JPH04243033A - Optical pickup device - Google Patents

Abstract

PURPOSE:To improve the accuracy of an optical system. CONSTITUTION:The end of a reflection surface 4a of a reflection prism 4 which deflects the optical axis of a laser beam is connected to an adhesive surface 4b via a connecting surface 4c. On the other hand, a recessed part 12 is formed in the mounting position of the reflection prism 4 of a housing 11 and the adhesive surface 4b is fixed by an adhesive 13 to the base of this recessed part 12. Then, the connecting part of the adhesive surface 4b and the reflection surface 4a is formed thick and the rigidity of this part improves and, therefore, the deformation of the optical parts is prevented and the accuracy of the optical surface improves.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention focuses a laser beam outputted from a semiconductor laser element onto a recording medium by guiding it to an objective lens to narrow it down to a minute spot, and also directs the reflected light from the recording medium to the same objective lens. The present invention relates to an optical pickup device in which light enters through a lens.

0002

2. Description of the Related Art Generally, a storage device such as an optical disk device or a magneto-optical disk device (hereinafter collectively referred to as an optical disk device) is equipped with an optical pickup device for recording/reproducing data.

[0003] In this optical pickup device, the output light of a semiconductor laser element used as a light source is converted into a parallel laser beam, and the laser beam is guided to an objective lens and focused onto a recording medium after narrowing it down to a minute spot. At the same time, the reflected light from the recording medium is incident through the same objective lens, and the incident light is optically processed and guided to the light receiving element to obtain a reproduction signal, as well as a focusing error signal and a tracking error signal. There is.

Now, in order to narrow down the spot diameter of the laser beam focused on the storage medium to a very small diameter of about 1 μm using an optical pickup device, the performance of the optical system of the optical pickup device must have so-called diffraction-limited performance. Must be. In this way, in order for an optical system to have diffraction-limited performance, it is necessary to increase the precision of the optical surfaces of the optical components that make up the optical system, and to minimize the wavefront aberration of the optical surfaces. be.

On the other hand, when fixing each optical component of an optical pickup device to a housing, a holding member base member, etc., adhesive is usually used to fix the optical components because the interior of the housing is narrow.

Furthermore, in the optical pickup device, as an optical component for deflecting a laser beam, a so-called triangular prism P having a triangular prism shape is used, as shown in FIG. 6, for example. This triangular prism P has a simple shape, is small and lightweight, and has the characteristics of easily achieving angular accuracy in the deflection direction, and is used as an optical component for small optical devices such as optical pickup devices. It is widely used as

When attaching this triangular prism P to the casing A of the optical pickup device, as shown in FIG. is pressed against housing A.

[0008]

[Problems to be Solved by the Invention] However, such conventional methods have the following disadvantages.

That is, the adhesive G shrinks and expands during and after curing, and since its expansion coefficient is different from that of the triangular prism P and the housing A, external force acts on the triangular prism P and the housing A. At this time, the adhesive surface Pa and the reflective surface form an angle of 45 degrees, and since the portion where these surfaces connect is thin, the rigidity of the housing A is greater than that of the triangular prism P in that portion.

[0010] Therefore, the triangular prism P is deformed, and as a result, the optical surface of the triangular prism P curves or wraps. As a result, the wavefront aberration of the reflective surface of the triangular prism P increases, causing a decline in the performance of the optical system of the optical pickup device.

Further, in order to miniaturize the device, the triangular prism P is also formed as small as possible, and there has been a problem in that the adhesive G protruding from the adhesive surface wraps around the optical surface, deteriorating the reflection characteristics.

The present invention has been made in view of the above-mentioned circumstances, and aims to provide an optical pickup device that can improve optical characteristics by using optical components that can prevent deterioration of wavefront aberration of the optical surface. The purpose is to provide a fixation method.

[0013]

[Means for Solving the Problems] In the present invention, the reflective surface of a reflective prism that deflects the optical axis of a laser beam is connected at its end to an adhesive surface via a communication surface, and the adhesive surface is connected to a holding member. It is attached via an adhesive in a manner that it is placed on the bottom surface of a recess formed in the. Further, one end of the reflective surface is connected to the adhesive surface via a connecting surface. Further, both end faces of the reflective surface are connected to different adhesive surfaces via different connecting surfaces.

[0014]

[Operation] Therefore, the connecting portion between the adhesive surface and the reflecting surface becomes thicker, and the rigidity of that portion is improved, so deformation of the optical component is prevented and the accuracy of the optical surface is improved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an example of an optical system of an optical pickup device according to an embodiment of the present invention. Note that this optical pickup device uses a push-pull method as a tracking error detection method, and a knife edge method as a focusing error detection method.

In the figure, signal light output from a semiconductor laser device 1 is converted into parallel light by a coupling lens 2, enters a beam splitter 3, passes through the beam splitter 3, and is guided to a reflecting prism 4. The light is bent in the optical axis direction of the objective lens 5, focused by the objective lens 5, and formed into an image on the recording surface of the optical disc 6.

The reflected light from the optical disk 6 passes through the objective lens 5 and is converted into substantially parallel light, and then passes through the reflecting prism 4.
The beam is reflected by the beam splitter 3, and part or all of it is reflected by the beam splitter 3.

In this way, the reflected light from the optical disk 6 reflected by the beam splitter 3 is focused by the lens 7, and approximately half of the light beam is reflected by the splitting mirror 8 constituting the knife edge for tracking. The light is incident on a light receiving element 9 for tracking error detection whose light receiving surface is divided into two in the direction.

The remaining part of the light beam focused by the lens 7 is incident on a light receiving element 10 for focusing error detection, whose light receiving surface is divided into two by a dividing line parallel to the ridge line 8a of the splitting mirror 8. Ru.

A tracking error signal is obtained based on the difference between the light receiving signals output from the two divided light receiving surfaces of the light receiving element 9, and the tracking error signal is obtained based on the difference between the light receiving signals output from the two divided light receiving surfaces of the light receiving element 10. A focusing error signal is obtained based on the signal difference. Also, based on the sum of the light reception signals of the light receiving element 9 and the light receiving element 10, the optical disc 6
Obtain the playback signal from.

Further, the objective lens 5 is provided with an objective lens moving mechanism 11 for moving the objective lens 5 in the tracking direction and the focusing direction, and a tracking error signal or a focusing error signal is controlled by a servo control section (not shown). The objective lens moving mechanism 11 is controlled in the direction in which the value becomes zero.

Here, as shown in FIG. 2, the reflective prism 4 is provided with an adhesive surface 4b at a distance t from one end of the reflective surface 4a, and the reflective surface 4a and the adhesive surface 4
A connecting surface 4c connecting these surfaces is formed between the surfaces b.

FIG. 3 shows how the reflecting prism 4 is fixed.

In the figure, the mounting position of the reflecting prism 4 in the housing 11 has a dimension t in the plane direction of the communication surface 4c.
A recess 12 is formed with approximately the same depth as the adhesive surface 4.
The adhesive 13 is applied to the entire surface of b, and in this state, the adhesive surface 4c is pressed against the surface of the recess 12 and fixed to the housing 11.

[0026] In this way, since there is a thickness between the reflective surface 4a of the reflective prism 4 and the adhesive surface 4b corresponding to the dimension t in the surface direction of the connecting surface 4c, the rigidity of the reflective prism 4 is improved. .

On the other hand, since the concave portion 12 of the casing 11 is thinner than other parts, the casing 1 in this portion
The rigidity of No. 1 has decreased.

Therefore, when an external force is applied to the adhesive portion between the reflective prism 4 and the housing 11 due to expansion/contraction of the adhesive 13, the concave portion 12 is easily deformed, so that the reflective prism 4 is deformed. As a result, the wavefront aberration of the reflecting surface 4a of the reflecting prism 4 is suppressed from increasing.

According to experiments conducted by the present inventors, the relationship between the dimension t in the direction of the connecting surface 4c of the reflecting prism 4 and the wavefront aberration of the reflecting surface 4c was obtained as shown in the graph of FIG. It was confirmed that by increasing the size to a certain extent, the wavefront aberration of the reflecting surface 4c can be effectively suppressed.

FIG. 5 shows another example of the reflecting prism 4.

This reflective prism 4' has two adhesive surfaces 4b' and 4 located at a predetermined distance from both ends of the reflective surface 4a'.
b'' is provided, and the reflective surface 4a' and the adhesive surface 4b'
, 4b'' form connecting surfaces 4c', 4c'' that connect these surfaces, respectively.

In this case, the reflecting prism 4' is connected to the housing 11.
It can be used for the part that is adhesively fixed to both the wall surface rising from the housing 11 in the right angle direction.

By the way, in the above-mentioned embodiment, the method according to the present invention was applied when fixing the reflecting prism 4, but when fixing other optical components of the same shape, such as the split mirror 8, etc. However, the fixing method according to the present invention can also be applied.

Furthermore, the present invention can be similarly applied to optical pickup devices equipped with optical systems other than those described above.

Further, as the adhesive, a two-part mixed epoxy adhesive, an ultraviolet curing adhesive, or the like can be used.

[0036]

[Effects of the Invention] As explained above, according to the present invention,
The reflective surface of the reflective prism that deflects the optical axis of the laser beam is connected at its end to the adhesive surface via the communication surface, and the adhesive surface is arranged on the bottom surface of the recess formed in the holding member. Since it is attached via adhesive, the connecting part between the adhesive surface and the reflective surface is thicker, increasing the rigidity of that part, preventing deformation of the optical component and improving the precision of the optical surface. Get the effect.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing 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 reflecting prism.

FIG. 3 is a schematic partial cross-sectional view showing an example of a fixing mode of a reflecting prism.

FIG. 4 is a graph diagram illustrating the relationship between the surface dimensions of a connecting surface and wavefront aberration.

FIG. 5 is a schematic diagram showing another example of a reflecting prism.

FIG. 6 is a schematic diagram showing an example of a triangular prism.

FIG. 7 is a schematic partial cross-sectional view showing an example of a manner in which a triangular prism is fixed.

[Explanation of symbols]

4,4’ Reflecting prism 4a, 4a’ reflective surface 4b, 4b', 4b'' Adhesive surface 4c, 4c', 4c'' Contact surface 11 Housing 12 Recess 13 Adhesive

Claims (3)

[Claims] [Claim 1] A laser beam output from a semiconductor laser element is guided to an objective lens, narrowed down to a minute spot, and focused on a recording medium, and reflected light from the recording medium is made incident through the same objective lens. In an optical pickup device, an end of the reflective surface of a reflective prism that deflects the optical axis of a laser beam is connected to an adhesive surface via a communication surface, and the adhesive surface is connected to the bottom surface of a recess formed in a holding member. An optical pickup device characterized in that the optical pickup device is attached via an adhesive in an arranged manner. 2. The optical pickup device according to claim 1, wherein one end of the reflective surface is connected to an adhesive surface via a connecting surface. 3. The optical pickup device according to claim 1, wherein both end surfaces of the reflective surface are connected to different adhesive surfaces via different connecting surfaces.