JP2012113785A - Optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup which has a small size and a simple structure, can be easily assembled and can accurately record or reproduce information.SOLUTION: An optical pickup A includes: a substrate 12 mounted in an opposite side to a portion opposing to an optical disk of a chassis 11; spectroscopic means 6 for separating a part of a laser beam before reaching the optical disk as a laser beam for measurement; and a light receiving element FMPD for a front monitor which is mounted on the substrate 12 and measures the quantity of the laser beam for measurement.

Description

  The present invention relates to an optical pickup for reading information on an optical disk, and more particularly to an optical pickup including a light receiving element for a front monitor that monitors the output of a light source.

  In an optical pickup that irradiates light to an optical disk and reproduces or records information, the light amount irradiated to the optical disk is adjusted to fall within a certain range in order to stably reproduce or record information. There is a need. In particular, when reproduction is performed with an optical pickup that can be recorded on the optical disc, a method of increasing the amount of emitted light is employed to suppress noise of laser light from a light source (laser diode). Along with this, the amount of light (objective outgoing light) emitted from the optical pickup to the optical disk also increases, and even if an attempt is made to reproduce the recording optical disk, recording may be performed on the recording optical disk.

  For this reason, in an optical pickup capable of recording information, it is necessary to accurately adjust the light quantity of the objective emission light so as to suppress noise and prevent recording on the recording optical disk when reproducing the recording optical disk. Therefore, a general optical pickup for recording is provided with a sensor (front monitor light receiving element) for detecting the amount of recording light from a light source (laser diode), and the amount of light detected by the front monitor light receiving element is adjusted. Based on the above, the output of the light source is adjusted. Further, by adjusting the amount of light from the light source based on the output from the light receiving element for the front monitor, it is possible to cope with fluctuations in the output due to the temperature of the light source and other influences, and to reproduce or record information. Can be performed stably.

  Various methods are known as a method of detecting the amount of light by the front monitor light receiving element in the optical pickup. For example, among light emitted from a light source, one that detects light deviating from a main optical path through which light used for recording or reproduction passes (see Japanese Patent Application Laid-Open Nos. 2008-10387 and 2009-116956, etc.) ), Or an optical element such as a half mirror or a beam splitter in the optical path, and a part of the light on the optical path is guided to a light receiving element for front monitor (see Japanese Patent Application Laid-Open No. 2009-211789).

  The optical pickup includes a substrate on which a laser driver for driving a connector and a laser diode as a light source is mounted. The front monitor light receiving element is also connected to the substrate via the FPC to supply power and transmit an electric signal converted from the received light by the FPC (Japanese Patent Laid-Open No. 2007-164855). Etc.). Further, in the conventional optical pickup, the substrate is disposed on the side of the base (chassis) of the optical pickup close to the optical disk in order to cool the laser driver by the air flow generated by the rotation of the optical disk.

JP 2008-10387 A JP 2009-116956 A JP 2009-2111789 JP 2007-164855 A

  2. Description of the Related Art In recent years, an optical disc apparatus that records / reproduces information by irradiating light onto an optical disc has been made thinner. As the optical disk device is made thinner, the optical pickup is required to be made thinner, and it is difficult to arrange the substrate on the side of the base (chassis) close to the optical disk. In addition, optical elements such as light sources and mirrors have been highly integrated in order to reduce the thickness of the optical pickup.

  Therefore, it is difficult to arrange the FPC for connecting the front monitor light receiving element and the substrate in the base (chassis) of the optical pickup, and the shape of the FPC is complicated or lengthened. The material was complicated. Further, since the deformation of the FPC is limited or difficult to deform by elastic force, a lot of labor and time are required for attaching the front monitor light receiving element to the base.

  The electrical signal output from the front monitor light receiving element is weak. When the shape of the FPC becomes complicated or lengthened, noise is likely to be mixed into the electric signal, and the electric signal cannot be accurately transmitted to the substrate and the control device connected to the substrate. As a result, the accuracy of adjusting the amount of light emitted from the light source is lowered, and the accuracy of recording / reproducing of the optical disk may be lowered.

  Therefore, an object of the present invention is to provide an optical pickup that has a small and simple configuration, can be easily assembled, and can accurately record or reproduce information.

  To achieve the above object, the present invention provides a chassis, a light source that is attached to the chassis and emits laser light, and an objective lens that is disposed on the side of the chassis facing the optical disk and collects the laser light. An actuator that holds the optical disc so as to face the optical disc and a rising mirror that is attached to the chassis and reflects the laser beam toward the objective lens, and reproduces information by irradiating the optical disc with the laser beam. Alternatively, an optical pickup that performs recording, in which a substrate attached to the opposite side of a portion of the chassis that faces the optical disk, and a part of the laser light before reaching the optical disk are separated as measurement laser light. Means and a light receiving element for front monitor mounted on the substrate for measuring the amount of the laser beam for measurement Eteiru.

  According to this configuration, the FPC for connecting the front monitor light-receiving element and the substrate is unnecessary, and accordingly, the number of members can be reduced accordingly. Further, since the front monitor light receiving element is mounted on the substrate, the front monitor light receiving element can be attached more easily and with higher positional accuracy than when the FPC is used. From these facts, it is possible to obtain an optical pickup with a simple configuration, a small size, a light weight and high accuracy.

  In the above configuration, the optical pickup further includes a falling mirror that reflects the measurement laser light toward the light receiving element for front monitor. Since the falling mirror is provided, it is possible to irradiate the front monitor light receiving element with the measurement laser beam by the falling mirror, so that the mounting angle of the front monitor light receiving element with respect to the substrate is special. It is not necessary to set the angle at a certain angle, and the manufacturing is easy. In addition, since the measurement laser beam is bent and applied to the front monitor light-receiving element, the angle adjustment of the measurement laser light is easy, and the measurement accuracy of the measurement laser light by the front monitor light-receiving element is increased accordingly. Can be increased.

  In the above configuration, the chassis includes a front monitor mounting portion including an inner wall with which a side surface portion of the front monitor light receiving element abuts. According to this configuration, even when the front monitor mounting portion mounted on the substrate is not visible, it can be mounted at an accurate position. In addition, since the substrate is fixed to the chassis after the front monitor light receiving element is positioned on the front monitor mounting portion, the front monitor light receiving element is not easily displaced when the substrate is mounted, and the measurement laser light It can suppress that measurement accuracy falls.

  In the above configuration, the spectroscopic means is a bending mirror that allows a part of the laser light to pass as the measurement laser light and reflects the rest toward the rising mirror.

  In the above configuration, the actuator includes two different objective lenses, and the two objective lenses are arranged side by side in the radial direction of the optical disc.

  In the above configuration, the spectroscopic means and the rising mirror are integrally formed, and the rising mirror is an optical element through which part of the laser light passes as the measurement laser light.

  In the above configuration, the actuator includes two different objective lenses, the two objective lenses are arranged side by side in the circumferential direction of the optical disc, and include two mirrors corresponding to the two objective lenses, respectively. Of the two rising mirrors, the rising mirror farther from the light source is an optical element formed integrally with the spectroscopic means.

  According to the present invention, it is possible to provide an optical pickup that has a small and simple configuration, can be easily assembled, and can accurately record or reproduce information.

It is the perspective view which looked at the optical pick-up concerning this invention from the top. It is the perspective view which similarly looked at the optical pick-up from the bottom. FIG. 3 is a perspective view showing a state where a main board is removed from the optical pickup shown in FIG. 2. It is a figure which shows arrangement | positioning of the optical element with which the optical pick-up concerning this invention is equipped. It is a perspective view of the main board | substrate attached to the optical pick-up concerning this invention. FIG. 4 is an enlarged view of a portion surrounded by a circle VI in FIG. 3. It is the perspective view seen from the other example concerning this invention. It is a figure which shows arrangement | positioning of the optical element with which the optical pick-up shown in FIG. 7 was equipped.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of the optical pickup according to the present invention as viewed from above, FIG. 2 is a perspective view of the optical pickup as viewed from below, and FIG. 3 is a view in which the main substrate is removed from the optical pickup shown in FIG. FIG. 4 is a diagram showing the arrangement of optical elements provided in the optical pickup according to the present invention.

  As shown in FIGS. 3 and 4, the optical pickup A includes a first light source 1, a first half-wave plate 101, a first diffraction grating 102, a second light source 2, and a second half-wave plate. 201, second diffraction grating 202, half mirror 203, polarizing beam splitter 3, quarter wavelength plate 4, collimator lens 5, folding mirror 6, first rising mirror 71, second rising mirror 72, first objective lens 81, a second objective lens 82, a sensor lens 9, a light receiving element PD, a falling mirror 10, and a front monitor light receiving element FMPD.

  As shown in FIGS. 1 and 2, the optical pickup A includes a chassis 11 to which each of the optical elements described above is attached, and a main board 12 attached to the lower surface of the chassis 11 (the surface opposite to the optical disk). ing. The main board 12 includes through holes 121 for screwing at two locations. The main board 12 is fixed to the chassis 11 by the screw passing through the through hole 121 and screwing into the screw hole 111 (see FIG. 3) formed in the chassis 11. The optical pickup A is slidably supported on an axis (not shown) extending in the radial direction and arranged in parallel with the tangential direction. Both end portions of the chassis 11 in the tangential direction are provided with a shaft through hole 112 through which one shaft is slidable and an engagement recess 113 into which the other shaft is slidably engaged. Yes.

  As shown in FIG. 3, among the optical elements described above, the optical elements other than the first rising mirror 71, the second rising mirror 72, the first objective lens 81, and the second objective lens 82 are the bottom surface of the chassis 11. It is arrange | positioned at the recessed part opened to. And the main board | substrate 12 is attached and fixed so that the opening may be covered (refer FIG. 2). By attaching the main board 12, the optical element is arranged in a space sealed by the chassis 11 and the main board 12, so that foreign substances such as dust and dirt can be prevented from entering and adhering to the optical element. . Note that a through hole 122 and a through hole 123 are formed in the main substrate 12. A heat sink 100 for holding the first light source 1 from the through hole 122 and assisting heat dissipation is exposed, and a heat sink 200 for holding the second light source 2 and assisting heat dissipation is exposed from the through hole 122. As described above, the heat sink 100 and the heat sink 200 are exposed from the through hole 122 and the through hole 123 of the main substrate 12, respectively, so that the heat generated in the first light source 1 and the second light source 2 is effectively radiated.

  Further, as shown in FIG. 1, the first objective lens 81 and the second objective lens 82 are provided in the actuator Act. The actuator Act is a drive device that moves the first objective lens 81 or the second objective lens 82 in the radial direction or the approaching / separating direction of the optical disc.

  The optical element of the optical pickup A will be described in detail. The first light source 1 is a laser diode that emits blue laser light (wavelength of about 405 nm) for recording / reproducing BD. Laser light emitted from the first light source 1 enters the first half-wave plate 101. The first half-wave plate 101 is an optical element that changes the polarization direction of the light emitted from the first light source 1. The first half-wave plate 101 blocks the light reflected by the optical disk and irradiates the first light source 1. It has a suppressing effect. The laser beam that has passed through the first half-wave plate 101 is incident on the first diffraction grating 102. The laser light is diffracted by the first diffraction grating 102 and emitted as three beams. These three beams form three spots on the optical disk, and a tracking error signal can be obtained by the DPP method well known in the art.

  The laser light that has passed through the first diffraction grating 102 enters the polarization beam splitter 3. The polarization beam splitter 3 is an optical element corresponding to the laser beam emitted from the first light source 1, that is, the blue laser beam. When the blue laser beam is incident, the optical beam is reflected or transmitted depending on the polarization direction of the incident beam. It is an element. The polarization beam splitter 3 will be described as an optical element that reflects P-polarized light and passes S-polarized light. The laser light that has passed through the first half-wave plate 102 is P-polarized laser light that is reflected by the reflecting surface of the polarizing beam splitter 3 and the optical path is bent.

  On the other hand, the second light source 2 is a laser diode that selectively emits red laser light (wavelength: about 650 nm) for DVD recording / reproduction or infrared laser light (wavelength: about 780 nm) for CD recording / reproduction. The red laser light or infrared laser light emitted from the second light source 2 is incident on the second half-wave plate 201. The second wave plate 201 is an optical element that changes the polarization direction of the light emitted from the second light source 2, and has an effect of blocking the light reflected by the optical disk and suppressing the second light source 2 from being irradiated. have. The red laser light or infrared laser light that has passed through the second half-wave plate 201 is incident on the second diffraction grating 202. Red laser light or infrared laser light is diffracted by the second diffraction grating 202 and emitted as three beams. These three beams form three spots on the optical disk, and a tracking error signal can be obtained by the DPP method well known in the art.

  The red laser light or infrared laser light that has passed through the second diffraction grating 202 is incident on the half mirror 203. A part of the light amount of the red laser light or infrared laser light incident on the half mirror 203 passes through the half mirror 203, and the remaining light amount is reflected and enters the polarization beam splitter 3. As described above, since the polarization beam splitter 3 is an optical element for blue laser light, all (substantially all) incident light amounts pass through the red laser light and the infrared laser light. Note that in the following description, when laser light is described without particular distinction, it refers to all of blue laser light, red laser light, and infrared laser light. That is, when it is simply described as laser light, it is converted by the optical element regardless of the wavelength of the laser light, reflected, and passes through the optical element.

  Laser light emitted from the polarization beam splitter 3 is incident on the quarter-wave plate 4. The quarter wavelength plate 4 is an optical element that shifts the phase of incident light by a quarter wavelength. That is, the quarter-wave plate 4 is an optical element that converts circularly polarized light when the transmitted light is linearly polarized light and linearly polarized light when it is circularly polarized light. As will be described later, the laser light applied to the recording surface of the optical disk (not shown) is circularly polarized light, and the laser light returned to the quarter wavelength plate 4 is converted to linearly polarized light. At this time, the returned laser beam is emitted from the quarter-wave plate 4 with linearly polarized light orthogonal to the laser beam incident on the quarter-wave plate 4 from the polarization beam splitter 3.

  The laser light that has passed through the quarter-wave plate 4 enters the collimator lens 5. The collimator lens 5 is a lens for correcting the aberration of divergent light to obtain parallel light. Note that the collimator lens 5 is movable in the optical axis direction in order to make the light of different wavelengths of the blue laser light, red laser light, and infrared laser light into parallel light accurately. The optical path of the laser beam that has passed through the collimator lens 5 is bent by a bending mirror 6. The optical path of the laser beam is changed from the tangential direction (tan direction) to the radial direction (rad direction) by bending the optical path with the bending mirror 6.

  The folding mirror 6 is a half mirror, and is an optical element through which a part of the incident laser light passes and the rest is reflected. The passed laser light is reflected by the falling mirror 10 and enters the front monitor light receiving element FMPD. The laser light incident on the front monitor light receiving element FMPD will be described later.

  The laser beam reflected by the bending mirror 6 enters the first rising mirror 71. The first rising mirror 71 is a dichroic mirror that reflects light included in a predetermined wavelength band and transmits light in other wavelength bands. The first rising mirror 71 has a characteristic of reflecting blue laser light and passing red laser light and infrared laser light. The first rising mirror 71 reflects blue laser light in the optical disc (BD) direction (rising direction), and the blue laser light reflected by the first rising mirror 71 is incident on the first objective lens 81. The first objective lens 81 is a condensing lens that condenses blue laser light and irradiates the BD recording layer as a laser spot. The numerical aperture of the first objective lens 81 is 0.85. The blue laser light (return light) reflected by the recording layer of the BD returns to the original parallel light by passing through the first objective lens 81, is reflected by the first rising mirror 71, and is reflected on the bending mirror 6. Return.

  On the other hand, when the laser beam reflected by the bending mirror 6 is a red laser beam or an infrared laser beam, it is out of the wavelength band reflected by the first rising mirror 71, so that all or almost all of the light amount is the first. Passes through the rising mirror 71. The red laser light or infrared laser light that has passed through the first rising mirror 71 enters the second rising mirror 72. The second rising mirror 72 is a total reflection type mirror, and red laser light or infrared laser light is reflected by the second rising mirror 72 in the direction of the optical disc (DVD or CD) (rising direction), and the second objective lens. 82 is incident.

  The second objective lens 82 is a condensing lens that condenses incident red laser light or infrared laser light and irradiates the recording layer of the corresponding optical disk (DVD or CD) as a laser spot. The numerical aperture of the second objective lens 82 is 0.6. The red laser light or infrared laser light (return light) reflected by the DVD or CD returns to the original parallel light by passing through the second objective lens 82, and is reflected by the second rising mirror 72 and reflected by the second rising mirror 72. 1 is incident on the rising mirror 71. As described above, since the first rising mirror 71 allows light other than the blue laser light to pass through without reflecting, the red laser light and the infrared laser light pass through the first rising mirror 71 and return to the bending mirror 6.

  The blue laser light reflected by the first rising mirror 71 and the red laser light and infrared laser light that have passed through the first rising mirror 71 enter the bending mirror 6 through the same optical path as the forward path (substantially the same). . Since the folding mirror 6 is a half mirror as described above, a part of the laser light incident on the folding mirror 6 is reflected and enters the collimator lens 5. The laser light incident on the collimator lens 5 is converted from parallel light into convergent light and is incident on the quarter-wave plate 4.

  The laser light incident on the quarter wavelength plate 4 is circularly polarized light and is converted into linearly polarized light when passing through the quarter wavelength plate 4. The linearly polarized light is S-polarized light having a polarization direction orthogonal to the blue laser light (P-polarized light) emitted from the first light source 1 and passed through the half-wave plate 102. The laser beam that has passed through the quarter-wave plate 4 enters the polarization beam splitter 3. Since the blue laser light that has passed through the quarter-wave plate 4 is S-polarized light, the laser light that has passed through the quarter-wave plate 4 passes through the polarization beam splitter 3. Further, red laser light and infrared laser light are also converted into S-polarized linearly polarized light by the quarter-wave plate 4. Since the polarization beam splitter 3 is an optical element corresponding to blue laser light, the red laser light and infrared laser light pass through the polarization beam splitter 3. In some cases, a part of the laser beam is reflected by the polarization beam splitter 3 and travels toward the first light source 1. In this case, the laser beam is also blocked by the half-wave plate 101 that emits P-polarized light and Will not reach.

  The light that has passed through the polarization beam splitter 3 enters the half mirror 203. A part of the laser light is reflected by the half mirror 203 and the rest passes. The laser light reflected by the half mirror 203 is directed toward the second light source 2, but the laser light is S-polarized light, so that it is blocked by the half-wave plate 202 and does not reach the second light source 2. The light that has passed through the half mirror 203 passes through the sensor lens 9 and enters the light receiving element PD. The sensor lens 9 is a lens arranged to generate a focus error signal. For example, a cylindrical lens that condenses laser light in a uniaxial direction is employed.

  The laser light incident on the light receiving element PD is converted into an electric signal by the light receiving element PD. This electrical signal is sent to a control unit (not shown) as a tracking error signal, a focus error signal, a data signal, and the like.

  In an optical disc apparatus, when recording information on a recordable optical disc, the recording layer must be supplied with energy that causes a layer change in the laser beam, and the first light source 1 or the second light source 2 has a high output. It is necessary to emit laser light. When emitting high-power laser light, a large current is supplied to the first light source 1 or the second light source 2 and a laser driver circuit (not shown) that supplies power to these light sources. As a result, the first light source 1, the second light source 2, and the laser driver circuit generate heat, and the temperature of the first light source 1, the second light source 2 itself and the surroundings of the optical pickup also increase. The laser diodes constituting the first light source 1 and the second light source 2 have a characteristic that the fluctuation of the output due to heat becomes large, and it is necessary to adjust the output accurately.

  When reproducing an optical disc on which information has been recorded in advance, the laser beam emitted from the first light source 1 or the second light source 2 is a laser beam reflected by the recording layer of the optical disc (BD, DVD or CD). It is sufficient that the light receiving element PD has a light quantity that can be converted into an electric signal. However, if the amount of laser light is low, the effect of noise increases, so adjustments are made to increase the amount of laser light. If the amount of laser light is increased too much due to this adjustment, recording may be mistaken when a recordable optical disc is played back. As described above, when adjustment is performed to increase the amount of laser light, the amount of laser light is accurately adjusted so that the laser light is not easily affected by noise and is not erroneously recorded on a recordable optical disk. There is a need. During reproduction, the outputs of the laser diodes of the first light source 1 and the second light source 2 vary due to heat. Correction of output fluctuations of the first light source 1 and / or the second light source 2 is also necessary.

  In order to adjust the amount of laser light (blue laser light, red laser light, and infrared laser light) emitted from the first light source 1 and the second light source 2, it is necessary to monitor the light amount of the laser light. Therefore, the optical pickup A includes a front monitor light receiving element FMPD. In the optical pickup A, part of the laser light that has passed through the collimator lens 5 has passed through the bending mirror 6, and the laser light that has passed through is totally reflected by the falling mirror 10 and led to the front monitor light receiving element FMPD. Yes. Based on the light amount of the laser light incident on the front monitor light receiving element FMPD, the light amount of the laser light emitted from the first light source 1 or the second light source 2 is detected.

  Note that the front monitor light receiving element FMPD is an element that converts the amount of laser light into an electrical signal regardless of the wavelength of the laser light, and transmits the converted electrical signal as a front monitor signal to a control device (not shown). ing. The control device refers to the received front monitor signal, detects the amount of laser light emitted from the first light source 1 or the second light source 2, and a laser driver circuit so that the amount of light falls within an appropriate range. Drive. In this way, the control device controls the laser driver circuit to adjust the power (current) supplied to the first light source 1 or the second light source 2, and the light is emitted from the first light source 1 or the second light source 2. The amount of laser light (blue laser light, red laser light, infrared laser light) can be adjusted with high accuracy. The above control device, laser driver circuit, and control of the laser driver circuit by the control device are well known in the art and will not be described in detail.

  A light receiving element for front monitor which is a main part of the present invention will be described with reference to the drawings. 5 is a perspective view of the main board attached to the optical pickup according to the present invention, and FIG. 6 is an enlarged view of a portion surrounded by a circle VI in FIG. In the optical pickup shown in FIGS. 3 and 6, only the front monitor light receiving element mounted on the main board is arranged in the chassis.

  As shown in FIG. 5, the main board 12 is mounted with a socket Sc into which a connector used for signal exchange and power supply is inserted and engaged, and a front monitor light receiving element FMPD. The main board 12 is a surface-mounting board, which is not shown, but has a wiring pattern formed of a thin film of copper or aluminum on the surface. The front monitor light receiving element FMPD is also connected to a terminal provided in the socket Sc by a wiring pattern, and a front monitor signal from the front monitor light receiving element FMPD is sent to the socket Sc through the wiring pattern. It is sent to the control device via the wiring provided with the connector.

  Since the socket Sc and the front monitor light receiving element FMPD are mounted on the main board 12, the socket Sc and the front monitor light receiving element FMPD required when the front monitor light receiving element FMPD is attached to the chassis 11 are provided. Can be omitted.

  The main board 12 is provided with a laser driver circuit (not shown) that drives (supplies power to) the first light source 1 and the second light source 2. The laser driver circuit may be arranged as a one-chip IC, or may have a configuration in which a plurality of ICs are combined. Furthermore, a configuration may be provided in which each light source includes an independent laser driver circuit, and two light sources may be driven by one laser driver. Note that, by optimizing the shape and arrangement of the optical elements, the thickness of the chassis 11 is thinner than the conventional one. As described above, since the chassis 11 is thin, even when the main board 12 is disposed on the side opposite to the optical disk, the airflow caused by the rotation of the optical disk is blown to the laser driver mounted on the main board 12 to be cooled. It is possible.

  Next, a procedure for attaching the main board 12 including the front monitor light receiving element FMPD to the chassis 11 will be described. As described above, among the optical elements provided in the optical pickup A, the optical elements other than the front monitor light receiving element FMPD and the first objective lens 81 and the second objective lens 82 are attached to the chassis 11. The first objective lens 81 and the second objective lens 82 are attached to an actuator Act that moves in the tracking, focusing, and tilt directions. The actuator Act is determined in advance on the chassis 11 by a well-known method. Can be attached to the position with high accuracy

  The front monitor light receiving element FMPD needs to be arranged so that the optical axis of the laser light reflected by the falling mirror 10 is accurately irradiated to the center in order to accurately measure the amount of laser light. Therefore, as shown in FIGS. 3 and 6, a front monitor mounting portion for fixing the side surface portion of the light receiving element FMPD for front monitor in contact with the chassis 11 in the direction in which the laser beam is reflected by the falling mirror 10 is provided on the chassis 11. 114 is formed. As shown in FIG. 6, the front monitor mounting portion 114 is a corner portion having two inner walls extending in the radial direction and the tangential direction.

  The front monitor light receiving element FMPD is a rectangular parallelepiped member. The front monitor light receiving element FMPD is positioned with respect to the falling mirror 10 by bringing the two side surfaces into contact with the two inner walls intersecting the front monitor mounting portion 114. That is, the front monitor light receiving element FMPD positioned by the front monitor mounting portion 114 is accurately irradiated with the laser beam reflected by the falling mirror 10 at the center of the light receiving portion. Therefore, when attaching the main board 12 to the chassis 11, it is possible to position the front monitor light receiving element FMPD at an accurate position with respect to the falling mirror 10 even if the position of the falling mirror 10 is not visible. It is.

  The optical pickup A employs a method of positioning the main board 12 on the chassis 11 by using a method of positioning by the front monitor light receiving element FMPD and the front monitor mounting portion 114. That is, after the front monitor light receiving element FMPD and the socket Sc are mounted on the main board 12 in advance, the side surface portion of the front monitor light receiving element FMPD is brought into contact with the inner wall of the front monitor mounting portion 114. Then, a screw is passed through the through hole 121 formed in the main board 12 and screwed into the screw hole 111 of the chassis 11 to fix the main board 12 to the chassis 11.

  As described above, since the center of the front monitor light receiving element FMPD is accurately arranged on the optical axis of the laser beam reflected by the falling mirror 10, the main board 12 is fixed to the chassis 11, so that the front monitor light receiving is received. The shift due to the attachment of the element FMPD is suppressed, and the front monitor light receiving element FMPD can accurately receive the amount of laser light reflected by the falling mirror 10. Thus, the control device can accurately detect the amount of laser light (blue laser light, red laser light, infrared laser light) emitted from the first light source 1 and the second light source 2, and the first light source It is possible to accurately adjust the output (light quantity) of the laser light emitted from the first or second light source 2.

  Even when the front monitor light receiving element FMPD and the through hole 121 are misaligned in manufacturing the main board 12, the through hole 121 has an effective screw diameter in order to facilitate the screwing of the main board 12. Can be mentioned which are formed to be large.

  As shown in FIGS. 2 and 3, the chassis 11 is formed with a stepped portion 115 that contacts the edge of the main board 12. When the main board 12 is attached to the chassis 11, the main board 12 may be positioned by bringing the edge of the main board 12 into contact with the stepped portion 115. In this case, the positional accuracy between the edge portion of the main substrate 12 that contacts the stepped portion 115 and the front monitor light receiving element FMPD must be high. However, when the main board 12 is attached to the chassis 11, since it cannot be visually observed, the front monitor light-receiving element FMPD is strongly pressed against the chassis 11 or the front monitor attachment portion 114, causing a problem that the damage or destruction occurs. Can be suppressed. A boss may be formed in the chassis 11, a boss hole into which the boss is fitted is formed in the main board 12, and the main board 12 may be positioned on the chassis 11 by fitting the boss and the boss hole. .

  Further, the main board 14 is brought into contact with the stepped portion 115 to determine a rough position of the main board 12 with respect to the chassis 11, and then the side surface of the front monitor light receiving element FMPD is brought into contact with the inner wall of the front monitor mounting portion 114. The final adjustment may be performed. Thus, by positioning in two stages, it is possible to suppress an excessive force from being applied to the front monitor light receiving element FMPD and damage it, and the front monitor light receiving element FMPD and the falling mirror 10 can be prevented. Can be positioned with high accuracy.

  The front monitor mounting portion 114 includes an inner wall extending in the tangential direction and the radial direction. However, the present invention is not limited to this, and the side surface of the front monitor light receiving portion FMPD is held to A device that can accurately position the light receiving unit FMPD on the chassis 11 can be widely used. Further, as long as the front monitor light receiving unit FMPD can be accurately positioned with respect to the falling mirror 10, it does not have to follow the shape of the front monitor light receiving unit FMPD. For example, when the front monitor light receiving unit FMPD has a cylindrical shape, the front monitor mounting portion 114 has a configuration including orthogonal inner walls as shown in FIGS. 3 and 6, and is positioned by contacting a part of the column. Alternatively, the inner wall may have a curved shape along the outer periphery of the front monitor light receiving unit FMPD. As the front monitor mounting portion 114, a configuration that can be positioned so that the laser beam reflected by the falling mirror 10 can be accurately received by the front monitor light receiving portion FMPD can be widely employed.

  Another example of the optical pickup according to the present invention will be described with reference to the drawings. 7 is a top perspective view of another example according to the present invention, and FIG. 8 is a diagram showing the arrangement of optical elements provided in the optical pickup shown in FIG. In the optical pickup B shown in FIGS. 7 and 8, the first objective lens 81 and the second objective lens 82 are arranged in the tangential direction (disposed tangentially). In an optical pickup provided with two objective lenses, it is difficult to perform DPP tracking. Therefore, a tracking method using a special hologram is adopted.

  That is, in the optical pickup B, the first diffraction grating 102, the second diffraction grating 202, and the bending mirror 6 are omitted. In the optical pickup B, between the half mirror 203 and the light receiving element PD (in the optical pickup B, it is between the sensor lens 9 and the light receiving element PD, but may be between the half mirror 203 and the sensor lens 9). A hologram HOE is arranged. The first rising mirror 71 is a half mirror through which part of the blue laser light passes, and the second rising mirror 72 is a half mirror configured to pass through part of the laser light. The rest of the configuration is the same as that of the optical pickup A, and substantially the same parts are denoted by the same reference numerals. Detailed descriptions of substantially the same parts are omitted.

  As shown in FIG. 8, the laser light that has passed through the collimator lens 5 travels straight and enters the first rising mirror 71. The first rising mirror 71 is an optical element that reflects part of the blue laser light and passes the rest. Further, the red laser beam and the infrared laser beam pass through the first raising mirror 71. Then, the laser light that has passed through the first rising mirror 71 enters the second rising mirror 72. The second rising mirror 72 is an optical element that reflects part of the red laser light and infrared laser light and passes the rest. Further, the blue laser light passes through the second rising mirror 72. The laser light that has passed through the second rising mirror is reflected by the falling mirror 10 and enters the front monitor light receiving element FMPD.

  On the other hand, part of the laser light reflected by the recording layer of the optical disk is reflected by the half mirror 203, and part of the laser light passes through the half mirror 203 and enters the sensor lens 9. The laser light incident on the sensor lens 9 is condensed in a uniaxial direction and enters the hologram HOE. The laser beam incident on the hologram HOE is corrected for aberrations and incident on the light receiving element PD.

  As described above, even if the two objective lenses are tangentially arranged, a part of the laser light reaching from the light source to the optical disk is branched and bent to the opposite side of the optical disk, so that the chassis 11 is opposite to the optical disk. It is possible to guide to the front monitor light receiving element FMPD mounted on the main board 12 attached to the main board 12. As a result, even with an optical pickup in which two objective lenses are tangentially arranged, the front monitor light receiving element FMPD can be mounted on the main substrate 12, and the FPC that has been conventionally used as a signal line is omitted. It is possible.

  The front monitor light receiving element FMPD can be positioned by the same method as the optical pickup A in which the objective lenses are arranged in the radial direction, and the first light source 1 or the optical pickup B in which the objective lenses are arranged in the tangential direction can be used. It is possible to accurately detect the amount of laser light from the second light source 2.

  In the above embodiment, the optical pickup has been described as an example having two types of light sources (three types of laser beams to be emitted), but is not limited thereto, and one type of laser is used. It may be provided with one light source that emits light, or may be provided with three or more light sources that emit three or more types of laser light.

  The present invention can be used for an optical pickup provided in an optical disc apparatus.

DESCRIPTION OF SYMBOLS 1 1st light source 100 Heat sink 101 1st 1/2 wavelength plate 102 1st diffraction grating 2 2nd light source 200 Heat sink 201 2nd 1/2 wavelength plate 202 2nd diffraction grating 203 Half mirror 3 Polarizing beam splitter 4 1 / Four-wavelength plate 5 Collimator lens 6 Bending mirror 71 First rising mirror 72 Second rising mirror 81 First objective lens 82 Second objective lens 9 Sensor lens 10 Falling mirror PD Light receiving element FMPD Front monitor light receiving element 11 Chassis 111 Screw hole 112 Shaft through hole 113 Shaft engaging portion 114 Front monitor mounting portion 115 Stepped portion 12 Main chassis 121 Through hole 122 Through hole 123 Through hole Sc Socket

Claims (7)

The chassis,
A light source attached to the chassis and emitting laser light;
An actuator disposed on a side of the chassis facing the optical disc and holding an objective lens for condensing the laser light so as to face the optical disc;
An optical pickup that is attached to the chassis and reflects the laser beam toward the objective lens, and reproduces or records information by irradiating the optical disc with the laser beam,
A substrate mounted on the opposite side of the portion of the chassis facing the optical disc, a spectroscopic means for separating a part of the laser beam before reaching the optical disc as a measuring laser beam, and mounted on the substrate for the measurement An optical pickup comprising a front monitor light receiving element for measuring the amount of laser light for use.   The optical pickup according to claim 1, further comprising a falling mirror that reflects the measurement laser light toward the front monitor light-receiving element.   3. The optical pickup according to claim 1, wherein the chassis includes a front monitor mounting portion including an inner wall with which a side surface portion of the front monitor light receiving element abuts.   The light according to any one of claims 1 to 3, wherein the spectroscopic means is a bending mirror that allows a part of the laser light to pass as the measurement laser light and reflects the rest toward the rising mirror. pick up. The actuator comprises two different objective lenses,
The optical pickup according to claim 4, wherein the two objective lenses are arranged side by side in a radial direction of the optical disc.   The said spectroscopic means and the said raising mirror are integrally formed, The said raising mirror is an optical element through which a part of laser beam passes as said measuring laser beam. The optical pickup described in 1. The actuator comprises two different objective lenses,
The two objective lenses are arranged side by side in the circumferential direction of the optical disc;
Two mirrors corresponding to each of the two objective lenses,
7. The optical pickup according to claim 6, wherein, of the two rising mirrors, a rising mirror farther from the light source is an optical element formed integrally with the spectroscopic means.

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