JPH10334472A - Optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup of high reliability capable of exactly recording information and exactly reproducing recorded information even for the change of ambient temperature. SOLUTION: A hollow part is provided so that an optical path about an optical axis O, being the central axis of a lens frame 24, is formed, the diameter of one side of an opening end is expanded so as to become orthogonal to the optical axis O, an abutting surface 24b for positioning is rotary symmetrically provided in a ring-like manner to the optical axis O, one lens surface 3b of a collimator lens 3 whose radius of curvature is larger is stuck/fixed by coating the abutting surface 24b with adhesive 16 and the surface is held so that a air gap 25 is formed over the whole circumference between the outer peripheral face 3a of the collimator lens 3 and the inner peripheral face 24a of the lens frame 24. Consequently even when the lens frame 24 is thermally deformed by the change of ambient temp., the force exerted on the collimator lens 3 is cancelled to each other on the symmetric positions so that the influence for making the collimator lens 3 eccentric due to the ambient temp. is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical pickup for recording or reproducing information on an optical information recording medium such as an optical card and an optical disk.

[0002]

2. Description of the Related Art In an optical pickup for optically recording or reproducing information on an optical recording medium such as an optical card or an optical disk (hereinafter simply referred to as a recording medium), information is accurately recorded on the recording medium. In order to accurately reproduce recorded information, it is necessary to narrow down light as a minute spot on a recording medium, and to accurately follow the spot on a track to be recorded or reproduced.

For this reason, a focus error signal and a track error signal are detected based on the reflected light from the recording medium, and focus control and tracking control of the spot are performed.

Further, in order to perform the information recording / reproducing operation at a high speed, a device for recording / reproducing information on / from an optical disk uses an optical pickup of a two light source type in which a recording / reproducing light source and an erasing light source are separately provided. 2. Description of the Related Art In a device for recording and reproducing information on an optical card, a two-light source optical pickup in which a recording light source and a reproduction light source are separated is used.

[0005] As such an optical pickup, there is an optical pickup of a two light source system as described in, for example, JP-A-4-82028. FIG. 5 shows a configuration of an optical system of an optical pickup of a two light source type used in an apparatus for recording and reproducing information on an optical card.

In FIG. 5, light emitted from the reproducing semiconductor laser 1 so as to spread is collimated by a collimating lens 3.
After being converted into a parallel light beam by the diffraction grating 5, the light beam is diffracted by the diffraction grating 5 into three light beams of zero-order light and ± first-order diffracted light, and transmits through the dielectric multilayer film formed on the joint surface of the beam splitter 6.

On the other hand, the light emitted to spread from the recording semiconductor laser 2 is converted into a parallel light beam by the collimator lens 4 and reflected by the dielectric multilayer film formed on the joint surface of the beam splitter 6. The light is combined with three light beams from the semiconductor laser 1 for reproduction.

These light beams that have exited the beam splitter 6 have an elliptical light quantity distribution, are incident on a shaping prism 7, are converted into circular light quantity distributions, and are further separated into a forward path and a return path. The light passes through the splitter 8 and the quarter-wave plate 9 and is condensed by an objective lens 10 as light condensing means to form four spots on the optical card 11 corresponding to the respective light beams.

FIG. 6 shows spot positions on the optical card 11. On the optical card 11, there are formed a recording track 11a for recording information as a row of pits 11c, and a guide track 11b for enabling the spot to scan the center of the recording track 11a correctly.

In the spots formed by the three light beams from the reproducing semiconductor laser 1, ± 1st-order diffracted lights by the diffraction grating 5 are the spots S1 and S3, and the 0th-order diffracted light is the spot S2. The spot due to the light beam from the recording semiconductor laser 2 is a spot S4.

The relative positions of these spots can be obtained by adjusting the relative angle between the optical axis of the light beam from the semiconductor laser 1 for reproduction and the optical axis of the light beam from the semiconductor laser 2 for recording.

More specifically, the position of the reproducing semiconductor laser 1 and the collimating lens 3 is adjusted in a plane perpendicular to the optical axis, or the position of the recording semiconductor laser 2 and the collimating lens 4 is adjusted in a plane perpendicular to the optical axis. The position of the spot is adjusted by adjustment or by adjusting the angle of the reflection surface of the beam splitter 6.

Light reflected from each spot on the optical card 11 passes through the objective lens 10 again, passes through the quarter-wave plate 9 and is reflected by the beam splitter 8 for separating the reciprocating path. The light is converged in a form given an aberration and enters the photodetector 13.

The photodetector 13 includes a light receiving element 13 as shown in FIG.
a, 13b, and 13c, and the light reflected from the three spots S1, S2, and S3 by the reproducing semiconductor laser 1 is received by the light receiving elements 13a, 13b, and 13c as S1 ', S2', and S3 ', respectively. You.

The tracking control is performed by the light receiving signals of the light receiving elements 13a and 13c, and the focus control and the reproduction signal detection are performed by the light receiving signal of the light receiving element 13b which is a four-divided element. Focus control is a so-called astigmatism method,
The property that the light given astigmatism by the toric lens 12 changes its shape in the diagonal direction of the quadrants A, B, C, and D according to the direction of the shift of the spot on the optical card 11 from the focused state. This is a method that uses.

In order to perform the focus control correctly, the difference signal (A + D)-(B + C) in the two diagonal directions of the quadrants A, B, C, and D during focusing is 0, and the upper and lower difference signals (A + B)-(C + D), left / right difference signal (A + C)-
The position of the photodetector 13 is adjusted so that (B + D) becomes 0 (the outputs of the quadrants A, B, C, and D are also A, B, and C, respectively, for simplicity). , D).

FIG. 8 shows a structure for holding a collimator lens in such an optical pickup and a partially enlarged view thereof.
FIG. 8A is a front view, and FIG. 8B is a cross-sectional view, a part of which is shown in an enlarged manner. FIG. 8 shows the holding structure of the collimator lens 3, but the collimator lens 4 has the same structure.

The diameter of the inner wall 14a of the lens frame 14 facing the outer peripheral portion of the collimating lens 3 is
When the lens is dropped, the eccentric amount of the collimating lens 3 with respect to the lens frame 14 is suppressed to several tens μm and the lens frame 1
The diameter of the collimating lens 3 is made several tens μm larger than the diameter of the outer circumference 3 a of the collimating lens 3 so that the collimating lens 3 can be dropped even when including the dimensional tolerance of the collimating lens 3. The collimating lens 3 is fixed to the lens frame 14 by filling an adhesive 16 in a gap with the outer periphery 3 a and curing the adhesive 16.

More specifically, when the collimating lens 3 and the lens frame 14 are bonded, an adhesive 16 is applied to the outer periphery 3a of the collimating lens 3 and then dropped into the lens frame 14, thereby forming the outer periphery 3a of the collimating lens 3. And lens frame 1
4, a layer of the adhesive 16 is formed in the gap between the inner walls 14a.

[0020]

However, in the structure for holding the collimating lens 3 or 4 of the conventional optical pickup, the collimating lens 3 is bonded to the inner wall 14a of the lens frame 14 in a state where the collimating lens 3 is biased as shown in FIG. Therefore, it has the following problems.

FIGS. 9A and 9B are diagrams for explaining the problems in the conventional optical pickup, and schematically show the deviation between the center of the collimator lens and the center of the lens frame due to a change in the ambient temperature. is there.

FIG. 9A shows a state at normal temperature in which the collimating lens 3 is biased in the direction of the point E so as to be in contact with the inner wall 14a of the lens frame 14. On the other hand, FIG. 9B shows a state at a high temperature when the ambient temperature increases.

At a high temperature, the entire lens frame 14 expands as indicated by an arrow, and for example, as shown in FIG. 9B, the inner wall 14a of the lens frame 14 is approximately δ1 in the radial direction from the state at normal temperature. It expands, but the collimating lens 3
Has a linear expansion coefficient smaller than that of the lens frame 14 by about one digit, so that the expansion amount is smaller than that of the lens frame 14.

At this time, the adhesive 16 is softer than the collimating lens 3 and the lens frame 14 and can act as an elastic body to absorb the distortion due to expansion. , The amount of strain absorption is small.

As a result, the collimating lens 3 moves so as to be drawn in the direction of the point E as the lens frame 14 expands. Therefore, the deviation between the center C1 of the collimating lens and the center C2 of the lens frame is δ0 at room temperature as shown in FIG. 9A, but increases to δ0 + δ1 at high temperature.

As described above, in the conventional structure for holding the collimating lens of the optical pickup, the inner wall 14a of the lens frame 14 is formed.
When the ambient temperature changes, the collimating lens 3 tends to adhere to the lens frame 14 in a biased state.
Since the semiconductor laser 1 and the collimator lens 3 are displaced in a direction perpendicular to the optical axis due to the displacement of the collimator lens 2 and the center C1 of the collimator lens, the optical axis previously adjusted may be inclined.

For this reason, in the optical pickup of the two light source system, a relative displacement occurs between the spot positions of the two light sources due to a change in the ambient temperature. However, since the spot by the other light source is shifted from the center of the track, there is a problem that the function of accurately recording information and accurately reproducing the recorded information is deteriorated.

Also in the single light source type optical pickup, the position of the light incident on the photodetector is shifted due to the inclination of the optical axis, so that the adjustment of the photodetector is relatively caused, and the focus control can be performed correctly. There is a problem that the function of accurately recording information and accurately reproducing the recorded information is deteriorated.

(Object of the Invention) The present invention has been made in view of the above points, and improves reliability against a change in ambient temperature, records information accurately, and reproduces recorded information accurately. It is an object of the present invention to provide an optical pickup that can perform the above-mentioned operations.

[0030]

To achieve the above object, an optical pickup according to the present invention comprises a semiconductor laser, a collimating lens for converting light from the semiconductor laser into a parallel light beam, and a lens for holding the collimating lens. With a frame, while providing a gap over the entire circumference between the outer peripheral surface of the collimating lens and the inner peripheral surface of the lens frame,
By bonding the ring-shaped surface inside the lens frame and the lens surface of the collimating lens for positioning the collimating lens in the optical axis direction, the ambient temperature changes and the lens frame thermally expands or contracts. Even if a force acts on the collimating lens via the adhesive portion, the forces cancel each other out at symmetrical positions in the ring-shaped portion, thereby preventing eccentric movement.

[0031]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIGS. 1 and 2 relate to a first embodiment of the present invention, and FIG. 1 is an enlarged view of a holding structure of a collimating lens in an optical pickup according to the first embodiment and a partial enlarged view thereof. FIG. 2 shows a state in which a collimating lens is bonded and fixed to a lens frame. FIG. 1A is a front view of the holding structure of the collimating lens viewed from the optical axis direction.
(B) is a cross-sectional view, and an enlarged view of a part of the circle in FIG.

The configuration of the optical system of the optical pickup according to the present invention is the same as that shown in FIG. 5, and a description thereof will be omitted. FIG. 1 shows the holding structure of the collimating lens 3, but the collimating lens 4 has the same structure.

As shown in FIG. 1, the holding structure of the collimating lens 3 in the first embodiment
Is substantially cylindrical, and has a hollow portion in which an optical path having the central axis as the optical axis O is formed.

One opening end (opening end on the right side in FIG. 1B) of the hollow portion of the lens frame 24 is tapered so that the diameter thereof is increased so that the reproducing semiconductor laser 1 is mounted. The diameter of the open end is also enlarged to form a short cylindrical inner peripheral surface 24a.
Are formed, and the collimating lens 3 is housed and held inside the inner peripheral surface 24a.

The radius of the inner peripheral surface is slightly larger than the radius of the outer peripheral surface 3a so that a gap 25 is formed over the entire periphery between the inner peripheral surface 24a and the short cylindrical outer peripheral surface 3a of the collimator lens 3. doing.

In this embodiment, when the collimating lens 3 is held by the lens frame 24, the collimating lens 3
In order to perform positioning in the optical axis direction, an adhesive 16 is applied to a ring-shaped abutting surface 24b which is rotationally symmetric with respect to the optical axis O on a surface orthogonal to the optical axis O, and the abutting surface 24b is collimated. The lens 3 has a structure in which one lens surface 3b is abutted and adhered and fixed by the adhesive 16 to be held.

The ring-shaped abutting surface 24b
Although the outer radius may be increased to the inner peripheral surface 24a of the lens frame 24, as shown in FIG. 1, by making the radius smaller than the outer radius 3a of the collimating lens 3, the adhesive 16 Is prevented from protruding between the inner peripheral surface 24a and the outer peripheral surface 3a of the collimating lens 3, and even if the collimating lens 3 is fixed in an eccentric state, the distance between the lens surface 3b and the abutting surface 24b is reduced. Adhesive 1
6 has almost no influence on the holding state (in contrast, in the conventional example, the state of adhesion and fixation is directly greatly affected by eccentricity).

The gap 25 provided over the entire circumference between the inner peripheral surface 24a of the lens frame 24 and the outer peripheral surface 3a of the collimator lens 3 prevents thermal deformation of the lens frame 24 due to a change in ambient temperature. This prevents direct action on the outer peripheral surface 3a.

Further, a lens frame 24 is provided on the optical pickup body.
There is also an effect of preventing the deformation of the lens frame 24 that occurs when fixing the outer surface 3a of the collimator lens 3 from directly acting.

When an attempt is made to secure a larger gap 25, the effect of suppressing the center deviation between the collimator lens 3 and the lens frame 24 becomes smaller, but this is dealt with by changing the bonding method.

For example, a structure for holding the outer peripheral surface 3a of the collimating lens 3 and a structure that can be fitted to the inner peripheral surface of the lens frame 24 when bonding and fixing as in a specific example of the bonding method shown in FIG. The center position of the lens frame 24 and the collimating lens 3 is adjusted by using the bonding jig 27 having the above, and the displacement of the center between the lens frame 24 and the collimating lens 3 can be suppressed to about several tens of microns as in the related art.

In the bonding operation, first, the collimating lens 3 is mounted on the bonding jig 27. Next, the collimating lens 3 is fitted together with the bonding jig 27 in the direction of the arrow in FIG. 2 to the lens frame 24 in which the adhesive 16 has been applied to the ring-shaped portion of the abutting surface 24b of the collimating lens 3 in advance. The lens surface 3b of the collimator lens 3 is held in contact with the contact surface 24b of the lens frame 24, and after the adhesive 16 is cured, the bonding jig 27 is pulled out, and the holding state as shown in FIG. 1 is obtained. .

The adhesive 16 is applied to a ring-shaped abutting surface 24b provided in the lens frame 24 for positioning the collimating lens 3 in the optical axis direction, and the collimating lens 3 is bonded to the ring-shaped abutting surface 24b. The force that causes the collimating lens 3 to move in the radial direction through the adhesive 16 due to the thermal deformation of the lens frame 24 due to the change in the distance can be radially dispersed to cancel each other.

Further, as shown in FIG. 1, in the present embodiment, the thickness of the adhesive layer is made substantially uniform by using the lens surface 3b having the larger radius of curvature of the collimating lens 3 as the adhesive surface, so that the temperature of the ambient temperature is reduced. Adhesive strength sufficient to receive the force generated by the thermal deformation of the lens frame 24 due to the change can be secured in a small area. The amount of inclination of the optical axis O of the collimating lens 3 can be reduced.

According to the present embodiment having such a configuration,
Instead of adhesively fixing the outer peripheral surface 3a of the collimating lens 3 in the conventional example, the lens surface 3b is adhesively fixed to a ring-shaped abutting surface 24b, and a gap 25 is formed around the entire outer peripheral surface 3a.
Is fixed so that

Accordingly, even if the ambient temperature changes and the lens frame 24 thermally expands, the collimating lens 3 fixed to the lens frame 24 is bonded at a concentric ring-shaped portion at an equal distance from the center of the lens frame 24. Since the collimating lens 3 is fixed via the agent 16, the adhesive portions of the collimating lens 3 receive a force outward in the radial direction due to the thermal expansion of the lens frame 24. They cancel each other out with almost equal forces in the opposite direction. Therefore, the eccentric movement as in the conventional example can be almost eliminated. In the case of thermal contraction, the eccentric movement of the collimating lens 3 can be almost eliminated.

In this case, even if the collimating lens 3 is eccentrically fixed, the outer peripheral surface 3a of the collimating lens 3
Since the air gap 25 is formed on the entire circumference of the collimator lens 3, it is possible to prevent the thermal deformation of the lens frame 24 due to a change in the ambient temperature from directly acting on the outer peripheral surface 3a of the collimator lens 3. Therefore, the inclination of the optical axis O can be substantially eliminated or reduced.

According to the optical pickup of this embodiment using the collimating lens holding structure, when optically recording or reproducing on a recording medium such as the optical card 11, the tracking control is performed and the recorded information is reproduced. It is possible to prevent the spot position from being relatively shifted at an ambient temperature, and to prevent the spot position for recording from being relatively shifted at an ambient temperature. In other words, even if the ambient temperature changes, accurate tracking control and recording and reproduction become possible,
A highly reliable optical pickup can be realized.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3A is a front view showing a collimating lens holding structure according to a second embodiment of the present invention, and FIG. 3B is a sectional view thereof.

In the first embodiment, the collimating lens 3
The lens surface 3b having the larger radius of curvature of the two lens surfaces is connected to the ring-shaped abutting surface 2 of the lens frame 24.
Although the collimating lens 3 is held by being fixed to the adhesive 4b with an adhesive 16, in the present embodiment, a collimating lens having a flat surface 3c outside the lens surface 3b in the radial direction, such as a glass molded lens, is used. In the lens 3, as shown in FIG. 3, by bonding the adhesive 16 to the lens frame 24 on the flat surface 3 c, the adhesive strength can be secured in a smaller area, and the inclination of the optical axis O of the collimating lens 3 occurs. The amount is kept small.

In the present embodiment, the lens frame 24 holding the collimating lens 3 is partially cut out of its outer peripheral surface, and is a plane parallel to the optical axis O (hereinafter, referred to as a D-cut plane). 28 are provided.

The contact area between the optical pickup body and the lens frame 24 increases due to the D-cut surface 28, and the lens frame 2
Since the deformation of the lens frame 24 when the lens frame 4 is fixed to the optical pickup main body can be reduced, the thermal deformation of the lens frame 24 is less likely to be biased when the ambient temperature changes, thus preventing the bias due to the thermal deformation. Effect can be enhanced.

Further, in this embodiment, as shown in FIG. 3, the diffraction grating 5 is bonded to the end face of the lens frame 24 with the D-cut surface 28 as a reference, and is fixed to the lens frame 24.

An optical component, such as a diffraction grating 5 or a quarter-wave plate, which needs to be rotated and positioned around the optical axis with reference to the D-cut surface 28, is adhered to the end surface of the lens frame 24, so that the optical pickup main body is formed. Rotational positioning during assembly can be facilitated.

When the diffraction grating 5 is adhered to the lens frame 24, the grating surface 5a is directed toward the lens frame 24 to prevent the grating surface from being stained and to facilitate the cleaning operation when the stain is attached. Can be.

According to the present embodiment, in addition to the effects of the first embodiment, since the lens is fixed by the flat surface 3c outside the lens surface 3b, the positioning abutment surface 24b
The accuracy of positioning with the lens can be improved, and the lens can be fixed with the lens surface side having a small radius of curvature inside.

Further, a D-cut surface 28 is provided so that the diffraction grating 5
By positioning and fixing the optical components such as the above and integrating them, there is an effect that the positioning when assembling to the optical pickup main body can be facilitated.

For example, as a modification of the second embodiment, the adhesive 1 is applied to the entire periphery of the ring-shaped abutting surface 24b.
Instead of fixing the collimating lens 3 at 6, the adhesive 16 is applied to a plurality of positions or portions that are point-symmetric with respect to the optical axis O, for example, as shown in FIG. May be.

That is, the flat surface 3c of the collimating lens 3 (not the flat surface 3c when applied to the first embodiment) is formed at a part of the ring-shaped abutting surface 24b, not at the entire circumference. Instead, a structure in which the lens surface 3b) is held with an adhesive may be used.

In this case, the second embodiment has substantially the same effects as those of the second embodiment, and also has the following effects. Since air can flow in and out of the portion where the adhesive 16 is not applied, the temperature of the entire collimating lens 3 does not become uniform and the temperature of a part of the collimating lens 3 locally increases.
Ambient air can easily move from one lens surface to the other lens surface, and can be easily set to a uniform temperature.

In order to make it easier for air to flow in and out, a groove in the radial direction (for example, the optical axis O is formed on a portion of the ring-shaped abutment surface 24b where the adhesive 16 is not applied in FIG. 4).
Are provided so as to form a communication path (for increasing the inflow and outflow of air to make the ambient temperature uniform) connecting the hollow portion serving as the optical path and the gap 25. May be. This modification can be applied to a case where a part of the outer peripheral portion of the collimator lens 3 is cut out.

The present invention is not limited to the two-light-source optical pickup shown in FIG. 5, but can be applied to a one-light-source optical pickup. Also in this case, the occurrence of the inclination of the optical axis O can be suppressed with respect to the temperature change, so that the position shift of the light incident on the photodetector can be suppressed, and the functions such as the focus control can be hardly changed. The function of recording information on the media and accurately reproducing the recorded information can be maintained.

The present invention can be applied not only to the optical pickup of the one light source system or the two light source system for recording or reproducing the optical card 11, but also to the optical pickup for recording or reproducing a disk-shaped recording medium.

It should be noted that embodiments formed by partially combining the above-described embodiments and the like also belong to the present invention. The present invention described above includes the contents of the claims described in the following supplementary notes.

[Supplementary Notes] In an optical pickup comprising a semiconductor laser, a collimating lens for converting light from the semiconductor laser into a parallel light beam, and a lens frame for holding the collimating lens, an outer peripheral surface of the collimating lens and an inner peripheral surface of the lens frame And a collimating lens holding structure for bonding a ring-shaped surface inside the lens frame for positioning the collimating lens in the optical axis direction and a lens surface of the collimating lens is provided. Optical pickup.

2. 2. The optical pickup according to claim 1, wherein the collimating lens holding structure is a structure in which a ring-shaped surface inside the lens frame is bonded to a surface having a maximum radius of curvature among lens surfaces of the collimating lens.

3. 2. The optical pickup according to claim 1, wherein the collimating lens holding structure adheres and fixes the lens surface of the collimating lens at a portion symmetrical with respect to a center of a ring-shaped surface inside the lens frame.

4. In an optical pickup comprising a semiconductor laser, a collimating lens for converting light from the semiconductor laser into a parallel light beam, and a lens frame for holding the collimating lens, an outer peripheral surface of the collimating lens and an inner peripheral surface of the lens frame A collimator that provides an air gap between the collimator lens and bonds a ring-shaped surface inside the lens frame for positioning the collimator lens in the optical axis direction and a flat surface provided radially outside the lens surface of the collimator lens. An optical pickup comprising a lens holding structure.

5. In an optical pickup comprising a semiconductor laser, a collimating lens for converting light from the semiconductor laser into a parallel light beam, and a lens frame for holding the collimating lens, an outer peripheral surface of the collimating lens and an inner peripheral surface of the lens frame And a collimating lens holding structure for bonding and fixing the lens surface of the collimating lens via an adhesive at a plurality of positions symmetrical at an equal distance from the center of the lens frame. Optical pickup.

[0070]

As described above, according to the present invention, an optical pickup including a semiconductor laser, a collimator lens for converting light from the semiconductor laser into a parallel light beam, and a lens frame holding the collimator lens At
A gap is provided between the outer peripheral surface of the collimating lens and the inner peripheral surface of the lens frame, and a ring-shaped surface inside the lens frame and a lens surface of the collimating lens for positioning the collimating lens in the optical axis direction. Since the collimating lens holding structure that adheres the lens is provided, even if the surrounding temperature changes and the lens frame thermally expands or contracts, and the force acts on the collimating lens via the bonding portion, the symmetry at the ring-shaped portion is obtained. , The forces cancel each other out at the positions, and the occurrence of eccentric movement can be prevented. Therefore, it is possible to suppress the occurrence of the deviation of the optical axis, and it is possible to realize a highly reliable optical pickup that records information accurately and reproduces the recorded information accurately even when the ambient temperature changes.

[Brief description of the drawings]

FIG. 1 is a diagram showing a holding structure of a collimating lens according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a state in which a collimating lens is bonded and fixed to a lens frame with a bonding jig.

FIG. 3 is a diagram illustrating a collimating lens holding structure according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a portion of a lens frame to which an adhesive is applied according to a modification of the second embodiment.

FIG. 5 is a diagram showing a configuration of an optical system of an optical pickup of a two light source type used in an apparatus for recording and reproducing information on an optical card.

FIG. 6 is a diagram showing spot positions on an optical card.

FIG. 7 illustrates a configuration of a photodetector.

FIG. 8 is a diagram showing a holding structure of a collimator lens in a conventional example and a partially enlarged view thereof.

FIG. 9 is a diagram illustrating that a problem occurs due to a temperature change when a collimator lens in a conventional example is eccentrically mounted.

[Explanation of symbols]

 Reference numerals 1, 2, semiconductor laser 3, 4, collimating lens 3a, outer peripheral surface 3b, lens surface 3c, flat surface 5, diffraction grating 6, 8, beam splitter 7, shaping prism 9, quarter-wave plate 10, objective lens 11 ... Optical card 12 ... Toric lens 13 ... Photodetector 16 ... Adhesive 24 ... Lens frame 24a ... Inner peripheral surface 24b ... Abutment surface 25 ... Void 27 ... Adhesive jig 28 ... D cut surface

Claims (3)

[Claims] 1. An optical pickup comprising a semiconductor laser, a collimator lens for converting light from the semiconductor laser into a parallel light beam, and a lens frame for holding the collimator lens, wherein an outer peripheral surface of the collimator lens and the lens A gap is provided between the inner peripheral surfaces of the frame, and a collimating lens holding structure for bonding a ring-shaped surface inside the lens frame for positioning the collimating lens in the optical axis direction and a lens surface of the collimating lens is provided. An optical pickup characterized in that: 2. The collimating lens holding structure according to claim 1, wherein the ring-shaped surface inside the lens frame and a surface having the largest radius of curvature among the lens surfaces of the collimating lens are bonded. 1. The optical pickup according to 1. 3. An optical pickup comprising a semiconductor laser, a collimating lens for converting light from the semiconductor laser into a parallel light beam, and a lens frame for holding the collimating lens, wherein an outer peripheral surface of the collimating lens and the lens A flat surface is provided between the inner peripheral surface of the frame and a ring-shaped surface inside the lens frame for positioning the collimating lens in the optical axis direction and a radially outer surface of the lens surface of the collimating lens. An optical pickup characterized by having a collimating lens holding structure for adhering the lens.