JPH03122821A - Optical disk restoring device - Google Patents

Abstract

PURPOSE:To reproduce an optical disk with a various reflection factor by switching the power of a reproducing laser beam corresponding to the reflection factor of each disk. CONSTITUTION:Means 9 and 11 are provided to detect the reflection factor of the disk, and a means 8 is provided to change the power of the projecting laser beam for reproduction according to the detected reflection factor. According to the reflection factor, the power of the reproducing laser beam so that a signal level in a detector 5 of an optical head 6 can be maintained at a prescribed value. Thus, by simply changing an optical disk device exclusive for reproducing, a DRAW type or reloadable optical disk can be reproduced and accordingly, the use of the optical disk can be enlarged.

Description

Detailed Description of the Invention [Field of Application in the Poultry Industry] The present invention relates to an optical disc device for recording and reproducing information on a write-once optical disc or a rewritable optical disc, and particularly relates to a CD (compact disc). ), CD-
The present invention relates to an optical disc device for reproducing read-only optical discs such as ROM, CD-I, LM (laser disc), and the above-mentioned write-once and *replaceable optical discs.

[Conventional technology]

Conventionally, write-once optical discs include those in which information bits are formed by melting the recording layer by laser beam irradiation, and those in which information bits are formed by changing the phase of the recording layer from an amorphous phase to a crystalline phase, and these disks are rewritable. Examples of optical discs include those that utilize magneto-optical recording and those that utilize phase change between a crystalline phase and an amorphous phase.

Also, as a read-only optical disc, there is a CD (compact disc) with uneven bits formed on the substrate.

LV (laser disc) and the like are widely known.

As a technique for reproducing these optical discs with one device, as described in Japanese Patent Application Laid-Open No. 1-128234, the reflectance of a write-once or refill-type optical disc is increased, and a conventional playback-only optical disc device is used. There are discs that can be played back in the same way as playback-only optical discs. Also, Unexamined Patent Publication No. 1-12
As described in ad in Publication No. 5727, by recording information regarding reflectance on the optical disk in advance and selecting and controlling the reproduction system based on this information, it is possible to use the same magneto-optical disk and read-only optical disk. Some devices allow playback.

[Problem to be solved by the invention]

The conventional technology described above requires the same level of reflectance as a read-only optical disk, so there are strict limitations on the disk reflectance, or the playback system circuit selects and controls the playback system according to the disk reflectance. No consideration was given to the increase in scale, and there was a problem in easily reproducing disks with different reflectances.

An object of the present invention is to provide read-only discs such as CDs and write-once optical discs by easily changing circuits.

An object of the present invention is to provide a device capable of reproducing optical discs having different reflectances such as removable optical discs.

[Means to solve the problem]

The above object is achieved by switching the power of the reproducing laser beam in the original disc reproducing device ζζ according to the reflectance of each disc.

[Effect]

In order to reproduce discs with different reflectances, it is necessary to supply a signal at a predetermined level to the focus and tracking servo circuit and the data signal processing circuit. Conventionally, a gain is added to the front stage of the circuit according to the reflectance level. Although a compensation circuit was provided, the present invention is characterized in that the signal level at the detector of the optical head is maintained at a predetermined value by switching the power of the reproduction laser beam according to the reflectance. Since the signal level can be adjusted by adjusting the power of the laser beam that is the source, there is almost no need to adjust the reproduction system, and the reproduction system can be significantly simplified. In addition, the output of the detector is fed back to the laser drive circuit, even for disks with different reflectances.
It becomes possible to freely obtain a desired level of detector output within the allowable range of laser output.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, l indicates an optical disk having a CD signal as information, 6 indicates an optical head, an objective lens 2, a half mirror 3, and a semiconductor laser (wavelength 780 nm)4. It consists of 5 detectors. The focus and tracking servo circuit 10 and the data signal processing circuit 11 have constant values set to match a CD (compact disc) having a reflectance of 70 inches or more. 9 is a circuit for detecting the reflectance of the optical disc 1; 8 is a circuit for switching the laser power according to the output signal of 9; and 7 is a circuit for driving the laser with the power set in 8.

For example, when a CD (reflectance of 70 S or more) is set as an optical disc in the apparatus of this embodiment, the focus pull-in circuit (not shown) is activated, and the objective lens 2 moves toward the optical disc, and the optical disc 1 is moved away from the optical disc 1. A detector 5 detects the reflected light, and a data signal processing circuit 11 and a reflectance detection circuit 9 detect the reflectance of the disk. The initial value of the laser power is 3 mW (Q,
5 mw) and adjust it for CD use. therefore,
In this case, the reflectance detection circuit 9 detects that the optical disc is a CD, and without switching the laser power, focusing and tracking are performed as is, and a CD signal is output. On the other hand, if the optical disc l is a write-once optical disc with a rumored reflectance of 35, the reflectance detection circuit 9 detects that it is a write-once optical disc in the same manner as the above process, and the laser power switching circuit wI8 detects that it is a write-once optical disc.
The laser power was 6 mW (x mw on the optical disc surface) and 2
By setting the value twice and effectively obtaining a signal level equivalent to 70% reflectance on the detector 5, focusing and tracking can be performed and a CD signal can be output. Book 9
1. On the male side, since a laser with a rating of 17mW was used as the semiconductor laser 4, the laser power switching circuit 8 was set to two levels of 3mW e 6mW, and a playable optical disc with a high reflectance (701 or higher) was used. ) and low reflectance (35ts to 50%).

It goes without saying that if the rated output of the semiconductor laser is increased, it will be possible to handle disks with even lower reflectance. Further, in this embodiment, the laser switching is performed in two stages, but it is also possible to increase the separation performance of the reflectance detection circuit 9 to have more stages.

Note that a 3-beam method was used as the tracking method in this embodiment. Next, another embodiment according to the present invention is shown in FIG.

As shown in the embodiment, the data signal processing circuit 11 has a constant set to match the CD, so the data signal amplitude is in accordance with the CD standard In/It, as shown in FIG. , =0.3 to 0.7 In/Irop≧0.6. Here, hOP is the reflectance of the mirror section, 1. is the signal amplitude of high frequency, is the low frequency signal amplitude. On the other hand, in write-once optical discs or reswap-type optical discs, Is /Irop*Lt /I 16p may be smaller than that of the CD standard. At this time, as shown in FIG. 2, a reflectance offset circuit is provided between the detector 5 and the data signal processing circuit 11 to effectively reduce the hOP signal. This is to ensure that the standards are met. In this embodiment, the offset circuit is controlled by the reflectance detection circuit 21.
This is done at the same time as the laser power switching command, but
It is not limited to this.

FIGS. 4 and 5 show an example of the optical disc used on the Meio side.

In FIG. 4, 31 is a polycarbonate resin substrate;
2 is a phase change recording film made of a 5b-8e-Bl film, O is an interference film made of SiN, U is a reflective film made of Au, and A is an organic protective film made of an ultraviolet curing resin.

When the phase change recording film changes from amorphous to crystalline, the refractive index changes from 4.0-i0.5 to 5.0-12.0.

Therefore, by using the above three-layer structure of substrate/phase change recording M/interference film/reflection film, the reflectance is high when the phase change recording film is amorphous, and low when it is crystalline. . From this, by selecting the amorphous state as the unrecorded state and the crystalline state as the recorded state, it is possible to change the reflectance from a high level to a low level before and after recording, and make it the same polarity as a read-only optical disc. can.

In the optical disc of this example, the reflectance of the recording film is 40.
Group 3 for tracking when recording information
6 (group width 0.7μ steel, depth 3Qnm, pitch 1.
5 μm), the actual reflectance (reflectance entering the detector ζ) is 35 due to the effect of group diffraction.
%. The disc is a write-once optical disc,
It can be written only once.

On the other hand, the optical disc shown in FIG. 5 is a rewritable original disc, and the first interference film 42 made of 41 SiN
8b-'l'a Phase change recording film consisting of SiN
The second interference film is made of A11, and the reflective film is made of A11. In this disc, in order to reduce damage caused by rewriting, the recording film 42 is replaced with an inorganic interference film 41.
Sandwiched with 0. The thickness of each layer is
A first interference film of 7 Q nm, a phase change recording film of 30 nm, a second interference film of 7 Q nm, and a reflective film of 1100 nm were used to obtain a reflectance of 40% after group diffraction.

In the above disc, straight groups were used, but a wobbling group 62 wobbled with respect to the track center 61 as shown in FIG. You can also get

FIG. 7 shows a specific example of an apparatus for recording information on a write once optical disc or a rewritable optical disc.

In FIG. 7, the recording device inputs data to a signal processing circuit 72 through an EFM modulation circuit 71 in the case of analog input distribution, and as it is in the case of CD data input 91. Based on the data, the laser drive circuit 76 controls the laser output, and the optical head 77 writes information onto the optical disk 1 while applying focus and tracking servo.

At this time, the motor servo circuit 73 simultaneously rotates the disk at a constant speed. For constant speed rotation, a self-clock in the signal processing circuit or a signal from the wobbling group shown in FIG. 6 can be used. The tracking method is a push-pull method using diffracted light from the group.

Since this device is an upper compatible device of a CD player, it is equipped with an automatic judgment circuit for optical disk reflectance, a CD playback system, etc. (not shown).

In the above-mentioned embodiment, the method of determining the reflectance of an optical disc is based on the signal strength of the optical head detector, but the method is not limited to this, and the method of writing reflectance information on the optical disc, the sensor hole of the disc cartridge, etc. Other methods of detection may also be considered.

In addition, in the implementation described above, a phase change recording film was used as a write-once optical disc or a rewritable optical disc, but it can also be applied to other optical recording films, organic recording films, MD recording films that utilize deformation, etc. Needless to say.

Furthermore, although the above-mentioned embodiments were intended for CD players, LV (laser disc), CD-ROM, CD
Even when applied to players such as DI and CDV, the effects of the present invention will not be impaired.

[Effects of the Invention] According to the present invention, it is possible to reproduce write-once or rewritable optical discs by simply using a read-only optical disc device, so that the uses of optical discs can be expanded.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an optical disc device as an embodiment of the present invention, FIG. 2 is a block diagram of an optical disc device as another embodiment of the invention, FIG. 3 is a characteristic diagram of an optical disc playback signal, and FIG. 5 and 5 are partial cross-sectional views of the optical disk used in the embodiments of the present invention, and FIG. 6 is a partial enlarged view of the optical disk for explaining the wobbling group.
FIG. 7 is a block diagram of an optical disc device as a device for recording information on a write once optical disc or a rewritable optical disc. l...Optical disk 6...Optical head 7...
Laser drive circuit 8... Laser power switching circuit 9... Reflectance detection circuit closed 1 Figure 2 Figure f'5 CD control Ij/IroP = 0.5~(7,7 In/1roF≧06 Steel 6 Figure 1 1 Tofu 7 Naka 1 Shiriki 4 Figure Kabuto 5 Kabuto 1 Figure

Claims (1)

[Claims] 1. In an optical disc reproducing apparatus that projects a laser beam onto an optical disc and reproduces information recorded thereon, the apparatus comprises means for detecting reflectance of the optical disc, and a means for reproducing information according to the detected reflectance. 1. An optical disc reproducing apparatus, comprising: means for changing the power of a projected laser beam.