JPS6350977A - Information reproducing device with fast reproduction function - Google Patents

Abstract

PURPOSE:To obtain a reproducing image without noise during a scanning operation, by writing a prescribed amount of video information being obtained from a recording disk on a memory, after the lapse of a prescribed time when a loop open command disappears. CONSTITUTION:When a scan command is issued, an oscillator 18 is started up, and an oscillation output (f) goes to a low level with a cycle T3 only for a time T4, then, an open command is issued. At such a time, a monostable multivibrator 19 is triggered, and an inverted Q output (g) goes to the low level for a time T5. A write enable signal (i) is outputted from a write control circuit 14 synchronizing with a vertical synchronizing signal (h) outputted from a synchronizing signal separator 12. The signal (i) is continued to be outputted until the next signal (h) is outputted, and the video information of one field is written on the memory 13. Therefore, by setting the time T5 longer by a time DELTAT required for servo clock after the closure of a tracking servo loop than the time T4, a video signal without having the noise can be stored in the memory 13.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an information reproducing apparatus, and more particularly to an apparatus having a function of reproducing information recorded on a recording disk such as a video disk at high speed.

11 and as an information reproducing apparatus, an apparatus as shown in FIG. 7 has already been devised which has a function of reproducing recorded information on a recording disk at high speed while a scanning operation is being performed, that is, a command is being issued. In the figure, 1 is a photodetector. The photodetector 1 is housed in a pickup configured to detect tracking errors using a three-beam method.

The elements 1a and 1C of the photodetector 1 receive reflected light from a light spot formed by irradiating the recording disk with a sub-beam for tracking error detection. Each output of these elements 1a and 1c is supplied to a subtracter 2 to generate a tracking error signal b. Further, reflected light from a light spot (information detection point) formed by irradiating the recording disk with the main beam for information detection is incident on the element 1b of the photodetector 1. The output of this element 1b is supplied to the FM demodulator 3 to reproduce the video signal e.

The output of the subtracter 2 is supplied to an equalizer 5 via a loop switch 4. In the equalizer 5, phase compensation of the tracking error signal is performed. Equalizer 5
The output a is applied to the tracking actuator 6 as a drive signal to form a tracking servo loop. Further, the output a of this equalizer 5 is supplied to a window comparator 7 and a motor drive circuit 8.

The window comparator 7 is configured so that its output becomes high level when the absolute value of the level of the output of the equalizer 5 exceeds a predetermined value. The output C of the window comparator 7 serves as a trigger signal for a monostable multivibrator (hereinafter abbreviated as monostable multi) 9. The d output d of the monostable multi 9 serves as a control signal for on/off control of the loop switch 4. loop switch 4
is configured to turn off (open state) when this output d becomes a low level.

The output of the motor drive circuit 8 is supplied to a slider motor 10. The slider motor 10 is a motor that drives a slider (not shown) that is equipped with a pickup and is movable in the radial direction of the disk. The motor drive circuit 8 is
The displacement amount of the tracking actuator 6 is detected based on the output of the equalizer 5, and the slider motor 10 moves the pickup to a position in the radial direction of the disk so that the displacement amount is zero, that is, the position is located at the midpoint of the movable range of the tracking actuator 6. control.

Further, this motor drive circuit 8 is configured to move the slider in one of the outer and inner circumferential directions of the disk at a predetermined speed in response to a scan command.

The operation of each part in the above configuration will be explained with reference to FIG. FIG. 8 (A> is a waveform diagram of the output a of the equalizer 5, and FIG. 8 (B) is a waveform diagram of the tracking error signal S.
(C) is a waveform diagram of the output C of the window comparator 7, (D) is a waveform diagram of the output d of the monostable multi 9, and (E) is the waveform diagram of the output d of the monostable multi 9. FIG. 2 is a waveform diagram of a video signal e.

When a scan command is issued, the motor drive circuit 8 moves the slider, for example, toward the outer circumference of the disk. Then, the level of the output a of the equalizer 5, which is supplied as a drive signal to the tracking actuator 6, gradually increases with a slope corresponding to the moving speed of the slider. In this case, the amount of displacement of the tracking actuator 6 becomes large. However, when the absolute value of the output a of the equalizer 5 reaches a predetermined value, the output C of the window comparator 7 becomes high level. Then, the monostable multi 9 is triggered and the Φ output d remains at a low level for a time T1 corresponding to the time constant of the monostable multi 9. As a result, the loop switch 4 remains off for a period of time T1, and the tracking servo loop becomes open. Then, the position of the tracking actuator 6 returns to the midpoint of the movable range, and the information detection light spot of the pickup moves across the recording track.

After the inversion operation of the monostable multi 9 is completed, the loop switch 4
When turned on, the tracking servo loop is closed, so that the information detection optical spot of the pickup is positioned on the recording track, and information reading begins.

Although high-speed reproduction is achieved by the above-described operation, noise is generated in the video signal e outputted from the FM demodulator 3 because the information indicating the amount that the loop switch 4 is turned off cannot be properly read.

Therefore, in order to reduce the influence of noise, the reference level in the window comparator 7, for example, has been set so that the period T2 in which the tracking servo loop is opened is sufficiently long.

However, in doing so, it became necessary to expand the movable range of the actuator and the field of view of the pickup.

Furthermore, when the tracking servo loop becomes open, the number of tracks over which the information detection light spot of the pickup jumps increases, making it difficult to maintain the continuity of reproduced images and finding a desired image.

An object of the present invention is to provide an information reproducing device that can obtain stable reproduced images without noise during a scanning operation.

The information reproducing device according to the present invention generates a loop open command at a predetermined period, opens a tracking servo loop by the loop open command, and generates a predetermined amount of video obtained from a recording disk after a predetermined time has elapsed from the time when the loop open command disappears. The configuration is such that information is written to the memory and the video information written to the memory is repeatedly read out.

Embodiments of the present invention will now be described in detail with reference to FIGS. 1 to 6.

In FIG. 1, element 1a of photodetector 1.

1b, 1c, subtractor 2. FM demodulator 3. Loop switch 4. Equalizer 5. The tracking actuator 6, motor drive circuit 8 and slider motor 10 are connected in the same way as in the device shown in FIG. However, in this example, the video signal output from the FM demodulator 3 is
(analog/digital) converter 11 and sync separator 1
2 is supplied. In the A/D converter 11, the video signal is sampled at a predetermined period, and the obtained sample values are converted into digital data.

The output data of this A/D converter 11 is supplied to a memory 13. The memory 13 is supplied with the outputs of a write control circuit 14 and a read control circuit 15 that perform mode control and address control. The write control circuit 14 is supplied with vertical and horizontal synchronization signals separated from the video signal by a synchronization separator 12.

In response to a write command, the write control circuit 14 simultaneously outputs a write enable signal i over a period from the generation of the vertical synchronization signal supplied after the generation of the write command to the generation of the next vertical synchronization signal. It is configured to output address data that changes sequentially at a predetermined period. The output data of the write control circuit 14 may be generated by, for example, a counter that counts up by a clock of a predetermined frequency and is reset by a horizontal synchronizing signal, and a counter that counts up by a horizontal synchronizing signal and is reset by a vertical synchronizing signal. Can be done. Data including video information for one field is written into the memory 13 by the write control circuit 14. Further, the read control circuit 15 is supplied with vertical and horizontal synchronization signals generated by a synchronization signal generation circuit 16. The read control circuit 16 is configured to generate address data that changes in synchronization with the supplied vertical and horizontal synchronization signals. The output data of the read control circuit 15 can be generated in the same manner as the output data of the write control circuit 14, for example. The read control circuit 15 sequentially reads data containing video information for one field written in the memory 13 in predetermined bits and supplies it to the D/A converter 17. In the 0/A converter 17, the data read from the memory 13 is converted into an analog signal and the video signal k is reproduced.

Further, the loop switch 4 is supplied with the output of an oscillator 18, which acts as a command generating means, as a control signal.

The oscillation output f of this oscillator 18 serves as a trigger input to the monostable multi 19. A high-level write command signal is supplied to the write control circuit 13 from the 0 output terminal of the monostable multifunction device 19 .

The operation of each part in the above configuration will be explained with reference to FIG. 2. FIG. 2(A) is a waveform diagram of the output a of the equalizer 5, and FIG. 2(B) is a waveform diagram of the tracking error signal S.
(C) is a waveform diagram of the oscillation output f of the oscillator 18, (D) is a waveform diagram of the 0 output q of the monostable multi 19, and (E) is the waveform diagram of the 0 output q of the monostable multi 19. (F) is a waveform diagram of the vertical synchronizing signal output from the sync separator 12. (G) is a waveform diagram of the write enable signal i. H) is a waveform diagram of the vertical synchronization signal j output from the synchronization signal generation circuit 16;
1) is a waveform diagram of a video signal output from the D/A converter 17.

When a scan command is issued, the slider is moved, for example, toward the outer circumference of the disk by the motor drive circuit 8 in the same manner as in the apparatus shown in FIG. Then, the level of the output a of the equalizer 5, which is supplied as a drive signal to the tracking actuator 6, gradually increases with a slope corresponding to the moving speed of the slider. In this case, the amount of displacement of the tracking actuator 6 becomes large. At the same time, the oscillation operation of the oscillator 18 is started, the oscillation output f becomes a low level for 14 hours with a period T3, and a loop open command is issued. This loop open command turns the loop switch 4 off for a period of time T4, and the tracking servo loop becomes open. Then, the position of the tracking actuator 6 returns to the midpoint of the movable range, and the information detection light spot of the pickup moves across the recording track.

When the oscillation output f reaches a high level, the loop switch 4 is turned on, the tracking servo loop is closed, and information starts to be read normally.

Further, when the oscillation output f becomes a low level, the monostable multi 19 is triggered, and the d output q remains at a low level for a time T5 corresponding to the time constant of the monostable multi 19. When this O output q becomes high level, the write control circuit 14 is activated in synchronization with the first vertical synchronization signal output from the synchronization separator 12.
A write enable signal 1 is output from. This write enable signal i is output until the next vertical synchronization signal is output. This write enable signal 1 causes data including video information for one field to be written into the memory 13.

Therefore, if time T5 is made longer than time T4 by T, which is the time required for servo lock after the tracking servo loop is closed, noise-free video information can be stored in the memory 13. Become. The data written in the memory 13 is read out by the address data generated by the vertical synchronizing signal j from the synchronizing signal generating circuit 16, and the D/A converter 17 outputs a noise-free video signal k.

FIG. 3 is a block diagram showing another embodiment of the present invention, showing elements 1a and 1b of the photodetector 1.

1c, subtractor 2. FM demodulator 3. Loop switch 4, equalizer 5. Tracking actuator 6, motor drive circuit 8. Slider motor 10. A/D converter 11. The synchronous separator 129 oscillator 18 and monostable multi 19 are the first
Connected in the same way as the device shown in the figure. However, in this example, the horizontal synchronization signal H output from the synchronization separator 12 is supplied to the phase comparator 22, and the phase difference with a reference signal, which will be described later, is detected. The phase difference signal output from the phase comparator 22 is supplied to a time axis servo circuit 23, and is used, for example, to control the rotational speed of a spindle motor that rotationally drives a recording disk, and to control the drive of an actuator in a so-called tangential servo system. .

30 is a reference oscillator of VCO<voltage controlled oscillator) configuration, and has a horizontal scanning frequency f+-+ (fH=15°734K)
f-1z) times N times (N is an integer greater than or equal to 2, N=mx
A reference clock p having a frequency of n) is generated.

This reference clock p is frequency-divided by 1/m (m is an integer of 2 or more) by a frequency division counter 31 to become a clock q. This frequency-divided clock q is selectively supplied to a frequency-divided counter 33 by a switch 32 serving as a gate means.
3 and further divided into 1/n (n is an integer of 2 or more), resulting in a clock t having a horizontal scanning frequency fH. This frequency-divided clock t becomes the reference signal of the phase comparator 22 mentioned above, that is, the time axis M standard of the time axis servo system.

The switch 32 is closed (on) during normal playback of information recorded on the disc, and remains open (off) for at least the jump period when a track jump operation is performed by special playback, and switches the frequency division clock q to the frequency division counter 33. The opening/closing is controlled by the control circuit 34 so as to supply the same. The control circuit 34 includes a monostable multivibrator 35 that is triggered by the falling edge of the output of the oscillator 17 and generates a single pulse of a predetermined pulse width, and a monostable multivibrator 35 that uses this single pulse as data (D>input) and performs synchronous separation. from device 12 to inverter 3
The horizontal synchronization signal H supplied via the clock (CK
), and the Q output of this D-flip 70 tube 37 is used as a control signal for the switch 32.

The reference pulse p generated from the reference oscillator 30 serves as the time axis reference for the servo system as described above, and also serves as the clock for A/D and D/A conversion of the video signal from the FM demodulator 3. The signal is supplied to the converter 11 and the D/A converter 39. Furthermore, the frequency is divided by 1/m by the frequency division counter 31, and the S→P register 41 and the write control circuit 42 are used as the clock q for writing and reading the memory 40.
Furthermore, it is supplied to a P-+S register 44 and a read control circuit 45 via an inverter 43. These write control circuit 42 and read control circuit 45 are constructed similarly to the write control circuit 14 and read control circuit 15 in the device shown in FIG. For example, by W/R clock q,
During the high level period, writing is performed by transferring the output of the register 41, which converts the serial data from the A/D converter 11 into m samples of parallel data, to the memory 40 at once, and vice versa, during the low level period. m samples of data are read from the memory 40 and stored in the register 4.
4 is performed.

As is clear from the above, since the time-domain servo is performed based on the time-domain reference pulse t obtained by frequency-dividing the reference pulse p generated from the reference oscillator 30, the video signal e
is synchronized with the time axis reference pulse t, which is the output of the frequency division counter 33, at a predetermined phase. This means that the reference oscillator 3
This means that the reference pulse p generated from 0 and the W/R clock q which is the output of the frequency division counter 31 are also synchronized with a predetermined phase.

Therefore, the time axis reference pulse and the video signal e are used as the horizontal and vertical reset pulses of the write control circuit 42.
By using the vertical synchronization pulses separated by the synchronization separator 12 and resetting the counter 42 with these pulses, the image plane and the memory plane are written in a 1:1 and predetermined relationship. Become.

Although it is possible to use the horizontal synchronization pulse separated from the video signal e by the synchronization separator 12 as the horizontal reset pulse for the write control circuit 42, it is possible that the time axis A slight phase shift will occur between the reference pulse t and the video signal e. The relationship between the W/R clock q and the time axis reference pulse t is determined by the frequency division counter 33 and has no uncertainty, but the absolute phase relationship between the video signal e and the W/R clock q is determined by the time axis reference pulse t. Since it is determined indirectly by the axis servo system, when the write control circuit 42 is reset by the horizontal synchronization pulse obtained from the video signal e, the W/R
It is not necessarily reset at the completion of the operating cycle;
This will cause inconvenience.

Therefore, by using the time axis reference pulse t as the horizontal reset pulse of the write control circuit 42, the W/R
This is preferable because the absolute phase with the clock q is maintained and it is not affected by noise contained in the reproduced signal.

On the other hand, on the read side, as described above, video data is read from the memory 40 during the low level period of the W/R clock q, and is converted back into an analog video signal by the D/A converter 39. The read control circuit 45, which determines the address of data read from the memory 40, uses the same W/R clock q as the write control circuit 42 to count, but its horizontal reset pulse uses the W/R clock q.
The frequency division pulse r obtained by dividing the clock q by 1/n by the frequency division counter 46 is used, and the 910f+ output from the oscillator 47 is used as the vertical reset pulse.
A vertical synchronization pulse separated by a vertical synchronization separation circuit 49 from a composite synchronization signal @S generated by a synchronization signal generator 48 based on a frequency signal of is used.

The horizontal synchronization pulse included in the composite synchronization signal S is separated by a horizontal synchronization separation circuit 50, and is supplied to a phase comparator 51, where the phase is compared with the frequency division pulse r from the frequency division counter 46. The phase comparator 51 controls the oscillation frequency of the reference oscillator 30 according to the phase difference between the two pulses, thereby making the horizontal reset pulse of the readout control circuit 45 match the phase of the composite synchronization signal S.

Therefore, the horizontal and vertical reset pulses of the read control circuit 45 are independent of the synchronization signal in the video signal e read from the recording disk, and the constant and continuous composite synchronization signal S
determined by.

At the time of writing, the image plane and the memory plane are kept in a 1:1 and predetermined relationship as described above, so if the data on the memory plane is sequentially read out by the read control circuit 45, continuous data can be written. This will allow you to obtain images.

The above is a description of the normal reproduction (so-called play) state, and the signal waveforms of each part at this time are shown in FIG. FIG. 4(A) is a waveform diagram of the reference clock p,
(B) is a waveform diagram of the divided clock q, (C) is a waveform diagram of the divided pulse r, (D) is a waveform diagram of the composite synchronization signal S, and (E ) is a waveform diagram of the time-axis reference pulse t, (F) is a waveform diagram of the video signal e, and (G) is a waveform diagram of the video signal e.
) is a waveform diagram of a video signal. In addition, Fig. 5 (A
) to (C) of the same figure respectively show a reproduced image plane, a memory plane, and an image plane of memory output based on the video signal output from the FM demodulator 3.

Next, during the scanning operation, when the oscillation output f becomes low level as shown in FIG. 6(A), similar to the device shown in FIG.
The monostable multi 35 is triggered and a negative polarity pulse with a predetermined pulse width is supplied to the D-flip-flop 37 . Then, the Q output port of the D-flip 70 knob 37 is at a low level for a time T6 corresponding to the pulse width of the negative polarity pulse, as shown in FIG. 6(B), and the switch 32 is turned off. Then, the operation of the time axis servo is stopped in synchronization with the horizontal synchronization signal from the synchronization separator 12, and writing to the memory 13 is prohibited.

Here, the time T6 when the Q output port becomes low level, the time T4 when the oscillation output f becomes low level, and the time T5 when the 0 output Q of the monostable multi 19 as shown in FIG. 6(C) becomes low level.
It should be somewhere in between.

Then, the Q output port goes to a high level and the time-domain servo starts operating after the tracking servo loop is closed and some time has elapsed, so the time-domain servo converges almost instantly. ◇The output Q becomes high level and a write command is supplied to the write control circuit 42 after the time axis servo converges. Therefore, data containing one field's worth of video information without any time axis error and noise is written in the memory 40, similar to the device shown in FIG. You will get a stable video signal.

Incidentally, the frequency division value m of the frequency division counter 31 represents the number of samples of one block for serial-to-parallel conversion of quantized data, and is usually appropriately set to 4 or 8. Also,
The product of this frequency division value m and the frequency division value n of the counter 33 determines the sampling frequency of the video signal, but in optical video discs, the video low frequency range is about 4.2 MHz, so the sampling frequency is From the theorem, 2X4.2MH
A frequency of z = 8.4 MHz or higher is required. On the other hand, if the sampling frequency is selected too high, the memory capacity required to record one field or one frame of video will increase, so from this point of view, a lower sampling frequency is preferable. Therefore, as an efficient sampling frequency, 8, 81 to 9.31 M) (Z), which is the value when m=3 and n=70 to 74, is appropriate.

At the subsequent stage of the D/A converter 39, a composite synchronizing signal S is added to the video signal (G) read from the memory 4° in an adder 53, but this saves the capacity of the memory 40. Therefore, the horizontal synchronization and vertical synchronization parts of the video signal are not recorded in the memory 40. memory 40
In the video signal (G) read from
2 occurs, and as a result, the continuity of the burst phase of the video signal is lost and there are cases where it is reversed. This will disrupt the color synchronization of the TV screen, but in order to prevent this, the burst continuity determining circuit 54 determines the burst continuity and
The continuity of the burst phase is maintained by selecting the input or output of the delay line 55 using the selection switch 56.

When the memory capacity is one field, the fields may be swapped between the writing side and the reading side. This is provided to control the vertical start position of the readout control circuit 45 so that the vertical start position of the readout control circuit 45 does not occur.

In the above embodiment, it is assumed that one field's worth of video information is written in the memory 13.40, but the memory 13.40 has video information corresponding to one part of the screen, such as one horizontal scanning line. Only the amount of video information may be written.

As described in detail above, the information reading and reproducing device according to the present invention generates a loop open command at a predetermined period, opens the tracking servo loop by this loop open command, and waits for a predetermined period of time from the disappearance of the loop open command. Since the configuration is such that a predetermined amount of video information obtained from the recording disk is written to the memory after the elapse of time, and the video information written to the memory is repeatedly read out, scanning operations can be performed regardless of whether the disk is a CAM disk or a CLV disk. A reproduced image free of noise and synchronization disturbance can be obtained.

Therefore, according to the present invention, there is no need to lengthen the period T3 in which the tracking servo loop is opened due to noise or synchronization disturbance, and even if T3 is shortened to about 50m5, at least one period is stored in the memory. A video signal for one field can be written and a good reproduced image can be obtained. This eliminates the need to expand the tracking actuator's movable range or the optical system's field of view just for scanning operations.
Cost reduction and quality improvement can be expected. Furthermore, since the number of track skips is reduced when the tracking servo loop is opened, continuity of images during scanning can be maintained, a desired image can be easily found, and operability is improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a waveform diagram showing the operation of each part of the device in FIG. 1, and FIG. 3 is a block diagram showing another embodiment of the present invention. 4 is a waveform diagram showing the operation of each part of the device in FIG. 3, FIG. 5 is a diagram showing the positional relationship of each data in the image plane and the memory plane, and FIG. 6 is a waveform diagram showing the operation of each part of the device in FIG. 3. FIG. 7 is a waveform diagram showing the operation of each part during the scanning operation of the apparatus. FIG. 7 is a block diagram showing a conventional information reproducing apparatus. FIG. 8 is a waveform diagram showing the operation of each part of the apparatus of FIG. Explanation of symbols of main parts 4...Loop switch 13.40...Memory 14.42...Write control circuit 15.45...
... Readout control circuit 18 ... Oscillator 19 ... Monostable multi

Claims (1)

[Claims] A tracking servo loop that controls the position of the information detection point of the pickup in the radial direction of the recording disk is opened, and at the same time the information detection point is moved across tracks, and the tracking servo loop is closed. An information reproducing device configured to perform high-speed reproduction by alternately performing reading operations for reading information on a recording disk, the information reproducing device comprising a memory, a command generating means for issuing a loop open command at a predetermined period, and a command generating means for issuing a loop open command at a predetermined period. loop open means for opening the tracking servo loop in response to the loop open command; write control means for writing a predetermined amount of video information obtained from the recording disk into the memory after a predetermined time has elapsed since the loop open command disappeared; 1. An information playback device having a high-speed playback function, comprising readout control means for repeatedly reading out video information written in a memory.