JP2005235393A - Optical detector, optical pickup and optical information reproducing apparatus using optical pickup - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an optical system which is lower in cost and simpler than those of a conventional optical system with the structure of an optical system in which inexpensive optical elements and semiconductor lasers are used as small in number as possible in an optical pickup which performs the recording/reproducing of information in/from a plurality type of optical disks. <P>SOLUTION: As a means for solving the problem, an optical pickup is made to have such structure of an optical system that it has a semiconductor laser having two laser sources of different wavelengths disposed in the same package, one diffraction grating and one optical detector and it is made to disposes a plurality of light reception areas each having four divisional light reception planes of the shape of a square with a cross inside at positions where light beams reflected from an optical disk are applied and, at the same time, to generate a focus error signal by an astigmatism method by using independently these light reception areas and a tracking error signal by a differential phase detection method by using one or both the light reception areas by a signal processing circuit. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a photodetector, an optical pickup used for reproducing an information signal recorded on an optical information recording medium (hereinafter referred to as an optical disc), and an optical information reproducing apparatus (hereinafter referred to as an optical disc device) using the same. ).

  An optical disc device is an information recording / reproducing device characterized by non-contact, large capacity, high-speed access, and low-cost media. Utilizing these features, it can be used as a digital audio signal recording / reproducing device or as an external storage device of a computer. Has been.

  Currently, there are various types of optical discs depending on the substrate thickness and the corresponding wavelength. For example, the optimum wavelength of the laser beam for recording or reproduction with respect to a disk substrate thickness of 1.2 mm such as CD or CD-R is 780 nm band, whereas recently standardized DVD-ROM or DVD-RAM, etc. The disk substrate thickness is 0.6 mm and the corresponding wavelength is in the 650 nm band. There has also been proposed an optical disc apparatus using a laser beam having a further shorter wavelength. Based on these circumstances, for example, an optical pickup for DVD that has begun to spread in recent years has two different wavelengths of 780 nm band and 650 nm band in consideration of compatibility with CD optical disks that have already been widely spread. The one with a semiconductor laser is the mainstream.

  On the other hand, along with the expansion of the use of these optical discs, downsizing and cost reduction of optical disc apparatuses are being promoted, and in order to achieve this, technology for downsizing and simplifying optical pickups is indispensable. In order to reduce the size and simplification of the optical pickup, it is effective to reduce the number of parts constituting the optical system or use a low-cost part. In particular, when considering the correspondence to multiple types of optical discs, an optical system corresponding to each optical disc is required. However, the simplification of the optical system or the reduction in the number of components by sharing optical components can Effective for downsizing and cost reduction. As an example, in Japanese Patent Application Laid-Open Nos. 8-55363 and 9-54977, in order to enable reproduction of a plurality of types of optical discs, laser beams from two semiconductor lasers are combined on an intermediate optical path. A technique for enabling information reproduction using two objective lenses is disclosed.

JP-A-8-55363 JP-A-9-54977

  As described above, an optical pickup equipped with two semiconductor lasers has an optical system configuration in which a condensing optical system portion such as an objective lens and a collimating lens is shared in order to reduce the size and cost of the optical pickup itself. There are many things that exist. An example of such a conventional optical system configuration is shown in FIGS.

  In FIG. 1A, for example, a light beam emitted from a semiconductor laser 11 oscillating at a wavelength of 650 nm reaches the dichroic half prism 12. The dichroic half prism 12 is an optical element in which two prisms are bonded, and a reflecting film that reflects about 50% and transmits about 50% of laser light with a wavelength of 650 nm and transmits about 100% of laser light with a wavelength of 780 nm. Is formed. The light beam emitted from the semiconductor laser 11 is reflected by the reflecting film of the dichroic half prism 12 arranged at an angle of 45 ° with respect to the optical axis, and then converted into a parallel light beam by the collimator lens 5. The objective lens 6 is reached. The objective lens 6 is integrally held by the actuator 7, and by energizing the drive coil 8, for example, a light beam can be focused on the information recording surface of the optical disc 1 such as a DVD-ROM to form a light spot. Is possible. The light beam reflected from the optical disk 1 follows the same optical path as the outward light, passes through the objective lens 6 and the collimating lens 5, and reaches the dichroic half prism 12. About 50% of the return light amount passes through the dichroic half prism 12 and then reaches the dichroic half mirror 13. Here, the dichroic half mirror 13 is an optical element that transmits about 100% of 650 nm wavelength laser light and transmits about 50% of 780 nm wavelength laser light and reflects about 50%.

  For this reason, the light beam that has reached the dichroic half mirror 13 passes through the dichroic half mirror 13 and is collected at a predetermined position of the photodetector 14.

  On the other hand, in FIG. 1B, for example, a light beam emitted from the semiconductor laser 15 oscillating at a wavelength of 780 nm passes through the diffraction grating 16 for generating three beams and then has an angle of about 45 ° with respect to the optical axis. It is configured to reach the dichroic half mirror 13 that is arranged. As described above, the dichroic half mirror 13 has a characteristic of reflecting about 50% of the laser light having a wavelength of 780 nm, and the dichroic half prism 12 has a characteristic of transmitting about 100% of the laser light having a wavelength of 780 nm. The light beam emitted from the semiconductor laser 15 is reflected by the dichroic half mirror 13, passes through the dichroic half prism 12, is converted into a parallel light beam by the collimator lens 5, and reaches the objective lens 6. The objective lens 6 is a lens capable of condensing the light beam emitted from the semiconductor laser 15 on the information recording surface on the optical disk 10 even on the optical disk 10 such as a CD-ROM. A light spot is formed on the surface. The light beam reflected from the optical disk 10 travels in the same optical path as that of the outward light, passes through the objective lens 6, the collimating lens 5, and the dichroic half prism 12, and reaches the dichroic half mirror 13.

  As described above, since the dichroic half mirror 13 is an optical element that transmits about 780 nm wavelength laser light by about 50%, the light beam that has reached the dichroic half mirror 13 passes through the dichroic half mirror 13 and then the photodetector 14. The light is condensed at a predetermined position.

  In the configuration of the conventional optical system shown in FIG. 1, the condensing optical system portion from the dichroic half prism 12 through the collimating lens 5 to the objective lens 6 is shared, and the number of parts is reduced. There is a need for wavelength-selective optical elements such as dichroic half prisms and dichroic half mirrors, which have wavelength selectivity for two different wavelengths, and two different wavelength semiconductor lasers. Optical elements and semiconductor lasers are still expensive parts when viewed from the components of the optical pickup, which hinders further cost reduction of the optical pickup.

  In view of the above situation, the problem to be solved by the present invention is that an optical pickup for recording or reproducing information on a plurality of different types of optical discs and an optical disc apparatus using the same are compared with the conventional optical system configuration. In addition to realizing a simple configuration, a low-cost optical system configuration is realized by using inexpensive optical elements and as few semiconductor lasers as possible.

  In order to solve the above problems, in the photodetector, the optical pickup, and the optical information reproducing apparatus using the same in the present invention, the semiconductor laser having the first or second or both laser light sources, the first or first An optical branching element that branches light beams emitted from two or both laser light sources into at least three light beams, and a first or second optical information recording medium in which the light beams including the three light beams are different. And a light collecting optical system that irradiates each predetermined position on the optical information recording medium with an independent light spot, and light that is emitted from the first laser light source and reflected by the first optical information recording medium A first light receiving region disposed at a position irradiated with the beam, and a first light disposed at a position irradiated with the light beam emitted from the second laser light source and reflected by the second optical information recording medium. A photodetector having a light receiving region, and a focus error signal and a tracking error signal of a light spot irradiated on the optical information recording medium by performing a predetermined calculation on a photoelectric conversion signal obtained from the photodetector. A signal processing circuit for generating and reproducing an information signal recorded on the optical information recording medium, wherein the photodetector is divided into four in a square shape, the first and second And the signal processing circuit outputs a signal capable of generating a focus error signal by the astigmatism method independently from each of the first, second, or both light receiving regions, and the first or second light receiving region. Alternatively, a signal capable of generating a tracking error signal by the differential phase detection method is output from both light receiving areas.

  In order to solve the above problems, in the present invention, the photodetector is arranged at a position where a light beam emitted from the first laser light source and reflected by the first optical information recording medium is irradiated. Are divided into two parts, each having a third and a fourth light-receiving region each having two light-receiving surfaces, and the signal processing circuit is independently tracking error by push-pull method from the third, fourth, or both light-receiving regions. A signal that can generate a signal is output.

  Further, in order to solve the above problems, in the present invention, the photodetector is disposed at a position where a light beam emitted from the first laser light source and reflected by the first optical information recording medium is irradiated. And a signal processing circuit for outputting a signal capable of generating a tracking error signal by a three-beam method from the third and fourth light receiving regions.

  In order to solve the above problems, in the present invention, the photodetector is disposed at a position where a light beam emitted from the first laser light source and reflected by the first optical information recording medium is irradiated. A third and a fourth light receiving region divided into four in a square shape, and the signal processing circuit independently outputs a focus error signal by an astigmatism method from each of the third, fourth, or both light receiving regions. A signal that can be generated is output, and a signal that can generate a tracking error signal by a push-pull method is output independently from the third, fourth, or both light receiving regions.

  Further, in order to solve the above problems, in the present invention, the photodetector is arranged at a position where a light beam emitted from the second laser light source and reflected by the second optical information recording medium is irradiated. Are divided into two parts, and each of the signal processing circuits includes a fifth and a sixth light receiving region each having two light receiving surfaces, and the signal processing circuit independently performs tracking error by a push-pull method from the fifth, sixth, or both light receiving regions. A signal that can generate a signal is output.

  In order to solve the above problems, in the present invention, the photodetector is disposed at a position where a light beam emitted from the second laser light source and reflected by the second optical information recording medium is irradiated. And a signal processing circuit for outputting a signal capable of generating a tracking error signal by a three-beam method from the fifth and sixth light receiving regions.

  Further, in order to solve the above problems, in the present invention, the photodetector is disposed at a position where a light beam emitted from the second laser light source and reflected by the second optical information recording medium is irradiated. A fifth and a sixth light receiving region divided into four in a square shape, and the signal processing circuit independently outputs a focus error signal by an astigmatism method from the fifth, sixth or both light receiving regions. The tracking error signal is generated by the push-pull method independently from the fifth, sixth, or both light receiving regions.

  In order to solve the above problems, in the present invention, a semiconductor laser having the first, second, or both laser light sources and three light beams emitted from the first, second, or both laser light sources are respectively provided. An optical branching element that splits into three light beams, and the three branched light beams are collected on the first or second optical information recording medium, and each is independent at a predetermined position on the optical information recording medium. A condensing optical system for irradiating the light spot, and a first optical beam arranged so that three light beams emitted from the first laser light source and reflected by the first optical information recording medium are independently received. , Second and third light receiving regions, and fourth, arranged so that three light beams emitted from the second laser light source and reflected by the second optical information recording medium are received independently. 5th and 6th And a focus error signal of a light spot irradiated on the first or second optical information recording medium by performing a predetermined calculation on a photoelectric conversion signal obtained from the photodetector. And a signal processing circuit for generating a tracking error signal and reproducing the information signal recorded on the first or second optical information recording medium, the first and fourth light receiving regions Each is divided into four in a square shape, each having four light receiving surfaces, and each of the second, third, fifth and sixth light receiving regions is divided into at least two parts, each having at least two light receiving surfaces. And the signal processing circuit generates a focus error signal by the astigmatism method independently from the first, fourth, or both light receiving regions, and the first, fourth, or both light receiving regions. Generating a tracking error signal by a differential phase detection method, and generating a tracking error signal by a push-pull method independently from the second, third, fifth, sixth, or each of the light receiving regions. To do.

  Furthermore, in order to solve the above-described problem, in the present invention, the first and second optical information recording media are each perpendicular to a track in at least one set of light spots among a plurality of light spots irradiated on the first and second optical information recording media. The light spot interval in the direction is approximately one half of the track pitch in each optical information recording medium, and the ratio of the track pitch in the first and second optical information recording media to the first and second The wavelength ratio in the laser light source is set to be approximately equal.

  The first, second, or both laser light sources may be provided in one housing.

  In addition, a signal processing circuit that generates a focus error signal and a tracking error signal of the light spot irradiated on the optical information recording medium by performing a predetermined calculation on the photoelectric conversion signal obtained from the photodetector is an optical signal. It may be provided in a detector or an optical pickup.

  Here, a method of dividing the light receiving area of the photodetector into four squares will be described. By using this method of dividing into four, the light receiving region in the photodetector is divided into four by a first dividing line and a second dividing line that intersect each other. In other words, the shape of the light receiving area after being divided into four is the character shape of the Chinese character “ta”.

  In order to solve the above problems, the optical pickup according to the present invention or the optical information reproducing apparatus using the optical pickup includes a semiconductor laser having the first, second, or both laser light sources, and the first or second. Alternatively, a light branching element that branches light beams emitted from both laser light sources into at least three light beams, and a light beam including the three light beams on different first or second optical information recording media. A condensing optical system for condensing and irradiating a predetermined spot on the optical information recording medium with an independent light spot, and a light beam emitted from the first laser light source and reflected by the first optical information recording medium A first light receiving region arranged so that the first position where the light is irradiated is within the light receiving range, and a light beam emitted from the second laser light source and reflected by the second optical information recording medium A photodetector having a second light receiving region arranged so that the second position to be irradiated is within the light receiving range; and a light beam reflected by the first optical information recording medium, or the second And a light detection optical system for guiding the light beam reflected by the optical information recording medium to a predetermined position of the light detector.

The optical detection optical system has a function of guiding the first light beam emitted from the first semiconductor laser light source and reflected from the optical information recording medium to a first light receiving region at a predetermined position of the photodetector. And a function of guiding the second light beam reflected from the optical information recording medium to a second light receiving region at a position different from the first light receiving region in the photodetector. .
The light detection optical system includes a hologram element having a linear or curved grating groove pattern.As an example of the hologram element, the first light beam having a predetermined wavelength is not diffracted, The second light beam having a wavelength different from that of the first light beam has wavelength selectivity for diffracting with a predetermined diffraction efficiency.

  As another example, a light beam having a predetermined polarization direction is not diffracted, but a light beam having a polarization direction perpendicular to the polarization direction is diffracted with a predetermined diffraction efficiency. The first or second semiconductor laser light source is emitted, is reflected by the optical information recording medium, and is not diffracted by the hologram element in the optical path of the first or second light beam toward the hologram element. A polarization conversion element is provided that gives a predetermined polarization direction to the first light beam and gives a polarization direction diffracted by the hologram element to the second light beam.

The condensing optical system has a function of condensing the first light beam emitted from the first semiconductor laser light source and narrowing it down to a first optical information recording medium having a predetermined substrate thickness, The second optical beam emitted from the second semiconductor laser light source is condensed to have a function of narrowing down to a second optical information recording medium having a substrate thickness different from that of the first optical information recording medium.
Further, in the above optical pickup device, the first semiconductor laser light source is a semiconductor laser light source having a wavelength of 660 nm or less, and the first optical information recording medium is an optical disk having a substrate thickness of about 0.6 mm. The second semiconductor laser light source is a semiconductor laser light source having a wavelength of 780 nm to 790 nm, and the second optical information recording medium is an optical disk having a substrate thickness of about 1.2 mm. In addition, the polarization conversion element functions as a 5λ / 4 plate for the first light beam emitted from the first semiconductor laser light source.
In the above optical pickup device, an astigmatism method is used to detect a focus error signal from the first light beam emitted from the first semiconductor laser light source and reflected from the first optical information recording medium. When detecting a focus error signal from the second light beam emitted from the second semiconductor laser light source and reflected from the second optical information recording medium, an astigmatism method, a knife edge method, or a beam size method is used. When detecting a tracking error signal from the first light beam emitted from the first semiconductor laser light source and reflected from the first optical information recording medium, a differential phase detection method (Differential Phase Detection method) or a differential push A second method of using the pull method (DPP method) and emitting the second semiconductor laser light source and reflecting the second optical information recording medium. When detecting the tracking error signal from the light beam using a push-pull method or differential push-pull method or three-spot method.

  Further, when the tracking error signal of the second optical information recording medium is detected by a differential push-pull method, the second light beam emitted from the second semiconductor laser light source is diffracted into at least three light beams. 3 spots that are separated from each other and that the spot interval of the three light beams is approximately one half of the track pitch of the information track of the optical information recording medium in the radial direction on the second optical information recording medium The three-spot diffraction grating further diffracts and separates the first light beam emitted from the first semiconductor laser light source into at least three light beams, and the three light beams. Are formed in advance on a predetermined write-once or rewritable optical information recording medium in the radial direction on the first optical information recording medium. That to approximately one half of the pitch of the groove.

  Further, by adjusting the position of the optical detection optical system, the position of the light receiving region in the photodetector to which the first or second light beam reflected by the optical information recording medium is guided is adjusted. I can do it.

  Further, by adjusting the position of the optical detection optical system, the position of the light receiving region in the photodetector to which the first or second light beam reflected by the optical information recording medium is guided is the same linear shape. Can be arranged.

  Further, by adjusting the position of the light detection optical system, the light receiving region in the light detector to which the first or second light beam reflected by the optical information recording medium is guided is made the same. I can do it.

Alternatively, in the optical pickup in the present invention or the optical information reproducing apparatus using the same, a semiconductor laser having the first, second, or both laser light sources,
An optical branching element that splits a light beam emitted from the first, second, or both laser light sources into at least three light beams, and a first or second light beam that includes the three light beams are different from each other. A condensing optical system for condensing on an optical information recording medium and irradiating each independent light spot on a predetermined position on the optical information recording medium, and a light beam reflected by the first optical information recording medium for irradiation A first light receiving region arranged so that the first position is within the light receiving range, and a second position where the light beam reflected by the second optical information recording medium is irradiated is within the light receiving range. And a light beam reflected by the first optical information recording medium or a light beam reflected by the second optical information recording medium. To a predetermined position of the photodetector So that and a detection optical system.

  In the optical pickup, the first position where the light beam reflected by the first optical information recording medium is irradiated and the second position where the light beam reflected by the second optical information recording medium is irradiated. The light detection optical system reflects a light beam reflected by the first optical information recording medium or a light beam reflected by the second optical information recording medium so as to change the position relative to the position of To the photodetector.

  Further, in the optical pickup, the first light receiving region and the second light receiving region arranged so that the first position irradiated with the light beam reflected by the first optical information recording medium is within the light receiving range. The photodetection optical system is provided so that the second light receiving region arranged so that the second position irradiated with the light beam reflected by the optical information recording medium is within the light receiving range is provided at a different position. The light beam reflected by the first optical information recording medium or the light beam reflected by the second optical information recording medium is guided to the photodetector.

  In the optical pickup, the first position where the light beam reflected by the first optical information recording medium is irradiated and the second position where the light beam reflected by the second optical information recording medium is irradiated. By changing the relative position of the first optical information recording medium, the light detection optical system arranges the first light receiving area and the second light receiving area in a straight line. The light beam reflected by the medium or the light beam reflected by the second optical information recording medium is guided to the photodetector.

  In the optical pickup, the first position where the light beam reflected by the first optical information recording medium is irradiated and the second position where the light beam reflected by the second optical information recording medium is irradiated. By changing the relative position with respect to the position of the first optical information recording medium, the light detection optical system is configured so that the first light receiving area and the second light receiving area are at the same position. Or the light beam reflected by the second optical information recording medium is guided to the photodetector.

As described above, according to the embodiments of the present invention, an optical pickup using a semiconductor laser in which laser light sources having two different wavelengths are arranged in the same casing, at least one diffraction grating, and one photodetector. With this optical system configuration, it is possible to obtain focus error signals and tracking error signals necessary for reproduction or recording of various optical discs having different substrate thicknesses and different groove structures such as DVD-ROM, DVD-RAM and CD-ROM. is there. Furthermore, when the ratio of the two laser wavelengths and the ratio of the track pitch of the optical disk are substantially equal, an optical system can be realized with one diffraction grating, and at the same time, with respect to optical components such as the diffraction grating and the half mirror, wavelength characteristics and Since polarization characteristics are not required, an optical system that is simpler and less expensive than the conventional one can be realized.
On the other hand, when a two-wavelength multi-laser is used as the light source of the optical pickup device, the diffraction grating according to the present invention makes it possible to share the light receiving area of the photodetector with respect to two wavelengths. By reproducing information from multiple types of optical discs with a single optical detection system, the number of optical components can be reduced, and further downsizing, simplification, and cost reduction of the optical pickup device can be realized.

  The configuration and operation of the optical pickup as the first embodiment of the present invention will be described below with reference to the drawings.

  In FIG. 2A, a semiconductor laser 2 is a laser light source that oscillates at a wavelength of 650 nm, for example, and a laser light source that oscillates at a wavelength of 780 nm, for example (two-wavelength multilaser). The two laser light sources are arranged at a predetermined interval d. FIG. 2A shows a state in which the 650 nm laser light source in the semiconductor laser 2 is turned on. The light beam emitted from the 650 nm laser light source passes through the diffraction grating 3 and reaches the half mirror 4. Here, the light beam that has passed through the diffraction grating 3 is at least three light beams: zero-order light that is directly transmitted by the diffraction grooves formed on the grating and ± first-order diffracted light that travels separately from the zero-order light at a predetermined diffraction angle. This is a beam configuration. The half mirror 4 is disposed at an angle of 45 ° with respect to the optical axis of the light beam. The reflection film formed on the surface of the half mirror 4 reflects about 50% of 650 nm wavelength laser light and about 50%. It is an optical element to transmit. The light beam is reflected by the reflection film of the half mirror 4 disposed at an angle of 45 ° with respect to the optical axis, and then converted into a parallel light beam by the collimator lens 5 and reaches the objective lens 6. Here, the objective lens 6 corresponds to laser light having a wavelength of 650 nm and a wavelength of 780 nm, and can be focused on optical disks having different substrate thicknesses. The objective lens 6 is integrally held by an actuator 7, and a light beam is applied to the information recording surface of the optical disk 1 having a substrate thickness of 0.6 mm, such as a DVD-ROM or DVD-RAM, by energizing the drive coil 8. It is possible to form three light spots of 0th order light and ± 1st order diffracted light. The light beam reflected from the optical disk 1 follows the same optical path as the outward light, passes through the objective lens 6 and the collimating lens 5 and reaches the half mirror 4, and about 50% of the return light quantity of the light beam is half mirror 4. After being transmitted, the light is condensed at a predetermined position of the photodetector 9.

  FIG. 2B shows a state in which the 780 nm laser light source in the semiconductor laser 2 is lit. A light beam emitted from a 650 nm laser light source and a 780 nm laser light source arranged at a predetermined distance d passes through the diffraction grating 3 and reaches the half mirror 4. Here, the light beam transmitted through the diffraction grating 3 is at least three light beams of 0th order light and ± 1st order diffracted light diffracted by the diffraction grooves formed on the grating. The half mirror 4 is arranged so as to form an angle of 45 ° with respect to the optical axis of the light beam. At the same time, the reflecting film formed on the surface reflects about 50% of the laser light having a wavelength of 780 nm. An optical element that transmits about 50%.

  The light beam is reflected by the reflection film of the half mirror 4 disposed at an angle of 45 ° with respect to the optical axis, and then converted into a parallel light beam by the collimator lens 5 and reaches the objective lens 6. The objective lens 6 is integrally held by an actuator 7, and when a drive coil 8 is energized, a light beam is applied onto an information recording surface of an optical disc 10 having a substrate thickness of 1.2 mm such as a CD-ROM or CD-R. It is possible to form three spots of 0th order light and ± 1st order diffracted light.

  The light beam reflected from the optical disk 10 follows the same optical path as the outward light, passes through the objective lens 6 and the collimating lens 5 and reaches the half mirror 4, and about 50% of the return light quantity of the light beam is half mirror 4. After being transmitted, the light is condensed at a predetermined position of the photodetector 9.

  3 to 5 show the spot arrangement on the optical disk in the first embodiment of the present invention. FIG. 3 shows the spot arrangement on the DVD-ROM disk, and FIG. 4 shows the spot on the DVD-RAM disk. Arrangement, FIG. 5 shows a spot arrangement on a CD-R disc.

  In FIG. 3, the recording pits 200 on the DVD-ROM disc are arranged in the track direction of the optical disc at an interval of a track pitch Tp1 (0.74 μm). As described with reference to FIG. 2, the light spot on the optical disk is made up of three spots of zero-order light and ± first-order light by the diffraction grating 3, and a spot 100 of zero-order light, a spot 101 of + 1st-order diffracted light, As shown in FIG. 3, the spots 102 of the −1st order diffracted light are arranged on the optical disc 1 at an interval Tp11 corresponding to the track pitch Tp1.

  In FIG. 4, on the DVD-RAM disc, guide grooves 202 are alternately formed with guide groove intervals 203 at intervals of a track pitch Tp2 (1.48 μm). The recording marks 201 are arranged in the track direction of the optical disc at an interval Tp21 (0.74 μm) corresponding to half of Tp2. The light beam is diffracted by the diffraction grating 3 in the same manner as in FIG. 3, and becomes three spots of zero-order light and ± first-order diffracted light on the optical disk. The spot 100 of the 0th order light, the spot 101 of the + 1st order diffracted light, and the spot 102 of the −1st order diffracted light are placed on the optical disc 1 at an interval Tp22 (= Tp11) corresponding to substantially half of the track pitch Tp2, as shown in FIG. Has been placed.

  In FIG. 5, guide grooves 401 are alternately formed on the CD-R disc with guide groove intervals 402 at intervals of a track pitch Tp3 (1.6 μm). The recording mark 400 is arranged in the track direction on the guide groove 401 of the optical disc at Tp3. The light spots on the optical disk 10 are the three spots of 0th-order light and ± 1st-order diffracted light as in FIGS. 3 and 4, and these 0th-order light spot 100 and + 1st-order diffracted light spots 101 and −1. The spots 102 of the next diffracted light are arranged on the optical disc 10 at intervals of Tp31 corresponding to approximately half of Tp3.

  Here, since the diffraction angle in the same diffraction grating by the laser beams having different wavelengths has a relation that it is substantially proportional to the wavelength under the condition that the diffraction angle is small, the three spots on the optical disk in the first embodiment are not related. The interval is almost proportional to the wavelength. Further, since the direction of the spot row on the optical disk, that is, the diffraction direction of the light beam is the same regardless of the wavelength, the distance between the spots on the optical disk in the disk radial direction is substantially proportional to the wavelength. That is, the following relationship holds between the two wavelengths λ1 (= 650 nm) and λ2 (= 780 nm) and the spot intervals Tp22 and Tp31 on the optical disc.

  According to equation (1), the spot interval Tp22 on the DVD-RAM disk when the spot interval Tp31 on the CD-R disc is set to 0.80 μm is 0.67 μm. This is a shift position of about 10% with respect to the half value of 0.74 μm of the track pitch in the DVD-RAM disk, and the servo signal is detected from the DVD-RAM disk without any problem by using a servo signal detection method described later. It is possible. Conversely, when the spot interval Tp22 on the DVD-RAM disc is set to 0.74 μm, the spot interval Tp31 on the CD-R disc is 0.89 μm. This is a deviation position of about 10% with respect to a track pitch of 0.8 μm on the CD-R disc, and a servo signal can be detected from the CD-R disc without any problem by using a servo signal detection method described later. It is possible to select an optical disc as a reference for setting the spot interval.

  The photodetector 9 shown in FIG. 2 has a configuration in which at least one light receiving area consisting of four light receiving surfaces is formed in a square shape with respect to laser light having a predetermined wavelength, as will be described later. . The light beams of the 0th order light and the ± 1st order diffracted light reflected from the optical disc 1 or the optical disc 10 are substantially the center of each light receiving region, that is, the point where the vertical and horizontal dividing lines in the light receiving region cross each other and the intensity of the light beam. The light is collected at a position where the centers substantially coincide. At this time, since each light beam is given a predetermined astigmatism when passing through the half mirror 4 disposed to be inclined with respect to the optical path, a square-shaped light-receiving region as will be described later. Thus, a focus error signal is detected by an astigmatism method. Similarly, the tracking error signal by the push-pull method or the differential phase detection method can be detected by using the output signal composed of four light receiving surfaces.

  Next, the intensity distribution of the light spot on the optical disc 1 will be described with reference to FIG. In this embodiment, as shown in FIG. 4, the irradiation position interval in the disk radial direction of the spots 100, 101, and 102 irradiated to the optical disk 1 coincides with substantially half of the guide groove pitch of the DVD-DAM disk. Is set to That is, for example, the arrangement of the three light spots 100, 101, 102 on the DVD-RAM disk shown in FIG. 6 is such that the zero-order light spot 100 is located between the guide grooves 203 of the disk as shown in FIG. , The light spot 101 of the + 1st order diffracted light and the light spot 102 of the −1st order diffracted light are respectively located directly above the adjacent guide grooves 202. Even in the case where the light spot irradiation position is shifted relative to the guide groove 202, the positional relationship between the light spots 100, 101, 102 is as shown in FIG. Is always kept. On the other hand, the reflected light beam from the optical disk is affected by diffraction by the guide groove 202, and has a unique intensity distribution pattern that periodically changes according to the relative position change of the irradiation position of the light spot and the guide groove of the disk. Will have. The intensity distributions of the reflected light beam of the 0th-order light spot 100 and the reflected light beam of the light spot 101 by the + 1st order diffracted light and the reflected light beam of the light spot 102 by the −1st order diffracted light are compared. As shown in c), the change is such that the left and right are completely reversed.

By the way, when a focus error signal by the astigmatism method is detected from these reflected light beams, there is a problem that a large disturbance is likely to occur in the detected focus error signal. This is mainly due to the periodic change in the intensity distribution pattern of the reflected light beam due to the diffraction effect in the guide groove 202 described above, and the push-pull signal leakage disturbance caused thereby. Therefore, as shown in FIGS. 7A and 7B, when the focus error signal obtained from the reflected light flux of the light spot 100 and the focus error signal obtained from the reflected light flux of the light spot 101 and the light spot 102 are compared, While the waveform of the focus error signal itself is substantially the same, the phase of the disturbance component generated in the signal is almost completely inverted.
Therefore, when the focus error signal obtained from the reflected light beam of the light spot 100 and the focus error signal obtained from the reflected light beam of the light spot 101 or the light spot 102 or a sum signal of both are added, FIG. As shown, the focus error itself is doubled, while a good focus error signal in which the disturbance component is almost completely canceled can be obtained.

  The phenomenon as described above is similarly applied to tracking error signal detection by the push-pull method. That is, in general, when detecting a tracking error signal by the push-pull method, when the objective lens is displaced in the tracking direction, the light spot irradiated on the light receiving surface of the photodetector 9 is also displaced accordingly, and FIG. And as shown in (b), a large offset occurs in the detected tracking error signal. This offset is the same for the tracking signal detected from the reflected light beam of the light spot 100 and the tracking error signal detected from the reflected light beam of the light spot 101 and the light spot 102 as shown in FIGS. Occurs only to the same extent. On the other hand, the tracking error signal itself is based on the phase of the signal detected from the reflected light beam of the light spot 100 and the reflected light beams of the light spots 101 and 102 for the same reason as described in the explanation of the focus error signal. The phase of the detected signal is almost completely inverted. Therefore, by subtracting the tracking error signal detected from the disk reflected light of each light spot, only the offset component is canceled, and the offset as shown in FIG. 8C is greatly reduced. A tracking error signal can be obtained.

  In the embodiment according to the present invention, a good focus error signal and tracking error signal are detected by utilizing the principle as described above.

  FIG. 9 is a plan view and a block diagram showing a first embodiment relating to a photodetector and a signal processing circuit according to the present invention. The package 20 of the photodetector 9 is provided with a light receiving area 210 in which each divided light receiving surface is divided into four square shapes represented by symbols a, b, c, and d as shown in the figure. Similarly to the light receiving region 210, a divided light receiving surface 211 is represented by symbols e, f, g, and h, and a four divided light receiving region 212 is represented by symbols i, j, k, and l. Has been placed. Further, the divided light receiving surface is represented by four divided light receiving regions 410 represented by symbols m, n, o, and p, the divided light receiving surface is represented by symbols q, r, and the divided light receiving surface is represented by symbols s. , T, a two-divided light receiving region 412 is arranged. Then, on the light receiving area 210, the disk reflected light of the on-disk light spot 100 is condensed to form a detection light spot 110. Similarly, the disk reflected light of the on-disk light spot 101 is collected on the light receiving area 211 and the reflected light of the on-disk light spot 102 is collected on the light receiving area 212 to form detection light spots 111 and 112, respectively. Yes.

  In addition, on the light receiving area 410, the disk reflected light of the on-disk light spot 300 is condensed to form a detection light spot 310. Similarly, the disk reflected light of the on-disk light spot 101 is collected on the light receiving area 411 and the reflected light of the on-disk light spot 102 is collected on the light receiving area 412 to form detection light spots 311 and 312. Yes.

  Here, in the first embodiment of the present invention, two different wavelength laser light sources (two-wavelength multi-lasers) separated by a minute distance d in the same housing, one diffraction grating, and one photodetector are used for optically. The system is configured. For this reason, the light receiving area sequence including the light receiving areas 200, 201, and 202 and the light receiving area sequence including the light receiving areas 410, 411, and 412 are arranged at different positions corresponding to the imaging system of the optical system. Further, with respect to the light receiving regions 201, 202, 411, 412 corresponding to the ± 1st order diffracted light of each laser beam, the interval between the light receiving regions 411, 412 corresponding to the laser light source having a large wavelength is the light beam in the diffraction grating 3. The arrangement is almost proportional to the diffraction angle.

  Each detection current detected by photoelectric conversion on each of the light receiving surfaces a, b, c, d is converted into a voltage by current-voltage conversion amplifiers 40, 41, 42, 43 provided in the package 20 of the photodetector 9. Each is converted and sent to the output terminal of the photodetector 9. Similarly, the light receiving surfaces e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, and t output lines are current-voltage conversion amplifiers 44, 45, 46, 47, 48, 49, 50, 51, 80, 81, 82, 83, 84, 85, 86, 87. (Hereinafter, for the sake of simplicity, these voltage-converted detection signals are given the same symbols as the light receiving surface on which the detection signals are detected.) After all, the 20 output terminals of the photodetector 9 Are output as a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, respectively. .

  Next, the arithmetic circuit will be described. Of the 20 detection signals output from the output terminal of the photodetector 9, signals (a + c) − (b + d) are output from the output signals a, b, c, and d by the adders 52 and 53 and the subtractor 54. The signal (a + d) − (b + c) is output by the adders 55 and 56 and the subtractor 57. Here, the signal (a + c) − (b + c) corresponds to a focus error signal of the on-disk light spot 100 detected by a so-called astigmatism method. Further, (a + d) and (b + c) correspond to the detected light quantity in each region when the detection light spot 110 is divided into two in the tracking direction (radial direction) of the disk, and the difference signal (a + d) between these two signals. -(B + c) corresponds to the tracking error signal of the light spot 100 on the disc detected by the so-called push-pull method.

  Further, a phase difference detection circuit 77 is connected to the output signals a, b, c, and d. By this circuit, a tracking error of the light spot 100 on the disc by the so-called phase difference detection method (differential phase detection method) is detected. A signal is also detected. Since this phase difference detection method is already a known technique, a detailed description thereof is omitted here.

  Further, by generating the sum signal DVD-RF of the output signals a, b, c, and d by the adder 76, the information signal recorded on the optical disc can be reproduced by a predetermined signal reproduction circuit. Although not shown in the present embodiment, the adder 76 is stored in the package 20 of the photodetector 9, and the output terminal of the sum signal (a + b + c + d) is added to the signal output terminal of the photodetector 9. Is also possible.

  Further, from the output signals e, f, g, and h, signals (e + g) − (f + h) are output by the adders 58 and 59 and the subtractor 60, and the signals (e + h) are output by the adders 61 and 62 and the subtractor 63. -(F + g) is output. Similarly, from the output signals i, j, k, and l, signals (i + k) − (j + l) are output by the adders 64 and 65 and the subtractor 66, and signals (i + l) are output by the adders 67 and 68 and the subtractor 69. ) − (J + k) is output.

  The signals (e + g) − (f + h) and (i + k) − (j + l) are output as the signal (e + g + i + k) − (f + h + j + l) by the adder 70 and further amplified by the amplifier 71 at a predetermined amplification factor K1. The amplification factor K1 of the amplifier 71 is determined so that the signal (e + g + i + k) − (f + h + j + l) has substantially the same signal amplitude as the signal (a + c) − (b + d). This signal (e + g + i + k)-(f + h + j + l) corresponds to the sum signal of the focus error signals of the on-disk light spots 101 and 102 detected by the so-called astigmatism method.

  On the other hand, (e + h)-(f + g) and (i + l)-(j + k) are output by the adder 73 as a signal (e + h + i + l)-(f + g + j + k) and further amplified by the amplifier 74 at a predetermined amplification factor K2. The amplification factor K2 of the amplifier 74 is determined so that the signal (e + h + i + l) − (f + g + j + k) has substantially the same signal amplitude as the signal (a + d) − (b + c). This signal (e + h + i + l)-(f + g + j + k) corresponds to the difference between the total detected light amounts in the respective areas when the detection light spots 111 and 112 are divided into two in the disk tracking direction (radial direction). This corresponds to the sum of the tracking error signals of the spots 101 and 102 on the disc detected by the method. The signal output from the subtractor 75 is {(a + d) − (b + c)} − K2 · {(e + h + i + l) − (f + g + j + k)}. This signal corresponds to a signal obtained by subtracting the tracking error signals of the spots 101 and 102 on the disk obtained from the light receiving areas 201 and 202 from the tracking error signal of the spot 100 on the disk obtained from the light receiving area 200. .

  By the way, selector switches 78 and 79 are provided at the focus error signal output terminal and the tracking error signal output terminal of the signal processing circuit, respectively. This is provided for appropriately switching between a focus error signal and a tracking error signal used for controlling the actuator 7 according to the type of the optical disk as described below. That is, for example, when reproducing an optical disk having a continuous guide groove on the recording surface of the disk, such as a DVD-RAM disk, first, the changeover switch 78 is switched as shown in FIG. The signal {a + c) − (b + d)} and the signal K1 · {(e + i + g + k) − (h + l + f + j)} output from the amplifier 71 are added by the adder 72 {{a + c) − (b + d)} + K1 · {( e + i + g + k)-(h + 1 + f + j)} is output as a focus error signal. As described above, this signal corresponds to a signal obtained by adding together the sum signal amplitudes of the focus error signal of the light spot 100 on the optical disc by the astigmatism method and the focus error signals of the light spots 101 and 102. Therefore, as described above, this signal is a good focus error signal in which the leakage error of the focus error signal due to diffraction in the guide groove is largely eliminated.

  Next, for the tracking error signal, the changeover switch 79 is switched to output a signal {(a + d) − (b + c)} − K2 · {(e + h + i + l) − (f + g + j + k)}. This is obtained by subtracting the sum signal of the tracking error signals of the spots 101 and 102 on the disk obtained from the light receiving areas 211 and 212 from the tracking error signal of the spot 100 on the disk obtained from the light receiving area 210 as described above. Correspondingly, this method is called a differential push-pull method. Therefore, although this signal is detected by the push-pull method, it is a good tracking error signal in which the offset due to the displacement of the objective lens is greatly eliminated.

  On the other hand, signals (m + o) − (n + p) are output from the output signals m, n, o, and p by the adders 88 and 89 and the subtracter 90, and the signal (m + p) is output by the adders 91 and 92 and the subtractor 93. -(N + o) is output. Here, the signal (m + o) − (n + p) corresponds to a focus error signal of the on-disk light spot 300 detected by a so-called astigmatism method. Further, (m + p) and (n + o) correspond to the detected light quantity in each region when the detection light spot 310 is divided into two in the tracking direction (radial direction) of the disk, and the difference signal (m + p) between these two signals. -(N + o) corresponds to the tracking error signal of the light spot 300 on the disc detected by the so-called push-pull method.

  Further, by generating the sum signal CD-RF of the output signals m, n, o, and p by the adder 99, the information signal recorded on the optical disc can be reproduced by a predetermined signal reproduction circuit. Although not shown in the present embodiment, the adder 99 is stored in the package 20 of the photodetector 9, and the output terminal of the sum signal (m + n + o + p) is added to the signal output terminal of the photodetector 9. Is also possible.

  Further, from the output signals q, r, s, t, a tracking error signal (q-r) detected from the subtractor 94 by the push-pull method, and a tracking error signal (s) detected from the subtractor 95 by the push-pull method. -T) is output, the signal (q + s)-(r + t) is output by the adder 96, and further amplified by the amplifier 97 at a predetermined amplification factor K3. The amplification factor K3 of the amplifier 97 is determined so that the signal (q + s)-(r + t) has substantially the same signal amplitude as the signal (m + p)-(n + o). Here, the signal (q + s) − (r + t) corresponds to the difference in the total detected light amount in each region when the detection light spots 311 and 312 are divided into two in the tracking direction (radial direction) of the disk. This corresponds to the sum of the tracking error signals of the spots 301 and 302 on the disc detected by the method. The signal output from the subtractor 98 is {(m + p) − (n + o)} − K3 · {(q + s) − (r + t)}. This signal corresponds to a signal obtained by subtracting the tracking error signals of the spots 101 and 102 on the disk obtained from the light receiving areas 411 and 412 from the tracking error signal of the spot 100 on the disk obtained from the light receiving area 410. This method is called a differential push-pull method. Therefore, although this signal is detected by the push-pull method, it is a good tracking error signal in which the offset due to the displacement of the objective lens is greatly eliminated.

  When playing back a read-only disc such as a DVD-ROM disc in which phase pits corresponding to the recording signal are provided on the disc, even if a signal based on the normal astigmatism method is used as the focus error signal, the disturbance is not disturbed. There is no effect. Further, a tracking error signal based on the phase difference detection method output from the phase difference detection circuit 77 can be used as the tracking error signal. Therefore, if the change-over switches 78 and 79 are switched so that (a + c)-(b + d) is output as the focus error signal and the tracking error signal output from the position difference detection circuit 77 is output as the tracking error signal, the read-only disc A desired error signal suitable for the above can be obtained. Also, with respect to a CD-ROM disc, good signal reproduction is possible by using an astigmatism method and a differential push-pull method.

  Here, the position adjustment of the detection light spot on the light detection surface will be described. FIG. 10 shows a light spot on the photodetector for DVD, and FIG. 11 shows a light spot on the photodetector for CD. In FIG. 10, detection light spots 110, 111, and 112 of the DVD are irradiated to predetermined positions in the light receiving areas 210, 211, and 212, respectively. In FIG. 11, CD detection light spots 310, 311, and 312 are irradiated to predetermined positions of the light receiving areas 410, 411, and 412, respectively. In the first embodiment of the present invention, the optical axis of the condensing optical system is set and adjusted based on the optical axis of the DVD. Therefore, the detection light spot on the CD is arranged at a position substantially proportional to the interval between the laser light sources with the optical axis of the DVD as the center. FIG. 12 shows a detection light spot on a CD with the DVD optical axis adjusted. The zero-order detection light spots 310 of the CD are arranged on the circumference centered on the position where the zero-order light spot 110 is arranged on the DVD, and the ± first-order detection light spots 311 and 312 of the CD are zero-order. Irradiated to the position diffracted around the detection light spot. By rotating the semiconductor laser 2 about the optical axis, the zero-order detection light spot 310 of the CD rotates in the direction of the arrow in FIG. 12, and thus the detection light spot position on the CD can be adjusted.

  Next, a second embodiment according to the present invention will be described with reference to FIG. The same symbols used in the drawings are the same as those used in the above description. The difference from the configuration of FIG. 9 is the configuration of the light receiving region in the package 21. In FIG. 13, the light receiving area for ± 1st order diffracted light used when reproducing a CD-R disc is also used as the light receiving area for ± 1st order diffracted light used when reproducing a DVD-RAM. . That is, when reproducing or recording a CD-R, by using the light receiving surfaces e, f, i, j of the light receiving areas 213, 214, the same as described in the first embodiment. It is possible to detect a focus error signal and a tracking error signal. With such a configuration, the number of signal lines output from the light receiving surface can be reduced by four, and an actual photodetector can be easily and inexpensively made. Even when a DVD-RAM disc is played back, the light from the optical disc does not return to the portion where the area of the light receiving surface is enlarged, so it goes without saying that the same effect as in the first embodiment can be obtained.

  Next, a third embodiment relating to the photodetector and the signal processing circuit according to the present invention will be described with reference to FIG. The same symbols used in the drawings are the same as those used in the above description. The difference from the configuration of FIG. 9 is the configuration of the light receiving region in the package 22. In FIG. 14, the light receiving area for ± first-order diffracted light used for reproducing a DVD-RAM disk is deleted. For this reason, the influence of the disturbance remains in the focus error signal by the astigmatism method, and it is difficult to reproduce the DVD-RAM disc. When playing back a CD-R disc, it is possible to generate a tracking error signal by the differential push-pull method, and furthermore, it is possible to use a diffraction grating exclusively for the CD-R. The position of the folded light on the optical disk 2 can be easily adjusted by using the rotation of the diffraction grating.

  Next, a fourth embodiment relating to the photodetector and the signal processing circuit according to the present invention will be described with reference to FIGS. The same symbols used in the drawings are the same as those used in the above description. FIG. 15 shows the arrangement of light spots on the CD-ROM disc. The recording pits 400 are arranged in the track direction and are formed at intervals of Tp3 (1.6 μm). The light spots on the optical disk 10 are three spots of 0th order light and ± 1st order diffracted light, and the spot 301 of + 1st order diffracted light and the spot 302 of −1st order diffracted light are from the spot 300 of 0th order light to Tp3. It arrange | positions in the position which left | separated the space | interval of Tp32 (0.4 micrometer) equivalent to 1/4. FIG. 16 is a plan view and a block diagram regarding a photodetector and a signal processing circuit. The difference from the configuration of FIG. 14 is the configuration of the light receiving region in the package 23. In FIG. 16, a light receiving area for receiving ± first-order diffracted light of the CD side detection system is constituted by one light receiving surface 413, 414, respectively. Outputs from the light receiving surfaces 413 and 414 are output from the current-voltage conversion amplifiers 84 and 86 and output as a difference signal of ± first-order diffracted light by using the subtractor 94. As a result, by combining with the spot arrangement on the optical disk 10 shown in FIG. 15, it is possible to detect the tracking error signal by the three-beam method.

Next, a fifth embodiment relating to the photodetector and the signal processing circuit according to the present invention will be described with reference to FIGS. The same symbols used in the drawings are the same as those used in the above description. FIG. 17 shows the configuration of the optical system in the fifth embodiment. The difference from the first embodiment shown in FIG. 2 is that two laser light sources having different wavelengths are arranged in the same casing. In the semiconductor laser 17 (two-wavelength multi-laser), the points where the polarization directions of the laser beams emitted from the respective laser light sources are substantially perpendicular to each other, and the two polarization diffraction gratings 18 and 19 are optical paths. It is a point arranged inside. The diffraction directions of the polarization diffraction gratings 18 and 19 due to the polarization of each other are arranged vertically, and the diffraction directions of the polarizations are arranged so as to coincide with the polarization directions of the corresponding laser light sources. Therefore, the grating groove and angle of each polarization diffraction grating can be set freely. FIG. 18 is a plan view and a block diagram relating to a photodetector and a signal processing circuit. The difference from the configuration of FIG. 14 is the configuration of the light receiving region in the package 24. In FIG. 18, the light receiving area for receiving the ± first-order diffracted light of the CD side detection system is constituted by one light receiving surface 413, 414 as in FIG. Outputs from the light receiving surfaces 413 and 414 are output from the current-voltage conversion amplifiers 84 and 86 and output as a difference signal of ± first-order diffracted light by using the subtractor 94. As described above, since the polarization diffraction gratings 18 and 19 can be designed independently of each other, for example, the discs are independent of the DVD-RAM optical disc 1 and the CD-ROM optical disc 10, for example. An upper spot arrangement is possible. Therefore, it is possible to select the spot arrangement shown in FIG. 4 on the DVD side, and it is possible to detect a focus error signal and a tracking error signal necessary for reproducing a DVD-ROM or DVD-RAM disc. On the CD side, the spot arrangement shown in FIG. 15 can be selected, and the tracking error signal can be detected by the three-beam method.

  Next, a sixth embodiment relating to the detection light spot adjusting method according to the present invention will be described with reference to FIGS. The same symbols used in the drawings are the same as those used in the above description. FIG. 19 shows a configuration diagram of the optical pickup in the sixth embodiment. The difference from the first embodiment shown in FIG. 2 is that the half mirror of the condensing optical system and the photodetector 9 are different. The dichroic diffraction grating 30 is disposed in the optical path between them. The dichroic diffraction grating 30 has such a characteristic that only the light beam of the CD is diffracted, and diffracts only the reflected light from the optical disk 10 during CD reproduction. Therefore, the irradiation state of the detection light spot on the detector 9 in the DVD is the same as that shown in FIG. On the other hand, in the CD, the light beam is diffracted by the dichroic diffraction grating 30 and the detection light spot is irradiated as shown in FIG. In FIG. 20, detection light spots 315, 316, and 317 are zero-order light detection spots on the dichroic diffraction grating 30, and detection light spots 318a, 319a, and 320a are + 1st-order light detection spots and detection light spots 318b on the dichroic diffraction grating 30. Reference numerals 319b and 320b denote -1st order light detection spots on the dichroic diffraction grating 30. In the sixth embodiment, the light detection areas 410, 411, and 412 are irradiated with the light detection spots 318a, 319a, and 320a that are + 1st order diffracted light from the dichroic diffraction grating 30. Therefore, as shown in FIG. 21, the light detection spots 318a, 319a, and 320a can be moved closer to or away from the zero-order detection light spot by moving the dichroic diffraction grating 30 back and forth along the optical axis. Yes, it is possible to rotate around the zero-order detection light spot 315 by rotating the dichroic diffraction grating 30 as shown in FIG.

  Therefore, the irradiation position of the CD detection light spot can be adjusted by adjusting the position and rotation of the dichroic diffraction grating 30. As a result, the irradiation position of the CD detection light spot can be within the light receiving range of the light receiving region.

  Further, as shown in FIG. 21, the light detection spots 318a, 319a, and 320a can be moved closer to or away from the zero-order detection light spot by moving the dichroic diffraction grating 30 back and forth along the optical axis. For this reason, the position of the light receiving region in the detector 9 can be set to a desired arrangement. That is, by adjusting the position of the dichroic diffraction grating 30, it is possible to increase the degree of freedom in designing the arrangement of the light receiving regions in the detector 9. This example is shown using FIG. 10, FIG. 20, and FIG. In FIG. 20, the light detection areas 210, 211, and 212 are irradiated with the detection light spot of the DVD (see FIG. 10), and the light detection areas 410, 411, and 212 are irradiated with the detection light spot of the CD. 412. Here, FIG. 21 shows that by adjusting the position of the dichroic diffraction grating 30, the irradiation positions of the CD detection light spots 318 a, 319 a, and 320 a can be on the light receiving areas 410, 411, and 412. Furthermore, in FIG. 21, by adjusting the position of the dichroic diffraction grating 30, the irradiation positions of the CD detection light spots 318a, 319a, and 320a can be placed on the light receiving areas 210, 211, and 212.

  For example, first, the reflected light used for DVD detection (the zero-order light beam in the dichroic diffraction grating 30) is irradiated with a detection light spot on the detector 9, as shown in FIG. A detection light spot is irradiated to a predetermined position within a range where light can be received.

  Here, the predetermined position described above means that when the detection light spot is irradiated to the predetermined position, the detection light spot is detected, and the output signal output based on the detection is It is an irradiation position in the light receiving region where an output signal that can be used for signal processing or the like can be output.

  That is, in the irradiation state of the detection light spot on the detector 9 shown in FIG. 10, the detection light spot is detected, and the signal output output based on the detection can be used for subsequent signal processing and the like. The position of the detector 9 and the like is determined so as to be the irradiation position in such a light receiving region. On the other hand, at this time, the reflected light (+ 1st order light or -1st order light beam in the dichroic diffraction grating 30) used for CD detection is caused in the light receiving region as described for the DVD due to manufacturing variation. The detection light spot is not always applied to a predetermined position within the range where light can be received. Therefore, when the position of the detector 9 is determined with reference to the reflected light used for the DVD detection, the reflected light used for the CD detection is predetermined within the light receiving range where light can be received in the light receiving area. The detection light spot is not always irradiated to the position.

  Here, since the reflected light used for detecting the CD is diffracted light in the dichroic diffraction grating 30, the dichroic diffraction grating 30 is moved back and forth along the optical axis or rotated around the optical axis. It is possible to make the irradiation position of the reflected light used for detecting the light approach or move away from the light receiving area of the DVD. Accordingly, by moving the dichroic diffraction grating 30 back and forth along the optical axis or rotating it around the optical axis, the irradiation position of the reflected light used for CD detection is a predetermined position within the range where light can be received in the light receiving area. It becomes possible to adjust so that. In this adjustment, the reflected light used for detecting the DVD is 0th-order light in the dichroic diffraction grating 30, so that the reflected light is irradiated so as to irradiate a predetermined position within the light receiving area.

  In the above description, the dichroic diffraction grating 30 does not diffract the DVD light beam but diffracts only the CD light beam. However, the present invention is not limited to this.

  That is, as in the present embodiment, the reflected light used for DVD detection uses the 0th order light in the dichroic diffraction grating 30, and the reflected light used for CD detection uses the + 1st order light or −1 in the dichroic diffraction grating 30. In the case of using the next light, the dichroic diffraction grating 30 may have a function of diffracting both the DVD and CD light beams.

  Next, by moving the dichroic diffraction grating 30 back and forth along the optical axis, or by rotating the dichroic diffraction grating 30 around the optical axis, the irradiation position of the reflected light used for detecting the CD or DVD is within the range where light can be received in the light receiving region. In the following, an embodiment showing the adjustment to be a predetermined position in will be described.

  In the seventh to ninth embodiments shown below, the DPP signal can be detected on both the CD and DVD discs by using one three-spot diffraction grating by using the relationship of the above formula (1). A simple light beam.

FIG. 23 is a schematic configuration diagram of an optical pickup device according to a seventh embodiment of the present invention. A laser light source 7001 is a two-wavelength multi-laser light source in which two semiconductor laser chips having different oscillation wavelengths (oscillation wavelengths of 650 nm band and 780 nm band) are provided in the same package.
For example, when reproducing a high-density optical disk such as a DVD-ROM, a light beam having a wavelength of 650 nm is emitted from a two-wavelength multi-laser light source 7001. This light beam passes through a diffraction grating 7009 for three spots, is reflected by a half mirror 7003 arranged at an angle of 45 ° with respect to the optical axis, and is parallel by a collimator lens 7005 via a rising mirror 7004. It is converted into a light beam and reaches the objective lens 7006. The objective lens 7006 is held by an actuator 7007, and a light beam is condensed on the optical disc 7008 to form a light spot. The light beam reflected from the optical disc 7008 follows the same optical path as the forward path, and enters the half mirror 7003 through the objective lens 7006, the collimator lens 7005, and the rising mirror 7004. The light beam that has passed through the half mirror 7003 reaches the hologram element 7010. The hologram element 7010 separates and generates a + 1st order diffracted light beam or a −1st order diffracted light beam with respect to a light beam having a wavelength of 780 nm band, as will be described later, and either one of these diffracted light beams is predetermined in the photodetector 7002. The grating groove pattern is designed so as to have a function of condensing in the light receiving region, but naturally, a 0th-order light beam and a ± 1st-order diffracted light beam are generated even when a light beam having a wavelength of 650 nm is incident. However, in this embodiment, it is designed such that only the 0th-order light beam that has been transmitted straight through the hologram element 7010 is incident on a predetermined light receiving region in the photodetector 7002 through the detection lens 7011. The detection lens 7011 is a lens in which a cylindrical lens and a concave lens are combined. The detection lens 7011 is added to the zero-order light beam by a function of condensing the zero-order light beam in a predetermined light receiving region in the photodetector 7002 and a half mirror 7003. 23 has a function of canceling the coma and the astigmatism in the y direction and the x direction in FIG. 23 and generating a predetermined amount of astigmatism in a direction inclined by 45 ° with respect to the y axis direction in the xy plane. doing.
Next, when reproducing a conventional optical disk such as a CD-ROM, a two-wavelength multi-laser light source 7001 emits a light beam having a wavelength of 780 nm. As described above, this light beam passes through the diffraction grating 7009 for three spots and is diffracted and separated into 0th order diffracted light and ± 1st order diffracted light. At this time, each light beam is, for example, a quarter track pitch on the optical disc 7008. Diffraction separation is performed so as to form a light spot by shifting in the disk radial direction. The light beam that has passed through the diffraction grating 7009 is reflected by a half mirror 7003 disposed at an angle of 45 ° with respect to the optical axis, passes through a rising mirror 7004, is converted into a parallel light beam by a collimator lens 7005, and is an objective lens. 7006 is reached. The objective lens 7006 is held by an actuator 7007. As described above, the objective lens 7006 has a function of condensing a light beam having a wavelength of 650 nm on a DVD disk and a light beam having a wavelength of 780 nm on an optical disk 7008 such as a CD-ROM. At the same time to form a light spot by condensing the light.
The light beam reflected from the optical disk 7008 follows the same optical path as the forward path, enters the half mirror 7003 through the objective lens 7006, the collimator lens 7005, and the rising mirror 7004. After passing through the half mirror 7003, the hologram element 7010 is transmitted. To reach. The hologram element 7010 has a predetermined grating groove pattern, and diffracts and separates an incident light beam having a wavelength of 780 nm band with a predetermined diffraction efficiency to generate a ± first-order diffracted light beam. Astigmatism and coma generated in the + 1st order diffracted light beam or -1st order diffracted light beam by passing through 7011 are canceled, and this diffracted light beam passes through the detection lens 7011 and has a wavelength of 650 nm in the photodetector 7002. It has a function of condensing light to a predetermined light receiving area at a position different from the predetermined light receiving area to which the light beam reaches almost without aberration.

  In FIG. 21, by moving the dichroic diffraction grating 30 back and forth along the optical axis, the light detection spots 318a, 319a, and 320a can approach or separate from the zeroth-order detection light spot. I have already explained that.

  Therefore, also in FIG. 23, by moving the hologram element 7010 back and forth along the optical axis, it is possible to change the position in the photodetector 7002 where the light beam having the wavelength of 780 nm reaches. By using this fact, in FIG. 23, it is possible to adjust the irradiation position of the CD detection light spot in the photodetector 7002. In addition, by adjusting the position of the hologram element 7010, it is possible to increase the degree of freedom in designing the arrangement of the light receiving regions in the photodetector 7002. For example, the light receiving region in the photodetector 7002 where the light beam having a wavelength of 780 nm reflected from the optical disk arrives and the light receiving region in the photodetector 7002 where the light beam having a wavelength of 650 nm reach are arranged in the same straight line. Is also possible.

  Alternatively, both the light beam wavelength of 650 nm band reflected from the optical disc and the light beam of 780 nm band can be condensed on the same light receiving region in the photodetector 7002. That is, the light receiving region can be shared for both the light beam wavelength in the 650 nm band and the light beam in the 780 nm band.

First, in this embodiment, the three-spot diffraction grating 7009 has a spot interval δ of 0 in the disk radial direction as shown in FIGS. 24A and 24B on an optical disk 7008 such as a DVD-ROM or DVD-RAM as described above. The incident light beam having a wavelength of 650 nm is diffracted and separated so as to be about .67 μm to generate the 0th order light beam 7102a, the + 1st order light, and the −1st order light beams 7102b, 7102c, and the CD-ROM and CD-R On such an optical disc 7008, as shown in FIG. 24C, the incident light beam having a wavelength of 780 nm is diffracted and separated so that the spot interval δ ′ in the disc radial direction is about 0.8 μm, and the 0th-order light beam 7103a and + 1st-order light And −1st order light beams 7103b and 7103c to form a grating groove pattern diffraction grating. . The hologram pattern of the hologram element 7010 includes a zero-order light of a 650 nm wavelength light beam diffracted and separated by the hologram element 7010 and a + 1st order diffracted light or a −1st order diffracted light of a 780 nm wavelength light beam diffracted and separated by the hologram element 7010. As long as it has a function of guiding the light to a predetermined light receiving region in the light detector 7002, it may be an equidistant linear lattice groove pattern. Needless to say, even if the grating groove pattern of the hologram element 7010 is a predetermined unevenly curved pattern, it does not matter. When a grating having an appropriate unevenly spaced curved grating groove pattern is used, a predetermined wavefront aberration can be added to the + 1st order or −1st order diffracted light beam diffracted by this grating and guided into the photodetector 7002. Therefore, an unnecessary aberration component included in the + 1st order or -1st order diffracted light beam and the focal position of the + 1st order or -1st order diffracted light beam can be corrected, and a good detection light spot can be irradiated to the photodetector. .
Next, the light receiving surface pattern of the light receiving region in the photodetector 7002 in this embodiment will be described with reference to FIG. As shown in FIG. 25, the light-receiving surface pattern of the light-receiving area is arranged in a straight line with three light-receiving surfaces divided into four in a square shape and two divided into a total of 16 independent light-receiving surfaces. It has been configured. When reproducing a DVD-based disc, the reflected light from the spots 7102a, 7102b and 7102c on the optical disc in FIGS. 24A and 24B is incident on the respective light receiving areas as shown in FIG. 25A to form light spots 7112a, 7112b and 7112c. At the time of reproduction of the CD-type disc, the disc reflected light of the spots 7103a, 7103b, and 7103c on the optical disc in FIG. 24C is incident on the respective light receiving areas as shown in FIG. 25B to form light spots 7113a, 7113b, and 7113c. Here, of the diffracted and separated light generated in the three-spot diffraction grating 7009, the light receiving area 7020a is used as the light receiving area for detecting the 0th-order light beam both when reproducing the DVD disk and when reproducing the CD disk as shown in FIG. ing. However, among the diffracted and separated lights generated by the three-spot diffraction grating 7009, the light receiving areas for detecting the + first-order light beam or the -1st-order light beam are different light receiving areas when reproducing a DVD disc and when reproducing a CD disc. Is used. This is because the diffraction angle of the light beam by the diffraction grating is substantially proportional to the wavelength as described above, and therefore, the zero-order light beam and the ± first-order light beam in the 780 nm wavelength band separated by the three-spot diffraction grating 7009 are separated. This is because the spot interval on the surface of the photodetector 7002 is increased by about 1.2 (= 780 ÷ 650) times compared to the spot interval of the light beam having a wavelength of 650 nm. Therefore, although the spot interval on the surface of the photodetector 7002 is different between the DVD disk reproduction and the CD disk reproduction, different light receiving areas are used so that the differential push-pull method can be applied to both the DVD system and the CD system. The light beam is detected.

  Since the detection method of the focus error signal and the tracking error signal by such a photodetector has already been described, detailed description thereof is omitted, but the focus error signal is detected by an astigmatism method by an arithmetic circuit as shown in FIG. The tracking error signal is detected by a phase difference detection method (DPD method). Here, reference numerals 7040, 7041, 7042, 7043, 7044, 7045, 7046, 7047 in the figure denote current-voltage conversion amplifiers, and reference numerals 7048, 7049, 7050, 7051, 7052, 7053, 7054, 7055, 7056, 7057, 7058, 7059, 7063, and 7064 are adders, 7070, 7071, 7072, and 7073 are subtractors, 7090 and 7091 are changeover switches, 7080 is a phase difference detection circuit, and 7060 is an amplification factor K3. Reference numerals 7061 and 7062 respectively denote amplifiers having an amplification factor K4. Hereinafter, the same reference numerals in the drawings are common to those used in the above description.

  When reproducing a DVD-RAM disc, the operation circuit is switched to that shown in FIG. 27, and the focus error signal is disclosed in the differential astigmatism method (details are omitted as disclosed in Japanese Patent Application No. 11-171844). The tracking error signal is detected by a differential push-pull method (DPP method).

  Further, when reproducing CD-type discs such as CD-ROM and CD-R, the arithmetic circuit as shown in FIG. 17 is switched, the focus error signal is astigmatism, and the tracking error signal is differential push-pull (DPP). ) To detect.

  In this embodiment, the light receiving surface pattern of the light receiving region in the photodetector 7002 is divided into 16 parts as shown in FIG. 25, but naturally the light receiving surface pattern of the light receiving region in the present invention is such as this. It is not limited to the structure, and at least when receiving a DVD disc and when playing a CD disc, each light beam is incident on the same photodetector to detect various servo signals and information signals. As long as it is a surface pattern, any other light receiving area light receiving surface pattern may be applied to the present invention. Hereinafter, an embodiment in which the light receiving surface pattern of the light receiving region of the photodetector 7002 is changed will be described.

  The eighth embodiment of the present invention has the same configuration as the optical pickup device in the seventh embodiment, but the light receiving surface pattern of the light receiving area is divided into four in a square shape as shown in FIG. This is a configuration in which a total of 14 independent light receiving surfaces, which are divided into 5 light receiving surfaces and 2 divided into 5, are replaced with a linear arrangement. With such a light receiving surface pattern of the light receiving area, when detecting the + first order light beam or the −first order light beam among the diffraction separated light generated by the three-spot diffraction grating 7009, the DVD system disc reproduction and the CD system are detected. The same light receiving area can be used during disk reproduction, and the number of light receiving surfaces can be reduced.

  Regarding the detection method of the focus error signal and the tracking error signal by such a photodetector, the same detection method as that described in the seventh embodiment can be used, so that detailed explanation is omitted, but the DVD-ROM is omitted. When reproducing a disc, a focus error signal is detected by an astigmatism method using an arithmetic circuit as shown in FIG. 30, and a tracking error signal is detected by a phase difference detection method (DPD method).

  When reproducing a DVD-RAM disc, the operation circuit is switched to the arithmetic circuit as shown in FIG. 31, the focus error signal is detected by the differential astigmatism method, and the tracking error signal is changed to the differential push-pull method (DPP method). To detect.

  Further, when reproducing a CD-type disc such as a CD-ROM or CD-R, the operation circuit is switched to the arithmetic circuit as shown in FIG. 32, the focus error signal is the astigmatism method, and the tracking error signal is the differential push-pull method (DPP method). ) To detect.

  Next, another embodiment in which the light receiving surface pattern of the light receiving area in the seventh embodiment is changed will be described below.

  The ninth embodiment of the present invention has the same configuration as that of the optical pickup device in the seventh embodiment. However, the light receiving surface pattern of the light receiving area is divided into four squares as shown in FIG. A total of eight independent light receiving surfaces divided into two divided into two are replaced with a configuration in which the surfaces are arranged in a straight line. With such a configuration, the number of light receiving surfaces can be further reduced. The detection method of the focus error signal and the tracking error signal by such a photodetector can be the same detection method as that described in the seventh embodiment, so detailed description is omitted, but a DVD-ROM disc is used. When reproducing, a focus error signal is detected by an astigmatism method using an arithmetic circuit as shown in FIG. 34, and a tracking error signal is detected by a phase difference detection method (DPD method). Here, reference numeral 7065 in the figure denotes an amplifier having an amplification factor K3, reference numeral 7074 denotes a subtractor, and reference numeral 7092 denotes a changeover switch.

  When reproducing a CD-type disc such as a CD-ROM or CD-R, the operation circuit is switched to the arithmetic circuit as shown in FIG. 35, the focus error signal is the astigmatism method, and the tracking error signal is the differential push-pull method (DPP method). To detect.

  Further, another embodiment in which the light receiving surface pattern of the light receiving area is simplified will be described below.

  The tenth embodiment of the present invention has the same configuration as that of the optical pickup device in the seventh embodiment, but one light receiving surface in which the light receiving surface pattern of the light receiving area is divided into four in a square shape as shown in FIG. A total of six independent light receiving surfaces in which light receiving surfaces are respectively arranged on the surface and both ends thereof are replaced with a linear arrangement.

  Here, 7122a, 7122b, and 7122c in the figure indicate that three light beams diffracted and separated by the three-spot diffraction grating 7009 reflect the optical disk 7008 during the reproduction of the DVD disk, and are reflected on the light receiving region in the photodetector 7002. 7123a, 7123b, and 7123c reflect the three light beams diffracted and separated by the three-spot diffraction grating 7009 when the CD disk is reproduced, and the light received in the photodetector 7002 is reflected. It shows a state of focusing on the area. Further, the three-spot diffraction grating 7009 has a spot spacing in the radial direction of the disc on the optical disc 7008 such as a CD-ROM or CD-R of about 0.4 μm, which is a quarter of the track pitch of the information track. It has a function of diffracting and separating a light beam having a wavelength of 780 nm emitted from the second semiconductor laser light source. As a detection method of the focus error signal and the tracking error signal by such an optical pickup device, when reproducing a DVD-ROM disc, an arithmetic circuit as shown in FIG. 37 is used to convert the focus error signal into an astigmatism method. The tracking error signal is detected by a phase difference detection method (DPD method). Reference numeral 7093 in the drawing represents a changeover switch. When reproducing a CD-type disc such as a CD-ROM or CD-R, the arithmetic circuit as shown in FIG. 38 is switched to detect the focus error signal by the astigmatism method and the tracking error signal by the three-spot method. .

  Here, in the ninth and tenth embodiments, the light beam having a wavelength of 650 nm is not necessarily diffracted and separated by the three-spot diffraction grating 7009. Therefore, by controlling the groove depth of the three-spot diffraction grating 7009, the diffracted light efficiency of the light beam having a wavelength of 650 nm may be set to approximately 0%.

Further, by moving the hologram element 7010 in the seventh to tenth embodiments in the optical axis direction and rotating around the optical axis, the condensing position of the zero-order light passing through the hologram element 7010 in the photodetector 7002 is determined. Without changing, the condensing position in the photodetector 7002 of the + 1st order diffracted light (or −1st order diffracted light) diffracted and separated by the hologram element 7010 can be displaced. Therefore, the hologram element 7010 can adjust the relative position between the light receiving region in the photodetector 7002 and the light spot incident on the light receiving region so that the focus error signal and the tracking error signal are correctly output.
In addition, as described above, the grating engraved in the hologram element 7010 is sawtoothed to selectively improve the diffraction efficiency of the diffracted light necessary for signal detection, thereby increasing the light utilization efficiency for the light flux used for signal detection. Further, the possibility that unnecessary light not used for signal detection becomes a stray light component and jumps into the light receiving region to reduce the S / N ratio of signal detection can be reduced as much as possible. Note that when the grating engraved on the hologram element 7010 described in the above embodiments is sawtoothed, the grating sidewalls may be inclined as shown in FIG. 39, or the grating may be stepped. I do not care. Further, by making the diffraction efficiency of the hologram element 7010 dependent on the wavelength or polarization, the light utilization efficiency of the signal light can be further improved.

Here, a diffraction grating in which the diffraction efficiency has wavelength dependency will be described.
In general, in the case of a diffraction grating having a rectangular grating groove cross section, if the grating groove width of the diffraction grating 30 is defined as w, the grating period is defined as p, and the grating groove depth is defined as h as shown in FIG. The light intensity I0 of 7101a and the light intensity I1 of the + 1st order light 7101b (-1st order light 7101c) greatly depend on w, p, and h. When the light intensity of the incident light is 1, the following formula (2) I can express.

However, n is the refractive index of the transparent member 7030 engraved with the diffraction grating, and λ is the wavelength of the light beam incident on the diffraction grating. Therefore, from the equation (2), in order to generate more zero-order diffracted light with respect to incident light in the 650 nm band, the following equation (3)

In order to generate more first-order diffracted light with respect to incident light in the 780 nm band, the following equation (4)

It is sufficient to make the grating groove depth satisfying the above.
For example, when the grating groove depth is set so that (n−1) h = 1950 [nm], (n−1) h = 3 · 650 = 2.5 · 780 is obtained, and Expressions (3) and (4) ) At the same time, the light utilization efficiency can be improved.
By the way, the hologram element having such wavelength dependency or wavelength selectivity is not limited to an element realized by controlling the grating groove depth as described above. An element based on any principle as long as the diffraction efficiency of ± 1st order diffracted light is sufficiently high for light of 780 nm band and the efficiency of 0th order light is sufficiently high for light of 650 nm band But it does n’t matter.
Here, as an eleventh embodiment of the present invention, an example in which the light use efficiency of the signal detection light is improved by using a polarizing element in which the diffraction efficiency has polarization dependency will be described with reference to the drawings. FIG. 41 is a schematic configuration diagram of an optical pickup device as an eleventh embodiment of the present invention. The same parts as those in the seventh embodiment of the present invention shown in FIG. Unlike the seventh embodiment described above, this embodiment uses a polarization-dependent hologram 7012 instead of the hologram element 7010 and is combined with the polarization conversion element 7013 to improve the light use efficiency by using polarized light. Yes.
Here, as the polarization conversion element 7013, a wave plate that functions as a 5λ / 4 plate for a 650 nm band light beam is used. For example, the polarization-dependent hologram 7012 functions to diffract only a light beam having S-polarized light with a predetermined diffraction efficiency, and to transmit a light beam having P-polarized light having a polarization direction perpendicular thereto without being diffracted.
For example, when reproducing a high-density optical disk such as a DVD-ROM, an S-polarized light beam having a wavelength of 650 nm is emitted from a two-wavelength multi-laser light source 7001. This light beam passes through a three-spot diffraction grating 7009 and enters a dichroic half mirror 7003 arranged at an angle of 45 ° with respect to the optical axis. The light beam reflected by the dichroic half mirror 7003 enters the polarization conversion element 7013 through the rising mirror 7004.

Here, since the polarization conversion element 7013 functions as a 5λ / 4 plate for a light beam in the 650 nm band, the light beam incident as S-polarized light becomes a circularly polarized light beam after passing through the polarization conversion element 7013, and is collimated by the collimator lens 7005. It is converted into a parallel light beam and reaches the objective lens 7006. The objective lens 7006 is held by an actuator 7007, and a light spot can be formed by condensing a light beam on an optical disk 7008 such as a DVD-ROM. The light beam reflected by the optical disk 7008 travels in the reverse direction and enters the polarization conversion element 7013 through the objective lens 7006 and the collimator lens 7005. The light beam incident as circularly polarized light passes through the polarization conversion element 7013 and then becomes P-polarized light. It becomes a light beam, passes through the rising mirror 7004, passes through the dichroic half mirror 7003, and enters the polarization-dependent hologram 7012. The polarization-dependent hologram 7012 does not have a diffraction function for a P-polarized light beam and is merely a transparent member. Therefore, the P-polarized light beam incident on the polarization-dependent hologram 7012 is not diffracted and passes through as it is. Then, the light reaches a predetermined light receiving region in the photodetector 7002 through the detection lens 7011.
Next, when reproducing a conventional optical disk such as a CD-ROM, an S-polarized light beam having a wavelength of 780 nm is emitted from a two-wavelength multi-laser light source 7001. The light beam emitted from the two-wavelength multi-laser 1 passes through a three-spot diffraction grating 7009 and enters a dichroic half mirror 7003 arranged at an angle of 45 ° with respect to the optical axis. The light beam reflected by the dichroic half mirror 7003 enters the polarization conversion element 7013 through the rising mirror 7004. Here, since the polarization conversion element 7013 is an element that functions as a 5λ / 4 plate with respect to a light beam in the 650 nm band as described above, it substantially functions as a λ plate with respect to light in the wavelength of 780 nm band. Therefore, the light in the wavelength band of 780 nm is converted into a parallel light beam by the collimator lens 7005 while being S-polarized after passing through the polarization conversion element 7013, and reaches the objective lens 7006. The objective lens 7006 is held by an actuator 7007. As described above, a light spot is formed by condensing a light beam on an optical disk 7008 such as a CD-ROM and a function of condensing a light beam on a DVD disk. At the same time. The light beam reflected from the optical disk 7008 travels in the reverse direction and enters the polarization conversion element 7013 through the objective lens 7006 and the collimator lens 7005. After passing through the polarization conversion element 7013, it remains as an S-polarized light beam. The light passes through the mirror 7004, passes through the dichroic half mirror 7003, and enters the polarization-dependent hologram 7012. Since the polarization-dependent hologram 7012 has a function of diffracting an S-polarized light beam, the light beam is diffracted at a predetermined diffraction efficiency in the polarization-dependent hologram 7012, passes through a detection lens 7011, and is a photodetector 7002. Of these, a predetermined light receiving region at a position different from the predetermined light receiving region to which the light beam having a wavelength of 650 nm reaches is reached. With such a configuration, it is possible to efficiently guide only the light beam necessary for signal detection to the photodetector in both cases of DVD reproduction and CD reproduction, greatly improving light utilization efficiency and unnecessary. The stray light component can be removed.
Note that the positional relationship between the light spot and the light receiving surface in the light receiving region of the photodetector 7002 and the method for detecting the information signal, focus error signal, and tracking error signal during optical disc reproduction are the same as in the seventh embodiment.
Further, by moving the polarization-dependent hologram 7012 in the direction of the optical axis and rotating around the optical axis, light beams 7113a, 7113b in the 650 nm band that are detected by the photodetector 7002 as in the seventh embodiment, Without changing the focal position of the 7113c and the position on the light receiving surface, the focal positions of the 780 nm band light beams 7112a, 7112b and 7112c detected by the photodetector 7002 can be changed independently. Therefore, the detector adjustment and the focus error signal offset adjustment for the 650 nm band light beam and the 780 nm band light beam can be performed independently.
Furthermore, with respect to the dichroic half mirror 7003, S-polarized light is almost totally reflected and P-polarized light is almost 100% transmitted for 650 nm light, and S-polarized light is reflected and transmitted about 50% for 780 nm light. If it has, the utilization efficiency of light can be improved.

  By the way, although the arrangement position of the hologram element 7010 is between the half mirror 7003 and the detection lens 7011 in the embodiments described so far, it is not limited to this, and is in the optical path between the detection lens 7011 and the photodetector 7002. It may be. Further, in the embodiment described so far, the hologram element 7010 is configured to transmit the 0th-order light of the light beam having the wavelength of 650 nm and the light beam of the first-order diffracted light of the light beam having the wavelength of 780 nm in the photodetector 7002. However, the present invention is not limited to this. For example, the + 1st order diffracted light or the −1st order diffracted light of the light beam having the wavelength of 650 nm and the 0 light beam of the wavelength of 780 nm are completely reversed. Even a diffraction grating having a function of guiding the next light to a predetermined position in the photodetector 7002 may be used.

  FIG. 42 shows a schematic block diagram of an optical disc apparatus equipped with the optical pickup of the present invention. The optical pickup 508 includes, for example, the package 20 shown in FIG. 9 and the pickup device shown in FIGS. 24 and 41. Various detection signals detected here are servo signal generation circuits in the signal processing circuit. 504 and the information signal reproduction circuit 505. The servo signal generation circuit 504 generates a focus error signal and a tracking error signal suitable for each optical disk from these detection signals, and drives the objective lens actuator in the optical pickup 508 via the actuator drive circuit 503 based on this, Controls the position of the objective lens. The information signal reproduction circuit 505 reproduces the information signal recorded on the optical disc 1 from the detection signal. Part of the signals obtained by the servo signal generation circuit 504 and the information signal reproduction circuit 505 are sent to the control circuit 500. The control circuit 500 uses these various signals to determine the type of the optical disk 1 that is to be reproduced at that time, and drives either the DVD laser lighting circuit 507 or the CD laser lighting circuit 506 according to the determination result, Further, as described above, the servo signal generation circuit 504 has a function of switching the circuit configuration so as to select the servo signal detection method corresponding to the type of each optical disk. An access control circuit 502 and a spindle motor drive circuit 501 are connected to the control circuit 500, and the access direction position control of the optical pickup 508 and the rotation control of the spindle motor 509 of the optical disc 1 are performed.

It is a block diagram of the conventional optical pick-up. It is a block diagram of the optical pick-up in the 1st Embodiment of this invention. FIG. 3 shows a spot arrangement on the optical disc in the first embodiment of the present invention, and is a diagram in the case of a DVD-ROM disc. FIG. 3 shows a spot arrangement on the optical disc in the first embodiment of the present invention, and is a diagram in the case of a DVD-RAM disc. FIG. 2 shows a spot arrangement on an optical disc in the first embodiment of the present invention, and is a diagram in the case of a CD-R disc. It is a figure explaining intensity distribution of a light spot on an optical disc. It is a figure which shows the disturbance to a focus error signal. It is a figure which shows the tracking error signal by a push pull system. It is the top view and block diagram of the photodetector and signal processing circuit by the 1st Embodiment of this invention. It is a figure which shows the irradiation state of the detection light spot in DVD. It is a figure which shows the irradiation state of the detection light spot in CD. It is a figure which shows the irradiation state of the detection light spot of CD in the state where only DVD was adjusted. It is the top view and block diagram of the photodetector and signal processing circuit by the 2nd Embodiment of this invention. It is the top view and block diagram of the photodetector and signal processing circuit by the 3rd Embodiment of this invention. FIG. 10 shows a spot arrangement on an optical disc in a fourth embodiment of the present invention, and is a diagram in the case of a CD-ROM disc. It is the top view and block diagram of the photodetector and signal processing circuit by the 4th Embodiment of this invention. It is a block diagram of the optical pick-up in the 5th Embodiment of this invention. It is the top view and block diagram of the photodetector and signal processing circuit by the 5th Embodiment of this invention. It is a block diagram of the optical pick-up in the 6th Embodiment of this invention. It is a figure which shows the irradiation state of the detection light spot in CD in the 6th Embodiment of this invention. It is a figure which shows the parallel displacement of the detection light spot in CD in the 6th Embodiment of this invention. It is a figure which shows the rotational movement of the detection light spot in CD in the 6th Embodiment of this invention. The schematic block diagram of the optical pick-up apparatus which showed the 7th Embodiment of this invention. (A) Light spot position on DVD-ROM disk, (b) Light spot position on DVD-RAM disk, (c) Light spot position on CD-ROM, CD-R disk Light-receiving surface pattern diagrams of the light-receiving area of the photodetector in the seventh embodiment (a) During DVD playback, (b) During CD playback Schematic diagram of a signal processing circuit used for DVD-ROM playback in the seventh embodiment Schematic diagram of a signal processing circuit used during DVD-RAM playback in the seventh embodiment Schematic diagram of a signal processing circuit used for CD-ROM and CD-R playback in the seventh embodiment Light-receiving surface pattern diagrams of the light-receiving area of the photodetector in the eighth embodiment (a) During DVD playback, (b) During CD playback Schematic diagram of a signal processing circuit used for DVD-ROM playback in the eighth embodiment Schematic diagram of a signal processing circuit used for DVD-RAM playback in the eighth embodiment Schematic diagram of a signal processing circuit used for CD-ROM and CD-R playback in the eighth embodiment Light receiving surface pattern diagrams of the light receiving area of the photodetector in the ninth embodiment (a) During DVD playback, (b) During CD playback Schematic diagram of a signal processing circuit used for DVD-ROM playback in the ninth embodiment Schematic diagram of a signal processing circuit used for CD-ROM and CD-R playback in the ninth embodiment Light-receiving surface pattern diagrams of the light-receiving area of the photodetector in the tenth embodiment (a) During DVD playback, (b) During CD playback Schematic diagram of a signal processing circuit used for DVD-ROM playback in the tenth embodiment Schematic diagram of a signal processing circuit used for CD-ROM and CD-R playback in the tenth embodiment Diagram showing sawtoothing of diffraction grating (a) Schematic diagram with tilt on side of grating, (b) Schematic diagram with stepped grating Schematic which showed the diffraction of the light by the diffraction grating which has a rectangular-shaped grating groove cross section. The schematic block diagram of the optical pick-up apparatus which showed the 11th Embodiment of this invention. 1 is a schematic block diagram of an optical disc apparatus equipped with an optical pickup according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,10 ... Optical disk, 2, 11, 15, 17 ... Semiconductor laser, 3, 16, 30 ... Diffraction grating, 4 ... Half mirror, 5 ... Collimating lens, 6 ... Objective lens, 7 ... Actuator, 8 ... Drive coil, 9, 14 ... Photo detector, 12 ... Dichro prism, 18, 19 ... Polarized diffraction grating, 20, 21, 22, 23, 24 ... Package, 30 ... Dichro diffraction Lattice, 200 ... Mark, 201 ... Pit, 100, 101, 102, 300, 301, 302, 303, 304 ... Light spot on disk, 110, 111, 112, 310, 311, 312, 313, 314, 315, 316, 317, 318, 319, 320 ... detection light spot, 200 ... recording pit, 201, 400 ... recording mark, 202, 4 01... Guide groove, 203 and 402... Guide groove, 210, 211, 212, 213, 214, 410, 411, 412... Light receiving area, 500... Control circuit, 501. ... Access control circuit, 503 ... Actuator drive circuit, 504 ... Servo signal generation circuit, 505 ... Information signal reproduction circuit, 506 ... CD laser lighting circuit, 507 ... DVD laser lighting circuit, 508 ... Optical pickup, 509... Spindle motor, 7001... Laser light source, 7002... Photodetector, 7003... Half mirror, 7004 ... Rising mirror, 7005 ... Collimator lens, 7006. Actuator, 7008 ... Optical disc, 7009 ... 3 spots Diffraction grating, 7010 ...... hologram element, 7011 ...... detection lens, 7012 ...... polarization dependent hologram 7013 ...... polarization conversion element.

Claims (38)

The light beam emitted from the first, second, or both laser light sources is branched into at least three light beams and irradiated to the first or second optical information recording medium. In a photodetector for detecting the reflected light beam,
A light receiving region to which a light beam reflected by the first optical information recording medium is irradiated is divided into four, and a first light receiving region having four light receiving surfaces;
A light receiving area to which the light beam reflected by the second optical information recording medium is irradiated is divided into four, and a second light receiving area having four light receiving surfaces;
A light receiving region irradiated with the light beam reflected by the first optical information recording medium is divided into two parts, each including a third and a fourth light receiving region each having two light receiving surfaces;
Outputting a signal capable of generating a focus error signal by the astigmatism method from the first or second or both light receiving regions;
Alternatively, a signal that can independently generate a push-pull tracking error signal from the first, second, or both light receiving regions is output,
Alternatively, a signal that can generate a tracking error signal by a differential phase detection method from the first, second, or both light receiving regions is output,
Alternatively, the photodetector outputs a signal capable of generating a tracking error signal by a push-pull method independently from each of the third, fourth, or both light receiving regions. The light beam emitted from the first, second, or both laser light sources is branched into at least three light beams and irradiated to the first or second optical information recording medium. In a photodetector for detecting the reflected light beam,
A light receiving region to which a light beam reflected by the first optical information recording medium is irradiated is divided into four, and a first light receiving region having four light receiving surfaces;
A light receiving area to which the light beam reflected by the second optical information recording medium is irradiated is divided into four, and a second light receiving area having four light receiving surfaces;
A light receiving area irradiated with a light beam reflected by the first optical information recording medium is divided into four parts, each including a third and a fourth light receiving area each having four light receiving surfaces;
Outputting a signal capable of generating a focus error signal by the astigmatism method from the first, second or both light receiving regions;
Alternatively, a signal that can independently generate a push-pull tracking error signal from the first, second, or both light receiving regions is output,
Alternatively, a signal that can generate a tracking error signal by a differential phase detection method from the first, second, or both light receiving regions is output,
Alternatively, a signal capable of generating a focus error signal by an astigmatism method independently from each of the third, fourth, or both light receiving regions is output,
Alternatively, the photodetector outputs a signal capable of generating a tracking error signal by a push-pull method independently from each of the third, fourth, or both light receiving regions. The photodetector according to claim 2.
And a fifth and sixth light receiving regions irradiated with the light beam reflected by the second optical information recording medium, and generating a tracking error signal by a three-beam method from the fifth and sixth light receiving regions. A photodetector that outputs a signal that can be generated. The photodetector according to claim 2.
A light receiving area irradiated with a light beam reflected by the second optical information recording medium is divided into two parts, each including a fifth and a sixth light receiving area each having two light receiving surfaces. A photodetector that outputs a signal capable of generating a tracking error signal by a push-pull method independently from each of the sixth or both light receiving regions. The photodetector according to claim 2.
The light receiving area irradiated with the light beam reflected by the second optical information recording medium is divided into four parts, each including five and sixth light receiving areas each having four light receiving surfaces, A signal that can generate a focus error signal by the astigmatism method is output independently from each of the sixth or both light receiving regions, or a tracking error by the push-pull method is independently generated from each of the fifth, sixth, or both light receiving regions. A photodetector that outputs a signal capable of generating a signal. The photodetector of claim 1.
And a fifth and sixth light receiving regions irradiated with the light beam reflected by the second optical information recording medium, and generating a tracking error signal by a three-beam method from the fifth and sixth light receiving regions. A photodetector that outputs a signal that can be generated. A semiconductor laser having a first or second or both laser sources;
A light branching element that branches the light beam emitted from the first, second, or both laser light sources into at least three light beams;
A condensing optical system for irradiating the first or second optical information recording medium with a light beam including the three light beams;
An optical pickup comprising: the photodetector according to claim 1, which detects a light beam reflected by the optical information recording medium. A semiconductor laser having a first or second or both laser sources;
A light branching element that branches the light beam emitted from the first, second, or both laser light sources into at least three light beams;
A condensing optical system for irradiating the first or second optical information recording medium with a light beam including the three light beams;
An optical pickup comprising: the photodetector according to claim 2, which detects a light beam reflected by the optical information recording medium. A semiconductor laser having a first or second or both laser sources;
A light branching element that branches the light beam emitted from the first, second, or both laser light sources into at least three light beams;
A condensing optical system for irradiating the first or second optical information recording medium with a light beam including the three light beams;
An optical pickup comprising: the photodetector according to claim 3, which detects a light beam reflected by the optical information recording medium. A semiconductor laser having a first or second or both laser sources;
A light branching element that branches the light beam emitted from the first, second, or both laser light sources into at least three light beams;
A condensing optical system for irradiating the first or second optical information recording medium with a light beam including the three light beams;
An optical pickup comprising: the photodetector according to claim 4, which detects a light beam reflected by the optical information recording medium. A semiconductor laser having a first or second or both laser sources;
A light branching element that branches the light beam emitted from the first, second, or both laser light sources into at least three light beams;
A condensing optical system for irradiating the first or second optical information recording medium with a light beam including the three light beams;
The photodetector according to claim 5 for detecting a light beam reflected by the optical information recording medium;
An optical pickup comprising: A semiconductor laser having a first or second or both laser sources;
A light branching element that branches the light beam emitted from the first, second, or both laser light sources into at least three light beams;
A condensing optical system for irradiating the first or second optical information recording medium with a light beam including the three light beams;
An optical pickup comprising: a photodetector according to claim 6 for detecting a light beam reflected by the optical information recording medium. The optical pickup according to claim 7, wherein a signal is detected from the optical information recording medium;
A servo signal generation circuit that generates a focus error signal or a tracking error signal from the detection signal detected by the optical pickup;
An actuator drive circuit for controlling the position of the objective lens actuator of the optical pickup from the focus error signal or the tracking error signal;
An information signal reproducing circuit for reproducing an information signal recorded on an optical information recording medium from the detection signal;
An access control circuit for controlling an access direction position of the optical pickup;
A spindle motor drive circuit for rotating the optical information recording medium, and an optical information reproducing apparatus. The optical pickup according to claim 8, wherein a signal is detected from the optical information recording medium;
A servo signal generation circuit that generates a focus error signal or a tracking error signal from the detection signal detected by the optical pickup;
An actuator drive circuit for controlling the position of the objective lens actuator of the optical pickup from the focus error signal or the tracking error signal;
An information signal reproducing circuit for reproducing an information signal recorded on an optical information recording medium from the detection signal;
An access control circuit for controlling an access direction position of the optical pickup;
A spindle motor driving circuit for rotating the optical information recording medium;
An optical information reproducing apparatus comprising: The optical pickup according to claim 9, wherein a signal is detected from the optical information recording medium;
A servo signal generation circuit that generates a focus error signal or a tracking error signal from the detection signal detected by the optical pickup;
An actuator drive circuit for controlling the position of the objective lens actuator of the optical pickup from the focus error signal or the tracking error signal;
An information signal reproducing circuit for reproducing an information signal recorded on an optical information recording medium from the detection signal;
An access control circuit for controlling an access direction position of the optical pickup;
A spindle motor drive circuit for rotating the optical information recording medium, and an optical information reproducing apparatus. The optical pickup according to claim 10 for detecting a signal from the optical information recording medium;
A servo signal generation circuit that generates a focus error signal or a tracking error signal from the detection signal detected by the optical pickup;
An actuator drive circuit for controlling the position of the objective lens actuator of the optical pickup from the focus error signal or the tracking error signal;
An information signal reproducing circuit for reproducing an information signal recorded on an optical information recording medium from the detection signal;
An access control circuit for controlling an access direction position of the optical pickup;
A spindle motor drive circuit for rotating the optical information recording medium, and an optical information reproducing apparatus. The optical pickup according to claim 11, wherein a signal is detected from the optical information recording medium;
A servo signal generation circuit that generates a focus error signal or a tracking error signal from the detection signal detected by the optical pickup;
An actuator drive circuit for controlling the position of the objective lens actuator of the optical pickup from the focus error signal or the tracking error signal;
An information signal reproducing circuit for reproducing an information signal recorded on an optical information recording medium from the detection signal;
An access control circuit for controlling an access direction position of the optical pickup;
A spindle motor drive circuit for rotating the optical information recording medium, and an optical information reproducing apparatus. The optical pickup according to claim 12, wherein a signal is detected from the optical information recording medium;
A servo signal generation circuit that generates a focus error signal or a tracking error signal from the detection signal detected by the optical pickup;
An actuator drive circuit for controlling the position of the objective lens actuator of the optical pickup from the focus error signal or the tracking error signal;
An information signal reproducing circuit for reproducing an information signal recorded on an optical information recording medium from the detection signal;
An access control circuit for controlling an access direction position of the optical pickup;
A spindle motor drive circuit for rotating the optical information recording medium, and an optical information reproducing apparatus.   Among the plurality of light spots respectively irradiated on the first and second optical information recording media, the light spot interval in the direction perpendicular to the track in at least one set of light spots has a track in each optical information recording medium. The ratio of the track pitch in the first and second optical information recording media and the ratio of the wavelengths in the first and second laser light sources are approximately equal to one half of the pitch. Item 7. The photodetector according to any one of items 1 to 6. The photodetector of claim 1.
The light receiving area irradiated with the light beam reflected by the first optical information recording medium is divided into four, and the first light receiving area having four light receiving surfaces is the first division in which the light receiving areas intersect each other. The light receiving area is divided into four by the line and the second dividing line, and the light receiving area irradiated with the light beam reflected by the second optical information recording medium is divided into four, and the first light receiving surface has four light receiving surfaces. The light receiving area of 2 is divided into four by a third dividing line and a fourth dividing line that intersect each other. A semiconductor laser having a first or second or both laser sources;
A light branching element that branches the light beam emitted from the first, second, or both laser light sources into at least three light beams;
A condensing optical system that condenses the light beams including the three light beams onto different first or second optical information recording media and irradiates independent light spots at predetermined positions on the optical information recording media. When,
A first light receiving region provided so that a first position irradiated with a light beam reflected by the first optical information recording medium is within a light receiving range;
A photodetector having a second light receiving region provided so that a second position irradiated with the light beam reflected by the second optical information recording medium is within a light receiving range;
A light detection optical system that guides the light beam reflected by the first optical information recording medium or the light beam reflected by the second optical information recording medium to a predetermined position of the photodetector. Features an optical pickup. The optical pickup according to claim 21, wherein
Relative relation between the first position where the light beam reflected by the first optical information recording medium is irradiated and the second position where the light beam reflected by the second optical information recording medium is irradiated To change the general position,
The light detecting optical system guides the light beam reflected by the first optical information recording medium or the light beam reflected by the second optical information recording medium to the photodetector. pick up. The optical pickup according to claim 21, wherein
Reflected by the first light receiving area and the second optical information recording medium provided so that the first position irradiated with the light beam reflected by the first optical information recording medium is within the light receiving range. The light detection optical system is configured so that the second optical receiving area is provided at a position different from the second light receiving area provided so that the second position irradiated with the light beam is within the light receiving range. An optical pickup for guiding a light beam reflected by an information recording medium or a light beam reflected by the second optical information recording medium to the photodetector. The optical pickup according to claim 21, wherein
Relative relation between the first position where the light beam reflected by the first optical information recording medium is irradiated and the second position where the light beam reflected by the second optical information recording medium is irradiated The light reflected by the first optical information recording medium so that the first light receiving area and the second light receiving area are arranged in a straight line by changing the position of the first light receiving area. An optical pickup characterized in that a beam or a light beam reflected by the second optical information recording medium is guided to the photodetector. The optical pickup according to claim 21, wherein
Relative relation between the first position where the light beam reflected by the first optical information recording medium is irradiated and the second position where the light beam reflected by the second optical information recording medium is irradiated By changing the general position, so that the first light receiving region and the second light receiving region are the same position,
The light detecting optical system guides the light beam reflected by the first optical information recording medium or the light beam reflected by the second optical information recording medium to the photodetector. pick up. First and second semiconductor laser light sources having different oscillation wavelengths from each other;
Condensing optics for condensing the first light beam emitted from the first semiconductor laser light source and the second light beam emitted from the second semiconductor laser light source at predetermined positions on the optical information recording medium, respectively. The system,
An optical pickup comprising a light detector having a predetermined detection surface and a light detection optical system for guiding the first and second light beams reflected from the optical information recording medium to a predetermined position of the light detector. In the device
The optical detection optical system guides the first light beam reflected from the optical information recording medium to a first detection surface region at a predetermined position of the optical detector, and reflects the optical information recording medium. And an optical pickup device having a function of guiding the second light beam to a second detection surface region at a position different from the first detection surface region in the photodetector.   27. The optical pickup device according to claim 26, wherein the first semiconductor laser light source and the second semiconductor laser light source are multi-laser light sources provided in the same package.   28. The optical pickup device according to claim 26, wherein the light detection optical system includes a hologram element having a linear or curved grating groove pattern.   The hologram element does not diffract the first light beam having a predetermined wavelength and diffracts the second light beam having a wavelength different from the first light beam with a predetermined diffraction efficiency. 30. The optical pickup device according to claim 28, wherein the optical pickup device is an element having the following.   The hologram element has polarization selectivity that diffracts a light beam having a polarization direction perpendicular to the polarization direction with a predetermined diffraction efficiency without diffracting the light beam having a predetermined polarization direction. Predetermined polarized light that is not diffracted by the hologram element in the optical paths of the first and second light beams emitted from the first and second semiconductor laser light sources, reflected from the optical information recording medium and directed to the hologram element 29. The optical pickup according to claim 28, further comprising a polarization conversion element that gives a direction to the first light beam and gives a polarization direction diffracted by the hologram element to the second light beam. apparatus.   The condensing optical system condenses the first light beam emitted from the first semiconductor laser light source and substantially diffracts it on a predetermined recording surface of a first optical information recording medium having a predetermined substrate thickness. A second optical disc having a function of satisfactorily narrowing to the limit and having a substrate thickness different from that of the first optical information recording medium by condensing the second light beam emitted from the second semiconductor laser light source; 31. The optical pickup device according to claim 26, wherein the optical pickup device has a function of satisfactorily narrowing to a diffraction limit substantially on a predetermined recording surface of an optical information recording medium.   32. The optical pickup device according to claim 26, wherein the first semiconductor laser light source is a semiconductor laser light source having a wavelength of 660 nm or less, and the first optical information recording medium has a substrate thickness of about 0.6 mm. The second semiconductor laser light source is a semiconductor laser light source having a wavelength of 780 nm to 790 nm, and the second optical information recording medium is an optical disk having a substrate thickness of about 1.2 mm. An optical pickup device characterized by that.   33. The optical pickup device according to claim 30, wherein the polarization conversion element functions as a 5λ / 4 plate for the first light beam emitted from the first semiconductor laser light source.   When detecting a focus error signal from the first light beam emitted from the first semiconductor laser light source and reflected from the first optical information recording medium, an astigmatism method is used, and the second semiconductor laser light source is 27. An astigmatism method, a knife edge method, or a beam size method is used when detecting a focus error signal from a second light beam that is emitted and reflected from the second optical information recording medium. 34. The optical pickup device according to any one of items 33 to 33.   When detecting a tracking error signal from a first light beam emitted from the first semiconductor laser light source and reflected from the first optical information recording medium, a differential phase detection method (Differential Phase Detection method) or a differential push pull When a tracking error signal is detected from a second light beam emitted from the second semiconductor laser light source and reflected from the second optical information recording medium, a push-pull method, a differential push-pull method, or three spots is used. 35. The optical pickup device according to claim 26, wherein a method is used.   36. The optical pickup apparatus according to claim 26, wherein the tracking error signal of the second optical information recording medium is detected by a differential push-pull method, and the optical pickup device according to claim 26, wherein the second semiconductor laser light source emits the second semiconductor laser light source. The light beam is diffracted and separated into at least three light beams, and the spot interval of the three light beams is approximately equal to the track pitch of the optical information recording medium in the radial direction on the second optical information recording medium. A three-spot diffraction grating halved is provided, and the three-spot diffraction grating further diffracts and separates the first light beam emitted from the first semiconductor laser light source into at least three light beams. And a predetermined write-once or rewritable type light in the radial direction on the first optical information recording medium. Optical pickup device, characterized in that to approximately one half of the track pitch of the information recording medium.   36. The optical pickup apparatus according to claim 26, wherein the tracking error signal of the second optical information recording medium is detected by a differential push-pull method, and the optical pickup device according to claim 26, wherein the second semiconductor laser light source emits the second semiconductor laser light source. The light beam is diffracted and separated into at least three light beams, and the spot interval of the three light beams is tracked on the information track of the optical information recording medium in the radial direction on the second optical information recording medium. A three-spot diffraction grating having approximately one-half of the pitch, and the three-spot diffraction grating converts the first light beam emitted from the first semiconductor laser light source into at least three light beams. And the spot interval of the three light beams is set to a predetermined write-once type or written in the radial direction on the first optical information recording medium. Repositionable optical information optical pickup device, characterized in that to approximately one half of the pitch of the groove which is previously formed on the recording medium. 38. An optical information reproducing apparatus or an optical information recording apparatus equipped with the optical pickup device according to claim 26.

Images