JP2008097748A - Optical information recording and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information recording and reproducing device, wherein the miniaturization is attained by using a cross prism to branch luminous flux coming from a light source into a reference light for recording, a reference light for reproduction and a recording information light. <P>SOLUTION: By using the cross prism 3, the luminous flux from a laser source 1 are branched into the recording information light 19, the reference light 17 for recording and the reference light 18 for reproduction. That is, the incident luminous flux are tri-branched by the cross prism 3 into reflection lights in two directions and a transmitting light, and the reflection lights in the two directions become respectively the reference light 17 for recording and the reference light 18 for reproduction. The transmitting light from the cross prism 3 is emitted on a spatial optical modulation element 8 and spatially modulated to form the recording information light 19. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical information recording / reproducing apparatus, particularly a recording medium on which an information signal is recorded by forming a hologram on a recording material made of a photosensitive material, for example, a material that changes its refractive index when irradiated with light. The present invention relates to an optical information recording / reproducing apparatus that performs reproduction from the above.

  As such an optical information recording / reproducing apparatus, for example, those described in “The Angle Align Method of Reference Beam for Holographic Data Storage”, Optical Data Storage Topical Meeting Conference Proceedings, pp. 55-57, 2006 are known. (Non-Patent Document 1). FIG. 5 shows a part of the configuration of a conventional optical information recording / reproducing apparatus described in this document.

  The optical information recording / reproducing apparatus includes a laser light source 30 and a first beam splitter 32 and a second beam splitter 33 that branch the light flux from the laser light source 30. The incident light beam is branched into reflected light and transmitted light by the first beam splitter 32, and further, the reflected light is branched into reflected light and transmitted light by the second beam splitter 33.

  Each of the light beams thus branched is irradiated onto the recording medium 42 as the recording information light 45, the recording reference light 43, and the reproduction reference light 44, and the information signal is recorded or the recorded information signal is reproduced. be able to.

  First, the information signal recording method will be described with reference to FIG. The light beam emitted from the laser light source 30 is converted into a parallel light beam by the collimator lens 31, and is branched into a light beam that is transmitted through the first beam splitter 32 and a light beam that is reflected. The light beam that has passed through the first beam splitter 32 is reflected by the reflecting surface of the third beam splitter 34 and enters the spatial light modulator 36.

  The reflected light from the spatial light modulator 36 becomes recording information light 45 that is spatially modulated by the information signal to be recorded. The recording information light 45 passes through the third beam splitter 34 and the fourth beam splitter 35, enters the objective lens 38, and is irradiated so as to be condensed on the recording medium 42.

  Further, the light beam reflected by the first beam splitter 32 is branched into two by the second beam splitter 33 into reflected light and transmitted light. The reflected light is used as recording reference light 43, reflected by the first movable mirror 39, and applied to the recording medium 42. As a result of the recording information light 45 and the recording reference light 43 overlapping and interfering in the recording medium 42, interference fringes due to a change in refractive index form a hologram.

  At this time, it is assumed that the reproduction reference beam 44 is prevented from being irradiated onto the recording medium 42 by means such as a shutter (not shown). Here, by driving the first movable mirror 39 and changing the angle of the recording reference light 43 incident on the recording medium 42 in multiple stages, information signals can be multiplexed and recorded on the same part of the recording medium 42.

  Next, a conventional method for reproducing information signals from the recording medium 42 will be described. The light beam emitted from the laser light source 30 is converted into a parallel light beam by the collimator lens 31 and reflected by the first beam splitter 32 in the same manner as at the time of recording. The light beam that has passed through the second beam splitter 33 is reflected by the mirror 41 and the second movable mirror 40 and enters the recording medium 42 as reproduction reference light 44.

  The incident direction of the reproduction reference beam 44 is opposite to the recording reference beam 43 during recording. Reproduction information light 46 is generated by irradiating the hologram formed on the recording medium 42 with the reproduction reference beam 44. The reproduction information light 46 passes through the objective lens 38, is reflected by the fourth beam splitter 35, and reproduces an information signal by the detection element 37. At this time, the recording reference beam 43 is prevented from being irradiated onto the recording medium 42 by means such as a shutter (not shown).

Here, when an information signal is recorded by changing the irradiation direction of the recording reference beam 43 in multiple stages during recording, the second movable mirror 40 is driven, and the irradiation direction of the reproduction reference beam 44 is changed to the recording reference. Adjustment is made so that the light 43 is in the opposite relationship (180 degrees). By doing so, it is possible to reproduce a desired information signal from the multiplex recording.
“The Angle Align Method of Reference Beam for Holographic Data Storage”, Optical Data Storage Topical Meeting Conference Proceedings, pp.55-57, 2006

  In a conventional optical information recording / reproducing apparatus, two beam splitters for obtaining a recording reference light, a reproducing reference light, and a recording information light by dividing a light beam from a laser light source into three, that is, a first beam splitter 32 and a second beam splitter 33. As a result, the optical system becomes large, and there is a limit to downsizing the apparatus.

  An object of the present invention is to provide an optical information recording / reproducing apparatus that can be miniaturized by using a cross prism to split a light beam from a light source into recording reference light, reproduction reference light, and recording information light. .

  The present invention uses a cross prism to split a light beam from a light source into recording information light, recording reference light, and reproduction reference light. The cross prism splits the incident light beam into two directions of reflected light and transmitted light in two directions, and the reflected light in the two directions is used as recording reference light and reproduction reference light, respectively. The transmitted light is spatially modulated by irradiating the spatial light modulator and becomes recording information light. The optical system can be simplified because one cross prism branches into the recording information light, the recording reference light, and the reproduction reference light.

  According to the present invention, by providing one cross prism, the light beam can be branched into three, and two beam splitters are not required as in the prior art. Therefore, the optical system is smaller than the conventional one, and the apparatus can be miniaturized.

  Next, the best mode for carrying out the invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a configuration of a first embodiment of an optical information recording / reproducing apparatus according to the present invention. FIG. 1 shows the configuration of an optical system for recording or reproducing information on a recording medium. The recording circuit necessary for recording information on the recording medium, the reproducing circuit necessary for reproducing, focus control and tracking. A servo control circuit that performs control and the like is omitted. In addition, circuits and mechanisms such as a controller that controls the entire apparatus and a motor that rotationally drives the recording medium are also omitted. The same applies to the following embodiments.

  The gist of the present invention is that a cross prism 3 that branches the light beam from the laser light source 1 into three branches is provided. The cross prism 3 includes two transflective reflecting surfaces that intersect each other, and divides the incident light beam into two directions of reflected light and transmitted light in two directions, which are used as recording reference light, reproduction reference light, and recording information light, respectively. The recording medium 13 is irradiated.

  A first embodiment of the present invention will be described below with reference to FIG. In the figure, reference numeral 1 denotes a laser light source that generates laser light for recording or reproducing information signals. The light beam emitted from the laser light source 1 is converted into a parallel light beam by the collimator lens 2 and enters the cross prism 3. The cross prism 3 splits the incident light beam into three-way reflected light and transmitted light.

  The reflected light in the two directions is used as the recording reference light 17 and the reproduction reference light 18, and the transmitted light is spatially modulated as described later to be the recording information light 19. The recording reference light 17 and the reproduction reference light 18 are selectively applied to the recording medium 13 by opening and closing the first shutter 4 and the second shutter 5, respectively.

  First, when an information signal is recorded as shown in FIG. 1A, the first shutter 4 is opened, the second shutter 5 is closed, and only the recording reference light 17 is the first. , Is reflected by the first movable mirror 6 and is applied to the recording medium 13. In FIG. 1, the driving mechanism of these shutters is omitted.

  The light beam that has passed through the cross prism 3 enters the transmissive spatial light modulation element 8 and is spatially modulated by the information signal to be recorded to be recorded information light 19. The recording information light 19 passes through the polarization beam splitter 9 and the quarter wavelength plate 11, is incident on the objective lens 12, and is irradiated so as to be condensed on the recording medium 13.

  The recording medium 13 used here includes a substrate 14, a reflective film 15 formed on the substrate 14, and a recording layer 16 made of a material that changes in refractive index when irradiated with light. As a result of the recording information beam 19 and the recording reference beam 17 overlapping and interfering in the recording layer 16, interference fringes due to a change in refractive index form a hologram.

  Further, by driving the first movable mirror 6 and changing the angle of the recording reference light 17 incident on the recording medium 13 in multiple stages, it is possible to multiplex-record information signals on the same part of the recording medium 13. Further, during the recording operation, in order to prevent the reflected light of the recording reference light 17 from the recording medium 13 from becoming stray light and entering the optical path of the recording reference light 17 or re-entering the recording medium 13, It is desirable to drive the movable mirror 7 in a direction that does not affect the recording, for example.

  Next, when the information signal from the recording medium 13 is reproduced as shown in FIG. 1B, the spatial light modulation element 8 is controlled so as not to transmit the entire light beam, thereby recording the light beam recording medium. 13 is blocked. In addition, by setting the first shutter 4 in the closed state and the second shutter 5 in the open state, only the reproduction reference light 18 out of the reflected light beam from the cross prism 3 passes through the second shutter 5, Reflected by the two movable mirrors 7 and applied to the recording medium 13.

  The reproduction reference light 18 is reflected by the reflective film 15 of the recording medium 13 and then irradiated on the hologram formed on the recording layer 16, thereby producing reproduction information light 20. The reproduction information light 20 passes through the objective lens 12 and the quarter wavelength plate 11, is reflected by the polarization beam splitter 9, and is guided to the detection element 10. The information signal is reproduced from the detection signal of the detection element 10.

  Here, when the information signal is recorded by changing the irradiation direction of the recording reference light 17 in multiple stages during recording, the second movable mirror 7 is driven, and the irradiation direction of the reproduction reference light 18 is changed to the recording reference. Adjustment is made so that the light 17 is directly opposite (180 degrees). By doing so, it is possible to reproduce a desired information signal from the multiplex recording.

  Further, during the reproduction operation, in order to prevent the reflected light of the reproduction reference light 18 from the recording medium 13 from becoming stray light and entering the optical path of the reproduction reference light 18 or reentering the recording medium 13, It is desirable to guide the movable mirror 6 in a direction that does not affect reproduction, for example, by driving the movable mirror 6.

  Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 2, the same parts as those in FIG. In the present embodiment, the cross prism 3 and the polarization beam splitter 9 are integrated. The light beam emitted from the laser light source 1 is converted into a parallel light beam by the collimator lens 2 and enters the cross prism 3. Similarly, the cross prism 3 splits the incident light beam into three reflected light beams in two directions and transmitted light.

  The reflected light in the two directions is used as the recording reference light 17 and the reproduction reference light 18, and the transmitted light is spatially modulated as described later to be the recording information light 19. The recording reference light 17 and the reproduction reference light 18 are selectively applied to the recording medium 13 by opening and closing the first shutter 4 and the second shutter 5, respectively.

  First, when an information signal is recorded as shown in FIG. 2A, the first shutter 4 is in an open state, the second shutter 5 is in a closed state, and only the recording reference light 17 is the first. , Is reflected by the first movable mirror 6 and is applied to the recording medium 13.

  The light beam that has passed through the cross prism 3 is reflected by the integrated polarization beam splitter 9, further reflected by the mirror 23, and is incident on the polarization beam splitter 9 again. However, a first quarter-wave plate 21 is provided between the polarization beam splitter 9 and the mirror 23, and rotates the direction of linearly polarized light by 90 degrees. Therefore, the reflected light from the mirror 23 passes through the polarization beam splitter 9 and enters the reflective spatial light modulation / detection integrated element 24.

  The spatial light modulation / detection integrated element 24 is an element in which, for example, a reflective spatial light modulation element using liquid crystal or the like and a CMOS detection element or the like are integrated.

  In the integrated spatial light modulation / detection element 24, the light beam is spatially modulated by the information signal to be recorded and reflected as the recorded information light 19. The recording information light 19 is incident on the polarization beam splitter 9 again, and a second quarter-wave plate 22 is provided between the polarization beam splitter 9 and the spatial light modulation / detection integrated element 24. Since the direction of linearly polarized light is rotated 90 degrees by the second quarter-wave plate 22, the recording information light 19 is reflected by the polarization beam splitter 9, enters the objective lens 12, and is condensed on the recording medium 13. Irradiated.

  As a result of the recording information beam 19 and the recording reference beam 17 overlapping and interfering in the recording layer 16, interference fringes due to a change in refractive index form a hologram. Here, by driving the first movable mirror 6 and changing the angle of the recording reference beam 17 incident on the recording medium 13 in multiple stages, it is possible to multiplex-record information signals on the same part of the recording medium 13.

  Further, during the recording operation, in order to prevent the reflected light of the recording reference light 17 from the recording medium 13 from becoming stray light and entering the optical path of the recording reference light 17 or re-entering the recording medium 13, It is desirable to drive the movable mirror 7 in a direction that does not affect the recording, for example.

  Next, when the information signal from the recording medium 13 is reproduced as shown in FIG. 2B, the first shutter 4 is closed and the second shutter 5 is opened. As a result, only the reproduction reference light 18 out of the light flux reflected by the cross prism 3 passes through the second shutter 5, is reflected by the second movable mirror 7, and is applied to the recording medium 13.

  Further, the reproduction reference light 18 is reflected by the reflection film 15 of the recording medium 13 and then irradiated on the hologram formed on the recording layer 16, thereby producing reproduction information light 20. The reproduction information light 20 passes through the objective lens 12, is reflected by the polarization beam splitter 9, and is received by the spatial light modulation / detection integrated element 24. The information signal is reproduced from the signal of the integrated element 24.

  Further, during the reproduction operation, in order to prevent the reflected light of the reproduction reference light 18 from the recording medium 13 from becoming stray light and entering the optical path of the reproduction reference light 18 or reentering the recording medium 13, It is desirable to guide the movable mirror 6 in a direction that does not affect reproduction, for example, by driving the movable mirror 6.

  In the second embodiment, since the cross prism 3 and the polarization beam splitter 9 are integrated, the entire apparatus can be further downsized.

  Next, a third embodiment of the present invention will be described with reference to FIG. In FIG. 3, the same parts as those in FIG.

  In the present embodiment, when recording an information signal, the recording reference beam 17 is reflected by the reflection film 15 of the recording medium 13 and then overlaps with the recording information beam 19 in the recording layer 16 so as to interfere with the hologram. Form. When reproducing the information signal, the reproduction reference light 18 is irradiated on the hologram formed on the recording layer 16 before being reflected by the reflection film 15 of the recording medium 13, thereby reproducing the reproduction information. The point from which the light 20 is produced | generated differs from 1st Embodiment.

  This will be specifically described. First, when an information signal is recorded as shown in FIG. 3A, the first shutter 4 is in the open state and the second shutter 5 is in the closed state, and only the recording reference light 17 is the first. , Is reflected by the first movable mirror 6 and is applied to the recording medium 13. In FIG. 3, the driving mechanism of these shutters is omitted.

  The light beam that has passed through the cross prism 3 enters the transmissive spatial light modulation element 8 and is spatially modulated by the information signal to be recorded to be recorded information light 19. The recording information light 19 passes through the polarization beam splitter 9 and the quarter wavelength plate 11, is incident on the objective lens 12, and is irradiated so as to be condensed on the recording medium 13.

  The recording medium 13 used here includes a substrate 14, a reflective film 15 formed on the substrate 14, and a recording layer 16 made of a material that changes in refractive index when irradiated with light. After the recording reference light 17 is reflected by the reflective film 15 and overlaps with the recording information light 19 in the recording layer 16 and interferes, interference fringes due to a change in refractive index form a hologram.

  Further, by driving the first movable mirror 6 and changing the angle of the recording reference light 17 incident on the recording medium 13 in multiple stages, it is possible to multiplex-record information signals on the same part of the recording medium 13. Further, during the recording operation, in order to prevent the reflected light of the recording reference light 17 from the recording medium 13 from becoming stray light and entering the optical path of the recording reference light 17 or re-entering the recording medium 13, It is desirable to drive the movable mirror 7 in a direction that does not affect the recording, for example.

  Next, when reproducing an information signal from the recording medium 13 as shown in FIG. 3B, the spatial light modulation element 8 is controlled so as not to transmit the entire light beam, thereby recording the light beam recording medium. 13 is blocked. In addition, by setting the first shutter 4 in the closed state and the second shutter 5 in the open state, only the reproduction reference light 18 out of the reflected light beam from the cross prism 3 passes through the second shutter 5, Reflected by the two movable mirrors 7 and applied to the recording medium 13.

  The reproduction reference light 18 is irradiated onto the hologram formed on the recording layer 16 before being reflected by the reflection film 15 of the recording medium 13, thereby generating reproduction information light 20. The reproduction information light 20 passes through the objective lens 12 and the quarter wavelength plate 11, is reflected by the polarization beam splitter 9, and is guided to the detection element 10. The information signal is reproduced from the detection signal of the detection element 10.

  Here, when the information signal is recorded by changing the irradiation direction of the recording reference light 17 in multiple stages during recording, the second movable mirror 7 is driven, and the irradiation direction of the reproduction reference light 18 is changed to the recording reference. Adjustment is made so that the light 17 is directly opposite (180 degrees). By doing so, it is possible to reproduce a desired information signal from the multiplex recording.

  Further, during the reproduction operation, in order to prevent the reflected light of the reproduction reference light 18 from the recording medium 13 from becoming stray light and entering the optical path of the reproduction reference light 18 or reentering the recording medium 13, It is desirable to guide the movable mirror 6 in a direction that does not affect reproduction, for example, by driving the movable mirror 6.

  Next, a fourth embodiment of the present invention will be described with reference to FIG. In FIG. 4, the same parts as those in FIG.

  In the present embodiment, when recording an information signal, the recording reference beam 17 is reflected by the reflection film 15 of the recording medium 13 and then overlaps with the recording information beam 19 in the recording layer 16 so as to interfere with the hologram. Form. When reproducing the information signal, the reproduction reference light 18 is irradiated on the hologram formed on the recording layer 16 before being reflected by the reflection film 15 of the recording medium 13, thereby reproducing the reproduction information. The point from which the light 20 is produced | generated differs from 2nd Embodiment.

  This will be specifically described. First, when an information signal is recorded as shown in FIG. 4A, the first shutter 4 is in the open state and the second shutter 5 is in the closed state, and only the recording reference light 17 is the first. , Is reflected by the first movable mirror 6 and is applied to the recording medium 13.

  The light beam that has passed through the cross prism 3 is reflected by the integrated polarization beam splitter 9, further reflected by the mirror 23, and is incident on the polarization beam splitter 9 again. However, a first quarter-wave plate 21 is provided between the polarization beam splitter 9 and the mirror 23, and rotates the direction of linearly polarized light by 90 degrees. Therefore, the reflected light from the mirror 23 passes through the polarization beam splitter 9 and enters the reflective spatial light modulation / detection integrated element 24.

  The spatial light modulation / detection integrated element 24 is an element in which, for example, a reflective spatial light modulation element using liquid crystal or the like and a CMOS detection element or the like are integrated.

  In the integrated spatial light modulation / detection element 24, the light beam is spatially modulated by the information signal to be recorded and reflected as the recorded information light 19. The recording information light 19 is incident on the polarization beam splitter 9 again, and a second quarter-wave plate 22 is provided between the polarization beam splitter 9 and the spatial light modulation / detection integrated element 24. Since the direction of the linearly polarized light is rotated by 90 degrees by the second quarter-wave plate 22, the recording information light 19 is reflected by the polarization beam splitter 9, enters the objective lens 12 and is condensed on the recording medium 13. Irradiated.

  After the recording reference light 17 is reflected by the reflective film 15 and overlaps with the recording information light 19 in the recording layer 16 and interferes, interference fringes due to a change in refractive index form a hologram. Here, by driving the first movable mirror 6 and changing the angle of the recording reference beam 17 incident on the recording medium 13 in multiple stages, it is possible to multiplex-record information signals on the same part of the recording medium 13.

  Further, during the recording operation, in order to prevent the reflected light of the recording reference light 17 from the recording medium 13 from becoming stray light and entering the optical path of the recording reference light 17 or re-entering the recording medium 13, It is desirable to drive the movable mirror 7 in a direction that does not affect the recording, for example.

  Next, as shown in FIG. 4B, when the information signal from the recording medium 13 is reproduced, the first shutter 4 is closed and the second shutter 5 is opened. As a result, only the reproduction reference light 18 out of the light flux reflected by the cross prism 3 passes through the second shutter 5, is reflected by the second movable mirror 7, and is applied to the recording medium 13.

  Further, the reproduction reference light 18 is irradiated on the hologram formed on the recording layer 16 before being reflected by the reflection film 15 of the recording medium 13, thereby generating reproduction information light 20. The reproduction information light 20 passes through the objective lens 12, is reflected by the polarization beam splitter 9, and is received by the spatial light modulation / detection integrated element 24. The information signal is reproduced from the signal of the integrated element 24.

  Further, during the reproduction operation, in order to prevent the reflected light of the reproduction reference light 18 from the recording medium 13 from becoming stray light and entering the optical path of the reproduction reference light 18 or reentering the recording medium 13, It is desirable to guide the movable mirror 6 in a direction that does not affect reproduction, for example, by driving the movable mirror 6.

  In the fourth embodiment, as in the second embodiment, by integrating the cross prism 3 and the polarization beam splitter 9, it is possible to further reduce the size of the entire apparatus.

  Note that the present invention can also be applied to a recording medium that does not include the reflective film 15 as in the prior art shown in FIG. In this case, however, the reference light for reproduction at the time of information signal reproduction is irradiated from the opposite side to the reference light for recording at the time of information signal recording. Must be placed on the opposite side.

  However, if the recording medium 13 includes the reflective film 15 as in the above embodiment, the reproduction reference light and the recording reference light may be irradiated from the same surface side of the recording medium. Accordingly, since all of the optical system can be arranged on the same side, the entire apparatus can be further downsized.

It is a figure which shows the structure of 1st Embodiment of the optical information recording / reproducing apparatus based on this invention. It is a figure which shows the structure of the 2nd Embodiment of this invention. It is a figure which shows the structure of the 3rd Embodiment of this invention. It is a figure which shows the structure of the 4th Embodiment of this invention. It is a figure which shows the structure of the conventional optical information recording / reproducing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser light source 2 Collimator lens 3 Cross prism 4 1st shutter 5 2nd shutter 6 1st movable mirror 7 2nd movable mirror 8 Spatial light modulation element 9 Polarizing beam splitter 10 Detection element 11 1/4 wavelength plate 12 Objective lens 13 Recording medium 14 Substrate 15 Reflective film 16 Recording layer 17 Reference light for recording 18 Reference light for reproduction 19 Recorded information light 20 Reproduced information light 21 First quarter-wave plate 22 Second quarter-wave plate 23 Mirror 24 Spatial light modulation / detection integrated element

Claims (3)

A spatial light modulation element is irradiated with a light beam from a light source, a recording information light and a recording reference light generated by the spatial light modulation element are irradiated on a recording medium, and information is obtained by interference between the recording information light and the recording reference light. In an optical information recording / reproducing apparatus that performs signal recording, irradiates the recording medium with reproduction reference light from the light source, and reproduces an information signal from reproduction information light generated by the hologram, a light beam from the light source An optical information recording / reproducing apparatus comprising: a cross prism that branches into the recording information light, the recording reference light, and the reproduction reference light. The recording medium includes a reflective film, and the irradiation of the reference light for recording at the time of recording the information signal and the irradiation of the reference light for reproduction at the time of reproducing the information signal are performed from the same surface side of the recording medium. The optical information recording / reproducing apparatus according to claim 1. The optical information recording / reproducing apparatus according to claim 2, wherein the reproduction reference light is reflected by the reflective film after passing through an area where the information signal is recorded or before passing through the area.

Images