JPH0477967B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical system for reproducing signals from a disk on which signals are recorded in a manner readable by irradiation of a light beam onto a spiral or concentric track. The present invention relates to a system for making a track jump of a light beam for signal reading on a disc player, particularly on a disc, in the radial direction of the disc by one or more tracks.

(Prior Art) In an optical disc such as an optical video disc, a signal is recorded in a spiral track formed by an arrangement of pits, and in an optical disc player for reproducing signals from such a disc, a rotating A light beam is irradiated onto the disk from an optical head that moves in the radial direction of the disk to read a signal from the disk track, and the read signal is reproduced to achieve the desired reproduction. However, when accessing a specified address on a disc track in such an optical disc player, or in the case of an optical video disc player, speed changes such as double-speed playback in the forward direction, still playback, double-speed playback in the reverse direction, etc. When performing reproduction, a light beam for reading a signal is track-jumped on the disk in the radial direction of the disk by one or more tracks.

This tracking jump is a signal that ensures that the signal reading light beam is correctly positioned on the track of the disk by supplying a drive voltage based on a tracking error signal that indicates the tracking status of the signal reading light beam with respect to the disk. When the supply of drive voltage based on the tracking error signal to the tracking drive means that moves the reading light beam in the radial direction of the disk is cut off, that is, when the tracking servo is turned off, the tracking drive means is turned off. This is carried out by supplying as a drive voltage a track jump signal consisting of an acceleration pulse of one polarity followed by a deceleration pulse of the other polarity.

Specifically, in the case of an optical video disk player, the disk has a constant angular velocity with one frame of the video signal as one track revolution, and the vertical retrace period varies from the inner circumference to the outer circumference of the disk. When the disks are lined up in the radial direction, and when the optical beam for signal reading is to be track-jumped by one revolution of the track, the movement of the optical beam on the disk and the movement of the optical beam supplied to the tracking drive means are shown in Fig. 4. As shown in the relationship between the drive voltage DV and the tracking error signal TE obtained from the tracking error detection means, when the light beam is located in the vertical retrace period of a certain track T(0), the drive voltage DV By setting Vd to a predetermined value of one polarity and supplying an acceleration pulse DP to the tracking drive means, the light beam is accelerated in the direction corresponding to the polarity of the acceleration pulse in the radial direction of the disk, and the light beam is moved from the starting point. When reaching the intermediate position between the circumference T(0) and the target next circumference T(1), change the drive voltage DV to a predetermined value Vb of another polarity and supply the deceleration pulse BP to the tracking drive means. As a result, the light beam is decelerated and brought to the target circumference T(1). In this case, the absolute values of the voltage of the acceleration pulse DP and the voltage of the deceleration pulse BP are made equal,
By making the time of the acceleration pulse DP equal to the time of the deceleration pulse BP, the light beam is directed to the target circumference T(1)
Stops exactly on top and never goes too far.

Even when the light beam for signal reading is track-jumped by multiple tracks, as shown in FIG. A method has been considered in which the acceleration pulse DP is supplied until the position is reached, and the deceleration pulse BP is supplied from the point at which the intermediate position is reached.
However, in this case, when the track jump number N is large, the acceleration energy becomes large, so
Even if the light beam is decelerated by the deceleration pulse BP, the light beam does not stop on the target circumference T(N) and travels too far. Therefore, when a track jump is to be performed for a plurality of track revolutions, a method is adopted in which the track jump is not performed at once but is repeated for one revolution a plurality of times.

(Problem to be Solved by the Invention) However, this method of repeating the track jump for one round multiple times and resulting in a track jump for multiple rounds requires a certain amount of time between each track jump. Therefore, it takes a considerable amount of time to make a track jump for multiple rounds, and in the case of an optical video disc player, when the disc has a constant angular velocity as mentioned above, the track jump number N is large. In this case, the arrival position of the light beam after the track jump deviates from the vertical retrace period, and there is an inconvenience that noise occurs in the upper or lower part of the reproduced screen after the track jump.

In view of this, the present invention is designed to make it possible to make a track jump for a plurality of laps in a short period of time while accurately stopping on a target lap.

(Means for solving the problem) After an acceleration pulse is supplied to the tracking drive means in the case where the tracking jump is made by one round as described above, and the light beam is moved while being accelerated in a direction according to the polarity of the acceleration pulse. , when the drive voltage to the tracking drive means is reduced to zero without any deceleration pulses being supplied, the light beam remains for a considerable period of time.
Due to inertia, it continues to move at a constant speed in the same direction.

Focusing on this point, in the present invention, the supply of the drive voltage based on the tracking error signal to the tracking drive means is cut off according to the tracking jump instruction, and the voltage of the first polarity is used as an acceleration pulse for a predetermined period of time. After supplying the acceleration pulse to the driving means, after a time sufficiently shorter than the natural resonance period of the tracking driving means, a voltage of the second polarity whose absolute value is approximately equal to the voltage of the first polarity is applied for the above-mentioned predetermined time. By supplying a deceleration pulse for a substantially equal amount of time to the tracking drive means, a light beam for reading a signal on the disk is track-jumped in one direction in the radial direction of the disk by one or more turns of the track.

The time during which the acceleration pulse and the deceleration pulse are supplied is the same even when the track jump is performed for a plurality of revolutions as when the track jump is performed for one revolution. The purpose of making the non-driving time between the acceleration pulse and the deceleration pulse sufficiently shorter than the natural resonance period of the tracking drive means is to prevent resonance of the natural resonance frequency of the tracking drive means. When the track jump is made by one revolution, the non-driving time between the acceleration pulse and the deceleration pulse is set to zero.

(Function) As mentioned above, when the track jump is made for multiple rounds, the time of the acceleration pulse and the deceleration pulse is suppressed and a non-driving time is left between the acceleration pulse and the deceleration pulse. As with the case where the light beam is stopped exactly on the target circumference, it does not go too far. Moreover, since the track jump is performed at once, the track jump can be made for multiple rounds in a short time.In the case of an optical video disc player, when the disc has a constant angular velocity, the track jump number N is large. Even if the position of the light beam after the track jump is shifted from the vertical retrace period, noise will not occur on the reproduced screen after the track jump.

(Embodiment) FIG. 1 shows a main part of an example of an optical disc player of the present invention.

In this example, a three-spot method (three-beam method) is used to detect tracking errors using two light beams other than the light beam for signal reading. A total of three light beams, one for signal reading and two for tracking error detection,
Two light beams for tracking error detection are incident on the disk at symmetrical positions with respect to the direction along the track and in the direction perpendicular to this, with the light beam for signal reading as the center. The amount of light is changed depending on the position relative to the pit and is reflected back to the optical head. Of the light beams, the light beam for signal reading is transmitted to four light receiving elements 11A, 11B, 11C arranged around one point.
The two light beams for tracking error detection reach the light receiving unit 11 consisting of the light receiving element 11D, and reach the other light receiving elements 12E and 12F, and the light receiving elements 11A,
Output signals A, B, C, and D are obtained from the light receiving elements 11B, 11C, and 11D according to the portions of the light beams for signal reading on the respective spots, and the light receiving element 1
2 for tracking error detection from 2E, 12F
Output signals E and F are obtained depending on the size of the spot created by the light beam of the book.

Then, the output signals E and F of the light receiving elements 12E and 12F are supplied to the plus side input terminal and the minus side input terminal of the subtraction circuit 13, respectively, and the subtraction circuit 13 outputs a signal E-F of the difference between the signal E and the signal F. Obtained as tracking error signal TE. In addition,
Although not shown, a signal represented by (A+B)-(C+D) is obtained as a focus error signal, and a signal represented by A+B+C+D is extracted as a reproduced signal.

The tracking error signal TE obtained from the subtraction circuit 13 is supplied to the drive circuit 14, and a drive voltage based on the tracking error signal TE is obtained from the drive circuit 14. When the switch 15 is turned on, the drive voltage is tracking drive means 1 for moving the focusing lens of the optical head or the entire optical head in the radial direction of the disk through a switch 15;
6, the tracking servo is turned on, and the light beam for signal reading is controlled so as to be positioned correctly on the track of the disk.

A power supply 18 with a positive voltage +V is connected to the tracking drive means 16 via a switch 17, and a negative voltage -V is connected via a switch 19.
V power supply 20 is connected, and the above-mentioned switch 15 is turned on.
It is controlled on/off by the output signal S1 of the RS flip-flop 21, and the switch S1
7 and 19 are controlled on and off by signals obtained from terminals 22 and 23, respectively. Terminals 22 and 23 are the output terminals of a switch 24 that distributes and takes out two input signals to two output terminals according to the switching state, and the switch 24 receives output signals S of monostable multivibrators 25 and 26 as input signals.
2, S3 is supplied.

On the other hand, the tracking error signal TE obtained from the subtraction circuit 13 is supplied to the voltage comparison circuit 27.
Tracking error signal from voltage comparison circuit 27
A rectangular wave signal ZC is obtained by detecting the zero cross point of TE, and this rectangular wave signal ZC is supplied to the clock terminal CK of the counter 28. When the data supplied to the preset terminal PR is preset and the start signal is supplied to the control terminal CT, the counter 28 counts down the pulses of the square wave signal ZC from the preset value, and counts the pulses by the preset value. When the count value becomes zero, a carry signal CA is obtained.

Then, by operating the track jump on the operation section 29, the number of track jumps N is output from the operation section 29.
Data ND indicating track jump start signal TS and signal indicating track jump direction
SW is obtained, data ND is supplied to the preset terminal PR of the counter 28, and the start signal TS is
The signal is supplied to the set terminal S of the RS flip-flop 21, the trigger terminal of the monostable multivibrator 25, and the control terminal CT of the counter 28.
SW is supplied to the switch 24 as its switching signal. Further, the carry signal CA obtained from the counter 28 is supplied to the trigger terminal of the monostable multivibrator 26, and the output signal S3 of the monostable multivibrator 26 is applied to the RS flip-flop 21.
is supplied to the reset terminal R of.

To explain the operation when a track jump is made by N tracks from the inner circumference to the outer circumference of the disk in the above-mentioned configuration, in this case, the counter 28
is preset to the track jump number N, and the signal SW is set to a high level, for example, so that the switch 24 outputs the output signal S2 of the monostable multivibrator 25 to the terminal 22, and outputs the output signal S3 of the monostable multivibrator 26 to the terminal 23. The state is switched to the state in which the state is derived.

Then, at a time t ₀ when the light beam for signal reading is on a certain circumference T(0) of the track, a start signal TS is obtained from the operating section 29, and the RS flip-flop 21 is set at the leading edge of the start signal TS. As shown in FIG. 2, the output signal S1 of the RS flip-flop ₂₁ becomes low level at time _t0 , and
The switch 15 is turned off and the tracking servo is turned off. At the same time, the monostable multivibrator 25 is triggered by the leading edge of the start signal TS, and the output signal S2 of the monostable multivibrator 25 becomes high level at time t ₀ , and the switch 17 is turned on at time t ₀ to drive tracking. The drive voltage DV to the means 16 becomes the voltage +V of the power supply 18, and an acceleration pulse is applied to the tracking drive means 16 from time _t0.
DP is supplied, and a light beam for signal reading is accelerated and moved from the inner circumference of the disk toward the outer circumference, as indicated by arrow 1 in FIG. 2, in accordance with the polarity of the acceleration pulse DP in the radial direction of the disk.

The time for the monostable multivibrator 25 to maintain the metastable state is determined by the time between the starting point T(0) and the next circumference T(1) when the light beam for signal reading is moved while being accelerated as described above. Time to reach the intermediate position, i.e. from time t ₀ to time t ₁ in Figure 2
is set equal to the time until. This time is
It takes about 100μ seconds. Therefore, when the light beam for signal reading reaches a position midway between the circumference T(0) and the circumference T(1) of the starting point at time _t1 , the output signal S2 of the monostable multivibrator 25 becomes low level, The switch 17 is turned off, the driving voltage DV becomes zero, and the moving speed of the light beam for signal reading is changed to the speed shown in Fig. 2.
As shown by SP and the position of the signal reading light beam on the track with respect to time is shown by line 2 in the figure, the signal reading light beam is moved in the same direction at a constant speed due to inertia from time _t1 . .

On the other hand, from the time _t0 when the start signal TS is obtained from the operation unit 29, the light beam for signal reading of the rectangular wave signal ZC obtained from the voltage comparator circuit 27 is detected at the counter 28, at the midpoint between one track lap and the next track. The falling edge indicating the point in time when the signal reading light beam passes through the position _of
-1) When the count value of the counter 28 becomes zero by reaching the intermediate position, a carry signal CA is obtained from the counter 28, and the monostable multivibrator 26 is triggered at the leading edge of the carry signal CA.
At t ₂ the output signal S of the monostable multivibrator 26
3 becomes high level, the switch 19 is turned on at time _t2 , the drive voltage DV to the tracking drive means 16 becomes the voltage -V of the power supply 20, and the deceleration pulse BP is applied to the tracking drive means 16 from time _t2 . The optical beam for reading the signal moves toward the target circumference T(N) while decelerating.

The time for the monostable multivibrator 26 to maintain the metastable state is determined by the time the light beam for reading the signal moves while decelerating as described above until it reaches the target circumference T(N).
2, that is, the time from time t ₂ to time t ₃ in FIG. This time is almost equal to the time of the aforementioned acceleration pulse DP. Therefore, when the signal reading light beam reaches the target circumference T(N) at time _t3 , the output signal S3 of the monostable multivibrator 26 becomes low level and the switch 19 is turned off. Then, at this time point _t3 , the moving speed of the light beam for signal reading becomes zero, and the light beam for signal reading does not go beyond the target circumference T(N). Simultaneously at time t ₃ the output signal S3 of the monostable multivibrator 26
RS flip-flop 21 is reset by the falling edge of RS flip-flop 21, and the output signal S1 of RS flip-flop 21 becomes high level, and switch 1 is turned off at time _t3 .
5 is turned on and the tracking servo is turned on.

Contrary to the above, if you want to jump the track by N tracks from the outer circumference to the inner circumference of the disk, the signal SW is set to a low level and switch 2 is turned on.
Contrary to the above, 4 is a monostable multivibrator 25
The output signal S2 of the monostable multivibrator 26 is output to the terminal 23, and the output signal S3 of the monostable multivibrator 26 is output to the terminal 22. Therefore, contrary to the above, the switch 19 is activated between time t ₀ and time t ₁ .
is turned on, the light beam for signal reading is accelerated and moved from the outer periphery to the inner periphery of the disk by an acceleration pulse of voltage -V, and switch 17 is turned on between time t ₂ and time t ₃ . being made into
The optical beam for reading the signal is decelerated by the deceleration pulse of voltage +V as it heads toward the target lap, and then tracks jumps to the target lap in the same manner as described above.

In the range where the track jump number N is up to several tens,
Acceleration pulse DP and deceleration pulse BP as mentioned above
The acceleration pulse
_The non-driving time _T
It is close to the natural resonance period of 6. Therefore, when making the track jump number N larger than several 10,
Either the track jump as described above is repeated several times in the range up to several 10, or as shown in Fig. 3, the end point of the acceleration pulse DP is set to the circumference T(0) from which the light beam for signal reading is the starting point. At this point, the starting point of the deceleration pulse BP is at the point where the light beam for signal reading reaches the position halfway between the lap T (M) several laps ahead and the next lap T (M+1), and the light beam for signal reading is from the target lap T (N). Lap T(N-M) several laps before this and Lap T(N
The acceleration pulse
It is sufficient to shorten the non-driving time T _X between DP and deceleration pulse BP.

(Effects of the Invention) According to the present invention, by suppressing the time of the acceleration pulse and the deceleration pulse and leaving a non-driving time between the acceleration pulse and the deceleration pulse, even when the track jump is made for multiple revolutions, the time of the acceleration pulse and the deceleration pulse is suppressed. As with a single track jump, the light beam will stop exactly on the target circumference and will not overshoot. Moreover, since the track jump is performed at once, the track jump can be performed for multiple rounds in a short period of time.In the case of an optical video disc player, when the disc has a constant angular velocity,
Even if the track jump number N is large, the arrival position of the light beam after the track jump will not deviate from the vertical retrace period and noise will not occur on the reproduced screen after the track jump.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing essential parts of an example of the optical disc player of the present invention, FIG. 2 is a diagram for explaining its operation, and FIG. 3 is a diagram for explaining the operation of another example. FIGS. 4 and 5 are diagrams for explaining the track jump according to the conventional method. In the figure, 12E and 12F are light receiving elements constituting a tracking error detection means, 16 is a tracking drive means, 15, 17 to 21 and 24 to 2.
8 is a circuit constituting the track jump means.

Claims (1)

[Scope of Claims] 1. Tracking error detection means for obtaining a tracking error signal representing the tracking state of a light beam for signal reading on the disk for reading the signal from a disk having a track on which the signal is recorded; Tracking drive means for moving the signal reading light beam in the radial direction of the disk in order to correctly position it on the track of the disk by being supplied with a drive voltage based on a king error signal; and a track jump. In response to the instruction, the supply of the drive voltage based on the tracking error signal to the tracking drive means is cut off, and a voltage of the first polarity is supplied to the tracking drive means as an acceleration pulse for a predetermined period of time, and the acceleration After the pulse is supplied, after a time sufficiently shorter than the natural resonance period of the tracking drive means, a voltage of a second polarity whose absolute value is approximately equal to the voltage of the first polarity is applied to the tracking drive means for approximately the predetermined time. Track jump means for causing the light beam for reading the signal on the disk to track jump in the radial direction of the disk by one or more turns of the track by supplying it as a deceleration pulse for an equal amount of time. An optical disc player consisting of