JP2008077744A - Optical pickup - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently use the laser beam radiated to a front monitor diode provided to control the output of a laser diode. <P>SOLUTION: The optical pickup which has a polarizing beam splitter 33 having a reflector film 33a to receive the laser beam from the laser diode 11, transmits the laser beam toward the objective lens 88, and reflect a part of the laser beam as a monitor laser beam to a front monitor diode 44 provided to control the output of the laser beam. The central part of the reflector film 33a is used as a total transmissive film to transmit the incident laser beam as the laser beam to the objective lens 88, and its periphery is used as a total reflector to reflect the beam as the monitor laser beam. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical pickup apparatus that performs an operation of reading a signal recorded on an optical disc and an operation of recording a signal on the optical disc.

  2. Description of the Related Art Optical disk apparatuses that can perform signal reading operation and signal recording operation by irradiating a signal recording layer of an optical disk with laser light emitted from an optical pickup device have become widespread.

  FIG. 5 is a perspective view of a main part showing a general configuration of a conventional optical pickup device. In the figure, reference numeral 1 denotes a laser diode that emits an output laser beam L1 corresponding to a drive signal supplied from a laser drive circuit, and the laser beam L1 is a laser beam having an elliptical cross section.

  Reference numeral 2 denotes a diffraction grating on which the laser beam L1 radiated from the laser diode 1 is incident. The 0th-order light, the + 1st-order light, and the −1st-order light generated in this way cause the laser light to follow the signal reproduction operation, the focusing control operation for focusing the laser light on the signal recording layer of the optical disc, and the signal track. It is used for tracking control operation.

  Reference numeral 3 denotes a polarization beam splitter on which the laser beam L2 emitted from the diffraction grating 2 is incident. The polarization beam splitter 3 is provided to transmit the laser beam L3 irradiated to the optical disc (not shown) and to control the output of the laser beam. A reflective film 3a for reflecting the monitor laser light L4 irradiated to the front monitor diode 4 is provided. The reflection film 3a is also configured to reflect the return light reflected from the optical disk, as will be described later.

  Reference numeral 5 denotes a collimator lens to which the laser beam L3 transmitted through the polarization beam splitter 3 is incident, and has an action of changing the incident laser beam L3 to a laser beam L5 which is a parallel beam. Reference numeral 6 denotes a reflection mirror on which the laser beam L5 is incident, and serves to reflect all of the laser beam L5 in the direction of the optical disc as the laser beam L6. Such a reflection mirror 6 is generally called a raising mirror.

  Reference numeral 7 denotes a quarter-wave plate on which the laser beam L6 reflected from the reflection mirror 6 is incident, and functions to shift the phase of the laser beam L6 by a quarter wavelength. Reference numeral 8 denotes an objective lens to which the laser beam L7 transmitted through the quarter-wave plate 7 is incident, and has an effect of focusing as a laser beam L8 focused on a signal recording layer provided on the optical disc.

  Laser light L8 irradiated to the signal recording layer of the optical disc by the objective lens 8 is incident on the objective lens 8 as return light reflected from the signal recording layer. Return light incident on the objective lens 8 is incident on the polarization beam splitter 3 through the quarter-wave plate 7, the reflection mirror 6, and the collimator lens 5.

  In this way, the phase of the return light incident on the polarizing beam splitter 3 is reciprocated through the quarter-wave plate 7 and thus shifted by a half wavelength. When return light whose phase is shifted in this way is incident on the polarizing beam splitter 3, it is reflected as control laser light L9 by the reflecting film 3a formed on the polarizing beam splitter 3.

  Reference numeral 9 denotes a sensor lens to which the control laser light L9 reflected by the reflective film 3a of the polarizing beam splitter 3 is incident, and the control laser light is provided in a light receiving portion provided in a photodetector 10 called a PDIC. L9 is guided as convergent light and irradiated.

  In the optical pickup device shown in FIG. 5, the laser light L 1 emitted from the laser diode 1 passes through the diffraction grating 2, the polarization beam splitter 3, the collimator lens 5, the reflection mirror 6 and the quarter wavelength plate 7 to the objective lens 8. Incident light is applied to the signal recording layer of the optical disc by the focusing operation of the objective lens 8.

  The laser light L8 applied to the signal recording layer is reflected from the signal recording layer and is incident on the objective lens 8 as return light. The return light incident on the objective lens 8 is incident on the polarization beam splitter 3 via the quarter-wave plate 7, the reflection mirror 6 and the collimator lens 5.

  The return light incident on the polarization beam splitter 3 is out of phase with respect to the laser light L 2 incident from the laser diode 1 side by a half wavelength, and is reflected by the polarization beam splitter 3. Reflected by the film 3a as control laser light L9. The control laser light L9 obtained in this way is incident on the sensor lens 9 and is irradiated on the light receiving portion provided in the photodetector 10.

  As the light receiving unit provided in the photodetector 10, a well-known four-divided sensor or the like is provided as not shown, but a reproduction signal that is a data signal recorded on the optical disk, a focusing control operation A focusing control signal for performing tracking and a tracking control signal for performing tracking control operation are generated.

  The laser beam L1 emitted from the laser diode 1 is incident on the polarization beam splitter 3 as the laser beam L2 diffracted by the diffraction grating 2, and a part of the laser beam L1 is reflected by the reflecting film 3a and is used for the monitoring laser. The light is emitted to the front monitor diode 4 as light L4.

  The monitoring laser light L4 irradiated to the front monitor diode 4 changes according to the output level of the laser light L1 emitted from the laser diode 1. Accordingly, the monitor signal generated by the front monitor diode 4 is fed back to a drive circuit provided to supply a drive signal to the laser diode 1, whereby the output of the laser light L1 emitted from the laser diode 1 is set to a predetermined value. Laser servo operation can be performed to control Such laser servo operation is well known and will not be described.

  The conventional optical pickup device shown in FIG. 5 is configured to use the laser light reflected from the reflective film 3a of the polarizing beam splitter 3 as the monitoring laser light L4. The optical pickup device shown in FIG.

  In FIG. 6, the same members as those shown in FIG. As can be seen from the figure, the monitor laser light L4 is configured to use the laser light transmitted through the reflection mirror 6. That is, in the optical pickup device having such a configuration, the laser light L5 incident on the reflection mirror 6 is not totally reflected by the reflection mirror 6, and a part of the laser light is transmitted as the monitor laser light L4. The reflection film provided on the reflection mirror 6 is configured.

  The optical pickup apparatus shown in FIG. 6 can also read out signals recorded on the optical disc by performing the same operation as that of the optical pickup apparatus shown in FIG.

  In the above-described conventional optical pickup device, a part of the laser light L1 emitted from the laser diode 1 is used as the monitoring laser light L4 for controlling the laser output. Is used, the amount of the laser beam L8 applied to the signal recording layer provided on the optical disk is reduced accordingly.

  On the other hand, in an optical disc apparatus, it is necessary to increase the amount of laser light L8 in order to perform a reproducing operation and a recording operation at a high speed. For this reason, a high output of the laser diode 1 is required. However, the increase in output of the laser diode 1 is not only limited, but heat generation associated with an increase in drive current is a serious problem.

As a method for solving such a problem, a method of efficiently using a laser beam used as a monitor laser beam has been developed. (See Patent Document 1 and Patent Document 2.)
JP-A-11-86313 JP 2003-208729 A

  The prior art disclosed in Patent Document 1 or 2 described above uses laser light that is not used for signal reading operation of the optical pickup device, so-called unnecessary light. Since the amount of light used is likely to change due to process variations, there is a problem that a stable laser output control operation cannot be performed.

  The present invention is intended to provide an optical pickup device that can solve such a problem.

  The present invention relates to a laser diode that emits laser light, a diffraction grating on which laser light emitted from the laser diode is incident, laser light that has passed through the diffraction grating, and laser light toward the objective lens Pickup comprising a polarizing beam splitter on which a reflection film for reflecting a part of the laser beam as a monitor laser beam is formed on a front monitor diode provided to transmit the laser beam and to control the output of the laser beam In the apparatus, the laser beam incident on the central portion of the reflective film is made to be a total transmission film that transmits the laser light in the direction of the objective lens, and the peripheral portion is made to be a total reflection film that reflects the laser light for monitoring. is there.

  Further, the present invention is configured to effectively use laser light by making the shape of the total transmission film circular.

  In the present invention, a condensing lens for condensing the ring-shaped monitoring laser light on the light receiving portion of the front monitor diode is provided between the polarizing beam splitter and the front monitor diode so that the light receiving operation can be performed without any problem. It is configured.

Further, the present invention provides a laser diode that emits laser light, a diffraction grating on which laser light emitted from the laser diode is incident, laser light that has passed through the diffraction grating is incident, and is directed toward the objective lens. A light having a reflection mirror formed with a reflection film that reflects a part of the laser light as a monitor laser light to a front monitor diode provided to reflect the laser light and control the output of the laser light In the pickup device, a total reflection film that reflects the laser beam incident on the central portion of the reflection film as a laser beam in the direction of the objective lens and a total transmission film that transmits the peripheral portion as a laser beam for monitoring. It is.

  The optical pickup device of the present invention is a total transmission film that transmits laser light incident on the central part of the reflection film provided in the polarization beam splitter as laser light in the direction of the objective lens, and its peripheral part is used for monitoring. Since the total reflection film is reflected as the laser beam, a sufficient amount of light can be efficiently obtained as the laser beam used for reading the signal recorded on the optical disk.

  In addition, the pickup device of the present invention uses a total reflection film that reflects laser light incident on the central portion of the reflection film provided on the reflection mirror as laser light toward the objective lens, and the periphery thereof is used for monitoring. Since the total transmission film is made to transmit as laser light, it is possible to efficiently obtain a sufficient amount of light as the amount of laser light used for performing the reading operation of the signal recorded on the optical disk.

  FIG. 1 is a perspective view of a main part showing an embodiment of the optical pickup device of the present invention, and FIG. 2 is a perspective view of the main part.

  In FIG. 1, 11 is a laser diode that emits laser light L11 having an output corresponding to a drive signal supplied from a laser drive circuit, and the laser light L11 is a laser light having an elliptical cross section.

  Reference numeral 22 denotes a diffraction grating on which the laser beam L11 emitted from the laser diode 11 is incident, and has a function of generating and emitting a laser beam L22 composed of 0th-order light, + 1st-order light, and −1st-order light. The 0th-order light, the + 1st-order light, and the −1st-order light generated in this way cause the laser light to follow the signal reproduction operation, the focusing control operation for focusing the laser light on the signal recording layer of the optical disc, and the signal track. Since it is used for the tracking control operation and can be performed by a known technique, the description thereof is omitted.

  Reference numeral 33 denotes a polarization beam splitter on which the laser beam L22 emitted from the diffraction grating 22 is incident, and is provided to transmit the laser beam L33 incident on an objective lens described later and to control the output of the laser beam. A reflective film 33a for reflecting the monitor laser light L44 irradiated to the front monitor diode 44 is provided. The reflection film 33a is also configured to reflect the return light reflected from the optical disk, as will be described later.

  Reference numeral 444 denotes a condensing lens to which the monitoring laser light L44 reflected by the reflecting film 33a of the polarizing beam splitter 33 is incident. The incident monitoring laser light L44 is condensed and received by the front monitor diode 44. The part is irradiated.

Reference numeral 55 denotes a collimator lens to which the laser beam L33 transmitted through the reflection film 33a of the polarizing beam splitter 33 is incident, and has an action of changing the incident laser beam L33 to a laser beam L55 which is a parallel beam. Reference numeral 66 denotes a reflection mirror on which the laser beam L55 is incident, and has a function of reflecting all the laser beam L55 as laser beam L66 in the direction of the objective lens. Such a reflection mirror 66 is generally called a raising mirror.

  Reference numeral 77 denotes a quarter wavelength plate on which the laser beam L66 reflected from the reflection mirror 66 is incident, and has an action of shifting the phase of the laser beam L66 by a quarter wavelength. Reference numeral 88 denotes an objective lens to which the laser beam L77 transmitted through the quarter wavelength plate 77 is incident, and has an effect of focusing as a laser beam L88 focused on a signal recording layer provided on the optical disc. The objective lens 88 is configured to perform a focusing control operation by a displacement operation in a direction perpendicular to the signal surface of the optical disc and to perform a tracking control operation by a displacement operation in the radial direction of the optical disc. The objective lens that performs such an operation is provided to be displaceable by, for example, four support wires. However, since such a configuration is well known, the description thereof is omitted.

  The laser beam L88 applied to the signal recording layer of the optical disc by the objective lens 88 is incident on the objective lens 88 as return light reflected from the signal recording layer. The return light incident on the objective lens 88 is incident on the polarization beam splitter 33 through the quarter-wave plate 77, the reflection mirror 66 and the collimator lens 55.

  In this way, the phase of the return light incident on the polarization beam splitter 33 is reciprocated through the quarter-wave plate 77 and thus shifted by a half wavelength. When the return light whose phase is shifted in this way is incident on the polarization beam splitter 33, it is reflected as the control laser light L99 by the reflection film 33a formed on the polarization beam splitter 33.

  Reference numeral 99 denotes a sensor lens to which the control laser light L99 reflected by the reflective film 33a of the polarization beam splitter 33 is incident, and the control laser light is provided in a light receiving portion provided in the photodetector 101 called PDIC. L99 is guided as convergent light and irradiated.

  In the optical pickup device shown in FIG. 1, the laser light L 11 emitted from the laser diode 11 passes through the diffraction grating 22, the polarization beam splitter 33, the collimator lens 55, the reflection mirror 66, and the quarter wavelength plate 77 to the objective lens 88. Incident light is applied to the signal recording layer of the optical disc by the focusing operation of the objective lens 88.

  The laser beam L88 applied to the signal recording layer is reflected from the signal recording layer and enters the objective lens 88 as return light. The return light incident on the objective lens 88 is incident on the polarization beam splitter 33 via the quarter-wave plate 77, the reflection mirror 66, and the collimator lens 55.

  The return light incident on the polarization beam splitter 33 is reflected as control laser light L99 by the reflection film 33a provided on the polarization beam splitter 33. The control laser beam L99 obtained in this way is incident on the sensor lens 99 and is irradiated to the light receiving unit provided in the photodetector 101 as the laser beam L101 converged by the sensor lens 99.

  As the light receiving section provided in the photodetector 101, a known quadrant sensor or the like is provided, and a reproduction signal that is a data signal recorded on the optical disc, a focusing for performing a focusing control operation. The control signal and the tracking control signal for performing the tracking control operation are generated. A focusing control operation, a tracking control operation, a signal reproduction operation, and the like based on signals obtained from various sensor units provided in the photodetector 101 are well-known, and a description thereof will be omitted.

  The laser beam L11 emitted from the laser diode 11 is incident on the polarization beam splitter 33 as the laser beam L22 diffracted by the diffraction grating 22, and a part of the laser beam L11 is reflected by the reflection film 33a and is used for the monitoring laser. The light is emitted to the front monitor diode 44 as light L44.

  The monitoring laser light L44 applied to the front monitor diode 44 changes according to the output level of the laser light L11 emitted from the laser diode 11. Therefore, the monitor signal generated by the front monitor diode 44 is fed back to a drive circuit that supplies a drive signal to the laser diode 11, thereby controlling the output of the laser light L11 emitted from the laser diode 11 to a predetermined value. Laser servo operation can be performed. Such a laser servo operation can be configured by a known circuit, and the description thereof is omitted.

  Here, the gist of the present invention will be described with reference to the perspective views shown in FIGS. FIG. 1B is a diagram for explaining a portion of the polarizing beam splitter 33. In FIG. 1, a circular portion A indicated by oblique lines in the reflective film 33a provided on the polarizing beam splitter 33 is incident. And a laser beam reflecting portion for monitoring that totally reflects as a monitoring laser beam L44 in its peripheral portion (between the circle indicated by a broken line and the portion A) in the figure. Has been.

  As a result of the configuration of the reflection film 33a of the polarization beam splitter 33 as described above, the monitoring laser light L44 obtained by reflection by the reflection film 33a is a laser light having a ring-shaped cross section as shown in FIG. Since the ring-shaped monitoring laser beam L44 is incident on the condensing lens 444, the front monitor diode 44 is irradiated as a single laser beam by the condensing action of the condensing lens 444. .

  Therefore, even if the monitoring laser light L44 reflected by the reflective film 33a of the polarizing beam splitter 33 is a ring-shaped laser light, the laser light applied to the front monitor diode 44 is collected by the condenser lens 444. Since the laser light is used, the laser light for performing the light quantity monitoring operation by the front monitor diode 44 can be obtained without any trouble.

  The circular total transmission film portion A provided on the reflection film 33a provided on the polarization beam splitter 33 is provided to transmit the laser light L33 guided to the objective lens 88. The diameter of the transmissive membrane portion A is set to the effective diameter of the objective lens 88 in consideration of the shift amount of the objective lens 88, component errors, and assembly errors. Thus, by setting the diameter of the total transmission film portion A, the operation as the optical pickup device can be performed without any trouble.

  FIG. 3 is a perspective view of a main part showing another embodiment of the optical pickup device of the present invention, and FIG. 4 is a perspective view of the main part.

  In FIG. 3, the same members as those shown in FIG. As can be seen from the figure, the monitor laser light L44 is configured to use the laser light transmitted through the reflection mirror 66. That is, in the optical pickup device having such a configuration, the laser light L55 incident on the reflection mirror 66 is not totally reflected by the reflection mirror 66, and a part of the laser light is transmitted as the monitor laser light L44. The reflection film provided on the reflection mirror 66 is configured.

  Here, the gist of the present invention will be described with reference to FIGS. In FIG. 3B, a circular portion B indicated by oblique lines on the reflection film 66a provided on the reflection mirror 66 is a total reflection film portion that reflects all incident laser light and its periphery. The portion (between the circle indicated by a broken line and the portion B in the figure) is a monitor laser beam transmitting portion that transmits the entire amount as the monitor laser beam L44.

  As a result of the configuration of the reflection film 66a of the reflection mirror 66 as described above, the monitor laser light L44 obtained through the reflection film 66a is a laser beam having a ring-shaped cross section as shown in FIG. Since such a ring-shaped monitoring laser beam L44 is incident on the condensing lens 444, the condensing action of the condensing lens 444 irradiates the front monitor diode 44 as a single laser beam.

  Therefore, even if the monitoring laser light L44 transmitted through the reflective film 66a of the reflecting mirror is a ring-shaped laser light, the laser light applied to the front monitor diode 44 becomes the laser light condensed by the condenser lens 444. Therefore, it is possible to obtain a laser beam for performing the light amount monitoring operation by the front monitor diode 44 without any trouble.

  The circular total reflection film portion B provided on the reflection film 66a provided on the reflection mirror 66 is provided to reflect the laser beam L66 guided to the objective lens 88. This total reflection is performed. The diameter of the film part B is set to the effective diameter of the objective lens 88 in consideration of the shift amount of the objective lens 88, component errors, and assembly errors. Thus, by setting the diameter of the total reflection film portion B, the operation as the optical pickup device can be performed without any trouble.

  In the first embodiment, the laser beam L33 transmitted through the reflecting film 33a provided in the polarizing beam splitter 33 is guided to the objective lens 88, and the laser beam reflected by the reflecting film 33a is used as the monitoring laser beam L44. Although the optical pickup device to be used has been described, the laser light reflected by the reflective film 33a provided in the polarization beam splitter 33 is guided to the objective lens 88, and the laser light transmitted through the reflective film 33a is used as the monitor laser light. It can also be implemented in an optical pickup device used as the above.

  That is, in the optical pickup device that uses the laser light transmitted through the reflective film 33a as the monitor laser light, the portion of the reflective film 33a provided in the polarizing beam splitter 33 that reflects the laser light toward the objective lens is provided. The monitor laser beam is set to be transmitted through the total reflection portion and the peripheral portion as the total transmission portion.

It is a perspective view of the principal part which shows one Example of the optical pick-up apparatus of this invention. It is a perspective view of the principal part of the optical pick-up apparatus shown in FIG. It is a perspective view of the principal part which shows one Example of the optical pick-up apparatus of this invention. It is a perspective view of the principal part of the optical pick-up apparatus shown in FIG. It is a perspective view of the principal part which shows one Example of the conventional optical pick-up apparatus. It is a perspective view of the principal part which shows one Example of the conventional optical pick-up apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Laser diode 22 Diffraction grating 33 Polarization beam splitter 44 Front monitor diode 55 Collimator lens 66 Reflection mirror 77 1/4 wavelength plate 88 Objective lens A Total transmission film part B Total reflection film part

Claims (11)

A laser diode that emits laser light, a diffraction grating on which the laser light emitted from the laser diode is incident, and a laser beam that has passed through the diffraction grating is incident and transmits the laser light toward the objective lens; And an optical pickup device comprising a polarization beam splitter on which a reflection film for reflecting a part of the laser beam as a laser beam for monitoring is formed on a front monitor diode provided to control the output of the laser beam, The laser light incident on the central portion of the reflective film is a total transmission film that transmits the laser light in the direction of the objective lens, and the total reflection film that reflects the peripheral portion as laser light for monitoring is used. Optical pickup device. 2. The optical pickup device according to claim 1, wherein the shape of the total transmission film is circular. 3. The optical pickup device according to claim 2, wherein the cross-sectional shape of the monitoring laser beam reflected by the total reflection film is a ring shape. 4. The optical pickup device according to claim 3, wherein a condensing lens for condensing the ring-shaped monitoring laser light on the light receiving portion of the front monitor diode is provided between the polarizing beam splitter and the front monitor diode. 3. The optical pickup device according to claim 2, wherein the diameter of the total transmission film is set to the effective diameter of the objective lens in consideration of a shift amount of the objective lens, component errors, and assembly errors. The return light reflected from the signal recording layer of the optical disc by the reflective film provided in the polarization beam splitter is guided to a photodetector provided to obtain a signal used for tracking control operation of the optical pickup device. The optical pickup device according to claim 1, which is configured as described above. A laser diode that emits laser light, a diffraction grating on which the laser light emitted from the laser diode is incident, and laser light that has passed through the diffraction grating is incident and reflects the laser light toward the objective lens; And a reflection mirror formed with a reflection film for transmitting a part of the laser beam as a laser beam for monitoring to a front monitor diode provided to control the output of the laser beam, Light characterized by a total reflection film that reflects the laser light incident on the center of the reflection film as laser light toward the objective lens and a total transmission film that transmits the periphery as laser light for monitoring Pickup device. 8. The optical pickup device according to claim 7, wherein the shape of the total reflection film is circular. 9. The optical pickup device according to claim 8, wherein the cross-sectional shape of the monitoring laser beam that passes through the total transmission film is formed in a ring shape. 10. The optical pickup device according to claim 9, wherein a condensing lens for condensing the ring-shaped monitoring laser light on the light receiving portion of the front monitor diode is provided between the reflection mirror and the front monitor diode. 9. The optical pickup device according to claim 8, wherein the diameter of the total reflection film is set to the effective diameter of the objective lens in consideration of the shift amount of the objective lens, component errors, and assembly errors.

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