JPH05151606A - Optical head device - Google Patents

Abstract

PURPOSE:To eliminate a shaping prism, simultaneously to thin an optical element and to miniaturize and thin an optical head device by using a hologram optical element combining a function reflecting a laser beam from the arrangement surface of an optical system to the direction of a recording medium and a function converting the elipse shape of the laser beam into a roughly circular shape. CONSTITUTION:This device is constituted so that the laser beam of the elipse shape outgoing from a laser light source 1 is parallelled by a collimate lens 2 and passes through a beam splitter 3 and the optical path of the beam is reflected in the direction of the recording medium and the beam shape is made the roughly circular shape by the hologram surface 5 of a reflection mirror prism 4 and the beam is converged by art objective lens 6, and information is recorded on or reproduced or erased from the recording medium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head device used in an optical recording / reproducing apparatus for reproducing information on a recording medium or for recording / reproducing or recording / reproducing / erasing information on the recording medium. Is.

[0002]

2. Description of the Related Art In optical recording, a device such as an optical disk for optically reproducing information on a concentric or spiral track formed on the disk has already been put into practical use.

The structure of an image forming optical system (optical system from a laser light source to a recording medium) of a conventional basic optical head device will be described with reference to FIGS. 4 and 5. FIG. 4 is a side view of the imaging optical system of the conventional optical head device, and FIG. 5 is a plan view of the imaging optical system of the conventional optical head device.

In the optical head device shown in FIGS. 4 and 5, the laser light emitted from the laser light source 11 has an elliptical shape, and after being collimated by the collimator lens 12,
The shaping prism 13 makes a substantially circular shape. The substantially circular laser light passes through the beam splitter 14 and is reflected by the rising mirror 15 along the optical path toward the recording medium 17,
Further, it is condensed by the objective lens 16 to form a minute spot on the recording medium 17.

In this optical head device, a collimator lens 12 and a shaping prism 13 are used in order to efficiently guide the laser light emitted from the laser light source 11 to the recording medium 17.

[0006]

However, this method has a drawback that it is difficult to miniaturize the optical head device because the shaping prism used for making the laser beam substantially circular expands the optical arrangement area. .. Further, since it has a function of enlarging the narrow emission angle direction of the elliptical semiconductor laser emission light, it is necessary to arrange the wide emission angle direction perpendicular to the optical arrangement surface, which makes it difficult to reduce the thickness of the optical head device. There was a drawback.

Therefore, an object of the present invention is to eliminate the shaping prism without lowering the utilization efficiency of laser light,
An object of the present invention is to provide an optical head device that can be made compact and thin.

[0008]

Therefore, in order to solve the above-mentioned problems, the present invention uses a hologram optical element to reflect a laser beam from a surface on which an optical system is arranged toward a recording medium, and It is a combination of circularizing functions.

[0009]

According to the present invention, the hologram optical element has a shaping prism that serves to reflect the laser light from the optical system arrangement surface toward the recording medium and to substantially circularize the laser light, thereby enlarging the optical arrangement area. By eliminating it and enabling miniaturization of the optical element, the problem of miniaturization and thinning of the optical head device is solved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to FIGS. 1 is a side view of an image forming optical system of an optical head device of the present invention, FIG. 2 is a plan view of an image forming optical system of an optical head device of the present invention, and FIG. 3 is a configuration diagram of a hologram optical element of the present invention. ..

In FIG. 1, 1 is a laser light source, 2 is a collimating lens, 3 is a beam splitter, 4 is a reflection mirror prism, 5 is a hologram surface, and 6 is an objective lens.
In the imaging optical system of the optical head device, the elliptical laser light emitted from the laser light source 1 is collimated by the collimator lens 2, transmitted through the beam splitter 3, and the hologram surface 5 of the reflection mirror prism 4 changes the optical path. The beam is reflected in the direction of the recording medium and the beam shape is made substantially circular.
It is configured to focus light on.

Next, the structure of the hologram optical element will be described with reference to FIG. In FIG. 3, the reflection mirror prism 4 has a shape of an acute angle of 45 ° or less with an incident ray of laser light, and a hologram surface 5 is attached to the reflection surface. The hologram surface 5 on the reflection mirror prism 4 uses a laser beam of a specific wavelength to generate a plane wave 8 from a direction perpendicular to the recording medium (direction A in the figure) and a direction horizontal to the optical arrangement surface (in the figure). This is an element in which interference fringes of the plane wave 9 from the direction B) are recorded, and when a parallel laser beam is emitted from the direction B in which the plane wave 9 is recorded, the laser beam is reflected in the direction of the recorded plane wave 8. That is, FIG.
When the divergent light emitted from the laser light source 1 is collimated by the collimator lens 2 and is incident on the hologram surface 5, the laser light is reflected in a direction perpendicular to the recording medium 7. At this time, the elliptical laser light is expanded on the minor axis side and converted into a substantially circular shape.

In each of the above embodiments, by using the hologram optical element for reflecting the laser light from the optical system arrangement surface toward the recording medium and converting the shape of the laser light into a substantially circular shape,
By eliminating the shaping prism of the optical head device and using a collimating lens having a sectional shape of 8, an optical head device that can be made smaller and thinner can be realized.

Although an example using a collimator lens is shown in the embodiment, a finite system optical head device which does not use a collimator lens by using a hologram optical element recorded by causing spherical waves to interfere with each other from two directions. Can also be applied.

Furthermore, the present apparatus can be applied to all optical head devices used for read-only recording media, write-once recording media, or rewritable recording media.

[0016]

As described above, the present invention provides a hologram optical element that combines the function of reflecting laser light from the optical system arrangement surface toward the recording medium and the function of converting the elliptical shape of laser light into a substantially circular shape. By using it, the shaping prism can be eliminated, and the thickness of the raising mirror and other optical elements in the height direction of the optical head can be reduced, so that the optical head device can be made smaller and thinner. ..

[Brief description of drawings]

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

FIG. 2 is a plan view of an image forming optical system of an optical head device showing an embodiment of the present invention.

FIG. 3 is a schematic diagram showing a configuration of a hologram optical element of the present invention.

FIG. 4 is a side view showing an image forming optical system of a conventional optical head device.

FIG. 5 is a plan view showing an image forming optical system of a conventional optical head device.

[Explanation of symbols]

 1 Laser Light Source 2 Collimating Lens 3 Beam Splitter 4 Hologram Reflecting Mirror (Reflecting Mirror Prism) 5 Hologram Reflecting Mirror (Hologram Surface) 6 Objective Lens System (Objective Lens) 7 Recording Medium 8'Collimating Lens Cross Section 9,10 Plane Wave

Claims (1)

[Claims] 1. A laser light source, and a reflection function for reflecting laser light emitted from the laser light source toward a recording medium,
The hologram reflection mirror is provided with a hologram reflection mirror having a conversion function of converting the laser light into a substantially circular shape, and an objective lens system for condensing reflected light reflected by the hologram reflection mirror on a recording medium. An optical head device characterized in that its mirror surface is arranged at an acute angle or an obtuse angle with respect to the emission direction of the laser light.