JP2008287077A - Optical information recording and reproducing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a holographic recording and reproducing apparatus capable of stably recording and reproducing information even when a medium is tilted. <P>SOLUTION: The optical information recording and reproducing apparatus for recording and reproducing information through the use of signal light 100 and reference light 200 includes: a tilt sensor 14 for detecting the tilt of the information recording medium 7; a disc-tilt detection circuit 24 for obtaining information about the tilt of the information recording medium 7 based on the output of the tilt sensor 14, then, obtaining a disc tilt signal; a variable-angle mirror 5 for adjusting the incident angle of the reference light 200 on the information recording medium 7; a mirror angle detection circuit 21 for detecting the angle of the variable-angle mirror 5; an angle error detection circuit 23 for detecting an angle error based on the outputs of the mirror angle detection circuit 21 and the disc tilt detection circuit 24; and a mirror driving circuit 22 for driving the variable-angle mirror 5 based on the output of the angle error detection circuit 23. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical information recording / reproducing apparatus, and more particularly to an optical information recording / reproducing apparatus for correcting an incident angle of reference light.

In recent years, holographic memory has been rapidly developed as a next-generation mass storage technology. (For example, see Non-Patent Document 1)
FIG. 15 is a block diagram showing a schematic configuration of a general optical system of a hologram recording / reproducing apparatus using an angle multiplex recording method.

  At the time of recording, the light beam emitted from the laser light source 101 is branched into the signal light 100 and the reference light 200 by the beam splitter 102.

  The reference light 200 has its beam diameter enlarged by the beam expander 103 and enters the variable angle mirror 104.

  The reference light 200 reflected by the angle of the variable angle mirror 104 is incident on the hologram recording medium 120 through the relay lens 105.

  One signal light 100 is reflected by the mirror 106, and the light beam diameter is changed by the beam expander 107, and then enters the spatial light modulator 108.

  The signal light 100 spatially modulated by the spatial light modulator 108 is condensed on the recording medium 120 by the Fourier transform lens 109.

  The signal light 100 and the reference light 200 interfere with each other in the recording medium 120, and the interference fringes are recorded on the recording medium 120.

  By changing the pattern of the spatial light modulator 108 and simultaneously changing and recording the angle of the angle variable mirror 105, the page data is angularly multiplexed at the same position.

  During reproduction, the reference beam 200 is irradiated onto the recording medium 120 by the variable angle mirror 104, and the generated reproduction light is incident on the image sensor 111 through the Fourier transform lens 110.

By changing the incident angle of the illumination reference light 200, the page data recorded by angle multiplexing is read.
"High speed holographic data strage at 100 Gbit / in2" InPhase Technologies, ISOM / ODS 2005

  In the hologram recording / reproducing system as in the above prior art, very high accuracy is required for the incident angle of the reference light to the hologram recording medium.

  However, the inclination of the hologram recording medium varies depending on the driving environment and the like, and the incident angle of the reference light with respect to the hologram recording medium varies.

  In such a case, the contrast of interference fringes may be lowered during recording, or the diffraction efficiency of reproduction light may be deteriorated.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a holographic recording / reproducing apparatus that realizes stable recording / reproduction even when a medium is tilted.

  As a means for solving the above-mentioned problems, the present invention splits a light beam from a light source into two light beams by a splitter, and guides one of the branched light beams as a reference light and the other as a signal light to an information recording medium. Information is recorded on the information recording medium by causing interference, the reference light is irradiated to the information recording medium, light emitted from the information recording medium by irradiation of the reference light is received by an imaging device, and the light is received. In an optical information recording / reproducing apparatus for reproducing information based on light, a tilt sensor for detecting the tilt of the information recording medium, and tilt information of the information recording medium is obtained based on an output of the tilt sensor, and a disc tilt signal is obtained. A disk tilt detection circuit for obtaining the reference light, an angle variable mirror for adjusting an incident angle of the reference light to the information recording medium, and a mirror angle detection circuit for detecting the angle of the angle variable mirror. An angle error detection circuit for detecting an angle error based on the outputs of the mirror angle detection circuit and the disk tilt detection circuit, and a mirror drive for driving the angle variable mirror based on the output of the angle error detection circuit And a circuit.

  In addition, the present invention also splits a light beam from a light source into two light beams by a splitter, and guides and interferes with one of the branched light beams as reference light and the other as signal light to the information recording medium. Information is recorded on the information recording medium, the information recording medium is irradiated with the reference light, light emitted from the information recording medium is received by the imaging element by irradiation of the reference light, and information is reproduced based on the received light In the optical information recording / reproducing apparatus, a divided light receiving element that receives reference light reflected from the surface of the information recording medium, a disk inclination detection circuit that detects the inclination of the information recording medium based on light reception by the divided light receiving element, An angle error detection circuit for detecting an angle error based on an output of the disk tilt detection circuit; an angle variable mirror for adjusting an incident angle of the reference light to the information recording medium; And the home position detection circuit for detecting a home position in degrees variable mirror, on the basis of the output of the angle error detecting circuit, and having a, a mirror driving circuit for driving said tilting mirror.

  In addition, the present invention also splits a light beam from a light source into two light beams by a splitter, and guides and interferes with one of the branched light beams as reference light and the other as signal light to the information recording medium. Information is recorded on the information recording medium, the information recording medium is irradiated with the reference light, light emitted from the information recording medium is received by the imaging element by irradiation of the reference light, and information is reproduced based on the received light In the optical information recording / reproducing apparatus, a first divided light receiving element that receives the reference light reflected from the surface of the information recording medium, a second divided light receiving element that receives the reference light transmitted through the information recording medium, and A disc inclination detection circuit for detecting an inclination of the information recording medium based on light reception by the first divided light receiving element; and the reference light is transmitted from the information recording medium based on light reception by the second divided light receiving element. An angle of incidence detection circuit for detecting an angle of incidence, an angle error detection circuit for detecting an angle error based on outputs of the disk tilt detection circuit and the incidence angle detection circuit, and the reference light information recording medium And a mirror driving circuit for driving the angle variable mirror based on an output of the angle error detection circuit.

  According to the present invention, since the inclination of the recording medium is detected and the incident angle of the reference light with respect to the holographic recording medium can be controlled, a stable recording / reproducing operation can be performed.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 is a block diagram showing a configuration of a holographic recording / reproducing apparatus as a first embodiment of an optical information recording / reproducing apparatus according to the present invention.

  As shown in FIG. 1, 1 is a laser light source, 2 is a variable ND filter, 3 is a half-wave plate, 4 is a beam splitter, 5 is a variable angle mirror, 6 is a relay lens, and 7 is a hologram recording medium as an information recording medium. , 8 are mirrors, and 9 is a spatial light modulator. Further, 10 is a Fourier transform lens, 11 is a shutter, 12 is a Fourier transform lens, 13 is an image sensor, and 14 is an optical tilt sensor. The optical information recording / reproducing apparatus of the present embodiment has these.

  At the time of recording, the intensity of the laser light emitted from the laser light source 1 is adjusted by the variable ND filter 2, passes through the half-wave plate 3, and is branched to the signal light 100 by the beam splitter 4 and the other to the reference light 200. The

  The reference light 200 reflected by the beam splitter 4 enters the angle variable mirror 5.

  The reference light 200 whose direction is changed according to the angle of the variable angle mirror 5 passes through the relay lens 6 and is incident on the hologram recording medium 7 as substantially parallel light.

  On the other hand, the signal light 100 transmitted through the beam splitter 4 is reflected by the mirror 8 and enters the spatial modulation element 9.

  The signal light 100 spatially modulated into the data page pattern by the spatial modulation element 9 is condensed on the hologram recording medium 7 by the Fourier transform lens 10.

  The guided signal light 100 and reference light 200 interfere with each other in the hologram recording medium 7, and the interference fringes are recorded on the hologram recording medium 7.

  Further, by changing the angle of the variable angle mirror 5, the incident angle of the reference beam 200 to the hologram recording medium 7 can be changed, and recording can be performed with angle multiplexing.

  During reproduction, the signal light is blocked by the shutter 11 and only the reference light is irradiated onto the hologram recording medium 7.

  The generated reproduction light passes through the Fourier transform lens 12 and a data page pattern is detected by the image sensor 13.

  Further, the angle of incidence of the reference beam 200 on the hologram recording medium 7 is changed by the angle variable mirror 5, and the multiplexed recording data is sequentially reproduced.

  Here, in the present embodiment, the optical tilt sensor 14 is installed below the hologram recording medium 7 in order to detect the tilt of the hologram recording medium 7.

  FIG. 2 is a side view showing the configuration of the optical tilt sensor 14 for tilt detection.

  As is well known, the optical tilt sensor 14 includes an LED 15 and two photodiodes 16a and 16b, and an output corresponding to the angle of the hologram recording medium 7 can be obtained.

  The light emitted from the LED 15 is incident on the hologram recording medium 7 substantially perpendicularly.

  The reflected light from the surface of the hologram recording medium 7 is detected by the light receiving surfaces of the two photodiodes 16a and 16b arranged symmetrically in the radial direction of the hologram recording medium 7 with respect to the LED 15 light emitting portion.

  An electric signal based on the detected amount of reflected light is generated, and this electric signal is sent to the disk tilt detection circuit 24. A disk tilt signal is obtained by obtaining a difference between the two electric signals.

  The disk tilt signal is sent to the angle error detection circuit 23.

  The variable angle mirror 5 includes an angle detector (not shown), and the mirror angle detection circuit 21 outputs a mirror angle signal.

  The mirror angle signal is sent to the angle error detection circuit 23, and the differential output from the disk tilt signal is sent to the mirror drive circuit 22 as the angle error signal.

  The variable angle mirror 5 is rotated by the mirror drive circuit 22 and controls the incident angle of the reference light 200 so as to correct the tilt of the hologram recording medium 7.

  In the case of angle multiplex recording / reproduction, a predetermined offset is added to the control angle, and the incident angle of the reference light is changed.

  As described above, in this embodiment, since the incident angle of the reference light with respect to the holographic recording medium can be kept constant, a recording / reproducing signal can be stably obtained even when the disc tilt fluctuates. it can.

[Second Embodiment]
FIG. 3 is a block diagram showing a configuration of a holographic recording / reproducing apparatus as a second embodiment of the optical information recording / reproducing apparatus according to the present invention.

  Since the configuration of the optical system for irradiating the hologram recording medium 7 with the signal light 100 and the reference light 200 is the same as that of the first embodiment, the description thereof is omitted. Since only the configuration of the optical system that performs tilt detection is different, it will be described in detail below.

  The reference light 200 reflected from the surface of the holographic recording medium 7 passes through the condenser lens 17 and is received by the divided light receiving element 18.

  As shown in FIG. 4, the divided light receiving element 18 is divided into two equal parts in a direction perpendicular to the radial direction of the recording medium 7.

  The variable angle mirror 5 includes a home position detection circuit 25, and the reference light 200 can be deflected in a predetermined reference direction by returning the home position.

  If the outputs from the light receiving surfaces a and b of the divided light receiving element 18 are A and B, each output signal is sent to the disk tilt detection circuit 24, and a disk tilt signal TILT is output by the following calculation.

Disc tilt signal TILT = (A−B) / (A + B)
The divided light receiving element 18 is mounted with a medium having no inclination, and is adjusted and fixed so that the disk inclination signal TILT becomes 0 when the angle variable mirror 5 returns to the home position. FIG. 5 shows how the light beam is incident at this time.

  Next, the correction operation when the holographic recording medium 7 is tilted will be described.

  When the inclination of the magnitude of α occurs in the holographic recording medium 7, the disk inclination signal TILT ≠ 0. For example, the disk tilt signal TILT = X. FIG. 6 shows how the light beam is incident at this time.

  The disk tilt signal TILT is sent to the subsequent angle error detection circuit 23 and is output as it is to the mirror drive circuit 22 as the incident angle error IAE.

  The mirror drive circuit 22 drives the angle variable mirror 5 so that the incident angle error IAE output becomes X / 2. FIG. 7 shows how the light beam is incident at this time.

  Then, the incident angle error IAE = X / 2 at that time is reset to a new home position level, and information is recorded.

  Next, when the holographic recording medium 7 is tilted again and the change amount ΔIAE of the incident angle error signal reaches a predetermined value again, the angle variable mirror 5 is driven so that only half of the change amount remains with respect to the new home position level. . An example of ΔIAE is ΔIAE = Y, and an example of IAE is IAE = X / 2 + Y / 2.

  Then, the incident angle error IAE at that time is reset to a new home position level. The subsequent operation is the above-described repetition.

  Similarly, FIG. 8 shows how the light beam is incident during reproduction. The control of the variable angle mirror 5 is the same as in recording, and the reproduction light 300 is generated.

  In the case of angle multiplex recording / reproduction, a predetermined offset is added to the target value of the incident angle error IAE to change the incident angle of the reference light.

  In the present embodiment, in addition to the effects of the first embodiment, since the inclination is detected at the recording position, the incident angle can be controlled with higher accuracy.

[Third Embodiment]
FIG. 9 is a block diagram showing a configuration of a holographic recording / reproducing apparatus as a third embodiment of the optical information recording / reproducing apparatus according to the present invention.

  Since the configuration of the optical system that irradiates the hologram recording medium 7 with the signal light 100 and the reference light 200 is the same as that of the first embodiment, description thereof is omitted. Since only the configuration of the optical system that performs tilt detection is different, it will be described in detail below.

  The reference light 200 reflected from the surface of the holographic recording medium 7 passes through the condensing lens 17 and is received by the divided light receiving element 18 as the first divided light receiving element.

  The divided light receiving element 18 is divided into two equal parts in a direction perpendicular to the radial direction of the recording medium.

  On the other hand, the reference light 200 transmitted through the holographic recording medium 7 passes through the condenser lens 19 and is received by the divided light receiving element 20 as the second divided light receiving element.

  The state of the light receiving surfaces of the divided light receiving elements 18 and 20 is shown in FIG.

  Similarly, the divided light receiving element 20 is also divided into two equal parts in a direction perpendicular to the radial direction of the recording medium.

  The output from the light receiving surfaces a and b of the divided light receiving element 18 is A, and the outputs from the light receiving surfaces c and d of the B divided light receiving element 20 are C and D. Is required. This calculation is performed by the disk tilt detection circuit 24 and the incident angle detection circuit 25, respectively.

Disc tilt signal TILT = (A−B) / (A + B)
Incident angle signal IA = (C−D) / (C + D)
Outputs of the disk tilt detection circuit 24 and the incident angle detection circuit 25 are sent to the angle error detection circuit 23, and each incident error IAE is sent to the mirror drive circuit 22 by the following calculation.

Incident angle error IAE = (A−B) / (A + B) − (C−D) / (C + D)
The angle of the variable angle mirror 5 is feedback-controlled by the mirror drive circuit 22 so that the incident angle error IAE becomes a constant value.

  First, the operation during recording / reproduction will be described.

  Recording is performed with the incident angle of the reference beam 200 on the hologram recording medium 7 being a predetermined angle θ. FIG. 11 shows a state where the inclination of the hologram recording medium 7 is in the reference state.

  Next, the case where the inclination of the hologram recording medium 7 is changed will be described.

  As shown in FIG. 12, when the inclination of the recording medium changes in a direction (θ ′ = θ + α) in which the incident angle of the reference light to the recording medium increases, the incident light enters the divided light receiving element 18 from the hologram recording medium 7. The change in ray angle is 2α.

  At this time, since A <B and C = D, IAE ≠ 0.

  Then, the variable angle mirror 5 changes the angle of the reference beam 200 by α so that C <D as shown in FIG. 13, and stops at a position where IAE = 0.

  Here, the change in the light beam angle incident on the divided light receiving element 18 from the hologram recording medium 7 is α, and at the same time, the change in the light beam angle transmitted through the hologram recording medium 7 and incident on the divided light receiving element 20 is also α.

  At this time, the incident angle of the reference beam 200 to the recording medium is maintained at the original angle θ.

  At the time of reproduction, as shown in FIG. 14, control is performed so as to make the incident angle error IAE constant as in the case of recording, and signal light is reproduced.

  When performing angle multiplexing recording / reproduction, a predetermined offset is added to the target value of the incident angle error IAE, and the incident angle of the reference beam 200 is changed.

  In the present embodiment, in addition to the effects of the second embodiment, it is not necessary to return to the home position, and it is possible to correct the optical axis inclination of the optical system that emits the reference light. Therefore, a recording / reproducing signal can be obtained stably even when there is vibration or a change with time.

  The present invention relates to a holographic recording / reproducing apparatus that causes signal light indicating information and reference light to interfere with each other and records information using the interference fringes.

1 is a block diagram showing a configuration of a holographic recording / reproducing apparatus as a first embodiment of an optical information recording / reproducing apparatus according to the present invention. It is a side view which shows the structure of the optical inclination sensor 14 for inclination detection. It is a block diagram which shows the structure of the holographic recording / reproducing apparatus as 2nd Embodiment of the optical information recording / reproducing apparatus which concerns on this invention. 3 is a plan view showing a light receiving surface of a split sensor 15. FIG. It is a figure which shows the structure of the incident angle detection system at the time of recording in the 2nd Embodiment of this invention. It is a figure which shows the structure of the incident angle detection system at the time of recording in the 2nd Embodiment of this invention. It is a figure which shows the structure of the incident angle detection system at the time of recording in the 2nd Embodiment of this invention. It is a figure which shows the structure of the incident angle detection system at the time of reproduction | regeneration in the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the holographic recording / reproducing apparatus as 3rd Embodiment of the optical information recording / reproducing apparatus which concerns on this invention. 3 is a plan view showing a light receiving surface of a split sensor 17. FIG. It is a figure which shows the structure of the incident angle detection system at the time of recording in the 3rd Embodiment of this invention. It is a figure which shows the structure of the incident angle detection system at the time of recording in the 3rd Embodiment of this invention. It is a figure which shows the structure of the incident angle detection system at the time of recording in the 3rd Embodiment of this invention. It is a figure which shows the structure of the incident angle detection system at the time of reproduction | regeneration in the 3rd Embodiment of this invention. It is a figure which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser light source 2 Variable ND filter 3 Half wave plate 4 Beam splitter 5 Angle variable mirror 6 Relay lens 7 Hologram recording medium 8 Mirror 9 Spatial light modulation element 10 Fourier transform lens 11 Shutter 12 Fourier transform lens 13 Image sensor 14 Optical tilt sensor DESCRIPTION OF SYMBOLS 17 Condensing lens 18 Division | segmentation sensor 19 Condensing lens 20 Division | segmentation sensor 21 Mirror angle detection circuit 22 Mirror drive circuit 23 Angle error detection circuit 24 Disc inclination detection circuit 25 Home position detection circuit 26 Incident angle detection circuit

Claims (6)

The light beam from the light source is split into two light beams by a splitter, one of the branched light beams is used as reference light and the other as signal light, information is recorded on the information recording medium by being guided and interfered with the information recording medium,
In an optical information recording / reproducing apparatus that irradiates the information recording medium with the reference light, receives light emitted from the information recording medium by irradiating the reference light with an imaging device, and reproduces information based on the received light ,
An inclination sensor for detecting the inclination of the information recording medium;
A disc tilt detection circuit for obtaining tilt information of the information recording medium and obtaining a disc tilt signal based on the output of the tilt sensor;
An angle variable mirror for adjusting an incident angle of the reference light to the information recording medium;
A mirror angle detection circuit for detecting the angle of the variable angle mirror;
An angle error detection circuit for detecting an angle error based on outputs of the mirror angle detection circuit and the disk tilt detection circuit;
An optical information recording / reproducing apparatus comprising: a mirror driving circuit that drives the angle variable mirror based on an output of the angle error detection circuit. The tilt sensor includes a light source for emitting to the information recording medium,
A photodiode that receives light emitted from the light source and reflected from the information recording medium;
2. The optical information recording / reproducing apparatus according to claim 1, wherein the inclination is detected based on a received light amount of the photodiode. 3. The optical information recording / reproducing apparatus according to claim 2, wherein there are two photodiodes. The light beam from the light source is split into two light beams by a splitter, one of the branched light beams is used as reference light and the other as signal light, information is recorded on the information recording medium by being guided and interfered with the information recording medium,
In an optical information recording / reproducing apparatus that irradiates the information recording medium with the reference light, receives light emitted from the information recording medium by irradiating the reference light with an imaging device, and reproduces information based on the received light ,
A split light-receiving element that receives reference light reflected from the surface of the information recording medium;
A disk tilt detection circuit for detecting the tilt of the information recording medium based on the light received by the divided light receiving elements;
An angle error detection circuit for detecting an angle error based on the output of the disk tilt detection circuit;
An angle variable mirror for adjusting an incident angle of the reference light to the information recording medium;
A home position detection circuit for detecting a home position of the variable angle mirror;
An optical information recording / reproducing apparatus comprising: a mirror driving circuit that drives the angle variable mirror based on an output of the angle error detection circuit. 5. The optical information recording / reproducing apparatus according to claim 4, wherein a home position of the variable angle mirror is changed based on an inclination of the information recording medium. The light beam from the light source is split into two light beams by a splitter, one of the branched light beams is used as reference light and the other as signal light, information is recorded on the information recording medium by being guided and interfered with the information recording medium,
In an optical information recording / reproducing apparatus that irradiates the information recording medium with the reference light, receives light emitted from the information recording medium by irradiating the reference light with an imaging device, and reproduces information based on the received light ,
A first split light-receiving element that receives reference light reflected from the surface of the information recording medium;
A second split light-receiving element that receives reference light transmitted through the information recording medium;
A disk tilt detection circuit for detecting the tilt of the information recording medium based on light reception by the first divided light receiving element;
An incident angle detection circuit that detects an angle at which the reference light is incident on the information recording medium based on light reception by the second divided light receiving element;
An angle error detection circuit for detecting an angle error based on outputs of the disk tilt detection circuit and the incident angle detection circuit;
An angle variable mirror for adjusting an incident angle of the reference light to the information recording medium;
An optical information recording / reproducing apparatus comprising: a mirror driving circuit that drives the angle variable mirror based on an output of the angle error detection circuit.

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