JPS62283687A - Light emitting device - Google Patents

Abstract

PURPOSE:To reduce the size and weight of a light emitting device by using a light transmission member having a function for correcting a light from a light source to parallel beam and an ellipse correcting function. CONSTITUTION:The second surface (plane of emission) 3b of a light transmission member 3 is brought in coincidence with the end 5a of an opening side, and a first surface (plane of incidence) 3a is disposed in a housing 5. Electrodes 6 are energized to emit a light beam L1 from a light source 12 toward a light transmission member 3. The beam L1 is refracted at the first surface ea of the member 3, corrected to a parallel beam (light beam L2) to the second surface 3b. lt is elliptically corrected by the second surface 3b to an emitted light beam L3 in which its perpendicular section is circular and its optical axis coincides with the axial direction of the housing 5. The beam L3 is applied as a spot S on a recording film 33 opposed to a guide groove 34, and the reflected light is introduced through the film 33 and a disk substrate 32 to an objective lens 22 side.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention corrects a light beam emitted from a light source such as a semiconductor laser diode used in an optical head, etc. The present invention relates to a light emitting device that emits light.

(Prior Art) For example, when recording or reproducing information on an optical disk in an image information file device or the like, an optical head having a light emitting device using a semiconductor laser diode as a light source is used.

However, the light emitted from a semiconductor laser diode is diffused light and its orthogonal cross-sectional shape is an ellipse, so correcting the diffused light to parallel light and its cross-sectional shape to a circular shape improves the convergence of this light. This is essential for improving the intensity and making the intensity distribution uniform.

A conventional example of such a light emitting device will be explained with reference to FIG.

The light emitting device 50 shown in the figure includes a light source 12 using a semiconductor laser diode, a collimating lens 11 consisting of a plurality of lens groups that corrects the light beam generated from the light source 12 into parallel light, and this collimating lens 11. The correction prism 13 receives parallel light, performs ellipse correction on the light, and emits parallel light whose orthogonal cross section is circular.

According to this light emitting device 50, the light beam from the light source 12 can be corrected and emitted as a parallel light beam and a light beam with a circular cross section, so that information can be recorded or The amount of light beam necessary for reproduction can be obtained.

However, since it includes a collimating lens 11 for collimating the light beam from the light source 12 and a correction prism 13 for correcting the ellipse, the overall shape of this light emitting device 50 becomes large, and the light beam directed to the correction prism 13 is
, 12 also have a problem in that strict precision is required depending on the inclination angle of the correction prism 13.

(Problems to be Solved by the Invention) As described above, conventional light emitting devices have problems in that they are large in size and heavy in weight, and are accompanied by restrictions on the arrangement of the light source and the correction prism.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a light emitting device that has a function of correcting a light beam from a light source to parallel light and an ellipse correction function, and is small and lightweight (means for solving the problem). ) The light emitting device of the present invention has a light source, an entrance surface having an aspherical shape to convert the light generated from the light source into a parallel beam, and a planar shape that corrects the cross-sectional shape of the parallel light to a substantially circular shape. and a light-transmitting member having a light exit surface.

(for production) The operation of the apparatus having the above configuration will be explained below.

The light beam from the light source enters the aspherical incident surface of the light-transmitting member, and becomes parallel light due to the action of the incident surface, and travels inside the light-transmitting member. Then, this parallel light reaches an exit surface having a planar shape, and is emitted to the outside from the exit surface whose cross-sectional shape has been corrected to be approximately circular.

(Example) Examples of the present invention will be described in detail below.

First, the present invention will be explained in detail with reference to FIGS. 41 to 6.

In the figure, G is a light-transmitting member (for example, glass) having an aspherical refractive surface and having a refractive index n. It is assumed that the In point of this refraction surface is taken as the origin A of the orthogonal X and Y axes. Further, in the figure, it is assumed that the right side of the refractive surface of the light-transmitting member G is air having a refractive index of 1.

At this time, the light traveling parallel to the Gex axis of the light-transmitting member is refracted at a point P on the refraction surface, and reaches a focal point F on a surface (indicated by a dotted line in the figure) that is symmetrical to the refraction surface, which is assumed to be in the air. Consider the case of focusing.

Now, AF=f, the coordinates of point P are (x, y) (however, x<Q
), the following equation (1) can be obtained.

-nx+ (y2 + (f-x)2bi= f ・(1
] When formula (1) is rearranged, the following formula (2) is obtained.

y2- (n2-1 > x2 +2f (n-1)
x=0...(2) This equation (2) has the same form as the general equation whose origin is the vertex of the left branch of the hyperbola.

Therefore, the refractive surface becomes a hyperboloid, and xlFI! All light traveling parallel to I is at the focal point F
It will converge to .

As shown in FIG. 5, by using a light-transmitting member 2 having a second surface 2b which is a hyperboloid as described above and a first surface 2a perpendicular to the incident light, parallel to the X-axis For such light, it is possible to construct a light-transmitting member 2 in which spherical aberration is removed.

In the above-mentioned light-transmitting member 2, if we consider the case where the traveling direction of light is reversed, from the focal point F to the second
The light diffusing toward surface 2b is refracted by this hyperboloid, and
The light becomes parallel to the axis and is emitted from the first surface 2a. In this case, the diffused light is corrected to parallel light, but its orthogonal cross-sectional shape is not corrected in any way.

Therefore, if the light from the focal point F has an elliptical orthogonal cross section like the light emitted by a semiconductor laser diode, then
The orthogonal cross-sectional shape of the parallel light also remains elliptical.

Therefore, as shown in FIG. 6, the first surface of the light-transmitting member 3 (
The entrance surface > 3a is a hyperboloid, the second surface (the exit surface > 3b is the first
A predetermined inclination angle φ with respect to the optical axis of the light that has become parallel light at the surface 3a
A device with an inclined plane having .

According to the light transmitting member 3, it is possible to correct diffused light having an elliptical orthogonal cross section to parallel light having no spherical aberration and having a circular orthogonal cross section.

Next, an embodiment of a light emitting device based on the above principle will be described with reference to FIG.

The light emitting device 10 shown in the figure includes a cylindrical housing 5 in which one end is closed with a substrate 4 and the other end is opened with a slope, and the substrate 4 is connected inside the housing 5. A light source 12 using a semiconductor laser diode placed on an integrally formed light source placement part 4a, a light transmitting member 3 attached to an opening of the housing 5, and a first In the figure, the electrode 6 is arranged to protrude downward and is electrically connected to the light source 12.

The end face 5a of the housing 5 on the opening side is the housing 5
It is formed into an inclined surface that is inclined at a certain angle with respect to the axial direction. Then, the second surface (output surface) 3b of the light transmitting member 3 is aligned with the end 5a on the opening side, and the first surface (incidence surface) 3a is made to face the inside of the housing 5. There is.

The light source 12 is placed on the light source placement part 4a so that the optical axis of the light beam emitted from the light source 12 forms a predetermined angle of 0 with respect to the axial direction of the housing 5, so that the light transmitting member 3 The optical axis of the light emitted from the second surface 3b of the housing 5 coincides with the axis of the housing 5.

Next, the operation of the embodiment apparatus having the above configuration will be explained.

By energizing the electrode 6, a light beam L1 is emitted from the light source 12 toward the light-transmitting member 3.

This light beam L1 is refracted by the first beam 3a of the light transmitting member 3, corrected into parallel light (light beam L2), and reaches the second beam 3b. Then, ellipse correction is performed by the second surface 3b, and an output light beam L3 whose orthogonal cross section is circular and whose optical axis coincides with the axial direction of the housing 5 is emitted.

Next, a schematic configuration of an optical head 20 using the above-mentioned light emitting device 10 and an optical disc 3 using this optical head 20 will be described.
A method of recording or reproducing information to or from 1 will be explained.

An example of this optical disc 31 will be explained with reference to FIG. 3. The optical disc 31 shown in the figure has a recording film 33 on a disc-shaped disc substrate 32 on which arc-shaped pre-groups are provided.
A guide groove 34 corresponding to the pre-group is formed by vapor deposition or the like, and pits 35 as recording information are formed at predetermined intervals on the recording film 33 in this guide groove 34.
This is a reproduction-only type that is configured by providing a. Then, the guide groove 3 is
A light beam L3 is irradiated as a spot S onto the recording film 33 facing 4, and the reflected light is guided to the objective lens 22 side via the recording film 33 and the disk substrate 32.

Next, FIG. 3 (a>,
An example of reproducing recorded information on the optical disc 21 shown in FIG. 12(b) will be explained.

The light beam L1 generated by the light source 12 of the light emitting device 10 reaches the first surface 3a of the light-transmitting member 3 and becomes a parallel light beam L2 based on the above-mentioned principle. This light beam L2 travels through the light-transmitting member 3, reaches the second surface 3b, and is subjected to ellipse correction based on the above-mentioned principle to become a light beam L3 whose orthogonal section has a substantially circular shape. This light beam L3 passes through the beam splitter 21, is focused by the objective lens 22, and is irradiated as a spot S onto the guide groove 34 of the optical disc 31.

Then, the reflected light passes through the recording 1151j33 and the disk substrate 32, reaches the objective lens 22, becomes parallel light, and enters the beam splitter 21. Roughly, this light beam L3 is reflected by the beam splitter 21 and reaches the condensing lens 23, where it is condensed by the action of the condensing lens 23 and enters the photodetector 24.

Through this series of actions of the optical head 20, it is possible to obtain, as an output signal of the photodetector 24, a recorded information signal, that is, a reproduced signal, which is based on the difference in reflectance based on the presence or absence of the pits 35, and A focus signal and a tracking signal for the optical disc 31 can be obtained,
For example, by driving means for the objective lens 22 (not shown), the objective lens 22 can be moved up and down or left and right in FIG. 2 to perform focus correction or tracking correction.

According to this optical head 20, since the light emitting device 10 can be configured to be small and lightweight, the optical head 20 itself can be made small and lightweight.
It becomes possible to reduce the weight. As a result, this optical head 20
This has the effect of shortening the access time to the optical disc 31.

The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the invention.

For example, in the above embodiments, a hyperbolic surface is used as the aspheric surface of the light-transmitting member, but the same filtering performance can be achieved by using a circular surface or a parabolic surface.

It goes without saying that the light emitting device of the above embodiment is not only used as a light source for an optical disk provided with pits, but also applied to an optical head of an erasable optical disk, such as a magneto-optical disk or a phase-change optical disk. That's it.

[Effects of the Invention] According to the present invention described in detail above, the size can be reduced by using a light-transmitting member that has both the function of correcting the light from the light source into parallel light and the function of correcting ellipse.

A light-emitting device that can be lightweight can be provided.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a schematic explanatory view showing the configuration of an optical head using the same device, and FIG.
The figure is a partially enlarged explanatory diagram of an optical disc, FIGS. 4 to 6 are diagrams each illustrating the principle of the present invention, and FIG. 7 is an explanatory diagram showing a conventional light emitting device. 3... Photo-transmissive member, 3a... First surface, 3b... Second surface, 10... Light emitting device, 12... Light source.゛°−1 Figure 3

Claims (3)

[Claims] (1) Light transmission having a light source, an entrance surface with an aspherical shape that corrects the cross-sectional shape of the light beam to parallel light, and an exit surface with a planar shape that corrects the cross-sectional shape to a substantially circular shape. A light-emitting device characterized by having a sexual member. (2) The light emitting device according to claim 1, wherein the light source and the light transmitting member are arranged at a predetermined angle. (3) The light-transmissive member has an aspherical entrance surface that corrects the light beam generated from the light source into parallel light, and an aspherical entrance surface that is inclined with respect to the optical axis of the parallel light to change the cross-sectional shape of the parallel light. 2. The light emitting device according to claim 1, wherein the light emitting device has a light emitting surface that emits light after being corrected to have a substantially circular shape.