JPS6236301B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotational speed control method in an information disk reproducing device, and from the start of reproduction until a desired information signal is reproduced, the rotation speed is controlled according to the radial position of the information disk. By rotating the information disk using a phase error signal obtained by comparing the phases of the frequency signal and the rotation detection signal of the information disk, rapid tracking playback is possible, and the rotation speed can be controlled with good linearity, temperature characteristics, and stability. The object of the present invention is to provide a rotation speed control method for a reproducing device that can perform the following steps.

There are two methods for recording and reproducing information signals on a disk: a constant angular velocity method (hereinafter abbreviated as "CAV method") in which the rotation speed is always constant regardless of the radial position of the recording element or reproducing element on the disk; The constant linear velocity method (hereinafter abbreviated as CLV method) is a method in which the rotational speed of the disk is changed according to the radial position of the disc so that the relative linear velocity with the recording element or the reproducing element is constant. The CLV method allows higher density than the CAV method and has a higher effective utilization rate of the disk.The information disk on which information signals are recorded using the CLV method is reproduced at a constant linear speed.

However, the above-mentioned information disk has a flat portion 2 on the surface of the disk 1 as shown in FIG. By alternately repeating the long oval pits (concavities) 3, information signals such as color video signals and audio signals are recorded, and between the track center lines of adjacent information signal recording tracks. If the tracking control reference signals _P1 and _P2 , which have different frequencies lower than the recording band of the information signal, are recorded alternately every rotation of the disc, reproduction using the CLV method will not work. There is.

That is, in this disc 1, for example, the sliding contact surface 4b with the disc 1 has a sharp apex 4c as an introduction part, and is a flat surface including an electrode part 4a formed on the rear end surface,
In addition, the scanning needle 4 has a sliding contact surface 4b whose area is selected to be large enough to simultaneously contact a plurality of pits 3 in order to maintain a long needle life, thereby preventing slight changes in capacitance with the electrode portion 4a. a read and recorded information signal;
and previously recorded tracking control reference signal _P1 ,
_P2 is regenerated, and the scanning needle 4 is used for tracking control which is simultaneously regenerated from both sides of the helical track to be scanned among the tracks t ₁ , t ₂ , t ₃ , t ₄ , t ₅ of each spiral rotation. Tracking is controlled by the level difference between reference signals _P1 and _P2 .

Here, the above tracking control reference signal _P
1 and _P2 are used to distinguish and separate the reproduced signals through a resonant circuit, but if the rotational speed of disk 1 is different from that during recording, _P1 and _P2 cannot be separated and reproduced, making tracking impossible. The range in which this tracking can be controlled varies depending on the Q of the resonant circuit, but normally it is necessary that the difference between the number of revolutions during recording and that during reproduction be within about ±5%. However, in the CLV method, since the rotation speed varies depending on the radial position of the information disk of the reproduction element, tracking cannot be achieved at rotation speeds exceeding this range of ±5%, and if tracking cannot be achieved, accurate reproduction cannot be achieved. The signal cannot be obtained, and the synchronization signal in the reproduced signal, which is the basis of the rotation speed, cannot be accurately obtained, making it impossible to accurately reproduce the information signal.

In addition, a reference signal for tracking control may be recorded if grooves are formed for tracking or tracking is performed using a light beam for tracking control at the front and rear positions in the scanning direction of the light beam for signal reproduction. Even when performing equal-velocity reproduction on an information disk that has not been subjected to any The motor's servo system could not operate normally, and it took a long time to obtain accurate reproduction information signals.

The present invention eliminates the above-mentioned drawbacks, and an embodiment thereof will be described below with reference to FIG. 2.

FIG. 2 shows a block system diagram of an embodiment of the rotational speed control method in the information disk constant-velocity reproducing apparatus according to the present invention. In the figure, 5 is a turntable 6
Directly connected to a potentiometer or feed screw provided for detecting the radial position of the scanning needle 5 and a reproducing element (not shown) such as a light beam with respect to the information disk 7 placed above. The DC voltage taken out from the slider of the sliding resistor, such as a sliding resistor, is applied to a voltage controlled oscillator (VCO) 8 as a control voltage. This allows VCO8
A signal whose frequency changes depending on the position of the reproducing element with respect to the information disk 7 is extracted, appropriately counted down, and applied to the contact a of the changeover switch 9. First, to explain the operation at startup, the changeover switch 9, together with the changeover switch 12 described later, is connected to contact a at the time of startup, so the oscillation output of the VCO 8 is connected to a countdown circuit (not shown). , is applied to the phase comparator 10 through the changeover switch 9 as a rotation reference signal.

On the other hand, a motor 1 for rotating the information disk 7
4 rotation speed is detected by the rotation speed detector 11,
Pulses with a frequency corresponding to the rotation speed are supplied to the phase comparator 10 through the changeover switch 12, where they are passed through a countdown circuit (not shown) to the VCO.
The phase is compared with the oscillation output of 8. Phase comparator 10
The output phase error signal passes through the servo circuit 13 and controls the rotation speed of the motor 14.

As a result, the rotational frequency of the motor 14 is changed to VCO
It is rotated synchronously with the oscillation output of 8. here,
Since the VCO 8 has good linearity, temperature characteristics, and stability, the oscillation frequency corresponding to the position information on the information disk 7 of the reproducing element can be easily set to within ±2% of the normal value. The rotation speed of the motor 14 is also ±2 of the normal value for position information.
The difference is within %, and tracking can be done quickly.

Here, the purpose of the isolinear speed reproducing device is to obtain a rotational speed corresponding to the radial position of the information disk 7 of the reproducing element, but the conditions are good linearity, good temperature characteristics, and stability. In order to satisfy these conditions,
It is necessary to minimize the number of signal conversion circuits used to obtain changes in rotational speed from position information, and to use circuits with good linearity. However,
According to this embodiment, the position information is converted into frequency information by the VCO 8 and used as the reference signal for rotation, so the number of signal conversion circuits is small, and the VCO
8 performs V-F conversion and is excellent in terms of linearity, stability, etc.

In this way, the disk rotation speed of the isolinear speed playback device is kept approximately equal to the rotation speed during recording depending on the radial position of the information disk of the playback element (this is roughly adjusted by adjusting the rotation speed). Therefore, even when the information disc 1 shown in the first figure is reproduced, the tracking control reference signal can be accurately discriminated and separated.

Next, when tracking is established, the changeover switches 9 and 12 are switched to the contact b side by a pulse obtained by branching from a tracking servo circuit (not shown). As a result, the stable reference frequency from the reference oscillator 15 is supplied to the phase comparator 10 through the changeover switch 9, while the reproduction synchronization signal input to the input terminal 16 is supplied through the changeover switch 12. By applying both phase error signals to the motor 14 through the servo circuit 13, the motor 14 receives the reproduction synchronization signal from the reference oscillator 15.
The rotation speed is controlled to match the output reference frequency. Here, since information signals, tracking control reference signals, etc. are recorded in advance on the information disk 7 at a constant linear speed, the motor 14 also moves linearly as the reproducing element moves toward the inner circumference of the disk 7, just as during recording. The rotational speed is gradually increased to keep the speed constant. That is, the motor 14 is controlled to rotate at exactly the same number of rotations as when the information disk 7 is recorded.

It should be noted that during reproduction of an information disk having a tracking groove, the changeover switches 9 and 12 are switched to the contact b side when the rotational speed reaches a level at which a reproduction synchronization signal can be obtained approximately accurately. That is, it is performed when the desired information signal is reproduced. Furthermore, by making the output oscillation frequencies of the rotational speed detector 11 and the VCO 8 the same, a countdown circuit on the output side of the VCO 8 is unnecessary, and the circuit configuration becomes simple.

Furthermore, when a CAV type information disc is to be reproduced at a constant angular velocity, by closing and connecting only the changeover switch 9 to the contact b side, uniform angular reproduction can be performed with extremely simple operation and stably.

As described above, the rotational speed control method in the information disk reproducing apparatus according to the present invention includes a motor that rotates the information disk on which a signal is recorded, a rotational speed detector that detects the rotational speed of this motor, and a rotation speed detector that detects the rotational speed of this motor. A sliding resistor that detects the radial position of the information disk of the reproduction element that picks up and reproduces the recorded signal and outputs a signal according to the position, and a sliding resistor that outputs a signal according to the position. a variable frequency oscillator whose output oscillation frequency is varied and outputs a frequency signal according to the position; a first changeover switch that selectively outputs one of the output signal of the rotation speed detector and the synchronization signal of the information signal; , a second changeover switch that selects and outputs either the output of the variable frequency oscillator or a predetermined reference frequency; and a phase comparison between the output signal of the second changeover switch and the output signal of the first changeover switch, using the output signal of the second changeover switch as a reference signal. It consists of a phase comparator and a servo circuit that controls the rotation speed of the motor using the output phase error signal of the phase comparator. The output signal of the rotation speed detector is outputted from the second switch, and the output signal of the variable frequency oscillator is outputted from the second changeover switch to obtain the rotation speed corresponding to the position in the radial direction of the information disk of the reproducing element. After the information signal is reproduced, the first changeover switch outputs a reproduction synchronization signal, and the second changeover switch outputs a predetermined reference frequency so that the relative linear velocity between the reproduction element and the information disk becomes constant. Since the rotational speed of the information disk is controlled, when playing back an information disk in which a tracking control reference signal is recorded on both sides of the information signal track or multiplexed with the information signal, the speed is constant. It is possible to perform stable tracking using this method, and it is also possible to rapidly rotate information discs in which no reference signal for tracking control is recorded in synchronization. Complete rotation speed control is possible with a simple switch change and can be performed automatically, and the conversion from position information to rotation is only one V-F conversion using a variable frequency oscillator, which improves linearity and It has the advantage that it has good temperature characteristics and stability, and can also perform constant angular velocity reproduction by operating the first and second changeover switches.

[Brief explanation of the drawing]

FIG. 1 is a partially enlarged perspective view showing an example of the reproduction state of the information disk proposed by the present applicant together with a scanning needle, and FIG. 2 is a block system diagram showing an embodiment of the system of the present invention. 1, 7... Information disk, 8... Voltage controlled oscillator (VCO), 9, 12... Changeover switch, 10... Phase comparator, 11... Rotation speed detector, 14... Motor, 1
5...Reference oscillator.

Claims (1)

[Claims] 1. A motor that rotates the information disk, a rotation speed detector that detects the rotation speed of the motor, and a reproducing element that picks up and reproduces signals recorded on the information disk, detecting the position in the radial direction of the information disk. a sliding resistor that outputs a signal according to the position; a variable frequency oscillator whose output oscillation frequency is changed according to the output signal of the sliding resistor and outputs a frequency signal according to the position; a first selector switch that selects and outputs one of the output signal of the rotation speed detector and a synchronization signal in the information disk reproduction signal; and a second switch that selectively outputs one of the output signal of the variable frequency oscillator and a predetermined reference frequency. changeover switch, and the first changeover switch using the output signal of the second changeover switch as a reference signal.
It consists of a phase comparator that compares the phase with the output signal of the changeover switch, and a servo circuit that controls the rotation speed of the motor based on the output phase error signal of the phase comparator. Until the signal is regenerated, the first changeover switch outputs the output signal of the rotation speed detector, and the second changeover switch outputs the output signal of the variable frequency oscillator, so that the regeneration element After reproducing the required information signal, the first changeover switch outputs a reproduction synchronization signal, and the second changeover switch outputs a reproduction synchronization signal according to the radial position of the information disk. A rotational speed control method in an information disk reproducing apparatus, characterized in that the rotational speed of the information disk is controlled so that a relative linear velocity between the reproducing element and the information disk is constant by outputting a frequency.