JPWO2011081107A1 - Optical information processing apparatus and optical information processing method - Google Patents

Abstract

This optical information processing device (1) provides information for controlling the incident angle of the beam light condensed on the optical information recording medium (2) for each recording information that can be recorded on the optical information recording medium (2). The incident angle control data storage unit (12) that stores the incident angle control data shown in association with each other and one or more incident angle control data are acquired from the incident angle control data storage unit (12) when recording or reproducing information. And a controller (11) for controlling the incident angle of the beam light focused on the optical information recording medium (2) based on the acquired one or more incident angle control data.

Description

  The present invention relates to an optical information processing apparatus and an optical information processing method that perform at least one of recording information on an optical information recording medium and reproducing information recorded on the optical information recording medium.

  As a technique for recording information on an optical information recording medium, a technique is known that is performed depending on whether or not a diffraction grating is formed on the optical information recording medium. In the diffraction grating, two coherent light beams facing each other are condensed on an optical information recording medium, and standing waves generated by the interference between the two light beams alter the recording material (recording layer). It is formed. In the above-described recording technique, this is used to form a diffraction grating when recording binarized information “1” and recording binarized information “0” at the time of recording information. No diffraction grating is formed. As described above, in the recording technique described above, the information is recorded depending on whether or not the diffraction grating is formed according to the information recorded at the recording position of the optical information recording medium.

  As a technique for reproducing information recorded on an optical information recording medium, a technique is known that is performed by detecting reflected light from a diffraction grating formed on the optical information recording medium. When a diffraction grating is formed on the optical information recording medium, if the light beam having the same condition as one of the two light beams used at the time of recording is focused on the recording position from one side of the optical information recording medium The light beam is reflected by the diffraction grating. On the other hand, when the diffraction grating is not formed at the recording position of the optical information recording medium, the beam light is not reflected even if the light beam is condensed at the recording position from one surface side of the optical information recording medium ( That is, it is transmitted). By utilizing this, in the above reproduction technique, at the time of information reproduction, the beam light having the same condition as one of the two light beams used at the time of recording is transmitted from one surface side of the optical information recording medium to the recording position. When the light is condensed and the reflected light is detected, since the diffraction grating is formed at the time of recording, the binarized information “1” is reproduced. On the other hand, when the reflected light is not detected, the binarized information “0” is reproduced. That is, in this reproduction technique, recorded information is reproduced by detecting reflected light from the recording position of the optical information recording medium.

  As described above, in the conventional technique, information recording is performed depending on whether or not a diffraction grating is formed at the recording position of the optical information recording medium. On the other hand, the reflected light of the light beam irradiated to the recording position of the optical information recording medium is reflected. Information reproduction can be performed depending on whether or not it is detected. However, since information recorded / reproduced at each recording position is 1 bit, the recording capacity is limited and a sufficient recording capacity may not be obtained.

  As a technique for increasing the recording capacity of an optical information recording medium, a technique for recording and reproducing information of multiple bits at each recording position of the optical information recording medium (so-called multiple recording / reproducing technique) has been proposed (Patent Document 1). Thru 3). Patent Documents 1 to 3 disclose an angle multiplex recording / reproducing technique used for page-type hologram recording.

  In angle multiplex recording, an information recording operation performed at each recording position of the optical information recording medium is performed at a constant angle. For example, when the information recording operation is performed three times depending on whether or not the diffraction grating is formed at a certain angle, 3-bit information can be recorded.

  In the angle multiplex reproduction, the information reproduction operation performed at each recording position of the optical information recording medium is performed at the same constant angle as that during the information recording operation. For example, when the information reproducing operation is performed three times depending on whether or not the reflected light of the beam light is detected at a certain angle, 3-bit information can be reproduced.

JP 2008-226434 A JP 2008-268829 A JP 2009-80906 A

  The optical information recording medium is altered every time a diffraction grating is formed during information recording, and the refractive index of the recording position changes. The optical information recording medium has a refractive index change threshold (Δn) that allows a change in refractive index, and information is recorded when a refractive index change exceeding the threshold (Δn) is applied to the recording position of the optical information recording medium. Can not.

Further, the refractive index change threshold (Δn) is Δn << 1, and the diffraction efficiency (η) of the diffraction grating when N diffraction gratings are formed at the same position is η = (Δn / N) ² , As the number of diffraction gratings increases, the diffraction efficiency (η) decreases significantly.

  Thus, the number of diffraction gratings that can be formed at the same position is limited by the refractive index change threshold (Δn) and the diffraction efficiency (η). That is, the number of bits that can be recorded / reproduced at the recording position is determined by the refractive index change and the diffraction efficiency when the diffraction grating is formed. For this reason, the conventional technique has a problem that more information recording / reproduction cannot be performed.

  The present invention has been made in view of the above circumstances, and an optical information processing apparatus and an optical information recording / reproducing apparatus that record and reproduce more information while the number of diffraction gratings that can be formed at each recording position is limited. The purpose is to provide an information processing method.

An optical information processing apparatus according to a first aspect of the present invention provides:
An optical information processing apparatus that performs at least one of recording and reproduction of information on an optical information recording medium,
Incident angle control data stored in association with incident angle control data indicating information for controlling the incident angle of the light beam condensed on the optical information recording medium for each recording information that can be recorded on the optical information recording medium Storage means;
When recording or reproducing information, one or a plurality of the incident angle control data is acquired from the incident angle control data storage means, and collected on the optical information recording medium based on the acquired one or a plurality of incident angle control data. Control means for controlling the incident angle of the light beam to be emitted.

An optical information processing method according to a second aspect of the present invention includes:
An optical information processing method for performing at least one of information recording and reproduction on an optical information recording medium,
Stores incident angle control data indicating information for controlling the incident angle of beam light condensed on the optical information recording medium for each recording information that can be recorded on the optical information recording medium at the time of recording or reproducing information. An incident angle control data acquisition step of acquiring one or a plurality of the incident angle control data from a predetermined memory;
And a control step of controlling the incident angle of the beam light condensed on the optical information recording medium based on one or a plurality of incident angle control data acquired in the incident angle control data acquisition step. And

  According to the present invention, more information can be recorded and reproduced while the number of diffraction gratings that can be formed at each recording position is limited.

It is a block diagram which shows the structure of the optical information processing apparatus which concerns on embodiment of this invention. It is a figure which shows the data structure of the incident angle control data memorize | stored in the incident angle control data memory | storage part which concerns on embodiment of this invention. 1 is a diagram showing an optical information recording medium according to an embodiment of the present invention. It is a figure which shows the structure of the optical unit which concerns on embodiment of this invention. It is a figure which shows four opening of the active wavelength plate of the optical unit which concerns on embodiment of this invention. It is a figure which shows four variable openings of the shutter which concerns on embodiment of this invention. It is a figure which shows four light-receiving parts of the photodetector which concerns on embodiment of this invention. It is a block diagram which shows the internal structure of the optical unit drive part which concerns on embodiment of this invention. It is a figure which shows the beam light condensed at the recording position of an optical information recording medium by incident angle (theta) 1 at the time of information recording. It is a figure which shows the beam light condensed at the recording position of an optical information recording medium by incident angle (theta) 2 at the time of information recording. It is a figure which shows the beam light condensed at the recording position of an optical information recording medium by incident angle (theta) 3 at the time of information recording. It is a figure which shows the beam light condensed at the recording position of an optical information recording medium by incident angle (theta) 4 at the time of information recording. It is a figure which shows the beam light condensed on the recording position of an optical information recording medium by incident angle (theta) 1 at the time of information reproduction. It is a figure which shows the beam light condensed at the recording position of an optical information recording medium by incident angle (theta) 2 at the time of information reproduction. It is a figure which shows the beam light condensed at the recording position of an optical information recording medium by incident angle (theta) 3 at the time of information reproduction. It is a figure which shows the beam light condensed on the recording position of an optical information recording medium by incident angle (theta) 4 at the time of information reproduction. It is the figure which showed the relationship between the angle of the beam light condensed on the diffraction grating formed at the time of information recording, and a signal level. It is a figure which shows another structure of the optical unit which concerns on embodiment of this invention.

  An embodiment of the present invention will be described with reference to the drawings. In the present embodiment, a mode in which 2-bit information recording / reproduction is performed at each recording position of the optical information recording medium will be described.

  As shown in FIG. 1, the optical information processing apparatus 1 is roughly divided into a controller 11, an incident angle control data storage unit 12, an optical unit driving unit 13, and a condensing point moving mechanism driving unit 14. And an optical unit 100 and a condensing point moving mechanism 140. With these configurations, the optical information processing apparatus 1 records information on the optical information recording medium 2 and reproduces information recorded on the optical information recording medium 2.

  The controller 11 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and is configured to centrally control the optical information processing apparatus 1.

  The controller 11 reads out an information recording / reproducing program stored in the ROM or the like in response to a request for information recording or a request for reproducing information input via an operation unit (not shown), and expands and executes the information recording / reproducing program in the RAM or the like. As a result, the optical information processing apparatus 1 is comprehensively controlled.

  The controller 11 records information on an optical information recording medium 2 supplied from a recording data input unit or a storage unit (not shown), and a recording request signal indicating an information recording request supplied via an operation unit or the like. Recording data to be received. Then, the controller 11 performs control to record information at each recording position of the optical information recording medium 2. The recording data received by the controller 11 is information (for example, “100001100110...”) Representing the data in a bit string.

  The controller 11 divides the received recording data according to the number of bits recorded at each recording position of the optical information recording medium 2. In this embodiment, since the number of bits of information to be recorded at each recording position of the optical information recording medium 2 is “2”, the controller 11 receives “10”, “00”, “01”. Divide the recorded data.

  The controller 11 acquires incident angle control data corresponding to the divided recording data from the incident angle control data storage unit 12, and operates the optical unit driving unit 13 based on information indicated by the acquired incident angle control data.

  In addition, the controller 11 receives a reproduction request signal indicating an information reproduction request supplied via an operation unit or the like and reproduces information recorded at each recording position of the optical information recording medium 2 during information reproduction. Do. The controller 11 acquires all incident angle control data from the incident angle control data storage unit 12 and operates the optical unit driving unit 13 based on each incident angle control data.

  Further, the controller 11 determines a point at which the optical unit 100 condenses the beam light on the optical information recording medium 2 during information recording and information reproduction (hereinafter referred to as a condensing point) and a surface of the optical information recording medium 2. A movement control signal for moving to a recording position in the thickness direction is supplied to the condensing point moving mechanism driving unit 14.

  The incident angle control data storage unit 12 includes incident angle control data indicating information for controlling the incident angle of the beam light focused on the optical information recording medium 2 in the recording information that can be recorded at each recording position of the optical information recording medium 2. Are stored in association with each other.

  In this embodiment, since the number of bits of information to be recorded at each recording position of the optical information recording medium 2 is “2”, the information that can be recorded is “00”, “01”, “10”, “11”. It becomes a kind. Accordingly, as shown in FIG. 2, the incident angle control data storage unit 12 has the incident angles of the corresponding light beams of “θ1”, “θ2”, “θ3”, “ Incident angle control data 1 to 4 for controlling to be θ4 ″ are stored.

  Each incident angle control data indicates which one of the variable openings 60a to 60d of the shutter 106a and the variable openings 60e to 60h of the shutter 106b, which will be described later, is opened during information recording and information reproduction. Contains information (see FIGS. 4 and 6). In addition, each incident angle control data includes light reception information indicating which one of light receiving portions 70a to 70d of a photodetector 110 of the optical unit 100, which will be described later, is a light reception target during information reproduction (FIG. 4). FIG. 7).

  The optical unit drive unit 13 applies various drive voltages to the optical unit 100 in order to operate the optical unit 100 under the control of the controller 11.

  The optical unit 100 operates with various driving voltages applied by the optical unit driving unit 13.

  The condensing point moving mechanism driving unit 14 applies a driving voltage or the like to the condensing point moving mechanism 140 in order to operate the condensing point moving mechanism 140 under the control of the controller 11.

  The condensing point moving mechanism 140 is operated by a driving voltage or the like applied by the condensing point moving mechanism driving unit 14 and records the condensing point in the optical information recording medium 2 in the surface and thickness direction of the optical information recording medium 2. Move to position. In addition, the condensing point moving mechanism 140 performs tracking control that rotates the optical information recording medium 2 and causes the condensing point to follow the track so that the condensing point is located at a predetermined position.

  As shown in FIG. 3, the optical information recording medium 2 includes a recording layer 202 sandwiched between two substrates 201a and 201b. As a material of the substrates 201a and 201b, for example, glass is used, and as a material of the recording layer 202, for example, a photopolymer is used. The recording layer 202 has a plurality of recording positions in its surface and thickness direction.

  Next, a specific configuration of the optical unit 100 will be described. As shown in FIG. 4, the optical unit 100 includes a light source 101, lenses 102a to 102e, condenser lenses 103a to 103d, an active wavelength plate 104, a polarizing beam splitter 105, shutters 106a and 106b, and a mirror 107a. To 107d, quarter-wave plates 108a and 108b, objective lenses 109a and 109b, and a photodetector 110.

  The light source 101 operates by being supplied with a constant current, and emits linearly polarized light having a single wavelength toward the lens 102a. As the light source 101, for example, a semiconductor laser can be employed.

  The lenses 102a to 102e respectively convert incident light from divergent light into parallel light or from parallel light into convergent light. In the present embodiment, as the lenses 102a to 102e, spherical lenses having convex shapes on both sides are employed as shown in FIG. 4, but the shape of the lenses is not limited. For example, a spherical lens having a concave shape on both sides, a spherical lens having a convex shape on one side and a concave shape on the other side, or an aspherical lens may be used.

  The active wave plate 104 operates when a voltage is applied, and the function as a quarter wave plate and the function as a half wave plate are switched according to the applied voltage. The active wavelength plate 104 is configured by sandwiching a liquid crystal layer such as a nematic liquid crystal having a uniaxial refractive index anisotropy between two substrates. A transparent electrode for applying an AC voltage to the liquid crystal layer is provided on the surface of the two substrates facing the liquid crystal layer.

  When an AC voltage having a predetermined effective value (for example, 2.5 V) is applied to the liquid crystal layer, the direction of the optical axis of the liquid crystal layer is a direction perpendicular to the optical axis of incident light and a direction parallel to the optical axis. The direction is the middle (angle 45 °). At this time, the phase difference between the polarization component in the direction parallel to the plane including the optical axis and the optical axis generated in the light transmitted through the liquid crystal layer and the polarization component in the direction perpendicular to the plane is π / 2, and the active wave plate 104 functions as a quarter-wave plate. The active wave plate 104 that functions as a quarter wave plate converts incident linearly polarized light into circularly polarized light.

  On the other hand, when an AC voltage having a predetermined effective value (for example, 0 V) is applied to the liquid crystal layer, the direction of the optical axis of the liquid crystal layer becomes a direction perpendicular to the optical axis of incident light. At this time, the phase difference between the polarization component in the direction parallel to the plane including the optical axis and the optical axis generated in the light transmitted through the liquid crystal layer and the polarization component in the direction perpendicular thereto is π, and the active wave plate 104 is 1 / It functions as a two-wave plate. The active wave plate 104 functioning as a half-wave plate changes the polarization direction of the incident linearly polarized light by 90 degrees.

  Further, as shown in FIG. 5, the active wavelength plate 104 is provided with four openings 50 a to 50 d on the surface from which the light beam is emitted. As a result, the light beam incident on the active wave plate 104 is split into four light beams by passing through the active wave plate 104.

  The polarization beam splitter 105 transmits the beam light having the P-polarized component parallel to the incident surface and reflects the beam light having the S-polarized component perpendicular to the incident surface. The polarization beam splitter 105 branches the optical path according to the polarization component of the beam light incident from the active wave plate 104.

  The shutter 106 a is provided on the optical path of the beam light reflected by the polarization beam splitter 105, and the shutter 106 b is provided on the optical path of the beam light reflected by the polarization beam splitter 105. As shown in FIG. 6, the shutter 106a includes variable openings 60a to 60d, and the shutter 106b includes variable openings 60e to 60h. The variable openings 60a to 60h are opened when a voltage is applied thereto. The variable openings 60a to 60h transmit the beam light when it is open, and block (not transmit) the beam light when it is closed. For example, ferroelectric liquid crystal shutters are used for the variable openings 60a to 60h.

  When the variable aperture 60a and the variable aperture 60h are opened, the beam light 80a transmitted through the variable aperture 60a is incident on the upper end position of the objective lens 109a as shown in FIG. 9A. The beam light 80a is incident from this position toward the recording position of the recording layer 202 of the optical information recording medium 2 at an incident angle “θ1”. The incident angle is an angle formed by the incident direction of the beam light incident on the optical information recording medium 2 and the normal direction of the optical information recording medium 2. On the other hand, the beam light 80h that has passed through the variable aperture 60h is incident on the lower end position of the objective lens 109b. The beam light 80h is incident from this position toward the recording position of the recording layer 202 of the optical information recording medium 2 at an incident angle “θ1”. The light beams 80a and 80h are condensed at the same position of the recording layer 202 of the optical information recording medium 2 at the incident angle “θ1”, and they interfere with each other, whereby the diffraction grating 203a corresponding to the incident angle “θ1” is formed. It is formed.

  When the variable aperture 60b and the variable aperture 60g are opened, the beam light 80b transmitted through the variable aperture 60b is at a position shifted upward from the center of the objective lens 109a as shown in FIG. 9B, and the beam light 80a. Is incident at a position lower than the incident position. The beam light 80b is incident from this position toward the recording position of the recording layer 202 of the optical information recording medium 2 at an incident angle “θ2”. On the other hand, the beam light 80g transmitted through the variable aperture 60g is incident at a position shifted downward from the center of the objective lens 109b and higher than the position where the beam light 80h is incident. The beam light 80g enters from the position toward the recording position of the recording layer 202 of the optical information recording medium 2 at an incident angle “θ2”. The light beams 80b and 80g are condensed at the same position of the recording layer 202 of the optical information recording medium 2 at the incident angle “θ2”, and they interfere with each other, whereby the diffraction grating 203b corresponding to the incident angle “θ2” is formed. It is formed.

  When the variable aperture 60c and the variable aperture 60f are opened, the beam light 80c transmitted through the variable aperture 60c is incident on a position shifted downward from the center of the objective lens 109a as shown in FIG. 9C. The beam light 80c enters from the position toward the recording position of the recording layer 202 of the optical information recording medium 2 at an incident angle “θ3”. On the other hand, the light beam 80f transmitted through the variable aperture 60f is incident on a position shifted upward from the center of the objective lens 109b. The beam light 80f is incident from this position toward the recording position of the recording layer 202 of the optical information recording medium 2 at an incident angle “θ3”. The light beams 80c and 80f are condensed at the same position of the recording layer 202 of the optical information recording medium 2 at the incident angle “θ3”, and they interfere with each other, whereby the diffraction grating 203c corresponding to the incident angle “θ3” is formed. It is formed.

  When the variable aperture 60d and the variable aperture 60e are opened, the beam light 80d transmitted through the variable aperture 60d is at the lower end position of the objective lens 109a and from the position where the beam light 80c is incident, as shown in FIG. 9D. Incident at a low position. The beam light 80d is incident at an incident angle “θ4” from this position toward the recording position of the recording layer 202 of the optical information recording medium 2. On the other hand, the beam light 80e transmitted through the variable aperture 60e is incident on the upper end position of the objective lens 109b and higher than the position where the beam light 80f is incident. The beam light 80e enters from the position toward the recording position of the recording layer 202 of the optical information recording medium 2 at an incident angle “θ4”. The light beams 80d and 80e are condensed at the same position of the recording layer 202 of the optical information recording medium 2 at the incident angle “θ4”, and they interfere with each other, whereby the diffraction grating 203d corresponding to the incident angle “θ4” is formed. It is formed. In the present embodiment, with respect to the normal direction of the optical information recording medium 2, the angle formed with the incident direction of the beam light incident from one side is positive, and the incident direction of the beam light incident from the other side is Assuming that the formed angle is negative, the incident light is θ1 = −43.5 °, θ2 = −14.5 °, θ3 = 14.5 °, θ4 = 43.5 °, and the angle interval Δθ = 29 °. Incident on the recording medium 2.

  The mirrors 107a to 107d are arranged to change the optical path and guide the beam light incident from the front member to the rear member.

  The quarter wave plates 108a and 108b convert linearly polarized light into circularly polarized light when the incident light beam is linearly polarized light, and convert circularly polarized light into linearly polarized light when the incident light beam is circularly polarized light.

  The objective lenses 109a and 109b face each other via the optical information recording medium 2, and the light beam in the first optical path focused by the objective lens 109a and the beam light in the second optical path focused by the objective lens 109b are light. The information recording medium 2 is arranged so as to be condensed at the same position. In this embodiment, as the objective lenses 109a and 109b, biconvex lenses are employed as shown in FIG. 4, but aspherical lenses may be used.

  The condensing lenses 103 a to 103 d are provided on the optical path of the beam light that passes through the polarization beam splitter 105. The condensing lenses 103a to 103d convert the incident beam light from parallel light to convergent light. In the present embodiment, biconvex lenses are used as the condenser lenses 103a and 103d as shown in FIG. 4, but the shape of the lenses is not limited. For example, a spherical lens having a concave shape on both sides, a spherical lens having a convex shape on one side and a concave shape on the other side, or an aspherical lens may be used.

  As shown in FIG. 7, the photodetector 110 includes four light receiving units 70 a to 70 d at the focal positions of the condenser lenses 103 a to 103 d. The light receiving units 70a to 70d receive the beam lights collected by the corresponding condensing lenses 103a to 103d, respectively. The photodetector 110 is composed of a light receiving element such as a CCD (Charge Coupled Device) or a PIN photodiode, for example.

  Next, the internal configuration of the optical unit driving unit 13 will be described. As shown in FIG. 8, the optical unit driving unit 13 includes a shutter driving unit 21, an active wavelength plate driving unit 22, a light source driving unit 23, and a received light signal acquisition unit 24.

  The shutter drive unit 21 receives from the controller 11 a shutter control signal for controlling the variable openings 60a to 60d of the shutter 106a and the variable openings 60e to 60h of the shutter 106b. Then, the shutter drive unit 21 applies a predetermined voltage to the variable openings 60a to 60d and the variable openings 60e to 60h that are to be opened indicated by the shutter control signal.

  The active wave plate driving unit 22 receives an active wave plate control signal for controlling the active wave plate 104 from the controller 11 and applies a predetermined voltage to the active wave plate 104 according to the active wave plate control signal. Specifically, the active wave plate driving unit 22 causes the active wave plate 104 to function as a quarter wave plate by applying an alternating voltage (for example, 2.5 V) having a predetermined effective value during information recording. Further, by applying an AC voltage (for example, 0 V) having a predetermined effective value during information reproduction, the active wavelength plate 104 is caused to function as a half-wave plate.

  The light source driving unit 23 receives a light source control signal for controlling the light source 101 from the controller 11 and supplies a constant current to the light source 101 according to the light source control signal.

  The light reception signal acquisition unit 24 specifies light detection units 70a to 70d that have been detected by receiving light reception signals from the light detection units 70a to 70d that have been detected at the time of information reproduction, and receives light reception information indicating the specified light reception units as a controller. 11 is supplied.

  Next, the operation of the optical information processing apparatus 1 according to this embodiment will be described. The operation of the optical information processing apparatus 1 is roughly divided into an information recording operation for recording information on the optical information recording medium 2 and an information reproducing operation for reproducing information recorded on the optical information recording medium 2.

  First, the information recording operation will be described. At the time of information recording, the controller 11 records on a recording request signal for requesting information recording input via an operation unit or the like, and an optical information recording medium 2 supplied from a recording data input unit or storage unit (not shown). The recording data is received, and the information recording program stored in the ROM or the like is read according to the received data, and the program is developed on the RAM or the like and executed.

  Specifically, when the controller 11 receives the recording data “1000011100110...”, The number of bits of information to be recorded at each recording position of the optical information recording medium 2 is “2”. , “00”, “01”..., The received recording data is divided.

  Subsequently, the controller 11 sequentially acquires incident angle control data corresponding to the divided recording data from the incident angle control data storage unit 12. For example, the controller 11 has “incident angle control data 3” corresponding to “10”, “incident angle control data 1” corresponding to “00”, “incident angle control data 2” corresponding to “01”,. Thus, the incident angle control data is sequentially acquired from the incident angle control data storage unit 12.

  Further, the controller 11 supplies a movement control signal for driving the condensing point moving mechanism 140 to the condensing point moving mechanism driving unit 14. In accordance with this, the condensing point moving mechanism driving unit 14 applies a driving voltage or the like for operation to the condensing point moving mechanism 140. The condensing point moving mechanism 140 is operated by a driving voltage applied by the condensing point moving mechanism driving unit 14 and is first at a position where information is recorded (position of the upper left corner of the recording layer 202 shown in FIG. 3). Control so that the focal point is located. The condensing point moving mechanism 140 performs tracking control that rotates the optical information recording medium 2 and causes the condensing point to follow the track.

  Hereinafter, the operation of recording information “10” at the recording position of the optical information recording medium 2 to be recorded first in this case will be described.

  The controller 11 outputs a shutter control signal for controlling the variable opening 60c of the shutter 106a and the variable opening 60f of the shutter 106b based on the shutter information 3 indicated by the “incident angle control data 3” corresponding to “10”. 21. In response to this, the shutter drive unit 21 applies a voltage to the variable opening 60c and the variable opening 60f to open the variable opening 60c and the variable opening 60f.

  In addition, the controller 11 supplies an active wave plate control signal for causing the active wave plate 104 to function as a quarter wave plate to the active wave plate driving unit 22. In response to this, the active wave plate driving unit 22 applies an AC voltage (for example, 2.5 V) having a predetermined effective value to cause the active wave plate 104 to function as a quarter wave plate.

  Further, the controller 11 supplies a light source control signal for controlling the light source 101 to the light source driving unit 23. In response to this, the light source driver 23 supplies a constant current to the light source 101 to operate the light source 101.

  In the optical unit 100, the light source 101 emits beam light (linearly polarized light) having a constant power toward the lens 102a. The light beam emitted from the light source 101 is collimated by the lens 102a and converted from linearly polarized light to circularly polarized light by the active wavelength plate 104 functioning as a quarter wavelength plate.

  In addition, the beam light is divided into four beam lights by the four openings 60 a to 60 d provided on the emission surface of the active wavelength plate 104, and each divided beam light is emitted to the polarization beam splitter 105.

  Of the circularly polarized light incident on the polarizing beam splitter 105, the S-polarized component beam light (about 50% of the incident light) is reflected by the polarizing beam splitter 105 and incident on the shutter 106a.

  The four light beams incident on the shutter 106a are transmitted through the open variable aperture 60c among the variable apertures 60a to 60d provided in the shutter 106a. The beam light 80c transmitted through the variable aperture 60c is shifted downward from the center of the objective lens 109a through the lens 102b, the mirror 107a, the lens 102c, the mirror 107b, and the quarter wavelength plate 108a as shown in FIG. 9C. Incident to the position. The beam light 80c is condensed from this position to the recording position of the recording layer 202 of the optical information recording medium 2 (position where information is first recorded) at an incident angle “θ3”.

  On the other hand, of the circularly polarized light incident on the polarizing beam splitter 105, the P-polarized component beam light (about 50% of the incident light) passes through the polarizing beam splitter 105 and enters the shutter 106b.

  The four light beams incident on the shutter 106b are transmitted through the variable opening 60f that is open among the variable openings 60e to 60h provided in the shutter 106b. The beam light 80f transmitted through the variable aperture 60f is shifted upward from the center of the objective lens 109b through the lens 102d, the mirror 107c, the lens 102e, the mirror 107d, and the quarter wavelength plate 108b as shown in FIG. 9C. Incident to the position. The beam light 80f is condensed from this position to the recording position of the recording layer 202 of the optical information recording medium 2 (position where information is first recorded) at an incident angle “θ3”.

  Therefore, at the recording position of the recording layer 202 of the optical information recording medium 2, the two light beams 80 c and 80 f facing each other are incident from the both sides (objective lenses 109 a and 109 b) of the optical information recording medium 2. It is condensed at θ3 ″. Then, the beam 80c and the beam 80f interfere with each other at this recording position, whereby the diffraction grating 203c corresponding to the incident angle “θ3” is formed. As a result, information corresponding to the first recording data “10” of the recording data divided by the controller 11 is recorded at the recording position of the optical information recording medium 2 where the information is recorded first.

  Thereafter, in order to record the next information at the recording position of the optical information recording medium 2, the controller 11 supplies a movement control signal for driving the condensing point moving mechanism 140 to the condensing point moving mechanism driving unit 14. Accordingly, the condensing point moving mechanism driving unit 14 applies a driving voltage or the like to the condensing point moving mechanism 140. The condensing point moving mechanism 140 is operated by a driving voltage or the like applied by the condensing point moving mechanism driving unit 14, and is next at a position where information is recorded (position of the upper left corner of the recording layer 202 shown in FIG. 3). Control so that the focal point is located. The condensing point moving mechanism 140 performs tracking control that rotates the optical information recording medium 2 and causes the condensing point to follow the track.

  Then, the incident angle control data (“incident angle control”) corresponding to the remaining divided recording data (“00”, “01”, “10”, “01”, “10”...) Acquired by the controller 11. Based on data 1 ”,“ incident angle control data 2 ”,“ incident angle control data 3 ”,“ incident angle control data 2 ”,“ incident angle control data 3 ”... Repeatedly. Thereby, at each recording position of the optical information recording medium 2, the beam light sequentially enters the incident angle “θ1”, the incident angle “θ2”, the incident angle “θ3”, the incident angle “θ2”, and the incident angle “θ3”. And diffraction gratings corresponding to the respective incident angles are sequentially formed.

  Through the above information recording operation, the recording data (“100001100110...”) Can be recorded on the optical information recording medium 2.

  Next, the information reproduction operation will be described. At the time of information reproduction, the controller 11 receives a reproduction request signal for requesting information reproduction input via the operation unit or the like, reads out an information reproduction program stored in the ROM or the like in response to this, and stores the information reproduction program in the RAM or the like. Expand and run.

  Specifically, the controller 11 receives all the incident angle control data (incident angle control data 1) from the incident angle control data storage unit 12 in accordance with a reproduction request for the recorded data ("100001100110 ...") recorded at the time of information recording. ~ 4).

  Further, the controller 11 supplies a movement control signal for operating the condensing point moving mechanism 140 to the condensing point moving mechanism driving unit 14. Accordingly, the condensing point moving mechanism driving unit 14 applies a driving voltage or the like to the condensing point moving mechanism 140. The condensing point moving mechanism 140 is operated by the driving voltage applied by the condensing point moving mechanism driving unit 14 and is collected at a position where the first information is reproduced (the upper left corner position of the recording layer 202 shown in FIG. 3). Control so that the light spot is located. The condensing point moving mechanism 140 performs tracking control that rotates the optical information recording medium 2 and causes the condensing point to follow the track.

  Hereinafter, in this case, an operation for reproducing the information first recorded at the recording position of the optical information recording medium 2 will be described.

  The controller 11 determines all the variable values of the shutter 106a based on the shutter information indicated by the “incident angle control data 1”, “incident angle control data 2”, “incident angle control data 3”, and “incident angle control data 4”. A shutter control signal for operating the openings 60 a to 60 d and all the variable openings 60 e to 60 h of the shutter 106 b is supplied to the shutter driving unit 21. In response to this, the shutter drive unit 21 applies voltages to the variable openings 60a to 60d and the variable openings 60e to 60h to open the variable openings 60a to 60d and the variable openings 60e to 60h.

  In addition, the controller 11 supplies an active wave plate control signal for causing the active wave plate 104 to function as a half wave plate to the active wave plate driving unit 22. In response to this, the active wave plate driving unit 22 applies an AC voltage (for example, 0 V) having a predetermined effective value to the active wave plate 104 to cause the active wave plate 104 to function as a half wave plate.

  Further, the controller 11 supplies a light source control signal for operating the light source 101 to the light source driving unit 23. In response to this, the light source driver 23 supplies a constant current to the light source 101 to operate the light source 101.

  In the optical unit 100, the light source 101 emits beam light (linearly polarized light) having a constant power toward the lens 102a. The beam light emitted from the light source 101 is collimated by the lens 102a, and the polarization direction of the linearly polarized light is changed by 90 degrees by the active wavelength plate 104 functioning as a half-wave plate.

  In addition, the beam light is divided into four beam lights by the four openings 60 a to 60 d provided on the emission surface of the active wavelength plate 104, and each divided beam light is emitted to the polarization beam splitter 105.

  The S-polarized component beam light incident on the polarization beam splitter 105 (about 100% of the incident light) is reflected by the polarization beam splitter 105 and incident on the shutter 106a. On the other hand, the P-polarized component beam light (about 0% of the incident light) is not incident on the polarization beam splitter 105, and the beam light is not incident on the shutter 106a.

  The four light beams incident on the shutter 106a are transmitted through all the open variable openings 60a to 60d. The light beams 90a to 90d transmitted through the variable apertures 60a to 60d pass through the lens 102b, the mirror 107a, the lens 102c, the mirror 107b, the quarter wavelength plate 108a, and the objective lens 109a, and the recording layer 202 of the optical information recording medium 2. Is condensed at the recording position (the position where information is first recorded).

  Therefore, at the time of information reproduction, as shown in FIGS. 10A to 10D, the light beams of incident angles “θ1” to “θ4” are recorded on the optical information recording medium 2 from one surface side (objective lens 109a side). The light is condensed at the recording position of the layer 202.

  At this recording position, only the light beam condensed at the same incident angle as that at the time of information recording is reflected by the diffraction grating formed at the time of information recording. On the other hand, when the light beam is collected at an incident angle different from that at the time of information recording, or when the diffraction grating is not formed at the recording position, the light beam is transmitted.

  In the present embodiment, the diffraction grating 203c is formed by the light beams 80c and 80f collected at the incident angle “θ3” at the position where the information of the recording layer 202 of the optical information recording medium 2 is first recorded. Accordingly, as shown in FIG. 10C, only the beam light 90c collected at the same incident angle θ3 as that at the time of information recording is reflected by the diffraction grating 203c, and is collected at the other incident angles θ1, θ2, and θ4. 90a, 90b, and 90d are transmitted.

  The reflected beam light 90c ′ reflected by the diffraction grating 203c passes through the objective lens 109a, the quarter-wave plate 108a, the mirror 107b, the lens 102c, the mirror 107a, and the lens 102b in the direction opposite to the above direction, and the shutter 106a. And enter the polarization beam splitter 105.

  The P-polarized component beam light incident on the polarization beam splitter 105 (about 100% of the incident light) passes through the polarization beam splitter 105 and passes through the variable aperture 60c, and a condensing lens 103c provided on the optical path of the beam light. And is received by the light receiving unit 70c of the photodetector 110.

  The light receiving unit 70 c that has detected the light supplies a light reception signal to the light reception signal acquisition unit 24 of the optical unit driving unit 13. The light reception signal acquisition unit 24 specifies the light detection unit 70c that has been detected by receiving the light reception signal, and supplies light reception information (light reception information 3) indicating the specified light reception unit 70c to the controller 11.

  In response to this, the controller 11 acquires “incident angle control data 3” corresponding to the received light information 3 from the incident angle control data storage unit 12, and information “10” associated with the “incident angle control data 3”. To get. As a result, the first information “10” recorded at the recording position of the optical information recording medium 2 is reproduced.

  Thereafter, in order to reproduce the next information from the recording position of the optical information recording medium 2, the controller 11 supplies a movement control signal for driving the condensing point moving mechanism driving unit 14 to the condensing point moving mechanism driving unit 14. To do. Accordingly, the condensing point moving mechanism driving unit 14 applies a driving voltage or the like to the condensing point moving mechanism 140. The condensing point moving mechanism 140 is operated by the driving voltage applied by the condensing point moving mechanism driving unit 14 and is collected at a position where the next information is reproduced (position of the upper left corner of the recording layer 202 shown in FIG. 3). Control so that the light spot is located. The condensing point moving mechanism 140 performs tracking control that rotates the optical information recording medium 2 and causes the condensing point to follow the track.

  Then, by repeatedly performing the same operation as described above, the controller 11 sequentially stores information “00” associated with “incident angle control data 1” and information “associated with“ incident angle control data 2 ”. The information of 10 bits associated with the incident angle control data sequentially acquired, such as “01”, information “10”... Associated with “incident angle control data 3”, is acquired.

  With the above information reproducing operation, the recorded data (“100001100110...”) Recorded at the time of information recording can be reproduced.

  As described above, according to the optical information processing apparatus 1 of the present embodiment, the control is performed to collect the beam light at the incident angles (θ1 to θ4) assigned for each recording information, and one diffraction grating is provided at each recording position. By forming, 2-bit information recording / reproduction can be performed. In this case, assuming that the maximum value of the refractive index change of the recording layer 202 of the optical information recording medium 2 is Δn, the refractive index change assigned to one diffraction grating is Δn. On the other hand, when performing 2-bit information recording / reproduction according to whether or not a diffraction grating is formed as in the prior art, a maximum of two diffraction gratings are required at the recording position. In this case, the refractive index change assigned to one diffraction grating is Δn / 2. Further, the diffraction efficiency of one diffraction grating is proportional to the square of the refractive index change. Therefore, the optical information processing apparatus 1 of the present embodiment can increase the diffraction efficiency of one diffraction grating by a factor of four, while the multiplicity is 2 as compared with the conventional one. As described above, according to the optical information processing apparatus 1 of the present embodiment, more information can be recorded and reproduced while the number of diffraction gratings that can be formed at each recording position is limited.

  Note that the incident angle interval (Δθ) of the beam light focused on the optical information recording medium 2 is the influence of crosstalk, which is the ratio of the signal level received from another diffraction grating to the signal level received from the diffraction grating to be reproduced. We must not receive it. That is, it is necessary not to receive reflected beam light from a diffraction grating other than the diffraction grating to be reproduced.

The size in the optical axis direction of the beam light condensed on the recording layer 202 of the optical information recording medium 2 by the objective lenses 109a and 109b is λ for the wavelength of light used for recording and reproduction, and NA for the objective lenses 109a and 109b. When the refractive index of the recording layer 202 is n ₀ , 4n ₀ λ / NA ² is given. Therefore, the size of the diffraction grating 203 formed in the recording layer 202 in the optical axis direction is also approximately 4n ₀ λ / NA ² . The diffraction efficiency (reflectance) of the diffraction grating when the incident angle of the light beam condensed on the optical information recording medium 2 is changed is obtained by the coupled wave theory.

  The relationship between the beam light condensed on the optical information recording medium 2 during information reproduction and the diffraction efficiency of the diffraction grating (relation between the recording wavelength and the reproduction wavelength) will be described with reference to FIG. At the time of recording information on the optical information recording medium 2, the incident angles of the light used for recording on the optical information recording medium 2 are θ1 = −43.5 °, θ2 = −14.5 °, θ3 = 14.5 °. , Θ4 = 43.5 °, and the angle interval was Δθ = 29 °.

  At the time of information reproduction, the incident angle of the beam light condensed on the optical information recording medium 2 was changed in the range of θ = −58 ° to + 58 °. In FIG. 11, the horizontal axis represents the reproduction angle, and the vertical axis represents the signal level obtained by normalizing the diffraction efficiency of the diffraction grating with the value when the reproduction angle coincides with the recording angle. In FIG. 11, four curves in the case where the recording angles are θ1 to θ4 are shown superimposed. In any case where the recording angle is “θ1” to “θ4”, the signal level is 1 when the reproduction angle coincides with the recording angle. However, the signal level decreases as the reproduction angle moves away from the recording angle, and the signal level becomes almost zero when the reproduction angle is separated from the recording angle by Δθ. In this case, reflected beam light from a diffraction grating other than the diffraction grating to be reproduced is not received.

  For example, in a diffraction grating formed under the condition of the incident angle θ1 at the time of information recording, the light receiving signal level when the light is condensed under the condition of the incident angle θ1 at the time of information reproduction is 1, and under the conditions of the incident angles θ2, θ3, and θ4. When collected, the signal level is almost zero. That is, it can be seen that reflected beam light from a diffraction grating other than the diffraction grating to be reproduced is not received and is not affected by crosstalk.

In the present embodiment, the mode in which 2-bit information recording / reproduction is performed at each recording position of the optical information recording medium 2 has been described. However, the present invention is not limited to recording / reproduction of 2-bit information. The number of bits that can be recorded is arbitrary as long as the following conditions are satisfied for the information recorded on the optical information recording medium 2 and the incident angle of the light beam condensed on the optical information recording medium 2.
2 ^d ≦ _p C _q
d: Number of bits of information to be recorded at each recording position of the optical information recording medium 2 ^d ; Number of information p; Set number of incident angles of beam light that can be focused on the optical information recording medium 2 q: Beam that can be focused Number of incident light angles selected from light

  The incident angle control data storage unit 12 stores incident angle control data for controlling the incident angle of beam light in association with each other for each piece of information of a plurality of bits.

  In consideration of the refractive index change and diffraction efficiency when the diffraction grating is formed, it is better that the number of diffraction gratings formed at each recording position of the optical information recording medium 2 is small. Therefore, it is better that the number of light beams to be selected is small. For example, when 2-bit recording information is expressed using incident angles (θ1 to θ4) in four directions, a beam light in one direction is selected rather than selecting a beam light in two directions from the beam light in four directions. Better. By doing so, one diffraction grating is formed, the refractive index change is smaller than when two diffraction gratings are formed, and the diffraction efficiency is not lowered.

  Further, in the present embodiment, the incident angle focused on the optical information recording medium 2 is selected by the variable openings 60a to 60d of the shutter 106a and the variable openings 60e to h of the shutter 106b. Not. For example, as shown in FIG. 12, the optical information recording medium 2 includes an inclination mechanism 120 that inclines around the condensing point, and an incident angle that is condensed on the optical information recording medium 2 is selected using the inclination mechanism 120. You may make it do. In this case, the incident angle control data includes tilt information for operating the tilt mechanism 120. With this configuration, the optical unit 100 shown in FIG. 4 does not need to divide the beam light, and the number of components can be reduced.

  Further, the optical information processing apparatus 1 uses the light beam that can be collected on the optical information recording medium 2 based on the data size of the requested recording data and the memory capacity of the optical information recording medium 2 at the time of recording. The number (q) of light beams to be selected and the number of bits (d) may be determined. For example, it is assumed that the number (p) of light beams that can be collected on the optical information recording medium 2 is five directions (incident angles θ1 to θ5), and there are 60 remaining recording positions on the optical information recording medium 2. To do. Here, when recording of recording data having a data size of 100 bits is requested, the optical information processing apparatus 1 (controller 11) determines the number of bits (d) of information to be recorded at each recording position as 2 bits. The number (q) of light beams to be selected from the light beams that can be condensed on the optical information recording medium 2 is determined as q = 1.

That is, in this case, by selecting the incident angles (θ1 to θ5) in one direction from the incident angles (θ1 to θ5) of the beam light that can be collected on the optical information recording medium 2 (2 ² ≦ ₅ C ₁ ). The recording data can be recorded. On the other hand, in the above case, when recording of recording data having a data size of 150 bits is requested, the optical information processing apparatus 1 (controller 11) sets the number of bits (d) of information to be recorded at each recording position to 3 The number of light beams (q) selected from the light beams that can be collected on the optical information recording medium 2 is determined as q = 2. That is, in this case, by selecting the incident angles (θ1 to θ5) in two directions from the incident angles (θ1 to θ5) of the beam light that can be collected on the optical information recording medium 2 (2 ³ ≦ ₅ C ₂ ). The recording data can be recorded.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

  This application is based on Japanese Patent Application No. 2009-298858 filed on Dec. 28, 2009. The specification, claims, and entire drawings are incorporated in this specification.

DESCRIPTION OF SYMBOLS 1 Optical information processing apparatus 2 Optical information recording medium 11 Controller 12 Incident angle control data memory | storage part 13 Optical unit drive part 14 Condensing point moving mechanism drive part 21 Shutter drive part 22 Active wavelength plate drive part 23 Light source drive part 24 Light reception signal Acquisition unit 50a, 50b, 50c, 50d Opening 60a, 60b, 60c, 60d, 60e, 60f, 60g, 60h Variable opening 70a, 70b, 70c, 70d Light receiving unit 80a, 80b, 80c, 80d, 80e, 80f, 80g, 80h Beam light 90a, 90b, 90c, 90d Beam light 90c 'Reflected beam light 100 Optical unit 101 Light source 102a, 102b, 102c, 102d, 102e Lens 103, 103a, 103b, 103c, 103d Condensing lens 104 Active wavelength plate 105 Polarized light Beam splitter 106a, 106b Shutter 107a, 107b, 107c, 107d Mirror 108a, 108b 1/4 wavelength plate 109a, 109b Objective lens 110 Photo detector 120 Tilt mechanism 140 Condensing point moving mechanism 201a, 201b Substrate 202 Recording layer 203, 203a , 203b, 203c, 203d diffraction grating

Claims (8)

An optical information processing apparatus that performs at least one of recording and reproduction of information on an optical information recording medium,
Incident angle control data stored in association with incident angle control data indicating information for controlling the incident angle of the light beam condensed on the optical information recording medium for each recording information that can be recorded on the optical information recording medium Storage means;
When recording or reproducing information, one or a plurality of the incident angle control data is acquired from the incident angle control data storage means, and collected on the optical information recording medium based on the acquired one or a plurality of incident angle control data. Control means for controlling the incident angle of the light beam to illuminate,
An optical information processing apparatus. The control means includes
When recording information on the optical information recording medium, the incident angle control data corresponding to the information is acquired from the incident angle control data storage means,
When reproducing information from the optical information recording medium, all the incident angle control data is acquired from the incident angle control data storage means.
The optical information processing apparatus according to claim 1. The relationship between the information recorded on the optical information recording medium and the incident angle of the condensed light beam is as follows: 2 ^d ≦ _p C _q
d: the number of bits of information to be recorded on the optical information recording medium p: the set number of incident angles of the beam light that can be condensed on the optical information recording medium q: the set number of incident angles of the selected beam light is satisfied,
The optical information processing apparatus according to claim 1 or 2. The incident angle control data includes shutter information for operating a shutter that controls an incident angle of the beam light condensed on the optical information recording medium,
The control means controls an incident angle of the beam light condensed on the optical information recording medium using the shutter information;
The optical information processing apparatus according to claim 1, wherein the optical information processing apparatus is an optical information processing apparatus. The incident angle control data has tilt information for operating a tilt mechanism that controls the incident angle of the beam light focused on the optical information recording medium,
The control means controls the incident angle of the beam light condensed on the optical information recording medium using the tilt information.
The optical information processing apparatus according to claim 1, wherein the optical information processing apparatus is an optical information processing apparatus. An optical information processing method for performing at least one of information recording and reproduction on an optical information recording medium,
Stores incident angle control data indicating information for controlling the incident angle of beam light condensed on the optical information recording medium for each recording information that can be recorded on the optical information recording medium at the time of recording or reproducing information. An incident angle control data acquisition step of acquiring one or a plurality of the incident angle control data from a predetermined memory;
A control step of controlling the incident angle of the beam light focused on the optical information recording medium based on one or a plurality of incident angle control data acquired in the incident angle control data acquisition step,
An optical information processing method. In the incident angle control data acquisition step,
When recording information on the optical information recording medium, the incident angle control data corresponding to the information is acquired from the memory,
When reproducing information from the optical information recording medium, all the incident angle control data is acquired from the memory.
The optical information processing method according to claim 6. The relationship between the information recorded on the optical information recording medium and the incident angle of the condensed light beam is as follows: 2 ^d ≦ _p C _q
d: the number of bits of information to be recorded on the optical information recording medium p: the set number of incident angles of the beam light that can be condensed on the optical information recording medium q: the set number of incident angles of the selected beam light is satisfied,
The optical information processing method according to claim 6 or 7,

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