JPS631668B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a feed pulse generation circuit that periodically detects a DC component in a tracking error signal,
If the detected value continues to be equal to or higher than a predetermined value several times, the pulse width of the feed pulse applied to the feed motor for transporting the reproducing element is gradually increased, so that the reproducing element can be stably tracked using a simple circuit configuration. It is an object of the present invention to provide a feed pulse generating circuit that can perform feed feeding.

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 geometrically controlled without forming a needle guide groove. The main information signal and the first to third tracking signals are statically recorded by a disk-shaped information recording medium having an electrode function recorded as a change in the physical shape, and relative sliding scanning of the disk-shaped information recording medium with a reproducing needle having an electrode. We proposed a playback device that reads and plays back the changes in capacitance.

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. Forced transfer (this is called ``kitsuku'')
), 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.

FIG. 1 shows a circuit diagram of an example of a feed pulse generation circuit previously proposed by the applicant. In the same figure, an input terminal 1 is used to distinguish and separate first and second tracking signals _p1 and _p2 during reproduction of the disc;
After detecting them, a tracking error signal with a level corresponding to the relative level difference between the two (that is, a level corresponding to the amount of track deviation) and a polarity corresponding to the direction of the track deviation is input to the differential amplifier. 2. The tracking error signal taken out from the non-inverting amplifier 2 is sent to the amplifier 6 via a switching FET 5F or 5B, only one of which is turned on depending on the feed direction by control signals from input terminals 3 and 4. pulse width modulator 7 after being supplied and amplified here.
The output pulse width is varied.

This pulse width modulator 7 is triggered by a pulse from the input terminal 8 applied to its trigger terminal, but this trigger pulse is applied during normal playback (during normal playback, first motion playback,
During slow motion playback, for example, one pulse is generated every time 32 tracks on the disk are played back. Therefore, one pulse is extracted from the output terminal of the pulse width modulator 7 during 32-track reproduction, and the pulse width is set to a length that corrects the feed error in accordance with the tracking error signal from the amplifier 6. The variable pulse is output as a feed pulse.

The feed pulses taken out from the pulse width modulator 7 and having a pulse width that accurately matches the inclination of the needle tip are applied to the terminals of the analog switch circuit 10, respectively. During normal playback, the analog switch circuit 10 outputs 32 inputs from the input terminal 8.
One incoming pulse is applied to the terminal each time a track is reproduced, and a high level signal, for example, applied to the terminal from the input terminal 9 allows the input feed pulse to pass through to the output terminal as it is. This feed pulse is applied to each drain of the switching FETs 12F and 12B via the amplifier 11. FET12F and FET12B, like FET5F and FET5B, respectively, are turned on depending on the feed direction, and the feed pulse is turned on FET1.
It is supplied to the amplifier 13 via 2F or 12B.

The feed pulse taken out from the amplifier 13 is subjected to inversion amplification or non-inversion amplification depending on the feed feeding direction, and is amplified by transistors 14 and 15.
The current is applied to a feed feeding DC motor (not shown) from the output terminal 16 through a drive circuit consisting of the following: For example, in order to transfer the reproducing needle from the outer circumferential side to the inner circumferential 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, during normal playback, feed feed errors can be corrected and stable feed control can be performed.

However, as can be seen from FIG. 1, the feed pulse generation circuit proposed by the present applicant has a problem in that it has a large number of parts and is expensive.

The present invention solves the above problems,
An embodiment thereof will be described below with reference to FIG.

FIG. 2 shows a circuit system diagram of an embodiment of the main part of the feed pulse generating circuit according to the present invention. In the same figure,
The same parts as in FIG. 1 are given the same reference numerals. The input terminal 1 is connected to the inverting input terminal of the operational amplifier 17 via a low-pass filter having an extremely low cutoff frequency and consisting of a resistor R ₁ and a capacitor C ₁ . The operational amplifier 17 has a non-inverting input terminal grounded via a resistor R ₂ and a feedback resistor R ₃ , and an output terminal grounded via a diode D. connected to an input port. The operational amplifier 17 and the like constitute a comparator. The output ports 19 of the microcomputer 18 are respectively connected to, for example, terminals of the analog switch 10 shown in the first figure.

To explain the operation of the above configuration, the tracking error signal input to input terminal 1 is transmitted through resistor R ₁
The DC component is waved and taken out by a low-pass filter consisting of a capacitor _C1 and an operational amplifier 17.
is applied to the inverting input terminal of The operational amplifier 17 and the like output a low level signal when this DC component is above a predetermined value, and output a high level signal when it is smaller than this predetermined value. This output signal is applied to the microcomputer 18.

The microcomputer 18 calculates the third tracking signal _p3 discriminately separated from the signal reproduced from the disk (not shown), or counts the number of kick pulses during trick play, and calculates it periodically every time, for example, 32 tracks are reproduced. The output signal of amplifier 17 is detected. For example, when transferring the regenerated needle from the outer circumferential side of the disk to the inner circumferential side, as a result of this detection,
When the output signal of the operational amplifier 17 is at a high level, no feed pulse is generated at the output port 19. On the other hand, when it is newly detected that the output signal of the operational amplifier 17 is at a low level, the microcomputer 18 outputs the signal to the output port 19 for 2 ms, for example.
Generates a feed pulse with a pulse width of .

With the next detection by the microcomputer 18,
When the output signal of the operational amplifier 17 is at a low level, a feed pulse with a pulse width somewhat wider than the previous pulse width of 2 ms is generated. Thereafter, in the same manner, the microcomputer 18 periodically detects the output signal of the operational amplifier 17, memorizes whether or not a feed pulse was generated at the previous detection, and stores whether or not a feed pulse was generated at the previous detection. When the output signal of the operational amplifier 17 is at a level that generates a feed pulse during the next detection, a feed pulse having a wider pulse width than the previously generated feed pulse is generated.

As described above, the feed feed error causes a fluctuation in the DC component of the tracking error signal, and the magnitude of this DC component corresponds to the feed feed error. In this embodiment, regardless of the magnitude of the feed error, a correction operation is performed to first reduce the feed error that is greater than or equal to a predetermined value. As a result, if the feed error is small, it can be corrected, so the microcomputer 1
Since the input signal No. 8 is at a high level, no feed pulse is generated. However, if the feed feed error is large, it cannot be fully corrected by the first feed feed error correction operation, so the input signal of the microcomputer 18 will be at a low level at the next detection, and the playback needle will be moved slightly larger than the first time. It generates a feed pulse for causing the feed to move and correcting the feed feed error. In this way, feed errors can be corrected.

Although the above embodiment is applied to a feed pulse for feeding a reproducing needle for reproducing a disc, which was previously proposed by the present applicant, it is also applicable to an optical pick-up reproducing element in an apparatus for optically reading and reproducing a disc. It can also be used as a feed pulse to move the disk in the radial direction.

As described above, the feed pulse generation circuit according to the present invention includes a detection circuit that detects when the DC component of the tracking error signal of the reproducing element is equal to or higher than a predetermined value, and a detection circuit that periodically detects the signal from the detection circuit. The present invention has a circuit that generates a feed pulse only when the DC component is equal to or greater than the predetermined value, and also generates a feed pulse with a pulse width wider than the pulse width when the feed pulse was generated during the previous detection. Compared to a circuit that constantly modulates the pulse width of the feed pulse, regardless of the magnitude of the DC component of the tracking error signal, such as the feed pulse generation circuit proposed by someone, the circuit configuration is simpler and cheaper, and it is easier to reproduce. It has features such as being able to feed the element while tracking it stably.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a conventional circuit, and FIG. 2 is a circuit diagram showing an embodiment of a main part of the circuit of the present invention. 1...Tracking error signal input terminal, 7...
Pulse width modulator, 10... Analog switch circuit, 17... Operational amplifier, 18... Microcomputer.

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. The generating circuit includes a detection circuit that detects when the DC component of the tracking error signal of the reproducing element is equal to or higher than a predetermined value, and a detection circuit that periodically detects the signal from the detection circuit, and detects when the DC component of the tracking error signal of the reproducing element is equal to or higher than the predetermined value. A feed pulse generating circuit characterized in that it has a circuit that generates a feed pulse only in the above cases, and also generates a feed pulse with a pulse width wider than the pulse width when the feed pulse is generated during the previous detection.