JP2008251113A - Optical head device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely correct aberration, to adjust a position of a laser light source, to make adhering and fixing operation easy, and to secure an installation space of a light receiving element for monitor. <P>SOLUTION: In the optical head device 1, a first laser beam is made incident on a first beam splitter 521 of a parallel flat plate type from a diagonal direction, the transmission light is guided to an optical recording medium 5 through an objective lens 54, and the reflected light is guided to a light receiving element 45 for monitor. A first laser light source 31 and the light receiving element 45 for monitor are positioned at an incident plane side of the first laser beam of the first beam splitter 521, and a mirror 53 and the objective lens 54 are positioned at an out-going side of the first laser beam. It is easy to secure an installation space at the incident plane side of the first beam splitter, though the light receiving element 45 for monitor is arranged, it is easy that the first laser beam light source 31 can be approached to a side of the light receiving element 45 for monitor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical head device for reproducing and / or recording an optical recording medium such as a CD or a DVD.

  An optical head device used for reproduction and recording of optical recording media having different thicknesses such as CD and DVD includes two sets of laser light sources having different wavelengths, and guides laser light emitted from the respective laser light sources to a common optical path, It is made to converge on an optical recording medium through a common objective lens. The return light component of each laser beam from the optical recording medium is separated from the laser beam on the emission side on the common optical path and guided to the light receiving element. Two beam splitters are used to guide each laser beam to a common optical path and to separate the return light component of each laser beam from the exit side laser beam. Patent Document 1 discloses a two-light source optical pickup using two inexpensive parallel plate beam splitters as a beam splitter instead of a cube beam splitter (prism).

In the optical pickup disclosed herein, the laser beam for CD recording / reproducing is reflected by the parallel plate type first beam splitter and guided to the optical recording medium side, and the laser beam for DVD reproduction is the other parallel plate type. After being reflected by the second beam splitter, it passes through the first beam splitter and is guided to the optical recording medium. The return light components of the respective laser beams reflected by the optical recording medium are sequentially transmitted through both beam splitters and guided to the light receiving element.
JP 2002-15456 A

  In the optical pickup disclosed in Patent Document 1, a substantially linear optical path is formed between the optical recording medium and the light receiving element, and two parallel plate beam splitters are disposed obliquely therewith, with respect to the optical path. The optical system has an arrangement structure in which a laser light source is arranged at a side position of each beam splitter on the same side. In the optical system of this arrangement configuration, when a light receiving element for monitoring for controlling the light emission of a laser light source for CD recording / reproducing on the side close to the optical recording medium, a so-called front monitor is arranged, it is opposed to the laser light source. It is necessary to arrange at a position in front of the first beam splitter.

  However, a laser light source for CD recording / reproduction, a rising mirror, an objective lens, an objective lens driving mechanism, and the like are arranged in front of the first beam splitter, and generally there is no room for installation space. Further, in order to widen the distance between the two laser light sources, the laser light source for CD recording / reproducing is disposed at a position moved forward from the side of the first beam splitter. The distance to the side is narrow. Therefore, in the configuration disclosed in Patent Document 1, it is possible to secure the mounting allowance for two parallel plate beam splitters, widen the interval between the two laser light sources, and secure the space for arranging the front monitor. Have difficulty.

  In view of these points, the present invention has been made in view of the above points. In a two-light source optical head using a parallel plate type beam splitter as an optical path synthesizing element, it is possible to reliably correct aberrations and to adjust the position of the laser light source and to fix the adhesive. And to secure a space for installing a light receiving element for monitoring.

In order to solve the above problems, the present invention includes a first laser light source that emits a first laser beam, a second laser light source that emits a second laser beam having a wavelength different from that of the first laser beam, and these The first laser beam and the second laser beam are arranged to guide the return light component of each laser beam that is reflected by the optical recording medium and returned through the objective lens to the light receiving element. In an optical head device having a first beam splitter and a second beam splitter,
The first beam splitter is a parallel plate beam splitter,
The first laser light emitted from the first laser light source is partially transmitted from the oblique direction to the first beam splitter and guided to the objective lens;
The second laser light emitted from the second laser light source is sequentially reflected by the second beam splitter and the first beam splitter and guided to the objective lens;
Respective return light components of the first laser light and the second laser light are reflected by the first beam splitter and guided to the second beam splitter, transmitted through the second splitter and guided to the light receiving element,
The first laser light emitted from the first laser light source is partially reflected by the first beam splitter and guided to a light receiving element for monitoring;
The first laser light source and the second laser light source are arranged on the same side with respect to the optical path of the return light component from the first beam splitter toward the light receiving element,
The incident angle of the first laser beam emitted from the first laser light source to the first beam splitter is set to an angle of less than 45 degrees.

  Here, in order to reduce the size and cost of the apparatus, it is desirable that the second beam splitter is a parallel plate type beam splitter.

  In addition, when the aberration generated when the first laser light passes through the first beam splitter is corrected by an aberration correction lens disposed between the first laser light source and the first beam splitter, 1 A laser light source and the aberration correction lens are fixed to a common holder to form a light source unit whose relative position is predetermined, and the light source unit is positioned and bonded to a unit mounting portion formed on the apparatus frame. It is desirable to fix.

  In this case, the light source unit includes at least one spacer for adjusting the distance between the light emitting point of the first laser light source and the lens center of the aberration correction lens, and the first It is desirable that at least one of one laser light source and the correction lens is fixed to the holder.

  The light source unit mounted on the unit mounting portion is movable by a predetermined amount around the optical axis direction, the direction orthogonal to the optical axis, and the orthogonal axis passing through the optical axis. It is desirable that the light source unit is bonded and fixed to the unit mounting portion in a state in which the position adjustment of the light source unit mounted on is performed in a three-dimensional manner.

  Furthermore, it is desirable to use a toric lens as the aberration correction lens. The toric lens may be a magnification conversion lens that sets a magnification from the first laser light source to the optical recording medium to a predetermined value.

  In the optical head device of the present invention, the first laser beam is incident on the parallel plate type first beam splitter from an oblique direction, the transmitted light is guided to the optical recording medium through the objective lens, and the reflected light is received for monitoring. It leads to the element. Therefore, the first laser light source and the monitoring light receiving element are located on the incident surface side of the first laser light in the first beam splitter, and the objective lens is located on the emission side of the first laser light.

  On the other hand, when the optical system is configured such that the first laser beam is reflected by the parallel plate type first beam splitter and guided to the optical recording medium through the objective lens, the incident surface of the first beam splitter is used. On the side, the first laser light source, the light receiving element for monitoring, and the objective lens are located. Therefore, it is often difficult to secure an installation space for arranging them on the incident surface side of the first beam splitter.

  In particular, when the incident angle of the first laser beam to the first beam splitter is set to be less than 45 degrees and the interval between the first laser beam and the second laser beam is increased, the first laser light source is connected to the monitor light receiving element or the objective lens. There is a risk that they will interfere with each other. For this reason, the incident angle of the first laser beam may not be less than 45 degrees.

  In the present invention, as described above, the first laser light is transmitted through the first beam splitter and guided to the objective lens, so that the first laser light source and the light receiving for monitoring are provided on the incident surface side of the first beam splitter. The element is positioned, and the objective lens is positioned on the opposite exit surface side. Therefore, it is easy to secure an installation space on the incident surface side of the first beam splitter. Therefore, even when the light receiving element for monitoring is arranged, it is easy to bring the first laser light source closer to the light receiving element for monitoring.

  As a result, the incident angle of the first laser beam with respect to the first beam splitter is set to be less than 45 degrees, the transmission optical path length of the first laser beam passing through the first beam splitter is shortened, and this occurs when the first laser beam is transmitted. Aberrations can be reduced.

  In addition, by making the incident angle of the first laser light less than 45 degrees in this way, the arrangement position of the first laser light source moves in a direction away from the second laser light source, and the distance between these laser light sources is wide. Become. Therefore, it is possible to secure a space for placing a jig used to position and attach these laser light sources to the apparatus frame, and a space for facilitating adhesive application work, positioning these laser light sources, and Bonding and fixing work is facilitated. In particular, when the first laser light source is unitized and is three-dimensionally adjusted and bonded and fixed to the apparatus frame, the space for the position adjusting jig can be secured, and the first light source unit can be accurately obtained. To reliably correct the aberration and form a good light spot on the optical recording medium, thereby ensuring the reliability of the apparatus.

  Embodiments of an optical head device to which the present invention is applied will be described below with reference to the drawings.

(overall structure)
1A, 1B, and 1C are a plan view, a side view, and a bottom view of a state in which a bottom cover and the like are removed, respectively, of an optical head device to which the present invention is applied. The optical head device 1 according to the present embodiment can record and reproduce information with respect to a CD-type disc and a DVD-type disc by using a first laser beam having a wavelength of 780 nm and a second laser beam having a wavelength of 650 nm. This is a two-wavelength optical head device.

  The optical head device 1 has a metal or resin device frame 2 made of a die-cast product such as magnesium or zinc. A first bearing portion 21 and a second bearing portion 22 that engage with a guide shaft and a feed screw shaft (part indicated by an imaginary line in FIG. 1A) of the disk drive device are engaged with each of both ends of the device frame 2. The optical head device 1 can reciprocate in the disk radial direction indicated by the arrow A. One side end face 23 in the moving direction of the device frame 2 is curved in a substantially arc shape to prevent interference when approaching a spindle motor (not shown) of the disk drive mechanism.

  In the apparatus frame 2, an objective lens 91 is disposed at a substantially central portion on the upper surface side. The apparatus frame 2 includes an objective lens driving mechanism 9 that servo-controls the position of the objective lens 91 in the focusing direction and the tracking direction. The objective lens 91 is a common objective lens used for recording and reproduction by the first laser beam and the second laser beam. For example, a two-wavelength lens in which a diffraction grating is formed by concentric grooves or steps. Is used.

  As the objective lens driving mechanism 9, for example, a wire suspension type can be used. As the objective lens driving mechanism 9, a well-known one can be used, and detailed description thereof will be omitted. However, a lens holder that holds the objective lens 91, and the lens holder with a plurality of wires in the tracking direction and A holder support portion that is movably supported in the focusing direction and a yoke fixed to the apparatus frame 2 are provided. The objective lens drive mechanism 9 includes a magnetic drive circuit including a drive coil attached to the lens holder and a drive magnet attached to the yoke. By controlling energization of the drive coil, the lens holder Is driven in the tracking direction and the focusing direction with respect to the optical recording medium. The objective lens driving mechanism 9 can also perform tilt control for adjusting the tilt of the objective lens 91 in the jitter direction. The periphery of the objective lens 91 is covered with a rectangular frame-shaped actuator cover 90.

  The apparatus frame 2 is provided with a flexible substrate 81 on which a connector 6 and the like are mounted. Via the flexible substrate 81, first and second laser light sources 31, 32 and signals to be described later are provided. The detection light receiving element 40 is supplied with power or a signal.

(Configuration of optical system)
FIG. 2 is a schematic configuration diagram showing an optical system of the optical head device 1. In FIG. 2, the portion above the position indicated by the alternate long and short dash line B is a portion arranged in a direction orthogonal to the paper surface, but is shown in a state of being developed on a plane.

  As shown in FIGS. 1C and 2, an AlGaInP-based laser that emits a first laser beam is provided on the side end face opposite to the side end face 23 that is curved in an arc shape in the apparatus frame 2. A first laser light source 31 having a diode and a second laser light source 32 having an AlGaAs laser diode that emits a second laser light are mounted. The first laser light source 31 is unitized and mounted on a unit mounting portion 25 formed on the apparatus frame 2, and after being adjusted in position, is bonded and fixed to the apparatus frame 2. On the other hand, the second laser light source 32 is press-fitted and fixed to a press-fit portion 26 formed in the apparatus frame 2.

  Here, the first laser light source 31 is unitized as follows. As shown in FIG. 2, the first laser light source 31 is fixed to the rear end side of the cylindrical holder 110, and an aberration correction lens 50 (described later) is fixed from the front end side to constitute the light source unit 100. Further, a spacer ring 120 is attached between the first laser light source 31 and the cylindrical holder 110 as necessary.

  The unit mounting portion 25 of the apparatus frame 2 is slightly larger than the light source unit 100, and the light source unit 100 mounted on the unit mounting portion 25 has an optical axis direction, a direction orthogonal to the optical axis, and the optical axis. A predetermined amount can be moved around the orthogonal axis. The light source unit 100 mounted on the unit mounting portion 25 is adhesively fixed to the unit mounting portion 25 after its position is adjusted three-dimensionally. The spacer ring 120 is attached to adjust the distance between the light emitting point of the first laser light source 31 and the lens center of the aberration correction lens 50.

  Next, as the optical paths of the first and second laser beams, the first forward path L1 from the first laser light source 31 to the recording surface of the optical recording medium 5 and the second laser light source 32 to the recording surface of the optical recording medium 5 are used. A second forward path L2 is formed. Further, a return path L3 is formed in which the return light reflected from the recording surface of the optical recording medium 5 travels to the signal detection light receiving element 40.

  In the first forward path L1, the first diffraction grating 511 that diffracts the first laser light emitted from the first laser light source 31 into three beams for tracking detection, and the laser light separated into three beams by the first diffraction grating 511 A parallel plate type first beam splitter 521 that partially transmits the first beam splitter 521 and a rising mirror 53 that raises the laser beam that has passed through the first beam splitter 521 toward the optical recording medium 5 are disposed. Above the rising mirror 53, a collimating lens 54 that converts laser light into parallel light and an objective lens 91 that converges the parallel light from the collimating lens 54 onto the recording surface of the optical recording medium 5 are disposed.

  In the second forward path L2, a second diffraction grating 512 that diffracts the second laser light emitted from the second laser light source 32 into three beams for tracking detection, and a laser beam separated into three beams by the second diffraction grating 512 And a parallel plate type second beam splitter 522 that partially reflects the light beam. The second laser beam partially reflected by the second beam splitter 522 is partially reflected by the first beam splitter 521, and then passes through the rising mirror 53, the collimator lens 54, and the objective lens 91 in the same manner as the first laser beam. The recording surface of the optical recording medium 5 is irradiated. Therefore, a common optical path is from the first beam splitter 521 to the optical recording medium 5.

  The return light returning along the return path L3 also returns to the first beam splitter 521 via the common optical path. The return light is reflected by the first beam splitter 521, passes through the second beam splitter 522, is given astigmatism by the detection lens 56, and then reaches the signal detection light receiving element 40.

  As shown in FIGS. 1C and 2, a monitor light receiving element 45 (front monitor) is disposed in the vicinity of the first laser light incident surface side of the first beam splitter 521. The reflected light component of the first laser beam partially reflected on the incident surface of the first beam splitter 521 is received by the monitor light receiving element 45, and feedback control of the emission intensity of the first laser light source is performed based on the received light amount. Can be done.

  Thus, the first beam splitter 521 is an optical path combining element for guiding the first laser light and the second laser light to the common optical path, and the second beam splitter 522 transmits each return light from the second laser light on the emission side. This is an optical path separation element for separating and guiding the light detection element 40 for signal detection. Therefore, the first beam splitter 521 has an optical characteristic of transmitting approximately 50% of the first laser light, reflecting approximately 50%, and reflecting the second laser light substantially totally. The second beam splitter 522 The optical characteristic is such that one laser beam is substantially totally transmitted, the second laser beam is transmitted approximately 50%, and approximately 50% is reflected. The first and second beam splitters 521 and 522 are inclined in the same direction, and the first and second laser light sources 31 and 32 stand on the same side, that is, stand up with respect to the optical path portion therebetween. It is arranged at the part of the apparatus frame 2 on the side opposite to the side where the raising mirror 53 and the objective lens 54 are arranged.

  Next, an aberration correction lens 50 that is an aberration correction lens is disposed between the first laser light source 31 and the first diffraction grating 511 on the first forward path L1. The aberration correction lens 50 corrects aberrations (coma and astigmatism) that occur when the first laser light emitted from the first laser light source 31 passes through the first beam splitter 521 obliquely as divergent light. belongs to. As the aberration correction lens 50, for example, a toric lens is used. In the toric lens, the lens surface on the first laser light source 31 side is a concave surface 50a, and the lens surface on the other side is a toric surface 50b.

  The aberration correction lens 50 (toric lens) is disposed in a state inclined by a predetermined angle with respect to the emission optical axis of the first laser light source 31, and the concave surface 50 a and the toric surface 50 b are projected from the first laser light source 31. It is inclined by a predetermined angle from the optical axis of the incident light. Therefore, the aberration correction lens 50 is opposite to the coma aberration generated when the first laser light passes through the first beam splitter 521 due to the inclination of the concave surface 50a and the toric surface 50b with respect to the central optical axis of the first laser light. And the coma aberration when the first laser light passes through the first beam splitter 521 is corrected. Further, the aberration correction lens 50 generates coma aberration opposite to astigmatism generated when the first laser light passes through the first beam splitter 521 due to the anisotropy of the radius of curvature of the toric surface 50b. Astigmatism when the first laser beam passes through the first beam splitter 521 is corrected.

  Here, the optical magnification in the second forward path L2 from the second laser light source 32 toward the optical recording medium 5 is set to 6.5 to 7.5, for example. The optical magnification in the first forward path L1 from the first laser light source 31 toward the optical recording medium is preferably set to 3.5 to 5.0 times, for example. However, in the first forward path L1 and the second forward path L2, the collimating lens 54 and the objective lens 91 are shared, and there are restrictions on the layout. Therefore, the toric lens used as the aberration correction lens 50 is used as a magnification conversion lens for the first laser light, and the first forward path L1 from the first laser light source 31 toward the optical recording medium 5 is performed by the aberration correction lens 50 (toric lens). The optical magnification is optimized.

  As described above, the first laser light source 31 and the aberration correction lens 50 are fixed to the common cylindrical holder 110 to constitute the light source unit 100, and the light source unit 100 is three-dimensionally attached to the unit mounting portion 25 of the apparatus frame 2. After being adjusted in position, it is bonded and fixed. Therefore, the first laser light source 31 and the aberration correction lens 50 are positioned with high accuracy in advance. The light source unit 100 is three-dimensionally adjusted and bonded and fixed to the apparatus frame 2 with high accuracy. Therefore, aberration correction can be performed reliably and a good light spot can be formed on the optical recording medium 5.

  Next, the incident angle θ1 of the first laser beam to the first beam splitter 521 is set to an inclination angle of less than 45 °. For example, it is set to 40 °. For this reason, the optical path length through which the first laser beam passes through the first beam splitter 521 can be shortened, and the first laser beam is incident on the first beam splitter 521 by the amount close to perpendicular incidence. The aberration that occurs when passing through 521 is small. Although the incident angle θ2 of the second laser beam to the second beam splitter 522 is 45 °, the incident angle θ3 of the second laser beam to the first beam splitter 521 is the first beam of the first laser beam. It is set to the same angle as the incident angle θ1 to the splitter 521, for example, 40 °.

  Thus, since the incident angle θ1 of the first laser light is 40 ° and the incident angle of the second laser light is 45 °, the first laser light source is compared with the case where both of these incident angles are 45 °. The position 31 is moving away from the second laser light source 32. As a result, the distance between the first and second laser light sources 31 and 32 is widened, and the laser light sources 31 and 32 are arranged in a direction extending toward the rear thereof. Therefore, when these first and second laser light sources 31 and 32 are position-adjusted and fixed to the apparatus frame 2, a space for inserting a position adjusting jig and a space for performing an adhesive fixing operation are secured. .

  When the incident angle θ1 of the first laser light is less than 45 °, the position of the monitor light receiving element 45 is also moved to the first laser light source 31 side, and the interval therebetween is narrowed. However, only the first laser light source 31 and the monitor light receiving element 45 are arranged on the incident surface side of the first beam splitter 521, and the laser light source, the monitor light receiving element, and the objective lens are directed to the incident surface side. As in the case where a rising mirror for raising the laser beam is arranged, there is no room for the installation space for these components, and there is no adverse effect that they interfere with each other.

  The incident angle θ1 of the first laser beam is set to 40 °, and the angle difference between the emission directions of the first laser beam and the second laser beam is set to 5 °, but this angle difference is limited to 5 °. is not. The optical head device 1 should be designed so as to have an optimum angle difference from the thickness of the entire device required for the optical head device 1 and the size of other components used.

  On the other hand, a half-wave plate 46 is integrally formed on the exit-side surface of the three-beam generating diffraction grating 511 arranged in the first forward path L1. The polarization plane direction of the first laser light emitted from the first laser light source 31 is adjusted by the half-wave plate 46, and when entering the reflection surface 53a of the rising mirror 53, the incident direction and the reflection direction are determined. It is adjusted to be in a direction inclined by 45 degrees with respect to the vertical surface of the reflection surface 53a. The reflecting surface 53a of the rising mirror 53 is designed so that the phase difference generated when both laser beams are reflected is π (2n + 1) / 2 (n = 0, 1, 2,...) Both laser beams incident in a state where the polarization plane direction is inclined by 45 degrees are converted into circularly polarized light after reflection. In this way, the information reading performance is improved by bringing the light spot formed on the optical recording medium 5 close to circularly polarized light. Further, the half-wave plate 46 is integrally formed on the surface of the diffraction grating 511, so that cost reduction is achieved.

(Operational effect of the present embodiment)
As described above, in the optical head device 1 according to the actual embodiment, the first forward path L1 from the first laser light source 31 to the rising mirror 53 is substantially linear, and the first beam of the parallel plate type is inclined obliquely thereto. The splitter 521 is disposed as an optical path combining element, and the first laser beam is partially transmitted obliquely through the first beam splitter 521 and guided to the optical recording medium 5 side.

  Accordingly, the monitoring light receiving element 45 for receiving the reflected light component of the first laser light incident on the first beam splitter 521 sandwiches the first beam splitter 521 and is opposite to the rising mirror 53 and the objective lens 54. The first laser light source 31 is disposed on the same side. Therefore, even if the first laser light source 31 is moved to the monitor light receiving element 45 side in order to widen the distance between the first laser light source 31 and the second laser light source 32, the arrangement space of the monitor light receiving element 45 is changed to other optical elements. It can be secured easily without interfering with parts.

  As a result, the incident angle θ1 of the first laser beam with respect to the first beam splitter 521 is set to be less than 45 °, the transmission optical path length of the first laser beam passing through the first beam splitter 521 is shortened, and the first laser beam Aberrations that occur during transmission can be reduced.

  In addition, since the incident angle θ1 of the first laser light can be made less than 45 in this way, the arrangement position of the first laser light source 31 moves in a direction away from the second laser light source 32, and the distance between these laser light sources is increased. Become wider. Therefore, it is possible to secure a space for placing a jig used to position and attach these laser light sources 31 and 32 to the apparatus frame 2, and the position adjustment and adhesion fixing work of these laser light sources 31 and 32 are facilitated. In particular, when the first laser light source 31 is unitized and is three-dimensionally adjusted and bonded and fixed to the apparatus frame, a space for a position adjusting jig can be secured and the light source unit 100 can be accurately obtained. Can be reliably corrected to form a good light spot on the optical recording medium 5, so that the reliability of the apparatus is ensured.

  In addition, the optical head device 1 according to the present embodiment uses the parallel plate type first and second beam splitters 521 and 522 as the light combining element and the optical path separating element. The cost can be reduced as compared with the case where a prism is used as the optical path separation element.

  In the above-described embodiment, the toric lens having the toric surface 50b on one side is used as the aberration correction lens 50. However, instead of this, a cylindrical lens may be used. Further, although the configuration is such that both coma and astigmatism are corrected by one aberration correction lens 50, a configuration in which coma and astigmatism are corrected by separate aberration correction elements may be employed. Furthermore, although the aberration correction lens 50 has a configuration having an aberration correction function and an optical magnification change function, a configuration in which the aberration correction function and the optical magnification change function are respectively assigned to separate elements may be adopted.

(A), (B), and (C) are a plan view, a side view, and a bottom view of the optical head device to which the present invention is applied, with the bottom cover and the like removed. It is a schematic block diagram which shows the optical system of the optical head apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical head apparatus 2 Apparatus frame 21 1st bearing part 22 2nd bearing part 23 Side end surface 25 Unit mounting part 26 Press-fit part 31 1st laser light source 32 2nd laser light source 40 Light receiving element 45 for signal detection Light receiving element for monitoring 46 Half-wave plate 5 Optical recording medium 50 Aberration correction lens 50a Concave surface 50b Toric surface 511 First diffraction grating 512 Second diffraction grating 521 Parallel plate type first beam splitter 522 Parallel plate type second beam splitter 91 Objective lens 100 Light source unit 110 Cylindrical holder 120 Spacer ring L1 First forward path L2 Second forward path L3 Return path θ1 Incident angle θ2 of the first laser beam with respect to the first beam splitter Incident angle of the second laser beam with respect to the second beam splitter

Claims (6)

A first laser light source that emits the first laser light, a second laser light source that emits a second laser light having a wavelength different from that of the first laser light, and the first laser light and the second laser light are used as a common objective. A first beam splitter and a second beam splitter arranged to guide the return light component of each laser beam guided to the lens, reflected by the optical recording medium and returned via the objective lens, to the light receiving element; In the optical head device
The first beam splitter is a parallel plate beam splitter,
The first laser light emitted from the first laser light source is partially transmitted from the oblique direction to the first beam splitter and guided to the objective lens;
The second laser light emitted from the second laser light source is sequentially reflected by the second beam splitter and the first beam splitter and guided to the objective lens;
Respective return light components of the first laser light and the second laser light are reflected by the first beam splitter and guided to the second beam splitter, transmitted through the second splitter and guided to the light receiving element,
The first laser light emitted from the first laser light source is partially reflected by the first beam splitter and guided to a light receiving element for monitoring;
The first laser light source and the second laser light source are arranged on the same side with respect to the optical path of the return light component from the first beam splitter toward the light receiving element,
An optical head device characterized in that an incident angle of the first laser light emitted from the first laser light source to the first beam splitter is an angle of less than 45 degrees. The optical head device according to claim 1,
An optical head device characterized in that the second beam splitter is a parallel plate beam splitter. The optical head device according to claim 1,
Aberration that occurs when the first laser light passes through the first beam splitter is corrected by an aberration correction lens disposed between the first laser light source and the first beam splitter,
The first laser light source and the aberration correction lens are fixed to a common holder to constitute a light source unit in which the relative position is determined in advance.
An optical head device characterized in that the light source unit is positioned and bonded and fixed to a unit mounting portion formed in an apparatus frame. The optical head device according to claim 3,
The light source unit includes at least one spacer for adjusting a distance between a light emitting point of the first laser light source and a lens center of the aberration correction lens,
An optical head device, wherein at least one of the first laser light source and the correction lens is fixed to the holder via the spacer. The optical head device according to claim 4,
The light source unit mounted on the unit mounting portion is movable by a predetermined amount around the optical axis direction, the direction orthogonal to the optical axis, and the orthogonal axis passing through the optical axis,
An optical head device, wherein the light source unit is bonded and fixed to the unit mounting portion in a state where the position of the light source unit mounted to the unit mounting portion is adjusted three-dimensionally. The optical head device according to claim 5,
The optical head device, wherein the aberration correction lens is a toric lens.

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