JPH06180853A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To provide a super resolution optical information recording and reproducing device without deteriorating the availability of light and always forming an excellent super resolution beam spot even when an objective lens is moved. CONSTITUTION:This device is provided with a polarizing beam splitter 2 distributing a laser beam outgoing from a laser diode 1 to a specified polarizing component and a polarized wave transmission selection means 3 interrupting the beam in the vicinity of the optical axis only at the time of being incident to the objective lens 4 from a laser diode side, and capable of preventing the deterioration in the avilability of light by transmitting even the beam in the vicinity of the optical axis for a reflected beam from an information recording medium 6. Further, the device is provided with an actuator 5 capable of driving the polarized wave transmission selection means 3 and the objective lens 4 at least to two axes by the same holding body as well. By such a constitution, the formation of the excellent super resolution beam spot and the recording and reproducing of information with high density are attained always even when the objective lens 4 is moved.

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 information input / output device for recording / reproducing information using light.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional super-resolution optical information recording / reproducing apparatus.

The basic structure is a laser diode 1 which emits a laser beam which is a laser source, a light blocking plate 9 which blocks light near the optical axis, a beam splitter 2 which branches the laser beam, and an objective lens 4 which condenses the laser beam. It comprises an actuator 5 for driving the objective lens and a photodiode 7 which is a light receiving element for converting the returned light into an electric signal.

The laser light emitted from the laser diode 1 passes through a light shielding plate 9 having a light shielding region in the vicinity of the optical axis to become a laser light in the vicinity of the optical axis and goes to the beam splitter 2. The laser light transmitted through the beam splitter 2 is focused on the information recording medium 6 by the objective lens 4. At this time, the beam spot 11 can have a smaller beam diameter than that of the normal spot 10 without the light shielding plate due to the super-resolution effect of light shielding near the paraxial (φb).
<Φc). The laser light reflected by the information recording medium 6 passes through the objective lens 4 again and is reflected by the beam splitter 2.
Go to the photodiode 7. It is converted into an electric signal by the photodiode 7, and a reproduction signal and an error signal are obtained by the signal reproduction circuit.

With the above structure, it is possible to record and reproduce high-density information using a super-resolution light beam.

[0006]

In the structure described above, in order to efficiently guide the return light from the information recording medium to the photodiode, the light shielding plate is provided between the laser diode and the beam splitter in the outward path of the optical path system. Must be placed. Therefore, when the objective lens moves in the track direction, the center of the light blocking plate and the optical axis of the laser beam are deviated from each other, and a good super-resolution beam cannot be obtained.

FIG. 4 shows the above explanatory diagram. When the objective lens 4 moves by f as shown in the figure, the super-resolution beam spot 12
Cannot obtain a good beam.

An object of the present invention is to provide a super-resolution optical information recording / reproducing apparatus which always forms a good super-resolution beam spot even when the objective lens moves, without lowering the light utilization efficiency.

[0009]

In order to achieve the above-mentioned object, the present invention provides a laser source for emitting a laser beam,
A polarization beam splitter that transmits or reflects the laser light emitted from the laser source and the return light from the information recording medium, and a polarization separation plate having a polarization wave transmission selection area that blocks only polarization waves in a specific direction in the vicinity of the optical axis, , A λ / 4 plate, a polarized light transmission selecting means, an objective lens for converging the laser light transmitted through the polarized wave transmission selecting means on an information recording medium in super-resolution, and the objective lens for focusing and tracking. An actuator for driving in at least two axial directions, and a light receiving element for converting the laser light reflected by the polarization beam splitter by the return light from the information recording medium into an electric signal, wherein the actuator comprises: The polarization wave transmission selecting means and the objective lens can be driven in at least two axes by one holding body. Selection means, the polarization separating plate and lambda / 4 plate is characterized in that it is integral.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing an optical system according to the present invention. The laser beam emitted from the laser diode 1 is separated into linearly polarized P wave and S wave by the polarization beam splitter 2, and only the P wave goes to the objective lens 4. The laser light is incident on the polarized wave transmission / selection means 3 which is simultaneously held by the lens holder 5 of the actuator together with the objective lens 4. Here, the polarized wave transmission / selection means 3 is composed of a polarized light separation plate 3a having a polarized wave transmission / selection region 3c formed of, for example, a polarization film near its center and a λ / 4 plate 3b for converting linearly polarized light into circularly polarized light. .

At this time, in order to completely block the linearly polarized P wave near the optical axis which is incident on the polarized wave transmission / selection region, the rotation direction of the polarized wave transmission / selection means 3 with respect to the optical axis 0-0 '. Set the mounting angle. As a result, as for the linearly polarized P-wave, only the light other than the polarized-wave transmission selection area 3c remains as it is.
It is incident on b.

The linearly polarized P wave from which the light in the vicinity of the optical axis is removed is converted into circularly polarized light by passing through the λ / 4 plate 3b, is condensed by the objective lens 4, and is super-resolved on the information recording medium 6. Form a beam spot. The reflected light from the information recording medium 6 becomes circularly polarized light in the opposite direction to that at the time of incidence due to reflection, passes through the objective lens 4, and is incident again on the polarized wave transmission / selection means 3. Since the circularly polarized light is incident on the λ / 4 plate 3b in the opposite direction to that at the time of incidence, linearly polarized light rotated by 90 ° from that at the time of incidence, that is, S wave in this case, is incident on the polarization separation plate 3a.

Therefore, in the laser light, all the light including the polarized wave transmitting / selecting region 3c is transmitted through the polarization separating plate 3a, and in the next polarization beam splitter Z, on the contrary, most of the light is on the photodiode 7 side. Will be reflected. With the above configuration, it is possible to always generate a good super-resolution beam spot even when the objective lens moves and realize recording / reproduction of high-density information without lowering the light use efficiency.

FIG. 2 shows an embodiment of an integrated type polarized wave transmission / selection means. In this figure, an integrated type is formed by forming a polarized wave transmission / selection region with, for example, a polarization film near the center of a λ / 4 plate. It realizes the polarized wave transmission selection means.

[0015]

As described above, the present invention has the polarized wave transmission / selection means utilizing the polarization of the laser beam and the means for driving the polarized wave transmission / selection means and the objective lens with the same holder. Thus, there is an effect that it is possible to follow a track and to always form a good super-resolution beam spot and record / reproduce high-density information even when the objective lens is moved during access without lowering the light utilization efficiency. .

[Brief description of drawings]

FIG. 1 is an optical path diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing an embodiment of an integrated polarized light wave transmission selection means in the present invention.

FIG. 3 is an optical path diagram of a conventional super-resolution optical information recording / reproducing apparatus.

FIG. 4 is an optical path diagram illustrating a problem in the conventional technique.

[Explanation of symbols]

 1 Laser Diode 2 Polarization Beam Splitter 3 Polarization Wave Transmission Selection Means 3a Polarization Separation Plate 3b λ / 4 Plate 3c Polarization Wave Transmission Selection Area 4 Objective Lens 5 Biaxial Actuator 6 Information Recording Medium 7 Photodiode 8 1 Body Type Polarization Wave Transmission Selection Means 9 Light-shielding plate 9a Light-shielding area 10 Normal beam spot 11 Super-resolution beam spot 11a Main beam 11b Side lobe 12 Super-resolution beam spot when moving the optical axis

Claims (3)

[Claims] 1. A laser source for emitting a laser beam, a polarizing beam splitter for transmitting or reflecting the laser beam emitted from the laser source and a return beam from an information recording medium, and a polarized wave in a specific direction near the optical axis. A polarization separation plate having a polarization wave transmission selection area for blocking only the above, a polarization wave transmission selection means composed of a λ / 4 plate, and a laser beam transmitted through the polarization wave transmission selection means on an information recording medium in super-resolution. An objective lens that emits light, an actuator that drives the objective lens in at least two axis directions of a focus and a track, and light receiving that converts the laser light reflected by the polarization beam splitter by return light from the information recording medium into an electric signal An optical information recording / reproducing apparatus comprising: an element. 2. The optical information recording / reproducing apparatus according to claim 1, wherein the actuator is capable of driving the polarized wave transmission selecting means and the objective lens in at least two axes with a single holding body. 3. The optical information reproducing apparatus according to claim 1, wherein the polarized wave transmission / selection means has a polarization separation plate and a λ / 4 plate integrated with each other.