JPH04113525A - Optical pickup - Google Patents

Abstract

PURPOSE:To miniaturize an optical pickup and to improve reliability by providing a metallic plate fixed by laser welding on an optical housing fitted to the back of a printed circuit board. CONSTITUTION:A photodetector 6 is mounted on a printed circuit board 7, and the metallic plate 11 having almost the same shape as the printed circuit board 7 is fitted to the back of this printed circuit board 7. This metallic plate 11 is adhered to an optical housing 8 by the laser welding. Since the metallic plate 11 fitted to the back of the printed circuit board 7 mounting the photodetector 6 is fixed to the optical housing 8 by using laser welding, the optical pickup can be miniaturized. Further, the number of parts can be reduced, the control accuracy of the photodetector 6 can be kept high against any environmental change, and high reliability can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical pickup used in a device for optically reading information by projecting a light spot onto an information track of an optical disk or the like on which signals are recorded at high density. be.

[Conventional technology]

2. Description of the Related Art Conventionally, when writing or reading signals on an optical disc, an optical pickup is used that has a light receiving element to receive reflected light irradiated onto the optical disc and convert it into an electrical signal.

FIG. 2 is a diagram showing the optical system of a conventional general optical pickup. In this figure, the semiconductor laser 1 is a half mirror.
2, and the reflected light is sent to the objective lens 3.
is applied to the optical disc 4 via. Then, the reflected light from the optical disk 4 is irradiated onto the half mirror 2 via the objective lens 3, and the optical signal transmitted through the half mirror 2 is transmitted to the concave lens 5.
The light is guided to the light receiving element 6 via the light receiving element 6. Here, semiconductor laser 1
and the light-receiving element 6 are in a conjugate positional relationship with respect to the half mirror 2, and by adjusting the position of the concave lens 5 in the optical axis direction, the light-receiving element 6 can be moved along the light-receiving surface in the direction perpendicular to the optical axis. Adjust its position by moving the
The light receiving element 6 is then fixed to the optical housing after position adjustment. FIG. 3 shows a printed circuit board 7 on which the light receiving element 6 is mounted, and after being attached to the printed circuit board 7, it is attached to an optical housing 8 as shown in FIG. The printed circuit board 7 is fixed to the housing 8 with screws 10 using a leaf spring 9 bent at six points as shown. Further, the back surface of the printed circuit board 7 is lined with a metal plate 11 as shown in the figure in order to match the coefficient of expansion with the metal housing 8.

Also, as shown in FIG. 5, the metal plate 1 on the back side of the printed circuit board 7
1 is fixed to the optical housing 8 with an adhesive 12.

[Problem to be solved by the invention]

However, as optical pickups become smaller and ¥R-shaped,
Not only does the space for screwing the printed circuit board on which the light receiving element is mounted become smaller, but the spot diameter on the light receiving element also becomes smaller. Therefore, the rotational moment applied when screwing the printed circuit board after adjusting the position of the light-receiving element tends to cause the light-receiving element to be slightly misaligned with respect to the spot, and this has the disadvantage that the effect cannot be ignored. In order to solve these problems, it may be possible to glue the printed circuit board to the optical housing as shown in Figure 5, but the adhesive expands and contracts due to the effects of temperature and humidity, resulting in The disadvantage was that the positional relationship changed.

The present invention has been made in view of the problems of conventional optical pickups, and a technical object thereof is to provide a small and highly reliable optical pickup.

[Means to solve the problem]

The present invention is characterized by having a light receiving element that receives light, a printed circuit board on which the light receiving element is mounted, and a metal plate attached to the back surface of the printed circuit board and fixed to the optical housing by laser welding. It is something.

[Effect]

According to the present invention having such characteristics, a metal plate is provided on the back surface of the printed circuit board on which the light receiving element is mounted, and the optical pickup is fixed by spot welding this metal plate to the housing.

〔Example〕

FIG. 1 is a perspective view of an optical pickup according to an embodiment of the present invention, and the same parts as in the conventional example described above are given the same reference numerals and detailed explanations will be omitted. In this figure, the light receiving element 6 is mounted on a printed circuit board 7. The back surface of the printed circuit board 7 is lined with a metal plate 11 having substantially the same shape as the printed circuit board 7, as shown in the figure. This metal plate 11 is then bonded to the optical housing 8 by laser welding. The metal plate 11 and the optical housing 8 are bonded together by adjusting the position of the light spot of the light-receiving element 6 and then irradiating the apex portions (A) of the metal plate 1104 with laser light as shown in FIG. For example, a YAG laser is used as the laser beam for this welding, and 20J/P, 10
It has been confirmed that when bonded under m5ec conditions, a mounting strength of 3 kg or more can be obtained. If the welding point is the apex of the metal plate 11 as shown in FIG. 1, the heat will be concentrated compared to other locations and the welding strength will be excellent. Furthermore, if the metal plate 11 is made of aluminum, the optical housing 8 is also made of aluminum die-casting, and the objects to be welded are made of the same material, more stable welding strength can be obtained since the melting temperatures are the same. Unlike when fixing with screws, when fixed by welding in this way, no stress is applied to the printed circuit board etc., and there is no positional shift during fixing, and the adjustment accuracy can be maintained at a high level. Further, since no adhesive is provided, there is only a relative positional shift between the optical housing 8 and the metal plate 11 even with respect to temperature and humidity, and high reliability can be obtained.

〔Effect of the invention〕

As described in detail above, the present invention can downsize an optical pickup by fixing an optical housing to a metal plate lined with a printed circuit board on which a light-receiving element is mounted using laser welding. In addition, the number of parts can be reduced, and the adjustment accuracy of the light receiving element can be maintained at a high level against environmental changes, resulting in high reliability.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an optical pickup according to an embodiment of the present invention, FIG. 2 is a layout diagram showing the configuration of an optical system of a general optical pickup, and FIG. 3 is a configuration of a conventional light receiving element and printed circuit board. FIGS. 4 and 5 are configuration diagrams of a conventional light-receiving element mounting portion. 6.-----1 light-receiving element, 7-------printed circuit board, 8-------optical housing, 1
1-...-metal plate. Patent applicant Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] (1) It has a light receiving element that receives light, a printed circuit board on which the light receiving element is mounted, and a metal plate attached to the back surface of the printed circuit board and fixed to the optical housing by laser welding. Optical pickup. (2) The optical pickup according to claim 1, wherein the metal plate is made of an aluminum material, and the optical housing to which the metal plate is attached is made of aluminum die-casting. (3) The optical pickup according to claim 1 or 2, wherein the metal plate has an apex portion laser welded to the optical housing.