JPH09320091A - Optical pickup module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize reduction of the number of parts, reduction in size and cost through introduction of an integrated structure of an optical pickup module. SOLUTION: At almost the center of a holder member 100, a lens hole 101 to which an objective lens 110 is engaged is provided and a laser element mounting means 102 to which a laser element 111 is fixed is also provided at one end of the holder member 100. Moreover, a beam splitter 113 is fixed to the objective lens 110 in the side opposed to an information recording medium. A light receiving element 114 is fixed to the position on the plate surface so that the laser beam emitted from the beam splitter 113 irradiates the holder member 100. The reflected beam from the objective lens 110 is reflected within the beam splitter 113 for several times to become the predetermined optical path length and is then received by the light receiving element 114. Therefore, the optical pickup module is integrally structured to reduce the number of parts and realize reduction in size and cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compact optical pickup module by integrally providing a holder member with an objective lens, a laser element and the like.

[0002]

2. Description of the Related Art Conventionally, in an optical pickup device,
The information recording medium is irradiated with laser light emitted from an optical pickup module used in the pickup device to write and reproduce information.

FIG. 6 shows the appearance of such an optical pickup module. The optical pickup module is largely composed of a semiconductor laser 11, an objective lens 15, an optical system having a light receiving element and the like, and a drive control system having an actuator 20 and the like. Be separated. FIG. 7 shows a schematic configuration of the optical system.

The optical system in the optical pickup module includes a semiconductor laser 11 which emits a laser beam, and a beam splitter 12 which reflects the laser beam emitted from the semiconductor laser 11 and transmits the laser beam incident from an objective lens 15 described later. , A coupling lens 13 for converting the laser light into parallel light, a deflection prism 14 for deflecting the laser light, an objective lens 15 for condensing the laser light, a detection lens 16 including a cylindrical lens, and a reflection from the recording layer. It has a light receiving element 17 and the like for receiving laser light.

Under the above structure, the laser light emitted from the semiconductor laser 11 is a beam splitter 1
The light is reflected by the second reflecting surface, enters the coupling lens 13, and is converted into parallel light by the coupling lens 13. The laser light thus converted into parallel light is deflected by the deflection prism 14 and enters the objective lens 15. The laser light is condensed by the objective lens 15 to form a laser spot on the recording layer of the information recording medium (not shown).

On the other hand, laser light reflected by the recording layer (hereinafter,
Such laser light is referred to as reflected light) is the objective lens 1
The light is condensed by the beam splitter 5, passes through the deflection prism 14, the coupling lens 13, and the beam splitter 12, and enters the detection lens 16. The detection lens 16 is formed of a cylindrical lens or the like, and causes the incident reflected light to undergo astigmatism and then enters the light receiving element 17. The light receiving element 17 converts the received reflected light into an electric signal.

The photoelectric conversion signal from the light receiving element 17 is used as a reproduction signal and an actuator control signal.

Based on the actuator control signal, the actuator 20 moves the objective lens 15 to the surface of the recording layer so that the laser light focused by the objective lens 15 focuses on the recording layer (to form a fine spot). The focus drive is performed by vertically moving (in the direction indicated by Fo in FIG. 7) to adjust the position. Further, the objective lens 15 is moved parallel to the surface of the recording layer (in the direction indicated by Tr in FIG. 7) so that the focused laser spot is located at the center of a predetermined groove provided in the recording layer. Tracking drive for position adjustment is performed.

The reflected light that has entered the beam splitter 12 through the coupling lens 13 passes through the beam splitter 12, and at that time, the beam splitter 1
When the reflecting surface of 2 is provided with a half mirror coat, only a part of the incident light is transmitted, and a 1/4 λ plate is arranged between the objective lens 15 and the beam splitter 12 to reflect the beam from the beam splitter 12. When the surface is provided with a polarization coat for an optical isolator, all reflected light is transmitted.

Normally, the semiconductor laser 11 is of a can type as shown in FIG.
The size of 2 is 1 mm or less. 8A is a perspective view of the can-type semiconductor laser 11, FIG. 8B is a sectional structure of the semiconductor laser 11, and FIG. 8C is a laser device 42.
It shows the laser light emitted from.

Since the laser element 42 is accompanied by heat generation due to laser oscillation, it is fixed to the stem 41 or an element base 47 protruding from the stem 41 in order to radiate the heat.
The power supply terminal and the like are wire-bonded to the lead terminal by the gold wire 48.

Then, these are covered with a can 43 and are housed and hermetically sealed. The top surface of the can 43 is a window 44 made of glass.
Is provided so that the laser light can be extracted to the outside.

The laser element 42 is shown in FIG.
As shown in (c), the laser light emitted in two directions and emitted in the direction of the window 44 is guided to the optical system, and the laser light emitted on the opposite side to the laser light is provided in the semiconductor laser 11. Then, the light amount of the laser beam is detected and the laser power can be controlled based on the detection result.

Next, a focus detection method using the astigmatism method will be described with reference to FIG. Although the focal length of the objective lens 15 is constant, for some reason (for example,
The distance between the objective lens 15 and the recording layer may change (warpage of the information recording medium, etc.).

In such a case, the diameter of the laser spot formed on the recording layer becomes large, the laser power density becomes small, and accurate information recording cannot be performed. Also, since the reading area increases, unnecessary information becomes a detection signal. Since it is included, problems such as instability of the reproduced signal occur.

Therefore, it is necessary to adjust the distance between the objective lens 15 and the recording layer to the focal length. At this time, it is important to judge in which direction the objective lens 15 should be moved and adjusted.
This determination is made based on the spot shape formed on the light receiving element 17.

Incidentally, the light receiving element 17 is divided into four, and the reflected light incident on each region is independently photoelectrically converted and output. In this description, as shown in FIGS. 9B, 9C, and 9D, for convenience, the upper left region is the element a, the upper right region is the element b, the lower right region is the element c, and the lower left region is the element. It describes as d.

In such a case, when the distance between the objective lens 15 and the recording layer is the focal length, the reflected light from the recording layer is reflected by the detection lens 16 at the position where the light receiving element 17 is provided ( (Origin) and FIG.
As shown in (c), a circular spot is formed on the light receiving element 17.

On the other hand, when the distance between the objective lens 15 and the recording layer is longer than the focal length, the reflected light reflected from the recording layer is detected by the detection lens 16 from the position (origin) where the light receiving element 17 is provided. 9 is focused on the side (+ side in FIG. 9A) and the light receiving element 17 has
As shown in (b), the major axis direction is an ellipse inclined by 45 degrees.

Further, when the distance between the objective lens 15 and the recording layer is shorter than the focal length, the reflected light reflected from the recording layer exceeds the position (origin) where the light receiving element 17 is provided by the detection lens 16. (-Side in FIG. 9A)
In addition, the light receiving element 17 has an ellipse whose major axis is tilted by −45 degrees as shown in FIG. 9D.

Therefore, by comparing the sum of the signal intensities of the elements a and c of the light receiving element 17 divided into four and the sum of the signal intensities of the elements b and d, the objective lens 1
It is possible to know whether or not the distance between the recording layer 5 and the recording layer is larger than the focal length, and a focus control signal can be obtained from the magnitude relationship and the magnitude thereof.

Next, the tracking control signal will be described. Usually, a spiral groove is formed on the information recording medium, and unless the laser spot focused by the objective lens 15 is irradiated to the correct position, the laser power required for recording is insufficient or the recorded mark is When the mark is reproduced, a signal of a predetermined size cannot be obtained and reproduction information becomes unstable.

Therefore, in order to adjust the position of the laser spot to an appropriate position, the tracking control by the push-pull method is carried out by irradiating the groove with laser light and detecting the reflected light by at least a two-divided element. The tracking control is performed by detecting the tracking signal based on the principle.

The principle of detecting the tracking signal will be described with reference to FIG. FIG. 10A shows reflected light when the laser light focused by the objective lens 15 is applied to the groove. The laser light is diffracted by the edge portion of the groove to generate reflected light composed of multi-order diffracted light, and the main diffracted light incident on the objective lens 15 is the zero-order diffracted light.

At this time, the diffracted light that has passed through the objective lens 15 has an intensity distribution that reflects the existence of edges. Therefore,
Appropriateness of the irradiation position of the laser spot can be determined by receiving the diffracted light by the split light receiving element 17 as shown in FIG. 10B and determining the symmetry of the intensity distribution.

That is, when the difference signal TE between the sum of the signals from the elements a and d and the sum of the signals from the elements b and c is zero, the laser spot is applied to the center of the groove. When the difference signal TE is not zero, it can be seen that the laser spot is irradiated at a position deviated from the center of the groove. The direction of the deviation can be determined from the positive and negative signs of the difference signal TE.

The difference signal TE is a tracking signal, and the laser spot position is adjusted by moving the objective lens 15 parallel to the surface of the recording layer based on the tracking signal.

[0028]

However, the optical pickup module having the above-mentioned structure has a drawback that it is difficult to make it compact because the optical path of the optical system is linear. In order to overcome such a problem, JP-A-4-61
Japanese Patent Laid-Open No. 635 and Japanese Patent Laid-Open No. 4-139628 disclose a technique of mounting a semiconductor laser and a deflecting unit for an objective lens on a silicon substrate. Such a technique three-dimensionally processes silicon. There is a problem that it becomes expensive because it is necessary.

Therefore, according to the present invention, the optical pickup module is configured integrally to reduce the number of constituent parts, and the optical path is bent by using reflection or the like to enable miniaturization and cost reduction. The purpose is to provide.

[0030]

In order to solve the above problems, the invention according to claim 1 is an objective for condensing a laser beam emitted from a laser element to form a laser spot on a recording layer of an information recording medium. A lens and a laser beam from the laser element are reflected and incident on the objective lens,
A beam splitter that receives the laser light reflected from the recording layer, repeats reflection inside, and then emits it, a light receiving element that receives the laser light from the beam splitter, the laser element, an objective lens, a beam splitter, and a light receiving element. A plate-shaped holder member to which an element is attached, the holder member being provided at a substantially central portion thereof and a lens hole into which the objective lens is inserted, and the laser element being fixedly provided at one end thereof. A laser beam emitted from the beam splitter, and a laser element attachment part that is provided on the opposite side of the objective lens from the information recording medium and to which the beam splitter is fixed. The light receiving element is fixed to a plate surface position of the holder member irradiated with.

That is, the laser element, the objective lens, the beam splitter and the light receiving element are integrally fixed to the holder member, and the laser beam is reflected by the beam splitter.
Since it is configured to have a predetermined optical path length by being refracted or the like, it is possible to make the device compact and reduce the cost.

The invention according to claim 2 is characterized in that electric circuits of a signal line and a power line of the laser element and the light receiving element are patterned on the holder member via an insulating member.

According to a third aspect of the present invention, the laser light incident on the first surface, which is the incident surface of the parallelogram-shaped beam splitter, is a second surface that forms an acute angle with the first surface, and the first surface is the second surface. Direction, the first surface reflects in the direction of a third surface facing the first surface, the third surface reflects in the direction of a fourth surface forming an acute angle with the third surface, and The light is emitted from four surfaces and is received by the light receiving element.

According to a fourth aspect of the present invention, there is provided a monitor element for detecting the light quantity of the laser light emitted from the laser element, and the laser light from the semiconductor laser is received substantially vertically by the monitor element. A monitor element mounting portion for mounting the monitor element is provided on the holder member between the laser element mounting portion and the hole.

According to a fifth aspect of the present invention, the laser element mounting portion is bent at a predetermined angle, and the laser light emitted from the laser element fixed to the laser element mounting portion is reflected by the beam splitter. It is characterized by doing so.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partial perspective view of an optical pickup device including an optical pickup module according to this embodiment. 2 (a) is a top view of the optical pickup module, and FIG. 2 (b) is an arrow AA in FIG. 2 (a).
FIG. 2C is a cross-sectional view and a side view seen from the direction B in FIG.

The general structure of the optical pickup module is as follows.
A substantially flat plate-shaped holder member 10 that supports each member described later.
0, a laser element 111 that is provided at one end of the holder member 100 and emits a laser beam, an objective lens 101 that is fitted into a lens hole provided at a substantially central portion of the holder member 100 and focuses the laser beam, A light-receiving element 1 for a motor, which is provided between the objective lens 101 and the laser element 111 and detects the amount of laser light emitted from the laser element 111.
12. The light receiving element, which is provided substantially below the objective lens 101, reflects the laser light from the laser element 111 and guides it to the objective lens 101, and refracts and reflects the laser light incident through the objective lens 101 to be described later. It has a beam splitter 113 for guiding to 114, a light receiving element 114 provided on the holder member 100 at the end portion facing the laser element 111, and receiving the laser light from the beam splitter 113.

At the center of one end of the holder member 100, a valve-shaped laser element mounting portion 102 formed by cutting or drawing is bent at a predetermined angle so as to raise the head, and the laser element mounting portion 102 is provided with a laser. Element 111
Is stuck.

The mounting position of the laser element 111 is substantially the same as that of the objective lens 101. Therefore, the laser element mounting portion 102 is bent at a predetermined angle, and the laser light emitted from the laser element 111 is reflected by the objective lens 101.
The beam splitter 113 is provided below the beam splitter 113, and the laser element 111 is not required to be separately attached.

Further, the can type semiconductor laser has a structure that radiates heat through a stem or the like, but in the present invention,
Since it is directly fixed to the holder member 100 by a method such as fusion bonding or pressure bonding, heat is radiated quickly. In particular, when the holder member 100 is made of a metal material having a high thermal conductivity such as aluminum, it is preferable from the viewpoint of lightweight.

Further, between the laser element mounting portion 102 and the objective lens 101, there is provided a pair of monitor mounting portions 103 arranged side by side by a predetermined distance and bent at a predetermined angle. A monitor light receiving element 112 is attached so as to bridge the portion 103. The monitor mounting portion 103 is provided in parallel so that the laser light emitted from the laser element 111 is not blocked by the monitor mounting portion 103.

The beam splitter 113 includes the holder member 1
It is sandwiched by a pair of beam splitter mounting portions 104 formed by bending 00 at 90 degrees.

Under the above structure, a part of the laser light emitted from the laser element 111 is received by the monitor light receiving element 112, and a part of the laser light is incident on the beam splitter 113. The laser light that has entered the beam splitter 113 is reflected by the first surface of the beam splitter 113, enters the objective lens 101, and is condensed by the objective lens 101 to form a spot on the recording layer.

On the other hand, the reflected light reflected from the recording layer is condensed by the objective lens 101, and the beam splitter 11
It is incident on 3. At this time, the reflected light obliquely enters the first surface as convergent light, so that astigmatism occurs due to refraction when entering the beam splitter 113. After that, the reflected light is reflected by the first, second, and third surfaces of the beam splitter 113, emitted from the fourth surface, and received by the light receiving element 114.

Therefore, a focus control signal can be obtained from the reflected light in which astigmatism has occurred by using a four-division element for the light receiving element 114, and a tracking signal can be obtained by using at least two division elements for the light receiving element 114. Obtainable.

The laser light incident through the first surface of the beam splitter 113 is repeatedly reflected from the second surface → the first surface → the third surface, so that the optical beam from the objective lens 110 to the light receiving element 114 is optically reflected. The distance becomes substantially the same as the optical distance from the laser element 111 to the objective lens 101, and the reflected light is imaged on the light receiving element 114. As a result, the reflected light enters the light receiving element 114 through the bent optical path, so that the optical pickup module can be downsized as compared with the conventional structure in which the optical path is linear.

In this case, when the beam splitter 113 'having the structure shown in FIG. 3 is used, the reflected light incident from the first surface is reflected by the second surface and emitted from the fourth surface. Therefore,
Although the optical pickup module can be downsized by reflecting in the beam splitter 113 'as compared with the conventional configuration, the optical pickup module becomes thicker by the length L than in the case described above.

Further, in the astigmatism method, it is necessary to preset the optical distance between the objective lens 110 and the light receiving element 114 to be equal to the distance between the laser element 111 and the objective lens 101 as described above. In this setting, the positions of the beam splitter 113 are set to D1, D as shown in FIG.
It is performed by appropriately adjusting in the 2 and D3 directions (including rotation depending on the situation).

The monitor light receiving element 112114 for detecting the light amount for controlling the power of the laser element 111.
Requires that the light-receiving surface of the monitor light-receiving element 112 is provided so as to face the laser element 111, but it is generally difficult to accurately dispose the three-dimensionally.

However, in the present invention, the monitor mounting portion 103 is provided in the holder member 100 by drawing or notching, and the monitor mounting portion 103 is bent at a predetermined angle so that the light receiving surface of the monitor light receiving element 112 faces the laser element 111. Thus, the three-dimensional structure can be configured with high accuracy and easily.

Further, the thickness of the optical pickup module does not depend on the optical distance between the laser element 111 and the objective lens 110, and the objective lens 110 and the beam splitter 1 are the same.
It is possible to make a thin optical pickup module because it is substantially determined by the distance to 13.

Further, by adding the function of a printed wiring board of an electric circuit as shown in FIG. 4 to the surface of the holder member 100, the laser element 111 and the light receiving element 114 fixed to the holder member 100 by fusion or pressure bonding. It is possible to connect the wiring between the electric circuit and the electric circuit by wire bonding. The terminal Ia in FIG. 4 is connected to the laser element, the terminal Ib is connected to the monitor light receiving element, and the terminal Ic is connected to the light receiving element. And the terminal Id
Is connected and wired to the control unit or the like.

As described above, all the optical systems of the optical pickup module are mounted on one single plate-shaped holder member, so that the optical pickup module can be made compact, lightweight and inexpensive.

[0054]

According to the invention of claim 1, since the laser element, the objective lens, the beam splitter and the light receiving element are integrally provided in the holder member, it is possible to reduce the number of parts of the optical up module. At the same time, downsizing became possible.

According to the second aspect of the invention, since the wiring circuit of the laser element and the light receiving element is patterned on the holder member through the insulating member, the connection to the laser element and the like can be performed easily and surely. It is possible to reduce the number of parts and downsize.

According to the third aspect of the invention, since the reflected light that has entered the beam splitter is reflected and emitted a plurality of times within the beam splitter to adjust the optical path length, the thickness of the optical pickup module can be reduced. It has become possible to make it thinner and downsize.

According to the fourth aspect of the invention, the monitor element mounting portion is provided by cutting and bending the holder member in order to mount the monitor element. Therefore, a dedicated component for mounting the monitor element is not required and the number of parts can be reduced. There was a reduction.

According to the fifth aspect of the invention, since the laser element mounting portion to which the laser element is fixed is provided by cutting and bending the holder member, the emission angle of the laser beam emitted from the laser element is set. It has become possible to set easily.

[Brief description of drawings]

FIG. 1 is a conceptual perspective view of an optical pickup device equipped with an optical pickup module according to the present invention.

FIG. 2 is a configuration diagram of an optical pickup module according to the present invention, in which (a) is a top view and (b) is AA in (a).
FIG. 13C is a cross-sectional view taken along the arrow, and FIG.

FIG. 3 is a diagram illustrating an optical path when the shape of a beam splitter is changed.

FIG. 4 is a diagram showing a pattern of an electronic circuit provided on a holder member.

FIG. 5 is a diagram showing a method of adjusting the position of a beam splitter.

FIG. 6 is an external view of an optical pickup device applied to the description of the conventional technique.

FIG. 7 is an external view of an optical system applied to the description of the conventional technique.

8A and 8B are explanatory views of a can type semiconductor laser device applied to the description of the conventional technique, FIG. 8A is an external view, FIG. 8B is a sectional view, and FIG. 8C is a perspective view of the laser device.

FIG. 9 is a diagram for explaining the principle of the astigmatism method,
(A) is a diagram showing a difference in optical path caused by a difference in distance between the objective lens and the recording layer, (b) shows a case where the distance is longer than the focal length of the objective lens, and (c) shows a relationship between the distance and the focal length. If they are equal, (d) is a diagram showing a spot shape taken by the light receiving element when the distance is shorter than the focal length.

FIG. 10 is a diagram showing the principle of a tracking signal, (a)
FIG. 4A is a diagram showing diffracted light diffracted by a groove, and FIG. 6B is a diagram showing a light intensity distribution of spots formed on the light receiving element by the diffracted light.

[Explanation of symbols]

 100 Holder member 101 Lens hole 102 Laser element mounting part 103 Monitor element mounting part 104 Beam splitter mounting part 110 Objective lens 111 Laser element 112 Monitor light receiving element 113 Beam splitter 114 Light receiving element

Claims (5)

[Claims] 1. An objective lens for condensing laser light emitted from a laser element to form a laser spot on a recording layer of an information recording medium, and reflecting the laser light from the laser element to enter the objective lens. And a beam splitter that receives the laser beam reflected by the recording layer, repeats internal reflection, and then exits; a light receiving element that receives the laser beam from the beam splitter; the laser element, an objective lens, A plate-shaped holder member to which a beam splitter and a light-receiving element are attached, a lens hole into which the objective lens is inserted is provided at a substantially central portion of the holder member, and the laser element is fixed to one end of the holder member. A laser element mounting portion is provided, and the beam splitter to which the beam splitter is fixed on the side opposite to the information recording medium with respect to the objective lens. An optical pickup module, wherein a beam splitter mounting portion is provided, and the light receiving element is fixed to a plate surface position of a holder member irradiated with the laser light emitted from the beam splitter. 2. The optical pickup module according to claim 1, wherein wiring circuits of the laser element and the light receiving element are patterned on the holder member via an insulating member. 3. A laser beam incident on a first surface, which is an incident surface of the parallelogram-shaped beam splitter, is reflected in a direction of the first surface by a second surface forming an acute angle with the first surface, Is reflected by the first surface in the direction of the third surface facing the first surface,
3. The light according to claim 1, wherein the light is reflected by the third surface in a direction of a fourth surface forming an acute angle with the third surface, emitted from the fourth surface, and received by the light receiving element. Pickup module. 4. A monitor element for detecting the amount of laser light emitted from the laser element, wherein the monitor element is attached so that the light receiving surface of the monitor element is substantially perpendicular to the laser light. 4. The optical pickup module according to claim 1, wherein a monitor element mounting portion is provided on the holder member between the laser element mounting portion and the lens hole. 5. A laser beam emitted from the laser element fixed to the laser element mounting portion is bent by a predetermined angle, and the laser beam emitted from the laser element is reflected by the beam splitter. Claim 1
The optical pickup module according to any one of claims 1 to 4.