JPS61180935A - Optical signal recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain the reproduction of two types of disks by discriminating these two disks by a disk discriminator and using this discrimination signal to switch the gains so as to obtain an equal amplitude level for reproduced output signals. CONSTITUTION:A disk discriminator 31 uses a reflective detector to discriminate the 1st disk which is recorded in variable density with the thermal change from the 2nd disk which is recorded totally in a recess/projection structure. The output signal of a head amplifier 15 is switched by the discrimination control output signal of a disk discriminating signal processing circuit 32 via a gain switching circuit 33. Thus the amplitude gain of the reproduced output signal is switched. The amplitude (a) of the address signal section is smaller than the amplitude (b) of the information signal section in the case of the 1st disk. While the output signal amplitude (c) of the 2nd disk is the largest. The reproduced output signal of the information signal section is controlled by a gain switching circuit 40 so that the amplitude is set at the a/b-fold value with the 1st disk and that the gain has no change with the 2nd disk.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a method for recording information signals such as video signals and digital signals by irradiating a photosensitive disk-shaped recording medium with a light beam such as a semiconductor laser focused to a minute beam of about 1 μm. The present invention relates to an optical information recording/reproducing device that records or reproduces data with high density as changes in unevenness or shading, and particularly relates to signal reproduction.

2. Description of the Related Art An example of a conventional optical recording/reproducing device will be described below with reference to the drawings.

FIG. 6 shows the configuration of a conventional optical recording/reproducing device. Recording signals such as video signals and digital signals applied from the signal input terminal 1 are subjected to processing such as modulation in the signal processing circuit 2, and are sent to the semiconductor laser 4, which is a light source that generates a light beam to be recorded on the disc 1°. It is guided to a semiconductor laser drive circuit 3 to drive it. The light beam emitted from the semiconductor laser 4 passes through the lens 5 and enters the polarizing beam splitter.
6, passes through a λ/4 plate 7, is narrowed down to a minute beam of about 1 μm through an aperture lens 8, and is irradiated onto a disk 1°. Further, the focus element 9 causes the aperture lens 8 to move to follow the surface wobbling of the disk 10, so that the light beam is always focused on the disk 1o.

Concentric or spiral guide tracks are formed on the disk 10, and each guide track is pre-formed with a unique address signal and a signal indicating the rotation start position.

A signal indicating this rotation start position is detected by a rotation detector 12, and the disk 1o is rotated at a constant speed (for example, 1800 rpm) by a motor 11 and a motor control circuit 13. In addition, when reproducing a signal, a light beam weaker than that during recording is emitted from the optical guide laser 4, and the light beam is transmitted through the lens 5, the polarizing beam splitter 6, the λ/4 plate 7, and the aperture lens 8. The same control as above is performed to irradiate the disk 1o, and the reflected light is split by the polarizing beam splitter 6 through the aperture lens 8λ/4 plate 7, and is converted into an electrical signal by receiving the light with the photoelectric converter 14. . Photoelectric converter 14
The output electrical signal is amplified by the head amplifier 16, and signal processing including demodulation is performed by the signal processing circuit 16, and a reproduced signal is obtained from the signal output terminal 17.

Also, the part indicated by dotted line A is the semiconductor laser 4 and the lens 6.
, polarizing beam splitter 6, λ/4 plate 7, aperture lens 8
, an optical system consisting of a focusing element 9, etc., and a transport system 18 consisting of a linear motor, a step motor, etc.
and the disc 10 to be recorded or reproduced by the drive circuit 19.
the disc 10 so that the light beam irradiates the track of
The optical system A is moved in the radial direction.

FIG. 6(1) is an example of an optical disc provided with concentric guide tracks.

The guide track 2o is formed in advance in a phased structure and has a groove shape. Further, the guide track 2o has an address signal section 22 in which each unique address signal is formed in advance in a phase structure in a discrete uneven shape, and an information recording section 21 for recording an information signal, which are structured in the form of a sector. . Recording is performed along the guide track 2o, and the address signal is read and recorded in the corresponding information recording section. FIG. 6(n) shows an enlarged plan view of the guide track 2.0.

22 is the address signal section in which the address signal is recorded in a discrete, uneven phase structure. When 21 is irradiated with a minute spot light in the information signal recording section, a thermal change occurs and the recording becomes black, forming a recording focus as shown in FIG. 6A. The recorded pit portion has a higher density and higher reflectance than the unrecorded portion.

Therefore, the information signal is reproduced by changes in reflectance. FIG. 6(1)(b) shows the output waveform of the reproduced signal in the information recording signal section 21, and the recording bit portion has a high reflectance. Further, (A) shows the output waveform of the reproduced signal in the address signal section 22, and the reflectance changes depending on the unevenness of the groove.

Further, the amplitude a of the address part is smaller than the amplitude a of the information signal part. The above write-once type disc uses an acrylic substrate or the like, and the reflectance is about 20% in the unrecorded area and in the 10-inch recorded area. On the other hand, in a read-only optical disc on which information is recorded in advance, such as a general optical video disc, both the address signal section and the information signal section are formed with a convex-concave phase structure. This method is used because it stamps disks in large quantities at high speed and at low cost. Such a read-only disk is made of an aluminum base material and has a reflectance of about 40%.

Figure 7 shows the output waveforms of the playback signals of the address signal track section (a) and the information signal track section (b) of a read-only disk recorded only with a concave-convex phase structure, and the amplitudes of the address signal section and the information signal section are equal. , the amplitude C is the amplitude a of the write-once disk.
,b is thicker than (a(b(c).

Problems to be Solved by the Invention As mentioned above, there are two types of discs: one is a record-once type disc in which recording is performed using a thermal change density, and the other is a disc in which recording is performed with a concave-convex phase structure as seen in a read-only disc. When attempting to reproduce the following with a single reproducing device, the reflectance of the two types of discs differs due to differences in recording materials and recording structures, and the amplitude of the reproduced signal differs depending on the disc. The problem with the configuration of the device was that two types of discs could not be played.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention distinguishes the two types of discs using a disc discriminator comprising, for example, a photodiode that detects the reflected light of the disc, When a disc is recorded using a signal based on the density of thermal changes, the address signal section and the information signal section are respectively detected and the amplitude levels of the respective reproduced signals are made equal.
The gain is switched so that the amplitude levels of the reproduced output signals from both disks are equal.

According to the present invention, with the above-described configuration, the reproduced output signals from the two types of disks are obtained with constant and equal amplitudes, so that the threshold level of the comparator of the subsequent signal processing circuit can be changed depending on the output amplitude of the reproduced signal. An optical signal reproducing device capable of reproducing two types of discs, which can be set at a constant level without any problem, is obtained.

Embodiment FIG. 1 is a block diagram showing an embodiment of the optical signal recording/reproducing apparatus of the present invention.

In FIG. 1, the components given the same numbers as those in FIG. 6 of the conventional example are the same as those in FIG. 5, and their explanations will be omitted. Further, components not particularly related to the present invention are omitted.

In FIG. 1, the disc discriminator 31 determines whether a disc (hereinafter referred to as the first disc) recorded with a thermally varied density or a disc (hereinafter referred to as the first disc) recorded with an uneven phase structure (
There are several possible configurations for this, but for example, it can be easily configured using a simple reflective photodetector that combines a light emitting diode and a photodiode. As mentioned in the conventional example, the first
The disk has a reflectance of about 10 to 20%, and the second disk has a reflectance of about 40%. When the reflectance is low, it is determined that it is the first disk, and when the reflectance is high, it is determined that it is the second disk. The type of disc is detected using this method, and the disc discrimination signal processing circuit 32 generates a digital signal that differs depending on the type of disc.
Controls the gain of the reproduced signal amplitude.

The reproduced light received by the photoelectric converter 14 is converted into an electrical signal and amplified by the head amplifier 16. The amplitude of the output signal of the head amplifier 15 at this time varies depending on the disc.
As shown in (I) and (n) in the figure.

(1) is the output signal amplitude of the first disk, (II) is the output signal amplitude of the second disk, (a) is the address signal section, and (b) is the information signal section.

In the case of the first disk, the amplitude a of the address signal section is smaller than the amplitude of the information signal section, and the output signal amplitude C of the second disk is the thickest (a(b(c) relationship).

Although three different amplitude levels are detected in this way, in the present invention, the reproduced output signal amplitude is controlled to a constant and equal level. In this case, any level of the amplitudes a, b, and c may be set. Here, as an example, it is assumed that the reproduced output signal amplitude is set to the level a.

The output signal of the head amplifier 16 is controlled by the discrimination control output signal of the disc discrimination signal processing circuit 32 in a gain switching circuit 33, and the gain of the amplitude of the reproduced output signal is switched. An example of the configuration of the gain switching circuit 33 is shown in FIG.

5o is an operational amplifier designed so that R2/R1=a/C, and the gain of the output signal is a/c times. For the first disc, the analog gate switch 61 is turned on and the analog gate switch 52 is turned off by the control signal from the disc discrimination signal processing circuit 32, and the gain of the reproduced signal amplitude remains the same.

For the second disk, the analog gate switch 61
is OFF, 52 is ON, and the gain of the reproduced signal amplitude is a
/ C multiplied by a.

The output signal of the gain switching circuit 33 is processed by an amplifier 34, an equalizer 35, and a low-pass filter 36 in order to reproduce the signal with good quality. Further, in order to detect the address signal section and the information signal section, the amplifier 37 amplifies the signal, the comparator 38 digitizes the address signal, the address signal detector 39 using a CPU etc. detects the address signal, and the information signal section gate signal is detected. is generated, and a reproduced output signal of only the information signal section is extracted. The reproduced output signal of the information signal section extracted in this way is further processed by the gain switching circuit 40 according to the disc discrimination signal from the disc discrimination signal processing circuit 32, so that when it is the first disc, the amplitude is increased by a /b times. Second
The gain is controlled so that it does not change when the disc is The configuration of this gain switching circuit 40 is similar to the gain switching circuit 33 described above, and an example of its configuration is shown in FIG. In Figure 3, 5Q is an amplifier whose gain is R1/R2
2a/b, the analog gate switch 51 is OFF and 52 is ON when it is the first disk, and the analog gate switch 51 is ○N52 when it is the second disk.
turns off. That is, as shown in FIG. 4, the output signal of the gain switching circuit 4o has an amplitude a for both the first disk and the second disk.

(+) indicates the first disk, and (It) indicates the second disk. The output signal thus obtained is binarized by the comparator 41, processed including demodulation by the signal processing circuit 42, and the information is reproduced as a digital signal, which is output as a reproduced signal from the signal output terminal 17. do.

Effects of the Invention As explained above, if the amplitudes of the reproduction output signals of the two types of disks are set to a constant level, the clipping level of the comparator can be set to a constant value, so both disks can operate stably. can.

In other words, a highly reliable optical signal reproducing device capable of reproducing two types of discs with a simple circuit configuration can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an optical recording/reproducing device showing an embodiment of the present invention, FIG. 2 is a waveform diagram showing a reproduction output signal of a disc, and FIG. 3 is a diagram of a gain switching circuit in an embodiment of the present invention. Fig. 4 is a waveform diagram showing the playback output signal of a gain-controlled disc, Fig. 5 is a block diagram of a conventional optical recording/reproducing device, and Fig. 6 is the configuration of an optical disc using a density recording method, and the optical disc. FIG. 7 is a diagram showing how signals are recorded on an optical disk of the uneven recording method and the reproduced signal waveform. A...Optical system, 1...Input terminal, 4.
... Semiconductor laser, 5, 8. River... Lens, 6.
Old r polarization beam splitter, 7...λ/4 plate, 9...Focusing element, 10...Disc, 11...Motor, 12... ...One revolution detector, 14...Photoelectric converter, 17...
... Output terminal, 60... Operational amplifier, 51.
52...Analog gate switch. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure (I) <X No. 4
Figure (1) (π) -Ile Kano fl Figure 6 C1 (1) 3°. Figure 7

Claims (2)

[Claims] (1) A guide track consisting of a groove-like structure is provided with address signals etc. formed discretely in a phase structure, and a light source such as a laser beam is focused on the guide track into a minute spot light to cause thermal changes. A first disk that reproduces signals on which information signals are given and recorded thereon, and a second disk on which address signals and information signals are prerecorded only in a phase structure on guide tracks consisting of groove-like structures are optically connected. The apparatus includes means for identifying and determining the first disc and the second disc, and controlling reproduction signal levels of the first disc and the second disc based on the identification result. An optical signal recording/reproducing device characterized by comprising a control means. (2) The control means controls the amplitude of the reproduction signal section of the phase structure section and the reproduction signal section formed by thermal change to the same level when the first disk is identified. 2. The optical signal recording and reproducing device according to claim 1.