JPH04103074A - Disk reproducing device - Google Patents

Abstract

PURPOSE:To make it possible to reproduce plural different types of disks only by one reproducing device by switching a gain switching means and a signal processing switching means in accordance with the output of a discriminating means for discriminating the 1st optical disk from the 2nd optical disk. CONSTITUTION:When an optical disk 1 is loaded to the reproducing device, the discriminating means 40 discriminates whether the loaded disk 1is the 1st optical disk or the 2nd optical disk and the gain switching circuit and the signal processing switching circuit in an RF circuit 31 are switched in accordance with the discriminated output. Namely, RF gain to the output of an optical head 30 is properly switched by the gain switching circuit in accordance with the difference of light reflection factors between the 1st and 2nd optical disks. On the other hand, the RF circuit 31 is switched by the signal processing switching circuit so as to form a reproducing signal processing circuit corre sponding to the difference of recording formats between the 1st and 2nd optical disks. Consequently, plural different kinds of optical disks can be reproduced by the same reproducing device.

Description

[Detailed description of the invention] [Industrial application field]

The present invention provides a disk playback device that can optically play back a plurality of types of disks, such as read-only optical disks and optical disks with different recording formats and different optical reflectances, such as rewritable magneto-optical disks. Regarding.

[Summary of the invention]

The present invention provides identification means for identifying a read-only first optical disc and a second disc having a different recording format and light reflectance, and uses the output of the identification means to identify the output of the optical head. The present invention provides a reproducing device that can automatically identify and reproduce a plurality of types of optical discs by switching a gain switching circuit and a signal processing switching circuit provided in an RF circuit that generates a reproduction signal.

[Conventional technology]

There are three types of optical discs currently known: read-only type, write-once type, and rewritable type. For example, a CD (compact disc), which is a type of playback-only optical disc, has digital audio data recorded on a transparent plastic disc using bit strings made by injection molding, etc., and the recording surface is made of aluminum. A metal reflective film such as the above is applied, and a protective film is further covered on top of the metal reflective film. Data is reproduced from this optical disc by detecting the intensity of the amount of light reflected from the pit row using the diffraction phenomenon of light. On the other hand, for example, a rewritable magneto-optical disk is, for example, TbF.
It has a structure in which a magneto-optical recording film (perpendicular magnetization film) made of a material such as eCo is deposited on a disk made of transparent plastic, and the top is covered with a protective film. In recording on this magneto-optical disk, a signal is recorded as the direction of magnetization using the magnetic field and the heat of the laser beam.Furthermore, the reproduction signal is detected according to the direction of magnetization when the magneto-optical disk is irradiated with a laser beam. This is done by utilizing the phenomenon in which the plane of polarization rotates (Kerr effect). As mentioned above, the recording formats are different between read-only optical discs and rewritable magneto-optical discs, and the playback formats are
Although the method of irradiating the disk with laser light and detecting the reflected light is the same, the difference lies in the way the reproduced signal is detected. Further, the light reflectance from the disk is about 115 when that of the read-only optical disk is 1, and that of the magneto-optical disk is also different. For this reason, conventionally, there has been a separate playback device for each type of optical disc.

[Problem to be solved by the invention]

However, if a separate playback device must be used depending on the type of disc to play an optical disc that can similarly reproduce optical signals, the cost burden on the user will increase and the operation will be cumbersome. . In view of the above points, it is an object of the present invention to enable a plurality of different types of discs to be played back by the same playback device.

[Means to solve the problem]

In order to achieve the above object, the disc reproducing apparatus according to the present invention includes identification means for identifying a first optical disc of a read-only type and a second optical disc having a different recording format and a different light reflectance from the first optical disc. , an optical head that rotationally drives the optical disk at a predetermined speed, and an RF circuit that generates a reproduction signal from the output of the optical head, and the RF circuit includes the first optical disk, the second optical disk, and the optical disk. A gain switching means for switching the gain and a signal processing switching means for switching the signal processing circuit are provided, and the gain switching means and the signal processing switching means are switched by the output of the identification means. 1. When an optical disc is loaded into the playback device, the identification means distinguishes whether the loaded disc is the first optical disc or the second optical disc, and the identification output is used to control the gain switching circuit and the RF circuit of the RF circuit. The signal processing switching circuit is switched. That is, the gain switching circuit switches the RF gain for the output of the optical head to be appropriate depending on the difference in light reflectance between the first optical disc and the second optical disc. In addition, the signal processing switching circuit allows the first
The RF circuit is switched so that the reproduction signal processing circuit corresponds to the difference in the recording format of the second optical disc.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. The embodiments described below are novel in that they are particularly able to reduce the size of the disc and the playback device, and are suitable for portable and vehicle-mounted devices. The following description will be made in the following order. 1. Two types of optical disk ■, recording/playback device 11 - (1) Recording system I of the recording/playback device A single playback device (or recording/playback device) for a rewritable optical disk and a rewritable magneto-optical disk.
Let's take as an example the case where you want to be able to play the file. In this example, the two types of optical discs have the same size, and their specifications are as follows. That is, as shown in FIG. 2, the outer diameter of the disk 1 is 64 fins, the center hole diameter d is 10 mm, and the signal recordable area W shown with diagonal lines has a diameter of 32 m1 or more. The thickness t of the disk 1 is 1.2 mm. Recording tracks are formed on the disk 1 in a spiral manner at a pitch of 1.6 μ. The disk 1 is rotated at a constant linear velocity of 1.2 to 1.4 m/s. In this example, as described later, the recorded information is compressed and recorded, so that the target information is 130M
It is possible to record and reproduce more than bytes. For example, in the case of an audio signal, for example, 44°1
When one sample is A/D converted to a 16-bit digital signal at a sampling frequency of kHz, by compressing this digital audio data to, for example, 1/4, the audio signal for two channels can be recorded for more than 60 minutes. It is made playable. In this example, the disk 1 includes two or more different types of disks, namely a read-only optical disk and a rewritable magneto-optical disk that has a magneto-optical recording film and is capable of recording, playback and erasing. provide. A read-only optical disc is a transparent plastic disc on which an information signal (in this case, a digital audio signal) is recorded by a bit string made by injection molding, etc., and the recording surface is covered with a material such as aluminum. A metal reflective film is applied, and a protective film is further covered on top of the metal reflective film. On the other hand, a rewritable magneto-optical disk is made of, for example, TbFeCo.
In this structure, a magneto-optical recording film (perpendicularly magnetized film) made of a material such as the above is deposited on a disk made of transparent plastic, and the top is covered with a protective film. In the case of a magneto-optical disk, as shown by the broken line in FIG.
The recording conditions and the like can be recorded in advance by a pit row made by an injection mold or the like in a portion P between 32 and 32. Furthermore, a pre-group for optical spot control (tracking control) is formed in advance on the disc 1, but in particular, in this example, a wobbling signal for tracking is superimposed on this pre-group. An absolute time code is recorded (see Japanese Unexamined Patent Publication No. 87682/1982). In this example, in the pit recording portion P of the magneto-optical disk, the range of this portion P is recorded as the above-mentioned absolute time, and the signal recording area W by magneto-optical recording is recorded.
It is designed to be used for area identification between this part P and this part P. Further, the optical reflectance of the read-only type optical disk and the above-mentioned magneto-optical disk is about 0.2, when that of the read-only type is taken as 1. In this example, the disc 1 is housed in a disc cartridge to prevent dust and scratches. FIG. 3 is a front view of a disc cartridge for a read-only optical disc, and FIG. 4 is a back view thereof. In the figure, 2 shows the cartridge as a whole, and 3 is a shirt plate. In FIG. 4, when the shirt cover plate 3 moves in the direction indicated by arrow A, the opening of the cartridge 2 is exposed, and the disc 1 inside is exposed to the outside. However, in the case of this read-only type, as shown in Figure 3,
There is no shirt opening on the front side of the disk cartridge 2, and a four-sided shadowed area 4, which is slightly smaller than the outer shape of the cartridge 2, is lower than its surroundings, and this area 4 has, for example, a picture or explanation indicating the recorded content. It is configured so that a label etc. included therein can be attached. Reference numeral 5 indicates a shutter lock member, and reference numeral 6 indicates a shutter return spring, which are housed in the cartridge 2. When the cartridge 2 is inserted from the cartridge insertion opening of the device in the insertion direction shown in the figure, the shutter plate 3 is It is used to lock the opening of the cartridge 2 in an exposed state and to close the shirt flap plate 3 again when the cartridge 2 is removed from the apparatus. Reference numeral 7 denotes an opening for inserting a spindle of a disk rotation drive motor of the recording or reproducing apparatus, and 8 and 9 are recessed holes into which positioning pins of the recording and reproducing apparatus are inserted when the cartridge 2 is inserted into the apparatus. 5 is a front view of the disk cartridge 12 for a rewritable magneto-optical disk, and FIG. 6 is a back view thereof. The cartridge 12 in this case has shirt openings on both the front and back sides. Therefore, when the shirt shirt plate 13 is moved in the direction of the arrow in FIG. 6, the disks 1 stored on both sides are exposed. In the case of this cartridge 12, unlike the cartridge 2, there is no area 4 where a label can be attached over almost the entire surface. The other is cartridge 2
15 is a shutter lock member, 16 is a shutter return spring, 17 is an opening for inserting a spindle of a disk rotation drive motor of a recording or reproducing device, and 18 and 19 are:
This is a recessed hole into which a positioning pin is inserted. In this example, the cartridges 2 and 12 have the same size, and as shown in FIGS. 3 and 5, the horizontal and vertical lengths a and b are a = 72 v*m, b - 68 ■
■The thickness has been selected as 5 dragons. In addition, as shown in FIGS. 4 and 6, the cartridge 2
Recessed holes (or protrusions) 10a and 10b are provided on the back side of the discs 12 and 12 for identifying whether the stored disc is a read-only type or a rewritable type. Further, on the back side of the disk cartridge 12, there is also a hole 10E for preventing accidental erasure.
is also provided. In addition, to prevent this accidental erasure,
For example, it is also possible to use a type in which the accidental erasure prevention claw used in micro-floppy disks is slidably moved. (2) Recording and reproducing device Next, an embodiment of the reproducing device according to the present invention will be described. In this example, an audio signal, for example, is recorded as an information signal on the disk 1 described above, and The following describes an example of a recording/reproducing apparatus that reproduces . FIG. 1 shows an embodiment of the recording/reproducing device, and this example is an I
By using C, we devised a way to simplify the configuration as much as possible. 11- (1) Recording system of recording/reproducing apparatus First, recording on a magneto-optical disk will be explained. Note that during recording and playback, the system controller 20
The modes of each circuit section are switched by a mode switching signal R/P from. A key manual operation section (not shown) is connected to the system controller 20, and an operation mode is designated by an input operation on this key manual operation section. Further, the identification recessed hole 10 a
The lob identifies whether or not the disk inserted into the device is a magneto-optical disk, and the identification output is supplied to the system controller 0-20. For example, a two-channel analog audio signal passed through the input terminal 21 is sampled at a sampling frequency of 44.1 kHz in an A/D converter 22, and each sampling value is converted into a 16-bit digital signal. This 16-bit digital signal is supplied to a data compression/expansion processing circuit 23. This data compression/expansion processing circuit 23 functions as a data compression circuit during recording, and in this example, input digital data is compressed to 1/4. Various methods can be used for this data compression, but for example, 4-bit quantization ADPCM (Adapt
ive De! ta Pu1se Code Modu
lation) can be used. Also, for example, input digital data can be divided into multiple bands such that the higher the frequency band, the wider the bandwidth, and each divided band has multiple samples (it is better to have the same number of samples in each band). It is also possible to use a method in which blocks are formed, orthogonal transformation is performed for each block in each band to obtain coefficient data, and bit allocation is performed for each block based on this coefficient data. The data compression method in this case takes into account the human hearing characteristics of sound, and can compress data with high efficiency (see Japanese Patent Application No. 1-278207). In this way, the digital data D from the A/D converter 22
A (FIG. 7A) is compressed to 1/4 by data compression processing in the circuit 23, and this compressed data da (FIG. 7B) is stored in the buffer memory 25 controlled by the track jump memory controller 24. will be forwarded to. In this example, the buffer memory 25 has 1
A D-RAM with a capacity of M bits is used. The memory controller 24 stores the compressed data da from the buffer memory 25 unless a track jump occurs in which the recording position on the disk 1 jumps due to vibration or the like during recording.
are sequentially read at a transfer speed four times the writing speed, and the read data is transferred to the data encode/decode circuit 26.
(C in the same figure). Further, when it is detected that a track jump has occurred during recording, the data transfer to the circuit 26 is stopped, and the compressed data da from the processing circuit 23 is stored in the buffer memory 25. Then, when the recording position is corrected, control is performed to resume data transfer from the buffer memory 25 to the circuit 26. Detection of whether a track jump has occurred can be performed by, for example, installing a vibration meter in the device and detecting whether the magnitude of vibration is such that a track jump has occurred. Furthermore, as described above, on the disc 1 of this example, an absolute time code is recorded superimposed on a wobbling signal for tracking control when forming a pre-group. Therefore, it is also possible to read the absolute time code from this pre-group at the time of recording and detect track jumps from the decoded output no.j. Alternatively, a track jump may be detected by ORing the vibration meter and the absolute time code. Note that when a track jump occurs, the power of the laser light for magneto-optical recording is reduced or the power is set to zero. Then, when a track jump occurs, the recording position can be corrected using the above-mentioned absolute time code. Furthermore, as can be understood from the above, the data capacity of the buffer memory 25 in this case is compressed data da corresponding to the time period from when a track jump occurs until the recording position is correctly corrected. A minimum storage capacity is required. In this example, the capacity of the buffer memory 25 has IM bits as described above, and this capacity is selected to have enough margin to fully satisfy the above conditions. Furthermore, in this case, the memory controller 24 performs memory control during normal operation during this recording so that as little data is stored in the buffer memory 25 as possible. For example, when the amount of data in the buffer memory 25 exceeds a predetermined amount, memory control is performed such that only a predetermined amount of data is read from the buffer memory 25 to always ensure a write space for more than the predetermined amount of data. conduct. The data encode/decode circuit 26 functions as an encode circuit during recording, and converts the compressed data da transferred from the buffer memory 25 into the sector structure of the CD-ROM.
encoded into approximately 2 bytes) of data. The output data of this data encode/decode circuit 26 is supplied to a recording encode circuit 27. In this recording encoder circuit 27, the data is subjected to an encoding process for error detection and correction, in this example CIRC encoding process, and a modulation process suitable for recording, in this example EF
Performs M encoding processing, etc. The encoded data from the recording encode circuit 27 is supplied to the magnetic head 29 via the magnetic head drive circuit 28. The magnetic head drive circuit 28 drives the magnetic head so as to apply a modulated magnetic field according to recording data to the disk 1 (magneto-optical disk). disc 1
The above recorded data is as shown in Figure 7. In this case, the magneto-optical disk 1 is housed in the cartridge 12, but when it is loaded into the apparatus, the shirt flap plate 15 is opened and the disk 1 is exposed from the shirt flap opening. A rotating shaft of a disk drive motor 30M is inserted into and connected to the spindle hole 15, and the disk 1 is rotationally driven at a linear velocity of 1.2 to 1.4 degrees. The disk drive motor 30M is controlled to have a constant linear velocity by a servo control circuit 32, which will be described later. The magnetic head 29 faces the disk 1 exposed through the shirt opening of the cartridge 12. Further, an optical head 30 is provided at a position facing the surface of the disk 1 opposite to the surface facing the magnetic head. During recording, this optical head 30 has the following information on the recording track:
A laser beam with a constant power greater than that during reproduction is irradiated. By this light irradiation and the modulated magnetic field by the magnetic head 29, data is recorded on the disk 1 by thermomagnetic recording. Both the magnetic head 29 and the optical head 30 are connected to the disk 1.
It is configured so that it can move along the radial direction. Note that during this recording, the output of the optical head 30 is R.
The signal is supplied via the F circuit 31 to an absolute time decoding circuit 34, where the absolute time code from the pre-group of the disc is extracted and decoded. The decoded absolute time information is then supplied to the recording encoder circuit 27, inserted into the recording data as absolute time information, and recorded on the disc. Absolute time decoding circuit 34
The absolute time information from system controller 2 is also
0 and is used for recording position recognition and position control as described above. 11- (2) Reproduction System of Recording and Reproducing Apparatus The apparatus of this example is capable of reproducing two types of disks: a read-only optical disk and a rewritable magneto-optical disk. These two types of disks can be identified by detecting the identification holes 10a and 10b provided in each disk cartridge 2 and 12, as described above. For example, a disc cartridge 2 for a playback-only disc has two identification holes 10a and 10b.
Only the recessed hole 10a is formed, and the disk cartridge 12 for the magneto-optical disk has two recessed holes 10a. 10b. As a result, when the cartridge 2 or 12 is loaded into the device, the recessed hole 1 for singing
By detecting the numbers 0a and 10b, it is possible to identify which cartridge it is. Furthermore, since the light reflectance of read-only and rewritable discs differs by 1:0.2 as described above, it is also possible to distinguish between the two types of discs from the output of the optical head 30. . The reproduction system of the example shown in FIG. 1 is provided with a disc identification circuit 40 for identifying two types of discs based on the difference in light reflectance, as will be described later. The disk loaded in the recording/reproducing device is rotationally driven by a disk drive motor 30M. Then, in the same manner as during recording, the servo control circuit 32 causes the disk drive motor 30M to drive the disk 1 at a linear velocity of 1.2 to 1.4.
The rotational speed is controlled to be constant at m/s. During reproduction, the optical head 30 detects a focus error by, for example, an astigmatism method by detecting the reflected light of the laser light irradiated on the target track, and also detects a tracking error by, for example, a push-pull method. In the case of a read-only optical disc, the reproduction signal is detected by using the diffraction phenomenon of light in the pit row of the target track, and in the case of a rewritable magneto-optical disc, the polarization angle ( The reproduction signal is detected by detecting the difference in the car rotation angle). FIG. 8 shows an example of the configuration of the optical head 30. In the figure, a laser beam from a semiconductor laser 301 is converted into a parallel beam by a collimator lens 302, divided into three beams by a diffraction grating 303, and then enters a polarizing beam splitter 304. The three laser beams whose optical axis directions have been changed by the polarizing beam splitter 304 are converged by the objective lens 305 and are incident on the disk 1. Further, a part of the laser beam incident on the beam splitter 304 is changed in its optical axis direction and is incident on a photodetector 306. is detected. The light receiving output of this photodetector 306 is supplied to a power control circuit 311. The power control circuit 311 controls the emission power of the semiconductor laser 301 to a predetermined value based on the amount of received light. And the laser beams (3 beams) reflected by disk 1
is the polarizing beam splitter 3 via the objective lens 305.
04, the direction of the optical axis is changed, and the light enters the Wollaston prism 307. In this Wallaston prism 307, the incident light has orthogonal polarization components,
That is, the P polarized light component is separated into the P polarized light component and the S polarized light component, and the P polarized light component is directed upward in the first beam direction (P) in FIG.
The S polarized light component is in the downward second beam direction (S). Further, from this Wallaston prism 307, a composite component of the P-polarized light component and the S-polarized light component has the same optical axis direction as the incident reflected laser beam.
is obtained in a direction intermediate between the beam directions of . In this case, in the figure, the three laser beams that are incident on the Wallaston prism 307 are lined up in a direction perpendicular to the plane of the paper, and are separated into a P-polarized component, an S-polarized component, and their composite component as described above. By doing so, a total of nine beams will be obtained. The reflected laser beams in the first beam direction (P) and the second beam direction (S) enter the photodetection unit 50 through the condenser lens 308, and the reflected laser beam in the third beam direction enters the photodetection unit 50. , enters the light detection unit 50 through the condensing lens 308 and the refractive lens 309. The photodetection unit 50 is composed of a plurality of photodetection elements, and in this example, as shown in FIG. 9, there are four photodetection elements 50A, 50B, and 50C in the center. A photodetecting element group 51 consisting of 50D is provided, and
There are photodetecting elements 50 at the left and right positions of this photodetecting element group 51.
A photodetecting element 50I and a photodetecting element 50J are provided above and below the photodetecting element group 51. Of the reflected laser beams that enter the photodetection unit 50, three laser beams in the third beam direction enter the photodetection elements 5.0E and 50F and the photodetection element group 51. Further, the reflected laser beam at the center of the three beams in the first beam direction, that is, the P-polarized light component, is detected by the photodetecting element 50.
1 and the reflected laser beam at the center of the three beams in the second beam direction, that is, the S-polarized component, enters the photodetector element 50J. Then, the detection outputs of each of the photodetecting elements 50A to 50J, which are the outputs of the optical head 30, are supplied to the RF circuit 31. The RF circuit 31 detects the reflected laser beam at the perpendicular magnetization film of the magneto-optical disk by mutually comparing the detection output of the P-polarized light component by the photodetector 50I and the detection output of the S-polarization component by the photodetector 50J. Detects the rotation of the plane of polarization received by DRF, and uses the comparison output to have a change corresponding to the rotation of the plane of polarization.
form. And this information signal. Generate playback data from. Furthermore, when reproducing from a read-only optical disc, the diffraction phenomenon of the laser beam is used to generate reproduced data as the strength and weakness of the detected amount of light.
Detection output of P polarized light component by 01 and photodetector element 50J
The read information signal DRF is formed from the sum of the detected output of the S polarized light component by Therefore, in the RF circuit 31, the signal processing circuit is switched using the disc identification output, and in the case of a magneto-optical disc, the difference between the P polarization component and the S polarization component (comparison output) is obtained.
In the case of a read-only type disk, the read information signal DRF from both the magneto-optical disk and the read-only type disk is obtained by obtaining the sum of the P polarization component and the S polarization component.
data playback becomes possible. The RF circuit 31 also detects a change in the reflected laser beam from a wobbling track for tracking servo provided on the disk by detecting a change in the reflected laser beam from a photodetecting element 50E of the photodetecting unit 50.
and 50F, a tracking error signal is formed using the photodetection outputs of these photodetection elements 50E and 50F. Furthermore, by detecting the beam spot shape on the photodetecting element group 51 using the detection outputs of the four photodetecting elements 50A to 50D, a focus error signal of the laser beam incident on the disk is formed. In addition, the RF circuit 31 switches the RF gain of the read information signal forming circuit system in consideration of the difference in optical reflectance between read-only disks and magneto-optical disks, and also switches the RF gain of each servo error signal forming circuit system. Make the gain switchable. FIG. 10 shows an example of the circuit configuration of this RF circuit 31. That is, the photodetection outputs Ll and LJ of the photodetection elements 50I and 50J of the photodetection unit 50 are amplified by operational amplifiers 101 and 102, respectively. Then, the sum of the outputs of these operational amplifiers 101 and 102 is obtained from the operational amplifier 103, and the sum of the outputs is obtained from the switch circuit S.
It is supplied to one input terminal P of WI. Further, the output of the operational amplifier 101 and the output of the operational amplifier 102 are inputted to a differential amplifier 104, and an output of the difference between the output of the operational amplifier 101 and the output of the operational amplifier 102 is obtained from the differential amplifier 104, and the output of the difference is sent to the switch. It is supplied to the other input terminal M of the circuit SW. This switch circuit SW1 is configured to switch between playback from a read-only type disk and playback from a magneto-optical disk based on a switching signal from the system controller 20 formed from the identification output of a disk sorting circuit 40, which will be described later. When reproducing data from a recorded portion by pits from portion P of the disk 1, the input end is switched to one side P, and the output is detected by light and the sum of I and LJ is obtained at the output end 105 as an output signal DRF. , when reproducing from the magneto-optical recording area W of the magneto-optical disk, the input end is switched to the other M side, and the output of the difference between the photodetection outputs Ll and LJ becomes the output signal D.
The signal is obtained as RF at the output terminal 105. Additionally, the operational amplifier 103 is provided with a switch circuit SCM for switching the gain, and when a playback-only disc is played back, the switch circuit SG is switched on in response to a switching signal from the system controller 20. is turned on and the gain is set to GA, and when the portion P of the magneto-optical disk is reproduced, it is turned off and the gain is set to about 50A. Note that the gain of the differential amplifier 104 is approximately 30GA. Further, the photodetection outputs LE and LF of the photodetection elements 50E and 50F are amplified by operational amplifiers 106 and 107, respectively, and then supplied to one input terminal and the other input terminal of a differential amplifier 108, respectively. From 108, the output of the difference between the photodetection outputs LE and LF is obtained. The output of this differential amplifier 108 corresponds to the amount of tracking deviation, and the output of this difference is supplied to one input terminal I of the switch circuit SW2, and is also supplied to the other input terminal I of the switch circuit SW via the inverting amplifier 109. It is supplied to the input terminal N. This switch circuit SW2 is connected to the system controller 20
The input end is switched to the other input terminal N side by a switching signal from the input terminal when reproducing from a read-only disk and when reproducing from a magneto-optical disk, and when reproducing from a recorded portion using bits from portion P. Further, when reproducing from the magneto-optical recording area W of the magneto-optical disk, the input terminal is switched to one input end I side. This switching occurs when playing from a read-only disk and when playing from a magneto-optical disk.
When playing back from the recorded part by pits from part P,
The tracking servo uses a three-spot method, and when reproducing from the magneto-optical recording area W of the magneto-optical disk, the push-pull method is used, so it is necessary to change the polarity of the tracking error signal in both tracking servo methods. It is. Then, the output of the switch circuit SW2 is output from the operational amplifier 110.
The output is obtained as the tracking error signal Te at the output terminal 111, and its gain is switched by the switch circuit SG2. That is, according to the switching signal from the system controller 20, when playing a read-only type disk, the switch circuit S62 is turned on and the gain is set to GT, and when playing a magneto-optical disk, the switch circuit S02 is turned off. and the gain is set to 5GT. Further, after the sum of the photodetection output LA of the photodetection element 50A of the photodetection element group 51 of the photodetection unit 50 and the photodetection output LC of the photodetection element 50C is amplified by the operational amplifier 112,
The sum of the photodetection output LB of the photodetection element 50B and the photodetection output LD of the photodetection element 50D is amplified by the operational amplifier 113, and then the differential amplifier 114 is supplied to one input terminal of the differential amplifier 114. The differential amplifier 114 outputs the difference between the signals supplied to both input terminals corresponding to the amount of focus error. The output of this differential amplifier 114 corresponds to the amount of focus error, and the output of this differential amplifier is the output of the operational amplifier 115.
The gain is switched by the switch circuit SG3, and the output thereof is obtained as the focus error signal Fe at the output terminal 116. That is, according to the switching signal from the system controller 20, when playing a read-only type disk, the switch circuit S03 is turned on and the gain is set to GF, and when playing a magneto-optical disk, the switch circuit SG3 is turned off. and the gain is set to 5GF. In this way, the tracking error signal Te obtained at the output terminal 111 of the RF circuit 31 and the focus error signal Fe obtained at the output terminal 116 are supplied to the servo control circuit 32. The servo control circuit 32 receives the focus error signal Fe.
The focus control of the optical system of the optical head 30 is performed so that the value becomes zero, and the tracking control of the optical system of the optical head 30 is performed so that the tracking error signal Te becomes zero. Further, although not shown, a part of the signal for detecting the tracking error Te of the RF circuit 31 is supplied to the absolute time decoding circuit 34 in order to extract the absolute time code from the blip probe. And system controller 2
Absolute time information from the decoding circuit 34 is supplied to the decoding circuit 34, and is used for playback position control as necessary. Furthermore, the system controller 20 can also use sector-by-sector address information extracted from the reproduced data to manage the position on the recording track that the optical head 30 is scanning. In this example, identification of the two types of optical disks and identification of the recording area W and portion P of the magneto-optical disk are performed as follows. That is, the operational amplifiers 101 and 102 of the RF circuit 31
The outputs X and Y of are proportional to the reflected laser beam from the optical disc, and are proportional to the reflectance of the optical disc. Therefore, these outputs X and Y are input manually to the disk identification circuit 4o. FIG. 11 shows an embodiment of the disk identification circuit 40, in which the sum signal of the output X and the output Y is sent to the operational amplifier 41.
After being amplified by, the signal is supplied to first and second comparison circuits 42 and 45. Then, in the first comparison circuit 42,
The DC power source 4 is compared with the lth threshold value VT by the DC power source 43.
6 is compared with a second threshold value vT2. In this case, the optical reflectance of the read-only disc is high, and the output of the operational amplifier 41 during playback is large, as shown by the solid line 61 in FIG. On the other hand, the optical reflectance of the magneto-optical disk is about 115 for the read-only type, and the output of the operational amplifier 41 during playback is small as shown by the solid line 62 in FIG. Therefore, the first and second threshold values VT
, and VT2 are, in this example, as shown in FIG.
VT, < VT2. In this way, if the disc loaded in the device is of the playback-only type, the output of the comparator circuit 42 is "1" and the output of the comparator circuit 45 is "0".
'', and if it is a magneto-optical disk, the output of the comparator circuit 42 will be "1" and the output of the comparator circuit 45 will also be "1". The outputs of these comparison circuits 42 and 45 are respectively output from output terminal 4.
4 and 47 to the system controller 20. In the system controller 20, the output signal of the output terminal 44 is "1" and the output signal of the output terminal 47 is "1".
0", the disc loaded in the device is identified as a playback-only disc, and the output signal from the output terminal 44 is "0".
1'', and when the output signal of the output terminal 47 is ``1'', the disk loaded in the device is identified as a magneto-optical disk. Furthermore, the system controller 20 detects the absolute time indicating the area of the portion P based on the decoded output of data from the portion P of the magneto-optical disk. Then, the portion P and the signal recording area W are distinguished from each other based on the absolute time from the absolute time decoding circuit 34. Based on the above two identification outputs, the system controller 20 selects each of the above-mentioned switch circuits SW, , S.
W2. SG, to SG3 switching signals are formed. Next, the read information signal DRF obtained at the output terminal 105 of the RF circuit 31 is waveform-shaped and binarized, and then supplied to the reproduction encoding circuit 33. The reproduction decoding circuit 33 receives the binary reproduction signal from the RF circuit 31 and performs processing corresponding to the recording encoding circuit 27, that is, decoding processing for error detection and correction, and
Performs FM decoding processing, etc. The output data of the reproduction decoding circuit 33 is supplied to the data encoding/decoding circuit 26. The data encode/decode circuit 26 functions as a decode circuit during reproduction and decodes data in the sector structure of the CD-ROM into compressed original data. Note that in this data encode/decode circuit 26,
Upon receiving the disc identification data from the system controller 20, when a part where a track jump occurs during recording is detected during playback of a magneto-optical disc, data joint processing at the track jump part is performed as necessary. Let's do it. The track jump position can be detected, for example, by inserting information indicating this into the recorded data. The output data of this data encode/decode circuit 26 is transferred to a buffer memory 25 controlled by a track jump memory controller 24 and written at a predetermined writing speed. During this playback, the memory controller 2
4, if there is no track jump that causes the playback position to jump due to vibration etc. during playback, the compressed data from Dedanin Code/Lever 26 will be written at 1/4 times the writing speed. The data is sequentially read out at a transfer speed and the read data is transferred to the data compression/expansion processing circuit 23. Further, when it is detected that a track jump has occurred during playback, writing of data from the circuit 26 to the buffer memory 25 is stopped, and the data compression/expansion processing circuit 23
It only transfers data to. Then, when the reproduction position is corrected, control is performed so that data writing from the circuit 26 to the buffer memory 25 is restarted. Detection of whether or not a track jump has occurred can be performed in the same way as during recording, for example, by using a vibration meter or by using an absolute time code that is recorded in the pre-group of the optical disc so as to be superimposed on a wobbling signal for tracking control. (that is, a method using the decoded output of the absolute time decoding circuit 34), or a method of detecting a track jump by ORing the vibration meter and the absolute time code. Furthermore, during this reproduction, since absolute time information and sector-based address information are extracted from the reproduced data as described above, these can also be used. Note that, as described above, track position control such as correction of the playback position when a track jump occurs can use the address information in addition to the absolute time code described above. As can be understood from the above, the data capacity of the buffer memory 25 during playback is always equal to the amount of data corresponding to the time from when a track jump occurs until the playback position is correctly corrected. A minimum storage capacity is required. This is because, with that much capacity, data can continue to be transferred from the buffer memory 25 to the data compression/expansion circuit 23 even if a track jump occurs. The capacity of the buffer memory 25 in this example is 1 Mbit, which is selected as a sufficient capacity to fully satisfy the above-mentioned conditions. Furthermore, in this case, the memory controller 24 performs memory control during normal operation during this playback so that the buffer memory 25 stores as much predetermined data as possible than the minimum necessary amount. For example, when the amount of data in the buffer memory 25 becomes less than or equal to a predetermined amount, data is written from the circuit 26, and memory control is performed so as to always ensure a reading space of more than the predetermined amount of data. The data compression/expansion processing circuit 23 functions as a data expansion circuit during playback, and converts the ADPCM data from the data compression/expansion circuit 23 to 0.4 times by performing a conversion process that is inverse to the data compression process during recording. The digital audio data is supplied to the D/A converter 35, returned to a two-channel analog audio signal, and output to the output terminal 3.
Output from 6. In this example, the digital audio data before D/A conversion can also be output from the output terminal 37 as is. The disks of the embodiments described above are very compact, having an outer diameter of 80 cm or less, and are very useful for downsizing recording and reproducing devices. Moreover, since the data is compressed and recorded on this small disk, it is possible to record and play back audio signals for more than 60 minutes.Furthermore, by making the disk smaller, the recording capacity can be increased. It will not deteriorate. Further, in this embodiment, a buffer memory is provided between the data compression means and the recording encode means in the recording system, and between the reproduction decoding means and the data decompression means in the reproduction system.
By setting the capacity of this buffer memory to a predetermined value, even if a track jump occurs and the recording position or playback position jumps during recording or playback, discontinuity of the recorded signal will not occur on the disk. In addition to being able to record continuously without causing any unnatural interruptions or noise, the reproduced signal can be reproduced without causing any unnatural interruptions or noise. In this way, in this embodiment, measures against track jumps are taken through signal processing, so there is no need to use an anti-vibration structure to prevent vibrations, which greatly contributes to the miniaturization of recording and reproducing devices. . In addition, stronger vibration countermeasures can be taken by using a vibration isolation structure for vibration countermeasures, but even in that case, the vibration isolation structure is relatively simple and the structure is small. Since the recording device and the reproducing device can be made smaller, the recording device and the reproducing device can be made smaller. Therefore, if the recording/reproducing apparatus of this embodiment is applied to a portable or vehicle-mounted disk recording/reproducing apparatus,
The effect is remarkable. ③ Modification As mentioned above, the optical disk to which this invention is applied is not limited to read-only type optical disks and magneto-optical disks, but may also be read-only type and write-once type optical disks. Of course. Furthermore, instead of a magneto-optical disk, two types of optical disks may be used: a phase-change type rewritable optical disk that utilizes the phase change of crystal-7 morphus, and a read-only type optical disk. Furthermore, the present invention is applicable to the case where three or more types of optical discs are to be reproduced instead of two types of optical discs. Note that the recorded information is not limited to audio signals only, but may also include video signals and characters. It is also possible to record graphic pattern signals, code conversion signals, map information, and other various data. Further, as a means for identifying the disk, an identification mark formed on the disk cartridge may be used, and the identification mark is not limited to a recessed hole or a protrusion as in the embodiment shown in the figure. An identification bar code or the like may be provided at one of the locations on the disc or a label attached thereto. In addition, the part that is switched according to the disc identification output is the gain and signal processing circuit in the RF circuit 31 in the above example, but depending on the difference in the signal reproduction method depending on the recording method of the optical disc, the part that is switched according to the disc identification output is the circuit at the later stage than the RF circuit. If it is necessary to switch the signal processing circuit of the disc, it goes without saying that that part should also be switched in accordance with the disc identification output.

【Effect of the invention】

As explained above, the disc playback device according to the present invention is provided with means for identifying a plurality of types of optical discs that can all be optically played, and based on the identification output thereof,
Since the gain of the RF circuit and the signal processing circuit are switched, it becomes possible to reproduce a plurality of types of optical discs with different recording methods and different light reflectances using the same reproduction device. In addition, since the circuit configuration after the RF circuit can be made common to multiple types of optical discs, it is possible to make the configuration of the circuit after the RF circuit the same for multiple types of optical discs. The configuration can be greatly simplified and can be configured at low cost.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of a recording and reproducing apparatus to which a disc reproducing apparatus according to the present invention is applied, FIG. 2 is a diagram for explaining an embodiment of an optical disc to be recorded and reproduced, and FIG. 6 to 6 are diagrams showing examples of disk cartridges that accommodate the optical disk, FIG. 7 is a time chart for explaining the recording system, and FIG. 8 is an optical head 3.
9 is a diagram showing an example of the photodetection unit, FIG. 10 is a circuit diagram of an example of an RF circuit, and FIG. 11 is a circuit diagram of an example of a disc identification circuit. FIG. 12 is a diagram showing the output of the optical head. 1: Disk 2: Cartridge 12 for read-only optical disk; Cartridge 10a, 10b for magneto-optical disk; Concave hole 20 for disk separation; System controller 23; Data compression/expansion processing circuit 30; Optical head 31; RF circuit 33; Reproduction Decoding circuit 40; disk identification circuit sw,, sw, , switch circuit for signal processing circuit switching SGI, sc,, sc3; switch circuit agent for RF gain switching Patent attorney Tadashi Sato Miti Matari ψ-Example Figure 2: Cartridge for Isamu 1 G M-type Tesisku Figure 3: Isamu-1 exclusive ljA 11 stone figure 6 series Kensen Uni 1. Father Figure 9

Claims (3)

[Claims] (1) Identification means for identifying a read-only first optical disc and a second optical disc that has a different recording format and a different light reflectance; and an optical head that rotates the optical disc at a predetermined speed. and an RF circuit that generates a reproduction signal from the output of the optical head, and the RF circuit includes gain switching means for switching gains between the first optical disc and the second optical disc, and a signal processing circuit. 1. A disc playback device comprising: signal processing switching means for switching between the gain switching means and the signal processing switching means, the gain switching means and the signal processing switching means being switched based on the output of the identification means. (2) The disc reproducing apparatus according to claim 1, wherein the identification means identifies the first optical disc and the second optical disc based on a difference in light reflectance. (3) The first and second optical discs are each housed in a cartridge, and the identification means performs identification by detecting a disc identification mark provided on the cartridge. Disc playback device described.