JPH10293520A - Optical information recorder and optical information reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an optical system for recording or reproducing small and to reduce intensity change in reproducing light with respect to thickness of an information recording layer recording information by using holography. SOLUTION: At a recording time, a hologram layer 3 of an optical information recording medium 1 is irradiated by recording reference light from one surface side through an objective lens 12, and the other side surface is irradiated by information light through a coupling lens 50, and a reflection type hologram is formed. At a reproducing time, the hologram layer 3 of the optical information recording medium 1 is irradiated by reproducing reference light from one surface side through the objective lens 12, and the information light generated from the hologram layer 3 is converged by the objective lens 12 to be detected by a CCD array 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical information recording apparatus for recording information on an optical information recording medium using holography and an optical information reproducing apparatus for reproducing information from the optical information recording medium using holography.

[0002]

2. Description of the Related Art In general, holographic recording in which information is recorded on a recording medium using holography is performed by superimposing light having image information and reference light inside a recording medium, and generating interference at that time. This is performed by writing stripes on a recording medium. When reproducing the recorded information, the recording medium is irradiated with reference light, whereby the image information is reproduced by diffraction due to interference fringes.

In recent years, volume holography, especially digital volume holography, has been developed in the practical range for ultra-high-density optical recording, and has attracted attention. Volume holography is a method of writing interference fringes three-dimensionally by actively utilizing the thickness direction of the recording medium. Increasing the thickness increases the diffraction efficiency, and using multiplex recording to increase the storage capacity. There is a feature that can be achieved. And
Digital volume holography is a computer-oriented holographic recording method that uses the same recording medium and recording method as volume holography, but limits image information to be recorded to binary digital patterns. In this digital volume holography, for example, image information such as an analog picture is once digitized, developed into two-dimensional digital pattern information, and recorded as image information. At the time of reproduction, this digital pattern information is read out and decoded to return to the original image information for display. Thereby, even if the SN ratio (signal-to-noise ratio) is somewhat poor at the time of reproduction, the original information can be reproduced very faithfully by performing differential detection or encoding the binary data to correct errors. It becomes possible.

FIG. 11 is a perspective view showing a schematic configuration of a recording / reproducing system in conventional digital volume holography. This recording / reproducing system includes a spatial light modulator 10 for generating an information light 102 based on two-dimensional digital pattern information.
1, a lens 103 for condensing the information light 102 from the spatial light modulator 101 and irradiating the hologram recording medium 100 with the information light 102. Reference light irradiating means (not shown) for irradiating light 104, CCD (charge coupled device) array 107 for detecting reproduced two-dimensional digital pattern information, and reproduction light 105 emitted from hologram recording medium 100 And a lens 106 for condensing the light and irradiating the light onto the CCD array 107. For the hologram recording medium 100, a crystal such as LiNbO ₃ is used.

In the recording / reproducing system shown in FIG. 11, at the time of recording, information such as an original image to be recorded is digitized, and the 0 or 1 signal is further arranged two-dimensionally to generate two-dimensional digital pattern information. . One piece of two-dimensional digital pattern information is called page data. Here, it is assumed that page data # 1 to #n are multiplex-recorded on the same hologram recording medium 100. In this case, first, the spatial light modulator 101 selects transmission or light blocking for each pixel based on the page data # 1, whereby the spatially modulated information light 1 is selected.
02 is generated and irradiated on the hologram recording medium 100 via the lens 103. At the same time, the hologram recording medium 10
0, the reference light 1 from a direction θ1 substantially orthogonal to the information light 102.
04, and inside the hologram recording medium 100,
The interference fringes formed by the superposition of the information beam 102 and the reference beam 104 are recorded. In order to increase the diffraction efficiency, the reference light 104 is transformed into a flat beam by a cylindrical lens or the like, and the interference fringes are changed to the hologram recording medium 100.
To be recorded in the thickness direction. At the time of recording the next page data # 2, the reference light 104 is irradiated from the angle θ2 different from θ1, and the reference light 104 and the information light 1 are irradiated.
02 can be multiplex-recorded on the same hologram recording medium 100. Similarly, at the time of recording other page data # 3 to #n, information is multiplex-recorded by irradiating the reference beam 104 from different angles θ3 to θn. A hologram in which information is multiplex-recorded is called a stack. In the example shown in FIG. 11, the hologram recording medium 100 has a plurality of stacks (stack 1, stack 2,..., Stack m,...).

To reproduce any page data from the stack, the stack may be irradiated with the reference beam 104 having the same incident angle as when the page data was recorded. Then, the reference light 104 is selectively diffracted by an interference fringe corresponding to the page data, and a reproduction light 105 is generated. This reproduction light 105 is transmitted through a lens 106
, And the two-dimensional pattern of the reproduction light is detected by the CCD array 107. Then, the information such as the original image is reproduced by decoding the detected two-dimensional pattern of the reproduction light in a manner reverse to that at the time of recording.

[0007]

In the configuration shown in FIG. 11, information can be multiplex-recorded on the same hologram recording medium 100. However, in order to record information at a very high density, the hologram recording medium 100 must be used. The positioning of the information light 102 and the reference light 104 becomes important. However, in the configuration shown in FIG.
0 has no information for positioning, the information beam 102 and the reference beam 10
The positioning of 4 can only be performed mechanically, and high-precision positioning is difficult. Therefore, the removability (easiness of transferring the hologram recording medium from one recording / reproducing apparatus to another recording / reproducing apparatus and performing the same recording / reproducing) is poor, and random access is difficult and high-density recording is difficult. There is a problem that is. Further, in the configuration shown in FIG. 11, since the optical axes of the information light 102, the reference light 104, and the reproduction light 105 are spatially arranged at mutually different positions, there is a problem that the optical system becomes large. .

Accordingly, the present applicant has proposed an optical information recording / reproducing apparatus and an optical information recording medium as shown in FIG. FIG. 12 shows only essential parts of the optical information recording / reproducing apparatus and the optical information recording medium. The optical information recording medium 201 shown in FIG. 12 has a hologram layer 203 on which information is recorded using volume holography, a reflective film 205, and a protective layer 20 on one surface of a disk-shaped transparent substrate 202.
4 are stacked in this order. An optical information recording / reproducing apparatus for recording / reproducing information using the optical information recording medium 201 includes a transparent substrate 2 of the optical information recording medium 201.
02; an actuator 213 that can move the objective lens 212 in the thickness direction and the radial direction of the optical information recording medium 201;
12, a two-divided optical rotation plate 214, which is disposed in this order from the objective lens 212 side on the opposite side of the optical information recording medium 201,
An S-polarization hologram 215 and a spatial light modulator 216 are provided.

The two-part optical rotation plate 214 has an optical rotation plate 214L arranged on the left side of the optical axis in FIG. 12, and an optical rotation plate 214R arranged on the right side of the optical axis in FIG. Each of the optical rotation plates 214L and 214R is configured by sealing liquid crystal between, for example, two transparent electrode substrates. The optical rotation plate 214L rotates the polarization direction by + 45 ° when no voltage is applied between the two transparent electrode substrates (hereinafter, it is referred to as being turned off with respect to the description of the two-segmented optical rotation plate 214 and the spatial light modulator 216), A voltage is applied between the two transparent electrode substrates (hereinafter, it is referred to as being turned on with respect to the description of the two-part optical rotation plate 214 and the spatial light modulator 216).
And the polarization direction is not rotated. On the other hand, the optical rotation plate 214R rotates the polarization direction by −45 ° when turned off, and does not rotate the polarization direction when turned on.

The S-polarized hologram 215 has a lens function of converging light only for S-polarized light (linearly polarized light whose polarization direction is perpendicular to the plane of incidence). Spatial light modulator 216
Has a large number of pixels arranged in a lattice, and by selecting the polarization direction of the emitted light for each pixel, it is possible to spatially modulate the light by the difference in the polarization direction. . Here, when turned off, the spatial light modulator 216 rotates the polarization direction by + 90 ° for each pixel, and does not rotate the polarization direction when turned on.

In the optical information recording / reproducing apparatus shown in FIG.
6, and is modulated by the spatial light modulator 216 to generate an S-polarized light beam and a P-polarized light beam (linearly polarized light whose polarization direction is parallel to the incident surface). The P-polarized light beam passes through the S-polarized hologram 215 as a parallel light beam, is condensed by the objective lens 212, is irradiated on the optical information recording medium 201, passes through the hologram layer 203 while converging, and is protected by the hologram layer 203. It converges so as to have the smallest diameter on the boundary surface with the layer 204. On the other hand, the s-polarized light flux is S
After being slightly converged by the polarization hologram 215, it is condensed by the objective lens 212 and
And converges so as to have the smallest diameter before the boundary surface between the hologram layer 203 and the protective layer 204, and then passes through the hologram layer 203 while diverging. In the light beam from the S-polarization hologram 215, the left side of the optical axis is rotated by + 45 ° in the polarization direction by the optical rotation plate 214L of the two-part optical rotation plate 214, and the right side of the optical axis is the optical rotation plate 214R of the two-part optical rotation plate 214. The polarization direction is -45
° rotated. As a result, in the hologram layer 203, in the region where the two light beams having different convergence positions overlap each other, the polarization directions of the two light beams match, and the hologram layer 2
A transmission type (Fresnel type) hologram is formed in 03. At the time of reproduction, reference light corresponding to one of the two light fluxes at the time of recording is applied to the optical information recording medium 201 to obtain reproduction light.

When a transmission type hologram is formed on a layered hologram recording medium such as the hologram layer 203 in the optical information recording medium 201 shown in FIG. 12, for example, the thickness of the hologram recording medium depends on the light wavelength. In the case where there is a variation in the degree, as shown in FIG. 13, the diffraction efficiency greatly changes, and as a result, the intensity of the reproduction light also largely changes, so that it is difficult to obtain a stable reproduction light. . FIG. 13 shows the relationship between the thickness of the hologram recording medium and the diffraction efficiency. In the drawing, reference numeral 221 denotes the diffraction efficiency when a transmission hologram is formed, and reference numeral 222 denotes a reflection type (Lipman type). 3) shows the diffraction efficiency when the hologram is formed. Also,
Reference numeral 223 indicates a thickness of about the wavelength of light.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to reduce the size of an optical system for recording or reproduction and to record information using holography. It is an object of the present invention to provide an optical information recording device and an optical information reproducing device capable of reducing a change in intensity of reproduction light with respect to a thickness of a layer.

[0014]

An optical information recording apparatus according to the present invention is an optical information recording apparatus for recording information on an optical information recording medium having an information recording layer on which information is recorded using holography. A recording reference light irradiating means for irradiating a recording reference light from one surface side to the information recording layer, and an information recording layer to the information recording layer from the other surface side. An information light irradiating means for irradiating information light carrying information to be recorded so that information is recorded by an interference pattern due to interference with the recording reference light.

The optical information reproducing apparatus of the present invention uses holography to record information by an interference pattern caused by interference between a recording reference light emitted from one surface and information light emitted from the other surface. An optical information reproducing device for reproducing information from an optical information recording medium having a recorded information recording layer, comprising: A reproducing reference light irradiating unit for irradiating the reference light, and a reproducing reference light is irradiated with reproducing light generated from the information recording layer by irradiating the reproducing reference light by the reproducing reference light irradiating unit. Reproduction light detecting means for collecting and detecting from the same surface side as the surface side.

In the optical information recording apparatus of the present invention, the information recording layer of the optical information recording medium is irradiated with the recording reference light from one side by the recording reference light irradiating means. , The information light is irradiated from the other surface side,
As a result, information is recorded on the information recording layer by an interference pattern due to interference between the recording reference light and the information light.

In the optical information reproducing apparatus of the present invention, the reproduction reference light corresponding to the recording reference light is applied to the information recording layer of the optical information recording medium from one surface side by the reproduction reference light irradiation means. The reproduction light emitted from the information recording layer by being irradiated with the reproduction reference light is collected and detected from the same surface as the surface irradiated with the reproduction reference light. .

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing a configuration of an optical information recording / reproducing apparatus as an optical information recording apparatus and an optical information reproducing apparatus according to a first embodiment of the present invention;
FIG. 2 is a block diagram showing the overall configuration of the optical information recording / reproducing apparatus according to the present embodiment.

First, the configuration of the optical information recording medium according to the present embodiment will be described with reference to FIG. The optical information recording medium 1 includes a hologram layer 3 as an information recording layer on which information is recorded using volume holography, and a semi-reflective film 5 on one surface of a disk-shaped transparent substrate 2 formed of polycarbonate or the like. And the transparent protective layer 4
They are stacked in this order. On the boundary surface between the hologram layer 3 and the protective layer 4, a plurality of address / servo areas as positioning regions extending linearly in the radial direction are provided at predetermined angular intervals, and a sector shape between adjacent address / servo areas is provided. The section is the data area. In the address servo area, information for performing focus servo and tracking servo by the sampled servo method and address information are recorded in advance by emboss pits or the like. Note that focus servo can be performed using a semi-reflective surface of the semi-reflective film 5. As information for performing the tracking servo, for example, a wobble pit can be used. The transparent substrate 2 has an appropriate thickness of, for example, 0.6 mm or less, and the hologram layer 3 has an appropriate thickness of, for example, 10 μm or more. The hologram layer 3
It is formed of a hologram material whose optical characteristics such as refractive index, dielectric constant, and reflectivity change according to the intensity of light when irradiated with light. Examples of the hologram material include a photopolymer (ph) manufactured by Dupont.
OTOPOLYMERS) HRF-600 (product name) or the like is used. In addition, in FIG. 1, the code | symbol 9 represents the radial direction.

The semi-transmissive film 5 is formed of a transparent material having a different refractive index from that of the hologram layer 3 so as to transmit a part of the amount of incident light and reflect the rest. By appropriately selecting the refractive index of the protective layer 4, the hologram layer 3 and the protective layer 4 can be provided without providing the semi-transmissive film 5.
May be a semi-reflective surface. In addition,
A reflective film may be provided instead of the semi-transmissive film 5 only in the servo area, and neither the semi-transmissive film 5 nor the reflective film may be provided in the data area.

Next, the configuration of the optical information recording / reproducing apparatus according to the present embodiment will be described. As shown in FIG. 2, the optical information recording / reproducing apparatus 10 includes a spindle 81 on which the optical information recording medium 1 is mounted, a spindle motor 82 for rotating the spindle 81, and a predetermined number of rotations of the optical information recording medium 1. And a spindle servo circuit 83 for controlling the spindle motor 82 so as to maintain the value of The optical information recording / reproducing device 10 further irradiates the optical information recording medium 1 with information light and recording reference light to record information, and irradiates the optical information recording medium 1 with reproduction reference light. A pickup 11 for detecting reproduction light and reproducing information recorded on the optical information recording medium 1; and a driving device 84 for moving the pickup 11 in the radial direction of the optical information recording medium 1. It has. Pickup 1
Reference numeral 1 denotes a pickup main body 11a disposed on one surface side of the optical information recording medium 1 for irradiating the recording reference light, irradiating the reproduction reference light, and detecting the reproduction light; It has an information light emitting portion 11b that is provided on the other surface side and irradiates information light, and a connecting portion 11c that connects the pickup main body 11a and the information light emitting portion 11b.

The optical information recording / reproducing apparatus 10 further receives a focus error signal FE,
A detection circuit 85 for detecting the tracking error signal TE and the reproduction signal RF, and an actuator in the pickup 11 is driven based on the focus error signal FE detected by the detection circuit 85 to move the objective lens to the optical information recording medium. A focus servo circuit 86 for performing focus servo by moving the focus servo circuit in the thickness direction 1;
A tracking servo circuit 87 that drives an actuator in the pickup 11 based on the tracking error signal TE detected by the step 5 to move the objective lens in the radial direction of the optical information recording medium 1 to perform tracking servo.
And a slide servo circuit 88 that controls the drive device 84 based on the tracking error signal TE and a command from a controller to be described later to perform a slide servo for moving the pickup 11 in the radial direction of the optical information recording medium 1. .

The optical information recording / reproducing apparatus 10 further decodes output data of a later-described CCD array in the pickup 11 to reproduce data recorded in the data area 7 of the optical information recording medium 1 or to detect the data in the detection circuit. A signal processing circuit 89 for reproducing a basic clock or determining an address from a reproduced signal RF from the optical disc 85;
And a controller 90 for controlling the whole of the device. The controller 90 receives the basic clock and address information output from the signal processing circuit 89, and controls the pickup 11, the spindle servo circuit 83, the slide servo circuit 88, and the like. The spindle servo circuit 83 receives the basic clock output from the signal processing circuit 89.

As shown in FIG. 1, the pickup 11
The objective lens 12 faces the surface of the optical information recording medium 1 on the side of the transparent substrate 2 when the optical information recording medium 1 is fixed to the spindle 81, and the objective lens 12 is attached to the optical information recording medium 1 in the thickness direction. And an actuator 13 movable in a radial direction, and a half mirror 14 and a CCD array 15 arranged in order from the objective lens 12 on the opposite side of the optical information recording medium 1 in the objective lens 12. The pickup 11 further includes a half mirror 14
, And a collimator lens 17 disposed between the laser coupler 20 and the half mirror 14. Pickup 11
Further, the collimator lens 17 in the half mirror 14
On the opposite side, a spatial light modulator 18 and a coupling lens 19 are sequentially provided from the half mirror 14 side. Each of these components is a pickup body 1
1a.

The pickup 11 further includes a spindle 8
When the optical information recording medium 1 is fixed to the optical information recording medium 1, the coupling lens 50 facing the surface of the optical information recording medium 1 on the side of the protective layer 4 and the light emitted from the coupling lens 19 are directed to the coupling lens 50 side. And an optical fiber 51 for transmission. The coupling lens 50 is provided in the information light emitting portion 11b, and the optical fiber 51 is provided in the connecting portion 11c.

The laser coupler 20 emits a laser beam,
The laser light is converted into a parallel light beam by the collimator lens 17 and is incident on the half mirror 14, where a part of the light amount is reflected and the rest is transmitted. The light reflected by the half mirror 14 is condensed by the objective lens 12, irradiates the optical information recording medium 1 from the transparent substrate 2 side, and has the smallest diameter on the interface between the hologram layer 3 and the protective layer 4. To converge. On the other hand, the light transmitted through the half mirror 14 is condensed by the coupling lens 19 via the spatial light modulator 18, enters one end of the optical fiber 51, is emitted from the other end of the optical fiber 51, and is coupled. The light is condensed by the lens 50, irradiates the optical information recording medium 1 from the protective layer 4 side, and converges to have the smallest diameter on the boundary surface between the hologram layer 3 and the transparent substrate 2.

The return light from the optical information recording medium 1 to the objective lens 12 side passes through the objective lens 12 and then enters the half mirror 14, where a part of the light amount is reflected and the rest is transmitted. It has become. The return light reflected by the half mirror 14 is condensed by the collimator lens 17 and enters the laser coupler 20. On the other hand, light transmitted through the half mirror 14 is incident on the CCD array 15.

The spatial light modulator 18 has a large number of pixels arranged in a lattice, and each pixel has a light transmitting state (hereinafter, also referred to as ON) and a light blocking state (hereinafter, also referred to as OFF). By selecting (1) and (2), light can be spatially modulated by intensity. Spatial light modulator 1
Specifically, for example, a liquid crystal display element utilizing the optical rotation of liquid crystal can be used as the element 8. In this case, the spatial light modulator 18 can selectively apply a voltage between the opposing electrodes for each pixel, and light passing through the pixel to which the voltage is applied is
Light that does not rotate the polarization direction and consequently passes unblocked by the analyzer and passes through a pixel to which no voltage is applied is rotated in the polarization direction and is consequently blocked by the analyzer. As the liquid crystal in the spatial light modulator 18, for example, a ferroelectric liquid crystal having a high response speed (on the order of microsecond) can be used. This enables high-speed recording, for example, information of one page can be recorded with several μ or less.

FIG. 3 is a perspective view showing the structure of the laser coupler 20 in FIG. 1, and FIG. 4 is a side view of the laser coupler 20. As shown in these figures, the laser coupler 20
Semiconductor substrate 2 on which photodetectors 25 and 26 are formed
1 and a prism 22 arranged on the semiconductor substrate 21 so as to cover the photodetectors 25 and 26 and bonded to the semiconductor substrate 21 at a position different from the position where the photodetectors 25 and 26 are formed on the semiconductor substrate 21. The semiconductor device includes a semiconductor element 23 arranged and bonded on a semiconductor substrate 21 and a semiconductor laser 24 bonded on the semiconductor element 23. The semiconductor laser 24 emits forward laser light in the horizontal direction toward the prism 22 and emits backward laser light in a direction opposite to the forward laser light. Semiconductor laser 2 of prism 22
On the side of the semiconductor laser 2, a slope is formed.
4 reflects part of the forward laser light from the semiconductor substrate 2
1 and a semi-reflective surface 22a that transmits a part of the return light from the optical information recording medium 1. The upper surface of the prism 22 is a total reflection surface 22b that totally reflects the light passing through the prism 22, as shown in FIG. In the semiconductor element 23, a photodetector 27 that receives a backward laser beam from the semiconductor laser 24 is formed. The output signal of the photodetector 27 is used to automatically adjust the output of the semiconductor laser 24. Various amplifiers and other electronic components are built in the semiconductor substrate 21. The semiconductor element 23 has built-in electronic components such as an amplifier for driving the semiconductor laser 24.

The laser coupler 20 shown in FIGS. 3 and 4
1, a part of the forward laser light from the semiconductor laser 24 is reflected by the semi-reflective surface 22a of the prism 22, and is incident on the collimator lens 17 in FIG. A part of the return light from the optical information recording medium 1 collected by the collimator lens 17 passes through the semi-reflective surface 22a of the prism 22, and is guided into the prism 22,
It is directed to the photodetector 25. A semi-reflective film is formed on the photodetector 25, and a part of the light guided into the prism 22 passes through the semi-reflective film on the photodetector 25 and is incident on the photodetector 25, and the other part is a photodetector. The light is reflected by the semi-reflective film on the surface 25, further reflected by the total reflection surface 22 b of the prism 22, and incident on the photodetector 26.

Here, as shown in FIG.
The light guided into the light source 2 is once converged so as to have the smallest diameter in the middle of the optical path between the photodetectors 25 and 26. In a focused state where the light from the laser coupler 20 converges on the boundary surface between the hologram layer 3 and the protective layer 4 on the optical information recording medium 1 so as to have the smallest diameter, the diameter of the light incident on the photodetectors 25 and 26 is When they are out of focus, the diameters of the light incident on the photodetectors 25 and 26 are different. Since the change in the diameter of the incident light on the photodetectors 25 and 26 is opposite to each other, a focus error signal can be obtained by detecting a signal corresponding to the change in the diameter of the incident light on the photodetectors 25 and 26. As shown in FIG. 3, the photodetectors 25,
Reference numeral 26 has a light receiving unit divided into three parts. A1, C1, and B light receiving sections in the photodetector 25
1. The light receiving units in the photodetector 26 are A2 and C
2, B2. C1 and C2 are A1 and B1 respectively.
And a light receiving portion at the center between A2 and B2. The dividing line between the light receiving sections is arranged so as to be parallel to the direction corresponding to the track direction in the optical information recording medium 1. Therefore, a tracking error signal can be obtained by the push-pull method from the difference between the outputs between the light receiving portions A1 and B1 and between the outputs between A2 and B2.

The control of the output of the semiconductor laser 24 in the laser coupler 20 and the control of the spatial light modulator 18 are performed by a drive circuit (not shown) under the control of the controller 90 in FIG. Has become.

FIG. 5 shows a detection circuit 85 for detecting a focus error signal, a tracking error signal and a reproduction signal based on the outputs of the photodetectors 25 and 26.
FIG. 3 is a block diagram showing the configuration of FIG. This detection circuit 85
An adder 31 for adding the respective outputs of the light receiving sections A1 and B1 of the photodetector 25, a gain adjusting amplifier 32 for adjusting the gain of the output of the adder 31, and a gain for adjusting the gain of the output of the light receiving section C1 of the photodetector 25. Adjustment amplifier 33
And a subtractor 34 for calculating the difference between the output of the gain adjustment amplifier 32 and the output of the gain adjustment amplifier 33;
And a gain adjustment amplifier 36 for adjusting the gain of the output of the adder 35, a gain adjustment amplifier 37 for adjusting the gain of the output of the light receiving section C2 of the photodetector 26, and an output of the gain adjustment amplifier 36 and the gain adjustment amplifier 37. A subtractor 38 for calculating a difference between the output and a subtractor 39 for calculating a difference between an output of the subtractor 34 and an output of the subtractor 38 to generate a focus error signal FE.

The detection circuit 85 further includes a subtractor 40 for calculating the difference between the output of the light receiving section A1 of the photodetector 25 and the output of the light receiving section B1, and the light receiving section A of the photodetector 26.
Subtractor 4 for calculating the difference between the output of the light receiving section B2 and the output of the light receiving section B2
1 and a subtractor 4 that calculates the difference between the output of the subtractor 40 and the output of the subtractor 41 to generate the tracking error signal TE.
2 is provided. The detection circuit 85 further includes the adder 31
An adder 43 for adding the output of the light receiving unit C1 to the output of
An adder 44 that adds the output of the adder 35 and the output of the light receiving unit C2, and an adder 45 that adds the output of the adder 43 and the output of the adder 44 to generate a reproduction signal RF. . In the present embodiment, the reproduction signal RF is a signal obtained by reproducing information recorded in an address servo area on the optical information recording medium 1.

Next, the operation of the optical information recording / reproducing apparatus and the optical information recording medium according to the present embodiment will be described with reference to FIGS.
The description will be made in the order of recording and reproduction. The optical information recording medium 1 is controlled by the spindle motor 82 so as to be maintained at a specified number of revolutions during servo, recording, and reproduction.

First, the operation at the time of servo will be described.
At the time of servo, all the pixels of the spatial light modulator 18 are turned off, and the output of the light emitted from the laser coupler 20 is set to a low output for reproduction. The controller 90 predicts the timing at which the light emitted from the objective lens 12 passes through the address servo area based on the basic clock reproduced from the reproduction signal RF, and outputs the light from the objective lens 12 over the address servo area. During the passage, the above settings are used.

The coherent laser light emitted from the laser coupler 20 is converted into a parallel light beam by the collimator lens 17, enters the half mirror 14, reflects a part of the light amount, and transmits the rest. Light transmitted through the half mirror 14 is blocked by the spatial light modulator 18. The light reflected by the half mirror 14 is condensed by the objective lens 12 and recorded on the optical information recording medium 1 such that the light converges on the boundary surface between the hologram layer 3 and the protective layer 4 so as to have the smallest diameter. The medium 1 is irradiated. This light is partially reflected by the semi-reflective film 5 of the information recording medium 1, and is modulated by emboss pits in the address servo area and returns to the objective lens 12 side. This return light is converted into a parallel light flux by the objective lens 12, enters the half mirror 14, a part of the light amount is reflected by the half mirror 14, is collected by the collimator lens 17, and enters the laser coupler 20,
It is detected by the photo detectors 25 and 26. Then, based on the outputs of the photodetectors 25 and 26, the detection circuit 85 shown in FIG. 5 generates a focus error signal FE, a tracking error signal TE, and a reproduction signal RF. While the tracking servo is performed, reproduction of the basic clock and determination of the address are performed.

Next, the operation at the time of recording will be described with reference to FIG. At the time of recording, the spatial light modulator 18 selects OFF or ON for each pixel according to information to be recorded.
The output of the light emitted from the laser coupler 20 is pulsed to a high output for recording. The controller 90 predicts the timing at which the light emitted from the objective lens 12 passes through the data area based on the basic clock reproduced from the reproduction signal RF. Make the above settings. While the light emitted from the objective lens 12 passes through the data area, focus servo and tracking servo are not performed, and the objective lens 12 is fixed.

The coherent laser light emitted from the laser coupler 20 is converted into a parallel light beam by the collimator lens 17, enters the half mirror 14, reflects a part of the light amount, and transmits the rest. The light reflected by the half mirror 14 is collected by the objective lens 12,
The information recording medium 1 is irradiated so as to converge so as to have the smallest diameter on the boundary surface between the hologram layer 3 and the protective layer 4.
In this embodiment, this light is used as recording reference light. On the other hand, the light transmitted through the half mirror 14 is transmitted to the spatial light modulator 1.
By 8, the intensity is spatially modulated in accordance with the information to be recorded, condensed by the coupling lens 19, and incident on one end of the optical fiber 51. This light is transmitted through an optical fiber 5
1, the light is transmitted to the information light emitting portion 11b side, is emitted from the other end of the optical fiber 51, and is coupled to the coupling lens 50.
And irradiates the information recording medium 1 so as to converge so as to have the smallest diameter on the boundary surface between the hologram layer 3 and the transparent substrate 2. In the present embodiment, this light is used as information light.

FIG. 6 is an explanatory diagram showing the states of the recording reference light and the information light in the hologram layer 3. As shown in this figure, in the hologram layer 3, the recording reference light 61
And the information light 62 travel in opposite directions and interfere with each other.
Then, when the output of the light emitted from the laser coupler 20 becomes high, the interference pattern between the recording reference light 61 and the information light 62 is volumetrically recorded in the hologram layer 3, and is of a reflection type (Lipman type). Is formed.

Next, the operation at the time of reproduction will be described with reference to FIG. FIG. 7 shows the pickup 11 during reproduction.
It is explanatory drawing which shows the state. At the time of recording, all the pixels of the spatial light modulator 18 are turned off, and the output of the light emitted from the laser coupler 20 is set to a low output for recording. The controller 90 predicts the timing at which the light emitted from the objective lens 12 passes through the data area based on the basic clock reproduced from the reproduction signal RF. Make the above settings. While the light emitted from the objective lens 12 passes through the data area, focus servo and tracking servo are not performed, and the objective lens 12 is fixed.

The coherent laser light emitted from the laser coupler 20 is converted into a parallel light flux by the collimator lens 17, enters the half mirror 14, reflects a part of the light amount, and transmits the rest. Light transmitted through the half mirror 14 is blocked by the spatial light modulator 18. The light reflected by the half mirror 14 is condensed by the objective lens 12 and applied to the information recording medium 1 so as to converge on the boundary surface between the hologram layer 3 and the protective layer 4 so as to have the smallest diameter. . In the present embodiment, this light is used as reproduction reference light. Then, by irradiating the reproduction reference light, reproduction light corresponding to the information light at the time of recording is generated from the hologram layer 3.

FIG. 8 is an explanatory view showing the state of the reference light for reproduction and the reproduction light in the hologram layer 3. As shown in this figure, in the hologram layer 3, the reference beam for reproduction 63
Travels as light similar to the recording reference light 61, and this recording reference light 61 is diffracted by a reflection type hologram to correspond to the information light 62 during recording from within the hologram layer 3. A reproduction light 64 is generated. The reproduction light 64 is transmitted through the transparent substrate 2 and passes through the objective lens 12.
Side, is condensed by the objective lens 12, enters the half mirror 14, and a part of the light amount is
4 and enter the CCD array 15.

As described above, the CCD array 15 includes:
The reproduction light 64 is incident, and on the CCD array 15, only the portion corresponding to the pixel that was turned on in the spatial light modulator 18 at the time of recording is illuminated brightly, and its two-dimensional pattern is
It is detected by the CD array 15. Then, the output signal of the CDD array 15 is output to the signal processing circuit 89 in FIG.
And the information is reproduced.

As described above, according to the optical information recording / reproducing apparatus 10 according to the present embodiment, irradiation of the recording reference light and the information light on the optical information recording medium 1 during recording, and optical information Since the irradiation of the recording reference light to the recording medium 1 and the detection of the reproduction light are all performed on the same axis, the optical system for recording and reproduction needs to be smaller than that of the conventional holographic recording method. Can be. Further, according to the optical information recording / reproducing device 10 according to the present embodiment, an optical system for recording and reproducing is
It can be configured in the form of a pickup 11, which is substantially the same as a normal optical disk device. Further, since it is not an optical system using polarized light, a polarization hologram or an optical rotation plate is not required, and the configuration is simple.

Further, according to the optical information recording / reproducing apparatus 10 according to the present embodiment, information for performing the focus servo and the tracking servo is recorded on the optical information recording medium 1, and the information is used for a normal optical disc. As with the device, focus servo and tracking servo can be performed, so that the positioning of light for recording or reproduction can be performed with high accuracy, and as a result, the servo can be stabilized and reliability can be improved. Can be improved, the removability is good, random access is easy, and the recording capacity and transfer rate can be increased.

Further, according to the optical information recording / reproducing apparatus 10 according to the present embodiment, since the reflection type hologram is formed on the optical information recording medium 1, the transmission type hologram is formed as shown in FIG. Compared to the case of the hologram, it is possible to increase the diffraction efficiency, and even if the thickness of the hologram layer 3 has a variation at about the wavelength of light, the diffraction efficiency does not change significantly. Can be improved in reliability.

Further, according to the optical information recording / reproducing apparatus 10 of the present embodiment, the spatial light modulator 18
Is used, it is possible to block the information light at the time of reproduction that does not require the information light.

Further, according to the optical information recording / reproducing apparatus 10 of the present embodiment, since the information light and the recording reference light are branched by using the half mirror 14, the transmission of the half mirror 14 By appropriately setting the reflectance and the reflectance, the light quantity ratio between the information light and the recording reference light in the hologram layer 3 can be made approximately 1: 1. Can be increased.

Next, an optical information recording / reproducing apparatus according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 9 shows a recording state of the optical information recording / reproducing apparatus according to the present embodiment, and FIG. 10 shows a reproducing state of the optical information recording / reproducing apparatus according to the present embodiment. The optical information recording / reproducing apparatus according to the present embodiment includes a pickup body 1
As means for transmitting information light from 1a to the information light emitting portion 11b, instead of the coupling lenses 19 and 50 and the optical fiber 51 in the optical information recording and reproducing apparatus according to the first embodiment, three mirrors 52 are used. , 53, 54
And a coupling lens 54. The mirror 52 bends the light from the spatial light modulator 18 upward in FIG. 9, the mirror 53 bends the light from the mirror 52 leftward in FIG.
The light from No. 3 is bent downward in FIG. The coupling lens 55 condenses the light from the mirror 54 and records the optical information from the surface on the side of the protective layer 4 so that the light converges on the boundary surface between the hologram layer 3 and the transparent substrate 2 so as to have the smallest diameter. The medium 1 is irradiated.

The mirrors 52 and 53 are provided in the connecting portion 11c, and the mirror 54 and the coupling lens 55
It is provided in the information light emitting section 11b.

In the optical information recording / reproducing apparatus according to the present embodiment, at the time of recording, the light modulated by the spatial light modulator 18 is replaced by mirrors 52 and 53 instead of the optical fiber 51 in the first embodiment. , 54 to the information light emitting portion 11b. Other configurations, operations, and effects of the present embodiment are the same as those of the first embodiment.

The present invention is not limited to the above embodiments. For example, in the above embodiments, the optical information recording medium 1
In the address servo area, address information and the like are recorded in advance by embossed pits. However, without providing embossed pits in advance, a portion of the hologram layer 3 close to the protective layer 4 is selected in the address servo area. Alternatively, formatting may be performed by irradiating a high-power laser beam and selectively changing the refractive index of the portion to record address information and the like.

The element for detecting the information recorded on the information recording layer 3 is not a CCD array, but a smart optical sensor (eg, a MOS solid-state image sensor and a signal processing circuit) integrated on one chip. Document "O plus
E, September 1996, No. 202, pages 93-99 ". ) May be used. Since this smart optical sensor has a high transfer rate and a high-speed calculation function, high-speed reproduction can be performed by using this smart optical sensor. For example, reproduction can be performed at a transfer rate on the order of G bits / sec. Becomes possible.

In particular, when a smart optical sensor is used as an element for detecting information recorded on the information recording layer 3, address information and the like are written in an address servo area of the optical information recording medium 1 by emboss pits. Instead of recording, in advance, a predetermined pattern of address information or the like is recorded in the same manner as in the recording using holography in the data area, and the pickup is set to the same state as during reproduction during servo operation, and the address is recorded. Information and the like may be detected by a smart optical sensor. In this case, the basic clock and the address can be obtained directly from the detection data of the smart optical sensor. The tracking error signal can be obtained from information on the position of the reproduction pattern on the smart optical sensor. The focus servo can be performed by driving the objective lens 12 so that the contrast of the reproduction pattern on the smart optical sensor is maximized. Also, at the time of reproduction, it is possible to perform focus servo by driving the objective lens 12 so that the contrast of the reproduction pattern on the smart optical sensor is maximized.

In the case where the light beam is modulated in accordance with the information to be recorded, in the embodiment, the light beam is modulated by the light intensity. In addition, the light beam is modulated by a difference in polarization or a phase difference of light. Is also good.

[0057]

As described above, according to the optical information recording apparatus according to any one of claims 1 to 6, the information recording layer of the optical information recording medium on which information is recorded by using holography is used. By the recording reference light irradiating means, irradiating the recording reference light from one surface side, by the information light irradiating means, irradiating the information light from the other surface side, to the information recording layer,
Since information is recorded by an interference pattern due to the interference between the recording reference light and the information light, the optical system for recording can be made small, and the intensity change of the reproduction light with respect to the thickness of the information recording layer can be reduced. This has the effect that it can be reduced.

According to the optical information reproducing apparatus of the present invention, the recording reference light radiated from one side and the information light radiated from the other side are utilized by utilizing holography. The information recording layer of the optical information recording medium on which the information is recorded by the interference pattern due to the interference of the light is irradiated with the reproduction reference light corresponding to the recording reference light from one side by the reproduction reference light irradiation means. Then, the reproduction light detecting means collects and detects the reproduction light generated from the information recording layer by being irradiated with the reproduction reference light from the same surface as the surface to which the reproduction reference light is irradiated. Because it was
The optical system for reproduction can be made small, and the change in intensity of the reproduction light with respect to the thickness of the information recording layer can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a pickup and an optical information recording medium in an optical information recording / reproducing apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing an overall configuration of the optical information recording / reproducing apparatus according to the first embodiment of the present invention.

FIG. 3 is a perspective view illustrating a configuration of a laser coupler in FIG. 1;

FIG. 4 is a side view of the laser coupler in FIG. 1;

FIG. 5 is a block diagram illustrating a configuration of a detection circuit in FIG. 2;

FIG. 6 is an explanatory diagram showing states of a recording reference light and an information light in a hologram layer at the time of recording by the pickup shown in FIG. 1;

FIG. 7 is an explanatory diagram showing a state of the pickup shown in FIG. 1 during reproduction.

FIG. 8 is an explanatory diagram showing a state of a reproduction reference light and a reproduction light in a hologram layer during reproduction of the pickup shown in FIG. 1;

FIG. 9 is an explanatory diagram showing a configuration of a pickup in an optical information recording / reproducing apparatus according to a second embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a state at the time of reproduction of the pickup shown in FIG. 9;

FIG. 11 is a perspective view showing a schematic configuration of a recording / reproducing system in conventional digital volume holography.

FIG. 12 is an explanatory diagram showing an optical information recording / reproducing device and an optical information recording medium proposed by the present applicant.

FIG. 13 is a characteristic diagram showing a relationship between the thickness of the hologram recording medium and the diffraction efficiency.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical information recording medium, 2 ... Transparent substrate, 3 ... Hologram layer, 4 ... Protective layer, 5 ... Semi-reflective film, 10 ... Optical information recording / reproducing apparatus, 11 ... Pickup, 12 ... Objective lens, 14 ...
Half mirror, 15: CCD array, 18: Spatial light modulator, 19: Coupling lens, 20: Laser coupler,
50: coupling lens, 51: optical fiber

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G11B 7/135 G11B 7/135 Z

Claims (8)

[Claims] 1. An optical information recording apparatus for recording information on an optical information recording medium having an information recording layer on which information is recorded using holography, comprising: A recording reference light irradiating means for irradiating a recording reference light from one surface side; and an interference caused by interference of the recording reference light on the information recording layer from the other surface side with respect to the information recording layer. An optical information recording device, comprising: an information light irradiating unit that irradiates an information light carrying information to be recorded so that information is recorded in a pattern. 2. An optical information recording apparatus according to claim 1, wherein said information light irradiating means has a modulating means for spatially modulating light according to information to be recorded. 3. The recording reference light irradiating means and the information light irradiating means use a light source for emitting light used for generating the recording reference light and the information light, and a light emitted from the light source. 2. The optical information recording apparatus according to claim 1, wherein the optical information recording apparatus shares a branching unit for branching the light emitted from the light source to generate the recording reference light and the information light. 4. The optical information recording medium according to claim 1, wherein the light source and the branching unit are disposed on one of a surface of the optical information recording medium irradiated with the recording reference light and a surface of the optical information recording medium irradiated with the information light. One of the reference light irradiating means and the information light irradiating means guides the light branched by the branching means from the surface of the optical information recording medium on which the branching means is provided to the opposite surface. 4. The optical information recording apparatus according to claim 3, further comprising an optical unit. 5. The optical information recording apparatus according to claim 4, wherein said light guiding means includes an optical fiber. 6. The optical information recording apparatus according to claim 4, wherein said light guide means includes a plurality of mirrors for transmitting light. 7. Using holography, an information recording layer on which information is recorded by an interference pattern caused by interference between a recording reference light emitted from one surface and an information light emitted from the other surface. An optical information reproducing apparatus for reproducing information from an optical information recording medium, comprising: irradiating the information recording layer with reproduction reference light corresponding to the recording reference light from one surface side. Reproducing reference light irradiating means, the reproducing light generated from the information recording layer by irradiating the reproducing reference light by the reproducing reference light irradiating means, the same as the surface side to which the reproducing reference light is irradiated An optical information reproducing apparatus comprising: a reproducing light detecting unit that collects and detects from a surface side. 8. The optical information reproducing apparatus according to claim 7, wherein said reproducing light is light which is spatially modulated according to information, and wherein said detecting means detects a pattern of the reproducing light.