JPS61258335A - Disk device - Google Patents

Abstract

PURPOSE:To detect both recorded and unrecorded areas of information in a reproduction mode and also to avoid completely the double writing to the recorded area of information in a record mode, by detecting and comparing the reflection factors of the beams reflected from a disk. CONSTITUTION:In a record mode of information, a reference voltage signal Va of a low level is delivered in a response to the recording beam. While a reference voltage signal Vb of a high level is delivered in response to the reproduction beam. These signals Va and Vb are compared with the signal (video signal) corresponding to the reflected light by a comparator 34. Thus the double writing can be detected accurately. Furthermore the signal Va corresponding to the reproduction beam is compared with the signal corresponding to the reflected light in a reproduction mode. Thus both the recorded and unrecorded areas of information can be detected accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a disk device such as an optical disk device that at least records and reproduces information on, for example, an optical disk.

[Technical background of the invention and its problems] Recently, an optical disk device has been developed that records and reproduces information on the recording film of an optical disk using a focused laser beam output by oscillation of a semiconductor laser oscillator. There is.

Incidentally, in such an optical disk device, a signal (video signal) from a photodetector that converts reflected light from an optical disk into an electric signal is compared with a reference voltage signal to detect whether information has been recorded or not. By doing so, it is possible to prevent double writing of information. However, due to the influence of the returning light, the video signal during information writing exceeds the reference voltage signal even though it is an unrecorded area, resulting in a false detection of the presence or absence of information, and a second error in the information recording area. There was a problem that it could not be used to prevent overwriting.

That is, there is a problem in that the video signal exceeds the reference voltage signal due to the return light generated by the bits that have just been recorded.

[Purpose of the Invention] This invention was made in view of the above circumstances, and its purpose is to be able to detect recorded and unrecorded areas of information when reproducing information, and to detect areas where information has been recorded when recording information. To provide a disk device that can reliably detect double writing to an area and prevent double writing.

[Summary of the Invention] In order to achieve the above object, the present invention records or reproduces information on a disk using focused light, in which light emitted from a light source is focused on the disk, The reflected light from the disk due to the focusing is converted into an electric signal by the conversion means, and the reference voltage output means outputs a different reference voltage signal depending on when the light corresponding to recorded information is emitted from the light source and at other times. , the electric signal converted by the conversion means and the reference voltage signal from the reference voltage output means are compared, and the detection means detects a reflectance for detecting double writing of information according to the comparison result. This is what I did.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings.

The drawings schematically show the configuration of an optical disc device of the present invention. That is, the optical disk 11 is rotated by the motor 12 with respect to the optical head 13 at a constant linear velocity. The optical disc 11 has a circular substrate made of, for example, glass or plastic, and the surface of the substrate is coated with a donut-shaped metal film layer, ie, a recording film, made of tellurium or bismuth.

An optical head 13 for recording and reproducing information is provided on the back side of the optical disc 11. This optical head 13 is constructed as follows. That is, 14
1 is a semiconductor laser oscillator for recording and reproducing, and this semiconductor laser oscillator 14 generates a diverging laser beam. In this case, when writing information to the recording film (not shown) of the optical disc 11, a laser beam beam whose light intensity is modulated (high luminous intensity) according to the information to be written is generated, and the information is read from the recording film. In this case, a laser beam with a constant light intensity (degree of polarization) is generated. The diverging laser beam generated by the semiconductor laser oscillator 14 is converted into a parallel beam by a collimator lens 15 and guided to a polarizing beam splitter 16 . The laser beam guided to this polarizing beam splitter 16 is reflected by this polarizing beam splitter 16, passes through a 1/4 wavelength plate 17, and enters an objective lens 18, which records information on the optical disc 11. focused towards the membrane.

Here, the objective lens 18 is supported movably in the direction of its optical axis and in the direction (radial direction) perpendicular to the optical axis, and when the objective lens 19 is positioned at a predetermined position, the objective lens 19 The beam waist of the focused laser beam emitted from the recording film is projected onto the surface of the recording film, and a minimum beam spot is formed on the surface of the recording film. In this state, the objective lens 18 is maintained in a focused state (focusing) and a focused tracking state (tracking), and information can be read and recorded. When writing information, bits are formed on a tracking guide on the recording film by a laser beam whose intensity is modulated.
When reading information, a laser beam having a constant light intensity (degree of polarization) is modulated in light intensity and reflected by a bit formed on the tracking guide.

The diverging laser beam reflected from the recording film of the optical disk 11 is converted into a parallel beam by the objective lens 18 when it is focused, passes through the quarter-wave plate 17 again, and is returned to the polarizing beam splitter 16. By reciprocating through the 1/4 wavelength plate 17, this laser beam beam has a polarization plane of 90° compared to when it is reflected by the polarizing beam splitter 16.
Since the light is rotated by a degree, the light passes through the polarizing beam splitter 16 without being reflected by the polarizing beam splitter 16.

The laser beam passing through the polarizing beam splitter 16 is
The light is irradiated onto the photodetector 20 through the condensing lens 19.

This photodetector 20 includes photodetection cells 2Qa and 20b that convert the light imaged by the condenser lens 19 into electrical signals.
It is made up of.

The output of the optical head 13, that is, the photodetection cells 20a, 2
The outputs of 0b are supplied to amplifiers 30 and 31, respectively.

The outputs of the amplifiers 30, 31 are fed to an adder 32. This adder 32 compares the increasing #video signal* with the reference voltage signal supplied from the reference voltage signal switching circuit 35, detects whether the video signal has reached the reference voltage signal, and if it has reached the reference voltage signal, , a detection signal with information, and a reference voltage signal of two types of levels are output. for example,
Normally, the reference voltage signal Va is output, and the recording light amount setting section 3
In response to a switching signal supplied from 8 (during recording), a reference voltage signal vb (Va>Vb) is output. The signals output from the comparator 34, that is, the information presence/absence signal and the double writing detection signal are supplied to the CPU 37. This CPLJ 37 controls the whole, and outputs a control signal to the recording light amount setting section 38 and the reproduction light amount setting section 39 in accordance with the recording signal or reproduction signal supplied from the external device (not shown). It is. The reproduction light amount setting section 39 outputs a drive signal to the base of the NPN transistor 40 in response to a control signal supplied from the CPU 37 during reproduction. The collector of this transistor 40 is grounded via a resistor 41. The transistor 40 performs current amplification in response to a drive signal supplied from the reproduction light amount setting section 39. As a result, a current flows through the semiconductor laser oscillator 14 due to the current amplification of the transistor 40, and the reproduction beam light from the semiconductor laser oscillator 14 is irradiated onto the optical disc 11.

The recording light amount setting section 38 also controls the CPLI during recording.
In response to a control signal supplied from 37, a control signal is outputted to the gate of an FET (field effect transistor) 42 to turn it on and off in response to a modulation signal corresponding to recording data. The sources of these FETs 42 are grounded. The drain of this FET 42 and the transistor 40
The collector is commonly connected to the power supply (Vcc) through a resistor 44, the semiconductor laser oscillator 14, and a resistor 45 in this order. The FET 42 is turned on in response to a control signal supplied from the recording light amount setting section 3, and a predetermined current is supplied to the semiconductor laser oscillator 14.

Next, the operation in such a configuration will be explained.

First, recording of information will be explained. For example, right now, CP
U37 first outputs a control signal to the reproduction light amount setting section 39. Then, the reproduction light amount setting unit 39 outputs a drive signal to the base of the transistor 40 in accordance with the supplied control signal. Thereby, the transistor 40 performs current amplification according to the drive signal. As a result, a (continuous) low-intensity laser beam is generated from the semiconductor laser oscillator 14.

Further, the CPU 37 sends a modulated signal corresponding to recording data supplied from an external device (not shown) to the recording light amount setting section 3.
Output to 8. Then, the recording light amount setting section 38 outputs a control signal corresponding to the modulation signal to the FET 42, and outputs a switching signal to the reference voltage signal switching circuit 35. As a result, the FET 42 is intermittently turned on and off according to the supplied control signal. Therefore, a high current flows intermittently to the semiconductor laser oscillator 14, and the semiconductor laser oscillator 1
4, an intermittent laser beam of high intensity is generated. As a result, the semiconductor laser oscillator 14 emits a laser beam of high intensity (recording beam) and a laser beam of low intensity (reproduction beam). This laser beam is transmitted through collimator lens 1
5 into a parallel light beam, and a polarizing beam splitter 16
guided by. The light beam guided to the polarizing beam splitter 16 is reflected, passes through the λ/4 plate 1 and enters the objective lens 18, and is focused onto the optical disk 11 by the objective lens 18. As a result, when recording information, bits are formed on the tracks of the recording film on the optical disk 11 by irradiation with a laser beam (recording beam) of high intensity.

Furthermore, as described above, a low current is supplied to the semiconductor laser oscillator 14 except during the recording operation. As a result,
When the recording beam is not being generated, the semiconductor laser oscillator 14 emits a weak laser beam (reproduction beam). This laser beam is irradiated onto the optical disk 11 in the same way as the recording beam. The reflected light from the optical disk 11 with respect to this reproduction beam light is reflected by the objective lens 1
8, the light is converted into a parallel light beam, passed through a λ/4 plate 1 and guided to a polarizing beam splitter 16.

At this time, the laser beam guided to the polarizing beam splitter 16 returns to the λ/4 plate 1 sheet metal 7, and the plane of polarization is rotated by 90 degrees compared to when it is reflected by the polarizing beam splitter 16. Thereby, the laser beam passes through the polarizing beam splitter 16 without being reflected. The laser beam that has passed through the polarizing beam splitter 16 is passed through the condensing lens 2.
0 to the photodetector 20. Therefore, signals corresponding to the irradiated light are outputted from the photodetection cells 20a and 20b as reproduction signals, and these signals are transmitted to the amplifier 3, respectively.
0.31.

As a result, the signals from the amplifiers 30 and 31 are added by the adder 32, and the result of this addition is supplied to the comparator 34.

Signal vb is output to comparator 34. As a result, the comparator 34 compares the supplied binary signal with the reference voltage signal (Va or vb>) supplied from the reference voltage switching circuit 35, and if the binary signal is larger than the reference voltage signal,
A double write detection signal is output to CPIJ37. Thereby, the CPU 37 reliably detects double writing in the information recorded area during information recording using the detection signal.

Furthermore, force steering, tracking, etc. are performed using the outputs of the amplifiers 30 and 31.

Next, information reproduction will be explained. That is, the CPU
37 outputs a control signal to the reproduction light amount setting section 39.

Then, a continuous laser beam of low luminous intensity is generated from the semiconductor laser oscillator 14. As a result, the operation is the same as when the reproduction beam light is emitted during recording, and the outputs of the photodetection cells 20a and 20b are supplied to amplifiers 30 and 31, respectively.

As a result, the comparator 34 doubles the supplied m signal and the reference voltage supplied from the reference voltage switching circuit 35. Thereby, the CPU 37 detects the information recorded area and the unrecorded area according to the detection signal.

Additionally, forcing, tracking, etc. are performed using the outputs of the amplifiers 30 and 31, and data reading (reproduction) is performed using the output of the binarization circuit 33.

As mentioned above, when recording information, a low-level reference voltage signal is output in correspondence with the recording beam light, a high-level reference voltage signal is output in correspondence with the reproduction beam light, and these reference voltage signals and By comparing the signal (video signal) corresponding to the reflected light, accurate double writing detection can be performed. Furthermore, during reproduction, by comparing a high-level reference voltage signal corresponding to the reproduction beam light with a signal corresponding to the reflected light, it is possible to accurately detect whether information has been recorded or not. Furthermore, the double writing detection and the recorded/unrecorded information detection can be performed using the same circuit.

[Effects of the Invention] As explained above, according to the present invention, it is possible to detect whether information has been recorded or not when reproducing information, and
It is possible to provide a disk device that can reliably detect double writing to an area where information has been recorded during information recording and can prevent double writing.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a diagram schematically showing the overall configuration, and FIG.・・・
- Optical disk (disc), 14... Semiconductor laser oscillator, 20... Photodetector, 20a, 20b... Photodetection cell, 30.31... Amplifier, 32... Adder,
33... Binarization circuit, 34... Comparator, 35...
Reference voltage switching circuit, 37... CPU, 38... Recording light intensity setting section, 39... Reproduction light intensity setting section, 40...
・Transistor, 42...FET.

Claims (1)

[Claims] A disk device that records or reproduces information on a disk using focused light, includes a light source, a focusing means for focusing the light emitted from the light source onto the disk, and reflection from the disk by the focusing means. a conversion means for converting light into an electrical signal; a reference voltage output means for outputting a reference voltage signal that is different when light corresponding to recorded information is emitted from the light source and at other times; and conversion by the conversion means. and a detection means for detecting double writing of information according to the comparison result by the comparison means. disk device.