JPH09282700A - Information recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use an optical block in common even when a fixing position of an optical element to the optical block is shifted by providing 1st and 2nd abutting surfaces for positioning a condenser lens in a different position on a condenser lens fixing part. SOLUTION: This fixing optical block 15 is for fixing the following parts and elements, etc. A cross-sectional shape of emitted light from a semiconductor laser is shaped and the shaped light is divided into two beams by shaping surfaces 31a and 32a of polarization beam splitters 31 and 32. One of the two divided beams is converged by the condenser lens 13, and the converged light is received by a phtodetector 6. Then, the optical block 15 has the condenser lens fixing part 16, and the condenser lens fixing part 16 is provided with the 1st abutting surface and the 2nd abutting surface for positioning the condenser lens 13 in a 1st position in the direction orthogonal to an optical axis of the condenser lens 13 and a position different from this 1st position respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording / reproducing apparatus for optically recording and / or reproducing information, and more particularly to an optical block for arranging each optical element in an optical head.

[0002]

2. Description of the Related Art As an optical head for optically recording and / or reproducing information on / from a recording medium, Japanese Patent Laid-Open No. Hei.
There is one disclosed in Japanese Patent No. 347029 (conventional example 1). FIG. 9 shows the optical head disclosed in Japanese Patent Laid-Open No. 5-347029. The optical head disclosed in JP-A-5-347029 will be described below with reference to FIG. The collimator lens 2 is provided in the emission direction of the emitted light from the semiconductor laser 1, and the polarization beam splitter 3 is provided in the transmission direction of the light beam passing through the collimator lens 2. The polarization beam splitter 3 has a first surface 3a, a second surface 3b, and a third surface 3c. The first surface 3a is provided with a polarizing film and splits incident light. In the reflection direction of the light beam reflected by the first surface 3a, the light detection element 6
Is provided. In the reflection direction of the light ray totally reflected by the second surface 3b on which the light ray transmitted through the first surface 3a is incident,
The objective lens 4 is provided. The light beam that has passed through the objective lens 4 is applied to the recording medium (magneto-optical recording medium) 5, and the light beam reflected here follows the same path as the outward path, enters the first surface 3a, and is reflected here. The third ray of light enters
The surface 3c is formed so as to be parallel to the emission direction of the light transmitted through the second surface 3b and the emission light from the semiconductor laser 1. A half-wave plate 7, a condenser lens 8, and a beam splitter 9 are provided in the transmission direction of the second surface 3b through which the light rays reflected by the third surface 3c are transmitted. Further, the light detecting element 10 is provided in the transmitting direction of the light ray passing through the beam splitter 9, and the light detecting element 11 is provided in the reflecting direction of the light ray reflected by the beam splitter 9. The semiconductor laser 1, the collimator lens 2, the polarization beam splitter 3, the photodetector 6, the half-wave plate 7, the condenser lens 8, the beam splitter 9, and the photodetectors 10 and 11 are
It is fixed to a fixed optical block.

Next, the operation of the optical head configured as described above will be explained. The emitted light emitted from the semiconductor laser 1 is collimated by the collimator lens 2 and the first surface 3a of the polarization beam splitter 3 is described. Incident at an angle. The light beam that has entered the first surface 3a is separated into reflected light and transmitted light, and the reflected light enters the photodetector 6 and the output of the semiconductor laser 1 is detected. On the other hand, the transmitted light is beam-shaped by being transmitted through the first surface 3a, is incident on the second surface 3b at an angle equal to or greater than the critical angle, and is totally reflected toward the recording medium 5. In this way, the light beam totally reflected passes through the objective lens 4 to become a focused light beam, and a beam spot is irradiated on the surface of the magneto-optical recording medium 5.

The light beam reflected by the magneto-optical recording medium 5 follows the same path as the outward path, passes through the objective lens 4, is reflected by the second surface 3b of the polarization beam splitter 3, and returns to the first surface 3a. The light rays that have entered the first surface 3a are reflected here and enter the third surface 3c. The light beam incident on the third surface 3c is reflected here, passes through the second surface 3b, becomes parallel to the emitted light from the semiconductor laser 1, and enters the half-wave plate 7. The light beam that has passed through the half-wave plate 7 is condensed by a condenser lens 8 and then enters a beam splitter 9 to be divided into two light beams. The divided light beams are respectively received by the photodetector element 10 and the photodetector element 11.

As another optical head, there is one disclosed in Japanese Patent Publication No. 6-19864 (Prior Art 2) shown in FIG. The optical head will be described below with reference to FIG. Reference numeral 101 denotes a semiconductor laser that generates a light beam for recording and reproduction, 102 denotes a collimator lens that converts a divergent light beam emitted from the semiconductor laser 101 into a parallel light beam,
Reference numeral 105 denotes an information recording medium, 103 denotes a beam splitter for separating reflected light from the information recording medium 105, which is a half prism that transmits 50 to 90% of incident light and reflects the rest. It has characteristics. Reference numeral 106 denotes a photodetector for detecting the intensity of the emitted light of the semiconductor laser 1, and 113 denotes a part of the emitted light from the semiconductor laser 101 reflected by the beam splitter 103 to be focused on the light receiving surface of the photodetector 106. Lens for, 104
Is emitted from the semiconductor laser 101 and collimator lens 10
2 is converted into a parallel light beam by the beam splitter 103
An objective lens for condensing the parallel light flux that has passed through the information recording medium 105, and 109, which guides the light flux reflected by the information recording medium 105 and bent in the traveling direction by the beam splitter 103 to the information signal reproducing system 120. , A beam splitter for guiding a part thereof to the servo signal detection system 130. Here, the information signal reproducing system 120 includes an analyzer 112 for converting the polarization plane rotation in the information signal light from the information recording medium 105 into an intensity change, a photodetector 110 for converting the information signal light into an electric signal, and an analyzer. It is composed of a lens 14 for guiding the information signal light converted into the intensity fluctuation signal by 112 to the signal detecting photodetector 110. Further, the servo signal detection system 130 includes the converging lens 1
15, a cylindrical lens 1116 for an astigmatic focus sensor, and a 6-division photodetector 111 for servo.

The information signal reproducing operation of this optical head will be described below. The divergent light beam emitted from the semiconductor laser 101 is converted into a parallel light beam by the collimator lens 102, passes through the beam splitter 103, and is condensed on the information recording medium 105 by the objective lens 104. A magnetic thin film having a magneto-optical effect is coated on the information recording medium 105, and information recording pits having a width of about 1 μm are recorded on the magnetic thin film. In the information recording pit, the direction of the perpendicular magnetization is opposite to the direction around it, and the polarization direction of the reflected light is + θk depending on the direction of the magnetization.
Alternatively, it rotates by a rotation angle of -θk. Then, the reflected light from the information recording medium 105 passes through the beam splitter 103 and the beam splitter 109 and is guided to the analyzer 112. The rotation of the polarization plane in the information recording medium 105 is converted into a change in light intensity by the analyzer 112, and the photodetector 11
It is converted into an electric signal by 0. On the other hand, a part of the irradiation light is reflected by the beam splitter 103 and focused on the photodetector 106 by the lens 113. By condensing light by the lens 113 and irradiating the light on the photodetector 106, the photodetector 106 can have a high bandwidth and high-speed response can be realized. Since the output of the photodetector 106 is proportional to the intensity of the emitted light of the semiconductor laser 101, by feeding back this electric output to the drive circuit of the semiconductor laser 1, the irradiation light output to the information recording medium 105 becomes constant. To be kept.

As described above, the optical head shown in FIG. 11 can be considered based on the two prior arts. That is, it is an optical head in which the condenser lens 13 is arranged between the polarization beam splitter 3 and the photodetection element 6 in the optical head shown in FIG. Reference numeral 15 is a fixed optical block, 16 is a movable optical block, and 14 is a rising mirror that is mounted on the movable optical block and that changes the optical axis of the outward light emitted from the polarization beam splitter toward the objective lens.

For fixing the condenser lens 13 to the fixed optical block 15, as shown in FIG. 12, the condenser lens 13 is fixed in the radial direction of the condenser lens 13 with respect to the V-groove shaped condenser lens fixing portion 16 formed in the optical block. As for the condensing lens 1, the outer cylindrical portion of the condensing lens 13 is applied to the fixed portion 16, and
Regarding the optical axis direction of 3, the lens surface of the condenser lens 13 is brought into contact with the adjustment pin to determine the position, and then fixed by adhesion.

Regarding the fixing of the polarization beam splitter 3 to the optical block 15, the polarization beam splitter 3
After positioning, the adhesive is directly bonded and fixed to the optical block 15 by an adhesive. In addition, the optical block 1 of the light detection element 6
For fixing to 5, the photodetector 6 is attached to the printed circuit board 1
9 and fix the printed circuit board 19 to the optical block 15
It is fixed by screwing in.

[0010]

However, in semiconductor lasers, the divergence angle of the emitted light differs depending on each manufacturer. When semiconductor lasers having different divergence angles are used, in order to make the cross-sectional shapes of the light beams emitted from the polarization beam splitter 3 toward the objective lens 4 substantially the same, the polarization beam splitter 3 is adjusted in accordance with the divergence angle. It is necessary to change the incident angle on the first surface 3a to change the shaping ratio.

FIG. 13 shows a polarization beam splitter 31 (shown by a thin solid line) having a shaping surface with a shaping ratio of 2.3, and a locus of light rays in the polarization beam splitter 31 (shown by a dashed line). A polarization beam splitter 32 having a shaping surface with a ratio of 2.75 (illustrated by a thick solid line) and a locus of light rays in the polarization beam splitter 32 (illustrated by a thick dashed line) are shown. As can be seen from FIG. 13, even if the shaping ratio is changed, the light beam (a) incident from the semiconductor laser is adjusted by adjusting the shape of the polarization beam splitter.
Then, the optical axes of the light beam (b) emitted to the objective lens side and the light beam (c) emitted to the half-wave plate 7 side can be aligned. However, the light ray (d) traveling toward the condenser lens 13 follows a different path. That is, when the semiconductor laser is changed and the divergence angle is different, and the shaping ratio of the shaping surface of the polarization beam splitter is changed accordingly, the layout of the optical system in the optical block 15 is as shown in FIG. Splitter 31
(When using the beam splitter 32) and (b) (when using the beam splitter 32).
The fixing positions of 1, 32, the condenser lens 13, and the detection element 6 to the optical block 15 are displaced.

Therefore, when the semiconductor laser is changed and the divergence angle of the light emitted from the semiconductor laser is changed, it is necessary to change the optical block for fixing the optical system, which cannot be used in common. Will end up. In view of the above problems, the present invention provides an information recording / reproducing apparatus having an optical block that can be used in common even if the fixing position of the optical element that constitutes the optical system is deviated to the optical block. To aim.

[0013]

In order to solve the above-mentioned problems, the present invention solves the above problems by emitting a semiconductor laser, shaping means for shaping the cross-sectional shape of the light from the semiconductor laser, and shaping by the shaping means. Splitting means for splitting the split light into two lights, a condenser lens for focusing one light split by the splitting means, and a photo-detecting element for receiving the light focused by the focusing means , The semiconductor laser,
In an information recording / reproducing device having a shaping means, a dividing means, a condensing lens, and an optical block for fixing a photodetector, the optical block has a fixing means for fixing the condensing lens, and the fixing means includes: A first contact surface and a second contact surface for positioning the condenser lens at a first position in a direction orthogonal to the optical axis of the condenser lens and at a position different therefrom are provided.

A condenser lens is brought into contact with the first contact surface of the fixing means directly or through a lens frame to position the condenser lens at the first position and to contact the second contact surface. Directly contacts the condenser lens via the lens frame, and positions the condenser lens at a position different from the first position (for example, the second position). When there are three or more positions where the condenser lens should be positioned, a spacer is arranged between the first contact surface and the condenser lens, and the condenser lens is brought into contact with the spacer for positioning. Let

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIGS. 1 to 4 show a first embodiment of the present invention. 1A and 1B are optical blocks of the polarization beam splitter 3, the condenser lens 13, and the detection element 6 when the shaping ratio of the polarization beam splitter 3 is changed according to the spread angle of the semiconductor laser 1. 2 (a) and 2 (b) are diagrams showing details of fixing the condenser lens in the condenser lens fixing portion of the optical block. FIG. 3 is a diagram showing a photo-detecting element fixed to the optical block 15, and FIG. 4 is a diagram showing position adjustment of a polarization beam splitter attached to the fixed optical block. Since the entire optical system is the same as that shown in FIG. 14, the description is omitted.

In FIG. 1, FIG. 1A shows a shaping ratio 2.3.
1 shows the arrangement of the polarization beam splitter 31, the condenser lens 13, and the photodetector 6 in the fixed optical block (hereinafter, simply referred to as an optical block) 15 when the polarization beam splitter 31 having the shaping surface of FIG. (B) shows the arrangement of the polarization beam splitter 32, the condenser lens 13, and the photodetector 6 in the optical block 15 when the polarization beam splitter 32 having a shaping surface with a shaping ratio of 2.75 is used.

On the bottom surface 15a of the optical block 15, a polarization beam splitter to be fixed (in this embodiment, a polarization beam splitter 31 having a shaping surface with a shaping ratio of 2.3) is fixed.
And a polarization beam splitter 32 having a shaping surface with a shaping ratio of 2.75) is formed outside the position where the polarization beam splitter 32 is to be fixed, and three holes 15b for adjusting the inclination and position of the polarization beam splitter to be fixed are formed. ing. These three holes 1
Each of 5b is formed to be larger than an adjustment pin of an adjustment jig to be described later, and the size thereof is large enough to correspond to the amount of deviation between the fixed positions of the two polarization beam splitters 31 and 32. Is formed.

Further, the bottom surface 15a of the optical block 15 is provided with a U-shaped condenser lens fixing portion 16 (see FIGS. 1 and 2). The two side walls 16a and 16b of the condenser lens fixing portion 16 are locations where the outer cylindrical portion of the condenser lens 13 is applied. The position of one side wall 16a of the two side walls is such that the optical axis of the reflected light from the polarization beam splitter 31 enters the condenser lens 13 when the condenser lens 13 is applied to the one side wall 16a. The position of the other side wall 16b is
When the condenser lens 13 is applied to the other side wall 16 b, the optical axis of the reflected light from the polarization beam splitter 32 enters the condenser lens 13. The two side walls 16a and 16b are provided for position adjustment in a plane substantially orthogonal to the optical axis of the condenser lens 13.

A hole 15c is formed in the optical block bottom surface 15a between the two side walls 16a and 16b of the condenser lens fixing portion 16. The hole 15c is used to adjust the position of the condenser lens 13 in the optical axis direction, and a positioning adjustment pin is inserted into the hole 15c, which will be described later. A screw hole for screwing the printed circuit board 19 holding the photodetecting element 6 is formed on a side surface 15d formed in a direction perpendicular to the bottom surface 15a of the optical block 15 (not shown). An elongated hole 19a is formed in the printed circuit board 19 so as to correspond to the screw hole of the optical block 15. The long hole 19a is formed on the printed circuit board 19
The photodetection element 6 held above is formed to extend to such an extent that position adjustment can be performed so that it can receive each of two lights having different optical axes reflected by the two shaping surfaces (FIG. 3 (a)).

Next, the fixing of the polarization beam splitter 31, the condenser lens 13, and the photodetector 6 when the polarization beam splitter 31 is used depending on the semiconductor laser used will be described. First, fixing the polarization beam splitter 31 will be described with reference to FIG. When the polarization beam splitter 31 is fixed to the optical block 15, a dedicated adjustment jig 41 for the polarization beam splitter 31 is used. The adjusting jig 41 is a single board 41a.
And three adjusting pins 41b implanted from the substrate. The three adjusting pins 41b of the adjusting jig 41 are respectively inserted into the three holes 15b formed in the bottom surface 15a of the optical block 15, and the side surface of the polarization beam splitter 31 is abutted against the holes. The tilt and position of the polarization beam splitter 31 are adjusted by the adjusting jig 41, and when the fixing position is determined, the polarization beam splitter 31 is adhesively fixed to the optical block 15 with an adhesive.

Next, the fixing of the condenser lens 13 will be described with reference to FIG. In the condenser lens 13, the outer cylindrical portion of the condenser lens fixing portion 16 formed on the optical block 15 is abutted against the left side wall 16a in the figure.
Then, the outer cylindrical portion of the condenser lens 13 and the right side wall 16
The leaf spring 17 is bent and inserted between it and b, and the condenser lens 13 is biased to the left side wall 16a.

In this state, the position of the condenser lens 13 is adjusted in the optical axis direction. For position adjustment in the optical axis direction, the light spot formed by the condenser lens 13 is used as the light detection element 6.
The position of the condenser lens 13 is adjusted so that the condenser lens 13 is positioned on the light receiving surface of the. Two adjusting pins 42 are inserted through the holes 15c formed in the bottom surface 15a of the optical block 15 between the two side walls of the condenser lens fixing portion 16, and the adjusting pins 42 are attached to the lens surface of the condenser lens 13. Then, the position of the condenser lens 13 in the optical axis direction is adjusted. When the adjustment is completed, the condenser lens 13 is attached to the condenser lens fixing portion 1 by an adhesive.
Adhesively fixed to 6.

Next, the fixing of the photodetector 6 will be described with reference to FIGS. 3 (a) and 3 (b). Shaping ratio 2.
The light reflected by the shaping surface 31a of No. 3 is condensed by the condensing lens 13, and forms a light spot on the left side of the optical block 15 in the figure as illustrated in FIG. Therefore, the printed circuit board 19 must be fixed to the left side of the optical block 15 in order to form the light spot on the light receiving surface of the light detection element 6 (see FIG. 3B). The printed board 19 is screwed and fixed to the optical block 15 by aligning the right end of the elongated hole 19a formed so as to extend in the longitudinal direction of the printed board 19 with the screw hole formed on the side surface 15d of the optical block 15. To do.

As described above, when the polarization beam splitter 31 having the shaping surface with the shaping ratio of 2.3 is used, the polarization beam splitter 31, the condenser lens 13 and the photodetector 6 are used.
Is fixed to the optical block 15. Next, fixing of the polarization beam splitter 32, the condenser lens 13, and the photodetector 6 when the polarization beam splitter 32 having a shaping surface with a shaping ratio of 2.75 is used for the same optical block 15 will be described.

First, fixing the polarization beam splitter 32 will be described with reference to FIG. When fixing the polarization beam splitter 32 to the optical block 15, the adjustment jig 51 for the polarization beam splitter 32 is used. Like the adjusting jig 41 for the polarization beam splitter 31, the adjusting jig 51 is composed of one substrate 51a and three adjusting pins 51b implanted from the substrate 51a. However,
The positional relationship between the three adjustment pins 51b is naturally different from that of the adjustment jig 41 for the polarization beam splitter 31. The adjustment of the tilt and the position of the polarization beam splitter 32 is the same as the above-mentioned case, and thus the description thereof is omitted.

Next, the fixing of the condenser lens 13 will be described with reference to FIG. The outer shape cylindrical portion of the condenser lens 13 is applied to the side wall 16b on the right side of the figure of the condenser lens fixing portion 16 formed in the optical block 15.
Then, the outer cylindrical portion of the condenser lens 13 and the left side wall 16
The leaf spring 17 is bent and inserted between a and a, and the condenser lens 13 is biased to the right side wall 16b.

In this state, the position of the condenser lens 13 in the optical axis direction is adjusted. Regarding the position adjustment in the optical axis direction,
The description is omitted because it is similar to the above case. next,
Regarding the fixation of the photo-detecting element 6, FIGS. 3 (a) and 3 (c)
This will be described with reference to FIG. The light reflected by the shaping surface 32a having a shaping ratio of 2.75 is condensed by the condenser lens 13, as shown in FIG.
As shown in (b), a light spot is formed on the right side of the side surface 15d of the optical block 15 in the figure. Therefore, the printed circuit board 19 must be fixed to the right side of the optical block 15 in order to form the light spot on the light receiving surface of the light detection element 6 (see FIG. 3C). The printed board 19 is screwed and fixed to the optical block 15 by aligning the left end of the elongated hole 19a formed extending in the longitudinal direction of the printed board 19 with the screw hole formed on the side surface 15d of the optical block 15. .

As described above, when the polarization beam splitter 32 having a shaping surface with a shaping ratio of 2.75 is used, the polarization beam splitter 32, the condenser lens 13 and the photodetector 6 are fixed to the optical block 15. As explained above,
According to the present embodiment, the common optical block can be used even if the shaping ratio of the shaping surface formed on the polarization beam splitter is changed according to two types of semiconductor lasers having different divergence angles to be emitted. Therefore, the range of selection of the semiconductor laser to be used can be widened, and the cost can be reduced. (Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. It should be noted that description of portions that are the same as those of the first embodiment will be omitted.

The optical block 25 of this embodiment can be shared even when there are three or more types of polarization beam splitters having shaping surfaces having different shaping ratios according to the semiconductor laser. The configuration will be described below with reference to FIG. FIG. 5 is a diagram showing details of a modified example of the condenser lens fixing portion 26.

Two side walls 26 of the condenser lens fixing portion 26
a and 26b are formed according to the light reflected by the shaping surface having the smallest shaping ratio and the largest shaping ratio. That is, when a polarization beam splitter having a shaping surface with the smallest shaping ratio is used, the external shape cylindrical portion of the condenser lens 13 is abutted against the side wall 26a on the left side in the figure to be fixed by adhesion, and the converging lens 13 with the largest shaping ratio is obtained. When a polarization beam splitter having a shaping surface is used, the external shape cylindrical portion of the condenser lens 13 is applied to the side wall 26b on the right side in the figure and fixed by adhesion.

When a polarizing beam splitter having a shaping surface with a shaping ratio between the smallest shaping ratio and the largest shaping ratio is used, the spacer 2 having a thickness determined accordingly is used.
1 is attached to the side wall 26a on the left side in the figure to be fixed by adhesion, and the outer cylindrical portion of the condenser lens 13 is attached to the surface (side surface) of the spacer 21. Then, the condensing lens 13 is fixed by inserting the sponge-like member 22 between the condensing lens 13 and the right side wall 26b.

As described above, according to the present embodiment, even if three types of polarization beam splitters having different shaping ratios of shaping surfaces are used, one optical block can be used and they can be shared. . Moreover, the range of selection of the semiconductor laser to be used is further expanded. In the present embodiment, an optical block that can be applied to a polarization beam splitter having three different shaping surfaces has been described. However, by using various spacers having different thicknesses, it is possible to obtain a polarization beam having three or more different shaping surfaces. It can correspond to a beam splitter. (Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIG.

In the present embodiment, the condenser lens fixing portion 36a is not the V groove but the W groove. The fixing of the condenser lens 13 is the same as that of the first embodiment, and thus the description thereof is omitted. Also in this embodiment, one optical block can be shared. (Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to FIG.

In this embodiment, the condenser lens 13 having a cylindrical outer shape is held by the lens frame 44 having a rectangular outer shape, and the side surface of the lens frame 44 is provided with the side wall 46 of the condenser lens fixing portion 46.
It abuts against a or the side wall 46b and is biased and fixed by the leaf spring 47. The fixing to the condensing lens fixing portion 46 is the same as that of the first embodiment except that the condensing lens 13 is fixed via the lens frame 44, and the description thereof will be omitted.

Also in this embodiment, one optical block can be shared. In this embodiment, the lens frame has a rectangular outer shape, but may have a cylindrical outer shape. (Fifth Embodiment) Next, a fifth embodiment of the present invention will be described with reference to FIG.

In this embodiment, as in the fourth embodiment, the condenser lens 13 is attached to the optical block 55 (the bottom surface 55a) while being held by the lens frame 54. 54 has a length such that it can be fitted between the two side walls 56a, 56b of the condenser lens fixing portion 56, and the portion (hole) 54a for holding the condenser lens 13 is formed only on one end side. It differs from the fourth embodiment in that

As described above, the condenser lens holding portion 54a of the lens frame 54 is formed only on one end side of the lens frame 54, but the holding portion 54a is located on the left side of the condenser lens fixing portion 56. When fixed so that the holding portion 54a is located on the side wall 56a side (as indicated by the solid line in FIG. 8),
The reflected light from the shaping surface having a small shaping ratio is incident on the condenser lens 13 held by the lens frame 54, and the lens frame 54 is reversed (as indicated by the dotted line in FIG. 8) to the right side. When the condenser portion is fixed to the condenser lens fixing portion 56 such that the holder portion 54a is located on the side wall side 56b, the reflected light from the shaping surface having a large shaping ratio is incident on the condenser lens 13 held by the lens frame 54. The position is decided so that it may be done.

Therefore, whether the lens frame 54 is to be reversed between the case of using the polarization beam splitter having a shaping surface with a small shaping ratio and the case of using the polarization beam splitter having a shaping surface with a large shaping ratio. Can be dealt with. The position adjustment of the condenser lens in the optical axis direction is the same as that in each of the above-described embodiments, and thus the description thereof is omitted.

In each of the above embodiments, the condenser lens fixing portion may be integrally formed with the optical block, or the condenser lens fixing portion may be separately manufactured and then adhered and fixed to the optical block. . Further, in each of the above-described embodiments, the description is made as the separation optical system (separation into the movable optical block 16 and the fixed optical block 15), but the present invention is not limited to this. The condenser lens fixing portion may be provided on the optical block of the integrated optical system in which the semiconductor laser, the polarization beam splitter, the objective lens, and the light detection element are mounted on one optical block.

Further, in each of the above-mentioned embodiments, an optical system intended for a magneto-optical recording medium has been described, but the present invention is not limited to this. The present invention can be applied to an optical system of an information recording / reproducing apparatus that performs at least one of reproduction and recording of information on an optical recording medium such as a phase change recording medium and a perforated type optical recording medium such as a compact disc.

Further, in each of the above-mentioned embodiments, the first surface of the polarization beam splitter acts as both a splitting means for splitting the light from the semiconductor laser and a shaping means for shaping the cross-sectional shape of the light from the semiconductor laser. However, the present invention is not only applied to an optical system using a polarization beam splitter having a surface that also serves as both means in this manner, and in short, when using a plurality of shaping surfaces having different shaping ratios, Since it is applied to the optical system, it does not matter whether or not both the above-mentioned means are combined.

[0042]

As described above, according to the present invention,
By using a plurality of semiconductor lasers that emit light with different divergence angles, the optical blocks can be shared even if the layout of the optical system is changed. Therefore, (1) the selection range of the semiconductor lasers to be used can be increased. (2) It becomes possible to suppress the manufacturing cost of the optical block to a low level.

[Brief description of drawings]

FIG. 1 is a plan view of the vicinity of a condenser lens fixing portion according to a first embodiment of the present invention.

FIG. 2 is a side view of respective condenser lens fixing portions when the polarization beam splitters 31 and 32 of the first embodiment are used.

FIG. 3A is a plan view of a printed circuit board holding a photodetector, and FIG. 3B is a polarization beam splitter 3;
1 shows a printed circuit board attached to the optical block 15 when the optical beam No. 1 is used, and FIG.
It is a figure which shows the printed circuit board attached to the optical block 15 when 2 is used.

FIG. 4 shows polarization beam splitters 31 and 3
It is a figure which shows the position adjustment at the time of attaching 2 to the optical block 15.

FIG. 5 is a side view of a condenser lens fixing portion according to a second embodiment of the present invention.

FIG. 6 is a side view of a condenser lens fixing portion according to a third embodiment of the present invention.

FIG. 7 is a side view of a condenser lens fixing portion according to a fourth embodiment of the present invention.

FIG. 8 is a side view of a condenser lens fixing portion according to a fifth embodiment of the present invention.

FIG. 9 is a diagram showing an optical system of Conventional Example 1.

FIG. 10 is a diagram showing an optical system of Conventional Example 2.

FIG. 11 is a diagram showing an optical system of Conventional Example 3.

FIG. 12 is a plan view and a side view showing fixing of a conventional condenser lens 13.

FIG. 13 is a diagram showing trajectories of light rays when the polarization beam splitters 31 and 32 are used.

FIG. 14A shows a polarization beam splitter 3
FIG. 14B is a diagram showing an optical system when the polarization beam splitter 32 is used, and FIG.

[Explanation of symbols]

 1 Semiconductor Laser 2 Collimating Lens 3 Polarizing Beam Splitter 4 Objective Lens 5 Magneto-Optical Recording Medium 6 Photodetection Element 7 1/4 Wave Plate 8 Condensing Lens 9 Beam Splitter 10, 11 Photodetecting Element 13 Condensing Lens 14 Standing Mirror 15 Fixed optical block 16 Condensing lens fixing part 17 Leaf spring 18 Movable optical block 19 Printed circuit board 21 Spacer 22 Sponge 25 Fixed optical block 26 Condensing lens fixing part 31, 32 Polarization beam splitter 35 Fixed optical block 36 Condensing lens fixing part 40 Adjusting pin for adjusting jig for condensing lens 41 Adjusting jig for polarizing beam splitter 31 42 Adjusting pin for adjusting jig for condensing lens 44 Lens frame 45 Fixed optical block 46 Condensing lens fixing part 47 Leaf spring 51 Polarized light Adjustment jig for beam splitter 32 5 3 Adjustment pin 54 Lens frame 55 Fixed optical block 56 Condenser lens fixing part

Claims (3)

[Claims] 1. A semiconductor laser that emits light, a shaping means that shapes the cross-sectional shape of the light from the semiconductor laser, a splitting means that splits the light shaped by the shaping means into two lights, and the splitting. A condensing lens that condenses one of the lights divided by the means, a photodetector element that receives the light condensed by the condensing means, the semiconductor laser, a shaping means, a dividing means, a condensing lens,
In an information recording / reproducing apparatus having an optical block that fixes a light detection element, the optical block has fixing means that fixes the condenser lens, and the fixing means fixes the condenser lens to the condenser lens. An information recording / reproducing apparatus having a first contact surface and a second contact surface for positioning at a first position and a position different from the first position in a direction orthogonal to the optical axis. 2. The first and second contact surfaces of the fixing means contact the side surface of the condenser lens which is not the lens surface,
The lens is positioned at the first position when contacting the first contact surface, and at a second position different from the first position when contacting the second contact surface. The information recording / reproducing apparatus according to claim 1, wherein 3. The first and second contact surfaces of the fixing means contact the side surface of a lens frame holding the condenser lens, and when the lens contacts the first contact surface. The information recording / reproducing apparatus according to claim 1, wherein the information recording / reproducing apparatus is positioned at the first position at a second position different from the first position when abutting on the second abutting surface.