CN219143795U - Holographic storage optical path system with calibration function - Google Patents
Holographic storage optical path system with calibration function Download PDFInfo
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- CN219143795U CN219143795U CN202222571655.7U CN202222571655U CN219143795U CN 219143795 U CN219143795 U CN 219143795U CN 202222571655 U CN202222571655 U CN 202222571655U CN 219143795 U CN219143795 U CN 219143795U
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Abstract
The utility model relates to the field of holographic storage, and discloses a holographic storage optical path system with calibration. The system comprises a signal light path, a reference light path, a reproduction light path, a servo light path and a storage medium; the storage medium comprises a recording layer and an address layer, and a plurality of calibration holographic bit marks and data holographic bit marks are arranged on the address layer; the signal light path and the reference light path both comprise a relay lens group, and the relay lens group is used for adjusting the irradiation angles and positions of the signal light and the reference light; 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 and the data holographic bit mark; the servo light path includes 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 back from an address layer of the storage medium. The method and the device are 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 present utility model relates to the field of holographic storage, and more particularly to a holographic storage optical path system with calibration.
Background
Holographic optical storage utilizes the interference of optical waves to record data page information in a photosensitive medium in the form of holograms, and has the advantages of large storage capacity, high data transmission rate, short addressing time and the like compared with the traditional optical storage technology. In the holographic optical storage technology, a laser beam is divided into two beams of reference light and signal light, wherein the signal light carries data page information after being transmitted or reflected by a spatial light modulator, interferes with the reference light in a photosensitive material layer of a storage medium and is exposed to form a hologram, so that information recording is realized.
An address layer is arranged in the holographic storage medium, and annular or spiral grooves or ridge-shaped channels are distributed on the address layer; the annular groove or the convex ridge is detected by the servo optical sensing system to realize accurate positioning, so that quick and convenient data access and storage are realized. The servo light path is introduced into the holographic optical storage light path system, so that the storage and retrieval efficiency of data can be effectively improved.
When reading the hologram, it is necessary to irradiate the same reference light as at the time of recording to reproduce the hologram in the storage medium; when the grating fringes in the storage medium are slightly deformed due to external factors, the incidence angle and the irradiation position of the reproduced reference light are slightly changed, so that the wave vector of the reproduced reference light meets the Bragg matching condition of the hologram, and the signal light is effectively reproduced. In addition, in order to ensure that the complete reading of data can be realized when the holographic optical disk on which the data is recorded is read on the same holographic optical disk drive or other holographic optical disk drives, the servo light beam and the reference light beam must be calibrated. It is therefore necessary to build an efficient calibration system for calibrating the servo and reference beams so that the head can read the data in the hologram completely during high speed movements.
Disclosure of Invention
The present utility model is directed to overcoming at least one of the above-mentioned shortcomings of the prior art, and providing a holographic storage optical system with calibration for solving the problem of how to calibrate and optimize the relative positions of reference light and servo light when the holographic storage optical system is reproduced.
The technical scheme adopted by the utility model is that the holographic storage light path system with calibration 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 a storage medium at a certain angle, and a hologram is generated by interference exposure; 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 includes a recording layer for storing holograms and an address layer. The address layer is provided with a plurality of calibration holographic bit marks and data holographic bit marks; the calibration hologram bit marks are used for positioning and recording the calibrated hologram; the data hologram bit mark is used for positioning a hologram for recording data; the signal light path and the reference light path both comprise a relay lens group, and the relay lens group is used for adjusting the irradiation angles and positions of the signal light and the reference light; 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 and the data holographic bit mark; the servo light path includes a servo laser for generating servo light, a calibration 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 back from an address layer of the storage medium.
The scheme is that a relay lens group is arranged in a signal light path and a reference light path so that the irradiation angles and positions of the signal light and the reference light can be adjusted; the irradiation position of the servo light can be adjusted by providing a collimator lens in the servo light path. The calibrated hologram, i.e. the calibration hologram, is recorded at the recording layer position corresponding to the calibration holographic bit marks on the storage medium. The hologram of the data, i.e. the data hologram, is recorded at the recording layer position corresponding to the data hologram bit mark on the storage medium. The scheme is that before recording the data hologram, the recording of the calibration hologram is carried out at the calibration hologram bit mark of the storage medium. Before the data hologram is reproduced, the calibration hologram is firstly reproduced at the calibration hologram position mark, the diffraction efficiency and the signal to noise ratio of the calibration hologram are detected through the reproduction light path, the wavelength of the relay lens group and the wavelength of the reference light are synchronously adjusted, and when the diffraction efficiency and the signal to noise ratio of the calibration hologram reach the maximum value, the calibration of the optimal irradiation angle, the position and the wavelength of the reference light is completed. Before the data hologram is reproduced, the servo light reflected from the address layer of the storage medium is detected and analyzed by the photoelectric detector, and the calibration lens is synchronously adjusted to complete the calibration of the optimal position of the servo light. The scheme calibrates the position of the calibration lens, the position of the relay lens group and the irradiation position and angle of the reference beam in the holographic storage light path system to the optimal state, and then reproduces the data hologram.
The reconstruction light path of the present solution includes a fourth fourier lens for imaging and an image sensor for collecting the data page image and analyzing the diffraction efficiency and signal-to-noise ratio. In order to convert the frequency-domain light field of the data page reproduced by the reference light into spatial light field imaging, a fourth Fourier lens is arranged in front of the image sensor. The fourth fourier lens performs an inverse fourier transform on the frequency domain light field and projects the spatial 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 of the signal light and the reference light can be an acute angle or an obtuse angle, and when the incident angle of the signal light and the reference light is 90 degrees, the storage performance is optimal.
Preferably, the servo light 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-polarized servo light; the quarter wave plate is used for converting incident P-polarized servo light into circular polarized servo light and converting circular polarized servo light reflected by the storage medium into S-polarized servo light; the first polarization beam splitter is used for reflecting the S-polarized servo light; the astigmatic focal lens group is used for converging the S-polarized servo light. The servo light of this scheme is transmitted through first half wave plate and is converted into P polarization servo light, and P polarization servo light is transmitted through first polarization beam splitter and is converted into circular polarization servo light through quarter wave plate after, and circular polarization servo light shines the back return in the former way of the address layer of storage medium perpendicularly. The reflected circularly polarized servo light is converted into S polarized servo light through a quarter wave plate, and the S polarized servo light is reflected to an astigmatic focusing lens group through a first polarization beam splitter and finally captured by the photoelectric detector. According to the scheme, the reflected track locking error signal and the tangential push-pull signal of the servo light path are analyzed through the photoelectric detector, so that the irradiation position of the servo light can be detected.
The method comprises the steps of detecting a track locking error signal and a tangential push-pull signal through a photoelectric detector, detecting the position of a servo light converging light spot, and when the servo light converging light spot is positioned in the middle of a calibration holographic position mark or a data holographic position mark, both the track locking error signal and the tangential push-pull signal are positioned at zero values between positive and negative maximum values.
The track locking error signal is used for detecting the condition that a servo light spot deviates from a track, and when the servo light spot is positioned on the center line of the track, the track locking error signal is 0; when the servo light spot gradually deviates from the optical track, the track locking error signal gradually tends to a maximum value or a minimum value; when the servo light spot is completely deviated from the track, the tracking error signal becomes 0.
The tangential push-pull signal is used for detecting a calibrated holographic bit mark or a data holographic bit mark of a light channel, 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 deviated from 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 utilizing the spherical waves to carry out 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 light path and the reference light path both comprise a shared read-write laser and a shared beam expander, the read-write laser is used for generating read-write light, and the beam expander is used for carrying out beam expansion on the read-write light.
Preferably, the signal light path and the reference light path comprise nyquist filters for intercepting unwanted spatial frequency components to control hologram size.
According to the scheme, the beam expander is used for carrying out beam expansion on the read-write light so as to solve the problem that the read-write light emitted by the read-write laser is nonuniform; and selecting the light of the middle uniform part through the 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 irradiation positions and angles of the signal light and the reference light are adjusted by moving the second fourier lens. The signal light path and the reference light path comprise a first Fourier lens and a second Fourier lens, the position of the first Fourier lens is fixed, and the position of the second Fourier lens is movable. The signal light path and the reference light path of 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 light path includes a second polarizing beam splitter for dividing the read-write light into the signal light and the reference light, and a spatial light modulator for loading the data page image to the signal light.
Further, the signal optical path and the reference optical path include a third polarizing beam splitter, the signal optical path and the reference optical path sharing the relay lens group and the nyquist filter; the signal light and the reference light are split by a third polarization beam splitter and respectively irradiated to the storage medium at the same or different angles.
Compared with the prior art, the utility model has the beneficial effects that:
the holographic storage light path system is provided with a servo unit, addresses on a storage medium are addressed and positioned through the servo unit, and holograms are stored in designated positions 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 the servo light spot are adjusted by the calibration lens in the servo unit, so that the servo light can be used for relocking the holographic bit mark, thereby ensuring that the reference light can reproduce data page information with high signal-to-noise ratio when the servo light is positioned on the holographic bit mark on the whole storage medium. In the scheme, even under the condition that the storage medium contracts and expands, the data in the storage medium can be accurately read out; and meanwhile, the compatibility of data stored in the read hologram among different devices is enhanced.
Drawings
FIG. 1 is a schematic diagram of a holographic storage optical system according to an embodiment of the present utility model.
Fig. 2 is a schematic view showing irradiation of signal light, reference light, and servo light on a storage medium according to the present utility model.
FIG. 3 is a schematic diagram of a holographic storage optical system according to another embodiment of the present utility model.
Description of the reference numerals: servo light 1, reference light 2, signal light 3; a recording layer 120, an address layer 121, a data hologram bit mark 122, a calibration hologram bit mark 123;
a servo laser 10, a first half-wave plate 20, a first polarizing beam splitter 30, a quarter-wave plate 40, an astigmatic focusing lens group 50, a photodetector 60, a collimating lens 140;
the read-write laser 70, the beam expander 80, the second half-wave plate 21, the third half-wave plate 22, the fourth half-wave plate 23, the second polarizing beam splitter 31, the third polarizing beam splitter 32, the spatial light modulator 90, the first fourier lens 130, the second fourier lens 131, the third fourier lens 160, the reference light objective lens 170, the fourth fourier lens 180, the image sensor 190, the nyquist filter 200.
Detailed Description
The drawings are for illustrative purposes only and are not to be construed as limiting the utility model. For better illustration of the following embodiments, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the actual product dimensions; it will be appreciated 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 technical scheme adopted by the utility model is that a holographic storage optical path system with calibration 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 3 and reference light 2, the signal light 3 and the reference light 2 respectively irradiate a storage medium at a certain angle, and a hologram is generated by interference exposure; the reproduction light 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 and an address layer 121, the recording layer 120 for storing holograms. The address layer 121 is provided with a plurality of calibration holographic bit marks 123 and data holographic bit marks 122; the calibration hologram bit mark 123 is used for positioning and recording a calibrated hologram; the data hologram bit mark 122 is used to locate a hologram in which data is recorded; the signal light path and the reference light path both comprise a relay lens group, and the relay lens group is used for adjusting the irradiation angles and positions of the signal light 3 and the reference light 2; 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 123 and the data holographic bit mark 122; the servo light path comprises a servo laser 10 for generating servo light 1, a collimator lens 140 for adjusting the irradiation position of the servo light 1 on the storage medium, and a photodetector 60 for receiving and analyzing the servo light 1 reflected back from the address layer 121 of the storage medium.
The scheme is that a relay lens group is arranged in a signal light path and a reference light path so that the irradiation angles and positions of the signal light 3 and the reference light 2 can be adjusted; the irradiation position of the servo light 1 can be adjusted by providing the collimator lens 140 in the servo optical path. The calibrated hologram, i.e. the calibration hologram, is recorded at the location of the recording layer 120 corresponding to the calibration holographic bit marks 123 on the storage medium. A hologram of data, i.e., a data hologram, is recorded at a location of the recording layer 120 corresponding to the data hologram bit mark 122 on the storage medium. The present scheme performs the recording of the calibration hologram at the calibration hologram bit marks 123 of the storage medium prior to the recording of the data hologram. Before the data hologram is reproduced, the calibration hologram is firstly reproduced at the calibration hologram position mark 123, the diffraction efficiency and the signal-to-noise ratio of the calibration hologram are detected through the 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 the maximum value, the calibration of the optimal irradiation angle, the position and the wavelength of the reference light 2 is completed. In the scheme, before the data hologram is reproduced, the photodetector 60 detects and analyzes the servo light 1 reflected from the address layer 121 of the storage medium, and the calibration lens 140 is synchronously adjusted to complete the calibration of the optimal position of the servo light 1. The present embodiment optimally aligns the position of the alignment lens 140, the position of the relay lens group, and the irradiation position and angle of the reference beam 2 in the holographic storage optical path system, and then reproduces the data hologram.
The reconstruction light path of the present solution includes a fourth fourier lens 180 for imaging and an image sensor 190 for collecting the data page images and analyzing diffraction efficiency and signal-to-noise ratio. In order to convert the frequency domain light field of the data page reproduced by reference light 2 into spatial 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 the 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 may 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 °, 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 focusing lens group 50; the first half-wave plate 20 is used for converting the servo light 1 into P polarized servo light; the quarter wave plate 40 is used for converting the incident P-polarized servo light into circular polarized servo light, and converting the circular polarized servo light reflected by the storage medium into S-polarized servo light; the first polarization beam splitter 30 is used for reflecting the S-polarized servo light; the astigmatic focal lens assembly 50 is used to collect S-polarized servo light. The servo light 1 in this embodiment is converted into P-polarized servo light through the first half-wave plate 20, and 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 is directly irradiated to the address layer 121 of the storage medium and returns in the original path. The reflected circularly polarized servo light is converted into S polarized servo light by the quarter wave plate 40, and the S polarized servo light is reflected by the first polarizing beam splitter 30 to the astigmatic focusing lens group 50, and finally captured by the photodetector 60. The irradiation position of the servo light 1 can be detected by analyzing the track-locked error signal and the tangential push-pull signal of the reflected servo light path by the photodetector 60.
The tracking error signal and the tangential push-pull signal are detected by the photodetector 60, and the position of the converging light spot of the servo light 1 is detected, and when the converging light spot of the servo light 1 is located in the middle of the calibration hologram position mark 123 or the data hologram position mark 122, the tracking error signal and the tangential push-pull signal are both located at zero values between positive and negative maxima.
The track locking error signal is used for detecting the condition that a servo light spot deviates from a track, and when the servo light spot is positioned on the center line of the track, the track locking error signal is 0; when the servo light spot gradually deviates from the optical track, the track locking error signal gradually tends to a maximum value or a minimum value; when the servo light spot is completely deviated from the track, the tracking error signal becomes 0.
The tangential push-pull signal is used for detecting a calibrated holographic bit mark 123 or a data holographic bit mark 122, i.e. a holographic bit mark, of a track, wherein 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 deviated from the notch, the tangential push-pull signal becomes 0.
The signal light 3 and the reference light 2 are spherical waves, and the holograms are recorded by utilizing the spherical waves to carry out 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 light path and the reference light path each include a common read-write laser 70 and a common beam expander 80, where the read-write laser 70 is used to generate read-write light, and the beam expander 80 is used to beam-expand the read-write light.
Preferably, the signal light path and the reference light path comprise a nyquist filter 200 located on the spectral plane of the signal light 3, the nyquist filter 200 being configured to intercept unwanted spatial frequency components on the spectral plane of the signal light 3 to control the hologram size.
The beam expander 80 is used for carrying out beam expansion on the read-write light, so as to solve the problem that the read-write light emitted by the read-write laser 70 is nonuniform.
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 light path includes a second polarization beam splitter 31 and a spatial light modulator 90, the second polarization beam splitter 31 being configured to split the read-write light into the signal light 3 and the reference light 2, and the spatial light modulator 90 being configured to load the data page image to the signal light 3.
Further, the signal optical path and the reference optical path include a third polarizing beam splitter 32, which shares the relay lens group and the nyquist filter 200; the signal light 3 and the reference light 2 are split by a third polarization beam splitter 32 and respectively irradiated to the storage medium at the same or different angles.
In this embodiment, the signal optical path and the reference optical path mostly 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 near the storage medium, and are further irradiated to the storage medium at the same or different angles. The specific optical path propagation paths are as follows:
the read-write laser 70 generates read-write light, and the read-write light is expanded by the beam expander 80 and then is adjusted to have a certain polarization direction by the second half-wave plate 21. The read-write light is converted into signal light 3 of P-polarization direction and reference light 2 of S-polarization direction after passing through the second polarization beam splitter 31. The reference light 2 and the signal light 3 are orthogonal in the offset direction, and the ratio is 1:1. The signal light 3 in the P polarization direction passes through the spatial light modulator 90 and carries data information. The signal light 3 in the P polarization direction and the reference light 2 in the S polarization direction pass through the first fourier lens 130, the nyquist filter 200, and the second fourier lens 131 in order, and then pass through 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 is transmitted 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 of the S polarization direction sequentially passes through the third polarization beam splitter 32 and the third fourier lens 160. The signal light 3 in the final 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.
In reproduction, the spatial light modulator 90 has no input signal, only the reference light 2 is irradiated on the hologram recorded with information in the storage medium, and the resulting diffracted light will continue to propagate in the propagation direction of the original signal light 3 after passing through the storage medium, and the data page image is collected and reproduced via the reproduction optical path.
In another embodiment, as shown in fig. 3, the signal optical path and the reference optical path have independent first fourier lens 130, second fourier lens 131, and nyquist filter 200, respectively. The second fourier lens 131 moving the signal light path can adjust the irradiation position and angle of the signal light 3. The second fourier lens 131 moving the reference light path can adjust the irradiation position and angle of the reference light 2.
The hologram for calibration and the recording method of the data hologram in the scheme specifically comprise the following steps:
s11, moving the calibration lens 140 and the second Fourier lens 131 to an initial position, so that a hologram generated by interference exposure of the reference light 2 and the signal light 3 is effectively positioned on the recording layer 120 of the storage medium under the condition that a converging light spot of the servo light 1 is focused on the address layer 121;
s12, fixing the calibration lens 140 and the second Fourier lens 131, and moving a storage medium to enable a servo light spot to be located at the calibration holographic position mark 123, and recording a calibration hologram at the calibration holographic position mark 123;
s13, moving the storage medium to enable a servo light spot to be located at the position of the other calibration holographic position mark 123, and recording the next calibration hologram at the position of the calibration holographic position mark 123;
s14, repeating the step S13 for a plurality of times to ensure that a plurality of calibration holograms are recorded successfully;
s15, moving the storage medium, enabling a 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 a servo light spot to be located at the other data holographic bit mark 122, and recording the next data hologram at the data holographic bit mark 122;
s17, repeating the step S16, and recording the hologram of the whole disc data;
the method for moving the calibration lens 140 and the second fourier lens 131 to the initial positions in step S11 is as follows: the optical path simulation design ensures that the converging light spot of the servo light 1 is on the plane of the optical path of the storage medium (namely the address layer 121), 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 calibration lens 140 and the second Fourier lens 131 at the moment 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 the storage medium, moving a converging light spot of the servo light 1 to the vicinity of the calibration holographic position mark 123, and fixing the positions of the calibration lens 140 and the storage medium;
s22, adjusting the wavelength of the reference light 2, fine-adjusting the positions of the second Fourier lens 131 and the storage medium, and fixing the position of the second Fourier lens 131 and the parameters of the reference light 2 when the diffraction efficiency and the signal-to-noise ratio of the calibration hologram at the calibration hologram position mark 123 reach the best;
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 position mark 123, and fixing the position of the calibration lens 140;
s24, moving the storage medium to enable a servo light spot to be located at the position of the next calibration holographic bit mark 123, and reconstructing a calibration hologram at the position of the calibration holographic bit mark 123;
s25, repeating the step S24 for a plurality of times, and ensuring that the reproduction signal-to-noise ratio of the plurality of calibration holograms reaches 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 a converging light spot of the servo light 1 to be positioned at the data hologram bit mark 122, and reconstructing a data hologram at the data hologram bit mark 122;
s27, repeating the step S26, and reproducing the hologram of the whole disc data.
It should be understood that the foregoing examples of the present utility model are provided for the purpose of clearly illustrating the technical aspects of the present utility model and are not intended to limit the specific embodiments of the present utility model. Any modification, equivalent replacement, improvement, etc. that comes within the spirit and principle of the claims of the present utility model should be included in the protection scope of the claims of the present utility model.
Claims (10)
1. A holographic storage optical system with calibration 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 and reference light, the signal light and the reference light respectively irradiate a storage medium at a certain angle, and a hologram is generated by interference exposure; 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 includes a recording layer for storing holograms and an address layer; it is characterized in that the method comprises the steps of,
the address layer is provided with a plurality of calibration holographic bit marks and data holographic bit marks; the calibration hologram bit marks are used for positioning and recording the calibrated hologram; the data hologram bit mark is used for positioning a hologram for recording data;
the signal light path and the reference light path both comprise a relay lens group, and the relay lens group is used for adjusting the irradiation angles and positions of the signal light and the reference light;
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 and the data holographic bit mark; the servo light path includes a servo laser for generating servo light, a calibration 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 back from an address layer of the storage medium.
2. The holographic storage optical path system of claim 1, in which said servo light is normally incident on said storage medium, and said signal light and said reference light are respectively obliquely incident on said storage medium at the same or different angles.
3. The holographic storage optical path system of claim 1, in which said 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-polarized servo light; the quarter wave plate is used for converting incident P-polarized servo light into circular polarized servo light and converting circular polarized servo light reflected by the storage medium into S-polarized servo light; the first polarization beam splitter is used for reflecting the S-polarized servo light; the astigmatic focal lens group is used for converging the S-polarized servo light.
4. The holographic storage optical system of claim 1, in which 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 holographic storage optical path system of claim 1, in which said signal optical path and said reference optical path comprise nyquist filters located on a spectral plane of said signal light, said nyquist filters being adapted to intercept unwanted spatial frequency components of the signal light to control hologram size.
6. The holographic storage optical path system of claim 4, in which 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. The holographic storage optical path system of claim 5, in which said signal optical path and said reference optical path comprise a third polarizing beam splitter, the signal optical path and reference optical path sharing said relay lens group and said nyquist filter; the signal light and the reference light are split by a third polarization beam splitter and respectively irradiated to the storage medium at the same or different angles.
8. The holographic storage optical path system of claim 1, in which the relay lens group comprises a fixed first fourier lens and a movable second fourier lens, the illumination positions and angles of the signal light and the reference light being adjusted by moving the second fourier lens.
9. The holographic storage optical path system of claim 1, in which the reconstruction optical 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 holographic storage optical path system of claim 2, in which said signal light and said reference light are incident at an angle of 90 °.
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