JPH08221890A - Optical reproducing device - Google Patents

Abstract

PURPOSE: To prevent a recording film from being destroyed by discriminating the kind of an optical disk by reproducing the optical disk with a semiconductor laser for a CD at first. CONSTITUTION: When an optical disk 1 is loaded in an optical reproducing device, a disk motor 2 is rotated to turn on the semiconductor laser for the CD. Next, a data signal 111 is outputted from a demodulation circuit 9. At this time, in the case the optical disk 1 is the CD, a system controller 11 discriminates that the optical disk 1 being reproduced in the CD from a data signal and continues the reproducing. However, in the case the optical disk 1 is a high density optical disk, the possibility that servo control, especially a tracking control becomes impossible is high. The reason is that the track pitch of the high density optical disk is almost the half of the pitch of the CD. Consequently, the system controller 11 discriminates that the optical disk being reproduced is not the CD but is the high density optical disk. As a result, the controller 11 turns on the semiconductor laser for the high density optical disk.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical reproducing apparatus for reproducing optical disks having different recording densities.

[0002]

2. Description of the Related Art At present, compact discs (hereinafter abbreviated as CD) are widely used for music or computer data. This CD has a diameter of 120 mm, a track pitch of about 1.6 μm, and a minimum pit length of about 0.9 μm. Since the CD is an optical disk for reproduction only, aluminum is used as the reflective film and the reflectance is 70 to 80%. The optical reproducing device for reproducing this CD uses a semiconductor laser of 770 to 800 nm as a light source, and the numerical aperture (NA) of the objective lens for condensing the laser light on the optical disk is generally about 0.45. .

Optics Vol. 18, No. 11 (1989)
(November, 2013) As described in pp. 612 to 613 “Application of high reflectance write-once type optical disc to recording / reproducing CD”, a write-once type optical disc capable of recording a signal only once has been put into practical use. This write-once optical disc uses an organic dye as a signal recording film, and the optical disc after signal recording has a reflectance of 70 at a wavelength of 770 to 800 nm so that the optical disc can be reproduced by an optical reproducing device for CD reproduction.
% Or more.

On the other hand, in recent years, semiconductor lasers have made remarkable progress, and a semiconductor laser for red light having a wavelength of 690 to 630 nm has been put into practical use, and in combination with an objective lens having a numerical aperture of 0.55 to 0.6, A high-density optical disc having a recording density 3 to 4 times that of the current CD has been proposed. (For example, the 1993 Autumn Meeting of the Institute of Electronics, Information and Communication Engineers, Lecture No. C-364 "High Density C Using Red Laser Pickup"
If the above-mentioned high-density optical disk is put to practical use in the future, it is naturally desirable that the optical reproducing apparatus can also reproduce the conventional CD and the write-once optical disk compatible with the reproduction of the CD. . In response to this demand, an optical reproducing apparatus as disclosed in Japanese Patent Laid-Open No. 6-259804 has been proposed. This is equipped with a conventional semiconductor laser for reproducing CDs and a semiconductor laser for reproducing high-density optical discs having a shorter wavelength. Depending on the type of optical disc to be reproduced, either semiconductor laser is used. The signal is reproduced by the laser light emitted by.

[0005]

An optical reproducing apparatus for reproducing a high density optical disc discriminates between a conventional CD and a high density optical disc, and a semiconductor laser corresponding to the optical disc to be reproduced.
It is necessary to selectively turn on the light and reproduce the signal from the reflected light. Further, for a write-once type optical disc that is compatible with reproduction of a CD, it is necessary to take sufficient destruction prevention measures as described below.

FIG. 4 shows an example of spectral characteristics of reflectance and absorptance of an optical disk using an organic dye as a recording film, like the write-once optical disk described above. Wavelength 770
70% or more of the reflectance at 800 nm is obtained, but the wavelength for reproducing high density optical disks is 630 to 69.
The reflectance at 0 nm is reduced to about 20%.
On the other hand, the absorptance is about 20% at 770 to 800 nm, but is a little over 70% at 630 to 690 nm, which is about 3 to 4%.
Double. This write-once type optical disc 770-8
The upper limit of the reproduction laser power at 00 nm is about 0.8.
mW. If the laser power is made larger than this, there is a possibility that the recording film may be destroyed due to a local temperature rise in the portion where the reproducing light spot is hit. But 630
At 690 nm, the absorption factor is 3 to 4 times, and the area of the reproduction light spot is about 1 / 2.5, so the upper limit of the reproduction laser power is about 0.1 mW or less. On the other hand, as a matter of course, the larger the reproduction laser power is, the more preferable it is to obtain a reproduction signal having a large SN ratio, and it is generally 0.1 to 0.5 mW. As a result, when reproducing a write-once type optical disc which is compatible with reproduction by a CD with a player for reproducing a high density optical disc, 630
There is a possibility that the recording film may be destroyed when reproducing with a light source of ˜690 nm.

Therefore, in the optical reproducing apparatus for reproducing the high density optical disc, the conventional CD and the write-once type optical disc are distinguished from the high density optical disc, and the CD and the write-once type optical disc are reproduced by the light source of 770 to 800 nm. It is desirable to prevent the write-once optical disc from being destroyed.

However, in the above-mentioned conventional optical reproducing apparatus, no consideration has been given to identifying the type of the optical disc and protecting the write-once type optical disc.

[0009]

As disclosed in the above-mentioned document, the high-density optical disc has a track pitch and a minimum pit length which are about ½ of those of a conventional CD.
With a light source of 770 to 800 nm for reproducing a CD, the light spot for reproducing is too large for a high density optical disc and reproduction is impossible. The present invention was made paying attention to this, and when reproducing an optical disk, first,
Attempt to reproduce with a CD reproduction light source of nm. If reproducible, the disc is discriminated as a conventional CD or a write-once type optical disc that is reproducible with the CD, and the replay is continued. On the other hand, if it cannot be reproduced, it is identified as a high-density optical disc and 630-690
Reproduction is performed with a light source for reproducing a high-density optical disc of nm.

[0010]

In the optical reproducing apparatus of the present invention, first, 770-80
In order to discriminate the type of the optical disc by attempting reproduction with a 0 nm light source, a write-once type optical disc that is compatible with CD reproduction is always reproduced with a 770-800 nm light source, so the recording film is not destroyed. .

[0011]

【Example】

(First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit block diagram of an optical reproducing apparatus of the present invention. The optical disc 1 is mounted on the disc motor 2. Here, the optical disc 1 is a conventional C
The case of a write-once type optical disc that is reproduction compatible with D or CD will be described. System controller 1
The motor drive circuit 12 outputs the motor drive signal 118 in response to the control signal 115 of 1, and the disc motor 2 rotates. Next, the laser drive circuit 13 outputs the laser drive signal 109 in response to the control signal 113 of the system controller 11 to turn on the semiconductor laser (not shown) of the CD optical pickup 3. A detection signal 101 from a photodetector (not shown) of the CD optical pickup 3 is input to the preamplifier 5 and a servo signal 103 and an RF signal 105 are output. The servo circuit 7 is actuated based on the control signal 116 of the system controller 11 and the servo signal 103.
A lens drive signal 107 is output to drive a lens actuator (not shown) of the CD optical pickup 3 to perform focus and tracking control. The demodulation circuit 9 demodulates the RE signal 105 into the data signal 111, and the data signal 11
1 is input to the system controller 11 and controls the motor drive circuit 12 based on the clock signal in the data signal 111 so that the optical disk 1 rotates at a prescribed speed. On the other hand, the data signal 111 is converted into an audio signal, a video signal or the like. Next, a case where the optical disc 1 is a high density optical disc will be described. Optical disc 1 is disc motor 2
Be attached to. Control signal 1 of system controller 11
The motor drive circuit 12 outputs the motor drive signal 118 according to 15.
Is output and the disk motor 2 rotates. Next, the laser drive circuit 14 outputs the laser drive signal 110 in response to the control signal 114 of the system controller 11 to turn on the semiconductor laser (not shown) of the optical pickup 4 for the high density optical disk. The detection signal 102 from the photodetector (not shown) of the optical pickup 4 for the high density optical disc is the preamplifier 6
And the servo signal 104 and the RF signal 106 are output. The servo circuit 8 outputs the actuator drive signal 108 based on the control signal 117 and the servo signal 104 of the system controller 11 to output the lens actuator of the optical pickup 4 for the high density optical disc (see FIG. (Not shown) is driven to perform focus and tracking control. The demodulation circuit 10 demodulates the RE signal 106 into a data signal 112, and the data signal 112 is input to the system controller 11 and the optical disk 1 is rotated at a prescribed speed from the clock signal in the data signal 112. Motor drive circuit 1
Control 2 On the other hand, the data signal 112 is converted into an audio signal, a video signal or the like.

FIG. 2 is a flow chart for explaining a series of operations of the optical reproducing apparatus of FIG. When the optical disk 1 is mounted on the optical playback device, the disk motor 2 rotates and C
The semiconductor laser for D lights up. Next, the focus, tracking control, and rotation speed control of the disk motor 2 are performed, and the demodulation circuit 9 outputs a data signal 111. Here, if the optical disc is a CD, the system controller 11
Discriminates from the data signal that the optical disc being reproduced is a CD and continues reproduction. However, if the optical disc is a high-density optical disc, servo control, particularly tracking control, is likely to be impossible. This is because the track pitch of a high density optical disc is about 1/2 of that of a CD. Even if tracking control is possible, a correct data signal cannot be obtained because the minimum pit length of a high density optical disc is about half that of a CD. In either case, since the correct data signal cannot be obtained, the system controller 11 determines that the optical disk being reproduced is not the CD but the high density optical disk. As a result, the system controller 11 stops the focus and tracking control, turns off the semiconductor laser for CD, and turns on the semiconductor laser for high density optical disk. Then, as in the case of the above-mentioned CD, focus, tracking control and rotation speed control are performed to reproduce the high density optical disc.

The specific structure of the optical pickup is not described because it has nothing to do with the essence of the present invention, but the structure disclosed in, for example, Japanese Patent Laid-Open No. 61-61240 may be used.

(Second Embodiment) Next, a second embodiment of the present invention will be described. FIG. 3 is a circuit block diagram of the optical reproducing apparatus of the present invention. The same parts, circuits, and signals as those in FIG. 1 are denoted by the same reference numerals, and the configuration of the optical pickup is different from that in FIG. The optical pickup 17 includes two semiconductor lasers and two semiconductor lasers.
It is provided with a single photodetector and an objective lens, and may have the configuration disclosed in, for example, Japanese Patent Laid-Open No. 6-259804 which is the conventional example described above. When the optical disk 1 is mounted on the disk motor 2, the motor drive circuit 12 is driven by the motor drive signal 1 by the control signal 115 of the system controller 11.
18 is output, and the disc motor 2 rotates. Next, the laser drive circuit 13 outputs the laser drive signal 109 in response to the control signal 113 of the system controller 11 to turn on the CD semiconductor laser 18 of the optical pickup 17. Detection signal 1 from the CD photodetector 20 of the optical pickup 17
01 is input to the preamplifier 5 and the servo signal 103 and R
The F signal 105 is output. The servo circuit 15 includes a control signal 119 for the system controller 11 and a servo signal 103.
On the other hand, the actuator drive signal 120 is output to drive the lens actuator (not shown) of the optical pickup 17 to perform focus and tracking control. The demodulation circuit 16 common to CDs and high-density optical disks is R
The E signal 105 is demodulated into a data signal 111, and the data signal 111 is input to the system controller 11 so that the optical disc 1 can be rotated at a prescribed speed from the clock signal in the data signal 111. Control the drive circuit 12.
On the other hand, the data signal 111 is converted into an audio signal, a video signal or the like. Next, a case where the optical disc 1 is a high density optical disc will be described. The motor drive circuit 12 outputs a motor drive signal 118 in response to the control signal 115 of the system controller 11 to rotate the disk motor 2. Next, the laser drive circuit 14 outputs the laser drive signal 110 in response to the control signal 114 of the system controller 11 to turn on the semiconductor laser 19 for high density optical disk. The detection signal 102 from the photodetector 21 for the high density optical disk is input to the preamplifier 6 and the servo signal 104 and the RF signal 10 are input.
6 is output. The servo circuit 15 is a system controller.
Based on the control signal 119 of the laser 11 and the servo signal 104, an actuator drive signal 120 is output to drive a lens actuator (not shown) of the optical pickup 17 to control focus and tracking. Is done. The common demodulation circuit 16 demodulates the RE signal 106 into a data signal 112, and the data signal 112 is input to the system controller 11 so that the optical disc 1 can operate at a prescribed speed from the clock signal in the data signal 112. Motor drive circuit 1 to rotate at
Control 2 On the other hand, the data signal 112 is converted into an audio signal, a video signal or the like. Although the common demodulation circuit is used in the embodiment shown in FIG. 3, separate demodulation circuits may be used as shown in FIG. A series of operations of the optical disk device shown in FIG. 3 may be performed in the same manner as the flow chart shown in FIG.

[0015]

According to the present invention, in an optical reproducing apparatus equipped with a semiconductor laser for CD and a semiconductor laser for high density optical disk, reproduction is first performed by a semiconductor laser for CD of 770 to 800 nm. In order to discriminate the type of the optical disc, the write-once type optical disc compatible with the CD is always reproduced by the semiconductor laser for CD of 770 to 800 nm, and the recording film is not destroyed.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of a first embodiment of an optical reproducing apparatus of the present invention.

FIG. 2 is a flowchart showing a series of operations of the optical reproducing apparatus of the present invention.

FIG. 3 is a circuit block diagram of a second embodiment of the optical reproducing apparatus of the present invention.

FIG. 4 Spectral characteristics of reflectance and absorptance of a write-once optical disc that is compatible with CD playback

[Explanation of symbols]

 1 Optical Disk 2 Disk Motor 3 Optical Pickup for CD 4 Optical Pickup for High Density Optical Disk 5, 6 Preamplifier 7, 8, 15 Servo Circuit 9, 10, 16 Demodulation Circuit 11 System Controller 12 Motor Drive Circuit 13 , 14 laser drive circuit 17 optical pickup 18 semiconductor laser for CD 19 semiconductor laser for high density optical disc 20 photodetector for CD 21 photodetector for high density optical disc

Claims (3)

[Claims] 1. A first light source for emitting a light beam of a first wavelength for reproducing a first optical disk, and a first optical disk for reproducing a second optical disk having a recording density higher than that of the first optical disk. Second light source that emits a light flux having a second wavelength shorter than the wavelength, a lens means that collects the light flux having the first wavelength and the light flux having the second wavelength on the optical disc, and the first and second optical discs. An optical reproducing device comprising a photodetector for receiving reflected light from the optical reproducing device, characterized in that means for discriminating between the first optical disk and the second optical disk is provided. 2. If the signal can be reproduced by the first light source, it is identified as the first optical disk, and if the signal cannot be reproduced by the first light source, it is identified as the second optical disk and the signal is reproduced by the second light source. The optical reproducing apparatus according to claim 1, wherein: 3. When starting reproduction of an optical disk, first try reproduction by a first light source, if reproduction is possible, identify the first optical disk and continue reproduction, and if reproduction is impossible, identify it as a second optical disk. The optical reproducing apparatus according to claim 2, wherein reproduction is performed by the second light source.