JPS627631B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a feed pulse generation circuit, which generates a feed pulse based on the zero-crossing point of a tracking error signal, thereby stably tracking the reproducing element even when the feed speed is high. The object of the present invention is to provide a feed pulse generation circuit that can generate feed pulses.

The present applicant has previously proposed, in Japanese Patent Application No. 52-25260 and others, that the main information signal and the first to third tracking control reference signals (hereinafter referred to as tracking signals) are each geometrically shaped without forming a needle guide groove. The main information signal and the first to third tracking signals are captured by electrostatic capacitance by a disc-shaped information recording medium having an electrode function recorded as a change in shape, and relative sliding scanning of the medium with a reproducing needle having an electrode. We proposed a playback device that reads and plays as a variation of the above. In addition, in the disc-shaped information recording medium proposed by the applicant mentioned above, a video signal, etc. is recorded as the main information signal in four fields per revolution on a spiral main track, and the recording frequency band of the main information signal is The first and second tracking signals f _p1 and f _p2 having different frequencies lower than that of A sub-track is formed in the middle between the main tracks adjacent to each other in a burst pattern, and is further recorded at the switching connection part of f _p1 and f _p2 (within the vertical blanking period).
, a third tracking signal f _p3 is used to switch the tracking polarity of the tracking servo circuit.
is recorded at a level below a predetermined level so as not to affect the main information signal.

FIG. 1 is a diagram schematically showing the recording arrangement relationship of recording tracking signals on this disc-shaped information recording medium.
In the figure, the ◯ mark indicates the f _p1 (or f _p2 ) recording position, the Δ mark indicates the f _p2 (or f _p1 ) recording position, and the solid line indicates the track center line of the main track. Further, the third tracking signal f _p3 is recorded at the position indicated by the broken line in FIG.

This disc-shaped information recording medium (hereinafter referred to as "disk") proposed by the present applicant does not have a needle guide groove, so it is possible to perform various types of special playback. It is necessary to change the speed at which the regenerating needle is transported in the radial direction of the disk (ie, the feed speed) depending on the speed. For example, when playing back a disc on which an NTSC color video signal is recorded as the main information signal in 4 fields per revolution of the disc and is rotated at 900 rpm, during normal playback, 1 field will be recorded every 32 tracks (every 2.1 seconds). A feed pulse is generated and applied to the feed feed DC motor to feed the regenerating needle, and the regenerating needle is always moved one track pitch at a predetermined location on the disk so that the same track is regenerated during stay motion regeneration. The feed is forcibly transferred (this is called "kick"), but the feed speed during this stay motion reproduction is zero.

However, in the disc playback device proposed by the present applicant, the feed feeding mechanism for transporting the playback needle is configured to move the playback needle using a DC motor, and therefore the transfer speed is controlled by the DC motor. This can be done by controlling the rotational speed of the DC motor by changing the period and pulse width of the feed pulse applied to the DC motor. During normal playback (normal playback, slow motion playback, quick motion playback, etc.), the error caused by the movement of the tip of the playback needle due to feed feed changes to the DC component of the tracking error signal. In order to correct this feed feeding error, the pulse width of the feed pulse is varied in accordance with the DC component of the tracking error signal. It is clear that the rotation speed of a DC motor increases in proportion to the pulse width if the repetition frequency of the applied feed pulses is the same.

By the way, the tracking error signal is 900rpm.
A 15Hz signal is superimposed due to the eccentricity of the rotating disk, etc., and in order to accurately correct the feed advance error, it is necessary to remove this 15Hz signal component. For this reason, the feed pulse generation circuit in the disc playback device proposed earlier by the applicant removes the 15Hz signal component by passing the tracking error signal through a CR low-pass filter, and then modulates the pulse width of the feed pulse. Was. However, in the feed pulse generation circuit proposed by the applicant, when the eccentricity of the disk increases, the 15 Hz signal component also increases accordingly, and may not be sufficiently removed by the low-pass filter. Also, due to the time delay caused by the low-pass filter, tracking error information is not accurately transmitted as feed error information, especially when the tracking error information is transmitted 64 times per disk rotation.
During fast motion playback, which causes the playback needle to become stiff, it is necessary to generate two feed pulses per disk rotation.If such fast motion playback is continued for a long time, the feed pulses will be affected due to the time delay caused by the low-pass filter. There was a problem in that the errors accumulated and became large, and the feed feed of the reproducing needle could no longer follow the tracking deviation correction operation of the reproducing needle, resulting in tracking failure.

The present invention solves the above-mentioned problems, and one embodiment thereof will be explained with reference to the drawings from FIG. 2 onwards.

FIG. 2 shows a circuit diagram of an embodiment of the main part of the feed pulse generating circuit according to the present invention. In the figure, 1 is a tracking error signal input terminal, and when a disc having the tracking pattern shown in the first figure is reproduced, a tracking error signal corresponding to the relative level difference between the reproduced tracking signals f _p1 and f _p2 is generated. Supplied. This tracking error signal is shown in Figure 3A.
The waveform has a waveform as shown in , and as mentioned above, the waveform has a frequency component such as 15 Hz superimposed on the DC component representing the feed feed error caused by the movement of the tip of the reproducing needle. The DC component of this tracking error signal is periodic as shown in Fig. 2A, and its period T is 32 track playback periods (2.1 seconds during normal playback), and at each period T, the feed is The tracking error becomes zero. FIG. 3B shows the waveform of the tracking error signal, which is an enlarged view of the part surrounded by the broken line in FIG.
A 15Hz frequency component and a horizontal scanning frequency of 15.753kHz are superimposed on the DC component.

The above-mentioned tracking error signal is divided into three branches as shown in Fig. 2, one is applied to the switch circuit ₂ via the resistor _R1 , and the other _is applied to the horizontal The scanning frequency component is removed and applied to the waveform shaping circuit 3, and the last one is applied to the terminal b of the switch circuit ₆ via the resistor R3.

Here, the value of the resistor R ₁ is smaller than the value of R ₃ , and during the closing period of the switch circuit 2, the resistor R ₁
The tracking error signal that has passed through is sent to the switch circuit 6.
is applied to terminal b of . For example, the output signal of the waveform shaping circuit 3 composed of an amplifier with gain is
This rectangular wave is a 15 Hz rectangular wave as shown by the solid line in Figure C. This rectangular wave is supplied to the sample pulse generator 4, where it is differentiated and then waveform-shaped and converted into a 30 Hz sample pulse as shown in Figure 3 D. be done. This sample pulse is supplied to the switch circuit 2, which closes the switch circuit 2 during its high level period, that is, the zero crossing of the 15 Hz frequency component in the input tracking error signal and a short period before and after the zero crossing, and tracks the tracking error signal. Sample the zero crossing point of .

On the other hand, when the sample pulse is generated, the level detector 5 outputs a switching signal that connects the switch circuit 6 to the terminal a side. The signal is applied to the capacitor C ₂ via the circuit 6 and held, and is output from the output terminal 7. Since this output signal is a direct current component of the tracking error signal indicating the center of the displacement width of the tip of the reproducing needle, extracted at two points per one rotation of the disk, it accurately represents the feed feed error. In addition, since this output signal has no time delay caused by a low-pass filter in principle, it is possible to generate a feed pulse twice per disk rotation, especially during first-motion playback, where the playback needle is scratched a total of 64 times per disk rotation. If this occurs,
Alternatively, even when the eccentricity is large, the feed error can be accurately transmitted.

The output signal taken out from the output terminal 7 is
The signal is converted into a feed pulse by the circuit previously proposed by the applicant as shown in the figure, and then used as a drive signal necessary for driving the feed feed DC motor to drive the feed feed DC motor.
That is, the above output signal passes through a non-inverting amplifier 8 and is then sent to a switching field effect transistor (FET).
Applied to the drains of 11F and 11B. this
Only one of the FETs 11F and 11B is turned on depending on the feed direction by control signals from input terminals 9 and 10. For example, when the regenerating needle is transferred from the outer circumferential side to the inner circumferential side of the disk, the FET 11F is turned on.

The error signal taken out from FET 11F or 11B passes through the inverting amplifier 12 to the pulse width modulator 1.
It is applied to the terminal No. 3, and its output pulse width is varied. This pulse width modulator 13 is triggered by a pulse from an input terminal 14 applied to its trigger terminal. During normal playback (normal playback, fast motion playback, slow motion playback, etc.), the pulses that enter this input terminal 14 are generated once every 32 tracks on the disk are played back. , Therefore, one pulse is taken out to the output terminal of the pulse width modulator 13 every 32 track reproduction, and the pulse width is long enough to correct the feed feed error according to the error signal from the inverting amplifier 12. The pulse that is varied is output as a feed pulse.

Feed pulses taken out from the pulse width modulator 13 and having a pulse width that accurately matches the inclination of the needle tip are applied to the terminals of the analog switch circuit 16, respectively. During normal playback, the analog switch circuit 16 receives the signal from the input terminal 14.
One incoming pulse is applied to the terminal every time 32 tracks are reproduced, and a high level signal, for example, applied to the terminal from the input terminal 15 allows the input feed pulse to pass through and output as it is to the output terminal. This feed pulse is applied to the drains of switching FETs 18F and 18B via an amplifier 17, respectively. FET18F, 18B
As with FET11F and 11B, only one of them is turned on depending on the feed feeding direction, and the feed pulse is turned on.
The signal is supplied to the amplifier 19 via FET 18F or 18B.

The feed pulse taken out from the amplifier 19 is subjected to inversion amplification or non-inversion amplification depending on the feed feeding direction, and is amplified by transistors 20 and 21.
The current is applied to a feed feeding DC motor (not shown) from the output terminal 22 through a drive circuit consisting of the following: For example, when transferring the reproducing needle from the outer circumference side to the inner circumference side of the disk, the DC motor is rotated in the forward rotation direction. On the other hand, when transferring the regenerating needle from the inner circumferential side to the outer circumferential side, the DC motor is rotated in the reverse direction.

In this way, according to the present embodiment, during normal reproduction, feed feed errors can be corrected and stable feed control can be performed.

Incidentally, the amplitude of the 15 Hz frequency component superimposed on the tracking error signal changes depending on the eccentricity of the disk, but in this embodiment, when the eccentricity is small, the output signal waveform of the waveform shaping circuit 3 changes to the third waveform. The waveform becomes rounded as shown by the broken line in Figure C, and as a result,
The peak value of the sample pulse output from the sample pulse generator 4 is smaller than the value required to close the switch circuit 2. At this time, the output of level detector 5 causes switch 6 to connect terminal b and capacitor _C2.
is switched to connect the non-grounded side of the Therefore, in this case, the tracking error signal input to the input terminal 1 is outputted from the output terminal 7 after the 15 Hz frequency component is removed by a low-pass filter consisting of a resistor R ₃ and a capacitor C ₂ as in the conventional case. As a result, it is possible to prevent malfunctions due to noise in the tracking error signal when eccentricity is small.

The above embodiment has been described with reference to a case in which it is applied to a feed pulse for feeding a reproducing needle that reproduces a disc having a track pattern as shown in FIG. 1, which was proposed earlier by the present applicant. It can also be used as a feed pulse for moving an optical pick-up playback element in a device that carries out a recording process in the radial direction of the disk.

As described above, the feed pulse generation circuit according to the present invention uses, as the feed pulse, a pulse whose pulse width is varied according to the signal level obtained by sampling the zero-crossing point of the tracking error signal of the reproducing element. Since the DC component of the tracking error signal representing the feed error is generated, even when the disk has a large eccentricity, or especially during first motion playback where two feed pulses are output for one rotation of the disk, the DC component of the tracking error signal representing the feed error is For example, since the data is sampled at two locations per one rotation of the disk, accurate feed error correction can be performed, and therefore, stable feed feed control of the reproducing element without tracking deviation can be performed.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing the recording arrangement of a reference signal for tracking control in a disk-shaped information recording medium, which was previously proposed by the present applicant, and FIG. 2 shows an embodiment of the main part of the circuit of the present invention. Block system diagram, Figure 3 A-D
are signal waveform diagrams for explaining the operation of FIG. 2, and FIG. 4 is a circuit diagram previously proposed by the applicant showing other essential parts of the circuit of the present invention. 1...Tracking error signal input terminal, 2, 6
...Switch circuit, 3...Waveform shaping circuit, 4...
Sample pulse generator, 7... Output terminal, 13...
...Pulse width modulator, 16...Analog switch circuit, 22...Feed feed signal output terminal.

Claims (1)

[Claims] 1 Feed pulses of a predetermined repetition frequency are applied to a motor for moving a reproducing element that picks up and reproduces recorded signals on a disc-shaped information recording medium in the radial direction of the recording medium, and drive and control the rotation speed and direction of the reproducing element. In the generating circuit, the pulse width of the feed pulse of the predetermined repetition frequency is varied in accordance with the signal level obtained by sampling the zero-crossing point of the tracking error signal of the reproducing element, and the pulse is generated as the feed pulse. A feed pulse generation circuit featuring: