JPH0567918U - Optical head device - Google Patents

Abstract

(57) [Summary] [Object] To provide an optical head device that can be thinned even when a laser unit having the same size as a conventional one is used. [Structure] A parallel prism 8 having a parallelogrammatic cross section is provided between a laser unit 2 and a mirror 4. Since the light incident on the parallel prism 8 is diffracted, the distance between the optical axis H at both ends of the parallel prism 8 with respect to the disk 1 is different. be able to.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an optical head device that optically reads information recorded on a disc.

[0002]

[Prior Art]

 As an optical disc device that optically reads information recorded on a disc, the configurations shown in FIGS. 3 and 4 are known. 3 is a side view and FIG. 4 is a plan view.

Reference numeral 1 denotes a disc, on the surface of which information is previously recorded in the form of pits. Reference numeral 2 denotes a laser unit having a laser diode 3, and the laser diode 3 emits light having an optical axis H formed so as to be parallel to the surface of the disk 1 and makes it enter a mirror 4. The path of the light is changed by the mirror 4 in the orthogonal direction so that the optical axis Z is formed and is incident on the objective lens 5, and the objective lens 5 focuses the light on the recording surface of the disc 1. Is converged on and irradiated.

The optical signal of the information reflected by the recording surface of the disk 1 is incident on the objective lens 5 again, and then its path is changed to the orthogonal direction by the mirror 4 and is incident on the beam splitter 6 as shown in FIG. Then, the beam splitter 6 changes the path again to the orthogonal direction, and then the light enters the photodetector 7. The information optically read by the photodetector 7 is converted into an electric signal and output.

[0005]

[Problems to be solved by the device]

 By the way, in the conventional optical head device, since the base 3A of the laser diode 3 has a constant dimension B in the direction of the optical axis Z.sub.1, there is a problem in that there is a restriction when making the optical head device thinner.

In this case, it is conceivable to bring the laser unit 2 closer to the disc 1 side in order to reduce the thickness, but along with this, the mirror 4 also has to be brought closer to secure the optical axis H. This causes an adverse effect such that the stroke of the objective lens 5 for following the surface wobbling of No. 1 in the optical axis Z direction becomes insufficient.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical head device that can be thinned even when a laser unit having the same size as a conventional one is used. Is.

[0008]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention provides an optical head device having a laser unit for generating a light beam, and a mirror for irradiating a disk by changing the path of light emitted from the laser unit in an orthogonal direction, A parallel prism having a parallelogrammatic cross section is provided between the laser unit and the mirror.

[0009]

[Action]

 By providing a parallel prism having a parallelogrammatic cross section between the laser unit and the mirror, the light incident on the mirror from the laser unit can be diffracted. This makes it possible to secure the optical axis H and the stroke of the objective lens even if a laser unit having the same size as that of the conventional one is brought close to the disk side, and therefore the optical head device can be made thinner. Can be planned.

[0010]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing an embodiment of the optical head device of the present invention. Reference numeral 1 is a disk on which information is recorded on the surface, 2 is a laser unit including a laser diode 3 having a base 3A having a constant size B, 4 is a mirror, 5 is an objective lens, and the same structure as the conventional one is used. It has become.

Reference numeral 8 is a parallel prism having a parallelogrammatic cross section and has a shape as shown in FIG. 2 and is provided between the laser unit 2 and the mirror 4. Due to the shape of the parallel prism 8, the incident light is diffracted and travels, so that its optical axis H changes stepwise. Therefore, the distance of the optical axis H to the disc 1 is different at both ends of the parallel prism 8, and the optical axis H of one end 8A of the parallel prism 8 is closer to the disc 1 than the optical axis H of the other end 8B. Becomes

According to the above-mentioned structure, the objective lens 5 converges and irradiates the disc 1 so as to focus on the recording surface, and the light reflected by the recording surface is emitted from the objective lens 5. After being incident on the mirror 4, the optical path is changed in the orthogonal direction, and then the optical path is changed again in the orthogonal direction by the beam splitter 6 as in FIG. 4, and the incident light is incident on the photodetector 7.

According to the present embodiment as described above, the distance from the optical axis H from the other end 8B of the parallel prism 8 to the disk 1 becomes equal to the distance from the conventional optical axis H to the disk 1. Therefore, it is possible to provide the laser unit 2 close to the disc 1 and the difference between the distance between the optical axis H at the one end 8A of the parallel prism 8 and the disc 1 and the distance.

Therefore, even when the laser unit 2 provided with the laser diode 3 having the base 3 A having the same constant size B as the conventional one is used, the laser unit 2 can be brought close to the disk 1. Moreover, since the distance of the optical axis H incident on the mirror 4 to the disk 1 is secured as in the conventional case, the stroke of the objective lens 5 in the optical axis Z direction to follow the surface wobbling of the disk 1 or the like. Since it can be ensured, it is possible to reduce the thickness of the optical head device without causing any trouble. Further, by bringing the laser unit 2 close to the disk 1, it is possible to substantially reduce the space.

[0015]

[Effect of the device]

 As described above, according to the present invention, since the parallel prism is provided between the laser unit and the mirror, even when the laser unit having the same size as the conventional one is used, the action of the objective lens is not affected. It is possible to reduce the thickness of the optical head device without giving it.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of an optical head device of the present invention.

FIG. 2 is a perspective view showing a parallel prism used in the apparatus of this embodiment.

FIG. 3 is a side view showing a conventional example.

FIG. 4 is a plan view showing a conventional example.

[Explanation of symbols]

 1 disk 2 laser unit 3 laser diode 3A laser diode base 4 mirror 5 objective lens 8 parallel prism

Claims (1)

[Scope of utility model registration request] 1. A laser unit for generating a light beam,
In an optical head device having a mirror that changes the path of light emitted from the laser unit to an orthogonal direction and irradiates the disk, a parallel prism having a parallelogrammatic cross section is provided between the laser unit and the mirror. An optical head device.