JPS5885974A - Equilinear speed controller of disk player - Google Patents

Abstract

PURPOSE:To make coincide automatically the period of a reproduced signal with the relative linear speed between a disk recording medium and a pickup, by generating the sawtooth wave which is synchronous with the revolution of a motor and controlling the inclination of the sawtooth wave in order to control the speed of revolution. CONSTITUTION:The signals are reproduced from a disk recording medium 1 through a pickup 3 attached to a mobile stage 4 which is moved by a pulse motor 5. The number of steps of the motor 5 is counted by an up-down counter 6, and the reference voltage corresponding to the count value of the counter 6 is generated 7 and fed to a comparator 13. The frequency proportional to the number of revolutions of a DC motor 2 is generated 8 to receive the waveform shaping 9. The square wave is applied to a sawtooth wave generating circuit 10. The frequency of the signal of a reproduced signal processing circuit 4A is compared 11 with the frequency of the reference signal 12. The difference of these frequencies is applied to the circuit 10 to control the inclination of the sawtooth wave. The reference voltage 7 is compared 13 with the level of the circuit 10 and undergoes the pulse width-voltage conversion 14 and then the power amplification 15. Thus the speed of the motor 2 is controlled. As a result, the correct reproduction is ensured even though the linear speed is unknown.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that can sequentially reproduce signals in good condition from a disk-shaped recording medium whose recording density is constant from the inner circumference to the outer circumference, and in particular, Even if the relative speed of the pickup and the disc-shaped recording medium recorded at that speed is unknown, the period or frequency of the playback signal picked up from the disc-shaped recording medium can be automatically adjusted to a specified period or frequency. The present invention relates to a constant linear velocity control device in a disc player that can be controlled.

Conventionally, as the above-mentioned constant linear velocity control device,
The distance from the center of rotation of the disk-shaped recording medium to the pickup is converted into voltage using a potentiometer, etc.
A known method is to obtain a voltage and frequency inversely proportional to the distance using a function generator, a voltage controlled oscillator, etc., and to control the constant linear speed of the motor using the voltage and frequency. However, in this apparatus, when a disk-shaped recording medium whose linear velocity is unknown is used, it is necessary to change the rotational speed of the motor so that the linear velocity is the original linear velocity of the disk-shaped recording medium. To do this, the constants of the function generator, voltage-controlled oscillator, etc. described above must be
There is an inconvenience that the linear velocity must be changed every time a disc-shaped recording medium whose linear velocity is unknown is used.

The present invention has been made to solve the above-mentioned disadvantages in the conventional apparatus, and has a simple configuration, so that even when a disk-shaped recording medium whose linear velocity is unknown is used, the disk-shaped recording medium has It is an object of the present invention to provide a constant linear speed control device for a disc player that can automatically control the rotational speed of a motor so as to maintain the original linear speed.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

The figure is a block diagram showing an embodiment of a constant linear velocity control device according to the present invention. In the figure, reference numeral 1 denotes a disk-shaped recording medium, which is rotationally driven by a DC motor 2 . 6 is attached to the movable base 4 and the above-mentioned disk-shaped recording medium 1
This is a pickup that extracts the playback signal from. The movable table 4 is configured to be moved over the disk-shaped recording medium 1 in the radial direction by a pulse motor 5. Further, the movable table 4 is provided with a reproduction signal processing circuit 4A for processing the reproduction signal from the pickup 5. 6 is an up/down counter that counts the number of driving steps of the pulse motor 5 mentioned above.

The up/down counter 6 counts up when the moving table 4 moves on the disk-shaped recording medium 1 from the inner circumference toward the outer circumference, and in the opposite direction, that is, when the moving table 4 moves on the disk-shaped recording medium 1. When moving from the outer circumference toward the inner circumference, it acts like a countdown. Reference numeral 7 denotes a reference voltage generating circuit, and a constant voltage corresponding to the count value of the up/down counter 6 is obtained at its output. Reference numeral 8 denotes a frequency generator that can obtain a frequency proportional to the number of rotations of the DC motor 2. The output of the frequency generator 8 is supplied to a waveform shaping circuit 9, from which a square wave signal is output. 10 is a sawtooth wave generation circuit, from which a sawtooth wave signal synchronized with the square wave signal output from the waveform shaping circuit 9 described above is obtained. , 11 is a frequency comparator that compares the period or frequency of the reproduction signal from the reproduction signal processing circuit 4A described above and the reference signal from the reference signal input terminal 12, and the comparison output is sent to the above-mentioned sawtooth wave generation circuit 1. (The reference voltage from the reference voltage generation circuit 7 and the sawtooth wave signal from the sawtooth wave generation circuit 10 are supplied to the level comparator 1.
The level comparator 13 outputs a speed error signal. Further, the above-mentioned output of the level comparator 16 is converted into a DC voltage by the pulse width-voltage conversion circuit 14, and then supplied to the DC motor 2 via the power amplifier circuit 15, so that the rotation speed of the motor 2 is controlled.

Here, if the distance from the center of rotation of the disk-shaped recording medium 10 to the pickup 6 is r, and the relative speed between the pickup 3 and the disk-shaped recording medium 1 is V, then the rotation period τ of the motor 2 is given by the following equation.

2πr T = lower
(1) By the way, if we synchronize the output of the frequency generator 8 with the edges of the square wave signal obtained via the waveform shaping circuit 9 and create a sawtooth wave signal with an elephant slope α, the sawtooth wave signal will become Expressed as a function of voltage and time, it is expressed by the following formula (%) (2) Then, assuming that a sawtooth signal is generated that provides a voltage proportional to the distance from the center of rotation of the disk-shaped recording medium 1 to the pickup 3, The sawtooth signal can be expressed as follows.

■= βr (where β is a constant) (3) Above (
When t is determined from equations 2) and (3), since αt = /r, it becomes -βr(4) t-go.

Comparing the above equation (4) with equation (1), it can be seen that the slope α of the 9-wave sawtooth signal corresponds to the linear velocity fK, v.

In the present invention, the original linear velocity is obtained by changing the slope of the above-mentioned sawtooth wave signal using control logic.

Next, seven operations of the device according to the present invention shown in the figure will be explained.

Assume now that the pickup 6 is located at a distance r from the center of rotation of the disk-shaped recording medium 10. At this time, the reference voltage V based on the above equation (3) is obtained at the output of the reference voltage generation circuit 7. The up/down counter 6 calculates the number of drive steps generated when the pickup 6 is moved by the distance r by the pulse motor 5 using the reference voltage V.
This is the voltage generated by the reference voltage generation circuit 7 in accordance with the counted value. Note that the reference voltage generation circuit 7 described above can be configured with an n-bit D/A converter, and in the case of n-bits, the pickup 3 moves from the inner circumference to the outer circumference of the disk-shaped recording medium 1; 2n voltages can be obtained.

On the other hand, if the initial setting of the sawtooth wave signal is α0, and the pickup 3 is located at a distance r from the rotation center of the disk-shaped recording medium 1, the rotation period To of the motor 2 is as described above (4). From the formula, To /r
(5) α0, and the linear velocity ν is −2π from Equation 7 (1) above.
r(6) O. If the above-mentioned linear velocity V deviates from the original linear velocity, the period or frequency between the signal obtained from the reproduction signal processing circuit 4A provided in the movable table 4 and the pre-known reference signal are compared by the frequency comparator 11, and by changing the linear velocity ν by changing the slope α of the sawtooth wave signal generated by the sawtooth 9 wave generation circuit 10 according to the control signal output from the comparator 11, It is possible to obtain a linear velocity of

As described above, according to the present invention, even when using a disk-shaped recording medium whose linear velocity is unknown, the period or frequency of the reproduced signal that is sharply increased from the disk-shaped recording medium can be adjusted to the original period or frequency. Therefore, it is possible to provide a constant linear velocity control device for a disc player that can automatically control the slope of a sawtooth wave signal and obtain the original linear velocity.

[Brief explanation of the drawing]

The figure is a block diagram showing an embodiment of a constant linear velocity control device according to the present invention. 1: disk-shaped recording medium, 2: DC motor, 6: pickup, 4: moving table, 4A: reproduction signal processing circuit, 5: pulse motor, 6: up/down counter, 7: reference voltage generation circuit, 8: frequency Generator, 9-waveform shaping circuit, 1u: sawtooth wave generation circuit, 11: comparator, 12: reference @ No. 5 input terminal, 16: level comparator, 14: pulse width-voltage conversion circuit, 15: power amplifier circuit , Patent applicant Akai Electric Co., Ltd.

Claims (1)

[Claims] In a device for obtaining a reproduced signal from the disc-shaped recording medium recorded at a constant linear velocity and the relative speed of the pickup being unknown, a voltage corresponding to the distance from the center of rotation of the disc-shaped recording medium to the pickup is provided. and a sawtooth wave generation means that generates a sawtooth wave signal synchronized with the rotational frequency of the motor, and the slope of the sawtooth wave signal is changed in accordance with the relative speed. A constant linear velocity control device for a disc player, characterized in that the cycle or frequency of the reproduction signal picked up from the disc-shaped recording medium is automatically controlled to be a specified cycle or frequency.