JPH0689506A - Device reproducing disk - Google Patents

Abstract

PURPOSE:To improve an access speed eliminating a motor control time to determine the access time by controlling so as to fix the number of revolution of a motor and to change a linear velocity at the time of accessing to a disk recording in a constant linear velocity (CLV). CONSTITUTION:The reproducing signal of an optical disk 1 controlled to the CLV whose subcode data is detected by a digital signal processing circuit 10 and sent to a microcomputer 11. Then, when accessed, by the micro computer 11, the present reproducing position of the optical disk 1 is detected from the subcode, and a required reproducing position is operated, and a pickup control circuit 7 is instructed of access operation. By the microcomputer 11, a control signal is sent to a frequency synthesizer 9, and an oscillation frequency is changed to change the frequency of the basic clock for a CLV motor control circuit 4 and the digital signal processing circuit 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk reproducing apparatus for recording digital signals, and more particularly to a disk reproducing apparatus suitable for improving the access speed of a disk recorded at a constant linear velocity.

[0002]

2. Description of the Related Art There is a compact disc player (CD player) as a music reproducing device. An optical pickup detects a disc recorded by converting an audio signal into digital data. After performing error detection and correction processing on the reproduced digital data, it is converted into an analog signal. This CD player has a high access speed because it is a non-contact type with an optical pickup. Since address information is recorded on the disc, it is easy to find the beginning of the desired song. In addition, the disk is recorded at a constant linear velocity (CLV) for the disk rotation speed in order to increase the recording density.
Even during reproduction, the disk is rotated by CLV control as described in JP-A-59-185071.

C using this CD as a data memory
There is a D-ROM. When reproducing a CD-ROM, it is required that the data memory has a high access speed.
One of the factors that determines the access speed is disk rotation speed control. Since the CLV control is performed, the number of rotations on the inner circumference and the outer circumference of the CD is approximately twice as different. Therefore, in the access from the inner circumference to the outer circumference and from the outer circumference to the inner circumference, there is a problem in the control time until the rotational speed becomes constant. For this problem, it depends on the ability of the motor to rotate the disk and depends on the improvement of the performance of the motor.

To address this, as described in Japanese Patent Application No. 4-50789, a disc recorded by CLV is controlled at a constant number of revolutions (CAV) to improve the access speed during reproduction of the disc. Techniques have been proposed. However, in order to control the motor at a constant rotation speed, it is necessary to provide a rotation speed detection means on the motor, which causes a problem that the configuration of the motor becomes complicated. .

[0005]

The present invention is based on the above CL.
This is to improve the access speed at the time of reproducing a disc recorded with V.

[0006]

According to the present invention, a disc recorded in CLV is kept at a constant linear velocity (CL
V), and when accessing from the inner circumference to the outer circumference or from the outer circumference to the inner circumference, the linear velocity is changed so that the rotational speed is not changed. Means is provided for changing the reference clock frequency that determines the processing time of the reproduced digital signal processing in accordance with the transmission speed of the digital information signal picked up from the disk.

[0007]

When the optical pickup is moved from the inner circumference to the outer circumference or from the outer circumference to the inner circumference, the rotation speed of the motor does not change. Therefore, the motor control time, which is one of the factors that determines the access time, Can be eliminated. Also,
The transmission speed of the digital information signal picked up from the disk changes according to the movement amount of the optical pickup, but by providing a means for changing the reference clock frequency that determines the processing time of the reproduction digital signal processing,
Can handle.

[0008]

FIG. 1 shows an embodiment of the present invention. Reference numeral 1 is an optical disc on which a digital signal is recorded in a CD format at a constant linear velocity, 2 is a motor for rotating the optical disc 1, 4
Is a CLV motor control circuit for controlling the rotation speed of the motor 2 so that the linear velocity is constant, 5 is an optical pickup, 6 is a feeding mechanism of the optical pickup 5, 7 is tracking of the optical pickup 5, focus control, pickup of the feeding mechanism A control circuit, 8 is a preamplifier that amplifies the signal of the optical pickup 5, 9 is a frequency synthesizer that oscillates at an arbitrary specified frequency, and 10 is a reproduction signal and a clock of the frequency synthesizer 9 according to a CD format such as error correction processing. A digital signal processing circuit that performs digital signal processing outputs data and subcode after error correction processing. Reference numeral 11 denotes a microcomputer, which performs an operation of instructing an access operation to the control circuit 7 by subcode data and an access instruction from the outside, and also generates a signal for controlling the oscillation frequency of the frequency synthesizer 9.

The operation of the configuration of FIG. 1 will be described with reference to FIGS. 2 and 3. FIG. 2 shows the relationship between the position of the optical pickup 5 and the rotation speed of the motor. FIG. 3 shows the relationship between the position of the optical pickup 5 and the linear velocity for tracing the optical disk 1 from the point A to the point B of the optical pickup 5, respectively. It shows a case of moving and accessing. In the operation of the configuration shown in FIG. 1, the CLV motor control circuit 4 controls the motor 2 at a constant linear velocity so that the frame synchronization signal frequency indicating the transmission speed of the reproduction signal from the digital signal processing circuit 10 becomes constant.
The optical pickup 5 can trace the track of the optical disc 1 from the inner circumference to the outer circumference by the moving mechanism 6 and the pickup control circuit 7. The preamplifier 8 amplifies the signal from the optical pickup 5, and the pickup control circuit 7
Output a control error signal to the digital signal processing circuit 1
A reproduction signal is output to 0. This reproduced signal is continuously reproduced without access (in FIGS. 2 and 3, a section from the innermost circumference to the point A and a section from the point B to the outermost circumference) to the optical disc 1 Is controlled at a constant linear velocity, and the transmission rate is constant. The digital signal processing circuit 10 detects the subcode data of the reproduced signal and sends it to the microcomputer 11, and outputs the data after the correction processing, which is used as data of a host computer or the like not shown in FIG. Next, the operation at the time of access (when accessing from point A to point B in FIGS. 2 and 3) will be described. Microcomputer 1
1 receives an access command from a host computer (not shown) or the like, detects the current reproduction position of the optical disc 1 from the subcode, calculates the desired reproduction position, and issues an access operation instruction to the pickup control circuit 7. . At the same time, the microcomputer 11 sends a control signal to the frequency synthesizer 9 to change the oscillation frequency,
CLV motor control circuit 4, digital signal processing circuit 10
Change the frequency of the basic clock sent to. less than,
A numerical example of frequency control will be given. In FIG. 2, if the linear velocity is controlled to be constant, the rotational speed will be inversely proportional to the trace position (diameter), so it will be (70/90) during the trace from point A to point B ( (See dashed line). Therefore, if the linear velocity is controlled to be constant, it is necessary to reduce the rotational speed of the motor 2 by C when accessing from the point A to the point B. On the other hand, in the present embodiment, when accessing from the point A to the point B, the oscillation frequency of the frequency synthesizer 9 is multiplied by (90/70). Therefore, the target linear velocity in the CLV motor control circuit is (90/70) times,
The motor 2 rotates at a linear velocity of (90/70) times. (FIG. 3) Therefore, the rotational speeds at points A and B are the same. On the other hand, since the linear velocity is (90/70) times, the transmission rate of the digital information signal picked up from the disc 1 is also (90/70) times. On the other hand, since the basic clock sent to the digital signal processing circuit 10 is also multiplied by (90/70), the signal processing rate is increased and the data can be reproduced correctly according to the transmission speed. The flow chart of the above access operation is shown in FIG.
Shown in. As described above, according to this embodiment, since the rotation speed of the motor 2 does not change at the time of access, there is an effect that the time required for access can be shortened.

Next, another embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the control by the microcomputer 11 is changed in the disc reproducing apparatus shown in FIG. The operation will be described with reference to the flowchart of FIG. The operation of the flow chart of FIG. 5 until the end of pick movement is the same as that of the flow chart of FIG. The operation after the end of pick movement will be described. After the pick movement is completed, the basic C
Gradually lower the K frequency. That is, the target value of the linear velocity is gradually decreased. Therefore, as shown in FIG. 6, the linear velocity of rotation of the disk is once 1.2 × (90
/ 70) m / s, it gradually drops until it reaches 1.2 m / s. According to this embodiment, the motor 2 is used at the time of access.
Since the rotation speed of does not change, the time required for access can be shortened. Further, since the linear velocity only temporarily changes at the time of access, it is easy to make the transmission rate of the data output from the digital signal processing circuit constant.

FIG. 7 shows another embodiment of the present invention. This is an embodiment in which the preamplifier 8 performs waveform equalization so that the transmission characteristics of the optical disk 1 and the optical pickup 5 are such that there is no intersymbol interference. Generally, it is possible to design an optical pickup so that the transmission characteristics of an optical disk satisfy the conditions of the transmission characteristics without intersymbol interference, but waveform equalization is performed in consideration of variations in manufacturing of the disk and the optical pickup. May be done. In FIG. 7, reference numeral 13 denotes an output from the microcomputer 11, which instructs the preamplifier 8 to switch frequency characteristics for waveform equalization depending on the position of the pickup 5, and the other configurations are the same as those in FIG.

The microcomputer 11 uses the subcode data and the access command to pick up the current pickup 5
It is possible to know the location of and the location of the access destination. Therefore, it is possible to switch and control the frequency characteristic of waveform equalization corresponding to the transmission speed of the reproduction signal of the access destination. Since the transmission speed becomes higher toward the outer circumference of the disk, the frequency characteristic of waveform equalization is switched so as to shift to the higher frequency side relatively toward the outer circumference of the disk. In the circuit configuration in which the frequency characteristic is determined by the resistor and the capacitor, the switching of the frequency characteristic in the preamplifier 8 is performed by switching the resistance value and the capacitance value of the capacitor by a switching means such as a transistor. The purpose can also be achieved by using a voltage-controlled variable capacitor or resistor.

FIG. 8 shows an example of the frequency synthesizer 9. Reference numeral 15 is a phase comparator, 24 is a loop filter, 14 is a voltage-controlled oscillator, 17 is a frequency divider with variable frequency division ratio, 18 is a frequency divider, and 16 is a crystal oscillator. From the microcomputer 11, a frequency control signal 23 for setting the frequency division ratio of the frequency divider 17 is input. Since the voltage controlled oscillator 14 is controlled so that the oscillation frequencies of the frequency divider 17 and the frequency divider 18 become equal, changing the frequency division ratio of the frequency divider 17 causes the voltage controlled oscillator 10 to operate at the set frequency. Can be oscillated.

FIG. 9 shows another embodiment of the present invention. This is an example in which the present invention is applied to reproduction of a disc on which an audio PCM signal is recorded. This embodiment has the same configuration as that of FIG. 1 except that a buffer RAM control circuit 19, a buffer RAM 20, a crystal oscillator 21, and a D / A converter 22 are added. The buffer RAM control circuit 19 receives the buffer RA from the basic clock supplied from the frequency synthesizer 9.
A data write timing signal for M20 is generated, and the data output from the digital signal processing circuit 10 is written in the buffer RAM 20. In addition, a timing signal for reading data from the buffer RAM 20 is generated based on a basic clock that is an integral multiple of the sampling frequency, and the data is D / A converter at a constant speed regardless of changes in the transmission speed. 22
Output to. Therefore, it is possible to correctly reproduce the audio signal even if the transmission speed changes each time the access is performed. In addition, the transmission speed of the signal reproduced from the disc is D / A
In a system such as a mini disk, which has a higher transmission speed than the signal output to the converter, a buffer RAM
Since it is necessary to repeat the access to absorb the discrepancy in the transmission rate, the buffer RAM is required regardless of the application of the present invention, and therefore it is particularly preferable. If data is lost due to vibration using the buffer RAM, if shock proof reading of data in the buffer RAM is performed until re-access, the disk is accessed quickly. Therefore, the capacity of the buffer RAM can be reduced. In particular, if the embodiments shown in FIGS. 5 and 6 are used together, the average amount of change in the transmission speed can be reduced, so that the effect of reducing the RAM capacity is great.

[0015]

According to the present invention, the constant linear velocity is changed before and after the access so that the rotational speed does not change when the disk recorded by CLV is accessed. Therefore, the rotational speed of the motor during the access operation is changed. Is constant, and the motor control time, which was one of the factors that determine the access time, can be eliminated. Further, the transmission speed of the digital information signal picked up from the disc changes due to the change of the linear velocity, but this can be dealt with by providing means for simultaneously changing the reference clock frequency that determines the processing time of the reproduction digital signal processing. .

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a diagram showing the rotational speed of the disc of FIG.

3 is a diagram showing the linear velocity of rotation of the disk of FIG.

4 is a flow chart showing the operation of FIG.

5 is a flowchart showing another operation of FIG.

FIG. 6 is a diagram showing the rotation speed of the disc of FIG.

FIG. 7 is a block diagram of a second embodiment of the present invention.

8 is a block diagram of the frequency synthesizer of FIG.

FIG. 9 is a block diagram of a third embodiment of the present invention.

[Explanation of symbols]

1 ... Optical disc, 2 ... Motor, 4 ... CLV motor control circuit, 5 ... Optical pickup, 7 ... Pickup control circuit,
8 ... Preamplifier, 9 ... Frequency synthesizer, 10 ... Digital signal processing circuit, 11 ... Microcomputer,

Claims (3)

[Claims] 1. A disc on which a digital information signal, which has been subjected to digital signal processing in a predetermined recording format such as an error correction code, is spirally recorded from the inner circumference to the outer circumference or from the outer circumference to the inner circumference at a constant linear velocity. A means for rotating at a constant speed, a means for switching the value of the linear velocity so that the rotation speed of the disk does not change before and after access when accessing from the inner circumference to the outer circumference or from the outer circumference to the inner circumference, and a digital information signal from the disk. And a digital signal processing means for subjecting the digital information signal output from the reading means to reproduction digital signal processing corresponding to the recording format. 2. The disk reproducing apparatus according to claim 1, wherein the reading means has means for switching frequency characteristics in response to changes in the transmission speed of the reproduced digital information signal. 3. The digital signal processing means according to claim 1, which has a means for changing a reference clock frequency for performing digital signal processing in proportion to a change in linear velocity when the linear velocity is switched. .