JP2010118092A - Optical head device, optical information recording/reproducing device, error signal generation method, and focus position adjusting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical head device detecting displacement of the focal point of a second beam, the optical head device focusing a first beam and the second beam on the same focal point. <P>SOLUTION: The optical head device includes: a beam focusing means for focusing a first beam and a second beam on the same focal point in the state of facing each other; an astigmatism application means for applying astigmatism to the first beam passing through the focal point; and an optical detecting means for detecting the first beam having the astigmatism applied thereto. The optical detection means includes a light reception part for receiving the optical spots 100a to 100i of the first beam having the astigmatism applied thereto to output a signal. The light reception part includes a first dividing line 101 and a second dividing line 102 orthogonal to each other, a third dividing line 103 inclined with respect to the first dividing line, and eight light receiving areas 21a to 21h separated from one another by a fourth dividing line 104 inclined with respect to the second dividing line. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical head device, an optical information recording / reproducing device, an error signal generation method, and a condensing position adjustment method.

  Optical signals can handle a larger amount of information than electrical signals. For this reason, recording and reproducing information using light has been conventionally performed. Information recording / reproducing technology using light has been developed from various aspects. For example, the technique disclosed in Patent Document 1 below relates to an optical head device that is excellent in reduction in size and weight and thickness. The technique disclosed in Patent Document 2 below relates to an optical pickup capable of preventing optical interference at a photodetector. In these patent documents 1 and 2, the dimension in the in-plane direction of the optical recording medium is used for recording information. Recently, as one of the technologies for increasing the capacity of optical recording media, a technology for recording and reproducing information three-dimensionally using the dimension in the thickness direction in addition to the dimension in the in-plane direction of the optical recording medium has been developed. . For example, Patent Document 3 below describes a technique for controlling the tilt of an objective lens when an interference pattern by two beams is recorded three-dimensionally on an optical recording medium. Non-Patent Document 1 below describes an optical head device for bit-type hologram recording. In the bit-type hologram recording / reproducing system, two opposing beams are condensed at the same position in the recording layer of the optical recording medium to interfere with each other, and a minute diffraction grating is formed at the focal point. Make a record. In the bit-type hologram recording / reproducing system, information is reproduced by condensing one of the two beams in the recording layer of the optical recording medium and detecting the reflected light from the diffraction grating. Do.

  The optical head device described in Non-Patent Document 1 will be described with reference to FIG. FIG. 2 is a configuration diagram of the optical head device. As shown in the figure, in this optical head device, the light emitted from the semiconductor laser 39a is transmitted through the convex lens 40a and converted from the divergent light to the parallel light, partly transmitted through the beam splitter 41a, and partly transmitted through the beam splitter. By being reflected by 41a, it is divided into two lights. Hereinafter, the transmitted light of the beam splitter 41a is referred to as “first beam”, and the reflected light of the beam splitter 41a is referred to as “second beam”.

  When recording information on the disk 38, the first beam is reflected by the interference filter 42, passes through the objective lens 45 a, is converted from parallel light into convergent light, and is collected in the recording layer of the disk 38. On the other hand, the second beam passes through the shutter 44 and a part thereof is reflected by the beam splitter 41b. The reflected second beam is reflected by the mirror 43, passes through the objective lens 45 b, is converted from parallel light into convergent light, and is collected in the recording layer of the disk 38. The first beam and the second beam are focused and interfered at the same position in the recording layer of the disk 38. Thereby, in the recording layer, a minute diffraction grating is formed at the condensing point. The diffraction grating formed in the recording layer has bit data information.

  After the condensing, the first beam passes through the recording layer of the disk 38, passes through the objective lens 45b, and is converted from divergent light to parallel light. The first beam that has become parallel light is reflected by the mirror 43, part of which passes through the beam splitter 41b, passes through the anamorphic lens system including the convex lens 40c and the cylindrical lens 47a, and converges from the parallel light. Converted to light. The first beam is given astigmatism when passing through the anamorphic lens system. The photodetector 46b receives the first beam given the astigmatism. Based on the output from the photodetector 46b, an error signal is generated that indicates the relative positional deviation of the condensing point of the second beam with respect to the condensing point of the first beam in the recording layer of the disk 38. Details of generation of the error signal will be described later.

  On the other hand, at the time of reproducing information from the disc 38, the first beam passes through the same optical path as that at the time of information recording and is condensed in the recording layer of the disc 38. On the other hand, the second beam is blocked by the shutter 44. The first beam condensed in the recording layer of the disk 38 is reflected by a diffraction grating formed at the condensing point. The reflected first beam passes through the objective lens 45a in the direction opposite to the optical path and is converted from divergent light into parallel light. The first beam converted into parallel light is reflected by the interference filter 42, part of the light is reflected by the beam splitter 41a, passes through the convex lens 40b, is converted from parallel light to convergent light, and is received by the photodetector 46a. Is done. In the photodetector 46a, the optical signal is converted into an electric signal, and reproduction data is generated from the electric signal.

  In recording information on the disk 38, the positions of the condensing points of the first beam and the second beam are moved in the thickness direction in addition to the in-plane direction of the optical recording medium, thereby forming a diffraction grating. Multi-layer recording can be performed in the thickness direction of the disk 38. As a result, the capacity of the disk 38 can be increased.

  The optical head device has an objective lens focal position deviation detection mechanism for detecting a focal position deviation of the objective lens 45a. The objective lens focal position deviation detection mechanism includes a semiconductor laser 39b, a convex lens 40d, a beam splitter 41c, a convex lens 40e, a cylindrical lens 47b, and a photodetector 46c. With the objective lens focal position deviation detection mechanism, it is possible to detect the positional deviation of the focal point of the objective lens 45a in the optical axis direction and the positional deviation of the disk 38 in the radial direction.

  In the optical recording / reproducing system of Non-Patent Document 1, in order to correctly record information, the condensing point of the first beam needs to coincide with the condensing point of the second beam. However, there is a case where the focal point is displaced in the optical axis direction, the radial direction of the disk 38, and the tangential direction (circumferential direction) of the disk. For example, if the thickness of the disk 38 is deviated from the standard value, a positional shift in the optical axis direction occurs between the condensing points of the two beams. Further, for example, when the disk 38 is inclined in the radial direction or tangential direction (circumferential direction), the positional deviation in the radial direction or tangential direction (circumferential direction) of the disk 38 is between the condensing points of the two beams. Arise. For this reason, the optical head device of Non-Patent Document 1 is provided with a condensing point position deviation detecting mechanism for detecting a positional deviation between the condensing points of the two beams.

As shown in FIG. 8, the condensing point position deviation detection mechanism includes a photodetector 46b, a convex lens 40c, and a cylindrical lens 47a. An anamorphic lens system is configured by the convex lens 40c and the cylindrical lens 47a, and a photodetector 46b is disposed between two focal lines configured by the anamorphic lens system. As described above, the first beam that has passed through the condensing point is given astigmatism and is received by the photodetector 46b. In the light receiving portion of the photodetector 46b, the first beam to which astigmatism is given is received as a light spot.

  FIG. 9A shows the pattern of the light receiving part of the photodetector 46b of the optical head device of Non-Patent Document 1 and the light spot on the light receiving part. In the figure, the X direction is a direction corresponding to the radial direction of the disk 38, the Y direction is a direction corresponding to the tangential direction (circumferential direction) of the disk 38, and the Z direction (perpendicular to the drawing in the figure). Direction) is a direction corresponding to the optical axis direction. In the same figure, dotted circles or ellipses indicated by 100a to 100i indicate the light spots. As shown in the figure, the light receiving portion of the photodetector 46b is divided into four light receiving regions 48a, 48b, 48c and 48d by a dividing line 101 parallel to the X direction and a dividing line 102 parallel to the Y direction. ing. The four light receiving regions are separated from each other by the dividing lines 101 and 102.

  FIGS. 9A (a) to 9A (c) show changes in the light spot in the case of a positional shift in the optical axis direction of the condensing point of the second beam with respect to the condensing point of the first beam. FIG. 9A (b) shows a case where the condensing points of the two beams coincide with each other, and the light spot 100b has a circular shape in which the intersection point and the center point of the dividing lines 101 and 102 coincide. On the other hand, when the condensing point of the second beam is displaced in the optical axis direction, as shown in FIG. 9A (a) and FIG. 9A (c), the light spot is +45 in the clockwise direction with respect to the X direction. It becomes an ellipse having a major axis in the direction of ° (light spot 100a in FIG. 9A (a)) or −45 ° (light spot 100c in FIG. 9A (c)). That is, the direction of the major axis of the light spot changes according to the direction of the positional deviation of the second beam in the optical axis direction.

  FIG. 9A (d) to FIG. 9A (f) show the movement of the light spot in the case of the positional deviation of the condensing point of the second beam relative to the condensing point of the first beam in the radial direction of the disk 38. FIG. 9A (e) shows a case where the condensing points of the two beams coincide with each other, and the light spot 100e has a circular shape in which the intersection point of the two dividing lines 101 and 102 coincides with the center point. On the other hand, when the condensing point of the second beam is displaced in the radial direction of the disk 38, as shown in FIGS. 9A (d) and 9A (f), the light spot is in the negative direction of the X direction ( It moves in the direction of (a light spot 100d in FIG. 9A (d)) or in a positive direction (a light spot 100f in FIG. 9A (f)), that is, depending on the direction of the positional deviation of the second beam in the radial direction. The moving direction of the light spot in the X direction changes.

  9A (g) to 9A (i) show the light spot in the case of the positional deviation in the tangential direction (circumferential direction) of the disc 38 at the condensing point of the second beam with respect to the condensing point of the first beam. Showing movement. FIG. 9A (h) shows a case where the condensing points of the two beams coincide with each other, and the light spot 100h has a circular shape in which the intersection point and the center point of both the dividing lines 101 and 102 coincide. On the other hand, when the condensing point of the second beam is displaced in the tangential direction of the disk 38, as shown in FIGS. 9A (g) and 9A (i), the light spot is in the negative direction of the Y direction ( It moves in the direction of the light spot 100g in FIG. 9A (g) or in the positive direction (light spot 100i in FIG. 9A (i)). That is, the moving direction of the light spot in the Y direction changes according to the direction of the positional deviation of the second beam in the tangential direction.

  In the optical head device, an error signal indicating the positional deviation of the condensing point of the second beam is generated as follows. That is, first, voltage signals output from the light receiving regions 48a to 48d are set to V48a to V48d, respectively. On the other hand, an error signal indicating the positional deviation of the condensing point of the second beam in the optical axis direction is referred to as PEZ, and an error signal indicating the positional deviation of the condensing point of the second beam in the radial direction is referred to as PEX. An error signal representing the positional deviation in the tangential direction of the condensing point of the second beam is PEY. In this case, PEZ is given by the astigmatism method, and PEX and PEY are given by the following equations, respectively, by the push-pull method.

PEZ = (V48a + V48d)-(V48b + V48c)
PEX = (V48a + V48c)-(V48b + V48d)
PEY = (V48a + V48b)-(V48c + V48d)
JP-A-6-274929 JP 2001-160220 A JP 2008-108407 A Toshihiro Horigome, 7 others, “Drive System for Micro-Reflector Recording Employing Blue Laser Diode”, International Symposium on Optical Memory 2006 (ISOM06) ) Technical digest

  However, the movement or change of the light spot in the light receiving unit of the photodetector 46b shown in FIG. 9A is an ideal change, and actually, the movement or change is different. This is because in the optical head device of Non-Patent Document 1, the main surface of the cylindrical lens 47a does not coincide with the front focal plane of the objective lens 45b or a surface optically conjugate with it. For this reason, when the position of the condensing point of the second beam changes, the position of the first beam on the main surface of the cylindrical lens 47a changes. As a result, even if the condensing point of the second beam is displaced only in the radial direction of the disk 38, the light spot is not only in the X direction in the light receiving portion of the photodetector 46b. A phenomenon of moving in the Y direction also occurs. Similarly, even when the condensing point of the second beam is misaligned only in the tangential direction of the disk 38, the light spot is not only in the Y direction but also in the X direction in the photodetector 46b. Also occurs.

  FIG. 9B shows an actual movement or change of the light spot in the light receiving portion of the photodetector 46b when the first beam is shifted on the main surface of the cylindrical lens 47a. In FIG. 9B, the same parts as those in FIG. 9A are denoted by the same reference numerals. First, FIGS. 9B to 9C show changes in the light spot when the condensing point of the second beam is displaced in the optical axis direction. As shown in the figure, in the case of the positional deviation in the optical axis direction, the change is the same as that in FIGS. Next, FIG. 9B (d ′) to (f ′) show the actual movement of the light spot when the condensing point of the second beam is displaced in the radial direction of the disk 38. As shown in the figure, when the condensing point of the second beam is displaced only in the radial direction of the disk 38, the light spot should move only in the X direction (FIG. 9A (d) and FIG. 9). 9A (f)). Actually, since it also moves in the Y direction, the light spot moves in an oblique direction as shown by the arrow (light spot 100d ′ in FIG. 9B (d ′) and FIG. 9B (f ′)). Light spot 100f '). For this reason, when the error signal is calculated by the above equation, PEX is not 0, but PEY, which should be 0, is not 0, so that there is a problem that a correct error signal cannot be generated. Next, FIG. 9B (g ′) to (i ′) show the actual movement of the light spot when the condensing point of the second beam is displaced in the tangential direction of the disk 38. As shown in the figure, when the condensing point of the second beam is displaced only in the tangential direction of the disk 38, the light spot should move only in the Y direction (FIG. 9A (g) and FIG. 9). 9A (i)). Actually, since it also moves in the X direction, the light spot moves in an oblique direction as indicated by an arrow (light spot 100g ′ in FIG. 9B (g ′) and FIG. 9B (i ′)). Light spot 100i '). For this reason, when the error signal is calculated by the above equation, PEY is not 0, but PEX that should be 0 is not 0, so that there is a problem that a correct error signal cannot be generated.

  Thus, in the optical head device of Non-Patent Document 1, when the condensing point of the second beam is displaced in the radial direction and tangential direction of the disk 38, the light spot of the light receiving portion of the photodetector 46b is The positional deviation of the second beam cannot be accurately reflected. For this reason, the optical head device of Non-Patent Document 1 cannot generate an accurate error signal. As a result, there is a problem that the condensing point of the second beam cannot be corrected accurately. This problem is not limited to the optical head device of Non-Patent Document 1, but the main surface of the cylindrical lens that gives astigmatism is the front side of the objective lens for condensing the second beam in the recording layer of the optical recording medium. This is a problem common to an optical head device that does not coincide with a focal plane or a plane optically conjugate with the focal plane.

  Accordingly, in order to solve the above-described problem, the present invention provides an optical head device that focuses the first beam and the second beam at the same focusing point, and accurately shifts the position deviation of the focusing point of the second beam. It is an object of the present invention to provide an optical head device that can be detected and an optical information recording / reproducing device using the same. In order to solve the above-described problem, the present invention provides an optical head device that condenses the first beam and the second beam at the same condensing point. It is an object of the present invention to provide an error signal generation method that can be detected at once, and a condensing position adjustment method using the same.

In order to solve the above-described problems, an optical head device of the present invention includes:
Beam condensing means for condensing the first beam and the second beam at the same condensing point in a state of being opposed to each other;
Astigmatism imparting means for imparting astigmatism to the first beam that has passed through the condensing point;
Photodetection means for detecting the first beam provided with the astigmatism,
The light detection means includes a light receiving unit that receives the light spot of the first beam to which the astigmatism is applied and outputs a signal,
The light receiving unit is
A first dividing line corresponding to a first direction in a plane direction perpendicular to the optical axis of the first beam of the condensing point and intersecting the optical axis of the first beam;
A second dividing line corresponding to a second direction orthogonal to the first direction in the plane direction and intersecting an optical axis of the first beam;
A third dividing line that intersects at an intersection of the first dividing line and the second dividing line and is inclined with respect to the first dividing line; and
Having at least eight light receiving regions that intersect at the intersection of the first dividing line and the second dividing line and that are separated from each other by at least four dividing lines of the fourth dividing line inclined with respect to the second dividing line; It is characterized by.

The optical information recording / reproducing apparatus of the present invention is
The optical head device of the present invention;
Error signal generating means for generating an error signal indicating a positional deviation of the condensing point of the second beam at the condensing point;
The error signal generating means includes
The eight light receiving regions are divided into four light receiving region groups by the first dividing line and the second dividing line, and based on output signals from the four light receiving region groups, the condensing point of the second beam Generate a first error signal that represents the displacement in the optical axis direction,
The eight light receiving regions are divided into two light receiving region groups by the fourth dividing line, and based on the output signals from the two light receiving region groups, the misalignment of the condensing point of the second beam in the first direction. A second error signal representing
The eight light receiving regions are divided into two light receiving region groups by the third dividing line, and based on the output signals from the two light receiving region groups, the misalignment in the second direction of the condensing point of the second beam. A third error signal representing the above is generated.

Furthermore, the error signal generation method of the present invention includes:
Using the optical head device of the present invention,
The eight light receiving regions are divided into four light receiving region groups by the first dividing line and the second dividing line, and based on output signals from the four light receiving region groups, the condensing point of the second beam Generating a first error signal representing a positional shift in the optical axis direction;
The eight light receiving regions are divided into two light receiving region groups by the fourth dividing line, and based on the output signals from the two light receiving region groups, the misalignment of the condensing point of the second beam in the first direction. The eight light receiving regions are divided into two light receiving region groups by the step of generating a second error signal representing the third dividing line and the third dividing line, and based on the output signals from the two light receiving region groups, And a step of generating a third error signal representing a positional deviation of the condensing point in the second direction.

Furthermore, the condensing position adjustment method of the present invention includes:
Based on the error signal generated by the error signal generation method of the present invention, the condensing point of the second beam is moved in at least one of the optical axis direction, the first direction, and the second direction. Thus, the optical head device of the present invention is characterized in that it has a condensing position adjusting step for adjusting the condensing point of the misaligned second beam to the correct position.

  As described above, according to the present invention, even if the light spot of the light receiving unit moves or changes without correctly reflecting the positional deviation of the condensing point of the second beam, It is possible to generate an error signal that correctly reflects the positional deviation of the light spot. As a result, the present invention can accurately detect the positional deviation of the condensing point of the second beam.

  In the present invention, “separated from each other by a dividing line” means that, for example, when adjacent to each other with a constant gap, adjacent to each other without a predetermined gap, one region is interposed therebetween. There are cases where two regions are adjacent to each other. In the present invention, the “third dividing line inclined with respect to the first dividing line” has an inclination angle formed with the first dividing line when there are a plurality of dividing lines inclined with respect to the first dividing line. The smallest dividing line. Similarly, in the present invention, the “fourth dividing line inclined with respect to the second dividing line” is an inclination angle formed with the second dividing line when there are a plurality of dividing lines inclined with respect to the second dividing line. Is the smallest dividing line.

  In the optical head device according to the aspect of the invention, the third dividing line may be formed on the light receiving unit when the second beam condensing point is displaced in the first direction with respect to the first beam condensing point. The fourth dividing line is parallel to the moving direction of the light spot, and the fourth dividing line is the position where the focusing point of the second beam is displaced in the second direction with respect to the focusing point of the first beam. It is preferable to be parallel to the moving direction of the light spot of the light receiving unit.

  In the optical head device of the present invention, it is preferable that the dividing line is a straight line. However, the present invention is not limited to this, and the dividing line may be, for example, a curve, a broken line, a line in which a curve and a straight line are combined, or the like.

  In the light receiving unit of the optical head device of the present invention, the four dividing lines are straight lines, the inclination direction of the third dividing line with respect to the first dividing line is clockwise, and the second dividing line The inclination direction of the fourth dividing line may be counterclockwise. Alternatively, in the light receiving unit of the optical head device of the present invention, the four dividing lines are straight lines, and the inclination direction of the third dividing line with respect to the first dividing line is counterclockwise, and The aspect in which the inclination direction of the fourth dividing line with respect to the second dividing line is clockwise may be employed.

  In the optical head device of the present invention, in order to generate a first error signal indicating a positional deviation of the condensing point of the second beam in the optical axis direction, the first dividing line and the second second light are generated in the light receiving unit. The eight light receiving region is divided into four light receiving region groups by a dividing line, and the light receiving portion is generated for generating a second error signal indicating a positional deviation of the condensing point of the second beam in the first direction. The eight light receiving areas are divided into two light receiving area groups by the fourth dividing line, and a third error signal is generated that indicates a positional deviation of the condensing point of the second beam in the second direction. Therefore, in the light receiving unit, it is preferable that the eight light receiving regions are divided into two light receiving region groups by the third dividing line.

  In the optical head device of the present invention, the condensing point of the second beam may be set in the optical axis direction based on at least one error signal of the first error signal, the second error signal, and the third error signal. It is preferable to have a condensing position adjusting means capable of adjusting the condensing point of the second beam to a correct condensing point by moving in at least one of the first direction and the second direction.

  In the optical head device according to the aspect of the invention, the beam condensing unit may condense the direct light of the first beam and the direct light of the second beam at the condensing point.

  In the optical head device according to the aspect of the invention, the beam condensing unit may condense one direct light and the other reflected light of the first beam and the second beam at the condensing point. .

  In the optical information recording / reproducing apparatus of the present invention, the optical head device is an optical head device including the condensing position adjusting unit, and the condensing position adjusting unit includes the first error signal and the second error signal. And the second beam focusing point is moved in at least one of the optical axis direction, the first direction, and the second direction based on the third error signal. It is preferable to have a condensing position adjusting means driving means for adjusting the light spot to a correct condensing point and driving the condensing position adjusting means.

  The optical information recording / reproducing apparatus of the present invention further includes the condensing point moving means, and the condensing point moving means moves the condensing point in the optical head apparatus of the present invention in the optical axis direction. It is preferable.

  Next, the present invention will be described in detail. However, this invention is not restrict | limited and limited by the following description.

  The optical head device of the present invention is an optical recording medium having a recording layer, and includes the beam condensing unit, the astigmatism applying unit, and the light detecting unit.

  In the optical head device of the present invention, the surface direction perpendicular to the optical axis of the first beam at the condensing point corresponds to the surface direction of the optical recording medium.

  Examples of the optical recording medium include a structure in which a recording layer is disposed between two transparent substrates. In the optical recording medium having this structure, beams are incident from both the front surface and the back surface, and the condensing points of the direct lights of the two beams are made coincident in the recording layer. In addition, in the above-described configuration, an optical recording medium having a configuration in which a reflective layer is disposed on one side of the recording layer is also included. In the optical recording medium having this configuration, one of the two beams is incident from the surface opposite to the reflective layer of the recording layer, and the direct light reaches the reflective layer of the one beam. Before the recording, the light is condensed in the recording layer, and the other beam is reflected by the reflective layer, and then the reflected light is condensed in the recording layer. The two substrates are cover layers. Examples of the substrate include a glass substrate and a resin substrate using a light transmissive resin such as polycarbonate. The recording layer can be formed using, for example, a photopolymer. The recording layer may have a single layer structure or a multi-layer structure corresponding to three-dimensional recording / reproduction. The reflective layer can be formed using aluminum, gold, platinum, or the like. In addition, in the above configuration, a recording medium in which a quarter-wave plate layer is further disposed between the recording layer and the reflective layer to change the polarization direction of the beam can be mentioned. The quarter-wave plate layer can be formed using, for example, a liquid crystal compound, a non-liquid crystal polymer film, or the like. The optical recording medium may be provided with a reference surface for controlling the objective lens by a light source different from the light source for recording and reproduction. The shape of the optical recording medium may be, for example, a disc shape (disc shape) or a card shape (rectangular shape).

  The beam condensing means is for condensing the first beam and the second beam in a state of facing each other at the same condensing point in the recording layer of the optical recording medium having the recording layer. The beam condensing means is, for example, two objective lenses. The beam condensing unit may include, for example, a light source, a beam dividing unit, and a beam separating unit. An example of the light source is a semiconductor laser. The beam splitting means is for splitting light emitted from the light source into a first beam and a second beam. An example of the beam splitting means is a polarizing beam splitter. The beam separating means is for separating the first beam that has passed through the condensing point in the recording layer of the optical recording medium from the second beam. Examples of the beam separating means include a polarizing beam splitter.

  The astigmatism imparting means is for imparting astigmatism to the first beam that has passed through the condensing point. Examples of the astigmatism applying means include a cylindrical lens.

  The light detection means is for detecting the first beam to which the astigmatism is applied. The light detection unit includes a light receiving unit that receives the light spot of the first beam to which the astigmatism is applied and outputs a signal. As described above, the light receiving unit includes at least eight light receiving regions separated from each other by at least four dividing lines of the first dividing line, the second dividing line, the third dividing line, and the fourth dividing line. Have In the optical head device of the present invention, the number of the dividing lines is not particularly limited, and further dividing lines may be set in addition to the four dividing lines. The first dividing line corresponds to a first direction in a plane direction (plane direction of the optical recording medium) perpendicular to the optical axis of the first beam at the condensing point, and intersects the optical axis of the first beam. It is a line to do. The second dividing line corresponds to a second direction orthogonal to the first direction in a surface direction (surface direction of the optical recording medium) perpendicular to the optical axis of the first beam at the condensing point, and the first It is a line that intersects the optical axis of one beam. The third dividing line is a line that intersects at the intersection of the first dividing line and the second dividing line and is inclined with respect to the first dividing line. The fourth dividing line is a line that intersects at the intersection of the first dividing line and the second dividing line and is inclined with respect to the second dividing line. In the present invention, when the optical recording medium is an optical disk (disk), the first direction is a radial direction of the optical disk, and the second direction is a tangential direction (circumferential direction) of the optical disk.

  In the optical head of the present invention, when the position of the condensing point of the second beam is shifted in the first direction relative to the position of the condensing point of the first beam, The first beam moves in a direction inclined with respect to the first dividing line. In the optical head of the present invention, when the position of the condensing point of the second beam is shifted in the second direction relative to the position of the condensing point of the first beam, the light detection is performed. In the light receiving part of the detector, the first beam moves in a direction inclined with respect to the second dividing line. In the present invention, the eight light receiving regions are divided into two light receiving region groups by the fourth dividing line, and based on the output signals of the two light receiving region groups, relative to the condensing point of the first beam. An error signal representing a positional shift in the first direction of the condensing point of the second beam is generated. Further, in the present invention, the eight light receiving regions are divided into two light receiving region groups by the third dividing line, and based on output signals from the two light receiving region groups, An error signal indicating a positional shift in the second direction of the focusing point of the relative second beam is generated. Thereby, when the position of the condensing point of the second beam is shifted in the first direction relative to the position of the condensing point of the first beam, an error indicating a positional deviation in the first direction. Although the signal is not zero, the error signal indicating the positional deviation in the second direction can remain zero. Similarly, when the position of the condensing point of the second beam is shifted in the second direction relative to the position of the condensing point of the first beam, an error indicating a positional deviation in the second direction. Although the signal is not zero, the error signal indicating the positional deviation in the first direction can remain zero. As a result, it is possible to correctly detect a positional deviation of the condensing point of the second beam with respect to the condensing point of the first beam in the first direction or the second direction.

  As described above, the third dividing line is the light spot of the light receiving unit when the condensing point of the second beam is displaced in the first direction with respect to the condensing point of the first beam. It is preferable to be parallel to the moving direction. The fourth dividing line is a moving direction of the light spot of the light receiving unit when the focusing point of the second beam is displaced in the second direction with respect to the focusing point of the first beam. It is preferable that it is parallel to. The parallelism is preferably completely parallel, but may be substantially parallel even if there is a slight deviation. The term “substantially parallel” means that, for example, when the focal point of the second beam is displaced in the first direction, the movement of the light spot in the second direction can be corrected, and the second When the focal point of the beam is displaced in the second direction, it means that the movement of the light spot in the first direction is parallel to the extent that it can be corrected.

  As described above, the inclination direction of the third dividing line with respect to the first dividing line is clockwise, and the inclination direction of the fourth dividing line with respect to the second dividing line is counterclockwise. An aspect may be sufficient (1st aspect). Alternatively, the inclination direction of the third dividing line with respect to the first dividing line may be counterclockwise, and the inclination direction of the fourth dividing line with respect to the second dividing line may be clockwise. (Second embodiment). The first aspect and the second aspect can be appropriately selected depending on the direction of positional deviation of the light spot. In addition, the inclination angle of the third dividing line with respect to the first dividing line and the inclination angle of the fourth dividing line with respect to the second dividing line are not particularly limited.

  According to the present invention, the main surface of the cylindrical lens for providing astigmatism is optically conjugate with the front focal plane of the objective lens for condensing the second beam in the recording layer of the optical recording medium, or with it. The present invention is applied to an optical head device that does not coincide with the surface. Further, the present invention is preferably applied to a recording method for recording information in three dimensions in the plane direction and the thickness direction in the recording layer of the optical recording medium, but is not limited to this, and is two-dimensional only in the plane direction. And may be applied to a recording method for recording information. When applied to a recording method for recording information in three dimensions in the plane direction and thickness direction, as described above, the optical information recording / reproducing apparatus of the present invention has the condensing point moving means, and the condensing point. The moving means preferably moves the condensing point in the optical head device of the present invention in the optical axis direction.

  Next, embodiments of the present invention will be described with reference to the drawings. However, the following embodiment is an exemplification, and the present invention is not limited or limited by the following embodiment.

[Embodiment 1]
FIG. 1 shows a part of the configuration of the optical head device of this embodiment and the configuration of the optical information recording / reproducing device. In the drawing, a portion 1a (excluding the disc 2a) surrounded by a dotted frame is the optical head device of the present embodiment. In the same figure, a block diagram showing a part of the configuration of an optical information recording / reproducing apparatus including the optical head device is shown in a portion outside the dotted line. As shown in the figure, the optical head of this embodiment includes a laser 3a, seven convex lenses 4a, 4b, 4c, 4d, 4e, 4f, and 4g, two half-wave plates 5a, 5b, and 3 Polarization beam splitters 6a, 6b, 6c, five mirrors 8a, 8b, 8c, 8d, 8e, one shutter 9a, two quarter-wave plates 10a, 10b, two The objective lens 11a, 11b, two photodetectors 12a, 12b, one cylindrical lens 13a, and one objective lens actuator 49a are included. A semiconductor laser can be used as the laser 3a. The wavelength of the beam emitted from the laser 3a is, for example, 405 nm. In the optical head device of the present embodiment, the objective lenses 11a and 11b are the beam condensing means, the polarizing beam splitter 6a is the beam dividing means, the polarizing beam splitter 6c is the beam separating means, and the cylindrical lens 13a. Is the astigmatism applying means, the photodetector 12b is the light detecting means for generating the error signal, and the objective lens actuator 49a is the condensing position correcting means. In the present embodiment, one relay lens system is formed by the two convex lenses 4b and 4c, and another relay lens system is formed by the two convex lenses 4d and 4e. The cylindrical lens 13a and the convex lens 4g constitute an anamorphic lens system. The photodetector 12b is arranged in the middle of two focal lines formed by the anamorphic lens system. In the present embodiment, the cylindrical lens 13a, the convex lens 4g, and the photodetector 12b form a condensing point position shift detection mechanism. The arrangement position of the half-wave plate 5b is not particularly limited, and may be arranged anywhere in the optical path between the polarizing beam splitter 6a and the polarizing beam splitter 6b. For example, the polarizing beam splitter 6a and the mirror 8a (Fig. 1) or in the optical path between the mirror 8a and the polarizing beam splitter 6b. The arrangement position of the quarter wavelength plate 10a is not particularly limited, and may be arranged anywhere in the optical path between the convex lens 4c and the objective lens 11a. For example, the optical path between the mirror 8d and the objective lens 11a. Of these, the optical path between the convex lens 4c and the mirror 8d may be used (FIG. 1). The arrangement position of the quarter wavelength plate 10b is not particularly limited, and may be arranged anywhere in the optical path between the convex lens 4e and the objective lens 11b. For example, the optical path between the mirror 8e and the objective lens 11b. Of these, the optical path between the convex lens 4e and the mirror 8e may be used (FIG. 1). The arrangement position of the shutter 9a is not particularly limited, and may be arranged anywhere in the optical path between the polarizing beam splitter 6a and the disk 2a. For example, the shutter 9a is arranged in the optical path between the mirror 8b and the mirror 8c. Alternatively, it may be arranged in the optical path between the polarizing beam splitter 6a and the mirror 8b (FIG. 1). The condensing point moving means can be constituted by an objective lens actuator (not shown) of the objective lens 11a and an objective lens actuator 49b of the objective lens 11b.

  In the optical head device of the present embodiment, the beam emitted from the laser 3a is split into reflected light and transmitted light by the polarization beam splitter 6a. In the present embodiment, the reflected light is the “first beam”, and the transmitted light is the “second beam”. In the present embodiment, in the case of information recording, the second beam passes through the shutter 9a. In the case of information reproduction, the second beam is blocked from traveling by the shutter 9a. In the case of information recording, recording data is converted into a laser driving signal by the modulation circuit 26a, the recording signal generation circuit 27a, and the laser driving circuit 28a. The laser 3a converts the recording data into an optical signal (laser beam) by the laser driving signal. On the other hand, in the case of information reproduction, a constant laser drive signal is input to the laser from the laser drive circuit 28a.

  In the optical head device and the optical information recording / reproducing apparatus of the present embodiment, information is recorded and reproduced, for example, as follows.

  First, the beam emitted from the laser 3a passes through the convex lens 4a and is converted from divergent light to parallel light. The parallel light passes through the half-wave plate 5a, and as a result, the polarized light is polarized in a direction of 45 ° with respect to the paper surface. About 50% of the polarized light is reflected by the polarization beam splitter 6a as the S-polarized component and becomes the first beam, and about 50% is transmitted as the P-polarized component and becomes the second beam.

  When recording information on the disc 2a, the shutter 9a is opened to allow the second beam to pass. Information is recorded on the disk 2a by the first beam and the second beam as follows. That is, first, the first beam passes through the half-wave plate 5b, changes its polarization direction by 90 °, is reflected by the mirror 8a, and enters the polarization beam splitter 6b as P-polarized light. The incident first beam passes through the polarization beam splitter 6b at almost 100%, passes through the relay lens system (convex lenses 4b, 4c) in the order of 4b → 4c, and becomes parallel light again. The first beam that has become parallel light is reflected by the mirror 8d, passes through the quarter-wave plate 10a, and is converted from linearly polarized light to circularly polarized light. The circularly polarized first beam passes through the objective lens 11a, is converted from parallel light into convergent light, and is condensed in the recording layer of the disk 2a. On the other hand, the second beam is reflected by the mirror 8b, passes through the shutter 9a, is reflected by the mirror 8c, and further enters the polarization beam splitter 6c as P-polarized light. The incident second beam passes through the polarization beam splitter 6c at almost 100%, passes through the relay lens system (convex lenses 4d, 4e) in the order of 4d → 4e, and becomes parallel light again. The second beam that has become parallel light is reflected by the mirror 8e, passes through the quarter-wave plate 10b, and is converted from linearly polarized light to circularly polarized light. The circularly polarized second beam passes through the objective lens 11b, is converted from parallel light into convergent light, and is condensed in the recording layer of the disk 2a from the side opposite to the first beam. In this way, the first beam and the second beam are condensed at the same position in the recording layer of the disk 2a. At the condensing point, the first beam and the second beam interfere with each other to form a minute diffraction grating. The diffraction grating formed on the recording layer becomes recorded information.

  After the condensing, the first beam is transmitted through the recording layer of the disk 2a, is transmitted through the objective lens 11b from the opposite direction to the second beam, and is converted from divergent light into parallel light. The first beam that has become parallel light passes through the quarter-wave plate 10b, is converted from circularly polarized light to linearly polarized light, is reflected by the mirror 8e, and passes through the relay lens system (convex lenses 4e, 4d) from 4e to 4d. It is transmitted in order and becomes parallel light again. The first beam that has become parallel light enters the polarization beam splitter 6c as S-polarized light. The first beam of S-polarized light is almost 100% reflected by the light beam splitter 6c and passes through the anamorphic lens system composed of the cylindrical lens 13a and the convex lens 4g in the order of 13a → 4g. The first beam transmitted through the anamorphic lens system is given astigmatism by the cylindrical lens 13a and is converted from parallel light to convergent light by the convex lens 4g. The first beam given astigmatism is received by the photodetector 12b. In the photodetector 12b, the optical signal of the first beam given astigmatism is changed into an electric signal, and the electric signal is amplified and amplified by an amplifying circuit 32a disposed outside the optical head device. Based on the electrical signal thus generated, an error signal is generated by the error signal generation circuit 33a. Based on the error signal, the objective lens drive circuit 34 operates the objective lens actuator 49a to adjust the inclination of the objective lens 11b.

  On the other hand, when reproducing information from the disk 2a, the shutter 9a is closed to block the progress of the second beam to the disk 2a.

  The first beam reaches the inside of the recording layer of the disk 2a through the same path as that during the information recording and is condensed. At the time of information reproduction, the condensed first beam is reflected by the diffraction grating formed in the recording layer of the disk 2a. The reflected first beam passes through the objective lens 11a in the opposite direction to the above and is converted from divergent light into parallel light. The first beam that has become parallel light passes through the quarter-wave plate 10a, is converted from circularly polarized light into linearly polarized light, and is reflected by the mirror 8d. The reflected first beam passes through the relay lens system (convex lenses 4c, 4b) in the order of 4c → 4b and becomes parallel light again. The first beam that has become parallel light enters the polarization beam splitter 6b as S-polarized light. Nearly 100% of the incident first beam is reflected by the polarization beam splitter 6b, passes through the convex lens 4f, is converted from parallel light into convergent light, and is received by the photodetector 12a. The output signal from the photodetector 12a is amplified by the amplifier circuit 29a, then processed by the reproduction signal processing circuit 30a and the demodulation circuit 31a, and converted into reproduction data.

  FIG. 2 shows the state of the first beam and the second beam with respect to the disk 2a during information recording / reproduction. FIG. 2A is a diagram illustrating an incident state during information recording, and FIG. 2B is a diagram illustrating a reflection state during information reproduction. In FIG. 2, the same parts as those in FIG. First, as shown in FIG. 2A, during information recording, direct light of the first beam 20a is incident on the disk 2a from one side of the disk 2a (upward in the figure), and the other side of the disk 2a ( Direct light of the second beam 20b enters the disk 2a from the lower side in FIG. The disc 2a has a structure in which a recording layer 14a is disposed between two substrates 17a and 17b. The direct light of the first beam 20a and the direct light of the second beam 20b are condensed at the condensing point 18a at the same position in the recording layer 14a. A minute diffraction grating is formed at the condensing point. On the other hand, as shown in FIG. 2B, at the time of reproducing information, the first beam is incident on the recording layer 14a of the disk 2a as described above. The incident first beam is reflected by a minute diffraction grating 19a (shown by a black circle in the figure) formed in the recording layer 14a, and is emitted to the outside of the disk 2a as reflected light 20c. The diffraction grating 19a has bit data information. At the time of information recording, the positions of the condensing points of the first beam and the second beam are three-dimensionally moved in the surface direction and the thickness direction of the recording layer 14a to form the diffraction grating 19a. Information can be recorded three-dimensionally on the recording layer 14a. At the time of information reproduction, information can be reproduced from the reflected light of the diffraction grating 19a formed three-dimensionally in the recording layer 14a.

  FIG. 3A shows the pattern of the light receiving part of the photodetector 12b in this embodiment and the light spot of the light receiving part. In the figure, the X direction is a direction corresponding to the radial direction of the disk 2a (the first direction), and the Y direction is a direction corresponding to the tangential direction (circumferential direction: the second direction) of the disk 2a. Yes, the Z direction (the direction perpendicular to the paper surface in the figure) is a direction corresponding to the optical axis direction. 3A (a) to 3 (i) show the pattern of the light receiving section. As shown in the figure, in the light receiving unit, a dividing line parallel to the X direction is the first dividing line 101, and a dividing line parallel to the Y direction is the second dividing line 102. In the light receiving unit, a line inclined clockwise with respect to the first dividing line 101 is the third dividing line 103, and a line inclined counterclockwise with respect to the second dividing line 102 is the fourth dividing line. Line 104. The third dividing line 103 is in the moving direction of the light spot of the light receiving unit when the focusing point of the second beam is displaced in the first direction with respect to the focusing point of the first beam. Parallel. In addition, the fourth dividing line 104 moves the light spot of the light receiving unit when the condensing point of the second beam is displaced in the second direction with respect to the condensing point of the first beam. Parallel to the direction. In the figure, dotted circles or ellipses indicated by 100a to 100i indicate light spots. The light receiving unit includes eight light receiving regions 21a to 21h separated from each other by the four dividing lines 101, 102, 103, and 104.

FIGS. 3A (a) to 3A (c) show changes in the light spot in the case of a positional shift in the optical axis direction of the condensing point of the second beam with respect to the condensing point of the first beam. FIG. 3A (b) shows a case where the condensing points of the two beams coincide with each other, and the light spot 100b has a circular shape in which the intersection point and the center point of both the dividing lines 101 and 102 coincide. On the other hand, when the condensing point of the second beam is displaced in the optical axis direction, as shown in FIGS. 3A (a) and 3A (c), the light spot is rotated +45 clockwise with respect to the X direction. It becomes an ellipse having a major axis in the direction of ° (light spot 100a in FIG. 3A (a)) or −45 ° (light spot 100c in FIG. 3A (c)). When detecting the positional deviation in the optical axis direction of the condensing point of the second beam, the eight light receiving areas 21a to 21g are shown below by the first dividing line 101 and the second dividing line 102. Divide into light receiving areas.
First light receiving area group: 21a
Second light receiving area group: 21e + 21b + 21f
Third light receiving area group: 21d
Fourth light receiving region group: 21h + 21c + 21g

FIG. 3A (d) to FIG. 3A (f) show the movement of the light spot in the case of the positional deviation in the radial direction of the disk 38 from the condensing point of the second beam with respect to the condensing point of the first beam. FIG. 3A (e) shows a case where the condensing points of the two beams coincide with each other, and the light spot 100e has a circular shape in which the intersection point of the two dividing lines 101 and 102 coincides with the center point. On the other hand, when the condensing point of the second beam is displaced in the radial direction of the disk 38, the light spot is not only in the X direction but also in the Y direction as shown in FIGS. 3A (d) and 3A (f). In order to move, the light spot moves in an oblique direction (a direction inclined clockwise with respect to the first dividing line) (light spot 100d in FIG. 3A (d) and light spot 100f in FIG. 3A (f)). When detecting the radial position shift of the condensing point of the second beam, the eight light receiving regions 21a to 21g are divided into the following two light receiving region groups by the fourth dividing line 104.
First light receiving region group: 21a + 21c + 21e + 21g
Second light receiving area group: 21b + 21d + 21f + 21h

FIG. 3A (g) to FIG. 3A (i) show the movement of the light spot in the case of the positional deviation in the tangential direction of the disc 38 of the condensing point of the second beam with respect to the condensing point of the first beam. FIG. 3A (h) shows a case where the condensing points of the two beams coincide with each other, and the light spot 100h has a circular shape in which the intersection point of the two dividing lines 101 and 102 coincides with the center point. On the other hand, when the condensing point of the second beam is displaced in the tangential direction of the disk 38, as shown in FIGS. 3A (g) and 3A (i), the light spot is not only in the Y direction but also in the X direction. In order to move, the light spot moves in an oblique direction (a direction tilted counterclockwise with respect to the second dividing line) (light spot 100d in FIG. 3A (g) and light spot 100f in FIG. 3A (i)). When detecting the positional deviation in the tangential direction of the condensing point of the second beam, the eight light receiving regions 21a to 21g are divided into two light receiving region groups described below by the third dividing line 103.
First output area: 21a + 21b + 21e + 21g
Second output area: 21c + 21d + 21f + 21h

  Here, the voltage signals output from the light receiving regions 21a to 21g are represented by V21a to V21g, respectively. In this case, if the error signal indicating the positional deviation of the condensing point of the second beam in the optical axis direction is PEZ, PEZ can be expressed by the following equation by the astigmatism method. Further, if the positional deviations in the radial direction and the tangential direction of the disk 2a at the condensing point of the second beam are PEX and PEY, respectively, PEX and PEY are given by the following formulas by the push-pull method.

PEZ = (V21a + V21d)-(V21b + V21c + V21e + V21f +
V21g + V21h)
PEX = (V21a + V21c + V21e + V21g)-(V21b + V21d +
V21f + V21h)
PEY = (V21a + V21b + V21e + V21g) − (V21c + V21d +
V21f + V21h)

  FIG. 3B shows another pattern of the light receiving portion of the photodetector 12b in this embodiment and a light spot of the light receiving portion. In the figure, the X direction is a direction corresponding to the radial direction of the disk 2a (the first direction), and the Y direction is a direction corresponding to the tangential direction (circumferential direction: the second direction) of the disk 2a. Yes, the Z direction (the direction perpendicular to the paper surface in the figure) is a direction corresponding to the optical axis direction. 3B (a) to 3 (i) show patterns of the light receiving portions. As shown in the figure, in the light receiving section, a dividing line parallel to the X direction is the first dividing line 101, and a dividing line 102 parallel to the Y direction is the second dividing line. In the light receiving portion, the line inclined counterclockwise with respect to the first dividing line 101 is the third dividing line 103, and the line inclined clockwise with respect to the second dividing line 102 is the fourth dividing line. Line 104. The third dividing line 103 is in the moving direction of the light spot of the light receiving unit when the focusing point of the second beam is displaced in the first direction with respect to the focusing point of the first beam. Parallel. In addition, the fourth dividing line 104 moves the light spot of the light receiving unit when the condensing point of the second beam is displaced in the second direction with respect to the condensing point of the first beam. Parallel to the direction. In the figure, dotted circles or ellipses 100a to 100i indicate light spots. The light receiving unit has eight light receiving regions 21a to 21h separated from each other by the four dividing lines 101, 102, 103, and 104.

FIGS. 3B (a) to 3B (c) show changes in the light spot in the case of a positional shift in the optical axis direction of the condensing point of the second beam with respect to the condensing point of the first beam. FIG. 3B (b) shows a case where the condensing points of the two beams coincide with each other, and the light spot 100b has a circular shape in which the intersection point and the center point of both the dividing lines 101 and 102 coincide. On the other hand, when the condensing point of the second beam is displaced in the optical axis direction, as shown in FIG. 3B (a) and FIG. 3B (c), the light spot is +45 in the clockwise direction with respect to the X direction. It becomes an ellipse having a major axis in the direction of ° (light spot 100a in FIG. 3B (a)) or −45 ° (light spot 100c in FIG. 3B (c)). When detecting the positional deviation of the condensing point of the second beam in the optical axis direction, the eight light receiving regions 21a to 21g are shown below by the first dividing line 101 and the second dividing line 102. Divide into area groups.
First light receiving area group: 21a + 21e + 21g
Second light receiving area group: 21b
Third light receiving region group: 21d + 21f + 21h
Fourth light receiving region group: 21c

FIG. 3B (d) to FIG. 3B (f) show the movement of the light spot in the case of the positional deviation in the radial direction of the disc 38 of the condensing point of the second beam with respect to the condensing point of the first beam. FIG. 3B (e) shows a case where the condensing points of the two beams coincide with each other, and the light spot 100e has a circular shape in which the intersection point and the center point of the dividing lines 101 and 102 coincide. On the other hand, when the condensing point of the second beam is displaced in the radial direction of the disk 38, the light spot is not only in the X direction but also in the Y direction as shown in FIGS. 3B (d) and 3B (f). In order to move, the light spot moves in an oblique direction (a direction inclined counterclockwise with respect to the first dividing line) (light spot 100d in FIG. 3B (d) and light spot 100f in FIG. 3B (f)). When detecting the radial position shift of the condensing point of the second beam, the eight light receiving areas 21a to 21g are divided into the following two light receiving area groups by the fourth dividing line 104.
First light receiving region group: 21a + 21c + 21g + 21h
Second light receiving area group: 21b + 21d + 21e + 21f

FIG. 3B (g) to FIG. 3B (i) show the movement of the light spot in the case of the positional deviation in the tangential direction of the disc 38 at the focusing point of the second beam with respect to the focusing point of the first beam. FIG. 3B (h) shows a case where the condensing points of the two beams coincide with each other, and the light spot 100h has a circular shape in which the intersection point and the center point of the dividing lines 101 and 102 coincide. On the other hand, when the condensing point of the second beam is displaced in the tangential direction of the disk 38, the light spot is not only in the Y direction but also in the X direction, as shown in FIGS. 3B (g) and 3B (i). In order to move, the light spot moves in an oblique direction (a direction inclined clockwise with respect to the second dividing line) (light spot 100g in FIG. 3B (g) and light spot 100i in FIG. 3B (i)). When detecting the positional deviation in the tangential direction of the condensing point of the second beam, the eight light receiving regions 21a to 21g are divided into two light receiving region groups described below by the third dividing line 103.
First light receiving region group: 21a + 21b + 21e + 21f
Second light receiving area group: 21c + 21d + 21g + 21h

  Here, the voltage signals output from the light receiving regions 21a to 21g are represented by V21a to V21g, respectively. In this case, assuming that the error signal representing the positional deviation of the condensing point of the second beam in the optical axis direction and PEZ, PEZ can be expressed by the following equation by the astigmatism method. Further, if the positional deviations in the radial direction and the tangential direction of the disk 2a at the condensing point of the second beam are PEX and PEY, respectively, PEX and PEY are given by the following formulas by the push-pull method.

PEZ = (V21a + V21d + V21e + V21f + V21g + V21h) −
(V21b + V21c)
PEX = (V21a + V21c + V21g + V21h)-(V21b + V21d +
V21e + V21f)
PEY = (V21a + V21b + V21e + V21f)-(V21c + V21d +
V21g + V21h)

  In the present embodiment, since the main surface of the cylindrical lens 13a does not coincide with the front focal plane of the objective lens 11b or a surface optically conjugate with it, the position of the condensing point of the second beam is the radius of the disk 2a. When changing in the direction and tangential direction, the position of the first beam on the main surface of the cylindrical lens 13a changes. For this reason, in the light receiving portion, the light spot moves in an oblique direction. In the present embodiment, as described above, the third dividing line inclined in the oblique direction in accordance with the movement of the light spot in the oblique direction. 103 and the fourth dividing line 104 are used to generate an error signal PEX and an error signal PEY. Thereby, when the position of the condensing point of the second beam is shifted in the radial direction of the disk 2a with respect to the position of the condensing point of the first beam, PEX is not 0 but PEY remains 0. can do. Similarly, when the position of the condensing point of the second beam is shifted in the tangential direction of the disk 2a with respect to the position of the condensing point of the first beam, PEY is not 0 but PEX remains 0. can do. As a result, it is possible to correctly detect the positional deviation in the radial direction and the tangential direction of the disc 2a at the condensing point of the second beam.

  The block diagram of FIG. 4 shows the configuration of the optical information recording / reproducing apparatus of the present embodiment. In this figure, the same parts as those in FIGS. 1, 2, 3A and 3B are denoted by the same reference numerals. As shown in the figure, the optical head device 1a is mounted on a positioner 22a, and the disk 2a is mounted on a spindle 23a. Shutter drive circuit 25a, circuit from modulation circuit 26a to laser drive circuit 28a, circuit from amplifier circuit 29a to demodulation circuit 31a, circuit from amplifier circuit 32a to objective lens drive circuit 34, positioner drive circuit 36a and spindle drive circuit 37a Is controlled by the controller 24a.

  The shutter drive circuit 25a drives a shutter 9a in the optical head device 1a by supplying a current to a motor (not shown). By the shutter drive circuit 25a, the shutter 9a allows the optical head device 1a to pass the second beam during information recording, and blocks the progress of the second beam during information reproduction.

  The modulation circuit 26a modulates a signal input from the outside as recording data according to a modulation rule when information is recorded on the disk 2a. The recording signal generation circuit 27a generates a recording signal for driving the laser 3a in the optical head device 1a based on the signal modulated by the modulation circuit 26a. When recording information on the disk 2a, the laser drive circuit 28a drives the laser 3a by supplying a current corresponding to the recording signal to the laser 3a based on the recording signal generated by the recording signal generation circuit 27a. Further, the laser driving circuit 28a drives the laser 3a by supplying a constant current to the laser 3a so that the power of the light emitted from the laser 3a is constant when reproducing information from the disk 2a.

  The amplifier circuit 29a amplifies the voltage signal output from the photodetector 12a in the optical head device 1a when reproducing information from the disk 2a. The reproduction signal processing circuit 30a performs generation, waveform equalization, and binarization of a reproduction signal recorded in the form of a diffraction grating on the disk 2a based on the voltage signal amplified by the amplifier circuit 29a. The demodulating circuit 31a demodulates the signal binarized by the reproduction signal processing circuit 30a in accordance with a demodulation rule, and outputs it as reproduction data to the outside.

  The amplifier circuit 32a amplifies a voltage signal output from the photodetector 12b in the optical head device 1a when information is recorded on the disk 2a. The error signal generation circuit 33a generates error signals Pez, PEX and PEY for driving the objective lens 11b in the optical head device 1a based on the voltage signal amplified by the amplification circuit 32a. The objective lens drive circuit 34 supplies current to the actuator 49a (see FIG. 1) so that the error signals Pez, PEX, and PEY become 0 based on the error signals Pez, PEX, and PEY generated by the error signal generation circuit 33a. And the objective lens 11b is driven in the optical axis direction, the radial direction of the disk 2a, and the tangential direction of the disk 2a. The objective lens driving circuit 34 is a condensing position changing means driving circuit. As a result, in the optical head device 1a, the condensing points of the first beam and the second beam condensed in the recording layer of the disk 2a can be matched.

  The positioner driving circuit 36a supplies current to a motor (not shown) to drive the positioner 22a to move the optical head device 1a in the radial direction of the disk 2a. As a result, when the information is recorded on the disk 2a and when the information is reproduced from the disk 2a, the condensing point of the first beam and the condensing point of the second beam in the optical head device 1a are set as the condensing points of the disk 2a It can move in the radial direction.

  The spindle drive circuit 37a is for rotating the disk 2a by supplying a current to a motor (not shown) to drive the spindle. As a result, when the information is recorded on the disk 2a and when the information is reproduced from the disk 2a, the condensing point of the first beam and the condensing point of the second beam in the optical head device 1a are set as the condensing points of the disk 2a It becomes relatively movable in the tangential direction.

  In the present embodiment, similarly to the optical head device described in Non-Patent Document 1, a reference surface having a track is provided on the disk 2a, and a second laser and a third photodetector are provided in the optical head device 1a. Can be provided. The beam emitted from the second laser is condensed on the track of the reference surface of the disk 2a by the objective lens 11a in the optical head device 1a. After focusing, the beam reflected by the track is received by the third photodetector. Based on the output from the third photodetector, a focus error signal indicating a positional shift in the optical axis direction of the focal point of the objective lens 11a with respect to the track and a track error signal indicating a positional shift in the radial direction of the disk 2a are generated. Is done.

  In the above case, the optical information recording / reproducing apparatus of the present embodiment can be provided with a second laser drive circuit, a third amplifier circuit, a second error signal generation circuit, and a second objective lens drive circuit.

  The second laser driving circuit supplies a constant current so that the power of the emitted light is constant when recording information on the disk 2a and reproducing information from the disk 2a. Drive. The third amplifier circuit amplifies a voltage signal output from the third photodetector when recording information on the disk 2a and reproducing information from the disk 2a. The second error signal generation circuit generates a focus error signal and a track error signal for driving the objective lens 11a based on the voltage signal amplified by the third amplifier circuit. Based on the focus error signal and the track error signal generated by the second error signal generation circuit, the second objective lens drive circuit has the focus error signal and the track error signal become 0 and is emitted from the second laser. The objective lens 11a is driven in the optical axis direction and the radial direction of the disk 2a by supplying an electric current to the actuator so that the focused beam is condensed on the track of the reference surface of the disk 2a. Instead of driving the objective lens 11a by the actuator, a variable focus lens and an optical deflection element may be employed. The variable focus lens is a lens capable of changing a focal length according to an applied voltage. The optical deflection element is an element that can change a deflection angle in accordance with an applied voltage. The variable focus lens and the optical deflection element can be disposed in the optical path of the first beam from the polarization beam splitter 6a of the optical head device 1a to the disk 2a.

  In the present embodiment, the variable focus lens and the light deflection element may be employed in place of the actuator 49a as the condensing position adjusting means for adjusting the condensing point of the second beam in the optical head device 1a. . The variable focus lens and the optical deflection element can be disposed in the optical path of the second beam from the polarization beam splitter 6a of the optical head device 1a to the disk 2a.

[Embodiment 2]
FIG. 5 shows a part of the configuration of the optical head device of this embodiment and the configuration of the optical information recording / reproducing device. In the drawing, a portion 1b (excluding the disc 2b) surrounded by a dotted frame is the optical head device of this embodiment. In the same figure, a block diagram showing a part of the configuration of an optical information recording / reproducing apparatus including the optical head device is shown in a portion outside the dotted line. As shown in the drawing, the optical head of the present embodiment includes a laser 3b, seven convex lenses 4h, 4i, 4j, 4k, 4m, 4n, and 4p, one half-wave plate 5c, and two Polarizing beam splitters 6d and 6e, two half mirrors 7a and 7b, two mirrors 8f and 8g, one shutter 9b, one objective lens 11c, two photodetectors 12c, 12d, one cylindrical lens 13b, and one relay lens actuator 49b. A semiconductor laser can be used as the laser 3b. The wavelength of the beam emitted from the laser 3b is, for example, 405 nm. In the optical head device of the present embodiment, the objective lens 11c is the beam condensing unit, the polarizing beam splitter 6d is the beam dividing unit, the polarizing beam splitter 6e is the beam separating unit, and the cylindrical lens 13b is The astigmatism applying means, the photodetector 12d is an optical detecting means for generating the error signal, and the relay lens actuator 49b is the condensing position correcting means. In the present embodiment, one relay lens system is formed by the two convex lenses 4i and 4j, and another relay lens system is formed by the two convex lenses 4m and 4k. In the present embodiment, a condensing point position shift detection mechanism is formed by the cylindrical lens 13b, the convex lens 4p, and the photodetector 12d. The arrangement position of the shutter 9b is not particularly limited, and may be arranged anywhere in the optical path between the polarizing beam splitter 6d and the polarizing beam splitter 6e. For example, the position between the polarizing beam splitter 6d and the half mirror 7b is acceptable. You may arrange | position in an optical path (FIG. 5), and may arrange | position in the optical path between the half mirror 7b and the mirror 8g. The condensing point moving means includes a relay lens actuator (not shown) of a relay lens system formed by convex lenses 4i and 4j and a relay lens actuator 49b of a relay lens system formed by convex lenses 4m and 4k. Is possible.

  In the optical head device of the present embodiment, the beam emitted from the laser 3b is split into reflected light and transmitted light by the polarization beam splitter 6d. In the present embodiment, the transmitted light is the “first beam”, and the reflected light is the “second beam”. In this embodiment, in the case of information recording, the second beam passes through the shutter 9b. In the case of information reproduction, the second beam is blocked from traveling by the shutter 9b. In the case of information recording, recording data is converted into a laser driving signal by the modulation circuit 26b, the recording signal generation circuit 27b, and the laser driving circuit 28b. The laser 3b converts the recording data into an optical signal (laser beam) by the laser driving signal. On the other hand, in the case of information reproduction, a constant laser drive signal is input to the laser from the laser drive circuit 28b.

  In the optical head device and the optical information recording / reproducing apparatus of the present embodiment, information is recorded and reproduced, for example, as follows.

  First, the beam emitted from the laser 3b passes through the convex lens 4h and is converted from divergent light into parallel light. The parallel light passes through the half-wave plate 5c, and as a result, the polarized light is polarized in a direction of 45 ° with respect to the paper surface. About 50% of the polarized light is transmitted through the polarizing beam splitter 6d as the P-polarized component and becomes the first beam, and about 50% is reflected as the S-polarized component and becomes the second beam.

  When recording information on the disc 2b, the shutter 9b is opened to allow the second beam to pass through. Information is recorded on the disk 2b by the first beam and the second beam as follows. That is, first, about 50% of the first beam passes through the half mirror 7a, is reflected by the mirror 8f, passes through the relay lens system (convex lenses 4i, 4j) in the order of 4i → 4j, and is weakly focused. Become. The first beam that has become weakly converged light enters the polarization beam splitter 6e as P-polarized light. The first beam of P-polarized light is almost 100% transmitted through the polarizing beam splitter 6e, is transmitted through the objective lens 11c, is converted from weakly convergent light to convergent light, and is condensed directly into the recording layer of the disk 2b. Is done. On the other hand, the second beam passes through the shutter 9b, about 50% passes through the half mirror 7b, is reflected by the mirror 8g, and passes through the relay lens system (convex lenses 4k, 4m) in the order of 4k → 4m. It becomes weak divergent light. The second beam that has become weakly divergent light enters the polarization beam splitter 6e as S-polarized light. The second beam of S-polarized light is almost 100% reflected by the polarizing beam splitter 6e, passes through the objective lens 11c, and is converted from weak divergent light to convergent light. The second beam that has become converged light is once transmitted through the recording layer of the disk 2b, reflected by the reflective layer of the disk 2b, and condensed as reflected light in the recording layer. In this way, the first beam and the second beam are condensed at the same position in the recording layer of the disk 2b. At the condensing point, the first beam and the second beam interfere with each other to form a minute diffraction grating. The diffraction grating formed in the recording layer becomes recorded information.

  After the condensing, the first beam is reflected by the reflecting layer of the disk 2b, passes through the recording layer, passes through the objective lens 11c from the opposite direction to the condensing on the recording layer, and is weakly converged from the diverging light. Converted to light. The first beam that has become weakly converged light enters the polarization beam splitter 6e as S-polarized light. The first beam of S-polarized light is almost 100% reflected by the light beam splitter 6e and passes through the relay lens system (convex lenses 4m, 4k) in the order of 4m → 4k to become parallel light. The first beam that has become parallel light is reflected by the mirror 8g, about 50% is reflected by the half mirror 7b, and passes through an anamorphic lens system composed of the cylindrical lens 13b and the convex lens 4p in the order of 13b → 4p. To do. The first beam transmitted through the anamorphic lens system is given astigmatism by the cylindrical lens 13b and is converted from parallel light to convergent light by the convex lens 4p. The first beam given astigmatism is received by the photodetector 12d. In the photodetector 12d, the optical signal of the first beam given astigmatism is changed into an electrical signal, and the electrical signal is amplified and amplified by an amplification circuit 32b disposed outside the optical head device. Based on the electrical signal thus generated, an error signal is generated by the error signal generation circuit 33b. Based on the error signal, the relay lens driving circuit 35 operates the relay lens actuator 49b to adjust the inclination of any one of the convex lenses 4m and 4k.

  On the other hand, when reproducing information from the disk 2b, the shutter 9b is closed to prevent the second beam from traveling to the disk 2b.

  The first beam reaches the inside of the recording layer of the disk 2b through the same path as that during the information recording and is condensed. At the time of information reproduction, the condensed first beam is reflected by the diffraction grating formed in the recording layer of the disk 2b. The reflected first beam passes through the objective lens 11c in the opposite direction to the above and is converted from divergent light to weak divergent light. The first beam that has become weakly divergent light enters the polarization beam splitter 6e as P-polarized light. The first beam of P-polarized light is almost 100% transmitted through the polarizing beam splitter 6e, and transmitted through the relay lens system (convex lenses 4j, 4i) in the order of 4j → 4i to become parallel light. The first beam that has become parallel light is reflected by the mirror 8f, about 50% is reflected by the half mirror 7a, passes through the convex lens 4n, is converted into convergent light, and is received by the photodetector 12c. The output signal from the photodetector 12c is amplified by the amplifier circuit 29b, then processed by the reproduction signal processing circuit 30b and the demodulation circuit 31b, and converted into reproduction data.

  FIG. 6 shows a state of incidence of the first beam and the second beam on the disk 2b during information recording / reproduction. FIG. 6A is a diagram illustrating an incident state during information recording, and FIG. 6B is a diagram illustrating an incident state during information reproduction. In FIG. 6, the same parts as those in FIG. First, as shown in FIG. 6A, at the time of information recording, the first beam 20d and the second beam 20e are incident on the disk 2b from one of the disks 2b (upward in the figure). The disk 2b has a structure in which a recording layer 14b, a quarter-wave plate layer 15, and a reflective layer 16 are disposed between two substrates 17c and 17d. The recording layer 14b, the quarter wavelength plate layer 15, and the reflective layer 16 are arranged in this order from the substrate 17c side to the 17d side. As described above, the beam 20d is incident on the objective lens 11c as P-polarized light (linearly polarized light whose polarization direction is parallel to the paper surface), passes through the objective lens 11c, and is converted from weakly convergent light to convergent light. The beam 20d converted into the convergent light is incident on the disk 2b from the substrate 17c side, passes through the recording layer 14b, and is collected in the recording layer 14b as direct light on the way to the reflective layer 16 side. To be lighted. On the other hand, as described above, the beam 20e enters the objective lens 11c as S-polarized light (linearly polarized light whose polarization direction is perpendicular to the paper surface), passes through the objective lens 11c, and is converted from weakly convergent light to convergent light. The second beam 20e converted into convergent light is transmitted through the recording layer 14b and further transmitted through the quarter-wave plate layer 15 and converted from S-polarized light to circularly-polarized light. The circularly polarized second beam 20e is reflected by the reflective layer 16, is transmitted through the wave plate layer 15, is converted from circularly polarized light to P-polarized light, is transmitted through the recording layer 14b, and is directed toward the substrate 17c. Thus, it is condensed in the recording layer 14b as reflected light. The direct light of the first beam 20d and the reflected light of the second beam 20e are condensed at the condensing point 18b at the same position in the recording layer 14b. A minute diffraction grating is formed at the condensing point. On the other hand, as shown in FIG. 6B, at the time of information reproduction, the first beam is incident on the recording layer 14b of the disk 2b as described above. The incident first beam is reflected by a minute diffraction grating 19b (shown by a black circle in the figure) formed in the recording layer 14b, and is emitted outside the disk 2b as reflected light 20f. The diffraction grating 19b has bit data information. At the time of information recording, the position of the condensing point of the first beam and the second beam is three-dimensionally moved in the in-plane direction and the thickness direction of the recording layer 14b to form the diffraction grating 19b. The information can be recorded three-dimensionally on the recording layer 14b. At the time of information reproduction, information can be reproduced from the reflected light of the diffraction grating 19b formed three-dimensionally in the recording layer 14b.

  The pattern of the light receiving unit and the light spot of the light receiving unit in the photodetector 12d are the same as those in the first embodiment, and specifically, as described with reference to FIGS. 3A and 3B. The method for generating the error signals Pez, PEX, and PEY from the pattern and the light spot and the method for detecting the misalignment of the condensing point are the same as those in the first embodiment. Specifically, FIG. 3A and FIG. This is as described above. In this embodiment, since the main surface of the cylindrical lens 13b does not coincide with the front focal plane of the objective lens 11c or a surface optically conjugate with it, the position of the condensing point of the second beam is the radius of the disk 2b. Change in the direction and tangential direction changes the position of the first beam on the main surface of the cylindrical lens 13b. For this reason, in the light receiving section, the light spot moves in an oblique direction. In the present embodiment as well, in the same manner as in the first embodiment, the first light spot inclined in the oblique direction according to the movement of the light spot in the oblique direction. Error signals PEX and PEY are generated using the third dividing line and the fourth dividing line. Thereby, when the position of the condensing point of the second beam is shifted in the radial direction of the disk 2b with respect to the position of the condensing point of the first beam, PEX is not 0 but PEY remains 0. can do. Similarly, when the position of the condensing point of the second beam is shifted in the tangential direction of the disk 2b with respect to the position of the condensing point of the first beam, PEY is not 0 but PEX remains 0. can do. As a result, the positional deviation in the radial direction or tangential direction of the disc 2b at the condensing point of the second beam can be detected correctly.

  The configuration of the optical information recording / reproducing apparatus of this embodiment is shown in the block diagram of FIG. In this figure, the same parts as those in FIGS. 5, 6, 3A and 3B are denoted by the same reference numerals. As illustrated, the optical head device 1b is mounted on a positioner 22b, and the disk 2b is mounted on a spindle 23b. Shutter drive circuit 25b, circuit from modulation circuit 26b to laser drive circuit 28b, circuit from amplification circuit 29b to demodulation circuit 31b, circuit from amplification circuit 32b to relay lens drive circuit 35, positioner drive circuit 36b and spindle drive circuit 37b Is controlled by the controller 24b.

  The shutter drive circuit 25b drives a shutter 9b in the optical head device 1b by supplying a current to a motor (not shown). The shutter drive circuit 25b causes the shutter 9b to pass the second beam through the optical head device 1b during information recording and to block the progress of the second beam during information reproduction.

  The modulation circuit 26b modulates a signal input from the outside as recording data according to a modulation rule when information is recorded on the disk 2b. The recording signal generation circuit 27b generates a recording signal for driving the laser 3b in the optical head device 1b based on the signal modulated by the modulation circuit 26b. When recording information on the disk 2b, the laser drive circuit 28b drives the laser 3b by supplying a current corresponding to the recording signal to the laser 3b based on the recording signal generated by the recording signal generation circuit 27b. Further, the laser drive circuit 28b drives the laser 3b by supplying a constant current to the laser 3b so that the power of the light emitted from the laser 3b is constant when reproducing information from the disk 2b.

  The amplifier circuit 29b amplifies the voltage signal output from the photodetector 12c in the optical head device 1b when reproducing information from the disk 2b. The reproduction signal processing circuit 30b performs generation, waveform equalization, and binarization of a reproduction signal recorded in the form of a diffraction grating on the disk 2b based on the voltage signal amplified by the amplifier circuit 29b. The demodulating circuit 31b demodulates the signal binarized by the reproduction signal processing circuit 30b in accordance with a demodulation rule, and outputs it as reproduction data to the outside.

  The amplifier circuit 32b amplifies a voltage signal output from the photodetector 12c in the optical head device 1b when information is recorded on the disk 2b. The error signal generation circuit 33b generates error signals Pez, PEX, and PEY for driving any one of the convex lenses 4k and 4m in the optical head device 1b based on the voltage signal amplified by the amplification circuit 32b. The relay lens driving circuit 35 supplies current to the actuator 49b (see FIG. 5) so that the error signals Pez, PEX, and PEY become 0 based on the error signals Pez, PEX, and PEY generated by the error signal generation circuit 33b. To drive one of the convex lenses 4k and 4m in the optical axis direction, the radial direction of the disk 2b, and the tangential direction of the disk 2b. The relay lens driving circuit 35 is a condensing position changing means driving circuit. As a result, in the optical head device 1b, it is possible to make the condensing points of the first beam and the second beam condensed in the recording layer of the disk 2b coincide.

  The positioner driving circuit 36b supplies current to a motor (not shown) to drive the positioner 22b to move the optical head device 1b in the radial direction of the disk 2b. As a result, when the information is recorded on the disk 2b and when the information is reproduced from the disk 2b, the condensing point of the first beam and the condensing point of the second beam in the optical head device 1b are set on the disk 2b. It can move in the radial direction.

  The spindle drive circuit 37b is for rotating the disk 2b by supplying a current to a motor (not shown) to drive the spindle. As a result, when the information is recorded on the disk 2b and when the information is reproduced from the disk 2b, the condensing point of the first beam and the condensing point of the second beam in the optical head device 1b are set on the disk 2b. It becomes relatively movable in the tangential direction.

  In the present embodiment, similarly to the optical head device described in Non-Patent Document 1, a reference surface having a track is provided on the disk 2b, and a second laser and a third photodetector are provided in the optical head device 1b. Can be provided. The beam emitted from the second laser is condensed on the track of the reference surface of the disk 2b by the objective lens 11c in the optical head device 1b. After focusing, the beam reflected by the track is received by the third photodetector. Based on the output from the third photodetector, a focus error signal indicating a positional shift in the optical axis direction of the focal point of the objective lens 11c with respect to the track and a track error signal indicating a positional shift in the radial direction of the disk 2b are generated. Is done.

  In the above case, the optical information recording / reproducing apparatus of the present embodiment can be provided with a second laser drive circuit, a third amplifier circuit, a second error signal generation circuit, and a second objective lens drive circuit.

  The second laser driving circuit supplies a constant current so that the power of the emitted light is constant when recording information on the disk 2b and reproducing information from the disk 2b. Drive. The third amplifier circuit amplifies the voltage signal output from the third photodetector when recording information on the disk 2b and reproducing information from the disk 2b. The second error signal generation circuit generates a focus error signal and a track error signal for driving one of the convex lenses 4i and 4j based on the voltage signal amplified by the third amplifier circuit. Based on the focus error signal and the track error signal generated by the second error signal generation circuit, the second objective lens drive circuit has the focus error signal and the track error signal become 0 and is emitted from the second laser. Current is supplied to the actuator so that the processed beam is focused on the track of the reference surface of the disk 2b, and either one of the convex lenses 4i and 4j is driven in the optical axis direction and the radial direction of the disk 2b. Instead of driving either one of the convex lenses 4i and 4j by the actuator, a variable focus lens and a light deflection element may be employed. The variable focus lens is a lens capable of changing a focal length according to an applied voltage. The optical deflection element is an element that can change a deflection angle in accordance with an applied voltage. The variable focus lens and the optical deflection element can be disposed in the optical path of the first beam from the polarization beam splitter 6d of the optical head device 1b to the disk 2b.

  In the present embodiment, the variable focus lens and the light deflection element may be employed in place of the actuator 49b as the focusing position adjusting means for adjusting the focusing point of the second beam in the optical head device 1b. . The variable focus lens and the optical deflection element can be disposed in the optical path of the second beam from the polarization beam splitter 6d of the optical head device 1b to the disk 2b.

[Embodiment 3]
Further, the present invention is not limited to the first and second embodiments. For example, the optical head device of the present invention may have the same configuration as the optical head device described in Non-Patent Document 1 described based on FIG. 8 instead of the first and second embodiments. In the present embodiment, unlike the first embodiment, the transmitted light of the beam splitter 41a is the first beam, and the reflected light of the beam splitter 41a is the second beam. In the optical head device of this embodiment, the objective lenses 45a and 45b are the beam condensing means, the polarizing beam splitter 41a is the beam dividing means, the polarizing beam splitter 41b is the beam separating means, and a cylindrical lens. 47a is the astigmatism applying means, and the photodetector 46b is an optical detecting means for generating the error signal. The pattern of the light receiving unit and the light spot of the light receiving unit in the photodetector 46b are the same as those in the first and second embodiments, and specifically, as described with reference to FIGS. 3A and 3B. The method of generating error signals Pez, PEX and PEY from the pattern and the light spot and the method of detecting the positional deviation of the condensing point are also the same as in the first and second embodiments. Specifically, FIG. 3A and FIG. This is as described using 3B.

It is a figure which shows an example (Embodiment 1) of a structure of the optical head apparatus of this invention. It is a figure which shows the optical path of the incident beam to a disk, and the reflected beam from a disk in the said example (Embodiment 1) of the optical head apparatus of this invention. It is a figure which shows the pattern and light spot of the light-receiving part of the said example (Embodiment 1) of the optical head apparatus of this invention. It is a figure which shows the pattern and light spot other than the above in the light-receiving part of the said example (Embodiment 1) of the optical head apparatus of this invention. It is a figure which shows an example (Embodiment 1) of the structure of the optical information recording / reproducing apparatus of this invention. It is a figure which shows an example (Embodiment 2) of a structure of the optical head apparatus of this invention. It is a figure which shows the optical path of the incident beam to a disk, and the reflected beam from a disk in the said example (Embodiment 2) of the optical head apparatus of this invention. It is a figure which shows an example (Embodiment 2) of a structure of the optical information recording / reproducing apparatus of this invention. It is a figure which shows the conventional optical head apparatus for three-dimensional recording / reproducing. It is a figure which shows the pattern and light spot of the light-receiving part of the conventional optical head apparatus for three-dimensional recording / reproducing. It is a figure which shows the pattern and light spot other than the above in the light-receiving part of the conventional optical head apparatus for three-dimensional recording / reproducing.

Explanation of symbols

1a, 1b Optical head device 2a, 2b Disk 3a, 3b Laser 4a, 4b, 4c, 4d, 4e, 4f, 4g, 4h, 4i, 4j, 4k, 4m, 4n, 4p Convex lenses 5a, 5b, 5c 1/2 Wave plates 6a, 6b, 6c, 6d, 6e Polarizing beam splitters 7a, 7b Half mirrors 8a, 8b, 8c, 8d, 8e, 8f, 8g Mirrors 9a, 9b Shutters 10a, 10b 1/4 wavelength plates 11a, 11b, 11c Objective lenses 12a, 12b, 12c, 12d Optical detectors 13a, 13b Cylindrical lenses 14a, 14b Recording layer 15 1/4 wavelength plate layer 16 Reflective layers 17a, 17b, 17c, 17d Substrates 18a, 18b Condensing points 19a, 19b Diffraction Gratings 20a, 20b, 20c, 20d, 20e, 20f Beams 21a, 21b, 21c, 21d, 21e, 21f 21g, 21h, 48a, 48b, 48c, 48d Light receiving area 22a, 22b Positioner 23a, 23b Spindle 24a, 24b Controller 25a, 25b Shutter drive circuit 26a, 26b Modulation circuit 27a, 27b Recording signal generation circuit 28a, 28b Laser drive circuit 29a 29b Amplifying circuits 30a, 30b Reproduction signal processing circuits 31a, 31b Demodulating circuits 32a, 32b Amplifying circuits 33a, 33b Error signal generating circuit 34 Objective lens driving circuit 35 Relay lens driving circuits 36a, 36b Positioner driving circuits 37a, 37b Spindle driving circuits 38 Disc 39a, 39b Semiconductor laser 40a, 40b, 40c, 40d, 40e Convex lens 41a, 41b, 41c Beam splitter 42 Interference filter 43 Mirror 44 Shutter 45a, 45b Object lens 46a, 46b, 46c Photodetector 47a, 47b Cylindrical lens 100a, 100b, 100c, 100d, 100e, 100f, 100g, 100h, 100i Light spot 101 First dividing line 102 Second dividing line 103 Third dividing line 104 Fourth dividing line

Claims (12)

Beam condensing means for condensing the first beam and the second beam at the same condensing point in a state of being opposed to each other;
Astigmatism imparting means for imparting astigmatism to the first beam that has passed through the condensing point;
Photodetection means for detecting the first beam provided with the astigmatism,
The light detection means includes a light receiving unit that receives the light spot of the first beam to which the astigmatism is applied and outputs a signal,
The light receiving unit is
A first dividing line corresponding to a first direction in a plane direction perpendicular to the optical axis of the first beam of the condensing point and intersecting the optical axis of the first beam;
A second dividing line corresponding to a second direction orthogonal to the first direction in the plane direction and intersecting an optical axis of the first beam;
A third dividing line that intersects at an intersection of the first dividing line and the second dividing line and is inclined with respect to the first dividing line; and
Having at least eight light receiving regions that intersect at the intersection of the first dividing line and the second dividing line and that are separated from each other by at least four dividing lines of the fourth dividing line inclined with respect to the second dividing line; An optical head device characterized by the above. The third dividing line is parallel to the moving direction of the light spot of the light receiving unit when the focusing point of the second beam is displaced in the first direction with respect to the focusing point of the first beam. And
The fourth dividing line is parallel to a moving direction of the light spot of the light receiving unit when the focusing point of the second beam is displaced in the second direction with respect to the focusing point of the first beam. The optical head device according to claim 1, wherein: In the light receiving unit, the four dividing lines are straight lines, the inclination direction of the third dividing line with respect to the first dividing line is clockwise, and the fourth dividing line with respect to the second dividing line The tilt direction is counterclockwise,
Or
In the light receiving portion, the four dividing lines are straight lines, the inclination direction of the third dividing line with respect to the first dividing line is counterclockwise, and the fourth dividing line with respect to the second dividing line The optical head device according to claim 1, wherein the inclination direction is clockwise. In order to generate a first error signal indicating a positional deviation of the condensing point of the second beam in the optical axis direction, the eight light receiving regions are formed by the first dividing line and the second dividing line in the light receiving unit. Are divided into four groups of light receiving areas,
In order to generate a second error signal indicating a positional deviation of the condensing point of the second beam in the first direction, the eight light receiving regions are divided into two light receiving regions by the fourth dividing line in the light receiving unit. Divided into groups,
In order to generate a third error signal indicating a positional deviation of the condensing point of the second beam in the second direction, the eight light receiving regions are divided into two light receiving regions by the third dividing line in the light receiving unit. 4. The optical head device according to claim 1, wherein the optical head device is divided into groups. Further, based on at least one error signal of the first error signal, the second error signal, and the third error signal, the condensing point of the second beam is set to the optical axis direction, the first direction, and the first error signal. 5. The optical head according to claim 4, further comprising a focusing position adjusting means capable of adjusting the focusing point of the second beam to a correct focusing point by moving in at least one of two directions. apparatus. 6. The optical according to claim 1, wherein the beam condensing unit condenses the direct light of the first beam and the direct light of the second beam at the condensing point. Head device. The said beam condensing means condenses one direct light and the other reflected light of said 1st beam and said 2nd beam at the said condensing point. An optical head device according to claim 1. The optical head device according to any one of claims 1 to 7,
Error signal generating means for generating an error signal indicating a positional deviation of the condensing point of the second beam at the condensing point;
The error signal generating means includes
The eight light receiving regions are divided into four light receiving region groups by the first dividing line and the second dividing line, and based on output signals from the four light receiving region groups, the condensing point of the second beam Generate a first error signal that represents the displacement in the optical axis direction,
The eight light receiving regions are divided into two light receiving region groups by the fourth dividing line, and based on the output signals from the two light receiving region groups, the misalignment of the condensing point of the second beam in the first direction. A second error signal representing
The eight light receiving regions are divided into two light receiving region groups by the third dividing line, and based on the output signals from the two light receiving region groups, the misalignment in the second direction of the condensing point of the second beam. An optical information recording / reproducing apparatus that generates a third error signal representing The optical head device according to claim 5,
The condensing position adjusting means determines the condensing point of the second beam based on the first error signal, the second error signal, and the third error signal, in the optical axis direction, the first direction, and the first direction. By moving in at least one of the two directions, the focusing point of the second beam is adjusted to the correct focusing point,
9. The optical information recording / reproducing apparatus according to claim 8, further comprising a condensing position adjusting means driving means for driving the condensing position adjusting means. Furthermore, it has a condensing point moving means,
The optical system according to claim 8 or 9, wherein the focusing point moving means moves the focusing point in the optical head device according to any one of claims 1 to 7 in an optical axis direction. Information recording / reproducing apparatus. Using the optical head device according to any one of claims 1 to 7,
The eight light receiving regions are divided into four light receiving region groups by the first dividing line and the second dividing line, and based on output signals from the four light receiving region groups, the condensing point of the second beam Generating a first error signal representing a positional shift in the optical axis direction;
The eight light receiving regions are divided into two light receiving region groups by the fourth dividing line, and based on the output signals from the two light receiving region groups, the misalignment of the condensing point of the second beam in the first direction. The eight light receiving regions are divided into two light receiving region groups by the step of generating a second error signal representing the third dividing line and the third dividing line, and based on the output signals from the two light receiving region groups, And a third error signal representing a positional deviation of the condensing point in the second direction. The focusing point of the second beam is moved in at least one of the optical axis direction, the first direction, and the second direction based on the error signal generated by the error signal generation method according to claim 11. Accordingly, the optical head device according to any one of claims 1 to 7, further comprising a condensing position adjustment step of adjusting a condensing point of the misaligned second beam to a correct position. Condensing position adjustment method.

Images