JPS6232544B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a constant linear velocity control device for disc-shaped information recording media such as video discs and audio discs.

For example, if an audio signal is converted into a PCM signal and then recorded and reproduced, the S/N ratio becomes extremely good and the dynamic range becomes wide, so that good recording and reproduction can be performed. Conventionally, a video tape recorder was used as a recording/playback device for such PCM signals, but improvements in ease of handling, simplification of device configuration,
From the viewpoint of ease of duplication, it has been proposed to use a disk-shaped information recording medium, such as a disk-shaped disk (hereinafter simply referred to as disk). The audio signal converted into a PCM signal is recorded on such a disk in the form of a spiral track. In this case, it is necessary to equalize the recording density on the inner circumferential side and the outer circumferential side of the disk to increase the recording density per unit area. Therefore, when reading PCM signals recorded at equal recording densities from a disk, it is necessary to drive the disk at a constant linear speed relative to the pickup for reading information.

Therefore, a conventional constant linear speed control device for driving a disk at a constant linear speed with respect to a pickup has been constructed as shown in FIG. 1, for example.

That is, a spinning motor 1 rotates a disk 2 and a frequency generator 3, a pickup 4 is provided opposite the disk 2, and the pickup 4 is rotated by a spinning motor 1.
is configured to be moved in the radial direction of the disk 2 by a feeding mechanism, and the position of the pick-up 4 in the disk radial direction is detected by a potentiometer 5. Obtain a voltage V _R that is proportional to the distance. On the other hand, the output of the frequency generator 3 is input to a frequency-voltage conversion circuit 7 to obtain a voltage V _F that is inversely proportional to the rotation speed of the spinning motor 1, and a comparison circuit 6 compares the voltage _VR and the voltage V _F. This comparison output was amplified by an amplifier 8, and the rotation speed of the spinning motor 1 was controlled by the amplified comparison output.

Therefore, when using the conventional constant linear velocity control device as shown in _{FIG .} The number is inversely proportional to the distance from the center of rotation of the disk 2 to the pickup 4, and is controlled so that the linear velocity of the disk 2 with respect to the pickup 4 is equal.

However, when using the above-described conventional constant linear velocity control device, a potentiometer or the like is required to detect the position of the pickup in the radial direction of the disk.
It was expensive and had the disadvantage of poor position detection accuracy. Further, after detecting the position R of the pickup in the disk radial direction, in order to obtain a comparison voltage proportional to 1/R, a reciprocal circuit, such as a multiplier, is required, resulting in a complicated circuit.
Another drawback is that the rotational speed of the spinning motor and the position of the pickup in the radial direction of the disk must be detected separately to calculate the linear velocity.

The present invention has been made in view of the above-mentioned drawbacks, and provides a uniform linear velocity control device for a disc-shaped information recording medium that is simple in construction and that always controls the linear velocity of the disc relative to the pickup to be the same. The purpose is to

The present invention will be explained below using examples.

FIG. 2 is an explanatory diagram of one embodiment of the present invention.

A turntable 11 and a slit disk 12 are installed at both ends of the rotor rotating shaft of the spinning motor 1.
The disc 2 and the slit disc 12 mounted on a turntable 11 are fixed separately, and the spinning motor 1 rotates the disc 2 and the slit disc 12 at the same rotation speed.

The radius of the slit disk 12 is set to be slightly larger than approximately 1/2 of the radius of the disk 2.
Long slits 12' are provided facing each other across the center of rotation of the slit disk 12.

On the other hand, a pick-up base 14 is slidably fitted between the cross roller guide members 13 provided oppositely, and one end of the pick-up base 14 is connected to the L
It is bent into a letter shape, and there is a pick-up 1 on the L-shaped part.
5 faces the lower surface of the disk 2 and is fixed to the disk 2 so as to read the information recorded on the disk 2. A pick-up base drive rack 16 is fixed to the pick-up base 14, and the pick-up base drive rack 16 is driven by a radial motor 1.
A pinion 18 driven by a radial motor 17 is engaged with the pinion 18, and the pick-up base 14 is moved by rotation of a radial motor 17, and the pick-up 15 is moved in the radial direction of the disk 2.

Further, a photo sensor drive rack 19 is fixed to the pickup base 14. A cross roller cage 20 is slidably mounted on the cross roller guide member 13, and a cross roller drive rack 21 is provided on the inner periphery of the cross roller cage 20. The photo sensor drive rack 19 and the cross roller drive rack 21 are each engaged with a cross roller drive pinion 22 which is an integrated pinion. is selected so that the cross roller cage 20 moves at half the speed of the pick-up base 14.

Further, when the tip of the cross roller cage 20 faces the slit disk 12 and the pick-up 15 faces the outer edge of the disk 2, a slit 1 is provided at the tip of the cross roller cage 20.
A photo sensor 23 is fixed on the slit disk 12 so as to face each other on the circumference of the slit disk 12 whose radius is the outer end point of the photo sensor 2'. Therefore, the rotation of the radial motor 17 causes the pick-up 15 to move in the radial direction of the disk 2 at a predetermined speed, and the photo sensor 23 moves the slit disk 12 at a speed that is half the moving speed of the pick-up 15 in response to the movement of the pick-up 15. The position of the photo sensor 23 in the radial direction of the slit disk 12 becomes a position corresponding to the position of the pick-up 15 in the radial direction of the disk 2. When the photo sensor 23 moves to a position facing the slit 12'
From the inner end of the slit disk 12, the slit 12'
to the outer end of the slit disk 12.

On the other hand, a signal with a frequency proportional to the linear velocity of the disk 2 relative to the pickup detected from the pickup 15 is sent to the phase comparator 24 and the loop filter 25.
and a PLL circuit 27 consisting of a voltage controlled oscillator 26
and the output of the voltage controlled oscillator 26 is input to the frequency divider 2.
8 and is frequency-divided, and then input to a phase comparator 29 where the phase is compared with the output obtained by frequency-dividing the oscillation output of the crystal oscillator 30. crystal oscillator 3
The 0 oscillation frequency is set to a frequency proportional to the reference linear velocity due to the rotation of the disk 2.

On the other hand, the output of the photo sensor 23 due to the rotation of the slit disk 12 is input to the one-shot multivibrator 32 and the AND gate 33, and the signal obtained by inverting the output of the photo sensor 23 is input to the AND gate 34, and the output of the one-shot multivibrator 32 is input to the AND gate 34. The output is input to an AND gate 34, and a signal obtained by inverting the output of the one-shot multivibrator 32 is input to an AND gate 33.

Lead output A and delay output B of phase comparator 29
, the output of the AND gate 33, and the output of the AND gate 34, respectively, are connected to the multiplex circuit 3.
Enter 5.

36 is a phase lock detection circuit that detects that the PLL circuit 27 has phase-locked to the signal frequency of the pickup 15;
When the PLL circuit is in phase lock, it generates a low voltage output, and when it is not in phase lock, it generates a high voltage output. The output of the phase lock circuit 36 is input to the multiplex circuit 35, and when the PLL circuit 27 is not phase locked, the output is input to the multiplex circuit 35.
selects the outputs of AND gates 33 and 34,
The multiplex circuit 35 is configured so that when the PLL circuit 27 is phase locked, the multiplex circuit 35 selects the leading output A and the delayed output B of the phase comparator 29.

The output of the multiplex circuit 35 is input to a charge pump circuit 37.
The output is input to a low pass filter 38.

The multiplex circuit 35, charge pump circuit 37 and low pass filter 38 are constructed as shown in FIG. 3, for example.

The multiplex circuit 35 is a NAND gate 50
~53, inverter 54 and pull-up resistor 5
5, 56, leading output A, delayed output B,
The outputs of the AND gates 34 and 33 are input to NAND gates 50, 51, 52, and 53, respectively, and the NAND gates 50 and 51 are opened and closed by a signal obtained by inverting the output of the phase lock detection circuit 36 with an inverter 54. , NAND gates 52 and 53 are configured to open and close their gates by the output of the phase lock detection circuit 36,
The outputs of NAND gates 50 and 52 are wired-OR connected and output, and the outputs of NAND gates 51 and 53 are wired-OR connected and outputted.

The charge pump circuit 37 consists of an inverter 57, transistors 58 and 59, the transistors 58 and 59 are connected in series between the power supply +B and the ground, and the transistor 58 is driven by the output of the NAND gate 51 or 53.
Transistor 59 is a NAND gate 50 or 52
It is configured to be driven by an output obtained by inverting the output of the inverter 57.

The low-pass filter 38 is composed of a resistor 60 and a capacitor 61, and the output of the common connection point of the transistors 58 and 59 is applied thereto.

The output of the low-pass filter 38 is input to a spinning motor drive circuit 39, and the rotation speed of the spinning motor 1 is controlled by the output of the spinning motor drive circuit 39.

In this embodiment constructed as described above, the rotation of the spinning motor 1 causes both the disk 2 and the slit disk 12 to rotate at the same number of rotations. Further, the rotation of the radial motor 17 moves the pick-up base 14, and the movement of the pick-up base 14 causes the pick-up 15 to move in the radial direction of the disk 2 while facing the disk 2. Furthermore, due to the movement of the pick-up base 14, the cross roller cage 20 also moves in the same direction as the pick-up base 14 at 1/1/2 of the moving speed of the pick-up base 14.
Move at a speed of 2. Therefore, the photo sensor 23 picks up 15 in the radial direction of the slit disk 12.
Move at 1/2 the speed of .

On the other hand, one-shot multivibrator 3
The output pulse width of 2 is the time corresponding to the reference linear velocity V ₀ (m/sec) of the disk 2 for each position of the pickup 15, that is, the time required for the slit 12' to cross the photo sensor 23 due to the rotation of the slit disk 12. It is set as t ₀ =D(m)/V ₀ (m/sec).

Also, the reference linear velocity V ₀ (m/sec) at the distance R (mm) from the disk rotation center of the pick-up 15
The rotational speed N ₀ of the disk 2 is N ₀ = 6×10 ⁴ ×V ₀ /2πR (rpm),
This rotational speed is the reference linear velocity V ₀ (m/sec) for the position of the pickup 15 at the distance R (mm).
This is the reference rotation speed for.

Now, the rotation of the spinning motor 1 causes the disk 2 and the slit disk 12 to rotate, and the pickup 15 detects the position of the PCM signal on the track of the disk 2 and adjusts the linear velocity of the disk 2 with respect to the position of the pickup 2 in the radial direction of the disk. A proportional frequency output is generated and output to the phase comparator 24.

Further, due to the rotation of the slit disk 12, the photosensor 23 generates an output of n pulses (n is a positive integer) for each rotation of the slit disk 12. The frequency of this pulse output becomes smaller as the pick-up 15 is located closer to the outer circumference of the disk 2, but the pulse width corresponds to the linear velocity of the disk 2 with respect to the position of the pick-up 15 in the radial direction of the disk. Letting V be ≈D/V. The rotational speed N of the disk 2 corresponding to this linear velocity V is 6×10 ⁴ ×V/2
As mentioned above, it is πR (rpm). The rising edge of the output pulse of the photo sensor 23 triggers the one-shot multivibrator 32. Therefore, one-shot multivibrator 32
generates a pulse with a pulse width t ₀ as shown in a-1 of FIG. 4a. This pulse width t ₀ is determined by the photo sensor 23 when the disk 2 is rotating at the reference linear velocity V ₀ .
is the time required for the slit 12' to cross the slit 12', and is constant regardless of the position of the pickup 15 in the disk radial direction.

Therefore, the rotation speed N of disk 2 is the reference rotation speed N ₀
When the number of output pulses is larger than that, the output pulse of the photo sensor 23 has a pulse width t ₁ (t ₀
>t ₁ ), and the AND gate 34 generates a leading pulse as shown in a-3 of FIG. 4a. The pulse width of this advance pulse is (t ₀ −t ₁ ).

Further, when the rotation speed N of the disk 2 is smaller than the reference rotation speed N ₀ , the output pulse of the photo sensor 23 has a pulse width t ₂ (t ₂
>t ₀ ), and the AND gate 33 generates a delayed pulse as shown in a-5 of FIG. 4a. The pulse width of this delayed pulse is (t ₂ −t ₀ ).

When the rotational speed N of the disk 2 fluctuates from the reference rotational speed _N0 and the frequency of the output signal from the pickup 15 is outside the lock range of the PLL circuit 27, that is, the linear velocity V changes from the reference linear velocity _V0 to a predetermined value. When the distance is greater than 1, the phase lock detection circuit 36 generates a high potential output, and the NAND gates 52 and 53 of the multiplex circuit 35 are opened.
The outputs of AND gates 33 and 34 are selected,
A NAND gate 52 or 53 generates an output.
The NAND gate 52 outputs a leading pulse obtained by inverting the leading pulse from the AND gate 34, and the NAND gate 53 outputs a delayed pulse obtained by inverting the delayed pulse from the AND gate 33.

For example, if the linear velocity V is far from the reference linear velocity _V0 , the leading pulse shown at b-1 in FIG. 4b is output from the NAND gate 52, and the delayed pulse shown at b-2 in FIG. , the transistor 59 is on for the period of the leading pulse width, discharging the charge in the capacitor 61, and
During the delay pulse width, the transistor 58 is turned on and the capacitor 61 is charged. Therefore, the output voltage of the low-pass filter 38 is b-3 in FIG. 4b.
The waveform becomes as shown in , and this low-pass filter 3
The output voltage of 8 is controlled through the spinning motor drive circuit 39 so that the rotation speed of the spinning motor 1 and the rotation speed of the disk 2 become the reference rotation speed N ₀ , that is, the linear velocity becomes the reference linear velocity V ₀ . These controls correspond to coarse control.

That is, the rotation speed N corresponding to the position of the pickup 15 in the disk radial direction is detected, and the rotation speed N of the disk 2 is controlled to the reference rotation speed _N0 by the above-mentioned rough control, and by this rough control, the rotation speed N of the pickup 15 is The frequency of the output signal from PLL circuit 2
7, the PLL circuit 27 operates and at the same time the output of the phase lock detection circuit 36 becomes
When the phase lock of the PLL circuit 27 is detected, the potential becomes low, and the NAND gate 5 of the multiplex circuit 35
Gates 2 and 53 are closed, NAND gates 50 and 51 are opened, and the output from phase comparator 29 is input to charge pump circuit 37.

Therefore, when the linear velocity of the disk 2 relative to the disk radial position of the pickup 15 is faster than the reference linear velocity _V0 , the phase comparator 29 outputs an advanced output A, and when it is slower, a delayed output B is output.
Lead output A from phase comparator 29 is inverted by NAND gate 50 and output to charge pump 37, and delayed output B is inverted by NAND gate 51 and output to charge pump 37.

Now suppose that the linear velocity V of disk 2 is the reference linear velocity V ₀
The leading output A outputted from the NAND gate 50 occurs at a time as shown in b-1 in FIG. 4b, and the delayed output B outputted from the NAND gate 51 occurs at a time b-2 in FIG. If the time shown in FIG. 4 occurs, the output voltage of the low-pass filter 38 will have a waveform as shown in b-3 of FIG. 4b.

The rotational speed of the spinning motor 1 is determined by the output voltage of the low-pass filter 38.
The linear velocity V of the disk 2 with respect to the radial position of the disk 5 is controlled to be a reference rotational speed N ₀ at which the linear velocity V ₀ is the reference linear velocity V 0 .

Furthermore, when the spinning motor 1 is controlled by the output from the phase comparator 29, the control signal is obtained by a phase comparison signal between the frequency of the output signal from the pickup 15 and the oscillation frequency of the crystal oscillator 30. This control is performed with higher precision than the coarse control described above,
It can be called fine control.

Therefore, the accuracy of the coarse control described above is
The accuracy is sufficient as long as the output signal from 5 is within the lock range of the PLL circuit 27, and the reference linear velocity V ₀ generated by the one-shot multivibrator 32 is sufficient.
This means that the requirements for the precision of the width of the slit 12' and the processing precision of the width of the slit 12' can be relaxed.

In addition, in the above embodiment, the slit 12'
The length of is set to 1/2 of the radius of disk 2, and the moving speed of the photo sensor 23 in the disk radial direction is the moving speed of the pick-up 15 in the disk radial direction.
The explanation has been given using the case where the value is 1/2, but it is not necessarily 1/2 and other values may be used, but the length S of the slit 12' and the length L of the information surface in the radial direction of the disk The ratio S/L of the photo sensor 23 must be greater than or equal to the ratio X/Y of the moving speed X of the photo sensor 23 and the moving speed Y of the pickup.

That is, the length S of the slit 12' is determined by the moving speed X of the photo sensor 23 and the moving speed Y of the pick-up.
The information surface length L in the disk radial direction is the ratio X/Y.
The length must be greater than or equal to the value L×X/Y multiplied by .

It goes without saying that the radius of the slit disk 12 is determined by selecting the ratio.

Furthermore, the resolution increases as the number of slits 12' increases.

As explained above, according to the present invention, there is no need to use a potentiometer to detect the position of the pickup in the radial direction of the disk, and there is no need for a reciprocal circuit such as a multiplier that is required in the conventional case. , the circuit configuration is simple and inexpensive.

In addition, there is no need to separately detect the rotational speed of the spinning motor and the radial position of the disk in the pick-up to calculate the linear velocity of the disk relative to the radial position of the disk in the pick-up. can be directly detected to control the spinning motor.

Furthermore, the mechanism for controlling the linear velocity of the disk relative to the radial position of the disk in the pickup to the reference linear velocity is only a slit disk, a photo sensor, and a drive mechanism for the photo sensor, and its structure is simple.

Furthermore, the radius of the slit disk can be made smaller than the radius of the disk, making it possible to downsize the device in terms of packaging.

Furthermore, high-speed search is possible when selecting songs on a digital audio disk, and the time required for selecting songs can be shortened.

[Brief explanation of the drawing]

FIG. 1 is a conventional circuit diagram of a constant linear velocity control device for a disk-shaped information recording medium. FIG. 2 is an explanatory diagram of a constant linear velocity control device for a disc-shaped information recording medium according to an embodiment of the present invention.
Figure 3 shows the multiplex circuit in Figure 2,
Circuit diagram of charge pump and low pass filter. FIG. 4 is a waveform diagram for explaining the operation of an embodiment of the present invention. 1... Spinning motor, 2... Disc, 11...
Turntable, 12...Slit disk, 12'...
Slit, 13...Cross roller guide member, 14...
Pickup base, 15...Pickup, 16
...Pickup base drive rack, 17...Radial motor, 18...Pinion, 19...Photo sensor drive rack, 20...Cross roller gauge, 21...
Cross roller drive rack, 22...Cross roller drive pinion, 23...Photo sensor, 24 and 2
9... Phase comparator, 25... Loop filter, 26...
Voltage controlled oscillator, 27...PLL circuit, 28 and 3
DESCRIPTION OF SYMBOLS 1... Frequency divider, 30... Crystal oscillator, 32... One shot multivibrator, 35... Multiplex circuit, 36... Phase lock detection circuit, 37... Charge pump circuit, 38... Low pass filter, 39
...Spinning motor drive circuit.

Claims (1)

[Claims] 1. A motor that rotationally drives a disk-shaped information recording medium on which information is recorded on a spiral track, and a rectangular slit having a length corresponding to the radius of the disk-shaped information recording medium in the radial direction, and the disk-shaped information recording medium. a slit disk driven at a rotation speed proportional to the rotation speed of the medium; and a pick-up that moves in the radial direction of the slit disk facing the slit disk and reads information from the disk-shaped information recording medium. A sensor that generates an output pulse having a time width required for the width of the slit to pass through the slit at a position in the radial direction of the slit disk that is proportional to the radial position of the disk-shaped information recording medium, and the output pulse width of the sensor and the disk-shaped information recording medium. a detection means for detecting a difference between a reference pulse width corresponding to a reference linear velocity of the pickup, and a signal having a frequency proportional to the linear velocity of the disc-shaped information recording medium relative to the radial position of the pickup outputted from the pickup. A PLL circuit as a signal, a phase comparison means for comparing a phase of a frequency corresponding to the reference linear velocity and an output signal of the PLL circuit, and detecting whether or not the PLL circuit is in phase lock. If not, the output of the detection means is selected and the rotation speed of the motor is controlled by that output, and when the phase is locked, the output of the phase comparison means is selected and the rotation speed of the motor is controlled by that output. 1. A linear velocity control device for a disc-shaped information recording medium, comprising: a motor drive means for controlling the linear velocity of a disc-shaped information recording medium.