WO2017042900A1

WO2017042900A1 - Optical information recording device, optical information recording/reproducing device, and optical information recording method

Info

Publication number: WO2017042900A1
Application number: PCT/JP2015/075527
Authority: WO
Inventors: 啓太山口; 充永沢; 誠保坂
Original assignee: 株式会社日立製作所
Priority date: 2015-09-09
Filing date: 2015-09-09
Publication date: 2017-03-16

Abstract

Provided is an optical information recording technique in which change in phase difference between signal light and reference light during recording is corrected during recording to record a high quality hologram, and thereby phase multivalued information can be stably reproduced. This optical information recording device records, as a hologram in a hologram recording medium, an interference fringe obtained by causing interference of reference light and signal light, and is provided with: a light source that emits light; a light flux splitting element that splits the light emitted from the light source into first light and second light; a light detecting unit that receives the first light and the second light and detects an interference intensity; a phase control unit that calculates the phase difference between the first light and the second light from the interference intensity detected by the light receiving unit, and controls at least the phase of the second light; and a spatial light modulator that adds phase multivalued information to the second light.

Description

Optical information recording apparatus, optical information recording / reproducing apparatus, and optical information recording method

The present invention relates to an optical information recording apparatus, an optical information recording / reproducing apparatus, and an optical information recording method using holography.

As a background art in this technical field, for example, there is JP 2008-203503 (Patent Document 1). In this publication, there is a description as “provides a technique for matching the phase of the diffracted light obtained from the hologram recording medium and the second reference light”. As a solution, “the first reference light is applied to the hologram recording medium 30”. The first reference beam path that guides the laser beam from the laser 11 to irradiate the laser beam, and the diffracted beam that guides the diffracted beam generated from the hologram recording medium 30 by the irradiation of the first reference beam to the CMOS sensor 27 having a plurality of pixels. An optical path, and a second reference light optical path that guides the second reference light having the same polarization direction as the polarization direction of the diffracted light from the laser 11 to the CMOS sensor 27, so that a phase is provided in the optical path of the second reference light. The delay element 16 and the biaxial rotating mirror 18 are arranged so that the phase of the diffracted light and the second reference light are matched to obtain a favorable DC reproduction characteristic. "

JP2008-203503

As next-generation storage technology, hologram recording / reproducing technology that records and reproduces information two-dimensionally modulated using holography is attracting attention. At the time of hologram recording, two-dimensional information is added to the signal light, and interference fringes formed by superimposing with the reference light are recorded in the recording medium. At the time of hologram reproduction, the diffracted light reproduced by irradiating the interference fringes of the recording medium with reference light is detected by the image sensor, and two-dimensional information is reproduced.

In order to increase the recording capacity in the hologram recording / reproducing technology, a phase multilevel technology for adding multilevel phase information to light has been proposed as a technology for adding two-dimensional information to light. In the present technology, light having high coherence (oscillator light) is superimposed on the diffracted light reproduced from the hologram and caused to interfere, thereby converting phase information into intensity information and reproducing two-dimensional information. In Patent Document 1, the phase of the oscillator light is controlled by a phase modulation element, and the phase difference between the diffracted light and the oscillator light can be matched.

However, since the technique of Patent Document 1 does not consider the phase difference change between the signal light and the reference light at the time of recording, there is a problem that the deterioration of the reproduction performance due to the phase difference change at the time of recording cannot be sufficiently suppressed. .

Therefore, the present invention provides an optical information recording technique capable of stably reproducing phase multilevel information by correcting a phase difference change between signal light and reference light during recording and recording a high-quality hologram. The purpose is to do.

The above problem is solved by the following configuration, for example.

In an optical information recording apparatus that causes reference light and signal light to interfere with each other and records the obtained interference fringes as a hologram on a hologram recording medium, a light source that emits light, light emitted from the light source, first light and second light A light beam splitting element that splits the first light and the second light to detect interference intensity, and the first light based on the interference intensity detected by the light receiving section. A phase controller that calculates a phase difference of the second light and controls at least a phase of the second light; and a spatial light modulator that adds phase multilevel information to the second light.

Advantageous Effects of Invention According to the present invention, an optical information recording / reproducing apparatus and recording that can reproduce stable phase multilevel information by correcting a phase difference change between signal light and reference light during recording and recording a high-quality hologram. A playback method can be provided.

The figure showing the optical pick-up apparatus in the optical information recording and reproducing apparatus in Example 1 The figure showing the optical information recording and reproducing apparatus in Example 1 Signal point arrangement diagram showing phase four-value recording method in embodiment 1 The figure showing the optical pick-up apparatus in the optical information recording and reproducing apparatus in Example 1 Signal point arrangement diagram showing phase four-value reproduction method in embodiment 1 Histogram of interference intensity at the time of quaternary phase reproduction in embodiment 1 Signal point arrangement diagram showing a phase four-value recording / reproducing method when the phase difference is shifted due to disturbance in the first embodiment Histogram of interference intensity at the time of phase quaternary reproduction when the phase difference is shifted due to disturbance in the first embodiment The figure showing the relationship between the light which injects into the photodetector in Example 1, and a light-receiving part Relationship between interference intensity and phase difference between first detection light and second detection light in Embodiment 1 1 is a configuration diagram of a circuit that performs phase difference control between signal light and reference light during recording in Embodiment 1. FIG. Example 4 recording flow of phase 4 values by two recordings Page / book recording flow in the first embodiment Diagram of optical pickup device in optical information recording / reproducing device in embodiment 2 Diagram of optical pickup device in optical information recording / reproducing device in embodiment 3 Configuration diagram of polarization direction conversion element in Example 4 The figure showing the production | generation method of the 1st detection light from the signal light and reference light in Example 4, and a 2nd detection light The figure showing the relationship between the light which injects into the photodetector in Example 4, and a light-receiving part The figure showing the optical pick-up apparatus in the optical information recording and reproducing apparatus in Example 5 Configuration diagram of split phase plate in embodiment 6 The figure showing the relationship between the light which injects into the photodetector in Example 6, and a light-receiving part The figure showing the relationship between the light which injects into the photodetector in Example 7, and a light-receiving part Diagram of optical pickup device in optical information recording / reproducing apparatus in embodiment 8 The figure showing the relationship between the light which injects into the photodetector in Example 9, and a light-receiving part

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a block diagram showing a recording / reproducing apparatus for an optical information recording medium for recording and / or reproducing digital information using holography.

The optical information recording / reproducing device 10 is connected to an external control device 91 via an input / output control circuit 90. In the case of recording, the optical information recording / reproducing apparatus 10 receives the information signal to be recorded from the external control device 91 by the input / output control circuit 90. When reproducing, the optical information recording / reproducing apparatus 10 transmits the reproduced information signal to the external control apparatus 91 by the input / output control circuit 90.

The optical information recording / reproducing apparatus 10 includes a pickup 11, a cure optical system 13, a disk rotation angle detection optical system 14, and a rotation motor 50, and the optical information recording medium 1 can be rotated by the rotation motor 50. ing.

The pickup 11 plays a role of irradiating the optical information recording medium 1 with reference light and signal light to record digital information on the recording medium using holography and reproducing information recorded on the optical information recording medium 1. When recording on the optical information recording medium 1, the information signal to be recorded is sent to the spatial light modulator in the pickup 11 by the controller 89 via the signal generation circuit 86, and the signal light is modulated by the spatial light modulator.

Also, the controller 89 drives the phase modulation element in the pickup 11 via the phase control circuit 92 to control the phase of the signal light and the reference light.

When reproducing the information recorded on the optical information recording medium 1, the pickup 11 causes the reference light to enter the optical information recording medium in the opposite direction to that during recording. Reproduced light reproduced by the reference light is detected by a later-described photodetector in the pickup 11, and a signal is reproduced by the signal processing circuit 85.

The irradiation time of the reference light and the signal light applied to the optical information recording medium 1 can be adjusted by controlling the opening / closing time of the shutter in the pickup 11 via the shutter control circuit 87 by the controller 89.

The cure optical system 13 plays a role of generating a light beam used for pre-cure and post-cure of the optical information recording medium 1. Precure is a pre-process for irradiating a predetermined light beam in advance before irradiating the desired position with reference light and signal light when recording information at a desired position in the optical information recording medium 1. Post-cure is a post-process for irradiating a predetermined light beam after recording information at a desired position in the optical information recording medium 1 so that additional recording cannot be performed at the desired position.

The disk rotation angle detection optical system 14 is used to detect the rotation angle of the optical information recording medium 1. When adjusting the optical information recording medium 1 to a predetermined rotation angle, a signal corresponding to the rotation angle is detected by the disk rotation angle detection optical system 14, and a disk rotation motor control circuit is detected by the controller 89 using the detected signal. The rotation angle of the optical information recording medium 1 can be controlled via 88.

A predetermined light source driving current is supplied from the light source driving circuit 82 to the light sources in the pickup 11, the cure optical system 13, and the disk rotation angle detection optical system 14, and each light source emits a light beam with a predetermined light amount. Can do.

Further, the pickup 11 and the disc cure optical system 13 are provided with a mechanism capable of sliding the position in the radial direction of the optical information recording medium 1, and the position is controlled via the access control circuit 81.

By the way, the recording technology using the principle of angle multiplexing of holography tends to have a very small tolerance for the deviation of the reference beam angle.

Therefore, a mechanism for detecting the deviation amount of the reference beam angle is provided in the pickup 11, a servo control signal is generated by the servo signal generation circuit 83, and the deviation amount is corrected via the servo control circuit 84. It is necessary to provide a servo mechanism for this purpose in the optical information recording / reproducing apparatus 10.

Further, the pickup 11, the cure optical system 13, and the disk rotation angle detection optical system 14 may be simplified by combining several optical system configurations or all optical system configurations into one.

FIG. 1 shows a recording principle in an example of a basic optical system configuration of the optical pickup device 11 in the optical information recording / reproducing apparatus of the present embodiment. The light beam emitted from the light source 301 passes through the collimator lens 302 and enters the shutter 303. When the shutter 303 is open, after the light beam passes through the shutter 303, the optical ratio of the p-polarized light and the s-polarized light becomes a desired ratio by the optical element 304 composed of, for example, a half-wave plate. After the polarization direction is controlled, the light enters the polarization beam splitter 305.

The light beam that has passed through the polarization beam splitter 305 functions as signal light 306, and after the light beam diameter is expanded by the beam expander 308, the non-polarization beam splitter 326, the phase modulation element 309, the non-polarization beam splitter 332, the polarization direction It passes through the conversion element 310 and the polarization beam splitter 311 and enters the spatial light modulator 312, and becomes two-dimensional data (hereinafter, page data) to which phase information is added for each pixel by the spatial light modulator 312. Here, the phase distribution in the page data is, for example, a phase distribution that removes DC intensity (so-called hot spot) in the light intensity distribution on the Fourier plane of the optical information recording medium 1.

The signal light 306 to which page data is added by the spatial light modulator 312 is reflected by the polarization beam splitter 311 and propagates through the relay lens 313 and the spatial filter 314. Thereafter, the light is condensed on the optical information recording medium 1 by the objective lens 315.

The light beam reflected from the polarization beam splitter 305 functions as reference light 307, and is set to a predetermined polarization direction according to recording or reproduction by the polarization direction conversion element 316, and then passes through the mirror 317 to the galvanometer mirror 319. Incident. Since the angle of the galvanometer mirror 319 can be adjusted by the actuator 320, the incident angle of the reference light incident on the optical information recording medium 1 after passing through the lens 321 and the lens 322 can be set to a desired angle. In order to set the incident angle of the reference light, an element that converts the wavefront of the reference light may be used instead of the galvanometer mirror.

Thus, the signal 306 and the reference light 307 are incident on the optical information recording medium 1 so as to overlap each other, whereby an interference fringe pattern is formed in the recording medium, and information is written by writing this pattern on the recording medium. Record.

Further, by changing the incident angle of the reference light incident on the optical information recording medium 1 by the galvanometer mirror 319, a plurality of page data can be recorded in the same area, and the recording capacity can be increased by angle multiplexing.

Hereinafter, in holograms recorded in the same area with different reference beam angles, holograms corresponding to each reference beam angle are called pages, and a set of pages angle-multiplexed in the same area is called a book. .

Here, the signal multipoint recording method in the present embodiment, which is a method of recording four phases by recording twice at the same position and the same reference light angle of the optical information recording medium 1, is shown in FIG. This will be described with reference to a layout diagram. FIG. 3 shows a complex plane. The absolute value of a point on the complex plane represents the amplitude of the signal light 306, and the declination represents the phase difference between the signal light 306 and the reference light 307. In the following description, the phase of the signal light is a value based on the phase of the reference light.

FIG. 3A is a signal point arrangement diagram showing an example of binary information added by the spatial light modulator 312 by points on a complex plane. As shown in the signal point arrangement diagram, the spatial light modulator 312 adds binary information of a phase 0 signal point 401 and a phase π signal point 402. After the binary information of the phase 0 signal point 401 and the phase π signal point 402 shown in FIG. 3A is recorded, the phase modulation element 309 changes the phase of the signal light 306 by π / 2. The binary information of the signal point 403 of phase π / 2 and the signal point 404 of phase 3π / 2 shown in 3 (b) is recorded in the same location of the optical information recording medium 1. Depending on the combination of phases added in the two recordings, the signal point 405 of phase π / 4, the signal point 406 of phase 3π / 4, and the phase of 5π / 4 shown in the signal point arrangement diagram of FIG. A signal point 407 and a signal point 408 having a phase of 7π / 4 are recorded. By thus recording twice at the same angle, page data of quaternary information can be recorded.

FIG. 4 shows a reproduction principle in an example of a basic optical system configuration of the optical pickup device 11 in the optical information recording / reproducing apparatus of the present embodiment. When reproducing the recorded information, the reference light 307 enters the optical information recording medium 1. In this embodiment, a reproduction method using phase conjugate light is used, and the reference light 307 transmitted through the optical information recording medium 1 is reflected from the galvano mirror 324 whose angle can be adjusted by the actuator 323, and again, the optical information recording medium 1 The information is reproduced using the reference light 307 incident on the. The diffracted light 337 reproduced by the reference light 307 enters the photodetector 325 through the objective lens 315, the relay lens 313, the spatial filter 314, the polarization beam splitter 311, and the polarizer 339.

Further, in order to convert the phase multilevel information of the diffracted light 337 into intensity multilevel information and detect it by the photodetector 325, interference between the diffracted light 337 and light having high coherence (oscillator light 338) is used. In order to generate the oscillator light 338, the polarization direction is controlled by the polarization direction conversion element 304, and a desired amount of light is transmitted through the polarization beam splitter 305. The oscillator light 338 transmitted through the polarization beam splitter 305 passes through the beam expander 308, the non-polarization beam splitter 326, the phase modulation element 309, and the non-polarization beam splitter 332, and then the polarization direction is controlled by the polarization direction conversion element 310. Reflects the polarization beam splitter 311. Thereafter, the oscillator light 338 enters the photodetector 325 through the polarizer 339.

FIG. 5 is a diagram for explaining a method for reproducing phase information from interference between the diffracted light 337 and the oscillator light, which is a method for reproducing the signal point of the phase multilevel information of the diffracted light 337 in this embodiment. As shown in FIG. 5, and the diffracted light 337, the interference phase [Phi _LO oscillator light 338 and the phase of the reference light as a reference, the signal point 405, the signal points 406, signal point 407, the signal points 408, declination It can be regarded as a projection onto an axis 409 having Φ _LO . Therefore, in the interference light between the diffracted light 337 and the oscillator light 338, the intensity difference between the signal point 405 and the signal point 408 is proportional to the distance 410, and the intensity difference between the signal point 408 and the signal point 406 is proportional to the distance 411. The intensity difference between 406 and signal point 407 is proportional to distance 412.

FIG. 6 is a histogram obtained when the signal of FIG. 5 is reproduced. In FIG. 6, the horizontal axis indicates the light intensity detected by the photodetector 325, and the vertical axis indicates the number of pixels having each interference intensity in the page data. Here, a histogram is shown in a state where four signal points (405, 406, 407, 408) are arranged in the same number of page data. As shown in this histogram, when the phase Φ _LO is optimized, four signal points (405, 406, 407, 408) are arranged at equal intervals, and the interference intensity corresponding to each signal point can be separated. Reproduction performance is obtained.

The present embodiment is not limited to the method of separating the signal point 405, the signal point 406, the signal point 407, and the signal point 408 all at once, but four phases (arbitrary reference phase, reference phase + π / 2, reference phase). + Π, reference phase + 3π / 2) is added to the oscillator light 338 to detect the phase from the principle of fringe scanning generally used in interferometers, etc. The same effect can be obtained by using.

The photodetector 325 can be an image sensor such as a CMOS image sensor or a CCD image sensor, for example, but may be any element as long as page data can be reproduced.

By the way, when the signal point of FIG. 3C is added to the signal light 306, if the phase modulation accuracy of the phase modulation element 309 is low, the phase of the signal light 306 in the first recording and the signal light in the second recording. The difference from the phase of 306 is deviated from π / 2. In FIG. 7A, when the difference between the phase of the signal light 306 in the first recording and the phase of the signal light 306 in the second recording deviates from π / 2 by Φ, the signal point of the signal point to be recorded Indicates placement. As a result of the phase shift from Φ / 2 by Φ, the signal points recorded in the second recording are

signal points

505 and 506. As a result, the quaternary phase signal points recorded on the optical information recording medium 1 twice are arranged as signal points 501, 502, 503, and 504.

7 (b) shows a state in which these signal points, to play on interference with the oscillator beam having a phase [Phi _LO. Projection of the signal point 501, the signal point 502, the signal point 503, and the signal point 504 onto the axis 409 having the declination Φ _LO is as shown in FIG. 7B, and the distance 507 between the signal point 502 and the signal point 504 is shown in FIG. 6 is smaller than the distance 411 of 6. FIG. 8 shows an interference intensity histogram of the oscillator light added with the diffracted light 337 and the phase Φ _LO at this time. The difference in interference intensity between the signal point 502 and the signal point 504 decreases, and the reproduction performance of the phase information deteriorates.

Further, as shown in FIG. 7B, the amplitudes of the signal point 501 and the signal point 503 are increased, but the amplitudes of the signal point 502 and the signal point 504 are decreased. The amount of light in the portion where the point 504 is added decreases. For this reason, the reproduction performance equivalent to the case of FIGS. 5 and 6 cannot be obtained only by optimizing the phase Φ _LO of the oscillator light.

Here, in the optical information recording / reproducing apparatus 11 of the present embodiment described above, details of the method of controlling the phase modulation element during recording, which is a feature of the present embodiment, will be described with reference to FIGS. explain.

As shown in FIG. 1, a part of the signal light 306 is reflected by the non-polarizing beam splitter 326. The reflected light beam is referred to as first detection light 328. The first detection light 328 is reflected by the non-polarizing beam splitter 330 via the mirror 329 and then enters the photodetector 331.

On the other hand, a part of the signal light 306 transmitted through the non-polarizing beam splitter 326 reflects the non-polarizing beam splitter 332. The reflected light beam is referred to as second detection light 334. The second detection light 334 passes through the non-polarizing beam splitter 330 and then enters the photodetector 331.

FIG. 9 shows the relationship between the light receiving unit 801 of the photodetector 331 and the first detection light 328 and the second detection light 334 incident on the photodetector 331. A part of the first detection light 328 and the second detection light 334 overlap on the light receiving unit 801 and interfere with each other. The light receiving unit 301 detects the interference intensity between the first detection light 328 and the second detection light 334. The photodetector 331 may be an image sensor such as a CMOS image sensor or a CCD image sensor, or may be an element that detects light intensity, such as a photodetector.

Equation 1 is an expression representing the interference intensity I between the first detection light 328 and the second detection light 334.

Here, E ₁ represents the complex amplitude of the first detection light 328, E ₂ represents the complex amplitude of the second detection light 334, and ΔΦ represents the difference between the initial phase of the first detection light 328 and the initial phase of the second detection light 334. Interference the intensity I is next to the square of the absolute value of the sum of the complex amplitude _{E 2} of the complex amplitude _{E 1} and the second detection light 334 of the first detection light 328, the intensity of the first detection light 328 _| E 1 ^{| 2,} the second It can be expressed by the sum of the intensity | E ₂ | ^{2 of} the

detection light

334 and 2 | E ₁ || E ₂ | cosΔΦ of the interference light of the first detection light 328 and the second detection light 334.

FIG. 10 shows the relationship between the interference intensity I and the phase difference ΔΦ when | E ₁ | and | E ₂ | It can be seen that the interference intensity I detected by the photodetector 331 changes according to the change in the phase difference ΔΦ between the first detection light 328 and the second detection light 334.

When the phase modulation element 309 is driven before the first recording and the interference intensity detected by the photodetector 331 is maximized, the first detection light 328 and the second detection light 334 are changed as indicated by a point 901 in FIG. The phase difference becomes zero. After the first recording is completed, the phase modulation element 309 is driven so that the interference intensity detected by the photodetector 331 becomes half of the maximum value, and moves to a point 902 in FIG. By performing the second recording in this state, the second recording can be performed in a state where the phase difference between the first detection light 328 and the second detection light 334 is π / 2. Each time each page is recorded, an interference fringe pattern is formed on the optical information recording medium 1 by driving the phase modulation element 309 to move the point 901 in the first recording and the point 902 in the second recording. The phase of the signal light 306 can be changed by π / 2 between the first recording and the second recording.

Next, the control procedure of the phase modulation element 309 during recording will be described with reference to FIGS.

FIG. 11 shows a configuration of a phase control circuit 92 that controls the phase modulation element. The phase difference calculation circuit 101 calculates a phase difference from the interference intensity detected by the photodetector 331. The memory 102 temporarily records the phase difference calculated by the phase difference calculation circuit 101. The phase modulation element drive amount calculation circuit 103 calculates the drive amount of the phase modulation element 309 based on the phase difference calculated by the phase difference calculation circuit 101 and drives the phase modulation element 309.

FIG. 12 shows a four-phase recording flow by two-time recording in this embodiment. First, | E ₁ | and | E ₂ | of Equation ₁ are calculated in advance by the photodetector 331 (interference condition learning 1001). Next, the interference intensity is detected by the photodetector 331 (1002), the phase difference is calculated by the phase difference calculation circuit 101 based on the interference condition learned in 1001, and stored in the memory 102 as the phase difference 1 (1003). ). Thereafter, the interference fringe pattern of the signal light 306 and the reference light 307 is recorded on the optical information recording medium 1 (1004).

After the first recording is completed, the phase of the signal light 306 is π / 2 modulated by the phase modulation element 309 (1005). After that, the photodetector 331 detects the interference intensity between the first detection light 328 and the second detection light 334 (1006), and the phase difference calculation circuit 101 calculates the phase difference (1007). The phase difference calculated in 1007 is defined as phase difference 2. The phase difference 1 stored in the memory 102 in 1003 is compared with the phase difference 2 calculated in 1007, and it is determined whether the difference is within a predetermined range (1008).

If the difference between the phase difference 1 and the phase difference 2 is outside the predetermined range as a result of 1008, the phase modulation element drive amount calculation circuit 103 calculates the drive amount of the phase modulation element 309 (1009), and the processing from 1005 to 1008 is performed. Try again.

As a result of 1008, when the difference between the phase difference 1 and the phase difference 2 is within a predetermined range, the interference fringe pattern of the signal light 306 and the reference light 307 is recorded on the optical information recording medium 1 (1010), and the phase modulation element 309 The phase of the signal light 306 is returned to the phase at the time of the first recording (1011).

1012: Whether to record the next book or page is determined. When the recording is continued, the processing returns to the processing of 1001, and when the recording is ended, the processing is ended.

Note that phase difference detection and phase control in this embodiment are not performed every time one page data is recorded, and processing 1002 to processing 1003 and processing 1006 to processing 1009 are performed every several pages or every several books. Also good.

Further, the learning of the interference condition 1001 is not performed at the time of recording, but may be performed at the time of shipment adjustment or initial adjustment, for example. At this time, by controlling the control amount of the phase modulation element 309 when the phase difference is 0 and the control amount of the phase modulation element 309 when the phase difference is π / 2, the control of the phase modulation element 309 is recorded in advance. Set the initial value of the condition. Thereby, learning 1001 of the interference condition at the time of recording can be omitted, and the transfer speed at the time of recording can be increased.

As described above, based on the interference intensity detected by the photodetector 331, the phase difference between the first detection light 328 and the second detection light 334 at the time of the first recording in which the signal point 401 and the signal point 402 are recorded. By making it possible to calculate the phase difference between the first detection light 328 and the second detection light 334 during the second recording in which the signal points 403 and 404 are recorded, the first recording and the second recording can be performed. By recording the high-quality hologram by controlling the phase modulation element 309 with high precision so that the phase difference between the signal light and the reference light changes by π / 2, stable phase multilevel information can be reproduced. .

Note that the method for obtaining the phase difference between the first detection light 328 and the second detection light 334 from the interference intensity detected by the light detector 331 is not limited to the above means, and for example, the first detection light 328 and the second detection light 334. It may be calculated by adding four phases of 0, π / 2, π, 3π / 2, etc. to either of them and performing a fringe scan.

In this embodiment, the phase of the signal light is modulated using the phase modulation element 309 disposed in the optical path of the signal light 306, but the phase of the reference light 307 is disposed by arranging the phase modulation element in the optical path of the reference light 307. It is also possible to use a configuration that modulates.

In this embodiment, phase four-value recording and phase four-value reproduction by two-time recording have been described, but it goes without saying that this control method can be applied to any recording / reproduction method using phase multivalue. Yes.

For example, the phase difference between the signal light and the reference light during recording may be controlled to a predetermined value between pages or books. FIG. 13 shows an example of the recording flow at this time. After learning of interference conditions (1301), interference intensity detection (1302), and phase difference 1 calculation (1303), a page or book is recorded (1304), interference intensity detection (1305), and phase difference 2 calculation (1306) are performed. . It is determined whether the difference between the phase difference 1 and the phase difference 2 is within a predetermined range (1307). If the difference is outside the predetermined range, the phase modulation element driving amount is calculated (1308) and the phase modulation element is driven (1309). Return to 1305. If the difference between the phase difference 1 and the phase difference 2 is within a predetermined range in 1307, the page or book is recorded (1310). In step 1311, it is determined whether or not the next page or book is to be recorded. If so, the process returns to 1305.

By doing so, the phase difference of signal points between adjacent pages and adjacent books can be controlled to a predetermined value, and inter-page interference and inter-book interference can be suppressed. In addition, for example, the phase difference between the oscillator light and the reference light during reproduction may be controlled.

The present embodiment is different from the first embodiment in that the

non-polarizing beam splitters

326 and 332 that generate the first detection light 328 and the second detection light 334 are arranged near the optical information recording medium, and the reference light 307 A part of the light is used as the second detection light 334. With this configuration, it is possible to improve the recording quality by correcting changes in the optical path length of the signal light 306 and the reference light 307 due to disturbances such as air fluctuations, external vibrations, thermal expansion / contraction of the phase modulation element. become.

FIG. 14 shows a recording principle in an example of a basic optical system configuration of the optical pickup device 11 in the optical information recording / reproducing apparatus of the present embodiment. Part of the signal light 306 propagated through the relay lens 313 and the spatial filter 314 is reflected by the non-polarizing beam splitter 326. The reflected light beam is used as the first detection light 328. On the other hand, some of the reference light 307 reflected from the mirror 317 is transmitted through the non-polarizing beam splitter. The equalized light beam is used as the second detection light 334.

With the above configuration, in addition to the phase modulation error of the phase modulation element 309, the signal light path from the light source 301 to the non-polarization beam splitter 326 and the reference light path from the light source 301 to the non-polarization beam splitter 332 are generated. It becomes possible to observe and correct a phase difference change between the signal light 306 and the reference light 307 caused by a change in the optical path length due to disturbance such as air fluctuation, external vibration, thermal expansion / contraction.

In addition, the optical path length from the polarizing beam splitter 326 to the optical detector 331 is equal to the optical path length from the polarizing beam splitter 326 to the optical information recording medium 1, and the optical path length from the polarizing beam splitter 332 to the optical detector 331 is By making the optical path lengths from the polarizing beam splitter 332 to the optical information recording medium 1 equal, the influence of changes in the optical path length due to disturbance generated in the optical path from the polarizing beam splitter 326 and the polarizing beam splitter 332 to the optical information recording medium 1 is suppressed. can do.

This embodiment differs from

Embodiments

1 and 2 in that a polarizing beam splitter is used instead of the non-polarizing beam splitter. With the above configuration, it is possible to suppress the loss of light amount of the signal light 306 and the reference light 307 used for recording, and the time for recording optical information on the optical information recording medium 1 can be shortened.

FIG. 15 shows a recording principle in an example of a basic optical system configuration of the optical pickup device 11 in the optical information recording / reproducing apparatus of the present embodiment. In order to generate the first detection light 328 from the signal light 306, the polarization beam splitter 340 and the polarization direction conversion element 342 are used. By adjusting the polarization direction of the signal light 306 by the polarization direction conversion element 342, the light quantity ratio between the light transmitted through the polarization beam splitter 340 and the reflected light is adjusted.

On the other hand, in order to generate the second detection light 334 from the reference light 307, the polarization direction conversion element 316 and the polarization beam splitter 341 are used. By adjusting the polarization direction of the reference light 307 by the polarization direction conversion element 316, the light quantity ratio between the light transmitted through the polarization beam splitter 341 and the light reflected is adjusted.

As for reproduction, the reproduction method using phase conjugate light is used as in the first embodiment, and the information on the optical information recording medium 1 is reproduced using the reference light 307 reflected from the mirror 324.

The polarization direction conversion element 316 adjusts the polarization of the reference light 307 so that the reference light 307 passes through the polarization beam splitter 341. Further, the polarization direction conversion element 342 adjusts the polarization of the diffracted light 337 so that the diffracted light 337 reproduced from the optical information recording medium 1 passes through the polarization bee splitter 311.

With the above configuration, the light amounts of the first detection light 328 and the second detection light 334 can be arbitrarily changed. The first detection light 328 and the second detection light 334 having a minimum amount of light necessary for detecting the interference light by the light detector 331 are generated, and all the remaining light is used for recording optical information on the optical information recording medium 1. As a result, the light amount loss of the light used for recording can be suppressed and the recording time of the optical information on the optical information recording medium 1 can be shortened as compared with the first embodiment using the non-polarizing beam splitter.

Further, by adjusting the polarization direction conversion element 316 so that the reference beam 307 is completely transmitted through the polarization beam splitter 341 at the time of reproduction, the amount of diffracted light 337 reproduced from the optical information recording medium 1 increases. Can be shortened.

In the recording flow shown in FIG. 12, the first detection light 328 is obtained by the polarization direction conversion element 316 and the polarization direction conversion element 342 only in the first data recording process 1004 and the second data recording process 1010. By adjusting the light quantity of the second detection light 334 to substantially zero, the light quantity loss of the signal light 306 and the reference light 307 used for optical information recording can be eliminated.

The present embodiment is different from the second and third embodiments in that the configuration of the polarization direction conversion element 316 and the polarization direction conversion element 342 is changed so that only part of the signal light 306 and the reference light 307 is ejected and the first detection is performed. This is a point for generating light and second detection light. With the above configuration, the light amount loss of the signal light 306 and the reference light 307 used for recording can be eliminated from the first embodiment, and the recording time of optical information on the optical information recording medium 1 can be shortened. Further, with respect to the second and third embodiments, the phase difference between the first detection light 328 and the second detection light 334 can be controlled in real time.

A method for generating the first detection light and the second detection light in the present embodiment will be described with reference to FIGS.

FIG. 16 shows an example of the configuration of the polarization

direction conversion elements

316 and 342 in the present embodiment. Although the polarization direction of the light transmitted through the outer peripheral portion 1501 of the polarization direction conversion element does not change, the inner 1502 is made of, for example, a half-wave plate, and thus the polarization direction of the transmitted light changes.

FIG. 17A shows a configuration of a cross-sectional portion of the signal light 306 after being modulated by the spatial light modulator 312 in the present embodiment. The signal light 306 is made larger than the signal light 306A to which phase information is added by the spatial light modulator 312, and the signal light 306B to which a fixed phase is added is provided on the outer periphery of the signal light 306A.

FIG. 17B shows how the first detection light 328 is generated in the present embodiment. Of the signal light 306, the signal light 306 </ b> B is reflected by the polarization beam splitter 340 because it passes through the outer peripheral portion 1501 of the polarization direction conversion element 342. The signal light 306B reflected by the polarization beam splitter 340 is used as the first detection light 328. Of the signal light 306, the signal light 306 </ b> A passes through the inside 1502 of the polarization direction conversion element 342, and thus passes through the polarization beam splitter 340 and enters the optical information recording medium 1.

FIG. 17C shows how the second detection light is generated in the present embodiment. Similarly to the signal light 306, the reference light 307 is separated into a reference light 307A and a reference light 307B. Of the reference light 307, the reference light 307 B that is not used for optical information recording passes through the outer peripheral portion 1501 of the polarization direction conversion element 316 and is therefore reflected by the polarization beam splitter 341. The reference light 307B reflected by the polarizing beam splitter 341 is used as the second detection light 334. Of the reference light 307, the reference light 307 A used for optical information recording passes through the inside 1502 of the polarization direction conversion element 316, passes through the polarization beam splitter 341, and enters the optical information recording medium 1.

FIG. 18 shows an example of the relationship between the light receiving unit 801 of the photodetector 331 and the first detection light 328 and the second detection light 334 incident on the photodetector 331 in this embodiment. By adjusting the optical axes of the first detection light 328 and the second detection light 334 by a predetermined amount, the first detection light 328 and a part of the second detection light 334 are adjusted to overlap each other on the light receiving unit 801. The overlapping portion of the first detection light 328 and the second detection light 334 interferes, and the light receiving unit 801 detects the interference intensity.

In this way, only the part of the beam of the signal light 306 and the reference light 307 that does not contribute to the recording of the optical information on the optical information recording medium 1 is ejected to generate the first detection light 328 and the second detection light 334. Thus, loss of the light intensity of the signal light 306 and the reference light 307 used for recording optical information on the optical information recording medium 1 out of the beam of the signal light 306 and the reference light 307 can be eliminated, and the optical information recording medium The recording time of optical information to 1 can be shortened.

In addition, since the phase difference between the first detection light and the second detection light is controlled based on the interference intensity of the portion that does not contribute to the optical information recording, even when the phase information is added to the signal light 306 by the spatial light modulator 312. The phase difference between the first detection light 328 and the second detection light 334 can be calculated and controlled. Therefore, the phase difference between the first detection light 328 and the second detection light 334 can be controlled in real time during optical information recording.

Note that it goes without saying that the component configuration for ejecting the first detection light 328 and the second detection light 334 and the detection method by the detector 331 are not limited to those shown in FIGS.

The present embodiment is different from the first embodiment in that instead of generating the first detection light 328 and the second detection light 334 in front of the optical information recording medium 1 and detecting the interference caused by them by the photodetector 331, This is a point of detecting the interference between the signal light 306 transmitted through the optical information recording medium 1 and the reference light 307. With the above configuration, the light amount loss of the signal light 306 and the reference light 307 used for recording can be eliminated compared to the first embodiment, so that the recording time of optical information on the optical information recording medium 1 can be shortened. Moreover, since the phase difference change can be corrected with respect to the second and third embodiments, the accuracy of the phase difference control can be improved.

FIG. 19 shows a recording principle in an example of a basic optical configuration of the optical pickup device 11 in the optical information recording / reproducing apparatus of the present embodiment. In this embodiment, the photodetector 331 detects the interference intensity between the signal light 306 and the reference light 307 transmitted through the optical information recording medium 1 during recording.

The signal light 306 transmitted through the optical information recording medium 1 enters the photodetector 331 through the lens 340, the mirror 341, and the non-polarizing beam splitter 342.

The reference light 307 that has passed through the optical information recording medium 1 is reflected by the mirror 324, reflected by the non-polarized beam splitter 342, enters the photodetector 331, and overlaps with the signal light 306. Note that the angle of the mirror 324 can be adjusted by an actuator 323.

As an example of the reproducing optical configuration of the optical pickup device 11 in the optical information recording / reproducing apparatus of the present embodiment, the mirror 324 is adjusted by the actuator 323 so that the reference light 307 enters the optical information recording medium 1. Similar to the first embodiment, a reproduction method using phase conjugate light is used, and information on the optical information recording medium 1 is reproduced using the reference light 307 reflected from the mirror 324.

With the above configuration, in this embodiment, it is possible to eliminate the loss of the light amounts of the signal light 306 and the reference light 307 that are generated by generating the first detection light 328 and the second detection light 324 in Embodiment 1. The recording time of optical information on the optical information recording medium 1 can be shortened. Further, in this embodiment, the phase difference change in the signal light optical path after the lens 315 and the reference light optical path after the mirror 319 that cannot be corrected in the first embodiment can be corrected, and the accuracy of the phase difference control between the signal light 306 and the reference light 307 can be corrected. It leads to improvement.

The present embodiment is different from the first embodiment in that the optical path of the first detection light 328 or the second detection light 334 is divided into at least two spatially divided phase plates 1701 that add at least two kinds of phases to transmitted light. It is a point to be placed inside. With the above configuration, ΔΦ can be calculated without obtaining the values of | E ₁ | and | E ₂ | of Equation 1, so that learning of the interference condition required in the first embodiment can be omitted. The phase difference control can be speeded up.

An example of a method for detecting interference between the first detection light 328 and the second detection light 334 in the present embodiment will be described with reference to FIGS.

FIG. 20 shows an example of the divided phase plate 1701 in the present embodiment. A divided phase plate 1701 that is spatially divided into four and adds four types of phases (0, π / 2, π, 3π / 2) is disposed in the optical path of the first detection light 328. The first detection light 328 transmitted through the divided phase plate 1701 is divided into four regions to which different phases are added.

FIG. 21 shows an example of the relationship between the light receiving unit of the photodetector 331 and the first detection light 328 and the second detection light 334 incident on the photodetector 331 in this embodiment. The photodetector 331 includes four light receiving

units

801, 802, 803, and 804, and the light receiving unit 801 receives interference between the region 1801 to which the phase 0 is added and the second detection light 334 in the first detection light 328. The unit 802 includes interference between the second detection light 334 and the region 1802 to which the phase π / 2 is added in the first detection light 328, and the light receiving unit 803 includes the region 1803 to which the phase π is added from the first detection light 328. The light receiving unit 804 detects interference between the second detection light 334 and the interference between the second detection light 334 and the region 1804 added with the phase 3π / 2 in the first detection light 328.

The value obtained by subtracting the interference intensity detected by the light receiving unit 802 from the interference intensity detected by the light receiving unit 801 is I ₁ , and the value obtained by subtracting the interference intensity detected by the light receiving unit 804 from the interference intensity detected by the light receiving unit 803 is I ₂ . To do. Number 2 is a formula representing the first detection light 328 a phase difference ΔΦ of the second detection light 334 at I ₁ and I _2, can be calculated ΔΦ in accordance with the formula from I ₁ and I _2.

Based on this calculation result, the phase modulation element 309 is controlled so that the difference in ΔΦ between the first recording and the second recording becomes π / 2, thereby correcting the phase difference change between the signal light and the reference light. be able to.

With the above configuration, ΔΦ can be calculated without obtaining the values of | E ₁ | and | E ₂ | of Equation 1, so that learning of the interference condition required in the first embodiment can be omitted. The phase difference control can be speeded up.

In the present embodiment, the configuration using the spatially divided phase plate 1701 is described. However, the number of spatial divisions of the divided phase plate 1701 may be two or more. The number of light receiving units may be two or more. Further, the divided phase plate 1701 may be arranged in the optical path of the second detection light 334 so that a phase is added to the second detection light 334.

The present embodiment is different from the first embodiment in that the photodetector 331 is an imaging device such as a CMOS image sensor or a CCD image sensor, and the entire interference light of the first detection light 328 and the second detection light 334 is imaged. The point is that phase control is performed using a three-dimensional array type phase modulation element 309. With the above configuration, the in-plane distribution of the phase difference between the first detection light 328 and the second detection light 334 can be calculated, and the phase difference can be controlled for each arbitrary location in the plane.

FIG. 22 shows an example of the relationship between the light receiving unit 801 of the photodetector 331 and the first detection light 328 and the second detection light 334 incident on the photodetector 331 in this embodiment. In this embodiment, the photodetector 331 is an imaging device such as a CMOS image sensor or a CCD image sensor, and images the entire interference light of the first detection light 328 and the second detection light 334.

As shown in FIG. 22, the interference light is divided into a plurality of regions, and phase differences ΔΦ ₁ to ΔΦ _N between the first detection light 328 and the second detection light 334 are calculated in each region (N is the interference light) Division number).

Based on the calculated phase differences ΔΦ ₁ to ΔΦ _N , a phase difference control amount in each divided region of the interference light is calculated, and the phase modulation element 309 controls each of the phase differences ΔΦ ₁ to ΔΦ _N to a predetermined value. Here, the phase modulation element 309 is, for example, a two-dimensional array type element such as a phase modulation type spatial light modulator or a deformable mirror, so that an arbitrary position in the plane of the signal light 306 or the reference light 307 can be obtained. Enable to add phase.

With the above configuration, the in-plane distribution of the phase difference between the first detection light 328 and the second detection light 334 can be calculated, and the phase difference can be controlled for each arbitrary location in the plane. The in-plane wavefront deviation of the signal light 306 and the reference light 307 can be corrected.

The photodetector 331 may be configured to detect a phase difference distribution in the plane of the first detection light 328 and the second detection light 334 by arranging a plurality of elements such as a photodetector for detecting the light intensity in the plane.

This embodiment is different from the first embodiment in that light obtained by adding phase information to the signal light 306 by the spatial light modulator 306 is incident on the photodetector 331. With the above configuration, the phase information added by the spatial light modulator 312 to the signal light 306 can be measured during recording, and the recording quality can be further improved with respect to the first embodiment.

FIG. 23 shows a recording principle in an example of a basic optical system configuration of the optical pickup device 11 in the optical information recording / reproducing apparatus of the present embodiment. A part of the signal light 306 transmitted through the polarization direction changing element 310 is reflected by the non-polarizing beam splitter 326 and used as the first detection light 328. The first detection light 328 is reflected by the non-polarizing beam splitter 330 and enters the photodetector 331. On the other hand, the signal light 306 that has passed through the non-polarizing beam splitter 326 passes through the polarizing beam splitter 311, enters the spatial light modulator 312, and page data is added by the spatial light modulator 312. The signal light 306 to which page data is added by the spatial light modulator 312 is reflected by the polarization beam splitter 311, and part of the light is reflected by the non-polarization beam splitter 332. The light reflected by the non-polarization beam splitter 332 is used as the second detection light 334, and the second detection light 334 passes through the non-polarization beam splitter 330 and enters the photodetector 331.

Further, the photodetector 331 is an imaging device such as a CMOS image sensor or a CCD image sensor.

With the above configuration, each pixel of the spatial light modulator 312 adds the phase added to the signal light 306 from the interference intensity of the first detection light 328 and the second detection light 334 detected by the photodetector 331. It becomes possible to measure at the time of recording. The measurement result is compared with the information signal sent from the controller 89 to the spatial light modulator 312 via the signal generation circuit 86, and the spatial light is adjusted so that the difference between the measurement result for each pixel and the information signal is equal to or less than a predetermined value. The modulator 312 may be controlled, or variation information between the measurement result and the information signal is recorded on the optical information recording medium 1, and signal processing is performed based on the variation information between the measurement result and the information signal during reproduction. You can go.

Of course, the spatial light modulator 312 of the present embodiment is not limited to the one that adds a phase binary value, and may be one that adds, for example, phase quaternary or more phase multilevel information.

The present embodiment is different from the second embodiment in that the photodetector 331 includes a plurality of light receiving surfaces 801, and the optical axes of the first detection light 328 and the second detection light 334 incident on the light receiving unit 801 are different. Are inclined at a predetermined angle.

FIG. 24A is a diagram showing an example of the relationship between the photodetector 331, the first detection light 328, and the second detection light in the optical information recording / reproducing apparatus of the present embodiment. As shown in FIG. 24A, the first detection light 328 reflected by the non-polarizing beam splitter 330 enters the photodetector 331 perpendicularly. On the other hand, the second detection light 334 transmitted through the non-polarizing beam splitter 330 is incident obliquely on the photodetector 331.

FIG. 24B is a diagram showing an example of the relationship between the light receiving unit 801 of the photodetector 331, the first detection light 328, and the second detection light in the optical information recording / reproducing apparatus of the present embodiment. The wavefront of the first detection light and the wavefront of the second detection light are received by the light receiving unit 801 of the photodetector 331 in a state where the wavefronts of the first detection light and the second detection light are inclined at a predetermined angle, and interference fringes between the first detection light 328 and the second detection light 334 are received. Formed on the portion 801. The light receiving unit 801 includes a plurality of light receiving units. The light receiving unit receives the bright portions of the interference fringes of the first detection light 328 and the second detection light 334, and includes the first detection light 328 and the second detection light 334. There is a light receiving portion that receives a dark portion of an interference fringe.

With the above configuration, the contrast of the interference fringes between the first detection light and the second detection light can be measured by the photodetector 331, and the first phase modulation element 309 can adjust the contrast to maximize the contrast. By controlling the optical path length difference between the first detection light 328 and the second detection light 334, it is possible to record a hologram on the optical information recording medium 1 with high coherence between the signal light 306 and the reference light 307. Become. Therefore, a strong interference fringe pattern is recorded on the optical information recording medium 1, and the amount of diffracted light 337 during reproduction can be increased, so that high reproduction performance can be obtained.

Needless to say, the configuration of the light receiving surface 801 of the photodetector 331 of the present embodiment is not limited to the above. Further, the light incident on the photodetector 331 obliquely is not limited to the second detection light 334, and the first detection light 328 may be incident obliquely on the photodetector 331.

Further, the present embodiment is not limited to phase multilevel hologram recording. For example, even in amplitude multilevel hologram recording, it is possible to obtain high reproduction performance by increasing the coherence between the signal light 306 and the reference light 307. is there.

According to the above configuration, in the phase multilevel hologram recording / reproducing apparatus and the phase multilevel hologram recording / reproducing method, it is possible to correct the phase difference change between the signal light and the reference light during recording, and stable phase multilevel Information can be reproduced.

In addition, this invention is not limited to the above-mentioned Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.

The following configuration is an example of a modification. As Modification 1, a phase control unit that controls the phase of reference light or signal light, light that has passed through the phase control unit, and a light detection unit that detects interference intensity of light that has not passed through the phase control unit, A phase difference calculation unit that calculates a phase difference based on the interference intensity detected by the light detection unit; and a phase difference control amount calculation unit that calculates a phase difference control amount based on the phase difference, In an optical information recording / reproducing method using an optical information recording / reproducing apparatus for interfering reference light and the signal light, recording the obtained interference fringes as a hologram on a hologram recording medium, and reproducing the recorded hologram recording medium, An optical information recording / reproducing method, wherein the phase control unit controls the phase difference during optical information recording based on the phase difference control amount.

As a second modification, in the optical information recording / reproducing method described in the first modification, phase multi-value recording is performed by performing hologram recording twice on the same portion of the hologram recording medium, and the above-mentioned level is recorded during the first hologram recording. Control the phase difference during the second hologram recording so that the difference between the first phase difference control step for controlling the phase difference and the phase difference controlled in the first phase control step is within a predetermined range. An optical information recording / reproducing method comprising: a second phase difference control step.

As a third modification, the optical information recording / reproducing method according to the first modification includes the phase difference control step of controlling the phase difference every time a predetermined number of pages or a predetermined number of books are recorded. An optical information recording / reproducing method.

Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 1 ... Optical information recording medium, 11 ... Optical pick-up apparatus, 101 ... Phase difference calculation circuit, 102 ... Memory, 103 ... Phase modulation element drive amount calculation circuit, 301 ... Light source, 302 ... Collimating lens, 303 ... Shutter, 304 ... Half-wave plate, 305 ... Polarizing beam splitter, 306 ... Signal light, 307 ... Reference light, 308 ... Beam Expander, 309 ... phase modulation element, 310 ... polarization direction conversion element, 311 ... polarization beam splitter, 312 ... spatial light modulator, 313 ... relay lens, 314 ... spatial filter 315 ... objective lens, 316 ... polarization direction conversion element, 317 ... mirror, 319 ... mirror, 320 ... actuator, 321 ... lens, 322 ... , 323 ... Actuator, 324 ... Mirror, 325 ... Photodetector, 326 ... Unpolarized beam splitter, 328 ... First detection light, 329 ... Mirror, 330 ... Non-polarizing beam splitter, 331 ... photodetector, 332 ... non-polarizing beam splitter, 334 ... second detection light, 337 ... diffracted light, 338 ... oscillator light, 339 ... polarized light 340: Polarization beam splitter, 341: Polarization beam splitter, 342: Polarization direction conversion element, 801: Light receiving unit, 802 ... Light receiving unit, 803 ... Light receiving unit, 804 ..Light receiving part, 1701 ... Divided phase plate

Claims

In an optical information recording apparatus for interfering reference light and signal light, and recording the obtained interference fringes on a hologram recording medium as a hologram,
A light source that emits light;
A light beam splitting element that splits light emitted from the light source into first light and second light;
A light detection unit that receives the first light and the second light and detects interference intensity;
A phase control unit that calculates a phase difference between the first light and the second light from the interference intensity detected by the light detection unit, and controls at least the phase of the second light;
A spatial light modulator for adding phase multilevel information to the second light;
An optical information recording apparatus comprising:
The optical information recording apparatus according to claim 1,
The optical information recording apparatus, wherein the first light is reference light and the second light is signal light.
The optical information recording apparatus according to claim 2,
The light detection unit receives the reference light and signal light to which phase multilevel information is added by the spatial light modulator.
An optical information recording apparatus.
The optical information recording apparatus according to claim 2,
A second light beam splitting element that separates the signal light into a first signal light and a second signal light;
A third light beam splitting element that separates the reference light into a first reference light and a second reference light,
Causing the first signal light and the first reference light to interfere, and recording the obtained interference fringes as a hologram on a hologram recording medium;
The second signal light and the second reference light are incident on the light detection unit;
An optical information recording apparatus.
The optical information recording apparatus according to claim 4,
The optical path length of the first signal light and the optical path length of the second signal light substantially match, and the optical path length of the first reference light and the optical path length of the second reference light substantially match. An optical information recording apparatus.
The optical information recording apparatus according to claim 4,
A first polarization conversion element for converting the polarization of the signal light;
A second polarization conversion element that converts the polarization of the reference light,
The second light beam splitting element and the third light beam splitting element are polarization beam splitters, and signal light whose polarization has been converted by the first polarization conversion element is incident on the second light beam splitting element, An optical information recording apparatus, wherein the third light beam splitting element receives reference light whose polarization has been converted by the second polarization conversion element.
The optical information recording apparatus according to claim 2,
The optical information recording apparatus, wherein the spatial light modulator adds phase multilevel information to a partial region in a light beam plane of the signal light incident on the spatial light modulator.
The optical information recording apparatus according to claim 6,
The spatial light modulator adds phase information to a partial area in the light beam plane of the signal light incident on the spatial light modulator,
The optical information recording apparatus, wherein the first signal light is signal light to which the phase multilevel information is added.
The optical information recording apparatus according to claim 1,
The optical information recording apparatus, wherein the signal light and the reference light transmitted through the hologram recording medium are incident on the light detection unit.
The optical information recording apparatus according to claim 1,
A phase addition unit for adding two or more types of phases to the first light or the second light;
The optical information recording apparatus, wherein the light detection unit includes two or more light receiving units.
The optical information recording apparatus according to claim 1,
The light detection unit has a plurality of light receiving units,
The phase control unit calculates an in-plane distribution of the phase difference between the first light and the second light based on the interference intensity detected for each of a plurality of previous light receiving units, and the first light Alternatively, the phase is controlled for each arbitrary region in the light beam plane of the second light.
The optical information recording apparatus according to claim 1,
At least one of the first light and the second light is incident on the light detection unit at a predetermined angle,
An optical information recording apparatus.
The optical information recording apparatus according to claim 12,
At least one of the plurality of light receiving portions receives a bright portion of an interference fringe between the first light and the second light,
At least one of the plurality of light receiving parts receives a dark part of an interference fringe of the first light and the second light,
The phase control unit controls the phase of the first light or the second light so as to maximize an intensity difference between the bright part and the dark part;
An optical information recording apparatus.
The optical information recording apparatus according to claim 1, wherein phase multilevel recording is performed by a plurality of recordings.
An optical information recording apparatus for performing phase multilevel recording by irradiating the same portion of the hologram recording medium with a plurality of light beams each having a different phase added by the phase controller.
In an optical information recording / reproducing apparatus for interfering reference light and signal light, recording the obtained interference fringes as a hologram on a hologram recording medium, and reproducing the recorded hologram recording medium,
A light source that emits light;
A light beam splitting element that splits light emitted from the light source into first light and second light;
A light detection unit that receives the first light and the second light and detects interference intensity;
A phase control unit that calculates a phase difference between the first light and the second light from the interference intensity detected by the light receiving unit, and controls at least the phase of the second light;
A spatial light modulator for adding phase multilevel information to the second light;
An optical information recording / reproducing apparatus comprising:
The optical information recording / reproducing apparatus according to claim 15,
The optical information recording / reproducing apparatus, wherein the first light is the reference light and the second light is the signal light.
In the optical information recording method of interfering the reference light and the signal light, and recording the obtained interference fringes on the hologram recording medium as a hologram,
A light emitting step for emitting light;
A light beam dividing step of dividing the light emitted in the light emitting step into a first light and a second light;
A light detection step of receiving the first light and the second light and detecting an interference intensity;
A phase control step of calculating a phase difference between the first light and the second light from the interference intensity detected by the light receiving unit, and controlling at least the phase of the second light;
A spatial light modulation step of adding phase multilevel information to the second light;
An optical information recording method comprising: