JP3422732B2 - Light head - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head provided in an optical recording / reproducing system for condensing light having a plurality of wavelengths to record / reproduce information signals on / from a recording medium.

[0002]

2. Description of the Related Art In recent years, with the development of information technology, an optical recording medium which is a recording medium having a small size and a large capacity has been used. Such an optical recording medium is a CD (Compact Disc), a CD
-ROM (Compact Disc-Read Only Memory), DVD
Playback-only recording media such as (Digital Video Disc), CD-
It is classified into a write-once recording medium in which an information signal can be written only once such as R (Compact Disc-Recordable) and a rewritable recording medium in which the information signal can be rewritten a plurality of times.

As the rewritable recording medium, a magneto-optical recording medium such as a magneto-optical disk is known. When an information signal is recorded on this magneto-optical recording medium, the magnetization state in the recording layer is changed by applying an external magnetic field having a polarity corresponding to the recording information while irradiating the recording layer made of a magnetic material with laser light. Is reversed in the direction of.

Increasing the recording density of the rewritable recording medium is one of the important technical problems in the magneto-optical recording medium. Conventionally, as a means for realizing a high density of a magneto-optical recording medium, for example, the 13th Applied Magnetics Society Lecture Summary (issued in 1989, page 68) and Japane
se Journal of Applied Physics, Vol.28 (1989) Suppleme
As described in nt28-3pp.343-347, there is known a multi-level recording method for multi-leveling and recording an information signal.

In the multi-valued recording system, when an information signal is recorded on a magneto-optical recording medium in which a plurality of magnetic layers having different coercive forces are laminated as recording layers, the magnetic field strength applied to the magnetic layer is set in multiple steps. By modulating, the magnetization of the specific magnetic layer is selectively inverted. According to such a multi-valued recording system, four-valued recording of information signals becomes possible by providing two magnetic layers having different coercive forces in the magneto-optical recording medium.

However, according to the multi-valued recording system using the magneto-optical recording medium, the signal detected from the magneto-optical recording medium is detected at a plurality of levels in order to detect the information signal multi-valued recorded during reproduction. Since the multi-valued recording signals are distinguished by each other, a large difference in signal amplitude corresponding to each multi-valued state cannot be taken, and it is difficult to accurately distinguish two multi-valued states having a small difference in signal amplitude. Met. Therefore, the multilevel recording method using the magneto-optical recording medium has a problem that the reproduced multilevel signal has a low S / N.

As a method for solving such a problem,
As disclosed in Japanese Patent Application No. 8-309946, a method of reproducing an information signal from a plurality of recording layers with a high S / N by reproducing an information signal using a reproducing light having a plurality of wavelengths. Is mentioned.

As described above, the optical head which reproduces the information signal by using the reproducing light having a plurality of wavelengths can realize a high density and high performance optical disc system by using a plurality of wavelengths.

[0009]

However, an optical lens for condensing light on a magneto-optical recording medium has chromatic aberration such as a focal length varying depending on the wavelength because the refractive index varies depending on the wavelength. Therefore, when focusing light on a magneto-optical recording medium using an optical lens having a plurality of wavelengths, it is necessary to design the optical lens in consideration of a plurality of wavelengths included in the light. Specifically, when condensing light having a plurality of wavelengths to form a spot, it is necessary to calculate the focal length of each wavelength and design the optical lens.

Furthermore, by increasing the density of the magneto-optical recording medium,
When increasing the number of wavelengths used for the reproduction light, it is necessary to use an optical lens corresponding to the wavelength used, increase in the number of optical components used in the optical head, complexity of optical system adjustment, etc. Inconvenience occurs.

Therefore, the present invention has been proposed in view of the above situation, and provides an optical head capable of condensing light onto a recording medium without causing chromatic aberration. With the goal.

[0012]

An optical head according to the present invention which solves the above-mentioned problems is provided with a reflecting portion which has a predetermined curvature and is formed in a concave shape to form a reflecting film, and which has a plurality of wavelengths. Is provided, the incident light is reflected, the optical axis is changed, and the light is condensed on the recording medium.

[0013]

In order to solve the above-mentioned problems, the optical head according to the present invention has a first incident surface on which light having a plurality of wavelengths is incident and a first incident surface on which the incident light is emitted. And a concave mirror surface portion that reflects the light reflected by the convex mirror surface portion to the first light emitting surface. An incident portion, a second incident surface on which the light reflected by the concave mirror surface portion is incident, and a second emission surface on which the light incident from the second incident surface is emitted to the optical disc. An emission part, the first emission surface is in close contact with the second incidence surface, and the concave mirror surface portion condenses light on the second emission surface. According to such an optical head, it is possible to focus the light on the recording medium only by the reflection of the light without utilizing the refraction of the light.

According to such an optical head, the light is focused on the recording medium without utilizing the refraction of the light.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

An optical head to which the present invention is applied is shown in FIG.
It is configured as shown in.

The optical head 1 comprises a condenser element 2 arranged on the optical disc D, and a lens suspension 3 for disposing the condenser element 2 on the optical disc D.

The condensing element 2 includes a substrate 11 and a substrate 11.
And a reflection film 13 formed in a concave shape.

The substrate portion 11 is made of, for example, a glass material or the like, and a hemispherical concave portion 12 is formed by processing and molding a part thereof.

The concave portion 12 is shaped to have a curvature such that the laser beam L is incident thereon and a minute spot S is formed on the optical disc D.

The reflection film 13 is made of, for example, a light reflection material such as Al and is formed on the concave surface portion 12 with a constant film thickness. The reflection film 13 reflects the incident laser light L. This reflecting film 13 reflects the laser light L,
The optical axis of the laser light L is changed by about 90 degrees to guide the laser light L onto the optical disc D.

The lens suspension 3 supports the condenser element 2 so that the distance between the condenser element 2 and the optical disk D becomes a predetermined distance. The operation of the lens suspension 3 is controlled by, for example, a drive mechanism (not shown), and the condenser element 2 is moved to a predetermined position on the optical disc D.

When recording / reproducing information signals on / from an optical disc D of a so-called multi-value recording system with the optical head 1 thus constructed, first, a laser beam L having a plurality of wavelengths is emitted from a light source and condensed. The reflective film 13 of the element 2 is irradiated. Then, the condensing element 2 configured as described above changes the incident laser light L from the optical axis L1 to L2, and condenses the laser light L having the optical axis L2 onto the optical disc D. Irradiate. As a result, the optical head 1 forms the spot S on the optical disc D on which the laser light L having a plurality of wavelengths is condensed.

A manufacturing process of the light-collecting element 2 provided in the optical head 1 thus constructed will be described with reference to FIG. Note that FIG. 2 shows a sectional view and a front view when manufacturing the light-collecting element 2.

When manufacturing the condensing element 2, first, a glass substrate is prepared, and as shown in FIG. 2A, a part of the glass substrate is processed and molded to form a concave surface portion 12 having a predetermined curvature.
To form.

Next, as shown in FIG. 2B, a reflective film 13 is formed on the concave surface portion 12 formed in the above-mentioned process by, for example, a sputtering method.

According to such an optical head 1, even when the laser light L having a plurality of wavelengths is incident, the optical axis of the incident laser light L is changed from L1 to L2. Since L is condensed on the optical disc D, the spot S can be formed on the optical disc D without utilizing the refraction of light. Therefore, according to the optical head 1, it is possible to form the minute spot S by the laser light having a plurality of wavelengths without causing the chromatic aberration generated by the laser light having a plurality of wavelengths.

Further, according to this condensing element 2, since the spot S can be formed without depending on the wavelength contained in the laser light, the optical component for forming the spot S is adjusted to the wavelength of the laser light L. Accordingly, it is not necessary to design it, and the number of parts can be reduced.

Next, a condensing element provided in another optical head to which the present invention is applied will be described with reference to FIG.

The condensing element 20 shown in FIG. 3 includes a light-incident material 21 which is emitted from an external light source and receives laser light L11 having a plurality of wavelengths, and a light emission which condenses and emits the laser light. And a material 22.

The light incident material 21 is made of, for example, a glass material having a predetermined refractive index and is processed and molded to form the convex surface portion 31 and the concave surface portion 32. The light incident material 21 includes a convex mirror portion 33 having a convex surface portion 31 formed with a reflective film such as Al, and a concave mirror portion 34 having a concave surface portion 32 formed with a reflective film made of a light reflecting material such as Al. Has been formed.

Here, the convex surface portion 31 is formed with a curvature such that the laser light L11 incident from the light incident surface 21a is reflected as the laser light L12 traveling from the convex mirror portion 33 toward the concave mirror portion 34. There is. In addition, the concave portion 32
Is the laser beam L12 reflected from the convex mirror section 33.
Is formed so as to have a curvature so as to be reflected as the laser light L13 traveling from the concave mirror portion 34 toward the light emitting surface 22a. The light incident surface 21a has a planar structure,
The laser light L11 enters perpendicularly to the light incident surface 21a.

The light emitting material 22 is joined to the light incident material 21 via the connecting portion 41. This light emitting material 22 is
It is made of a glass material having the same predetermined refractive index as the light incident material 21. The light emitting material 22 is formed into a cylindrical shape having substantially the same diameter as the light incident material 21 and is joined to the light incident material 21 so that the laser beam L13 from the light incident material 21 is incident. There is.

The connecting portion 41 for joining the light emitting material 22 and the light incident material 21 is preferably made of an adhesive having the same predetermined refractive index as the light emitting material 22 and the light incident material 21.

The laser light L11 emitted toward the light-collecting element 20 having the above-described structure enters through the light incident surface 21a. Next, the laser light L11 is applied to the convex mirror portion 33.
The optical axis is refracted by being reflected by the laser beam L1.
It becomes 2.

The laser beam L12 has an optical axis extending from the convex mirror section 33 to the concave mirror section 34 and is incident on the concave mirror section 34. Next, the laser light L12 is reflected by the concave mirror portion 34, so that the optical axis is refracted and becomes the laser light L13.

The laser light L13 has an optical axis extending from the concave mirror portion 34 toward the light emitting material 22 and is focused so as to form a spot S on the light emitting surface 22a of the light emitting material 22. Thereby, the laser beam L13 forms the spot S having a plurality of wavelengths.

The manufacturing process of such a condensing element 20 will be described with reference to FIG.

When manufacturing the condensing element 20, first,
A cylindrical glass material is prepared and, as shown in FIG. 4A, the side surface and the bottom surface thereof are processed and formed to form the hemispherical convex surface portion 31 and the concave surface portion 32.

Next, as shown in FIG. 4B, a convex mirror portion 33 is formed by forming a reflective film on the convex surface portion 31 and the concave surface portion 32 formed in the above-described process by, for example, a sputtering method.
And the concave mirror portion 34.

Next, as shown in FIG. 4C, the light emitting material 22 is bonded to the surface side facing the light incident surface 21a through the connecting portion 41 to manufacture the light collecting element 20.

According to the optical head 1 having such a condensing element 20, even when the laser light L11 having a plurality of wavelengths is incident, the incident laser light L11 is reflected by the convex mirror portion 33. Since the laser beam L12 can be formed into the laser beam L12 and then the laser beam L12 can be reflected by the concave mirror portion 34 to form the spot S as the laser beam L13, the spot S can be formed on the light emitting surface 22a without utilizing the refraction of light. Can be formed. Therefore, according to the condensing element 20, it is possible to form the minute spot S by the laser light having a plurality of wavelengths without causing the chromatic aberration generated by the laser light having a plurality of wavelengths.

Further, according to the optical head 1 provided with this optical element 20, the spot S can be formed without depending on the wavelength included in the laser beam L11. Therefore, an optical component for forming the spot S can be provided. It is not necessary to design according to the wavelength included in the laser light L11, and the number of parts can be reduced.

[0044]

As described above in detail, the optical head according to the present invention has the first incident surface on which light having a plurality of wavelengths is incident and the first emitting surface on which the incident light is emitted. An incident portion having a convex mirror surface portion that reflects light incident from the first incident surface and a concave mirror surface portion that reflects light reflected by the convex mirror surface portion to the first emission surface. And an emission part including a second incidence surface on which the light reflected by the concave mirror surface portion is incident and a second emission surface on which the light incident from the second incidence surface is emitted to the optical disc. The first exit surface is in close contact with the second entrance surface, and the concave mirror surface portion collects light on the second exit surface.
The light can be condensed on the recording medium only by the reflection of the light without using the refraction of the light, and the light can be condensed on the recording medium without causing the chromatic aberration caused by the incidence of the light of plural wavelengths. Can be focused on.

[0045]

[Brief description of drawings]

FIG. 1 is a sectional view for explaining a configuration of an optical head to which the present invention is applied.

FIG. 2 is a diagram for explaining a manufacturing process of the light converging element provided in the optical head to which the present invention is applied, FIG.
FIG. 4A is a sectional view and a front view showing the formation of a concave portion on a glass substrate, and FIG. 7B is a sectional view and a front view showing the formation of a reflective film on the concave portion.

FIG. 3 is a sectional view showing another condensing element provided in the optical head to which the present invention is applied.

FIG. 4 is a diagram for explaining a manufacturing process of another condensing element provided in the optical head to which the present invention is applied,
(A) is sectional drawing which shows forming a convex part and a concave part in a glass substrate, (b) forms a convex mirror part and a concave mirror part 34 by forming a reflective film in a convex part and a concave part. It is a sectional view shown, (c) is a sectional view showing joining a light emitting material.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 optical head, 2 light condensing element, 11 substrate part, 12 concave surface part, 13 reflective film, 20 light condensing element 31 convex surface part, 3
2 concave surface section, 33 convex mirror section, 34 concave mirror section

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-64-39642 (JP, A) JP-A-6-214154 (JP, A) JP-A-11-238238 (JP, A) JP-A-8- 180453 (JP, A) JP 63-313329 (JP, A) JP 2-214033 (JP, A) JP 5-225601 (JP, A) JP 10-162413 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B ⁷ /12-7/135 G02B 13/00-13/18

Claims (2)

(57) [Claims] 1. A first incident surface that allows light having a plurality of wavelengths to enter, and a first exit surface that exits the incident light, and reflects light that has entered from the first entrance surface. An incident portion including a convex mirror surface portion and a concave mirror surface portion that reflects the light reflected by the convex mirror surface portion to the first emission surface, and a second portion that inputs the light reflected by the concave mirror surface portion. Of light and an emission part including a second emission surface for emitting the light incident from the second incidence surface to the optical disc, the first emission surface being the same as the second incidence surface. An optical head which is in close contact with the concave mirror surface portion and collects light on the second emission surface. 2. The optical head according to claim 1, wherein the entrance portion and the exit portion are made of the same material.