Optical disk apparatus

Abstract: The invention is intended to digitize a first signal, reproduce or record and reproduce the digital information compressed in band up to a specified bit rate A1 at a specified rotating speed K or specified linear velocity V, digitize a second signal, reproduce or record and reproduce the digital information compressed in band up to a specified bit rate A2 at a rotating speed of about K x A2/A1, or a linear velocity of about V x A2/A1, and thereby reproduce or record and reproduce information of plural signals, or reproduce or record and reproduce information of plural compression rates by one unit. It is also intended to digitize a first signal, reproduce or record and reproduce the digital information compressed in band up to a specified bit rate A1 in n optical channels, digitize a second information, reproduce or record and reproduce the digital information compressed in band up to a specified bit rate A2 in about n x A2/A1 optical channels, and thereby reproduce or record and reproduce information of plural signals, or reproduce or record and reproduce information of plural compression rates by one unit without notably varying the rotating speed or linear velocity. It is further intended to enter the light emitted from a semiconductor laser into a nonlinear optical device (SHG), and reproduce the information on a disk surface or record and reproduce the information on a disk surface by the secondary harmonics delivered from the nonlinear optical device.

Description: The present invention relates to an optical disk apparatus capable of reproducing or both recording and reproducing of signals which are greatly different in the frequency band from each other, such as an NTSC signal and a high definition television (HDTV) signal. Optical disk apparatuses capable of reproducing or both recording and reproducing one of an NTSC signal and a high definition television signal have been distributed and reported hitherto. However, all of them are of analog recording type and optimally designed for individual signal bands, so that they are not compatible to each other. In the case of digital recording, the quantity of information is by far greater than that in the analog recording. So, it was not realistic to employ the digital recording in the aspects of reduction recording and reproducing time and extension of transfer rate. In other words, there was no optical disk apparatus capable of reproducing or both recording and reproducing both the NTSC signal and the high definition television signal. Even in case that the recording signals are of the same type, there was no optical disk apparatus capable of reproducing or both recording and reproducing in both of a low-definition, long-playing mode at a high compression rate and a high-definition, short-playing mode at a low compression rate. In the article "Optical Video Disc System for HDTV" (Conference Proceedings, Signal Processing of HDTV II, 1989, Amsterdam NL; pages 519-526) by H Sacki et al, there is described a system which reproduces HDTV images with digital audio. The system design is based on 2-Channel recording and playback technology, and a 20-MHz bandwidth luminance signal and a 6-MHz bandwidth line-sequential chrominance signal are recorded without bandwidth compression. The article "A Write-Once Video Disc Recording system Using Time-Division Multiplexing" (IEEE 1990 International Conference on Consumer Electronics Digest of Technical Papers, June 1990, New York, US; pages 42,43) by H Owa et al describes a video disc recording system for recording pictures with digital audio. By virtue of time-division multiplexing with an analog component, it is stated that a high quality picture may be produced. It is hence a primary object of the invention to provide a high recording density optical disk apparatus capable of reproducing or both recording and reproducing both a narrow band signal such as an NTSC signal and a wide band signal such as a high definition television (HDTV) signal, and capable of reproducing a signal in plural modes including a low-definition, long-playing mode at a high compression rate and a high-definition, short-playing mode at a low compression rate. Another object of the invention is to raise the recording density greatly by inserting a nonlinear optical device (SHG) into an optical system for reproducing or both recording and reproducing a signal by using secondary harmonics. Generally to achieve the above objects, in one aspect of the present invention, an optical disk apparatus is configured to digitize a first signal, and reproduce or both record and reproduce a digital data compressed in band down to a specified bit rate A1 at a specified disk rotating speed K or a specified linear velocity V, and, on the other hand, digitize a second signal, and reproduce or botb record and reproduce a digital data compressed in band down to a specified bit rate A2 at a disk rotating speed of substantially K × A2/A1 or a linear velocity of substantially V × A2/A1. With this configuration, it is possible to reproduce or both record and reproduce any one of plural signals which are different from each other in frequency band or compression rate. In another aspect of the present invention, an optical disk apparatus is configured to digitize a first signal, and reproduce or both record and reproduce a digital data compressed in band down to a specified bit rate A1 in n optical channels, and, on the other hand, digitize a second signal, and reproduce or both record and reproduce a digital data compressed in band down to a specified bit rate A2 in substantially n × A2/A1 optical channels. With this configuration, it is possible to record and/or reproduce any one of plural signals which are different from each other in frequency band or compression rate without notably varying the disk rotating speed or linear velocity. In still another aspect of the present invention, an optical disk apparatus may be configured to enter a light emitted from a semiconductor laser into a nonlinear optical device (SHG), and reproduce data recorded on a disk surface or both record data onto and reproduce data from the disk surface by secondary harmonics outputted from the nonlinear optical device. With this configuration, it is possible to extremely increase the recording density. According to the present invention, there is provided an optical disc apparatus for reproducing a digital signal recorded on a recording disk as set out in the independent claims 1 and 12. Detailed embodiments are set out in the dependent claims. According to some embodiments of the present invention, an optical disk apparatus may be configured to enter light emitted from a semiconductor laser into a nonlinear optical device (SHG), and reproduce data recorded on a disk surface or both record data onto and reproduce data from the disk surface by secondary harmonics outputted from the nonlinear optical device. With this configuration, it is possible to extremely increase the recording density. Fig. 1 is a block diagram of a reproducing system of an optical disk apparatus of the invention, Fig. 2 is a block diagram of a recording system for use with embodiments of an optical disk apparatus of the invention, Fig. 3 is an example of a disk for use with embodiments of the invention, Fig. 4 is a block diagram of an optical system for use in an embodiment an optical disk apparatus of the invention, and Fig. 5 is a diagram showing a relation of signal, mode and other parameters in an embodiment of the invention. Fig. 1 is an embodiment of a reproducing system of an optical disk apparatus of the invention. Information recorded on an optical disk 1 is read by an optical systems 2 and 3 including an optical head, and is sent into a digital demodulator 4. In the digital demodulator 4, the information is demodulated into a digital signal, and error correction or other processing is done at the same time. In a mode judging circuit 6, the type and mode of the signal of the reproduced information are judged from the information from the digital demodulator 4. The output of the digital demodulator 4 is decoded by a band-compressing decoder 9 on the basis of the information from the mode judging circuit 6. The signal decoded and expanded in band is digital-to-analog (D/A) converted in an output circuit 10, and delivered to an output terminal 11. A motor driving circuit 7 for controlling a motor 8 controls the motor 8 depending on the information from the digital demodulator 4 and mode judging circuit 6 so that the disk rotating speed or the linear velocity of the optical head relative to the disk becomes a specified value. A reproduced signal processing circuit 22 is composed of said digital demodulator 4, band-compressing decoder 9, and output circuit 10. If, meanwhile, the transfer rate is low, only one channel optical system 2 may be used, and the optical system 3 may be omitted. Here, the operation of the mode judging circuit 6 is to control the motor 8 so that the linear velocity of the optical head relative to the disk becomes a specified value. Or it is to operate only a required channel of the optical system, which may be realized, for example, by selecting only the necessary information out of the input information in the digital demodulator 4. In the case of a reproducing only machine, it is sufficient with the reproducing system described above, but in the case of a recording and reproducing machine, a recording system is also needed. Referring then to Fig. 2, an embodiment of a recording system of an optical disk apparatus is explained. The common blocks as in Fig. 1 are identified with the same reference numbers. A signal entered from an input terminal 15 is analog-to-digital (A/D) converted in an input circuit 16, and is encoded to a specified bit rate signal by a band-compressing encoder 17. This result is fed into a digital modulator 19 to be subjected to processing such as addition of error correction code, and is digitally modulated. Laser beams generated in optical systems 20, 21 are modulated by the digital modulated signal, so that digital information is recorded on an optical disk 1. A motor 8 is controlled by a motor driving circuit 7 so as to achieve a specified rotating speed of the disk or a specified linear velocity of the optical head relative to the disk. A recorded signal processing circuit 23 is composed of the input circuit 16, band-compressing encoder 17, and digital modulator 19. All of the motor driving circuit 7, digital modulator 19, and encoder 17 are controlled by the information from a mode specifying circuit 18 so as to operate as specified. If it is enough with the operation of one channel of optical system in low transfer rate application, the optical system 21 is not needed. The mode specifying circuit 18 is to specify the mode by means of, for example, a switch operated by an operator. As the mode judging method in the mode judging circuit 6 in reproduction, various methods may be considered including a method of, as shown in Fig. 3, recording a coded mode signal on a reference position of the disk, for example, a position on each track on a specific line in the radial direction, and judging the mode by reproducing the mode signal from the reference position. The optical systems 2, 3, 20, 21 of Figures 1 and 2 are shown in detail in Fig. 4. The optical system comprises a semiconductor laser 30, coupling lenses 31, 33, a nonlinear optical device (SHG) 32,' a long wavelength cut filter 34, a beam splitter 35, an objective lens 36, a detector 38, and a laser driving circuit 37. In recording, the modulation signal is fed into the laser driving circuit 37. In reproducing, a reproduced signal is delivered from the detector 38. By inserting the SHG 32, the laser wavelength becomes 1/2, so that the recording density on the disk can be increased about four times. As the SHG 32, the waveguide type is desired when recording and reproducing, but when reproducing only, it may be either waveguide type or bulk type. Fig. 5 shows an example of reproducing or recording and reproducing plural signals having different bands at plural compression rates, by using thus composed optical disk. This is to show the relationship of the linear velocity, number of optical system channels and reproduction time in CLV, and the relationship of the disk rotating speed, number of optical system channels and reproduction time in CAV, when the narrow band, NTSC signal is compressed in band to 5 Mbps and 10 Mbps, and when the wide band, high definition television signal (HDTV) is compressed in band to 30 Mbps and 60 Mbps. In Fig. 5A, the linear velocity is constant, and in Fig. 5B, the disk rotating speed is constant. Supposing, in Fig. 5A, the linear velocity at NTSC signar of 5 Mbps to be V and the reproduction time to be 12T 1 , the linear velocity at HD signal of 30 Mbps is 3V in a two-channel optical system, or 6V in a one-channel optical system, and the reproduction time is respectively 2T 1 . The same holds true in Fig. 5B where the disk rotating speed is constant. In the same signals, the greater the bit rate after band compression, the shorter becomes the reproduction time and hence a picture of high quality is reproduced. In the foregoing embodiments, the reproducing system and recording system are explained separately, but the invention is similarly applied either in the optical disk apparatus for recording and reproducing by one unit or in the optical disk apparatus for reproducing only. Incidentally, the narrow band signals include the NTSC signal, PAL signal, SECAM signal and so on, and the wide band signals include HD signal, HDMAC signal, MUSE signal and the like. Input and output signals may include, among others, composite signals, Y, PrPb, R, G, B, YC signals, audio signals, and control signals. The mode judging circuit 6 may be designed to be set by the operator by using a switch. The optical system is not limited to two channels, but the number of channels may be increased as required. The invention is valid not only in the CAV system and CLV system, but also in the MCAV system, MCLV system, and other disk driving systems.

Claims: An optical disc apparatus for reproducing a digital signal recorded on a recording disk (1) in the form of either n channels of first modulated coded compressed digital signals having a bit rate A1 or n x A2/A1 channels of second modulated coded compressed digital signals having a bit rate A2 which is higher than the bit rate A1, where n is an integer of one or more, said apparatus comprising: an optical reproducing means (2,3) having n x A2/A1 reproducing channels for reproducing from said recording disk (1) the recorded n channels of first modulated coded signals through n reproducing channels of said n x A2/A1 reproducing channels to obtain n channels of reproduced first modulated coded signals having the bit rate A1 when signals to be reproduced are said first modulated coded signals and for reproducing the recorded n x A2/A1 channels of second modulated coded signals through said n x A2/A1 reproducing channels to obtain substantially n x A2/A1 channels of reproduced modulated coded signals having the bit rate A2 when the signals to be reproduced are said second modulated coded signals; a reproduced signal processing means (22) operable in a first processing mode for demodulating and decoding said n channels of reproduced first modulated coded signals to obtain a reproduced digital signal and in a second processing mode for demodulating and decoding said substantially n x A2/A1 channels of reproduced second modulated coded signals to obtain another reproduced digital signal; a disk driving means (7) for driving said recording disk (1) to rotate at a specified substantially constant rotating speed or a specified substantially constant linear velocity; and a mode control means (6) for controlling said reproduced signal processing means to operate in said first processing mode when the signals to be reproduced are said first modulated coded signals and in said second processing mode when the signals to be reproduced are said second modulated coded signals. An apparatus according to Claim 1, wherein each of said n x A2/A1 reproducing channels of said optical reproducing means (2,3) includes a semiconductor laser (30) for emitting a laser beam, and a non-linear optical element (32) for generating a second harmonic component from the laser beam, and uses the second harmonic component for reproducing each of the plural channels of modulated coded signs from said recording disk. An apparatus according to Claim 1 or 2, wherein n is one and n x A2/A1 is two. An apparatus according to Claim 3, wherein said recording disk (1) has two recording areas on opposite surfaces thereof, respectively, and wherein two reproducing channels of said optical reproducing means (2,3) are arranged such that one channel of first modulated coded signal is reproduced through one of said two reproducing channels from one of said two recording areas and two channels of second modulated coded signals are reproduced through said two reproducing channels from both of said two recording areas. An apparatus according to Claim 1, further comprising, for recording a digital signal on a recording disk in a recording mode: a recording signal processing means (16,17,19) operable in said first processing mode for compression-coding and modulating an input signal to obtain said n channels of first modulated coded signals having the bit rate A1, and in said second processing mode for compression-coding and modulating the input signal to obtain said substantially n x A2/A1 channels of second modulated coded signals having the bit rate A2; a mode specifying means (18) for controlling said recording signal processing means in said recording mode to operate either in said first processing mode or in said second processing mode; and an optical recording means (20,21) having n x A2/A1 recording channels for recording on said recording disk said n channels of first modulated coded signals through n recording channels of said n x A2/A1 recording channels when said recording signal processing means is operating in said first processing mode and said n x A2/A1 channels of second modulated coded signals through said n x A2/A1 recording channels when said recording signal processing means is operating in said second processing mode. An apparatus according to Claim 5, wherein said optical reproducing means (20,21) is commonly used as said optical recording means (2,3). An apparatus according to Claim 5 or 6, wherein n is one and n x A2/A1 is two. An apparatus according to Claim 7, wherein said recording disk (1) has two recording areas on opposite surfaces thereof, respectively, and wherein two recording channels of said optical recording means (20,21) are arranged such that one channel of first modulated coded signal is recorded through one of said recording channels in one of said two recording areas and two channels of second modulated coded signals are recorded through said two recording channels in both of said two recording areas. An apparatus according to any of Claims 5 to 8, wherein said mode specifying means (18) controls said recording signal processing means to operate in said first processing mode when the input signal is an NTSC, PAL or SECAM signal and in said second processing mode when the input signal is a high definition television signal having a wider frequency band than the NTSC, PAL or SECAM signal. An apparatus according to any of Claims 1 to 9, wherein said mode control means (6) includes a means for detecting from a signal reproduced by said optical reproducing means whether said modulated coded signals are said first modulated coded signals or said second modulated coded signals. An apparatus according to any of Claims 1 to 10, wherein said first modulated coded signal and said second modulated coded signal are the same in kind, and different from each other in compression rate. An optical disc apparatus for reproducing a digital signal recorded on a recording disk (1) in the form of a modulated coded compressed digital signal, said modulated coded signal being one of a first modulated coded signal having a bit rate A1 and a second modulated coded signal having a bit rate A2 which is different from the bit rate A1, said apparatus comprising: an optical reproducing means (2,3) for reproducing said modulated coded signal from said recording disk (1) to obtain a reproduced modulated coded signal; a reproduced signal processing means (22) for demodulating and decoding the reproduced modulated coded signal to obtain a reproduced digital signal; a disk driving means (7) for driving said recording disk, said disk driving means being operable in a first mode in which said disk rotating means drives said recording disk (1) so as to rotate at a specified rotating speed K or a specified linear velocity V and being operable in a second mode in which said disk rotating means drives said recording disk to rotate at substantially a rotating speed K x A2/A1 or a linear velocity V x A2/A1; and a mode control means (6) for controlling said disk driving means (7) to operate in said first mode when said modulated coded signal is said second modulated coded signal. An apparatus according to Claim 12, further comprising, for recording a digital signal on a recording disk in a recording mode: a recording signal processing means (16,17,19) for compression-coding and modulating an input signal to obtain a modulated coded signal, said recording signal processing ;means being operable;able in a first processing mode for compression-coding and modulating the input signal to obtain as said modulated coded signal a first modulated coded signal having the bit rate A1 and in a second processing mode for compression-coding and modulating the input signal having the bit rate A2; a mode specifying means (18) for controlling said recording signal processing means (17,19) and said disk driving means (7) in said recording mode to operate either in said first processing mode and said first mode, respectively, or in said second processing mode and said second mode, respectively; and an optical recording means (20,21) for recording said modulated coded signal on said recording disk. An apparatus according to claim 13, wherein said optical reproducing means (2,3) is commonly used as said optical recording means (20,21). An apparatus according to Claim 13 or 14, wherein said mode specifying means (18) controls said recording signal processing means (17,19) and said disk driving means (7) to operate in said first processing mode and said first mode, respectively, when the input signal is an NTSC, PAL, or SECAM signal and in said second processing mode and said second mode, respectively, when the input signal is a high definition television signal having a wider frequency band than the NTSC, PAL or SECAM signal. An apparatus according to any of Claims 12 to 15, wherein said mode control means (6) includes a means for detecting from a signal reproduced by said optical reproducing means whether said modulated coded signal is said first modulated coded signal or said second modulated coded signal. An apparatus according to any of Claims 12 to 16, wherein said optical reproducing means (2,3) includes a semiconductor laser (30) for emitting a laser beam, and a non-linear optical element (32) for generating a second harmonic component from the laser beam, and uses the second harmonic component for reproducing said modulated coded signal from said recording disk. An apparatus according to any of Claims 12 to 17, wherein said first modulated coded signal and said second modulated coded signal are the same in kind, and different from each other in compression rate.

Inventors: HONJO MASAHIRO, HONJO, MASAHIRO
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1991
Main classification: H04N9
IPC codes: H04N5, G11B20, G11B7, H04N9