JPH07334862A - Optical pickup device - Google Patents

Abstract

PURPOSE:To reduce the cost for exchange of components, etc., by installing a holding member which accomodates plural optical components and an attaching mechanism for detachably attaching the holding member to the case of the main body of an optical pickup device. CONSTITUTION:The device is provided with a light source unit which transforms the laser light outputted from a semiconductor laser element 1 into a collimated light beam using a coupling lens 2 and shapes the transformed beam using beam shaping prisms 28, 29. It is also provided with a holding member 25 which holds the light source unit and an attaching base plate 26 which detachably attaches the holding member 25 to the case of the main body. The coupling lens 2 is installed movably in the back-and-forth direction of the optical axis against the holding member 25, and the attaching base plate 26 is provided with a positioning member which arranges the optical axes of plural optical components held in the holding member 25 in a straight line with the reference optical axis of the main body case.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source for converting a laser beam output from a semiconductor laser device into a parallel light beam by a coupling lens and shaping the beam shape of the converted laser beam through a beam shaping prism. The present invention relates to an optical pickup device including a unit.

[0002]

2. Description of the Related Art An optical pickup device, which is provided in an optical disk device for recording data using an optical disk and outputs a laser beam for recording / reproducing / erasing data, outputs a laser beam for recording / erasing data. The level becomes several times higher than the output level at the time of data reproduction, and therefore, the life of the semiconductor laser element used as the light source of the laser beam may become a problem.

For example, the access time during data recording in an optical disk device is the sum of the seek time to the target sector for recording data and the time required to record data on the optical disk. In order to reduce the time required for recording data, it is basically good to increase the output level of the laser beam during data recording so that the temperature of the recording surface of the optical disk can be raised in a short time. .

However, when the output level of the semiconductor laser element is increased, the life of the semiconductor laser element is shortened, and the life of the semiconductor laser element is exhausted even though other elements of the optical pickup device and the optical disk device are sound. Cause

When such a situation occurs, the optical pickup device itself cannot be used, so that the optical disk device cannot be used as it is. Therefore, when such a situation occurs, for example, it is possible to replace the optical pickup device with a new one, but in this case, the cost for that is very high.

Therefore, in the past, for example, Japanese Patent Application Laid-Open No. 61-11.
As disclosed in Japanese Patent No. 0346, there has been proposed one in which the entire optical system unit is replaceably attached to a carriage that moves an optical pickup device. In the case of such a conventional device, only the optical system unit of the optical pickup device needs to be replaced when the life of the semiconductor laser element as described above is exhausted.
The cost at the time of replacement can be reduced.

On the other hand, as another method for shortening the above-mentioned access time, it is preferable to shorten the seek time. For that purpose, it is conceivable to reduce the weight of the elements of the optical pickup device that move in the radial direction of the optical disc.

Therefore, a light source unit for generating a laser beam, a portion (fixed optical system unit) for accommodating a detection optical system unit for receiving a reflected light beam from an optical disc and generating various signals, and a light source unit. The objective lens for converging the laser beam output from the optical disc to the optical disc and its surrounding unit are separated (moving optical system unit), and the moving optical system unit is housed in the carriage.
A so-called separation optical system type optical pickup device in which only the moving optical system unit is moved has been put into practical use.

[0009]

However, in such a separation optical system type optical pickup device, since the moving optical system unit moves over a considerably long distance, the light between the moving optical system unit and the fixed optical system unit is increased. Adjustment of axis alignment becomes extremely difficult. For this reason, as described above, if the fixed optical system unit is to be replaced because the semiconductor laser element has reached the end of its life, the fixed optical system unit and the moving optical system unit after the replacement may be adjusted for optical axis alignment. There is an inconvenience that the cost becomes high.

A semiconductor laser element used as a laser light source and a coupling for converting laser light output from the semiconductor laser element into parallel light, as disclosed in Japanese Patent Laid-Open No. 4-121823, for example. If the lens is built into the same unit and the semiconductor laser element that has reached the end of its life can be replaced with the coupling lens, the cost of the replacement unit can be reduced, but it is difficult to adjust the optical axis alignment after the unit replacement. However, the cost for that is high.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical pickup device capable of simplifying the adjustment work at the time of exchanging the unit when the life of the semiconductor laser device is exhausted. I am trying.

[0012]

According to the present invention, a laser beam output from a semiconductor laser element is converted into a parallel light beam by a coupling lens, and the beam shape of the converted laser beam is shaped through a beam shaping prism. In an optical pickup device including a light source unit for holding, a holding member for housing a plurality of optical components including at least the semiconductor laser element, a coupling lens, and a beam shaping prism,
An attachment mechanism for detachably attaching the holding member to the main body casing is provided. Further, the coupling lens may be provided so as to be movable in the front-rear direction of the optical axis with respect to the holding member. Further, the mounting mechanism may include a positioning member that aligns the optical axes of the plurality of optical components housed in the holding member with the reference optical axis of the main body housing.

[0013]

Therefore, since the light source unit including the semiconductor laser element, the coupling lens and the beam shaping prism is detachably attached to the main body housing, the light source unit should be replaced when the life of the semiconductor laser element is exhausted. The cost for replacement can be reduced. Further, if the adjustment of the optical axis alignment with respect to the reference light flux is performed by the light source unit alone, the adjustment work of the optical axis alignment with respect to the main body housing becomes unnecessary, so that the cost for the adjustment can be significantly reduced.

[0014]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 shows a main part of an optical system of an optical pickup device according to an embodiment of the present invention. In this case, the focusing error is detected by the knife edge method and the tracking error is detected by the push-pull method.

In the figure, the laser light output from the semiconductor laser device 1 is converted into parallel light by the coupling lens 2, passes through the beam splitter 3, enters the objective lens 4, and is focused by the objective lens 4. Then, an image is formed on the recording surface of the magneto-optical disk 5.

The reflected light from the magneto-optical disk 5 is converted into substantially parallel light by the objective lens 4, reflected by the beam splitter 3 and guided to the condenser lens 6, and focused by the condenser lens 6. The reflected light is 60 of the luminous flux.
About 90% is reflected by the splitting mirror 7 that constitutes the knife edge, passes through the half-wave plate 8, and its polarization plane is 45%.
Rotate once.

The S-polarized component and the P-polarized component of the reflected light that has passed through the half-wave plate 8 are reflected by the polarization beam splitter 9. The light of the P-polarized component that has passed through the polarization beam splitter 9 is incident on the light receiving element 10 for tracking error detection, which has a light receiving surface divided into two in the tracking direction. The light of the S-polarized component reflected by the polarization beam splitter 8 is received by the light receiving element 11.

The light beam not reflected by the split mirror 7 has its light-receiving surface divided in two by a split line parallel to the ridge line 7a of the split mirror 7. The light-receiving element 1 for detecting a focusing error.
It is incident on 2.

A tracking error signal is obtained based on the difference between the light receiving signals output from the two light receiving surfaces of the light receiving element 10, and the difference between the light receiving signals output from the two light receiving surfaces of the light receiving element 12 is obtained. A focusing error signal is obtained based on

Further, the sum of the light receiving signals of the light receiving element 10 and
Based on the difference between the light receiving signals of the light receiving element 11, a magneto-optical signal which is a reproduction signal from the user area of the magneto-optical disk 5 is formed, and the light receiving signals output from the two light receiving surfaces of the light receiving element 10, respectively. A reproduction signal from the preformatted area of the magneto-optical disk 5 is formed based on the total sum of the received light signals of the light receiving element 11.

Further, the objective lens 4 is provided with an objective lens actuator (not shown) for moving the objective lens 4 in the focusing direction and the tracking direction.

FIG. 2 shows a part of the main part of the mechanical portion of the magneto-optical disk device to which the optical pickup device of the separation optical system is applied.

In the figure, a magneto-optical disk 5 is detachably attached to a turntable 16 attached to the rotary shaft of a spindle motor 15.

The optical pickup device includes a fixed optical system 18
And a fixed optical system 18
In the case 20 of the semiconductor laser element 1, the coupling lens 2, the beam splitter 3, the condenser lens 6, the split mirror 7, the half-wave plate 8, the polarization beam splitter 9, the light receiving elements 10, 11, and 12, Also, other optical components and the like are stored.

The housing 21 of the moving optical system 19 includes the objective lens 4, a deflection prism 22 for deflecting the optical axis of the fixed optical system 18 in the direction of the objective lens 4, and other optical parts. A seek mechanism 23 is provided for accommodating and moving the magneto-optical disk 5 in a radial direction.

Further, as shown in FIG. 3, the fixed optical system 18
A light source housing 25 accommodating a light source unit such as the semiconductor laser element 1 and the coupling lens 2 is detachably attached to the housing 20. In addition, in FIG.
The same reference numerals are attached to the parts corresponding to the respective elements.

The light source housing 25, as shown in FIG.
An accommodating portion 25a penetrating the inside thereof is provided, and the semiconductor laser element 1 is fixed to one opening end 25aa of the accommodating portion 25a while being attached to the attachment substrate 26. In addition, the semiconductor laser device 1 of the housing portion 25a
The coupling lens 2 is fixed in the vicinity of in the state of being housed in the lens holder 27.

A pair of beam shaping prisms 28, 29 for shaping the beam shape of the parallel light flux passing through the coupling lens 2 into a substantially circular shape are arranged in the vicinity of the opening end 25ab on the opposite side of the housing portion 25a. It is set up. Further, the positioning members 30 and 31 are for defining the mounting positions of the beam shaping prisms 28 and 29 in the housing portion 25a.

A mounting seat 25b is provided around the open end 25ab, and the mounting seat 25b and the housing 20 are provided.
The reference plate 32 is sandwiched between the two, and screws 33 and 34 commonly inserted in the holes 25ba and 25bb formed in the mounting seat 25b and the holes 32a and 32b formed in the reference plate 32, respectively. As a result, the light source housing 25 becomes the housing 2
It is attached to 0. The reference plate 32 is fixed to the mounting seat 25b of the light source housing 25 by adhesion.

The direction perpendicular to the plane of FIG. 4 is the Y direction,
Assuming that the direction parallel to the optical axis of the semiconductor laser device 1 is the Z direction and the direction perpendicular to both the Z direction and the Y direction is the X direction, the mounting position of the mounting substrate 26 with respect to the opening end 25aa is the X direction and the Y direction. It is possible to move a minute distance. Further, the lens holder 27 can be moved in the Z direction at a stage before fixing the position in the housing portion 25a.

Here, as shown in FIGS. 5A and 5B, the beam shape (far-field image) of the laser beam output from the semiconductor laser device 1 is perpendicular to the beam emission surface of the semiconductor laser device 1. In the case of an elliptical shape in which the major axis is arranged in the direction (parallel to the Y direction in this case), the beam shaping prisms 28 and 29 cause the beam width in the horizontal direction (parallel to the X direction in this case) to be the vertical direction. The beam is shaped so that it is equal to the beam width of. At this time, assuming that the beam width in the horizontal direction before shaping is a and the beam width in the vertical direction is b, the beam shaping magnification γ in this case is γ = (a / b).

That is, considering the laser beam after the beam shaping, the horizontal focal length of the coupling lens 2 is equivalent to γ times the actual focal length.

For example, considering an optical system from the semiconductor laser device 1 to the magneto-optical disk 5, as shown in FIG.
The focal length of the coupling lens 2 in the vertical direction is fc, whereas the focal length of the coupling lens 2 in the horizontal direction is γ × fc.

Generally, in the semiconductor laser element 1, the shape of the output beam differs depending on the chip shape in the vertical direction and the horizontal direction, and the spot formed when this beam is focused contains astigmatism. Be done. Considering the emission point side of the semiconductor laser device 1, the emission point in the beam vertical direction is
While it coincides with the end face of the semiconductor laser device 1, the light emitting point in the horizontal direction of the beam is located behind the end face of the semiconductor laser device 1 by the astigmatic difference δ.

In order to eliminate such astigmatism,
It is advisable to move the coupling lens 2 in the front-back direction of the optical axis so that the horizontal focal position of the objective lens 4 and the vertical focal position of the objective lens 4 coincide with each other.

That is, when the focal position of the coupling lens 2 is moved by the distance ε from the end face of the semiconductor laser device 1, the focal position of the objective lens 5 is changed.
Compared with the case where the is not moved, it is moved by the distance Sh in the horizontal direction and by the distance Sv in the vertical direction (see FIG. 6).

Here, as described above, since the horizontal focal length of the coupling lens 2 is equivalent to γ times the actual focal length fc, the movement of the coupling lens 2 causes the objective to move. Distances Sh and Sv with which the focal position of the lens 4 moves are expressed by the following equations (I) and (II), respectively.

Sh = ((fo / fc) ^ 2) × ε (I)

Sv = ((fo / fc) ^ 2) × (ε + δ) / (γ ^ 2) (II)

Here, fo is the focal length of the objective lens 4. Note that x ^ n is an operator that represents an operation that is the n-th power of x.

In order to match the focal position of the objective lens 4 in the vertical direction and the horizontal direction, the relationship of Sh = Sv should be established. Therefore, from the above equations (I) and (II), the following equation (III) ) Is required.

Ε = δ / ((γ ^ 2) -1) (III)

From the above, the objective lens is moved by moving the coupling lens 2 in the Z direction inside the light source housing 25 by the distance ε determined by the astigmatic difference δ of the semiconductor laser device 1 and the beam shaping magnification γ. The astigmatic difference of the spot condensed by 4 can be made "0", and astigmatism can be eliminated.

For adjusting the position of the coupling lens 2 as described above, as shown in FIG. 7, the light source housing 25 is provided with the same mounting mechanism for the light source housing 25 as the housing 20 of the fixed optical system 18. It is done by attaching it to 40. The state (position, direction, etc.) of the optical axis of the adjusting device 40 with respect to the mounting mechanism of the optical housing 25 is set to the same positional relationship as the state of the optical axis of the housing 20 with respect to the mounting mechanism of the optical housing 25. There is.

The adjusting device 40 is a device for detecting astigmatic difference by the double cross knife edge method. In this double cross knife edge method, an incident beam (in this case, a laser beam emitted from the light source housing 25) is focused by a condenser lens to form a beam waist, and diffused light after the beam waist is received by a light receiving element. Before and after the beam waist, the output of the light receiving element is differentiated when the light is received and the light is shielded at a constant speed by the knife edge in two directions perpendicular to the beam optical axis of the beam and orthogonal to each other. The intensity difference in the direction is obtained, and the astigmatic difference is detected thereby.

In addition to this, the adjusting device 40 also measures the inclination of the output optical axis of the semiconductor laser element 1, measures the parallelism of the laser light after passing through the coupling lens 2, and shifts the optical axis. Can be measured.

A mounting mechanism for the light source housing 25 of the adjusting device 40,
An example of the reference plate 32 is shown in FIG.

As described above, the reference plate 32 has
Holes 32a and 32b into which screws for fixing are inserted are formed, a window 32c for passing a laser beam output from the light source housing 25, and a pin (described later) for positioning are inserted. Hole 32d and long hole 3
2e is formed.

The adjusting mechanism 40 has a mounting mechanism in which a window 40a for passing a laser beam output from the light source housing 25, a screw hole 40b into which a screw for fixing the light source housing 25 is screwed, 40c and pins 40d and 40e for defining the reference position are provided.

When the light source housing 25 is attached to the adjusting device 40, first, the pins 40d,
The reference plate 32 is positioned so as to be inserted into the hole 32d and the long hole 32e of the reference plate 32, and attached to the adjusting mechanism 40.
While the 5 is aligned with the reference plate 32, it is screwed to temporarily fix the light source housing 25 to the adjusting device 40.

In this way, when the light source housing 25 is attached to the adjusting device 40, the semiconductor laser element 1 is turned on, and first, the adjusting device 40 observes the angle of the optical axis tilt of the output optical axis of the semiconductor laser element 1. However, the semiconductor laser device 1
The position adjustment of the semiconductor laser device 1 in the X and Y directions is performed so that the optical axis tilt of the output optical axis of is 0.

Next, while observing the parallelism of the laser light output from the coupling lens 2 by the adjusting device 40, the parallelism of the laser light is optimized.
The position of the coupling lens 2 in the Z direction is adjusted.

Then, the astigmatic difference is detected by the adjusting device 40, and the position of the coupling lens 2 in the Z direction is adjusted so that the astigmatic difference is minimized.

Finally, while detecting the deviation between the optical axis of the output laser beam and the reference optical axis of the adjusting device 40,
By appropriately moving the optical housing 25 in the X and Y directions,
So that the optical axis of the output laser beam matches the reference optical axis,
Adjust the optical axis.

When the adjustment of the optical housing 25 is completed in this way, the optical housing 25 is fixed to the reference plate 32 by adhesion or the like so that the adjusted state does not shift.

When the adjustment work is completed, the optical housing 25 is removed from the adjusting device 40 together with the reference plate 32, and the optical housing 25 and the reference plate 32 are removed as shown in FIG.
Is attached to the housing 20 of the fixed optical system 18 and fixed by screwing.

Here, as described above, the mounting mechanism for mounting the optical housing 25 and the reference plate 32 in the housing 20 has the same structure as the mounting mechanism for mounting the optical housing 25 and the reference plate 32 in the adjusting device 40. Therefore, the reference plate 32 is aligned so that the reference pin (not shown) provided on the housing 20 is inserted into the hole 32d and the long hole 32e of the reference plate 32. 25 is screwed to the housing 20 (see FIG. 9).

As described above, the reference plate 32 is fixed to the adjusting device 40 while being positioned, and in this state, the adjustment of each optical element accommodated in the optical housing 25 and the optical axis adjustment are performed. Since the optical housing 25 is adhesively fixed to the reference plate 32 after the adjustment is completed, the adjusted state of each optical element of the optical housing 25 is equivalent to that made with the reference plate 32 as a reference. .

Therefore, the reference plate 32 is attached to the housing 20.
At the time of attachment, the adjustment state of each optical element of the optical housing 25 maintains the adjustment state with the adjustment device 40, and exhibits good optical characteristics.

In this way, the optical housing 25 is attached to the housing 20.
When the optical pickup device is completed after being fixed to the above, other elements are assembled to complete the magneto-optical disk device.
After this, when the magneto-optical disk device is used and the semiconductor laser element 1 deteriorates and its life is exhausted, the optical housing 25 may be replaced. in this case,
The optical housing 25 to be newly mounted may be mounted on the adjusting device 40 and adjusted in the same manner as described above in the state before mounting.

As a result, a new semiconductor laser element 1 can be used in place of the semiconductor laser element 1 that has reached the end of its life, and the magneto-optical disk device can exhibit its initial performance.

As described above, in this embodiment, since the semiconductor laser element 1 can be replaced, a magneto-optical disk device with low running cost can be realized.

Since the optical axis of the semiconductor laser device 1, the parallelism of the laser beam, and the astigmatic difference can be adjusted only by the optical housing 25, the adjustment work is easy. Can be something.

FIG. 10 shows an optical housing of an optical pickup device according to another embodiment of the present invention. In the figure, the same parts as those in FIG. 4 and corresponding parts are designated by the same reference numerals.

In this case, the laser beam converted into parallel light by the coupling lens 2 is beam-shaped by one beam shaping prism 45 and then guided to the housing 20 of the fixed optical system 18.

Further, in the optical housing 46 that houses the semiconductor laser element 1, the coupling lens 2, and the beam shaping prism 45, the optical axis of the laser beam after passing through the beam shaping prism 45 is the housing 20. The whole shape is shaped like a dogleg to match the optical axis.

A mounting seat 46b is provided around the opening end 46a of the optical housing 46.
In b, holes 46c, 46 into which screws 33, 34 for screwing to the housing 20 via the reference plate 32 are inserted are provided.
d is provided.

In this way, the present invention can be similarly applied to the case where the beam shaping is performed using only one beam shaping prism 45.

In the above-described embodiments, the case where the present invention is applied to the optical pickup device of the magneto-optical disk device has been described, but the present invention can be applied to other optical pickup devices in the same manner. it can.

In the above-mentioned embodiment, the focusing optical system is provided with the knife edge method for detecting the focusing error and the push-pull method for detecting the tracking error. The detection optical system is not limited to the one described above.

[0072]

As described above, according to the present invention,
Since the light source unit consisting of the semiconductor laser element, the coupling lens and the beam shaping prism is detachably attached to the main body housing, when the life of the semiconductor laser element is exhausted, the light source unit may be replaced. The effect of being able to reduce the cost is obtained. Also, if the adjustment of the optical axis alignment with respect to the reference light flux is performed by the light source unit alone, the adjustment work of the optical axis alignment with respect to the main body housing becomes unnecessary, so that the cost for the adjustment can be significantly reduced. Also get the effect.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an optical system of an optical pickup device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an example of a main part configuration of a magneto-optical disk device according to an embodiment of the present invention.

FIG. 3 is a schematic plan view showing an example of a main part configuration of a magneto-optical disk device according to an embodiment of the present invention.

FIG. 4 is a schematic partial cross-sectional view showing an example of the configuration of an optical housing according to an embodiment of the present invention.

FIG. 5 is a schematic diagram for explaining the operation of a beam shaping prism.

FIG. 6 is a schematic diagram for explaining adjustment of astigmatism.

FIG. 7 is a schematic partial perspective view showing an example of a state in which the optical housing is attached to the adjusting device.

FIG. 8 is a schematic partial view showing an example of a mounting mechanism of the adjusting device.

FIG. 9 is a schematic partial view showing an example of a state in which an optical housing is attached to a housing of a fixed optical system.

FIG. 10 is a schematic partial cross-sectional view showing an example of the configuration of an optical housing according to another embodiment of the present invention.

[Explanation of symbols]

 1 Semiconductor Laser Element 2 Coupling Lens 25,46 Optical Housing 26 Mounting Substrate 27 Lens Holder 28,29,45 Beam Shaping Prism 32 Reference Plate

Claims (3)

[Claims] 1. An optical pickup provided with a light source unit for converting a laser beam output from a semiconductor laser device into a parallel light beam by a coupling lens and shaping the beam shape of the converted laser beam through a beam shaping prism. The apparatus is provided with a holding member for accommodating a plurality of optical components including at least the semiconductor laser element, the coupling lens, and the beam shaping prism, and an attachment mechanism for detachably attaching the holding member to the main body housing. Characteristic optical pickup device. 2. The optical pickup device according to claim 1, wherein the coupling lens is provided so as to be movable in the front-rear direction of the optical axis with respect to the holding member. 3. The mounting mechanism includes a positioning member that aligns optical axes of the plurality of optical components housed in the holding member with a reference optical axis of the main body casing. The optical pickup device according to claim 1.