JPS60214432A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain a practical optical information recording and reproducing device with excellent reliability by providing an optical beam strength adjusting means at recording or reproduction and an optical beam irradiation energy adjusting means for irradiating an optical beam to a prescribed track of a medium, applying tracking control in standby. CONSTITUTION:An optical beam from a semiconductor laser 1 is formed into parallel light by a lens 2 and condensed on a disc 10 through a half mirror 3, a 1/4lambda plate 5' and an objective lens 6. The reflected light is received by a photodetector 8 at the half mirror 3 through the lens 6 and the 1/4lambda plate 5' again, and the information recording on the disc 10 is detected and tracking control is applied. A drive circuit 11 driving a semiconductor laser 1 applies a desired drive signal to a semiconductor laser by using the 1st optical beam irradiating energy adjusting means 12 in the standby state selected depending on the standby, recording and reproduction, the 2nd optical beam irradiating strength adjusting means 13 selected at recording and the 3rd optical beam irradiation strength adjusting means 14 selected at reproduction to obtain an oscillated output.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an optical information recording/reproducing apparatus for recording and reproducing information by irradiating a disc-shaped optical recording medium with a light beam emitted from a laser oscillator or the like. Alternatively, the present invention relates to an optical information recording and reproducing apparatus that waits for a recording and reproducing operation while controlling tracking of a predetermined track by irradiating a light beam onto a medium before and after a reproducing operation.

Prior Art and Problems In general, optical information recording and reproducing devices perform a recording operation in which a light beam is modulated to be strong or weak depending on the information to be recorded, and is focused on a predetermined position on a recording medium to record information on the medium. , optical recording and reproduction of a large amount of information at high density is performed by a reproduction operation that non-destructively reproduces information recorded at a predetermined position on a medium. In particular, in the above-mentioned reproduction operation, it is extremely important to reproduce the information recorded on the medium without error and to reproduce the information non-destructively.

However, when the laser beam from a laser oscillator is used as the light beam, quantum shot noise, emission threshold noise, or noise due to interference due to reflected light from the medium is generated during low-output oscillation, resulting in fluctuations in the output and deterioration of the reproduced signal. It has the disadvantage of worsening the shedding ratio. An example of a semiconductor laser will be explained below. FIG. 1 shows the relationship between the oscillation output and forward drive current of a semiconductor laser, where the horizontal axis shows the drive current and the vertical axis shows the oscillation output. In the diagram, the area (a) is the LED area, and (b)
indicates a laser oscillation region with excellent coherency, and in the example shown in Fig. 1, the oscillation threshold current for starting laser oscillation is approximately 6
0 mA. Figure 2 shows the relationship between the oscillation output of the semiconductor laser and the noise (output fluctuation) generated in the oscillation output, which was actually measured using the measurement optical system shown in Figure 3, which will be described later. The horizontal axis is the laser oscillation output, and the vertical axis is the oscillation output. shows the amount of noise generated in each case. The large noise generated in the low output oscillation region in FIG. 2 corresponds to the area near the oscillation threshold in the laser oscillation region (b) in FIG. 1, and it can be seen that the noise decreases as the oscillation output increases. Such noise causes fluctuations in the optical beam intensity during the reproduction operation, resulting in a problem of deteriorating the Sβ ratio of the reproduced signal and increasing the error rate during reproduction. In order to solve this problem, it is necessary to obtain a good common ratio of the reproduced signal by setting the oscillation output to a sufficiently large value that does not include the above-mentioned noise (in the example of Fig. 2, the oscillation output is 1 mW or more). I am by.

FIG. 3 shows a measurement optical system for detecting the above noise.

The light beam of the semiconductor laser 1 is made into a parallel beam by a collimator lens 2, and one part is received by a photodetector 9 for semiconductor laser noise measurement by a mirror 3, and the other part passes through a polarizing beam splitter 4 and a rotating V4λ plate 5. Rear, condenser lens 6
The reflected light is focused on the mirror 1 that vibrates in the axial direction of the optical axis, and the reflected light passes through the lens 6, the V4λ plate 5, and the polarizing beam splitter 4 again, and a part of the light is returned by the 8-7 mirror 3 for measurement of the returned light. A portion of the light passes through the photodetector 8 and the lens 2 and then reaches the semiconductor laser 1 .

On the other hand, thermoplastic optical recording materials, amorphous optical recording materials, magneto-optical recording materials such as MnB1, etc. are used as the recording medium of the above-mentioned optical information recording/reproducing device, but these recording materials have unique optical properties. Information is recorded on the medium or reproduced by utilizing the fact that physical properties change in response to the energy of the irradiated light beam. As a result, even a low-power light beam can be used for a long time. It has been known that continued irradiation of the same track on the medium over time can cause changes in the recording material and damage the medium. This relationship is shown in FIG.

FIG. 94 shows the noise increase characteristic of the reproduced signal when two predetermined tracks C are continuously irradiated with a light beam of constant intensity. The horizontal axis shows the tracking time during which tracking control is performed by irradiating the same track with a light beam, and the vertical axis shows the increase in the amount of noise generated in the reproduced signal as a result of the continuous tracking.

The oscillation output of the semiconductor laser is 1.25 mW, (B
) is 15 mW, (C) is 1.75 mW, (D) is 2
The noise increase characteristics are shown for each mW, and (3) in this figure shows that even at an oscillation output of 1.25mW
By irradiating the same track with a light beam for 100 hours,
It can be seen that the amount of noise in the reproduced signal increases and begins to damage the medium. Note that the oscillation output in (A) above corresponds to the part where the threshold noise has decreased in FIG. It has been shown that this causes a problem of deteriorating the 9-ratio of the signal.

In order to solve the above-mentioned contradictory problems, conventionally a filter is inserted in the middle of the optical system, and a laser beam with sufficient oscillation output that does not generate the noise during reproduction is attenuated by the filter and irradiated onto the medium. Methods have been proposed to obtain reproduction signals with a good S/N ratio, but the life of the laser itself is shortened due to high-output laser oscillation, and the structure of the optical information recording and reproducing device including the optical system is affected. Further problems such as complication arise, resulting in many practical drawbacks.

Purpose of the Invention The purpose of the present invention is to focus on the limitations of the above-mentioned prior art,
In an optical information recording and reproducing device that records and reproduces information with high density and large capacity, a light beam intensity adjustment means and a light beam irradiation device that performs tracking control and waits by irradiating a light beam onto a predetermined track of a medium during recording or reproduction. By providing energy adjustment means, the present invention aims to provide a highly reliable and practical optical information recording/reproducing device.

Composition of the invention Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 5 is a diagram showing a schematic configuration of the main parts of the optical information recording/reproducing apparatus according to the present invention. The light beam from the semiconductor laser 1 is turned into parallel light by the lens 2 and is converted into a parallel beam by the half mirrors 3 and 1.
The light passes through the /4λ plate 5' and the objective lens 6 and is focused onto the disk 10. The reflected light passes through the lens 6 and the V4λ plate 5' again and is received by the photodetector 8 by the half mirror 3, where information recorded on the disc 10 is detected and tracking control is performed. A drive circuit 11 that drives the semiconductor laser 1 includes a first light beam irradiation energy adjustment means 12 during standby and a second light beam irradiation intensity adjustment means during recording, which are selected according to each operation of standby, recording, and reproduction. Means 13
During reproduction, a desired drive signal is applied to the semiconductor laser by the third light beam irradiation intensity adjusting means 14, and an oscillation output can be obtained. The first light beam irradiation energy adjusting means 12 of the present invention continuously operates the semiconductor laser at an output lower than the light beam irradiation intensity obtained by driving the semiconductor laser 1 by the third light beam intensity adjusting means 14. Alternatively, a circuit configuration that causes a semiconductor laser to oscillate in a modulated oscillation state having a peak light intensity comparable to the optical beam intensity obtained by the third light beam intensity adjusting means 14 may be used. Good too.

According to the optical information recording/reproducing apparatus configured as described above, in a state of waiting for recording or reproduction of necessary information,
The first light beam is a light beam with sufficiently low irradiation energy to enable tracking control on a predetermined track without destroying information recorded on the medium or leaving unnecessary tracking traces on an unrecorded medium. The beam irradiation energy adjustment means 12 causes the semiconductor laser 1 to oscillate via the drive circuit 11, and the reflected light or transmitted light from the medium is detected by the photodetector 8, and predetermined tracking control is performed while the next recording or reproduction is performed. Can wait for instructions for a long time.

In addition, in response to a recording or reproduction command, the second light beam intensity adjusting means 13 at the time of recording, such as a semiconductor laser, modulates the signal to be recorded via the drive circuit 11 and generates sufficient oscillation output to record information on the medium. or oscillate in an oscillation output range with a good S/N ratio and less threshold noise by the third light beam intensity adjustment means 14 during reproduction,
Optimal recording or playback can be performed.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, in an optical information recording and reproducing apparatus that records and reproduces information by irradiating a light beam onto a disk-shaped optical recording medium, when waiting for a command to record or reproduce information, has a first light beam irradiation energy adjustment means for irradiating a low energy light beam that does not damage the medium even if the light beam is irradiated onto the same track for a long time; It is equipped with a second light beam intensity adjustment means that stably and reliably records information on the medium, and during reproduction, a third door that irradiates a high quality light beam with less fluctuation in light intensity inherent to low output light beams. By providing a light beam intensity adjustment means, a reproduced signal with a good ratio can be obtained, and by selecting each appropriately,
A highly reliable and practical optical information recording/reproducing device can be provided.

In the above-mentioned embodiments, an optical information recording and reproducing device capable of recording and reproducing was explained as an example, but it is of course possible to apply the technical idea of the present invention to an optical information recording device or an optical information reproducing device. Yes, it does not depart from the present invention. Moreover, the specific configurations of the first light beam irradiation energy adjustment means, the second light beam intensity adjustment means, the third light beam intensity adjustment means, and the drive circuit can be freely configured within the technical scope of the present invention. It is something.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram of the oscillation output and drive current of a semiconductor laser.
Figure 2 is a diagram of output noise characteristics of a semiconductor laser, Figure 3 is a schematic diagram of the optical system for measuring noise characteristics, Figure 4 is a diagram of noise increase characteristics due to tracking of the medium, and Figure 5 is an optical information recording according to the present invention. The main part configuration diagram of the playback device is shown. 1...Semiconductor laser 2...Collimator lens 3...Eight mirror 4...Polarizing beam splitter 5...Rotating V4λ plate 5 '...v4λ plate B...Condensing lens 7...Mirror 8...Photodetector for measuring returned light B...Noise measurement Photodetector 10...Disk 11...Drive circuit 12...Light beam irradiation energy adjustment means 13
. . . Light beam intensity adjustment means 14 . . . Light beam intensity adjustment means Fig. 1 0501o. ...11S L14 Takumaru (“4) Figure 2 do1 Shooting method (mWl

Claims (4)

[Claims] (1) Optical information recording and reproducing device that records or reproduces information by irradiating a light beam onto a disk-shaped recording medium (=
means for irradiating a light beam; a first light beam irradiation energy adjusting means for waiting while irradiating a predetermined track of a medium with a light beam; and a first light beam irradiation energy adjusting means for irradiating a predetermined position of a medium with a light beam to record information. 1. An optical information recording/reproducing apparatus comprising: a second light beam intensity adjusting means; and/or a third light beam intensity adjusting means for reproducing recorded information by irradiating a medium with a light beam. (2) The optical information recording and reproducing apparatus according to claim 1, wherein the means for irradiating the light beam is a light source such as a semiconductor laser. (3) The first light beam irradiation energy adjusting means is 1
．． 2. The optical information recording and reproducing apparatus according to claim 1, wherein the optical information recording and reproducing apparatus is configured to irradiate a light beam with a lower intensity than the light beam intensity irradiated by the third light beam intensity adjusting means. (4) The first light beam irradiation energy adjustment means:
The light according to claim 1, further comprising modulated light beam generation control means for emitting a light beam with lower intensity than the light beam energy emitted by the third light beam intensity adjustment means. Information recording and reproducing device.