JPS6092680A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To realize a semiconductor laser for photopickup, which can be made the size thereof smaller and can be cut down its manufacturing cost to a lower cost, by a method wherein diffraction lattices are provided at the window parts of cases, wherefrom laser lights of a semiconductor laser are released. CONSTITUTION:A diffraction lattice 12 has been provided at the window part of a case 11, wherefrom laser lights of a semiconductor laser 10 are released. Male threads have been screwed on the outside of the cylinder part of a lower case 14, whereon a semiconductor laser chip 13 has been mounted, while female threads have been screwed on the respective inside of the cylinder parts of upper cases 16 and 18, esch having a window part where a diffraction lattice 15 or a transparent glass 17 have been provided. According to this method, the number of parts items for a photopickup of 3B is reduced, thereby enabling to make the size of the titled laser smaller, to make the weight thereof lighter and to cut down the manufacturing cost of a lower cost.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to semiconductor lasers. In particular, it relates to a semicircular laser for an optical pickup.

In recent years, optical video discs and digital audio discs have been put into practical use, and their players use semiconductor lasers for optical pickup.

Various types of optical pickup using semiconductor lasers have been devised and put into practical use, but the one that is currently in widespread use is the so-called 3B (three beam) method.

Figure 1 shows the optical system of the 3B method. The way the optical components are arranged is not unique, and two examples of Cαl, (bl are given here. In Cαl, 1b1, the same numbers indicate the same parts, 1cLl will be explained. The light emitted from the soy sauce semiconductor laser 1. is converted into three beams by the diffraction grating 2. Only the pP wave passes through the polarization beam splitter /3, and the beams become parallel beams by the collimator lens 4.

The parallel light beams pass through a quarter-wave plate and become circularly polarized light), and form a spot on a disk 7 by an objective lens 6.

The light reflected by the disk 7 passes through the quarter wavelength plate again,
The light enters the polarizing beam splitter 3. At this time, the light is B
Since it is a wave, it is reflected, passes through the cylindrical lens 8, and reaches the light receiving element 9.

The arrangement of 161 is different from cLl in that the collimator lens 4 is located next to the semiconductor laser 1, but the principle is exactly the same.

The number of parts in the 3B method is 8 types as described above.

At present, for example, although the 7t% device in a digital audio disc player is relatively compact, the pickup is large and it is difficult to incorporate it into the device. Also, compared to conventional record players,
Kanashi prices are also getting higher. One of these causes is
The pickup is large in size and its cost is high.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a semiconductor laser for optical pickup that is small in size and low in cost.

FIG. 2 is a specific example of the present invention. 10 is a semiconductor laser chip, an lli case, and 12 is a diffraction grating.

Conventionally, the 12 part was a transparent glass window, but since the 3B method of optical pickup always uses a diffraction grating, the transparent glass was replaced with a diffraction grating. By doing this, the number of parts is reduced by one.

FIG. 3 shows another specific example of the present invention. 13 is a semiconductor laser chip, 14 is a lower case, and as shown in the figure, a male thread is cut in the cylindrical portion. 15 is a diffraction grating, and 16 is an upper case. The inside of the upper case 16 is internally threaded to fit the screws of the lower case 14.

17 is a transparent glass, and 18 is a lower case. In this specific example, depending on the purpose, an upper case with transparent glass or a diffraction grating can be used. The invention shown in FIG. 2 also has wide versatility.

According to the present invention, the number of parts is reduced by one in the optical pickup of the J)%3B method. Furthermore, if the polarizing beam splitter in FIG. 1 is replaced with a half prism to create an optical system that excludes the quarter wavelength plate, the number of parts will be reduced by 1d2. This optical system is used to suppress noise by returning a small amount of light to the semiconductor laser.

According to the present invention, the number of parts can be reduced by 1 to 2 in the optical pickup of the JL and 3B methods, making it possible to reduce the size, weight, and cost. This makes digital audio disc players and optical video disc players smaller and lighter.
Cost reduction becomes possible.

As mentioned above, if a semiconductor laser with a diffraction grating provided on the case window is used for a 3B optical pickup, it becomes possible to make the optical pickup smaller, lighter, and lower in cost, and as a result, the player using this can be made smaller. It also becomes possible to reduce weight and cost.

[Brief explanation of drawings]

Fig. 1 1α1 [b) Optical system of Φ fist 3B method optical pick amplifier Fig. 2: One specific example of the present invention Fig. 3: Other specific example of the present invention 1: Semiconductor laser 2: Diffraction grating 3: Polarizing beam splitter 4: Collimator e-lens 5: Quarter-wave plate 6: Objective lens 7: Disk 8 Ni-lintrical lens 9: Photodetector element 1O2 semiconductor laser 0 chip 1J: Case 12: Diffraction grating 13: Semiconductor laser chip 14 : Lower case 15: Diffraction grating 16: Upper case 17: Transparent glass 18: Above case Applicant: Suwa Seikosha Co., Ltd. (d>(&) Figure 1 Figure 2 Q Figure 3

Claims (1)

[Scope of Claims] A semiconductor laser characterized in that a diffraction grating is provided in a window portion of a case of the semiconductor laser from which light from the il+ semiconductor laser is emitted. (2) There is a male thread on the outside of the cylindrical part of the lower case where the semiconductor laser chip is mounted, and a female thread on the inside of the cylindrical part of the upper case where the window part is equipped with transparent glass that also features a diffraction grating. A semiconductor laser that exhibits a t-a signal when cut.