JPH11339302A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical pickup device equipped with a light source unit of constitution capable of properly aligning each of elements. SOLUTION: A package main body 21 of a package 20 in a light source unit 10 of an optical pickup device is a molded work piece in which a semiconductor laser 2, a sub-mount 24, a reference surface 30 for prescribing the position of a semiconductor substrate 11 and attaching surfaces 33 and 36 of diffraction elements 13 and 14 are simultaneously formed. When each of the diffraction elements 13 and 14 is attached to the attaching surfaces, the attaching positions and the postures of the diffraction elements 13 and 14 are automatically prescribed. Also, since mutual positional relation and angular relation or the like between the reference surface 30 and the attaching surface is highly accurate, positional relation between the semiconductor laser 2a and each of the diffraction elements 13 and 14 is also accurately prescribed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup constructed so that return light from an optical recording medium is diffracted and separated by a hologram element, and the diffracted and separated light is reflected by a reflection means and guided to a photodetector. It concerns the device. More specifically, the present invention relates to an optical pickup device including a light source unit having a configuration in which optical elements such as a semiconductor laser, a hologram element, and a reflection unit are incorporated in a package.

[0002]

2. Description of the Related Art An optical pickup device used for recording / reproducing an optical disk such as a CD, DVD, MO, etc.
2. Description of the Related Art There is known a device including a light source unit having a configuration in which optical elements such as a semiconductor laser, a photodetector, and a hologram element are incorporated in a package. Such an optical pickup device is disclosed in, for example, JP-A-8-124205 and JP-A-3-278330.

In an optical pickup device disclosed in Japanese Patent Application Laid-Open No. 8-124205, a transmission-type three-segment diffraction grating, a transmission-type hologram element, a reflection means, and an objective lens are arranged in this order from a semiconductor laser toward an optical disk. ing. Further, from the optical disk to the photodetector, an objective lens, a reflection means, a transmission type hologram element, a transmission type three-segment diffraction grating, and a reflection mirror are arranged in this order.

A semiconductor laser, a transmission-type three-segment diffraction grating, a transmission-type hologram element, and a reflection means are installed on the same base, and these are integrated as a light source unit. In this light source unit, a heat sink is mounted on a base, a semiconductor laser is mounted on the upper surface, and a laser beam is emitted in a direction parallel to the substrate surface. A photodetector is formed behind the semiconductor laser on the upper surface of the heat sink, and a reflection mirror is disposed above the photodetector.

In this optical pickup device, a laser beam emitted from a semiconductor laser is split into a laser beam for signal reproduction and two laser beams for tracking error detection by a transmission type three-division grating. After being transmitted through the transmission type hologram element, each of the divided laser beams rises in a direction orthogonal to the surface of the base and is condensed on the optical disk via the objective lens.

[0006] The return light from the optical disk is
The light enters the transmission type hologram element via the reflection means. The return light is diffracted by the transmission type hologram element and diffracted in a direction perpendicular to the surface of the substrate, and at the same time, astigmatism is imparted. This diffracted light falls down by the reflection mirror and is guided to the photodetector. Signal reproduction, tracking error detection, and focus error detection are performed according to the detection result of the photodetector.

On the other hand, the optical pickup device disclosed in Japanese Patent Application Laid-Open No. 3-278330 also diffracts return light from an optical disk in a direction orthogonal to a semiconductor substrate, and diffracts the diffracted light by a special optical element (prism). It is common to that disclosed in Japanese Patent Application Laid-Open No. 8-124205 in that it is bent downward and guided to a photodetector.

[0008]

As described above, in the light source unit of the conventional optical pickup device, in the package, the return light from the optical disk is diffracted above the surface of the substrate by the transmission type hologram element, so that the rear side of the semiconductor laser is provided. In this configuration, the return light is reflected downward by the reflection mirror. However, when the return light passes above a semiconductor laser or the like, there is a possibility that the return light may interfere with the wire wiring routed there.

For example, when the objective lens moves in a direction perpendicular to the optical axis for track following, a phenomenon occurs in which a part of the return light is kicked by the movement, and the return light guided to the photodetector occurs. The amount of light itself decreases. In such a case, if a part of the return light interferes with the wire, the return light guided to the photodetector becomes very small, and the optical disk cannot be reproduced with high accuracy. In addition, the accuracy of tracking and focus control becomes insufficient.

Further, if the light component that interferes with the wire is reflected on the inner wall of the package and guided to the photodetector, the accuracy of the reproduction of the optical disk and the various controls is further deteriorated. Especially,
When the objective lens moves in the optical axis direction due to focus servo pull-in, the objective lens temporarily approaches the unit and the beam diameter of the return light increases, so that interference between the return light and the wire is likely to occur. In addition, the accuracy of reproduction and each control is apt to deteriorate.

On the other hand, the mounting position and posture of each optical element such as a semiconductor laser and a hologram element greatly affect the characteristics of the optical pickup device. For example, if the mounting position or attitude of the hologram element that separates the laser light emitted from the semiconductor laser into the signal reproduction laser light and the two tracking error detection laser lights is deviated from the target, the desired separation characteristics are obtained. Cannot be obtained, and the accuracy of reproduction and the like of the optical disc deteriorates. It is sufficient to take a sufficient time for the alignment adjustment of each optical element and to perform the adjustment with high accuracy. However, if such time is taken, the production efficiency of the optical pickup device is deteriorated. In particular, in the case of a light source unit in which each element is mounted in a package, it is difficult to adjust the alignment of each element.

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide an optical pickup device having a light source unit that does not cause return light to interfere with a wire and that can properly perform alignment of each element. It is to propose.

[0013]

In order to solve the above-mentioned problems, an optical pickup device according to the present invention comprises a light source unit,
Separation means for separating laser light emitted from the light source unit into laser light for signal reproduction and laser light for tracking error detection, and condensing the laser light for signal reproduction and the laser light for tracking error detection on an optical recording medium Focusing means, and diffracting means for diffracting return light from the optical recording medium, the light source unit is a package,
A semiconductor substrate mounted in the package; a semiconductor laser mounted on a submount in a state of emitting laser light in a direction parallel to the substrate surface of the semiconductor substrate; and a semiconductor laser formed on the substrate surface of the semiconductor substrate. The following configuration is adopted in an optical pickup device provided with a photodetector and a reflection unit that reflects the diffracted light diffracted by the diffraction unit and guides the light to the photodetector.

First, a reference surface for defining the positions of the semiconductor laser, the submount, and the semiconductor substrate, and a mounting surface of at least one of the separating means and the diffraction means are provided on the package of the light source unit. Are provided, and the package constituent member is a molded product in which the reference surface and the mounting surface are simultaneously formed.

In the optical pickup device having this configuration, the semiconductor laser, the submount, and the semiconductor substrate are installed in the light source unit by using the reference surface formed on the package component of the package of the light source unit. When the separating means and the like are mounted on the mounting surface formed on the member, their mutual positional relationship is automatically defined.
For example, the optical axis of the laser beam emitted from the semiconductor laser can be made to coincide with the optical axis of the separating means, or the optical path length of the semiconductor laser and the separating means can be set to a predetermined distance. Accordingly, it is possible to realize an optical pickup device including a light source unit capable of appropriately performing alignment of each optical element.

Further, since a package component which is a molded product in which each of the reference surface and the mounting surface is formed at the same time is employed, the mutual positional relationship and angular relationship (verticality) between the reference surface and the mounting surface are adopted. ) Is highly accurate. Therefore, the mutual positional relationship between the optical elements mounted using these surfaces can be more precisely defined.

Secondly, according to the present invention, the separating means is attached to a package, and the first surface orthogonal to the optical axis (unit emission optical axis) of the laser beam emitted from the light source unit is provided on the outer peripheral surface of the package. And a cylindrical or arc-shaped second reference surface centered on an axis extending parallel to the optical axis.

In the optical pickup device having this configuration, when the light source unit is assembled, the first reference plane is used so that the optical axis of the objective lens (condensing means) and the like are parallel to the unit emission optical axis. And the angle deviation of the optical axes can be reduced. Further, the assembling work is also facilitated. Further, if the rotation angle of the light source unit is adjusted using the second reference plane after the light source unit is assembled to the optical pickup device, a sub-beam (tracking error detection laser light) for performing tracking control by the three-beam method is used. It is possible to easily adjust the rotation angle between the disk and the track of the optical disk. After the rotation angle adjustment is completed, if the position of the light source unit is adjusted again by using the first reference plane, the displacement between the optical axis of the objective lens and the unit and the optical axis of the unit can be almost eliminated. it can. As described above, according to the present invention, it is possible to appropriately set the unit emission optical axis of the light source unit and the diffraction characteristics of the separation unit.

Third, in the present invention, a cylindrical or arcuate curved surface centered on the optical axis of the laser light emitted from the light source unit (unit emission optical axis) is used as the second reference surface. doing.

Also in the optical pickup device having this configuration, the relative angle between the sub-beam and the track can be appropriately set using the reference plane. Moreover, since the reference plane is a curved surface centered on the unit output optical axis, the unit output optical axis does not shift with the rotation angle adjustment. In addition, since the reference plane can be manufactured using the unit output optical axis as a guide, it is effective for manufacturing a reference plane with high surface accuracy.
If such a reference surface with high surface accuracy can be manufactured, the rotation adjustment of the light source unit can be performed with higher accuracy.

Fourth, in the present invention, the diffraction direction of the diffraction means is made parallel to the substrate surface of the semiconductor substrate.

In the optical pickup device having this configuration, the light diffracted by the diffracting means passes on the side of the semiconductor laser.
Therefore, the diffracted light does not interfere with the wire routed above the semiconductor laser. Therefore, it is possible to realize an optical pickup device having excellent optical characteristics and capable of accurately controlling the reproduction, tracking, and focusing of the optical recording medium.

Further, the thickness dimension of the light source unit can be reduced as compared with the case where the diffraction direction of the diffraction means is set in a direction perpendicular to the semiconductor substrate.

Here, it is desirable to adopt a configuration in which the optical path length from the semiconductor laser to the diffraction means is equal to the optical path length from the diffraction means to the photodetector. By doing so, the optical path length of the return light can be made shorter than before, so that the optical system of the optical pickup device can be made compact and the device can be downsized.

On the other hand, in the optical pickup device of the present invention, it is preferable that the focusing error detection of the focusing means is performed by using the tracking error detection laser beam. With this configuration, a diffraction unit having only a simple optical path separation function can be adopted as a diffraction unit for diffracting and separating return light from the optical recording medium. With such a diffraction means, the diffraction pattern can be made very simple. For example, a linear diffraction pattern can be used. The diffraction means provided with such a diffraction pattern is less likely to deteriorate the diffraction characteristics due to wavelength fluctuation, displacement of the mounting position of each optical element, and the like. Therefore, it is possible to realize an optical pickup device in which desired optical characteristics can be stably obtained. Also,
Since a simple diffraction pattern can be produced, the tolerance for the production error of the diffraction pattern can be increased, and the production cost of the diffraction means can be reduced.

[0026]

Embodiments of the present invention will be described below with reference to the drawings.

(Overall Configuration of Optical Pickup Device) FIG. 1 shows a schematic configuration of an optical system of the optical pickup device.
The optical pickup device 1 includes a semiconductor laser 2 and a rising mirror 1 that raises a laser beam Lf emitted from the semiconductor laser 2.
8, an objective lens (condensing means) 12 for converging the raised laser beam Lf on the optical disc 4, a signal reproducing light receiving element 3 for detecting the return light Lr from the optical disc 4, and an optical disc And a light guide system 70 for guiding the return light Lr from the light receiving element 4 to the light receiving element 3 for signal reproduction.
In addition, a first diffraction element (separation means) arranged at an intermediate position in an optical path from the semiconductor laser 2 to the rising mirror 18
13. The first diffraction element 13 is an element for splitting a laser beam emitted from the semiconductor laser 2 into a laser beam for signal reproduction and a laser beam for tracking error detection.

The light guide system 70 receives the return light L from the optical disc 4.
A second diffraction element 14 for diffracting r and a reflecting mirror 15 for guiding the light diffracted by the second diffraction element 14 to the light receiving element 3 for signal reproduction are provided.

In the optical pickup device 1 of the present embodiment, the semiconductor laser 2, the signal reproducing light receiving element 3, the light guide system 70 and the first diffraction element 13 are built in a common package 20,
The light source unit 10 is integrated.

(Configuration of Light Source Unit) FIGS. 2 and 3 show a light source unit. FIG. 2A is a plan view of the light source unit, and FIGS. 2B and 2C are FIGS.
It is sectional drawing in the AA 'line of (A), and sectional drawing in the BB' line. FIG. 3 is a front view of the light source unit as viewed from the front (the direction of arrow C in FIG. 2A). In FIG. 2A, a part of the package is omitted for easy understanding of the internal configuration of the light source unit. In the following description, the width direction of the package is described as an X direction, the vertical direction of the package is defined as a Y direction, and the front-rear direction of the package is defined as a Z direction.

As shown in these figures, the light source unit 1
The package 20 has a flat rectangular parallelepiped shape. Inside the package 20, a semiconductor substrate 11, a submount 24 mounted on a substrate surface 111 of the semiconductor substrate 11, and an upper surface of the submount 24 are provided. And a light-receiving element 3 for signal reproduction formed on the substrate surface 111 of the semiconductor substrate 11. Further, the package 20 is provided with the reflection mirror 15 and the first and second diffraction elements 13 and 14.

On the front surface 204 of the package 20, there is formed a cylindrical projection 201 which projects vertically toward the front.
A light passage hole 203 is formed by the cylindrical projection 201, and the first and second diffraction elements 13 and 14 are attached thereto. The forward laser light Lf emitted from the semiconductor laser 2 is emitted to the outside via these elements 13 and 14, and the return light Lr from the optical disc 4 is guided to the inside of the package 20.

The package 20 is composed of a substantially box-shaped package main body 21 having an upper opening, and a package lid plate 22 closing the upper opening. The package body 21 and the package cover plate 22 define a chamber 202 in which the semiconductor substrate 11 and the submount 24 are mounted, and also form a cylindrical projection 201.

FIG. 4A is a plan view of the package body, and FIGS. 4B and 4C are D-D in FIG. 4A, respectively.
It is sectional drawing in the D 'line, and sectional drawing in the EE' line. As shown in these figures, the package body 21
Has a substantially rectangular bottom wall 211, a front wall 212, a rear wall 213, and left and right side walls 214 and 215 rising from four sides of the bottom wall 211. Front wall 21
2 is cut in a concave shape, and a pair of left and right protruding side walls 216 and 217 extend perpendicularly to the front wall 212 from both sides thereof. The lower ends of these protruding side walls 216, 217 are connected by a protruding bottom wall 218 extending forward from the bottom wall 211. The protruding side walls 216 and 217 and the protruding bottom wall 218 form an extension 219 protruding forward.

The width of the extension 219 is smaller than the width of the package body 21, and the extension 219 is
1 is formed at a position offset from the center in the width direction.

The surface of the bottom wall 211 of the package body 21 is flat, and the semiconductor laser 2 and the submount 24
And reference plane 3 for defining the position of semiconductor substrate 11
It is set to 0. A rectangular plate-shaped stage 231 of the lead frame 23 is fixed to the reference surface 30. The leads (12 leads in this example) 232 of the lead frame 23 have pad portions located on the reference surface 30, and portions serving as external connection terminals pass through the rear wall 213 of the package body 21. Extending to the outside.
These external connection terminal portions are arranged at regular intervals in the width direction of the package.

(Configuration of Semiconductor Substrate and Its Peripheral Part)
FIG. 5 is an enlarged perspective view showing a semiconductor substrate and its peripheral portion, and FIG. 6 is a plan view showing a substrate surface of the semiconductor substrate. As shown in FIGS. 2, 5, and 6, the semiconductor substrate 11 is bonded to the stage 231 of the lead frame 23 with a silver paste. Semiconductor substrate 11
On one side of the substrate surface 111 in the width direction,
A substantially rectangular electrode portion 111a long in the front-rear direction is formed, and a signal processing circuit 26 is formed on the other side.
The submount 24 is fixed on the electrode portion 111a with a silver paste. The submount 24 is formed of a semiconductor substrate having a certain thickness, and the semiconductor laser 2 is fixed on the upper surface thereof with a silver paste.

The semiconductor laser 2 has a front emission end face 2f from which the front laser light Lf is emitted, and a rear emission end face 2b from which the rear laser light Lb is emitted. From these emission end surfaces 2f and 2b, the substrate surface 111 of the semiconductor substrate 11 is formed.
The laser beams Lf and Lb are emitted forward and backward, respectively, in a direction parallel to. The emission point of the forward laser light Lf of the semiconductor laser 2 is located at substantially the center in the vertical direction of the package 20 on the front emission end face 2f. The forward laser light Lf emitted from this point is attached to the light passage hole 203. First and second diffraction elements 13 and 14
And is emitted to the outside.

On the substrate surface 111 of the semiconductor substrate 11,
Signal processing circuit 2 formed on the side of electrode section 111a
Reference numeral 6 increases the level of the output signal of the light-receiving element 3 for signal reproduction, and generates a pit signal (RF signal), a tracking error signal (TE signal), and a focus error signal (FE signal) by an external control device. This is a circuit to make it easier. The signal reproducing light receiving element 3 is formed in front of the signal processing circuit 26. Therefore, the signal reproducing light receiving element 3
Is formed at a position in front of the front emission end face 2f of the semiconductor laser 2 and at a position laterally deviated from the optical axis Lu of the front laser beam Lf.

A monitor light receiving element 2 for feedback controlling the laser light output of the semiconductor laser 2 is provided at a position behind the semiconductor laser 2 on the upper surface of the submount 24.
5 are formed. Back emission end face 2 of semiconductor laser 2
A part of the rear laser beam Lb emitted from b is directly incident on the monitoring light receiving element 25.

(Structure of the light-receiving element for signal reproduction) FIG. 7 shows the light-receiving element 3 for signal reproduction in an enlarged manner. As shown in this figure, the light-receiving element 3 for signal reproduction has seven light-receiving surfaces A, B1, B2, C, D1, and elongated in the width direction (X direction).
D2 and E are provided. The light receiving surface A is for detecting a pit signal (RF signal), and the remaining light receiving surfaces are a tracking error signal (TE signal) and a focus error signal (FE signal).
It is for detection. In the light-receiving element 3 for signal reproduction, the remaining light-receiving surfaces are arranged three by three in the front-rear direction with the light-receiving surface A as a center. In front of the light receiving surface A, a light receiving surface B1, a light receiving surface C, and a light receiving surface B2 are arranged in this order.
, A light receiving surface D1, a light receiving surface E and a light receiving surface D2 are arranged in this order. The amounts of light received on these light receiving surfaces are converted into electric signals and supplied to the signal processing circuit 26. The method of generating the tracking error signal (TE signal) and the focus error signal (FE signal) will be described later.

The signal processing circuit 26 amplifies the electric signal supplied from each light receiving surface and converts the signal into a voltage corresponding to the amount of received light, and appropriately calculates a signal obtained by the I / V amplifier. It is composed of an arithmetic circuit section and the like. The output of the signal processing circuit 26 is applied to the substrate surface 11 of the semiconductor substrate 11.
Each of the electrodes 111b is taken out from each electrode 111b.

Each electrode 111b is electrically connected to a predetermined lead pad of the lead frame 23 by wire bonding (see FIG. 2). Further, electrodes (not shown) formed on the semiconductor laser 2 and the submount 24 are also electrically connected to pad portions of predetermined leads 232 by wire bonding. Each electrode 1
An output signal from the semiconductor laser 2b is guided to a control device (not shown) disposed outside the light source unit 10 via the lead frame 23 to generate an RF signal, a TE signal, and an FE signal. The feedback control of the laser light output is performed.

(Attaching Structure of Each Optical Element) Referring to FIG. 2, in the light source unit 10, the reflecting mirror 15, the first diffractive element 13, and the second diffractive element are located at predetermined positions of the package 20. Element 14 is mounted. A mirror mounting portion 221 of the reflection mirror 15 is formed integrally with the package cover plate 22. The mirror mounting portion 221 is a protrusion having a trapezoidal cross section formed from almost directly above the light receiving element 3 for signal reproduction toward the rear. The front surface of the trapezoidal mirror mounting portion 221 is a mirror mounting surface 222 inclined forward by 45 degrees, and the reflection mirror 15 is fixed to the mirror mounting surface 222 by an adhesive or the like.

The return light Lr from the optical disk 4 which enters the package via the first and second diffraction elements 13 and 14 hits the reflection mirror 15 and falls down at a right angle by this mirror 15 to receive the signal for the signal reproduction. Irradiate 3.

The first diffraction element 13 and the second diffraction element 14 are both rectangular in shape, and
Attached to.

FIG. 8 schematically shows a structure for mounting the first diffraction element 13, and FIG. 9 schematically shows a structure for mounting the second diffraction element 14. As shown in FIGS. 4 and 8, on the reference surface 30 of the frame main body 21, a step surface 31 which is one step lower than the reference surface 30 is formed at the boundary with the extending portion 216. The step surface 31 is formed along the width direction, and has a constant length in the front-rear direction. At the boundary between the step surface 31 and the reference surface 30, a step surface 3
A step surface 32 orthogonal to 1 is formed, and a step surface (attachment surface) 33 orthogonal to the step surface 31 is formed at a boundary between the step surface 31 and the extending portion 216.

Therefore, the first diffraction element 13 is connected to the step surface 33.
When it is arranged so as to be in contact with, the arrangement position in the front-back direction is automatically defined. Further, the attitude of the first diffraction element 13 is automatically defined so that the optical axis of the first diffraction element 13 is substantially parallel to the optical axis Lu of the forward laser beam Lf. The first diffraction element 13 is fixed by an adhesive or the like after fine adjustment of the arrangement position in the width direction in this state.

As shown in FIGS. 3, 4 and 9, the front surface 35 of the extension 216 is a vertical surface. The second diffraction element 14 has a slightly larger dimension than the light exit 201. Therefore, when the second diffraction element 14 is disposed so as to be in contact with an edge portion (mounting surface) 36 which defines a part of the opening of the light passage hole 203 of the package 20 on the front surface 35, the arrangement in the front-rear direction is provided. The position is defined automatically. Further, the optical axis of the second diffraction element 14 is
Laser light Lf emitted from semiconductor laser 2 from semiconductor laser 2
The attitude of the second diffraction element 14 is automatically defined so as to be substantially parallel to the optical axis Lu. The second diffraction element 14 is fixed by an adhesive or the like after finely adjusting the arrangement position of the package 20 in the width direction in this state.

As described above, in this example, when the first and second diffraction elements 13 and 14 are mounted, the respective diffraction surfaces 13 and 14 are utilized by using the mounting surfaces 33 and 36 formed on the package body 21. In the direction parallel to the optical axis Lu of the front laser beam Lf (front-back direction) can be defined easily and accurately. Further, the optical axes of the diffraction elements 13 and 14 can be set substantially parallel to the optical axis Lu. Accordingly, the diffraction characteristics of each of the diffraction elements 13 and 14 can be set appropriately.

Here, the frame main body 21, which is a component of the package 20, is a molded product in which the reference surface 30, and the mounting surfaces 33, 36 are simultaneously molded. Therefore, the reference plane 3
The positional relationship and the angular relationship between 0 and each of the mounting surfaces 33 and 36 are highly accurate. Therefore, the relative positional relationship between the optical elements (such as the semiconductor laser 2 and the respective diffraction elements 13 and 14) provided on these surfaces can be accurately defined.

(Outer Shape of Package) As shown in FIG. 3, in the package body 21, the outer side surfaces of the protruding side walls 216 and 217 of the extending portion 219 are provided with the forward laser beam Lf emitted from the light passage hole 203. 4 centered on the optical axis Lu
Arc surfaces 40a, 40b, 40c, and 40d are formed. These arc surfaces 40a to 40d are formed at the corners of the protruding side walls 216 and 217, respectively, and have the same central angle. In addition, these arc surfaces 40a to 40d
Of these, the two arc surfaces 40a and 40c are line-symmetric with respect to the optical axis Lu, and the remaining two arc surfaces 40b and 40d also have the optical axis L
u is line symmetric. The front surfaces 41a and 41b of the front wall 212 of the package body 21 are flat reference surfaces orthogonal to the optical axis Lu.

Accordingly, when the light source unit 10 is mounted on the optical pickup device 1, if the reference surfaces 41a and 41b are used, the optical axis of the objective lens 12 and the like and the forward laser light L
The orientation of the light source unit 10 can be set so that the optical axis Lu of f coincides with the optical axis Lu. Further, if the reference surfaces 41a and 41b are used, the light source unit 10 can be easily attached to the optical pickup device 1. On the other hand, by adjusting the rotation angle of the light source unit 10 using the arc surfaces 40a to 40d, the sub-beam (tracking error detection laser beam) for performing tracking by the three-beam method and the rotation angle adjustment of the track of the optical disk 4 are adjusted. Can be easily performed. That is, the diffraction direction in the first diffraction element 13 can be set appropriately. Thus, the light source unit 10
Since the optical axis Lu of the forward laser beam Lf and the diffraction characteristic (diffraction direction) of the first diffraction element 13 can be appropriately set,
An optical pickup device having excellent optical characteristics can be realized.
Further, since the arc surfaces 40a to 40d centering on the optical axis Lu may be produced, it is easy to produce an arc surface symmetrical with respect to the optical axis Lu, and it is possible to improve the surface accuracy of the arc surface. Further, since the arc surfaces 40a to 40d are curved surfaces centered on the optical axis Lu, even when the rotation angle of the light source unit 10 is adjusted with reference to the arc surfaces 40a to 40d, the position of the unit output optical axis Lu is adjusted. Does not change.

The projecting side walls 216, 2
Instead of forming the arc surface only at the corner portion 17, the entire outer peripheral surface of the side walls 216 and 217 may be an arc surface. When the package 20 is not a flat type, the outer shape of the wall defining the light passage hole 203 of the package 20 may have a circular cross section in the XY plane.

Further, an arc surface (second reference surface) centered on an axis parallel to the optical axis Lu may be formed. in this case,
When the rotation angle of the light source unit 10 is adjusted, the unit output optical axis Lu and the optical axis of the objective lens 12 and the like are shifted, but after the rotation angle adjustment is completed, the first reference surface 41
The deviation of the optical axis can be corrected by using a and 41b.

(Basic operation of optical pickup device)
The basic operation of the optical pickup device will be described with reference to FIG. In the light source unit 10, the forward laser light Lf emitted from the semiconductor laser 2 enters the first diffraction element 13 almost perpendicularly. The first diffraction element 13 has a diffraction grating surface (not shown). This diffraction grating surface has a function of dividing the forward laser light Lf that has entered substantially perpendicularly into a main beam and two sub beams.
In addition, the optical disc 4 has a function of converting the wavefronts of the two sub beams so that the two sub beams focus on the optical disc 4 before and after the optical axis. This diffraction grating surface
The return light Lr from the optical disc 4 is again transmitted to the first diffraction element 1
3 is formed at a position where it does not pass through the diffraction grating surface again.

For this reason, the forward laser beam Lf is split by the diffraction element 13 into a main beam and two sub beams. Of these beams, the main beam is used as laser light for signal reproduction (laser light for signal reproduction), and the two sub-beams are used as laser light for tracking error detection (laser light for tracking error detection).

The laser beam for signal reproduction and the two laser beams for tracking error detection reach the second diffraction element 14. The second diffraction element 14 determines the zero-order diffraction efficiency in the optical path where the three laser beams reach the optical disc 4,
Is set so that the product of the first order diffraction efficiency and the first-order diffraction efficiency in the optical path from the light-receiving element 3 to the signal reproducing light-receiving element 3 is maximized. The diffraction grating surface formed on the second diffraction element 14 is substantially parallel to the diffraction grating surface of the first diffraction element 13.

Of the three laser beams, the second diffraction element 1
The light component (0th-order diffracted light) transmitted through the light source unit 10
Emitted from Then, after being bent at a right angle by the rising mirror 11, the optical disk 4 is bent by the objective lens 12.
Focus on the recording surface of. At this time, the laser beam for signal reproduction focuses on the recording surface, and the two laser beams for tracking error detection enter a front focus state and a rear focus state.

The three laser beams converged on the recording surface of the optical disk 4 are reflected there and become return light Lr traveling from the optical disk 4 to the light receiving element 3 for signal reproduction. These return lights Lr are again transmitted to the objective lens 12 and the rising mirror 1.
The light is incident on the second diffraction element 14 of the light source unit 10 through the light source 8.

Here, the second diffraction element 14 has only a function of diffracting each return light in a direction parallel to the substrate surface 111 of the semiconductor substrate 11, in this example, in the width direction of the package 20. There is no function of performing wavefront conversion such as convergence and divergence on each return light Lr. For this reason, the three return lights Lr incident on the second diffraction element 14 are diffracted by the diffraction action of the diffraction element 14 to change the traveling direction.

The light diffracted by the second diffraction element 14 is the first light
Incident on the diffraction grating 13. As described above, the diffraction grating surface of the first diffraction grating 13 is not formed in a range where these diffracted lights enter. For this reason, each diffracted light incident on the diffraction grating 13 passes through the first diffraction grating 13 and reaches the reflection mirror 15. These diffracted lights fall vertically by the reflecting mirror 15 and irradiate the respective light receiving surfaces of the signal reproducing light receiving element 3.

As shown in FIG. 7, the diffracted light of the return light of the signal reproducing laser light forms light spots s1 and s2 on the light receiving surface A. Further, the diffracted light of the return light of the laser light for tracking error detection forms light spots s3 and s4 on the light receiving surfaces B1, B2 and C. The diffracted light of the return light of the other laser light for tracking error detection forms light spots s5 and s6 on the light receiving surfaces D1, D2 and E.

In this example, the RF signal is detected based on the amount of light received on the light receiving surface A of the signal reproducing light receiving element 3. The TE signal is detected by calculating the difference between the sum S1 of the light reception amounts of the light receiving surfaces B1, B2, and C and the sum S2 of the light reception amounts of the light receiving surfaces D1, D2, and E. The FE signals are received on the light receiving surfaces B1, B2, E
Is obtained by calculating the difference between the sum S3 of the received light amounts of the light receiving surfaces and the sum S4 of the received light amounts of the light receiving surfaces D1, D2, and C. In addition,
These signals are transmitted to the lead frame 23 of the light source unit 10.
Is generated by a control device (not shown) electrically connected to the external connection terminal of.

A part of the rear laser light Lb emitted from the rear emission end face 2 b of the semiconductor laser 2 directly enters the monitoring light receiving element 25 formed on the upper surface of the submount 24. Feedback control of the laser light output of the semiconductor laser 2 is performed based on the output signal of the monitoring light receiving element 25. The feedback control is also performed by the above-described control device.

As described above, in the optical pickup device 1 of the present embodiment, the diffraction direction of the second diffraction element 14 is set to the width direction of the package 20. For this reason, the second diffraction element 1
The light diffracted by 4 can be prevented from interfering with the wires connecting the electrodes 111b of the semiconductor substrate 11 and the pad portions of the leads 232 of the lead frame 23. Therefore, reproduction, tracking and focusing control of the optical disk 4 can be performed with high accuracy. Further, the thickness dimension of the light source unit 10 can be made smaller than when the diffraction direction of the second diffraction element 14 is set in the vertical direction of the package 20.

Here, in the optical pickup device 1 of the present embodiment, the second diffraction element 14 has a function of diffracting the return light from the optical disk 4, but does not have a function of wavefront conversion. For this reason, the second diffraction element 14
And the optical path length from the second diffraction element 14 to the light receiving element 3 for signal reproduction is equal. As a result, the optical path length of the return light can be made shorter than before, and the optical system of the optical pickup device can be made compact. As a result,
The size of the device can be reduced.

More specifically, since the second diffractive element 14 has a function of diffracting the return light and does not have a function of transforming the wavefront, the convergence point of the light diffracted by the diffractive element 14 is
It is optically conjugate with the virtual light emitting point of the semiconductor laser 2 and the two tracking error detection laser beams divided and generated by the first diffraction element 13. Therefore, the following relationship is established between the emission point of the forward laser light Lf of the semiconductor laser 2 and the center of the signal reproducing light receiving element 3.

As shown in FIGS. 10 and 11, the thickness of the submount 24, the submount 24 and the semiconductor laser 2
From the surface in contact with the light emitting point O, the optical path separation angle at the second diffraction element 14 at the wavelength of the semiconductor laser 2, and the unit output from the semiconductor laser 2 to the diffraction grating plane of the second diffraction element 14. The optical distance along the emission axis Lu is
These are ts, hLD, θbs, and dbs, respectively. With this definition, the XZ coordinate of the center of the signal reproducing light-receiving element 3 when the light-emitting point O in the (X, Z) plane where the signal reproducing light-receiving element 3 is formed is defined as Equation (1). And (2).

X = dbs × sin (θbs) (1) Z = dbs × {1−cos (θbs)} + ts + hLD (2) The diffraction of the semiconductor laser 2 and the second diffraction element 14 As can be seen from FIG. 10, the optical distance to the grating plane along the unit emission optical axis Lu is a position slightly shifted from the light incident surface of the second diffractive element 14 to the semiconductor laser 2 side. Corresponding to the distance between FIG.
11 and FIG. 11, the reflection angle of the reflection mirror 15 is 4
The case where the angle is set to 5 degrees is shown, and the deviation of the reflection angle of the mirror 15 and the angle deviation around the optical axis are not considered.

In the optical pickup device 1 of this embodiment, the focus error signal of the objective lens 12 is generated by using the tracking error detecting laser light, and the second diffraction element 14 that diffracts and separates the return light from the optical disk 4. The one having only a simple optical path separation function is adopted. For this reason,
The diffraction pattern of the diffraction element 14 can be simplified. For example,
A linear diffraction pattern can be employed. A diffraction element having such a diffraction pattern has little deterioration in diffraction characteristics due to wavelength fluctuation, displacement of the mounting position of each optical element, and the like. Therefore, the target optical characteristics can be stably obtained. In addition, since a simple diffraction pattern may be manufactured, the manufacturing error tolerance of the diffraction pattern can be increased, and the manufacturing cost of the diffraction element can be reduced.

(Other Embodiments) Although the optical pickup device 1 uses the first and second diffractive elements 13 and 14 which are independent from each other, the first diffractive element 13 is provided on one surface. Of course, a single optical element having optical characteristics and having the optical characteristics of the second diffraction element on the other surface may be employed.

The submount 24 is mounted on the semiconductor substrate 11.
The submount 24 may be mounted on the stage 231 or the lead 232 of the lead frame 23.

Further, the optical system of the optical pickup device 1 includes not only the optical element shown in FIG. 1 but also a lens for converting the laser beam Lf into a parallel beam, and a beam diameter in two orthogonal directions of the laser beam. A beam shaping prism for aligning, a compound prism for matching the optical axis of the laser light emitted from another light source with the optical axis of the light source unit 10, an aperture limiting means for reading information from an optical disk of different specifications, and a wavelength. An optical element such as a selective optical element may be included.

[0075]

As described above, in the optical pickup device of the present invention, the package of the light source unit in which the semiconductor laser and the photodetector are incorporated defines the positions of the semiconductor laser, the submount, and the semiconductor substrate. And a package component, which is a molded product in which a reference surface for mounting and a mounting surface for diffractive means and the like are formed at the same time. Therefore, it is possible to accurately define a relative positional relationship between a component such as a semiconductor laser installed using the reference surface and a component such as diffraction means mounted on the mounting surface.

In the optical pickup device of the present invention,
A separation unit is attached to the package, and a first reference plane orthogonal to the optical axis of the laser light emitted from the light source unit is formed on the outer peripheral surface of the package, and a cylindrical or arc-shaped centered on an axis extending parallel to the optical axis. A second reference plane is provided. With this configuration, it is possible to accurately set the emission optical axis of the light source unit and the separation direction of the separation unit using the first and second reference surfaces.

Further, in the optical pickup device of the present invention, the separating means is attached to the package, and the outer peripheral surface of the package is provided with a cylindrical shape having the optical axis of the laser beam emitted from the light source unit (unit emitting optical axis) as a center. An arc-shaped reference plane is formed. If you do this,
The diffraction direction of the separation means can be appropriately set using the reference plane. In addition, since the reference plane having the unit output optical axis as the center is provided, the rotation adjustment of the light source unit can be performed more accurately.

Further, in the optical pickup device of the present invention, the diffraction direction of the diffraction means is set to a direction parallel to the substrate surface of the semiconductor substrate. If you do this,
The light diffracted by the diffracting means can be prevented from interfering with the wire, and the reproduction, tracking, and focusing control of the optical recording medium can be accurately performed. Further, the size of the light source unit in the thickness direction of the semiconductor substrate can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an optical system of an optical pickup device to which the present invention has been applied.

2A is a schematic configuration diagram of a light source unit, FIG. 2B is a cross-sectional view taken along line AA ′ of FIG. 2A, and FIG. 2C is a cross-sectional view taken along line BB ′ of FIG. .

FIG. 3 is a front view of the light source unit shown in FIG.

FIG. 4A is a plan view of a package body which is a component of the package of the light source unit, and FIG.
FIG. 3C is a cross-sectional view taken along line D ′, and FIG.

FIG. 5 is an enlarged perspective view showing a semiconductor substrate and its peripheral portion in a light source unit of the optical pickup device.

FIG. 6 is an enlarged plan view showing a substrate surface of a semiconductor substrate in the light source unit of the optical pickup device.

FIG. 7 is an enlarged plan view showing a light-receiving element for signal reproduction in a light source unit of the optical pickup device.

FIG. 8 is a diagram for explaining a mounting structure of a first diffraction element in a light source unit of the optical pickup device.

FIG. 9 is a diagram for explaining a mounting structure of a second diffraction element in the light source unit of the optical pickup device.

FIG. 10 is a diagram for explaining a formation position in a width direction of a package of a signal reproducing light receiving element in a light source unit of the optical pickup device.

FIG. 11 is a view for explaining the formation position of the light receiving element for signal reproduction in the light source unit of the optical pickup device in the front-rear direction of the package.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 optical pickup device 2 semiconductor laser 3 signal reproducing light receiving element 4 optical disk 10 light source unit 12 objective lens 13 first diffractive element 14 second diffractive element 15 reflecting mirror 20 package 21 package body 22 package cover plate 24 submount 25 monitor Light receiving element for reference 30 Reference surface 33 Step surface (mounting surface) 36 Edge portion (mounting surface) 40a, 40b, 40c, 40d Arc surface (second reference surface) 41a, 41b Reference surface (first reference surface)

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hisahiro Ishihara 5329 Shimosuwa-cho, Suwa-gun, Nagano Prefecture Sankyo Seiki Seisakusho Co., Ltd.

Claims (7)

[Claims] 1. A light source unit, separating means for separating a laser beam emitted from the light source unit into a signal reproducing laser beam and a tracking error detecting laser beam, and the signal reproducing laser beam and the tracking error detecting laser beam The light source unit includes: a package; and a semiconductor substrate installed in the package. The light source unit includes a package, and a semiconductor substrate installed in the package. A semiconductor laser mounted on a submount so as to emit laser light in a direction parallel to the substrate surface of the semiconductor substrate; a photodetector formed on the substrate surface of the semiconductor substrate; Reflecting means for reflecting the diffracted light diffracted by the above and guiding the diffracted light to the photodetector, wherein the package of the light source unit is A package component provided with a reference surface for defining the positions of the semiconductor laser, the submount, and the semiconductor substrate; and a mounting surface for at least one of the separation unit and the diffraction unit. The optical pickup device is a molded product in which the reference surface and the mounting surface are simultaneously molded. 2. A light source unit; separating means for separating laser light emitted from the light source unit into laser light for signal reproduction and laser light for tracking error detection; A light source unit that condenses the laser light on an optical recording medium; and a diffractive unit that diffracts the return light from the optical recording medium. A semiconductor laser mounted on a submount so as to emit laser light in a direction parallel to the substrate surface of the semiconductor substrate; a photodetector formed on the substrate surface of the semiconductor substrate; Reflecting means for reflecting the diffracted light diffracted by the light guide and guiding the diffracted light to the photodetector, wherein the separating means is mounted on the package. Vignetting and,
An outer peripheral surface of the package has a first reference plane orthogonal to an optical axis of laser light emitted from the light source unit, and a second cylindrical or arc-shaped second axis centered on an axis extending parallel to the optical axis. An optical pickup device comprising a reference surface. 3. A light source unit, separating means for separating a laser beam emitted from the light source unit into a signal reproducing laser beam and a tracking error detecting laser beam, and the signal reproducing laser beam and the tracking error detecting laser beam. The light source unit includes: a package; and a semiconductor substrate installed in the package. The light source unit includes a package, and a semiconductor substrate installed in the package. A semiconductor laser mounted on a submount so as to emit laser light in a direction parallel to the substrate surface of the semiconductor substrate; a photodetector formed on the substrate surface of the semiconductor substrate; Reflecting means for reflecting the diffracted light diffracted by the light guide and guiding the diffracted light to the photodetector, wherein the separating means is mounted on the package. Vignetting and,
An optical pickup device, wherein an outer peripheral surface of the package includes a cylindrical or arc-shaped reference surface centered on an optical axis of laser light emitted from the light source unit. 4. A light source unit; separating means for separating laser light emitted from the light source unit into laser light for signal reproduction and laser light for tracking error detection; The light source unit includes: a package; and a semiconductor substrate installed in the package. The light source unit includes a package, and a semiconductor substrate installed in the package. A semiconductor laser mounted on a submount so as to emit laser light in a direction parallel to the substrate surface of the semiconductor substrate; a photodetector formed on the substrate surface of the semiconductor substrate; And a reflecting means for reflecting the diffracted light diffracted by the step (c) and guiding the diffracted light to the photodetector. An optical pickup device which is a direction parallel to the substrate surface of the plate. 5. An optical pickup device according to claim 4, wherein an optical path length from said semiconductor laser to said diffraction means is equal to an optical path length from said diffraction means to said photodetector. 6. The method according to claim 1, wherein
An optical pickup device configured to detect a focus error of the focusing means using the tracking error detection laser light. 7. A light source unit for an optical pickup device according to claim 1.