JP2950542B2 - Device for switching characteristics of disc playback system - Google Patents

Description

Description: [Object of the invention] (Industrial application field) The present invention relates to a disk playback system capable of switching the playback speed, and in particular, to a characteristic switching device for switching the characteristics of each part according to the playback speed. About. (Prior Art) As is well known, for example, in a disk reproducing system such as a compact disk player, the recording time of the reproduced analog audio signal is considered in consideration of recording the analog audio signal on another recording medium such as a tape. In order to shorten the time, a function has been added that has a function of performing reproduction at twice the standard speed. However, this type of disc reproducing system is still under development, and an optimum reproducing operation can be performed when reproducing at a standard speed and when reproducing at twice the standard speed. As described above, there is much room for improvement in terms of configuration and performance. (Problems to be Solved by the Invention) As described above, it is said that the conventional disk reproducing system having the function of reproducing at twice the speed of the standard cannot sufficiently meet the needs of the user. Have a problem. Therefore, the present invention has been made in view of the above circumstances, and it is extremely good that an accurate reproduction signal can be obtained in both the reproduction at the standard speed and the reproduction at a speed higher than the standard. It is an object of the present invention to provide a characteristic switching device for a compact disk reproducing system. [Structure of the Invention] (Means for Solving the Problems) In other words, a characteristic switching device of a disk reproducing system according to the present invention includes a disk motor for driving an optical disk on which digital information is recorded and a disk motor for rotating the optical disk. An optical pickup for reading digital information from a driven optical disk, and capable of switching the reproduction speed by switching the rotation speed of the optical disk. A first amplifying circuit having a first amplifying circuit for amplifying an output signal of the optical pickup; and a first feedback circuit for determining a characteristic of the first amplifying circuit; Generating means for generating a bit synchronization clock for extracting data based on the output signal of the optical pickup; generating a disk motor control signal for controlling a rotation speed of the disk motor based on an output signal of the optical pickup; Disk motor control means for supplying a disk motor via a second amplification means having an amplification circuit and a second feedback circuit for determining its characteristics; and an optical pickup based on an output signal of the optical pickup Generating a tracking error signal for the objective lens in the third, and having a third amplifier circuit and a third feedback circuit for determining the characteristic thereof; A tracking servo means for returning to the optical pickup via the width means; a focus error signal for an objective lens in the optical pickup based on an output signal of the optical pickup; and an amplification circuit shown in FIG. A focus servo means for feeding back to the optical pickup via a fourth amplifying means having a fourth feedback circuit for determining the characteristic; and a first to fourth feedback circuits in conjunction with switching of the reproduction speed. And switching means for controlling the characteristics of the first to fourth amplifying circuits and controlling the generation circuit to switch the frequency of the bit synchronization clock. (Operation) According to the above configuration, the characteristics of the amplifying unit, the bit synchronization clock generating unit, the disk motor control unit, the tracking servo unit, the focus servo unit, and the like of the disk playback system move by the switching of the playback speed. Since the switching is performed, an accurate reproduction signal can be obtained both at the time of reproduction at the standard speed and at the time of reproduction at a speed higher than the standard speed. Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 3 shows an overall configuration of a compact disc player to which the present invention is applied and whose reproduction speed can be switched. That is, in the figure, reference numeral 11 denotes a disk reproducing mechanism, which includes a disk table 14 on which the disk 12 is mounted and which is rotationally driven by the action of the disk motor 13,
The optical pickup 15 is configured to read digital data recorded on the optical disk 12, and a pickup feed motor 16 for moving the optical pickup 15 in the radial direction of the disk 12. Then, the reproduction RF output from the optical pickup 15
The signal is amplified by an analog amplification circuit 21 including current-voltage conversion amplification circuits 17 and 18, a wideband RF amplification circuit 19 and a feedback circuit 20 that determines the characteristics of the wideband RF amplification circuit 19, and then the signal is transmitted to a servo control circuit 22. Supplied. This servo control circuit 22 receives the input reproduction RF signal.
The signal is level-sliced at a predetermined slice level, converted into digital data, and a disk motor control signal and a pickup feed motor control signal are generated based on the digital data. Among them, the disk motor control signal is supplied to the disk motor 13 via a drive circuit 25 including an amplifier circuit 23 and a feedback circuit 24, and the rotation speed thereof is controlled. Further, the pickup feed motor control signal is supplied to the pickup feed motor 16 via the drive circuit 26 so that the moving speed of the optical pickup 15 is controlled. Note that a tracking error signal and a focus error signal are generated in the analog amplifier circuit 21. Of these, the tracking error signal is supplied to the optical pickup 15 via a drive circuit 29 including an amplifier circuit 27 and a feedback circuit 28, and tracking servo for an objective lens (not shown) is performed. Further, the focus error signal is supplied to the optical pickup 15 via a drive circuit 32 including an amplifier circuit 30 and a feedback circuit 31, and focus servo for the objective lens is performed. Here, the servo control circuit 22 generates a phase locked loop (PLL) 3 based on the generated digital data.
Drive 3 to generate a bit synchronization clock. Then, the servo control circuit 22 generates a data sampling clock based on the bit synchronization clock, and outputs the data sampling clock to the digital signal processing circuit along with the digital data. This digital signal processing circuit 34 uses a RAM (Read Only Memory) 37 to absorb jitter components for digital data and correct errors in synchronization with a system clock output from a clock generation circuit 36 having a crystal oscillator 35. , Correction processing. The digital data output from the digital signal processing circuit 34 is D / A
(Digital / Analog) The conversion circuit 38 converts the signals into analog signals of the L and R channels, and supplies the signals to amplifiers 39 and 40 and output terminals 41 and 42 to a sound reproduction system (not shown). Here, a reproduction speed control circuit 43 is provided in the compact disc player. When it is required to play back the disk 12 at twice the standard playback speed, the playback speed control circuit 43 supplies a system clock having a frequency twice the standard frequency to the crystal oscillator 35 and the phase locked loop circuit 33. And control to generate a bit synchronization clock, and the characteristics of the wideband RF amplifier circuit 19 and the drive circuits 25, 29, 32 to the feedback circuits 20, 24, 28, 31 at twice the standard speed. The switching operation is performed so as to be optimal for the reproduction of. The reproduction speed control circuit 43 also has an operation of displaying the operation state, time, and the like of the compact disk player by the display circuit 44. Here, the system clock output from the clock generation circuit 36 is a digital signal processing circuit 34 and a synchronization control circuit.
It is supplied to a cassette tape recorder 46 via 45. In this cassette tape recorder 46, the tape running speed during recording and reproduction changes in synchronization with the system clock.
That is, the recording / reproducing speed changes. For this reason, when the disk 12 is being played back at the standard speed, the system clock is also at the standard frequency, so if the cassette tape recorder 46 is in the recording state, the recording speed will also be the standard, and the output terminals 41 and 42 The output audio signal is recorded on the tape at a standard speed.
When the disk 12 is being played back at twice the standard speed, the system clock also has twice the standard frequency. Therefore, if the cassette tape recorder 46 is in the recording state, the recording speed is twice that of the standard. Thus, the audio signals output from the output terminals 41 and 42 are recorded on the tape at twice the standard speed. FIG. 1 shows details of the analog amplification circuit 21. That is, in the drawing, reference numeral 47 denotes a photodetector provided in the optical pickup 15 and four light receiving areas A to D
Are configured in a four-division manner. And the light receiving area
Each output current from A and C is added to a current and supplied to a current-voltage conversion amplifier circuit 17, and each output current from the light receiving regions B and D is added to a current-voltage conversion amplifier circuit 18
Is supplied to Here, the output of each current-voltage conversion amplifier circuit 17, 18 is
After being added via the resistors R1 and R2, the wideband RF amplifier 19
To the negative input terminal of The positive input terminal + of the broadband RF amplifier circuit 19 is grounded, and the output terminal is an output terminal 48.
Is connected to the servo control circuit 22 via the. Further, a feedback circuit 20 including resistors R3 to R5, capacitors C1 and C2, and a transistor Q is interposed between the negative input terminal − and the output terminal of the broadband RF amplifier circuit 19. The base of the transistor Q is connected to the connection terminal 49. The connection terminal 49 is connected to the reproduction speed control circuit 43.
Thus, a signal is supplied at H level when the disk 12 is reproduced at the standard speed, and at L level when the disk 12 is reproduced at twice the standard speed. For this reason, when the disk 12 is being played back at the standard speed, the H level signal is supplied to the connection terminal 49, and the transistor Q is turned on. Is determined by the feedback circuit 20 including the resistors R3 to R5 and the capacitors C1 and C2. That is, the frequency characteristics of the wideband RF amplifier circuit 19 at the time of the standard speed reproduction are the same as those of the conventional compact disc player only for the standard speed reproduction, and as shown in FIG. The characteristic is set so that the characteristic is attenuated as the frequency becomes higher, that is, the characteristic is optimal for the frequency of the reproduced RF signal reproduced at the standard speed. On the other hand, in the state where the disk 12 is being played back at twice the normal speed, the transistor Q is in the off state since the L level signal is supplied to the connection terminal 49.
The frequency characteristic of the broadband RF amplifier circuit 19 is determined by the feedback circuit 20 including the resistors R3 to R5 and the capacitor C1. In this case, the frequency characteristic of the broadband RF amplifier 19 is
As shown in Fig. B, it is almost flat and 1400kHz which is twice 700kHz
The characteristic is set so as to be raised near z, and to be attenuated as the frequency becomes higher thereafter, that is, to be optimal for the frequency of the reproduced RF signal reproduced at twice the standard speed. Therefore, according to the configuration as in the above embodiment, the frequency characteristic of the wideband RF amplifier 19 for amplifying the reproduced RF signal is optimized so as to be optimal for the obtained reproduced RF signal according to the reproduction speed of the disk 12. Is switched, so that an accurate reproduction signal can be obtained both at the time of reproduction at the standard speed and at the time of reproduction at twice the standard speed. In this regard, the frequency characteristics of the broadband RF amplifier circuit 19
As shown in FIG. 2A, if the disc 12 is reproduced at a speed twice as high as the standard speed, the phase characteristic does not match the reproduced RF signal when the disc 12 is reproduced at the standard speed, so that the jitter increases. This causes a problem that the amount of error correction greatly increases, and a problem that a good reproduction signal cannot be obtained occurs. In addition, the frequency characteristic of the broadband RF
As shown in Fig. B, if the characteristic corresponding to the reproduction at twice the standard speed is fixed, a good reproduction signal cannot be obtained because the characteristic near 700 kHz becomes flat at the standard speed reproduction. Therefore, it is necessary to change the frequency characteristics of the wideband RF amplifier circuit 19 at the time of standard speed reproduction and at the time of double speed reproduction. Here, the optical pickup 15 is an ideal type in which the response to the frequency of the reproduced RF signal at the time of reproduction at twice the standard speed is the same as the response to the frequency of the reproduced RF signal at the time of standard speed reproduction. Therefore, the constant of the feedback circuit 20 can be set so as to have a frequency characteristic that corrects the deviation during reproduction at twice the standard speed. It should be noted that the present invention is not limited to the above-described embodiment, and can be implemented with various modifications without departing from the scope of the invention. [Effects of the Invention] Therefore, as described in detail above, according to the present invention,
It is possible to provide a very good characteristic switching device of a disk reproducing system which can obtain an accurate reproduction signal both at the time of reproduction at the standard speed and at the time of reproduction at a speed higher than the standard speed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block circuit configuration diagram showing an embodiment of a characteristic switching device of a disk reproducing system according to the present invention, FIG. 2 is a characteristic diagram showing frequency characteristics of the embodiment, FIG. FIG. 1 is a block diagram showing the overall configuration of a compact disc player to which the present invention is applied. 11: Disc playback mechanism, 12: Disc, 13: Disc motor, 14: Disc table, 15: Optical pickup, 16: Pick-up feed motor, 17, 18
…… Current-voltage conversion amplifier circuit, 19 …… Broadband RF amplifier circuit, 20 …… Feedback circuit, 21 …… Analog amplifier circuit, 22 ……
Servo control circuit, 23 amplifying circuit, 24 feedback circuit, 25, 26 driving circuit, 27 amplifying circuit, 28 feedback circuit, 29 driving circuit, 30 amplifying circuit, 31 feedback Circuit, 32 ... Drive circuit, 33 ... Phase locked loop circuit, 34 ...
... Digital signal processing circuit, 35 ... Crystal oscillator, 36 ... Clock generation circuit, 37 ... RAM, 38 ... D / A conversion circuit, 39,4
0: amplifying circuit, 41, 42: output terminal, 43: reproduction speed control circuit, 44: display circuit, 45: synchronous control circuit, 46:
Cassette tape recorder, 47 Photo detector, 48
…… Output terminal, 49 …… Connection terminal.

Claims (1)

(57) [Claims] A disk motor for rotating and driving an optical disk on which digital information is recorded; and an optical pickup for reading digital information from the optical disk rotated and driven by the disk motor. A switchable disc reproducing system, comprising: a first amplifying circuit for amplifying an output signal of the optical pickup; and a first amplifying unit having a first feedback circuit for determining characteristics of the first amplifying circuit; Generating means for generating a bit synchronization clock for extracting data based on an output signal of the first amplifying means; and a disk motor for controlling a rotation speed of the disk motor based on an output signal of the optical pickup. Generate a control signal to determine the second amplifier circuit and its characteristics A disk motor control unit for supplying the disk motor via a second amplifying unit having a second feedback circuit; and a tracking for an objective lens in the optical pickup based on an output signal of the optical pickup. An error signal is generated, via a third amplifying means having a third amplifying circuit and a third feedback circuit for determining its characteristics,
A tracking servo unit that returns to the optical pickup; a focus error signal for an objective lens in the optical pickup based on an output signal of the optical pickup; and a fourth amplifier circuit and characteristics thereof are determined. A focus servo means for returning to the optical pickup via a fourth amplifying means having a fourth feedback circuit; and controlling the first to fourth feedback circuits in conjunction with the switching of the reproduction speed. Control means for switching the characteristics of the first to fourth amplifying circuits and controlling the frequency of the bit synchronization clock by controlling the generation circuit. apparatus.