the signal light and the reference light are incident obliquely to the storage medium at the same or different angles, respectively.
3. An independently calibrated holographic storage optical path system according to claim 1, wherein the servo optical path further comprises a first half wave plate, a quarter wave plate, a first polarizing beam splitter, and an astigmatic focusing lens group; the first half-wave plate is used for converting the servo light into P-polarization servo light; the quarter-wave plate is used for converting the incident P polarization servo light into circular polarization servo light and converting the circular polarization servo light reflected by the storage medium into S polarization servo light; the first polarization beam splitter is used for reflecting the S-polarization servo light; the astigmatic focusing lens group is used for converging the S-polarized servo light.
4. The independently calibrated holographic storage optical path system of claim 1, wherein the signal optical path and the reference optical path each comprise a common read-write laser for generating read-write light and a common beam expander for expanding the read-write light and outputting a uniform beam.
5. The independently calibrated holographic storage optical path system of claim 1, wherein the signal optical path and the reference optical path comprise nyquist filters located at spectral planes of the signal light, the nyquist filters being configured to intercept unwanted spatial frequency components of the signal light to control hologram size.
6. An independently calibrated holographic storage optical path system according to claim 4, wherein said signal optical path comprises a second polarizing beam splitter for splitting said read-write light into said signal light and said reference light, and a spatial light modulator for loading said data page image into signal light.
7. An independently calibrated holographic storage optical path system according to claim 5, wherein said signal optical path and said reference optical path comprise a third polarizing beam splitter, said relay lens group and said nyquist filter being shared by the signal optical path and the reference optical path; the signal light and the reference light are split by a third polarization beam splitter and are irradiated to the storage medium at the same or different angles, respectively.
8. An independently collimating holographic storage optical path system according to claim 1, wherein said relay lens group comprises a fixed first fourier lens and a movable second fourier lens, and the illumination positions and angles of said signal light and said reference light are adjusted by moving the second fourier lens.
9. An independently calibrated holographic storage beam path system according to claim 1, wherein said reconstruction beam path comprises a fourth fourier lens for imaging and an image sensor for collecting data page images and analyzing diffraction efficiency and signal to noise ratio.
10. The system of claim 2, wherein the signal light and the reference light are incident at an angle of 90 °.
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| CN202211184389.0A CN115631774A (en) | 2022-09-27 | 2022-09-27 | Independently calibrated holographic storage optical path system |
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| CN202211184389.0A CN115631774A (en) | 2022-09-27 | 2022-09-27 | Independently calibrated holographic storage optical path system |
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