JP2010182381A - Optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably monitor light quantities of first and second laser beams emitted from first and second laser light sources. <P>SOLUTION: An optical pickup device PU1 includes: the first laser light source 11 selectively emitting the first laser beam L1; the second laser light source 21 selectively emitting the second laser beam L2 having emission power higher than that of the first laser beam L1 and a wavelength longer than that of the first laser beam L1; an optical detector 31 for a front monitor monitoring each of the light quantities of the first and second laser beams L1 and L2; and a laser beam light quantity adjusting means 40A provided on the laser beam incident side of the optical detector 31 for the front monitor using a plurality of optical members 31a, and 41 to 43 and optically adjusting a difference in light quantities between the first and second laser beams L1 and L2 made incident in the optical detector 31 for the front monitor using the optical members 31a, and 41 to43. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical pickup device that enables recording and reproduction of information signals on a plurality of optical recording media having different standards.

  In general, as an optical recording medium (optical disc) capable of recording or reproducing various information signals such as audio signals, video signals, and data signals with high density, a well-known CD (Compact Disc), DVD (Digital Versatile Disc), etc. In addition, recently, a high-density optical recording medium called a BD (Blu-ray Disc) with higher density has been put on the market.

  The above-mentioned CD has a substrate thickness from the laser beam incident surface to the information recording surface of about 1.2 mm, and a laser beam having a wavelength of about 780 nm is an objective having a numerical aperture (NA) of about 0.45 to 0.5. The information signal can be recorded or reproduced by irradiating the information recording surface in a spot shape with a lens.

  Further, the DVD described above has a substrate thickness from the laser beam incident surface to the information recording surface of about 0.6 mm, and a laser beam having a wavelength of about 650 nm has a numerical aperture (NA) of about 0.6 to 0.65. The information signal can be recorded or reproduced by irradiating the information recording surface in a spot shape with the objective lens. At this time, the recording capacity of the DVD is about 6 to 8 times higher than that of the CD, and is about 4.7 GB (gigabyte) on one side when the diameter of the disk substrate is 12 cm.

  The above-mentioned BD has a substrate thickness from the laser beam incident surface to the information recording surface of about 0.1 mm, and a laser beam having a wavelength of about 405 nm is obtained by an objective lens having a numerical aperture (NA) of about 0.85. The information signal can be recorded or reproduced by irradiating the information recording surface in a spot shape. At this time, the recording capacity of the BD is about 5 times higher than that of the DVD, and is about 25 GB (gigabyte) on one side when the diameter of the disk substrate is 12 cm.

  An optical disc apparatus for recording or reproducing a CD, DVD, or BD is provided with a drive mechanism that holds and rotates and drives the optical disc, and is movable in the radial direction of the optical disc so that a laser beam can be recorded on the optical disc. An optical pickup device that irradiates the surface in a spot shape, and a signal processing means for recording data by the optical pickup device or reproducing recorded data are provided inside.

  By the way, there is an optical pickup device provided with two systems of optical blocks including a BD optical block for recording or reproducing BD and a DVD / CD optical block for recording or reproducing DVD / CD (for example, see Patent Document 1). ).

  In the optical pickup device disclosed in Patent Document 1 described above, although not shown here, the BD optical block includes a BD laser diode, a collimator lens, a beam shaping prism / PBS, and a BD front monitor. Consists of a photodetector, spherical aberration correction element, BD rising mirror, polarization hologram composite element, BD high NA objective lens, focusing lens, concave lens, hologram element, and BD photodetector Has been.

  On the other hand, the DVD / CD optical block includes a DVD laser diode, a diffraction grating, a CD laser diode, a coupling lens, a diffraction grating, a dichroic prism, a DVD / CD polarization beam splitter, and a collimator lens. DVD / CD front photo detector, DVD / CD rising mirror, 1/4 wavelength plate, wavelength selective aperture filter, DVD / CD objective lens, anamorphic lens, DVD / CD It consists of a photodetector.

  In Patent Document 1, the output of a blue laser beam with a wavelength of 405 nm output from a BD laser diode is the wavelength output from a red laser beam with a wavelength of 650 nm output from a DVD laser diode or a CD laser diode. Is weaker than the output of the infrared laser beam of 780 nm, but the front monitor / photo detector for BD for controlling the output of the laser diode for BD by monitoring the light quantity of the blue laser beam, and the red laser beam or infrared laser Two front monitors / photodetectors, a DVD / CD front monitor / photodetector, for controlling the output of the DVD laser diode or CD laser diode by monitoring the light quantity of the beam are provided.

  On the other hand, when recording or reproducing a DVD and a CD, one front monitor is provided for the red laser beam emitted from the DVD laser light source and the infrared laser beam emitted from the CD laser light source. There is an optical pickup that monitors each light quantity using a common photodetector (see, for example, Patent Document 2).

  In the embodiment of the optical pickup disclosed in Patent Document 2 described above, the front monitor sensitivity of the front monitor photodetector is adjusted with respect to the DVD laser light source serving as the first light source, although illustration is omitted here. On the other hand, the setting of the front monitor sensitivity of the CD laser light source as the second light source is performed by selecting the gain of the amplifier, and the light shielding that can move on the optical path between the CD laser light source and the front monitor photodetector. A plate is arranged, and the light shielding plate is moved on the optical path to attenuate the amount of light from the CD light source.

  Further, in another embodiment of the optical pickup disclosed in Patent Document 2, the DVD laser light source and the CD laser light source are omitted in order to omit a variable resistor for adjusting the amplifier gain, although illustration is omitted here. The front monitor sensitivity setting is adjusted by individually adjusting the amount of light to the front monitor photodetector for each laser beam emitted from the light by a light-shielding plate that can move in the direction crossing each optical path. Is doing.

JP 2004-295983 A JP 2003-217160 A

  By the way, in the optical pickup device disclosed in Patent Document 1, by providing a BD optical block and a DVD / CD optical block, it is possible to cope with BD as well as DVD and / or CD. To monitor the DVD laser diode / CD laser diode, two BD front photo detectors and two DVD / CD front photo detectors are required, which increases the cost. When the technical idea is applied as it is and one front monitor photodetector is shared, a new problem occurs as described below.

  That is, when the embodiment of the optical pickup disclosed in Patent Document 2 is applied, the amplifier gain must be selected when adjusting the front monitor sensitivity for the DVD laser light source as the first light source. For this reason, adjustment man-hours are required. On the other hand, when adjusting the front monitor sensitivity with respect to the CD laser light source as the second light source, the light shielding plate must be moved on the optical path. As a result, the structure of the optical pickup becomes complicated.

  In addition, when another embodiment of the optical pickup disclosed in Patent Document 2 is applied, there is no need to select an amplifier gain for front monitor sensitivity adjustment of the DVD laser light source. When setting the front monitor sensitivity for the laser light source, it is adjusted individually by each light shielding plate that can move in the direction crossing each optical path, so each light shielding plate moving mechanism is required, and the structure of the optical pickup is further complicated Problem arises.

  Therefore, a first laser light source that emits the first laser beam and a second laser light source that emits a second laser beam having a longer wavelength than the first laser beam and a larger emission power than the first laser beam are used. Light detection for front monitor for monitoring the light amounts of the first and second laser beams emitted from the first and second laser light sources when recording and reproducing optical information on a plurality of optical recording media having different standards When the detector is shared, the amplifier gain adjustment circuit can be simplified with respect to the output of the front monitor photodetector, and the first and second laser light sources emitted from the first and second laser light sources can be simplified. To provide an optical pickup device that can stably monitor the light amounts of two laser beams and can reliably adjust the light amount difference between the first and second laser beams incident on the front monitor photodetector. For the purpose.

The present invention has been made in view of the above problems, and the first invention includes a first laser light source that emits a first laser beam corresponding to the first optical recording medium,
Corresponding to the second optical recording medium having a substrate thickness larger than that of the first optical recording medium, a second laser beam having a larger emission power than the first laser beam and having a longer wavelength than the first laser beam is emitted. A second laser light source,
A front monitor photodetector that receives the first and second laser beams selectively emitted from the first and second laser light sources and monitors the respective light amounts of the first and second laser beams;
A light amount difference between the first and second laser beams that are installed on the laser beam incident side of the front monitor photodetector using a plurality of optical members and are incident on the front monitor photodetector by the plurality of optical members. A laser beam light amount adjusting means for optically adjusting
An optical pickup device comprising:

The second invention is the optical pickup device of the first invention described above,
An amplifier is connected to the output side of the front monitor photodetector, and the light quantity difference between the first and second laser beams is changed by the plurality of optical members in the laser beam light quantity adjusting means. The optical pickup device is optically adjusted so as to have a substantially gain difference of the amplifier with respect to a beam.

The third invention is the optical pickup device of the first or second invention described above,
Of the plurality of optical members used in the laser beam light amount adjusting means, the incident angle of the first laser beam with respect to at least one optical member installed on the laser beam incident side of the front monitor photodetector is a first incident. The optical pickup device is characterized in that when the incident angle of the second laser beam is the second incident angle, the second incident angle is made larger than the first incident angle.

Moreover, 4th invention is an optical pick-up apparatus of 3rd invention mentioned above,
In the optical pickup device, at least one of the plurality of optical members used for the laser beam light amount adjusting means is in close contact with the laser beam incident side of the front monitor photodetector. .

The fifth invention is the optical pickup device of the third or fourth invention described above,
The first laser beam is incident on the front monitor photodetector with P-polarized light, while the second laser beam is incident on the front monitor photodetector with S-polarized light. It is a pickup device.

According to a sixth aspect of the present invention, in the optical pickup device of the first or second aspect or the fourth aspect,
Comprising at least one objective lens for condensing the first laser beam and the second laser beam;
The plurality of optical members used for the laser beam light amount adjusting means are:
A sealing transparent optical member attached in close contact with the laser beam incident side of the front monitor photodetector;
A first semi-transmissive / reflective mirror that reflects a part of the first laser beam emitted from the first laser light source to the objective lens side and transmits a remaining part of the first laser beam;
Total reflection that partially reflects the part of the first laser beam that has passed through the first semi-transmissive / reflecting mirror and enters the sealing transparent optical member of the front monitor photodetector at the first incident angle. Mirror,
A part of the second laser beam emitted from the second laser light source is reflected toward the objective lens, and the remaining part of the second laser beam is transmitted to transmit the part of the front monitor photodetector. A second semi-transmissive / reflective mirror that is incident on the transparent optical member for sealing at the second incident angle larger than the first incident angle;
It is an optical pick-up apparatus characterized by including.

Furthermore, a seventh invention is the optical pickup device of the first or second invention described above,
Comprising at least one objective lens for condensing the first laser beam and the second laser beam;
The plurality of optical members used for the laser beam light amount adjusting means are:
A first semi-transmissive / reflective mirror that reflects a part of the first laser beam emitted from the first laser light source to the objective lens side and transmits a remaining part of the first laser beam;
A total reflection mirror that totally reflects a part of the first laser beam transmitted through the first semi-transmissive / reflective mirror;
A second semi-transmissive / reflective mirror that reflects a part of the second laser beam emitted from the second laser light source toward the objective lens and transmits the remaining part of the second laser beam;
A part of the first laser beam totally reflected by the total reflection mirror is incident at a first incident angle and then emitted and incident on the front monitor photodetector and transmitted through the second semi-transmissive / reflective mirror. A glass plate that exits after a part of the second laser beam is incident at a second incident angle larger than the first incident angle and is incident on the front monitor photodetector;
It is an optical pick-up apparatus characterized by including.

  According to the optical pickup device of the present invention, the first laser light source that emits the first laser beam and the second laser beam that has a longer wavelength than the first laser beam and a larger emission power than the first laser beam are emitted. When recording and reproducing optical information on a plurality of optical recording media with different standards using the second laser light source, the respective light amounts of the first and second laser beams emitted from the first and second laser light sources are monitored. When using a common front monitor photodetector for installation, a plurality of optical members are installed on the laser beam incident side of the front monitor photodetector. Since there is a laser beam light amount adjusting means for optically adjusting the light amount difference between the first and second laser beams incident on the photodetector, the light beams are emitted from the first and second laser light sources. In addition to being able to stably monitor the light amounts of the first and second laser beams with the front monitor photodetector, it is possible to reliably adjust the light amount difference between the first and second laser beams incident on the front monitor photodetector, Furthermore, since control for switching between the first laser light source and the second laser light source is not necessary, the number of control terminals of the optical pickup device can be reduced.

  Further, a plurality of optical members in the laser beam light amount adjusting means are provided by installing laser beam light amount adjusting means on the incident side of the front monitor light detector and connecting an amplifier to the output side of the front monitor light detector. Thus, the optical adjustment is performed so that the difference between the light amounts of the first and second laser beams becomes approximately the gain difference of the amplifier with respect to the first and second laser beams. Since a fixed resistor can be used as the feedback resistor, the gain adjustment circuit can be simplified and the amplifier can be operated stably.

  Further, among the plurality of optical members used for the laser beam light amount adjusting means, the incident angle of the first laser beam with respect to at least one optical member installed on the laser beam incident side of the front monitor photodetector is a first incident angle, When the incident angle of the second laser beam is the second incident angle, the light amounts of the first and second laser beams incident on the front monitor photodetector are set by making the second incident angle larger than the first incident angle. The difference can be adjusted reliably.

BRIEF DESCRIPTION OF THE DRAWINGS It is the figure which showed typically the whole structure of the optical pick-up apparatus of Example 1 which concerns on this invention, (a) is a left view, (b) is a top view, (c) is an optical system for BD. Front view, (d) is a front view of an optical system for DVD. It is the figure which expanded and showed the laser beam light quantity adjustment means with respect to the photodetector for front monitors shown in FIG. In the optical pick-up apparatus of Example 1 which concerns on this invention, it is the figure which showed the relationship between the incident angle and light transmittance of the blue laser beam and red laser beam which inject into the transparent optical member for sealing of the photodetector for front monitors. is there. FIG. 3 is a diagram schematically illustrating the overall configuration of an optical pickup device according to a second embodiment of the present invention, where (a) is a left side view, (b) is a plan view, and (c) is an optical system for a BD. Front view, (d) is a front view of an optical system for DVD. FIG. 5 is an enlarged view showing a laser beam light amount adjusting means for the front monitor photodetector shown in FIG. 4. In the optical pick-up apparatus of Example 2 which concerns on this invention, it is the figure which showed the relationship between the incident angle and light transmittance of the blue laser beam and red laser beam which inject into a glass plate.

  Hereinafter, an embodiment of an optical pickup device according to the present invention will be described in detail in the order of Embodiment 1 and Embodiment 2 with reference to FIGS.

  FIG. 1 is a diagram schematically showing the overall configuration of an optical pickup device according to a first embodiment of the present invention, where (a) is a left side view, (b) is a plan view, and (c) is for BD. FIG. 2D is a front view of the optical system, and FIG. FIG. 2 is an enlarged view of the laser beam light amount adjusting means for the front monitor photodetector shown in FIG. Further, FIG. 3 shows the relationship between the incident angle of the blue laser beam and the red laser beam incident on the transparent optical member for sealing of the front monitor photodetector and the light transmittance in the optical pickup device according to the first embodiment of the present invention. FIG.

  As shown in FIGS. 1A to 1D, the optical pickup apparatus PU1 according to the first embodiment of the present invention selectively emits a first laser beam L1 having a short wavelength from the first laser light source 11, The first laser beam L1 is focused in a spot shape on the first optical recording medium 1 having a small substrate thickness by the first objective lens 16 having a high numerical aperture (NA). A second laser beam L2 having a wavelength longer than that of the first laser beam L1 and having a larger emission power than that of the first laser beam is selectively emitted, and the second laser beam L2 has a numerical aperture lower than that of the first objective lens 16. When the second objective lens 26 having (NA) is focused in a spot shape on the second optical recording medium 2 having a substrate thickness larger than that of the first optical recording medium 1, the first and second laser light sources 11 and 21 are used. And first The front monitor photodetector 31 for monitoring the light amounts of the first and second laser beams L1 and L2 between the two objective lenses 16 and 26 is shared by the first and second laser beams L1 and L2. When installed, the laser beam light amount adjusting means 40A for optically adjusting the light amount difference between the first and second laser beams L1 and L2 incident on the front monitor photodetector 31 is detected by the front monitor light detector. It is characterized in that it is installed on the laser beam incident side of the device 31 using a plurality of optical members 31a, 41 to 43 or a plurality of optical members 41 to 43.

  At this time, for example, a BD (Blu-ray Disc) having a substrate thickness of about 0.1 mm from the laser beam incident surface to the information recording surface is applied as the first optical recording medium (hereinafter referred to as BD) 1. In this case, a first laser light source (hereinafter referred to as a BD laser light source) 11 emits a first laser beam (hereinafter referred to as a blue laser beam) L1 having a short wavelength and a wavelength of about 405 nm, and BD. The laser light source 11 is attached in such a direction that the blue laser beam L1 emitted therefrom becomes P-polarized light, and the blue laser beam L1 is incident on the front monitor photodetector 31 as P-polarized light. ing.

  On the other hand, when a DVD (Digital Versatile Disc) in which the substrate thickness from the laser beam incident surface to the information recording surface is about 0.6 mm is applied as the second optical recording medium (hereinafter referred to as DVD) 2, for example. The second laser light source (hereinafter referred to as a DVD laser light source) 21 has a second laser beam (hereinafter referred to as red) having a larger emission power than the blue laser beam L1, a longer wavelength than the blue laser beam L1, and a wavelength of around 650 nm. L2 is emitted, and the DVD laser light source 21 is attached in such a direction that the red laser beam L2 emitted therefrom becomes S-polarized light, and is attached to the front monitor photodetector 31. The red laser beam L2 is incident as S-polarized light.

  The P-polarized light and S-polarized light described above are determined by the relative relationship between the plane of polarization of linearly polarized light and the incident surface 31a1 (shown only in FIG. 2) of the front monitor photodetector 31 on which it is incident. The polarization direction perpendicular to the incident surface 31a1 and the S-polarized light enter from the polarization direction horizontal to the incident surface 31a1.

  Here, the optical pickup device PU1 according to the first embodiment will be described more specifically.

  First, when recording or reproducing with respect to the BD 1, when the blue laser beam L 1 of P-polarized light is emitted from the BD laser light source 11, the blue laser beam L 1 in the forward path is converted into the polarization selectivity half of the first polarization beam splitter 12. The light passes through the transmissive / reflective dielectric multilayer film 12a and is incident on a first semi-transmissive / reflective mirror 41 constituting a part of a laser beam light amount adjusting means 40A described later. About 90% of the blue laser beam L1 is reflected by the objective lens 16 and then enters the first collimator lens 13, while the remaining part of the blue laser beam L1 of about 10% is the first semi-transmitted light. After passing through the reflection mirror 41, it is reflected by the total reflection mirror 42 and enters the front monitor photodetector 31 in the state of P-polarized light as will be described later.

  The forward blue laser beam L1 converted into substantially parallel light by the first collimator lens 13 is reflected by the rising mirror 14 by 90 °, bent upward along the optical path, and then incident on the quarter-wave plate 15. The quarter-wave plate 15 converts linearly polarized light into circularly polarized light.

  Thereafter, the blue laser beam L1 in the forward path that has passed through the quarter-wave plate 15 has a numerical aperture (NA) as high as about 0.85 and is applied to the information recording layer of the BD 1 by the high NA objective lens 16 that becomes the first objective lens. The light is collected in a spot shape.

  On the other hand, the returning blue laser beam L1 reflected by the information recording layer of the BD 1 after the beam condensing becomes circularly polarized light opposite to the outward path and re-enters the high NA objective lens 16, and this high NA objective lens 16 Thus, the light becomes substantially parallel light, passes through the quarter-wave plate 15 and becomes linearly polarized light whose polarization direction is orthogonal to the forward path.

  Thereafter, the blue laser beam L1 on the return path is turned 90 ° by the rising mirror 14, passes through the first collimator lens 13, is reflected by the first semi-transmissive / reflective mirror 41, and is reflected by the first polarizing beam splitter. The light is reflected by the 12 polarization-selective transflective / reflective dielectric multilayer film 12 a and received by the first photodetector 17. The tracking error signal, focus error signal, and main data signal are detected when the information recording layer of the BD 1 is reproduced by the first photodetector 17.

  Next, when recording or reproducing data on the DVD 2, when the red laser beam L 2 of S-polarized light is emitted from the DVD laser light source 21, the outward red laser beam L 2 is polarized by the second polarization beam splitter 22. After being reflected by the semi-transmissive / reflective dielectric multilayer film 22a, it is incident on the second collimator lens 23, where it is converted into substantially parallel light.

  Thereafter, the forward red laser beam L2 that has passed through the second collimator lens 23 is incident on a second semi-transmissive / reflective mirror 43 that constitutes a part of a laser beam light quantity adjusting means 40A described later, and this second semi-transmissive light beam is transmitted. / Most of about 90% of the forward red laser beam L2 is reflected on the objective lens 26 side by the reflecting mirror 43 and then enters the rising mirror 14, while the remaining part of about 10% of the red laser. After passing through the second semi-transmissive / reflective mirror 43, the beam L2 enters the front monitor photodetector 31 in the state of S-polarized light as will be described later.

  Then, the forward red laser beam L2 is reflected by the rising mirror 14 by 90 °, bent upward along the optical path, and then incident on the quarter-wave plate 25. To circularly polarized light.

  Thereafter, the outward red laser beam L2 that has passed through the quarter-wave plate 25 has a numerical aperture (NA) as low as about 0.65 and is applied to the information recording layer of the DVD 2 by the low NA objective lens 26 serving as the second objective lens. The light is collected in a spot shape.

  Then, the return red laser beam L2 reflected by the information recording layer of the DVD 2 after beam condensing becomes circularly polarized light opposite to the outward path and re-enters the low NA objective lens 26, and this low NA objective lens 26 Thus, the light becomes substantially parallel light and passes through the quarter-wave plate 25 and becomes linearly polarized light whose polarization direction is orthogonal to the forward path.

  Thereafter, the red laser beam L2 in the return path turns 90 ° light direction by the rising mirror 14, is reflected by the second semi-transmissive / reflective mirror 43, passes through the second collimator lens 23, and passes through the second polarizing beam splitter 22. Is transmitted through the polarization selective transflective / reflective dielectric multilayer film 22 a and received on the second photodetector 27. The tracking error signal, focus error signal, and main data signal are detected when the information recording layer of the DVD 2 is reproduced by the second photodetector 27.

  Further, in the first embodiment, as described above, the blue laser beam L1 and the red laser beam L2 are provided between the BD laser light source 11 and the DVD laser light source 21, and the high NA objective lens 16 and the low NA objective lens 26. A front monitor photodetector 31 for monitoring the respective light amounts of the laser beam L1 and L2 is installed in common, and the front monitor photodetector 31 is provided in an APC (Auto Power Control) means 30. A part of the laser beam light amount adjusting means 40A is provided on the laser beam incident side of the front monitor photodetector 31.

  The APC means 30 described above receives the laser beams L1 and L2 in order to monitor the respective light amounts of the blue laser beam L1 emitted from the BD laser light source 11 and the red laser beam L2 emitted from the DVD laser light source 21. A front monitor photodetector 31 having a sealing transparent optical member 31a attached in close contact therewith, an amplifier 32 electrically connected to the output side of the front monitor photodetector 31 via a wire, and a controller 33 and a laser drive circuit 34.

  In the APC means 30, the monitor output voltage obtained by photoelectrically converting the blue laser beam L1 or the red laser beam L2 selectively incident on the front monitor photodetector 31 according to BD1 or DVD2 is the minus (−) of the amplifier 32. ) Terminal and a preset reference voltage is input to the plus (+) terminal of the amplifier 32, and the controller 33 compares the monitor output voltage with the reference voltage, and based on the comparison result, the laser driving circuit. 34, the emission power of the BD laser light source 11 and the DVD laser light source 21 is controlled to be optimum.

  In the first embodiment, the front monitor photodetector 31 and the amplifier 32 to which the fixed resistor R is connected are provided separately. good.

  Further, the laser beam light amount adjusting means 40A described above constitutes a main part of the first embodiment, and as described above, the seal attached in close contact with the laser beam incident side of the front monitor photodetector 31. It consists of a transparent optical member 31a for stopping and a plurality of optical members 41 to 43 fixedly installed in front of the transparent optical member 31a for sealing the front monitor photodetector 31, and the laser beam of the front monitor photodetector 31 The light quantity difference between the blue laser beam L1 and the red laser beam L2 incident on the front monitor photodetector 31 is optically adjusted by a plurality of optical members 31a and 41 to 43 installed on the incident side.

  At this time, the plurality of optical members fixedly installed in front of the sealing transparent optical member 31a of the front monitor photodetector 31 are the first semi-transmissive / reflective mirror 41, the total reflective mirror 42, and the second semi-transmissive member. / Reflection mirror 43.

  As shown in an enlarged view in FIG. 2, in the laser beam light amount adjusting means 40 </ b> A, a part of the blue laser beam L <b> 1 of the P-polarized light emitted from the BD laser light source 11 is reflected by the first semi-transmissive / reflective mirror 41. When the blue laser beam L1 of P-polarized light totally reflected by the total reflection mirror 42 after being transmitted is incident on the sealing transparent optical member 31a of the front monitor photodetector 31, the sealing is performed. The total reflection mirror 42 is installed so that the first incident angle α of the blue laser beam L1 is incident at, for example, about 45 ° with respect to the normal line standing on the incident surface 31a1 of the stop transparent optical member 31a, and the DVD A transparent optical member 31 for sealing the front monitor photodetector 31 after a part of the red laser beam L2 of S-polarized light emitted from the laser light source 21 is transmitted through the second semi-transmissive / reflective mirror 43. The second half angle so that the second incident angle β of the red laser beam L2 is incident at, for example, approximately 70 ° with respect to the normal line standing on the incident surface 31a1 of the sealing transparent optical member 31a. A transmission / reflection mirror 43 is provided.

  In other words, when the first semi-transmissive / reflective mirror 41, the total reflective mirror 42, and the second semi-transmissive / reflective mirror 43 are arranged as shown in the drawing, The first incident angle α of the P-polarized blue laser beam L1 is approximately 45 ° and the second incident angle β of the S-polarized red laser beam L2 is approximately 70 with respect to the incident surface 31a1 of the sealing transparent optical member 31a. The mounting angle of the front monitor photodetector 31 is adjusted so as to be incident at an angle.

  In the first embodiment, the first incident angle α of the blue laser beam L1 is about 45 ° with respect to the incident surface 31a1 of the sealing transparent optical member 31a of the front monitor photodetector 31, and the red laser beam L2 The second incident angle β is set to approximately 70 °, but the present invention is not limited to this. The light amount difference between the blue laser beam L1 and the red laser beam L2 and the sensitivity difference depending on the wavelengths of the laser beams L1 and L2 are not limited thereto. The first and second incident angles α and β may be set according to the above.

  At this time, a blue laser beam L1 of P-polarized light and a red laser beam L2 of S-polarized light are applied to an optical material having a refractive index of about 1.5 used for the sealing transparent optical member 31a of the front monitor photodetector 31. The relationship between the incident angle of each of the laser beams L1 and L2 and the light transmittance is as shown in FIG.

  That is, as shown in FIG. 3, when the mark X is a characteristic with respect to the blue laser beam L1, and the mark ○ is a characteristic with respect to the red laser beam L2, S incident on the sealing transparent optical member 31a of the front monitor photodetector 31 is obtained. When the second incident angle β of the polarized red laser beam L2 is set to be larger than the first incident angle α of the blue laser beam L1 of P-polarized light, the blue laser beam L1 of P-polarized light is detected by the front monitor. When the light enters the transparent optical member 31a for sealing at approximately 45 °, the light transmittance is 99%, and therefore the blue laser beam L1 of the P-polarized light has a substantially unchanged light amount and is a front monitor photodetector. 31 is incident.

  On the other hand, when the red laser beam L2 of S-polarized light is incident on the sealing transparent optical member 31a of the front monitor photodetector 31 at approximately 70 °, the light transmittance is 70%. The light quantity of the red laser beam L2 is attenuated and incident on the front monitor photodetector 31.

  That is, by adjusting the mounting angle of the front monitor photodetector 31, the light transmittance of the P-polarized light blue laser beam L1 and the light transmittance of the S-polarized light red laser beam L2 can be freely changed to some extent. can do.

  In practice, the light path difference between the optical path of the blue laser beam L1 of P-polarized light and the optical path of the red laser beam L2 of S-polarized light is about the gain difference of the assumed front monitor sensitivity adjustment amplifier 32 (FIG. 1). When the optical pickup device PU1 is assembled, the mounting angle of the front monitor photodetector 31 is set to the blue laser beam L1 for P-polarized light and the red laser beam L2 for S-polarized light. The amplifier 32 (FIG. 1) is mounted so as to have a light amount difference that corresponds to a substantial gain difference.

  Accordingly, the blue laser beam L1 of the P-polarized light incident on the front monitor photodetector 31 and the S-polarized light by the plurality of optical members 31a, 41 to 43 in the laser beam light amount adjusting means 40A that can obtain the above characteristics. Since the optical adjustment is made so that the difference in the amount of light from the red laser beam L2 is substantially the gain difference of the amplifier 32 with respect to both the laser beams L1 and L2, the amplifier 32 (FIG. 1) for adjusting the front monitor sensitivity. Since the fixed resistor R can be used as a feedback resistor for gain adjustment, the gain adjustment circuit can be simplified and the amplifier 32 can be operated stably.

  Further, since the laser beam light amount adjusting means 40A is installed on the laser beam incident side of the front monitor photodetector 31 using a plurality of optical members 31a and 41 to 43, the blue laser beam L1 and the red laser beam L2 are controlled. In addition to being able to monitor each light quantity stably with the front monitor photodetector 31, the light quantity difference between the blue laser beam L1 and the red laser beam L2 incident on the front monitor photodetector 31 can be adjusted with certainty. Since control for switching between the laser light source 11 and the DVD laser light source 21 is not required, the number of control terminals of the optical pickup device PU1 (FIG. 1) of the first embodiment can be reduced.

  In the first embodiment, the blue laser beam L1 is P-polarized light and the red laser beam L2 is S-polarized light, so that the incident angles of the laser beams L1 and L2 incident on the front monitor photodetector 31 are as follows. However, the present invention is not limited to this, and the blue laser beam L1 can be S-polarized light and the red laser beam L2 can be P-polarized light. It is also possible to set the laser beams L1 and L2 to the same polarized light.

  At this time, when the blue laser beam L1 is S-polarized light and the red laser beam L2 is P-polarized light, a multilayer film is formed on the sealing transparent optical member 31a of the front monitor photodetector 31, The light transmittance (light quantity) of the red laser beam L2 of P-polarized light may be set lower than the light transmittance (light quantity) of the blue laser beam L1 of S-polarized light.

  In addition, when the blue laser beam L1 and the red laser beam L2 are the same polarized light (P-polarized light or S-polarized light), as is apparent from FIG. ) Appears, and this characteristic can be used.

  In the first embodiment, only the plurality of optical members 41 to 43 are provided without attaching the sealing transparent optical member 31 a having the characteristics shown in FIG. 3 to the laser beam incident side of the front monitor photodetector 31. Is used to make the second incident angle β of the red laser beam L2 incident on the front monitor photodetector 31 larger than the first incident angle α of the blue laser beam L1, so that the blue laser beam L1 and the red laser beam L2 In this case, the laser beam light amount adjusting means 40A has a configuration using only the plurality of optical members 41 to 43.

  4A and 4B are diagrams schematically showing the entire configuration of the optical pickup device according to the second embodiment of the present invention. FIG. 4A is a left side view, FIG. 4B is a plan view, and FIG. 4C is for BD. FIG. 3D is a front view of the optical system, and FIG. FIG. 5 is an enlarged view of the laser beam light amount adjusting means for the front monitor photodetector shown in FIG. Further, FIG. 6 is a diagram showing the relationship between the incident angle of the blue laser beam and the red laser beam incident on the glass plate and the light transmittance in the optical pickup device according to the second embodiment of the present invention.

  The optical pickup device PU2 of the second embodiment according to the present invention shown in FIG. 4 is different from the optical pickup device PU1 of the first embodiment described above only in the configuration of the laser beam light amount adjusting means 40B. Here, for convenience of explanation, the same reference numerals are given to the constituent members shown above, and the constituent members shown above will be described as necessary and will differ from the first embodiment. A description will be given focusing on the different points by attaching new reference numerals to the constituent members.

  As shown in FIGS. 4A to 4D, the optical pickup apparatus PU2 according to the second embodiment of the present invention also has a short wavelength from the first laser light source (BD laser light source) 11 as in the first embodiment. The first laser beam (blue laser beam) L1 is selectively emitted, and the first laser beam L1 is thinned by the first objective lens (high NA objective lens) 16 having a high numerical aperture (NA). On the first optical recording medium (BD) 1, the light is condensed in the form of a spot. On the other hand, the second laser light source (laser light source for DVD) 21 has a longer wavelength than the first laser beam L 1 and is emitted from the first laser beam. A second laser beam (red laser beam) L2 having a large power is selectively emitted, and the second laser beam L2 has a lower numerical aperture (NA) than the first objective lens 16 (low NA). versus When the light is condensed in a spot shape on the second optical recording medium (DVD) 2 having a substrate thickness larger than that of the first optical recording medium 1 by the lens 26), the first and second laser light sources 11 and 21 and the first and second laser light sources 11 and 21 A front monitor photodetector 31 for monitoring the light amounts of the first and second laser beams L1 and L2 is shared with the first and second laser beams L1 and L2 between the second objective lenses 16 and 26. However, in order to optically adjust the light amount difference between the first and second laser beams L1 and L2 incident on the front monitor photodetector 31, the first embodiment is similar to the first embodiment. Is characterized in that a laser beam light amount adjusting means 40B having a partially different configuration is installed on the laser beam incident side of the front monitor photodetector 31 using a plurality of optical members 41 to 44.

  The laser beam light quantity adjusting means 40B described above constitutes a main part of the second embodiment, and as described above, a plurality of optical members 41 fixedly installed on the laser beam incident side of the front monitor photodetector 31. The optical quantity difference between the blue laser beam L1 and the red laser beam L2 incident on the front monitor photodetector 31 is optically adjusted by the plurality of optical members 41 to 44.

  At this time, the plurality of optical members installed on the laser beam incident side of the front monitor photodetector 31 include a first semi-transmissive / reflective mirror 41, a total reflective mirror 42, a second semi-transmissive / reflective mirror 43, And a glass plate 44.

  Accordingly, in the second embodiment, since the glass plate 44 is added to the first embodiment described above, the sealing transparent optical member 31a (see FIG. 1 and FIG. 2), an example in which the sealing transparent optical member 31a (FIGS. 1 and 2) is provided on the laser beam incident side of the front monitor photodetector 31 as in the first embodiment will be described. ) Is installed and there is no problem.

  As shown in an enlarged view in FIG. 5, in the laser beam light amount adjusting means 40 </ b> B, a part of the blue laser beam L <b> 1 of the P-polarized light emitted from the BD laser light source 11 is reflected by the first semi-transmissive / reflective mirror 41. When the blue laser beam L1 of P-polarized light totally reflected by the total reflection mirror 42 after passing through the glass plate 44 passes through the glass plate 44 and enters the incident surface 31b of the front monitor photodetector 31. The glass plate 44 is installed so that the first incident angle γ of the blue laser beam L1 is incident at, for example, about 45 ° with respect to the normal line standing on the incident surface 44a of the glass plate 44, and the DVD laser light source. A part of the red laser beam L2 of S-polarized light emitted from 21 is transmitted through the second semi-transmissive / reflective mirror 43 and then passed through the glass plate 44 to be incident on the front monitor photodetector 31. When the light is incident on 31b, the second incident angle δ of the red laser beam L2 is larger than the first incident angle γ of the blue laser beam L1 with respect to the normal standing on the incident surface 44a of the glass plate 44, for example, approximately 70 °. A glass plate 44 is installed so as to be incident on the screen.

  In other words, when the first semi-transmissive / reflective mirror 41, the total reflective mirror 42, the second semi-transmissive / reflective mirror 43, and the glass plate 44 are arranged as illustrated, the glass plate 44 So that the first incident angle γ of the blue laser beam L1 of P-polarized light is approximately 45 ° and the second incident angle δ of the red laser beam L2 of S-polarized light is approximately 70 ° to the incident surface 44a. The mounting angle of the glass plate 44 is adjusted.

  In the second embodiment, the first incident angle γ of the blue laser beam L1 is set to approximately 45 ° and the second incident angle δ of the red laser beam L2 is set to approximately 70 ° with respect to the incident surface 44a of the glass plate 44. However, the present invention is not limited to this, and the first and second incident angles γ,... Are adjusted in accordance with the light amount difference between the blue laser beam L1 and the red laser beam L2 and the sensitivity difference depending on each wavelength of each laser beam L1, L2. What is necessary is just to set (delta), respectively.

  At this time, when the blue laser beam L1 of P-polarized light and the red laser beam L2 of S-polarized light are incident on the glass plate 44, the relationship between the incident angles of the laser beams L1 and L2 and the light transmittance is shown in FIG. However, when the glass plate 44 is used, the interface with the air becomes two surfaces of the incident surface 44a and the exit surface 44b of the glass plate 44, so that the blue laser beam L1 and the red laser beam L2 are used. When the glass plate 44 passes through the interface of the glass plate 44 twice, the light transmittance tends to be deteriorated as compared with the case of passing the glass plate 44 once. When the glass plate 44 is used, the incident angle of the blue laser beam L1 and the red laser beam L2 The change in light transmittance with respect to the incident angle also increases as shown in FIG. Therefore, it becomes easier to set a larger light amount difference between the blue laser beam L1 of P-polarized light and the red laser beam L2 of S-polarized light.

  That is, as shown in FIG. 6, when the mark X is a characteristic for the blue laser beam L1 and the mark O is a characteristic for the red laser beam L2, the red laser beam L2 of the S-polarized light incident on the incident surface 44a of the glass plate 44 is obtained. When the second incident angle δ is set larger than the first incident angle γ of the P-polarized light blue laser beam L1, the P-polarized light blue laser beam L1 is incident on the incident surface 44a of the glass plate 44 at approximately 45 °. In this case, since the light transmittance is 98%, the blue laser beam L1 of P-polarized light is incident on the incident surface 44a of the glass plate 44 with a substantially unchanged light amount.

  On the other hand, when the red laser beam L2 of S-polarized light is incident on the incident surface 44a of the glass plate 44 at approximately 70 °, the light transmittance is 40%, so the amount of light of the red laser beam L2 of S-polarized light is attenuated. Then, the light is incident on the incident surface 31b of the front monitor photodetector 31. At this time, it can be seen that a light amount difference of twice or more can be adjusted.

  That is, by adjusting the mounting angle of the glass plate 44, the light transmittance of the blue laser beam L1 of P-polarized light and the light transmittance of the red laser beam L2 of S-polarized light can be freely changed to some extent. .

  In practice, the light path difference between the optical path of the blue laser beam L1 of P-polarized light and the optical path of the red laser beam L2 of S-polarized light is about the gain difference of the assumed front monitor sensitivity adjustment amplifier 32 (FIG. 4). When the optical pickup device PU2 is assembled, the mounting angle of the glass plate 44 is set so that the amplifier 32 (see FIG. 5) is attached to the blue laser beam L1 of P-polarized light and the red laser beam L2 of S-polarized light. It is attached so as to have a light amount difference corresponding to the approximate gain difference of 4).

  Accordingly, the P-polarized light blue laser beam L1 and the S-polarized light red laser beam L2 incident on the glass plate 44 by the plurality of optical members 41 to 44 in the laser beam light amount adjusting means 40B that can obtain the above characteristics. 4 is adjusted so that the difference in the amount of light is approximately equal to the gain difference of the amplifier 32 (FIG. 4) with respect to the two laser beams L1 and L2, so that the gain of the amplifier 32 for adjusting the front monitor sensitivity is used as a feedback resistor. Since the fixed resistor R can be used, the gain adjustment circuit can be simplified and the amplifier 32 can be operated stably.

  Further, since the laser beam light amount adjusting means 40B is installed on the laser beam incident side of the front monitor photodetector 31 using a plurality of optical members 41 to 44, the respective light amounts of the blue laser beam L1 and the red laser beam L2 are provided. Can be stably monitored by the front monitor photodetector 31, and the light quantity difference between the blue laser beam L1 and the red laser beam L2 incident on the front monitor photodetector 31 can be reliably adjusted. 11 and the DVD laser light source 21 are not required to be controlled, so that the number of control terminals of the optical pickup device PU2 (FIG. 4) of the second embodiment can be reduced.

  Further, if the glass plate 44 is further increased to a set of two sandwiching a space, a larger light amount difference can be given even at the same incident angle, and it is necessary even when the incident angle must be set small. A sufficient light quantity difference can be ensured.

  At this time, the glass plate 44 does not need to be coated in particular and is used only for monitoring the amount of light, so that high surface accuracy is not required, and the material can be inexpensive, so that the cost is hardly increased.

  In the second embodiment, similarly to the first embodiment, the blue laser beam L1 is P-polarized light and the red laser beam L2 is S-polarized light, so that each of the laser beams L1 and L2 incident on the glass plate 44 can be obtained. Although the difference in light transmittance due to the difference in each incident angle appears remarkably, the blue laser beam L1 can be S-polarized light and the red laser beam L2 can be P-polarized light, without being limited thereto. Furthermore, it is possible to set both laser beams L1 and L2 to the same polarized light.

  As described above, in the optical pickup devices PU1 and PU2 according to the first and second embodiments of the present invention described in detail, the example in which the BD1 and the DVD2 are applied as the optical recording medium has been described. However, the present invention is limited only to the above-described embodiment. Although not shown here, a third optical recording medium (hereinafter referred to as CD) having a lower density than that of DVD 2 has a substrate thickness from the laser beam incident surface to the information recording surface, for example. When a CD (Compact Disc) formed with a thickness of about 1.2 mm is applied, the emission power is larger than that of the red laser beam L2 in the vicinity of the DVD laser light source 21, and the wavelength is longer than that of the red laser beam L2. A third laser light source (CD laser light source) that emits an infrared laser beam of around 780 nm may be arranged. It is possible to arrange a two-wavelength laser light source in which the laser light source is housed in an integrated package to obtain a three-wavelength pick-up device, and to apply DVD and CD as the first and second optical recording media. Therefore, it is possible to make a pickup device compatible with two wavelengths, and various modifications can be made without departing from the scope of the present invention.

PU1 ... Optical pickup device of Example 1,
PU2 ... Optical pickup device of Example 2,
DESCRIPTION OF SYMBOLS 1 ... 1st optical recording medium (BD), 2 ... 2nd optical recording medium (DVD),
11 ... 1st laser light source (laser light source for BD),
12 ... 1st polarization beam splitter, 12a ... Polarization selective transflective / reflective dielectric multilayer film,
13 ... 1st collimator lens, 14 ... Rising mirror, 15 ... 1/4 wavelength plate,
16 ... 1st objective lens (high NA objective lens), 17 ... 1st photodetector
21 ... Second laser light source (DVD laser light source),
22 ... second polarization beam splitter, 22a ... polarization selective transflective / reflective dielectric multilayer film,
23 ... 2nd collimator lens, 25 ... 1/4 wavelength plate,
26 ... second objective lens (low NA objective lens), 27 ... first photodetector,
30 ... APC (Auto Power Control) means,
31 ... Front monitor photodetector,
31a ... Transparent optical member for sealing, 31a1 ... incident surface, 31b ... incident surface,
32 ... Amplifier, 33 ... Controller, 34 ... Laser drive circuit,
40A: Laser beam light amount adjusting means of Example 1,
40B: Laser beam light amount adjusting means of Example 2,
41 ... 1st transflective mirror, 42 ... Total reflection mirror,
43 ... second semi-transmissive / reflective mirror, 44 ... glass plate, 44a ... incident surface, 44b ... exit surface,
L1: first laser beam (blue laser beam),
L2 ... second laser beam (red laser beam), R ... fixed resistance,
α: a first incident angle of the first laser beam incident on the front monitor photodetector 31;
β ... a second incident angle of the second laser beam incident on the front monitor photodetector 31;
γ: a first incident angle of the first laser beam incident on the glass plate 44,
δ: Second incident angle of the second laser beam incident on the glass plate 44.

Claims (7)

A first laser light source that emits a first laser beam corresponding to the first optical recording medium;
Corresponding to the second optical recording medium having a substrate thickness larger than that of the first optical recording medium, a second laser beam having a larger emission power than the first laser beam and having a longer wavelength than the first laser beam is emitted. A second laser light source,
A front monitor photodetector that receives the first and second laser beams selectively emitted from the first and second laser light sources and monitors the respective light amounts of the first and second laser beams;
A light amount difference between the first and second laser beams that are installed on the laser beam incident side of the front monitor photodetector using a plurality of optical members and are incident on the front monitor photodetector by the plurality of optical members. A laser beam light amount adjusting means for optically adjusting
An optical pickup device comprising:   An amplifier is connected to the output side of the front monitor photodetector, and the light quantity difference between the first and second laser beams is changed by the plurality of optical members in the laser beam light quantity adjusting means. 2. The optical pickup device according to claim 1, wherein the optical pickup device is optically adjusted so as to have a substantially gain difference of the amplifier with respect to a beam.   Of the plurality of optical members used in the laser beam light amount adjusting means, the incident angle of the first laser beam with respect to at least one optical member installed on the laser beam incident side of the front monitor photodetector is a first incident. 3. The optical pickup according to claim 1, wherein the second incident angle is made larger than the first incident angle when the second incident angle is an angle of incidence of the second laser beam. 4. apparatus.   The at least one optical member among the plurality of optical members used in the laser beam light amount adjusting means is in close contact with the laser beam incident side of the front monitor photodetector. Optical pickup device.   The first laser beam is incident on the front monitor photodetector with P-polarized light, while the second laser beam is incident on the front monitor photodetector with S-polarized light. Item 5. The optical pickup device according to Item 3 or Claim 4. Comprising at least one objective lens for condensing the first laser beam and the second laser beam;
The plurality of optical members used for the laser beam light amount adjusting means are:
A sealing transparent optical member attached in close contact with the laser beam incident side of the front monitor photodetector;
A first semi-transmissive / reflective mirror that reflects a part of the first laser beam emitted from the first laser light source to the objective lens side and transmits a remaining part of the first laser beam;
Total reflection that partially reflects the part of the first laser beam that has passed through the first semi-transmissive / reflecting mirror and enters the sealing transparent optical member of the front monitor photodetector at the first incident angle. Mirror,
A part of the second laser beam emitted from the second laser light source is reflected toward the objective lens, and the remaining part of the second laser beam is transmitted to transmit the part of the front monitor photodetector. A second semi-transmissive / reflective mirror that is incident on the transparent optical member for sealing at the second incident angle larger than the first incident angle;
The optical pickup device according to claim 1, 2, or 4. Comprising at least one objective lens for condensing the first laser beam and the second laser beam;
The plurality of optical members used for the laser beam light amount adjusting means are:
A first semi-transmissive / reflective mirror that reflects a part of the first laser beam emitted from the first laser light source to the objective lens side and transmits a remaining part of the first laser beam;
A total reflection mirror that totally reflects a part of the first laser beam transmitted through the first semi-transmissive / reflective mirror;
A second semi-transmissive / reflective mirror that reflects a part of the second laser beam emitted from the second laser light source toward the objective lens and transmits the remaining part of the second laser beam;
A part of the first laser beam totally reflected by the total reflection mirror is incident at a first incident angle and then emitted and incident on the front monitor photodetector and transmitted through the second semi-transmissive / reflective mirror. A glass plate that exits after a part of the second laser beam is incident at a second incident angle larger than the first incident angle and is incident on the front monitor photodetector;
The optical pickup device according to claim 1, wherein the optical pickup device includes:

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