JPS63273382A - Laser diode - Google Patents

Abstract

PURPOSE:To obtain a diode which has less spherical aberration and irradiates a laser light by bringing the center of curvature of a window of a case into coincidence with a light emitting point. CONSTITUTION:A window 13A is secured to the opening 12 of a case 11. The window 13A has a curvature so that the center of the curvature coincides with a light emitting point 14a. According to this configuration, the optical path lengths of the laser lights L when laser lights L irradiated radially from the point 14a pass the window 13A become equal, and no spherical aberration occurs. Accordingly, when the laser diode 1A of this configuration is used for an optical head, the laser light condensing performance is improved to improve the reliability as a light source for the head.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a laser diode used in an optical head of an optical recording/reproducing device, and more particularly to a laser diode that emits laser light with little spherical aberration.

[Prior Art] FIG. 2 is a cross-sectional view showing a conventional laser diode described in, for example, Japanese Utility Model Application Publication No. Sho 61-140560.

In the figure, (1) is a laser diode, (11) is a case serving as the exterior of the laser diode (1), and (12) is an opening formed on the top surface of the case (11).

(13) is a laser beam transmission window made of parallel flat glass fixed to the inside of the opening (12);
1) It also has the role of sealing the inside and protecting it from external atmosphere such as moisture.

(14) is a light emitting part installed inside the case (11), and the laser light from the light emitting point (14a) is emitted to the outside of the laser diode (1) through the window (13). ing.

Figure 3 is a cross-sectional view showing an optical head using the laser diode (1) in Figure 2 as a light source, where C is a collimating lens provided at the laser beam emission position, and (2) is a half prism. Beam splitter, (3) is a condensing lens for concentrating the laser beam L1 that has passed through beam splitter (2) into a light spot, (4) is a condensing lens (
3) is an optical disc as an information carrier to which the laser beam L1 focused is irradiated; T is a convex lens that focuses the laser beam L2 reflected by the optical disk (4); and (5) is the condensed laser beam L2. It is a photodetector that receives light.

The optical head used in an actual optical recording/reproducing device is mounted on a movable stage (not shown) that moves at high speed in the radial direction of the optical disc (4) in order to select a track to be reproduced on the optical disc (4). ing. Further, the condensing lens (3) serving as an objective lens has an error detection sensor and an actuator (both not shown) for focusing and tracking the optical disk (4).

Next, the operation of an optical head using a conventional laser diode (1) will be explained with reference to FIGS. 2 and 3. Here, a case will be explained taking as an example a case where information recorded on an optical disc (4) is reproduced.

First, the laser light emitted from the aperture (12) of the laser diode (1) becomes a parallel beam at the collimating lens C, passes through the beam splitter (2), and is further converged at the condensing lens (3). It becomes a light spot and an optical disc (
4) is irradiated.

Next, the laser beam L2 reflected by the optical disk (4) travels backwards, has its optical path bent by the beam splitter (2), is condensed by the convex lens T, and enters the photodetector (5). Then, the photodetector (5) detects the reflected laser beam L.
The information on the optical disc (4) contained in the optical disc (4) is converted into an electrical signal and output.

At this time, since the window (13) of the laser diode (1) is a parallel plate, the laser light emitted radially is transmitted through the window (13).
13), the length of the optical path is different between the center and the periphery, resulting in spherical aberration.

Generally, if there is no spherical aberration in the laser light emitted from the laser diode (1), the laser light L1 focused by the condensing lens (3) will be at the fish collecting position as shown in Figure 4(a). Form a light spot. However, if the laser beam L1 contains spherical aberration, the laser beam L1 cannot be converged at the fish gathering position as shown in FIG. decreases.

[Problems to be solved by the invention] As described above, the conventional laser diode (1) has a window (1).
3) is a parallel plate, there is a problem in that spherical aberration occurs in the laser light emitted from the window (13).

This invention was made to solve the above-mentioned problems, and its purpose is to obtain a laser diode that emits laser light with little spherical aberration.

[Means for Solving the Problems] In the laser diode according to the present invention, the window has a curvature, and the center of curvature of the window coincides with the light emitting point on the light emitting part.

[Operations] In this invention, the optical path lengths of the laser beams passing through the window are made equal to reduce spherical aberration.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure is a sectional view showing one embodiment of this invention, (1^)
corresponds to the laser diode (1), (11),
(12) and <14) are the same as above.

(13A) is a window fixed to the opening (12),
It has a curvature, and the center of curvature coincides with the light emitting point (14a).

According to the above configuration, since the optical path lengths of the laser light radially emitted from the light emitting point (14a) when passing through the window (13A) are equal, spherical aberration does not occur.

Therefore, when the laser diode (1^) shown in Fig. 1 is used in an optical head as shown in Fig. 3, the focusing performance of the laser beam L1 is improved as shown in Fig. 4 (,), and the laser diode (1^) for the optical head is improved. Reliability as a light source is improved.

In addition, in the above embodiment, the window (13A) is connected to the case (11).
Although the case is shown in which the case (11) is fitted, it may also be adhered to the upper surface of the case (11).

Also, a laser diode (1^) was used for the optical head, but
It goes without saying that the same effect can be achieved even when applied to other laser application devices such as laser printers and laser measuring devices.

[Effects of the Invention] As described above, according to the present invention, the window has its own room, and the center of curvature of the window is made to coincide with the light emitting point on the light emitting part, so the optical path length of the laser light passing through the window can be reduced. This has the effect of making it possible to obtain a laser diode that can emit laser light with little spherical aberration.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a sectional view showing a conventional laser diode, Fig. 3 is a sectional view showing an optical head using a conventional laser diode, and Fig. 4 is a sectional view showing an optical head using a conventional laser diode. It is an explanatory view showing a condensing state of laser light. (1^)... Laser diode (11)... Case (12)... Opening (13A)... Window (14)... Light emitting part (14a)... Light emitting point...・Laser light surface: In the figures, the same reference numerals indicate the same or equivalent parts. Trap 1 Kasumi Heron 2 Figure Child 3 Da

Claims (1)

[Claims] A laser diode comprising a case having an opening, a window fixed to the opening, and a light emitting part installed in the case and emitting laser light through the window, wherein the window has a curvature, and A laser diode characterized in that the center of curvature of the window coincides with a light emitting point on the light emitting section.