JPS61184741A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To correct the writing current only at a single point by providing a rotating element and a polarized beam splitter into an optical path reaching an optical disk from a light source and therefore controlling the optical power for writing to the optical disk to different levels at the inner and outer circumference parts. CONSTITUTION:A collimator lens 2, a prism 3, a rotating element 4, a polarized beam splitter 5, a lambda/4 plate 6 and an objective lens 7 are provided between a semiconductor laser beam source 1 and an optical disk 8 serving as a recording medium. A servo and information detecting system 9 is set at the side of the beam splitter 5. In a writing mode the light delivered from the light source 1 is changed into parallel beams by the lens 2 and focused on the disk 8 by the lens 7 through the rotating element 4, the beam splitter 5 and the plate 6 after undergoing the right circle correction through the prism 3. In this case, the writing power IW delivered from the source 1 is kept constant with no change. Then the difference of the writing power between the inner and outer circumference parts of the disk 8 is controlled by the rotating element 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording/reproducing apparatus, and more particularly to an optical recording/reproducing apparatus that controls laser writing power.

Optical recording/reproducing devices are attracting attention in the information processing field because their recording medium, an optical disk, is compact and easy to handle, and because they do not wear out, they can be used semi-permanently.

Conventionally, optical recording and reproducing devices have used separate optical systems for recording and optical systems for reproducing. Therefore, the light sources used to be separate, but now the same light source is being used due to the simplification of the optical system.

[Conventional technology]

Conventionally, a drive circuit for a laser diode used as a reproduction light source has been equipped with an auto power control (APC) circuit that uses the monitor light to control the drive current in order to keep the optical power output from the laser diode constant. There is. However, when I try to record with this light source,
Because of the APC, the bias current changes and the predetermined power cannot be produced.Therefore, a drive circuit as shown in Fig. 3 has been devised that subtracts a current proportional to the recording current from the monitor light. APC bias current IB flows through the light source LD.A write current Iw is added thereto.When the current Is for the write current is subtracted from the monitor pin photodiode PD, the bias current rB does not change.For this reason, the power is always constant. becomes constant.

[Problem that the invention seeks to solve]

The above configuration has the following problems. That is, the power for recording on the optical disc needs to be changed depending on the difference in peripheral speed between the inner and outer circumferences of the optical disc. However, when the write current I- is changed in the circuit shown in FIG. 3, it is natural that Is must also be made proportional. In order to have this proportional relationship, it is necessary to increase the power supply voltage.

[Means for solving problems]

The present invention provides an optical recording/reproducing device which solves the above-mentioned problems, and includes a circuit that detects and makes constant the intensity of laser light output from a laser light source, and a circuit that supplies a recording current to the laser light source. In an optical recording/reproducing device, the current corresponding to the recording current is subtracted from the laser light intensity detection unit according to each bit, and is recorded on the optical disc, which is a recording medium. This is accomplished by an optical recording/reproducing device characterized in that an optical rotator and a polarizing beam splitter are inserted into the optical path of the optical disc, and the recording power is controlled by the optical rotator and the polarizing beam splitter according to the recording speed of the inner and outer circumferences of the optical disc. .

[For production]

The above optical recording/reproducing device inserts an optical rotator and a polarizing beam splitter in the optical path from the laser light source to the optical disk, and uses the optical rotator and polarizing beam splitter to make the optical power written on the optical disk different between the inner and outer circumferences. By controlling the write current, it is possible to correct the write current while keeping the optical power emitted from the light source constant, and there is no need to increase the power supply voltage of the power supply drive circuit.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a configuration diagram of an embodiment of the present invention.

In this embodiment, as shown in FIG. 1, a collimating lens 2 is provided between a semiconductor laser light source 1 and an optical disk 8 which is a recording medium.
, prism 3, optical rotator 4, polarization beam splitter 5, λ
A /4 plate 6 and an objective lens 7 are arranged in sequence, and a servo and information detection system 9 are arranged on the side of the polarizing beam splitter. Note that the light source 1 has a drive circuit shown in FIG.

In this embodiment configured in this way, the light emitted from the semiconductor laser light source 1 is transmitted through the collimating lens 2 during writing.
The light is made into parallel light by the prism 3 and corrected for perfect circularity by the prism 3, and then passes through the optical rotator 4, the polarizing beam splitter 5, and the λ/4 plate 6, and is focused onto the optical disk 8 by the objective lens 7. In this case, the key point of the present invention is to keep the writing power Iw emitted from the light source constant without changing it, and to adjust the difference in writing power between the inner and outer circumferences of the optical disc 8 by controlling the optical rotator 4. FIG. 2 is a diagram showing the state of transmission and reflection of light controlled by the optical rotator 4 at the polarizing beam splitter 5, where straight line A is the inner circumference and straight line B is the outer circumference. Since the circumferential speed of the optical disk is slow at the inner circumference, the polarization beam splitter increases reflection and reduces transmission, while at the outer circumference, control is performed using an optical rotator to reduce reflection and increase transmission. It shows.

For reading, the reflected light from the optical disk 8 returns through the objective lens 7 and the λ/4 plate 6, is reflected by the polarizing beam splitter 5, and enters the servo and information detection system 9, where the information is read.

〔Effect of the invention〕

As explained above, according to the present invention, an optical rotator and a polarizing beam splitter are inserted in the optical path from the light source to the optical disk, and the optical power written on the optical disk is made different between the inner and outer circumferences by the optical rotator and the polarizing beam splitter. By controlling, the write current can be corrected at only one point, and there is no need to increase the power supply voltage as in the conventional case.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the optical recording/reproducing device of the present invention, Fig. 2 is a diagram showing transmission and reflection of light controlled by an optical rotator in a polarized beam brick, and Fig. 3 is a diagram showing a semiconductor laser. FIG. 2 is a block diagram showing a driving circuit for a light source. In the figure, l is a semiconductor laser light source, 2 is a collimating lens,
3 is a prism, 4 is an optical rotator, 5 is a polarizing beam splinter, 6 is a λ/4 plate, 7 is an objective lens, 8 is an optical disk, 9
indicate the servo and information detection systems, respectively.

Claims (1)

[Claims] 1. It has a circuit that detects the intensity of the laser light output from the laser light source and makes it constant, and a circuit that superimposes the recording current on the laser light source, and the laser light intensity detector detects the current corresponding to the recording current for each bit. In an optical recording and reproducing apparatus that records on an optical disk, which is a subtractive recording medium, an optical rotator and a polarizing beam splitter are inserted in the optical path from the laser light source to the optical disk, and An optical recording/reproducing device characterized by controlling recording power according to the recording speed of the inner and outer circumferences of an optical disc.