JPH05189889A - Digital disc reproducing system - Google Patents

Abstract

PURPOSE:To shorten access time in reproduction of CD-ROM. CONSTITUTION:A disc 1 recorded with data in constant line velocity (CLV) format is rotated at a constant speed. Data is then read out from the disc 1 by means of an optical pickup 5. Edge signal of thus read out data is inputted to a VFO. Central frequency is then switched by switching the time constant of a VCO 15 included in the VFO. The central frequency is switched based on the position of the pickup 5. Furthermore, data transfer rate is kept constant using a memory 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital disk reproducing apparatus for reproducing data from a CLV (constant linear velocity) type disk such as a CD-ROM reproducing apparatus.

[0002]

2. Description of the Related Art An optical disc generally called a CD-ROM has a digital signal (data) which is similar to an audio CD (compact disc) and has an EFM (Eigher).
t toFourteen Modulation) is recorded by a modulation method called. Further, in the CD-ROM, the time width of the unit bit and the unit frame is the same on the inner circumference and the outer circumference of the disc. Therefore, the rotation speed of the disk is changed according to the change in the position of the optical pickup in the disk radial direction. That is, the disk is scanned by the optical pickup at a constant linear velocity (CLV).

[0003]

DISCLOSURE OF THE INVENTION In a CD-ROM player or a CD player, when searching an arbitrary address on the disc and reproducing it, the rotation speed of the disc corresponds to the position of the optical pickup in the disc radial direction. You have to control the speed. Since the time required to shift the disk drive motor from one rotation speed state to another rotation speed state is relatively long, the access time is inevitably long. Further, the circuit (CLV control circuit) for changing the rotation speed of the disk drive motor according to the position of the pickup in the disk radial direction is complicated, and the cost is inevitably increased.

Therefore, an object of the present invention is to provide a digital disc reproducing apparatus capable of shortening the access time when a CLV type disc is used.

[0005]

The first invention of the present application for achieving the above object is to reproduce the digital signal from a recording medium disk in which the digital signal is recorded in a constant linear velocity format together with clock information. And a disc rotating device for rotating the disc at a substantially constant speed, a pickup for reading a digital signal with the clock information from the disc, and an output of the pickup. A variable frequency oscillator connected to the pickup for generating a clock signal based on the above, and reproduction data connected to the pickup and the variable frequency oscillator and corresponding to a reproduction signal obtained from the pickup. And a reproduction signal processing circuit configured as described above and the pickup. A feed device for moving the pickup in the radial direction, a pickup position signal generating means for generating a signal indicating the radial position of the disc of the pickup, and a response to the pickup position signal generated by the pickup position signal generating means. And a control means for changing the oscillation frequency range of the variable frequency oscillator.

A second invention of the present application is a digital disk reproducing apparatus for reproducing the digital signal from a recording medium disk in which a digital signal is recorded in a constant linear velocity format along with clock information. A disk rotating device for rotating the disk at a substantially constant speed, a pickup for reading a digital signal with the clock information from the disk, and a clock signal based on the clock information included in the output of the pickup. A clock signal generation circuit for generating, a feeding device for moving the pickup in the radial direction of the disc, a read clock signal generation circuit for generating a read clock signal of a constant frequency, and a read clock signal connected to the pickup and from the pickup. Playback data corresponding to the obtained playback signal And a reproduction signal processing circuit configured to form a circuit between the pickup and the reproduction signal processing circuit or after the reproduction signal processing circuit and coupled to the clock signal generation circuit and the read clock signal generation circuit. The read clock generated from the read clock signal generation circuit is written with the reproduced signal obtained from the pickup or the reproduced data obtained from the reproduced signal processing circuit based on the clock signal generated from the clock signal generation circuit. The present invention relates to a digital disk reproducing device including a memory device for reading the reproduction signal or reproduction data corresponding to the reproduction signal at a constant transfer rate based on the signal.

[0007]

In the present invention, the disc is rotated at a substantially constant speed regardless of the change in the position of the pickup. As a result, the transfer rate of data obtained from the pickup changes depending on the position of the pickup in the radial direction of the disk. The variable frequency oscillator (VFO) in the first aspect of the invention generates a clock signal having a frequency corresponding to the transfer rate of the digital signal obtained from the pickup. A reproduction signal processing circuit such as an EFM demodulation circuit reproduces a reproduction output (reproduction data) corresponding to the output of the pickup based on this clock signal.
To form. The pickup position signal generating means is composed of an address detection circuit or a dedicated position detector. When the address signal is recorded on the disc, this detection signal can be the pickup position signal. An address signal externally applied for seeking can also be a pickup position signal. The control means for changing the oscillation frequency range of the variable frequency oscillator switches, for example, the center frequency of the variable frequency oscillator in response to the pickup position signal. As a result, the output frequency range of the variable frequency oscillator can be expanded.

In the second aspect of the invention, the writing of data to the memory device is performed at the same transfer rate as the output of the pickup, and the reading is performed by a clock signal having a constant frequency. Therefore, the transfer rate of the output data of the memory device becomes constant, and the output data can be supplied to the general-purpose device.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a CD-ROM reproducing apparatus according to an embodiment of the present invention will be described with reference to FIGS.

The disk 1 shown in FIG. 1 is called a CD-ROM in which a digital signal is recorded by EFM method with clock information or synchronization information, and has a spiral track 2 as shown in principle in FIG. The unit bit of the digital signal on the track 2 and the recording length L of the unit frame are the same in the entire area of the track 2. That is, CD-R
Like the audio CD, the OM disc 1 is constructed so that data is always transferred at a constant speed by reproducing in the CLV system. Since the bit lengths are the same, the EFM digital signal contains clock information.

A motor 3 as a rotating device for the disk 1 is rotated at a constant speed by a drive circuit 4. That is, although the motor 3 is the CLV type disk 1, as shown in FIG. 3, the disk 1 is CAV-driven so that the rotation speed becomes constant irrespective of the radial position of the pickup. Although not shown, a speed detector for the motor 3 may be provided, and a speed control circuit for rotating the motor 3 at a constant speed based on the detected output may be provided.

Like the CD player, the optical pickup 5 is a device for projecting a laser beam onto the disc 1 and detecting the reflected light to read a recorded digital signal (data) from the disc 1. The optical pickup 5 is a well-known laser light source and objective. It has a lens, a light receiving element (optical sensor), and the like, and converts a light reading signal into an electric signal and outputs it.

The feeding device 6 uses the pickup 5 for the disc 1
Of the feed motor and rotation-
It consists of a linear conversion mechanism.

The output terminal of the pickup 5 is a preamplifier 7
Also, it is connected to the EFM demodulation circuit 10 and the clock generation circuit 11 as the reproduction signal processing circuit via the waveform shaping circuit 8. The waveform shaping circuit 8 includes a comparator and shapes the EFM digital signal read from the disk 1 into a square wave pulse.

The clock signal generation circuit 11 includes an edge detection circuit 12, a phase comparator 13, and a low pass filter 14.
And a VCO (voltage controlled oscillator) 15 is a variable frequency oscillator (VFO). The waveform shaping circuit 8 outputs a square wave corresponding to a digital signal containing clock information. The edge detection circuit 12 connected here generates a short time width (shorter than the time length of a unit bit) pulse indicating the edge of a square wave. The edge detection circuit 12 may be composed of a trigger differentiating circuit and a mono-multivibrator. Phase comparator 13, low-pass filter 14 and VCO1
5 constitutes a PLL circuit 16 and includes a phase comparator 13
One input terminal is connected to the edge detection circuit 12, the other input terminal is connected to the VCO, and the output terminal is connected to the control input terminal 17 of the VCO 15 via the low pass filter 14. The VCO 15 is constructed so that the center frequency can be switched. A clock signal (synchronization signal) corresponding to the clock information reproduced from the disc 1 is output from the VCO 15. The frequency of this clock signal changes with time. A specific example of this will be described later with reference to FIG.

The output line 18 of the clock generation circuit 11 is connected to the demodulation circuit 10 and the write clock input terminal W of the memory 19. The demodulation circuit 10 is well known in CD players and the like, and extracts a reproduced digital signal (main information) from the output of the waveform shaping circuit 8 based on the clock signal of the frequency that changes with time obtained from the clock generation circuit 11. , EFM format playback digital signals are converted to NRZ (Non Return to Zer
Convert to a digital signal of a general format such as o).

The memory 19 comprising a RAM connected to the demodulation circuit 10 is for correcting the data having different transfer rates obtained from the demodulation circuit 10 to a constant transfer rate and outputting the read data. The input terminal R is connected to a read clock signal generator 20 which generates a read clock signal having a constant frequency. It is also possible to arrange this memory 19 in the preceding stage of the demodulation circuit 10. In this case, a reproduced digital signal (data) having a constant data transfer rate is sent to the demodulation circuit 10.

A microcomputer 22 connected to the output line 21 of the memory 19 has an address detecting function. That is, a digital signal is recorded on the disk 1 with an address signal added for each frame. This address signal is read by the pickup 5 together with the main information data. The microcomputer 22 compares this address signal with the seek command signal given from the line 23, and gives a seek control signal for moving the pickup 5 to the seek address to the feeding device 6 via the line 24.
Further, the microcomputer 22 sends a signal indicating whether the pickup 5 is located in the inner peripheral area, the intermediate area or the outer peripheral area of the disc on the basis of the detected address signal or the target address signal for which the seek command is given, on lines 25, 26, It is output to 27 and given to the VCO 15. The microcomputer 22 is also used to control the demodulation circuit 10.

Note that FIG. 1 shows the principal part of the CD-ROM reproducing device in principle, and more circuits are added to the actual device. For example, a device that controls the objective lens included in the pickup 5 to perform focus servo of the light beam, a tracking control device that controls the position of the beam in the disk radial direction by a reflection mirror arranged in the beam path in the pickup 5, and the like. It is provided.

FIG. 4 shows an example of the VCO 15 of FIG. The VCO 15 is an astable multivibrator type, and has a pair of transistors Q1 and Q2 and a pair of diodes D1.
, D2, a pair of resistors R1, R2, three capacitors C1, C2, C3, and a capacitor switching switch S1.
, S2, S3 and a controlled current source 30. The control terminal 17 is connected to the low pass filter 14 of FIG. 1, and the levels of the currents I1 and I2 sent by the control current source 30 are changed by the change of the voltage level of the control signal applied thereto,
As a result, the frequency of the oscillation output obtained from the output terminal 31 changes. A bias power supply terminal 32 is connected to the control current source 30, and the collectors of the pair of transistors Q1 and Q2 are connected to the power supply terminal 33 via resistors R1 and R2. The base of one transistor Q1 is connected to the collector of the other transistor Q2, and the base of the other transistor Q2 is connected to the collector of one transistor Q1. Also, a pair of transistors Q
Capacitors C1 to C3 are selectively connected between the emitters of 1 and Q2 by switches S1 to S3. The switches S1 to S3 are controlled by the output lines 25, 26 and 27 of the microcomputer 22 shown in FIG. Capacitor C1
, C2, and C3 have different electrostatic capacities, and this switching makes it possible to change the center frequency of the VCO 15, that is, the oscillation frequency range.

FIG. 5 shows changes in the cycle of the clock signal output from the clock signal generation circuit 16. The disk inner circumference has a long cycle and the outer circumference has a short cycle.

[0022]

[Operation] The signal recorded on the disk 1 is track 2
When continuously reproducing from the start end of the track toward the end, the pickup 5 is positioned at the start end of the innermost track of the track 2,
The motor 3 rotates the disk 1 at a constant speed to start reading a signal. The light beam is controlled by a tracking control device (not shown) so that the light beam scans the spiral track 2, and the displacement amount of the light beam becomes a certain amount or more by this, and it becomes impossible to perform the tracking control. The light beam is sent in the radial direction of the disk 1 by the cod-feeding device 6.
Even if the light beam moves in the radial direction of the disk 1, the rotation speed of the disk 1 is kept constant. As a result, the time width of the unit bit and the time width of the unit frame of the reproduction signal change according to the change of the position of the light beam in the radial direction of the disk 1, and the data transfer rate also changes. Even if the data transfer rate changes, a clock signal corresponding to this is generated from the clock signal generation circuit 11, so the demodulation circuit 10 is based on this.
In, EFM data can be converted into, for example, NRZ format data.

In order to expand the output frequency range of the VCO 15, a signal indicating whether the pickup 5 is located in the inner peripheral area, the intermediate area, or the outer peripheral area of the disc 1 is output by the output line 25 of the microcomputer 22. , 26, 27. As a result, the switches S1 and S2 shown in FIG.
, S3 are selectively turned on to selectively connect capacitors C1, C2, C3 having different capacities to switch the center frequency of the VCO 15. In this example, the center frequency of the VCO 15 is switched in three stages, but it may be in two stages, four stages or more, or the time constant may be changed continuously.

Since the transfer rate of the data obtained from the demodulation circuit 10 changes every moment, the memory 19 keeps the transfer rate of the data constant. This makes it possible to connect a general-purpose digital device to the CD-ROM reproducing device.

At the time of seek, the microcomputer 22 controls the feeding device 6 so that the light beam is positioned at the target address.
At the same time, the target address of the microcomputer 22 is the disk 1
It is determined which one of the inner peripheral area, the intermediate area, and the outer peripheral area it belongs to, and the switch-on command signal is transmitted to any of the lines 25 to 27 corresponding to the belonging area. This allows
Any one of the switches S1 to S3 is turned on, and VC
The center frequency of O15 is switched to match the target address. Since the switching time of the switches S1 to S3 is extremely short, the reading of the signal of the target address can be started quickly. That is, in the case of the conventional CVL method, since it was necessary to control the rotation speed of the motor 3 so as to match the target address, the access time was inevitably lengthened, but in the present embodiment, only switching of the switch is required. The access time will be greatly shortened.

[0026]

MODIFICATION The present invention is not limited to the above-described embodiments, and the following modifications are possible, for example. (1) Instead of controlling the VCO 15 by knowing the target address to be sought or the address currently being reproduced in the microcomputer 22, the change in the position of the disk radial moving member of the pickup 5 or the feeding device 6 is changed to the inner circumference of the disk 1. A position sensor for detecting in three or more stages of a region, an intermediate region and an outer peripheral region, or a position sensor for continuously detecting a position by a potentiometer is provided,
The VCO 15 may be controlled based on this output to expand the output frequency range of the VCO 15. (2) In the embodiment, the rotation speed of the disk 1 is set to be constant at every position of the pickup 5, but it may be switched in two steps of the inner circumference side and the outer circumference side or in more steps.
Even in this case, if the address change at the seek time is within the same area, the access time becomes short. (3) The VCO 15 can be a Schmitt trigger type VCO. (4) The center frequency of the VCO 15 can be switched by switching the resistance value. (5) The center frequency of the VCO 15 may be continuously changed by a continuously controllable circuit such as a variable capacitance diode or a variable resistance element. (6) It is also applicable to a magnetic disk reproducing device. (7) NRZ (Non Retur) data other than EFM
m to Zero) method, MFM (Modified Frequency Modu
It is possible to record by the method (lation) etc. Also, the clock signal can be recorded separately from the data.

[0027]

According to the first and second aspects of the present invention, the access time can be shortened and the disk rotating device can be simplified. According to the invention of claim 1, the clock signal can be generated over a wide frequency range. According to the invention of claim 2, the reproduction data can be output at a transfer rate having high versatility.

[Brief description of drawings]

FIG. 1 is a block diagram showing a CD-ROM reproducing device according to an embodiment of the present invention.

FIG. 2 is a plan view illustratively showing a track form in the disc of FIG.

FIG. 3 is a diagram showing a relationship between a position of a pickup and a rotation speed of a disc.

FIG. 4 is a circuit diagram showing a VCO.

FIG. 5 is a waveform diagram showing an output pulse of a VCO.

[Explanation of symbols]

 1 Disk 3 Motor 5 Pickup 6 Feeder 10 Demodulation Circuit 11 Clock Signal Generation Circuit

Claims (2)

[Claims] 1. A digital disk reproducing apparatus for reproducing the digital signal from a recording medium disk in which a digital signal is recorded in a constant linear velocity format with clock information, the disk rotating at a substantially constant speed. A disc rotating device for reading, a pickup for reading a digital signal with the clock information from the disc, and a variable frequency oscillator connected to the pickup for generating a clock signal based on the output of the pickup. A reproduction signal processing circuit connected to the pickup and the variable frequency oscillator and configured to form reproduction data corresponding to a reproduction signal obtained from the pickup; and the pickup in the radial direction of the disc. A feeder for moving the pickup, and the pickup Pickup position signal generating means for generating a signal indicating the radial position of the disk, and control means for changing the oscillation frequency range of the variable frequency oscillator in response to the pickup position signal generated by the pickup position signal generating means. A digital disc reproducing device consisting of. 2. A digital disk reproducing apparatus for reproducing the digital signal from a recording medium disk in which a digital signal is recorded in a constant linear velocity format with clock information, the disk rotating at a substantially constant speed. A disc rotating device for reading, a pickup for reading a digital signal with the clock information from the disc, and a clock signal generation circuit for generating a clock signal based on clock information included in the output of the pickup. A feed device for moving the pickup in the radial direction of the disc, a read clock signal generating circuit for generating a read clock signal of a constant frequency, and a reproduction signal connected to the pickup and obtained from the pickup To form playback data for A reproduced signal processing circuit formed between the pickup and the reproduced signal processing circuit or after the reproduced signal processing circuit and coupled to the clock signal generation circuit and the read clock signal generation circuit, The reproduction signal obtained from the pickup or the reproduction data obtained from the reproduction signal processing circuit is written based on the clock signal generated from the generation circuit, and is constant based on the read clock signal generated from the read clock signal generation circuit. And a memory device for reading the reproduction signal or reproduction data corresponding thereto at the transfer speed of.