JPH0650817Y2 - Scanning circuit of video disk playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a scanning circuit of a laser type video disc reproducing apparatus, and more specifically, a video for scanning a CLV (constant linear velocity) video disc for a predetermined length in the radial direction. The present invention relates to a scanning circuit of a disc reproducing device.

(Background of the invention and problems to be solved by the invention) When the CLV disk is scanned, the time base collector does not operate normally until the spindle servo device follows, so the color signal is unstable and difficult to see. It was

It is an object of the present invention to provide a scanning circuit for a video disc reproducing apparatus, which improves the stability of a spindle servo device and solves the above problems.

(Means for Solving the Problem) The scanning circuit of the present invention is a scanning circuit of a laser type video disk reproducing apparatus for scanning a CLV video disk for a predetermined length in a radial direction, and includes a reference oscillator and a frequency division ratio changing means. A frequency divider which has an oscillation frequency of a reference oscillator and generates a reference horizontal synchronizing signal; jump pulse generation means for causing an optical pickup to jump a plurality of tracks within a scanning range by a scanning instruction; Phase comparison between the reproduction horizontal synchronization signal and the reference horizontal synchronization signal for the second predetermined period until the spindle servo circuit locks after the first predetermined period shorter than the period from when the optical pickup starts the track jump. Holding means for holding the phase comparison output of the phase comparator for spindle servo, and the optical signal from the time when the first predetermined period has elapsed. The phase difference between the reproduction horizontal synchronizing signal and the reference horizontal synchronizing signal is out of the predetermined range during the period from the third predetermined period until the pickup finishes the track jump to the release of the hold by the holding means. , The reproduction horizontal synchronizing signal and the reference horizontal synchronizing signal are aligned within a predetermined phase difference. The feature is that the scanning operation is performed by repeating the jump and the steady reproduction.

(Operation) According to the present invention configured as described above, the phase comparison output is not held until the first predetermined period of time has elapsed since the jump pulse was generated. This is because the ratio pickup does not immediately perform the jump operation even if the jump pulse is generated, but the jump operation is performed with a time delay. The phase comparison output is held for a second predetermined period from when the first predetermined period has elapsed. This hold prevents the spindle servo apparatus from being controlled to an erroneous phase by noise at the time of off-track and the signal of the track during the jump. The third predetermined period is shorter than the second predetermined period, and the track jump ends when the third predetermined period has elapsed. However, it takes time until the tracking servo device and the spindle servo device are properly locked after the completion of the tracking jump. Furthermore, regarding the spindle servo device, it is necessary for the video disk to pull in a phase different from the phase before the track jump due to CLV, and during this period, a period of (second predetermined period−third predetermined period) is required. I need. Therefore, when the phase difference between both inputs of the phase comparator is outside the predetermined range at the timing of the end of the third predetermined period, the frequency division ratio of the frequency divider is changed. As a result,
The phase between both inputs of the phase comparator falls within the predetermined phase, and the hold of the phase comparison output is released at the end of the second predetermined period. For this reason, the spindle servo device enters the control state from the phase close to the target, the responsiveness is improved, the rotation of the video disk is stabilized, and the operation of the time base collector is also stabilized.

(Embodiment) Hereinafter, the present invention will be described with reference to an embodiment.

FIG. 1 is a block diagram showing the construction of an embodiment of the present invention.

The optical pickup 2 detects the signal recorded on the CLV video disc 1. The signal detected by the optical pickup 2 is supplied to the signal reproducing circuit 3 and reproduced. The horizontal cycle signal in the reproduction signal from the signal reproduction circuit 3 is supplied to the spindle motor servo phase comparator 4 and is compared in phase with a frequency division output which is a reference horizontal synchronization signal from the frequency divider 9 described later.
The phase comparison output of the phase comparator 4 is an analog switch 5 ₁ and a capacitor 5 ₂ for selectively holding the phase comparison output.
And the output from the hold circuit 5 is amplified by the amplifier 6 and then supplied to the spindle motor 7 so that the linear velocity of the video disk 1 becomes constant with respect to the position of the optical pickup 2. Spindle motor 7
Control the rotation speed of.

On the other hand, the oscillation output of the reference crystal oscillator 8 is supplied to the frequency divider 9 having a frequency division ratio changing circuit, and the frequency division output is supplied to the phase comparator 4 and the phase detection circuit 10 to supply the signal reproduction circuit 3
The phase difference with the horizontal synchronizing signal output from is detected. The output of the phase difference detection circuit is supplied to the frequency divider 9 via the switch 11. The detected phase difference of the phase difference detection circuit 10 is, for example, +90.
When it is in the range of 90 ° to 180 ° or −90 ° to 180 °, the frequency divider 9 divides the frequency division ratio n by (n + a),
It is configured to be changed to (na).

The controller 12 comprises a microcomputer, an analog switch 5 ₁ of the switching controller for receiving a scan instruction signal, the switch
Opening / closing control 11 and drive control for driving the optical pickup 2 to jump in the radial direction of the video disk 1 are performed.

The operation of the above-described embodiment will be described with reference to the flowchart shown in FIG.

When the scanning instruction signal is input to the control device 12, the tracking servo system of the optical pickup 2 is instructed to generate a jump pulse (step S ₁ ). The actual track jump is performed by the generation of the jump pulse. A predetermined period within the delay period from the start of the jump operation to the offtrack after the instruction to generate the jump pulse, for example, several
waits for the lapse of msec (Step S _2), when the predetermined period has elapsed, the analog switch 5 ₁ is controlled to the OFF state (Step S _3). This is because by holding the phase comparison output from the phase comparator 4 when the above predetermined period has elapsed,
This is because the spindle servo device is prevented from being controlled in an incorrect phase by noise at the time of track-off and a signal of a track during a jump of several tracks.
Waits for elapse of a predetermined time period for example, several msec following step S ₃ (Step S _4), the tracking servo system relative to the generation of jump brake pulse is instructed (step
S ₅ ). The jump brake pulse has a polarity opposite to that of the jump pulse and substantially brakes the jump of the optical pickup.

Following jump brake Step S ₅ waits for elapse of a predetermined time, for example several msec (Step S _6), the switch 11 is controlled in the on state (step S _7). The output of the phase difference detection circuit 10 is supplied to the frequency divider 9 by controlling the switch 11 to the ON state. As a result, the phase difference detection circuit 10 causes the phase difference between the horizontal synchronizing signal in the reproduction signal from the signal reproduction circuit 3 and the frequency division output from the frequency divider 9 from + 90 ° to +180.
When it is °, the division ratio is changed to (n + a) and the phase difference is −
When 90 ° to −180 °, the division ratio is changed to (na). When the phase difference is other than the above, that is, when the phase difference exceeds −90 ° and is less than + 90 °, the division ratio is changed to n. , And is supplied to the phase comparator 4 for phase comparison. Further, the tracking servo circuit is activated. (Step S _7).

That is, after the jump brake pulse is generated, the step
After a predetermined time in S _6, the track jump is finished, but actually then the tracking servo circuit and several ms until the spindle servo circuit is properly locked
It takes about ec. As for the spindle servo circuit,
Due to the CLV disc, it takes some time to pull in a phase different from the previous phase. So jump phase difference of the phase difference is more than a predetermined between the input of the phase comparator 4 (after a lapse of Step S ₆₎ the extent of the timing for stopping (-
90 ° to −180 °, + 90 ° to + 180 °), the frequency division ratio n of the frequency divider 9 for obtaining the reference signal from the oscillation output of the reference crystal oscillator 8 is set to (n−a) or (n + a). with operating the division ratio changing circuit for changing the tracking servo circuit is in the operating state (step S _7).

By executing step S ₇ , the phase difference between both inputs of the phase comparator 4 exceeds a value of −90 ° and a value of less than 90 ° by several phase comparisons.
S _8), prohibits the operation of the frequency dividing ratio changing circuit controls the analog switch 5 ₁ simultaneously turned on, and supplies the output of the phase comparator 4 to the amplifier 6 (step S _9).

The period of step S ₈ is set to several msec, for example, but since the phase comparison by the phase comparator 4 is performed by the horizontal synchronizing signal, the period is 63.5 μs in the NTSC system, and the period of several msec is too long. It is a period that can be said.

Play Following step S ₉ (several tens to several hundreds of 100 msec) is made, when not yet reached the desired position is executed from Step S ₁ again (step S _10).

As described above, the spindle servo circuit can start the control from a position close to the target, and the responsiveness is improved. Therefore, the rotation of the video disc 1 becomes stable,
As a result, the operation of the time base collector is also stable.

Incidentally, the hold of the phase comparison output, in the above embodiment a case has been exemplified using the analog switch 5 _1,
The phase comparison logic itself of the phase comparator 4 may be prohibited by a logic circuit. Similarly, the prohibition and permission of the frequency division ratio change can be performed using a logic circuit.

(Effect of the Invention) As described above, according to the present invention, the track jump is repeated to perform scanning, and the spindle servo device enters the control state from a phase close to the target during the track jump. The servo device can be stabilized and the responsiveness is improved. Also, since the rotation of the video disc becomes stable, the operation of the time base collector becomes stable, and the problem that the color signal is unstable and difficult to see is solved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. FIG. 2 is a flow chart for explaining the operation of one embodiment of the present invention. 1 ... Video disc, 2 ... Optical pickup, 3 ...
Signal regeneration circuit, 4 phase comparator, 5 hold circuit, 5 ₁ analog switch, 6 amplifier, 7 spindle motor, 8 reference crystal oscillator, 9 frequency divider, 10 ...... Phase difference detection circuit, 11 …… Switch, 12 …… Control device.

Claims (1)

[Scope of utility model registration request] 1. A scanning circuit of a laser type video disk reproducing apparatus for scanning a CLV video disk in a radial direction for a predetermined length, the scanning circuit having a reference oscillator and frequency division ratio changing means, and dividing an oscillation frequency of the reference oscillator. A frequency divider that circulates to generate a reference horizontal synchronizing signal, a jump pulse generation means that causes the optical pickup to jump a plurality of tracks within a scanning range by a scanning instruction, and a time from when the jump pulse is generated until the optical pickup starts the track jump. Phase comparison of a spindle servo phase comparator that compares the phase of the reproduction horizontal synchronization signal with the reference horizontal synchronization signal for a second predetermined period from when the first predetermined period shorter than the period elapses until the spindle servo circuit locks Hold means for holding the output, and the optical pickup ends the track jump after the lapse of the first predetermined period. When the phase difference between the reproduction horizontal synchronizing signal and the reference horizontal synchronizing signal is outside the predetermined range during the period from the lapse of the third predetermined period until the hold is released by the holding means, the reproduction horizontal synchronizing signal And a reference horizontal synchronization signal within a predetermined phase difference, the frequency division ratio change instruction means for giving an instruction to change the frequency division ratio of the frequency divider is provided. A scanning circuit for a video disc reproducing apparatus, characterized in that the scanning operation is performed by repeating the scanning operation.