JP2000113498A - Optical beam forming prism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable forming appropriately light beams having different wavelength without causing the tilt of an optical base respectively. SOLUTION: This prism has a first optical plane 12 on which a light beam is refracted and made incident, a dichroic film 15 in which a light beam of a wavelength of one side refracted and made incident from the first optical surface 12 is reflected and a light beam of a wavelength of the other side is transmitted, a second optical plane 13 reflecting a light beam transmitted through this dichroic film 15, and a third optical plane 14 emitting a light beam reflected by the second optical plane 13 and a light beam reflected by the dichroic film 15. Then, respective emitting optical axes of a light beam of a wavelength of one side emitted from the third optical plane 14 and a light beam of a wavelength of the other side are made parallel to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam shaping prism for shaping a sectional pattern of a light beam.

[0002]

2. Description of the Related Art For example, in an optical disk apparatus for recording or reproducing information on a disk-shaped recording medium (hereinafter simply referred to as an optical disk), a laser diode is generally used as a recording or reproducing light source. Here, since the cross-sectional pattern of the emitted beam is elliptical due to its structure, generally, the cross-sectional elliptical pattern is substantially reduced without reducing the light use efficiency by using a light beam shaping prism. The beam is shaped into a circular cross-section pattern.

FIG. 3 shows a conventional light beam shaping prism used in an optical disk device. The light beam shaping prism 1 also serves as a rising mirror disposed near an objective lens (not shown) for condensing a recording or reproducing light beam on an optical disk (not shown). An incident light beam 2 having a cross-sectional elliptical pattern converted into a light beam is refracted by a first optical surface 3, reflected by a second optical surface 4, and refracted and transmitted from the first optical surface 3. The cross-sectional pattern of the outgoing light beam 5 emitted from the first optical surface 3 is shaped into a circular shape in which the minor axis diameter φa of the incident light beam 2 is expanded so as to be substantially equal to the major axis diameter φb, The light is incident on the objective lens.

[0004]

By the way, recently,
In order to support a plurality of types of optical disks, for example, DVDs and CDs, a plurality of laser diodes that emit light beams of different wavelengths are provided, and a part of the optical system is shared with these laser diodes. 2. Description of the Related Art Compatible optical disk devices have been proposed in which recording and reproduction can be performed by driving a laser diode according to the type.

However, in such an optical disk device, if the light beam shaping prism 1 shown in FIG. 3 is used in common, the refractive index differs depending on the wavelength. For example, when the incident light beam 2 has the wavelength λ1, When the light beam shaping prism 1 is designed so that the optical axis of the output light beam 5 is parallel to the optical axis of the objective lens, the optical axis of the output light beam 5 is set at the wavelength λ2 (≠ λ1). It will be inclined with respect to the optical axis of the lens. As described above, when the optical axis of the light beam incident on the objective lens is tilted, aberration occurs in the beam spot formed on the corresponding type of optical disk by the objective lens, so that accurate recording or reproduction of information cannot be performed. Problems will arise. Such a problem is caused by the light beam shaping prism 1.
Also occurs when the mirror is not used as a rising mirror.

SUMMARY OF THE INVENTION An object of the present invention has been made in view of such a conventional problem, and has been appropriately configured so that light beams having different wavelengths can be appropriately shaped without causing an optical axis tilt. It is intended to provide a light beam shaping prism.

[0007]

In order to achieve the above object, the present invention provides a first optical surface on which a light beam is refracted and incident, and one wavelength which is refracted and incident from the first optical surface. A dichroic film that transmits the light beam of the other wavelength, a second optical surface that reflects the light beam transmitted through the dichroic film, and a light beam that is reflected by the second optical surface. And a third optical surface that emits a light beam reflected by the dichroic film. The light beam of one wavelength and the light beam of the other wavelength emitted from the third optical surface It is characterized in that the respective output optical axes are configured to be parallel.

With this configuration, the light beam of one wavelength which is refracted and incident on the first optical surface is reflected by the dichroic film, and the light beam of the other wavelength is reflected by the second optical surface, Each light beam is emitted from the third optical surface without tilting the optical axis.

In one embodiment of the present invention, the first optical surface and the third optical surface are provided on the same surface.

In this way, the number of optically processed surfaces can be reduced, so that the whole can be simply and inexpensively constructed.

[0011]

FIG. 1 shows an embodiment of the present invention. The light beam shaping prism 11 includes a first optical surface 12 for refracting and entering the light beam, a second optical surface 13 for reflecting the light beam, a third optical surface 14 for emitting the light beam, and a first optical surface 14 for emitting the light beam. , Third optical surfaces 12, 14
And in the optical path between the second optical surface 13 and the wavelength λ
A dichroic film 15 reflects one light beam toward the third optical surface 14 and transmits a light beam of another wavelength to be incident on the second reflection surface. In this embodiment, the first optical surface 12 and the third optical surface 14 are formed on the same surface. The light beam shaping prism 11 includes a triangular prism 11 having first and third optical surfaces 12 and 14.
a and the triangular prism 11 b having the second optical surface 13 can be configured to be joined via the dichroic film 15.

In the above configuration, when the light beam having the wavelength λ1 is obliquely incident on the first optical surface 12 at a predetermined angle,
The light beam is refracted by the first optical surface 12 and enters the dichroic film 15, where it is reflected and refracted and transmitted through the third optical surface 14 to be shaped. Also, the wavelength λ
When the second light beam is obliquely incident on the first optical surface 12 at the same angle, the light beam is refracted by the first optical surface 12 at a refraction angle different from that of the light beam having the wavelength λ1, and is incident on the dichroic film 15. However, the dichroic film 15 has a wavelength λ.
The light beam of wavelength λ 2 is reflected by the dichroic film 15 because the light beam of wavelength 1 is reflected and the light beam of another wavelength is transmitted.
The light is reflected by the second reflection surface 13 and further transmitted through the dichroic film 15, and then refracted and transmitted through the third optical surface 14 to be shaped.

Here, the dichroic film 15 and the second
Is incident on the dichroic film 15 and the second reflection surface 13 such that the respective emission optical axes of the light beams of wavelengths λ1 and λ2 emitted from the third optical surface 14 are parallel. An appropriate angle is set with respect to the optical axis of the light beam of the corresponding wavelength. In such an angle setting, if the angle is changed by the setting, the overall shape of the light beam shaping prism 11 is changed accordingly, which may cause inconvenience such that the prism cannot be accommodated in the intended chassis. In such a case, each of the triangular prisms 11a and 11b may be made of a material having an appropriate refractive index.

According to this embodiment, light beams of different wavelengths λ1 and λ2 can be appropriately shaped without causing any tilt of the optical axis. For example, as described above, a plurality of types of optical discs can be used. When applied to an optical disc device using a plurality of laser diodes that emit light beams of different wavelengths,
A beam spot having no aberration can be formed on each optical disc. Therefore, it is possible to accurately record or reproduce information on various optical disks. In this case, in accordance with the parallel movement of the output optical axis of the light beam shaping prism 11 due to the used wavelength, the optical axes of the subsequent optical elements may be moved in parallel.

[0015] The present invention is not limited to the above-described embodiment, but can be variously modified or changed. For example, in the above-described embodiment, the first optical surface 12 and the third optical surface 14 are provided on the same surface as a prism having a triangular cross section as a whole. However, as shown in FIG.
The optical surface 12 and the third optical surface 14 are separately provided, and the dichroic film 15 is arranged in the optical path between the first and third optical surfaces 12 and 14 and the second optical surface 13. , FIG. 2B
As shown in FIG. 1, a first optical surface 12 and a third optical surface 14 are separately provided, and a first optical surface 12 and a second optical surface 13 are provided.
The dichroic film 15 is arranged in the optical path between
Various modifications are possible, and the overall cross-sectional shape can be an arbitrary polygonal shape. Also, at least two or more dichroic films for selectively reflecting light beams of different wavelengths are provided in an optical path between at least the first optical surface 12 and the second optical surface 13 so that light beams of three or more wavelengths are provided. Similarly, the beam shaping can be performed without causing the optical axis to tilt.

[0016]

As described above, according to the present invention, light beams having different wavelengths can be properly shaped without causing any tilt of the optical axis.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a light beam shaping prism according to the present invention.

FIG. 2 is a sectional view showing two modified examples of the light beam shaping prism according to the present invention.

FIG. 3 is a cross-sectional view illustrating a conventional light beam shaping prism.

[Explanation of symbols]

 Reference Signs List 11 light beam shaping prism 11a, 11b triangular prism 12 first optical surface 13 second optical surface 14 third optical surface 15 dichroic film

Claims (2)

[Claims] 1. A first optical surface on which a light beam is refracted and incident, a light beam of one wavelength refracted and incident from the first optical surface is reflected, and a light beam of the other wavelength is transmitted. A dichroic film, a second optical surface for reflecting a light beam transmitted through the dichroic film,
A third optical surface that emits a light beam reflected by the optical surface and a light beam that is reflected by the dichroic film; and a light beam of the one wavelength emitted from the third optical surface; A light beam shaping prism, wherein each of the outgoing optical axes of the light beam of the other wavelength is parallel to each other. 2. The light beam shaping prism according to claim 1, wherein said first optical surface and said third optical surface are provided on the same surface.