JPS6074167A - Feeding servo-circuit of optical head - Google Patents

Abstract

PURPOSE:To eliminate an unstable tracking state generated by a shock vibration of a disturbance or a jump of an optical pickup, etc. by inserting a limiting circuit into an inlet side of a servo-circuit, and forming its envelope to an up-and- down symmetrical shape by a limiting action even when an unsymmetrical signal seen in a traverse signal, etc. in case when the optical pickup has moved has been inputted, so that its signal is inputted to an integration circuit. CONSTITUTION:A signal controlling circuit 10 is formed by diodes D1, D2 connected in reverse to each other, and a unit amplifier G, only a signal of a constant level of positive and negative is inputted to an integration circuit 5, and it does not occur that an unstable AC signal component is generated in a feeding servo-signal. However, a tracking error signal in a normal reproducing state is supplied to the integration circuit 5 without being short-circuited by said diodes D1, D2, and supplied to a sled feeding motor 7 as a feeding servo-signal for moving an optical pickup device 2 in the radial direction.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an apparatus for reproducing information recorded on an optical disk, which is a recording medium for a video disk or a digital audio disk (in particular, for an apparatus for reproducing information recorded on an optical disk, which is a recording medium for a video disk or a digital audio disk). This invention relates to an optical head feed servo circuit for maintaining a proper tracking state of the optical pink seven horns for reproduction.

[Background technology and its problems]

Video and audio signals are arranged in a spiral pattern as uneven bit information on the recording surface of the source disk, and the device reads out the video and audio signals from the reflected light by irradiating the source disk with 7-the-light scarlet. Normally, it is essential to have a tracking servo so that the optical pickup device moves while accurately tracking the recording trunk formed in a spring roll shape.

Figure 1 shows a block diagram for removing the tracking servo, in which 1 is a rotating source disk, 2 is a source disk 1 that is irradiated with a laser beam, and at the same time the optical disk 1 is an optical pickup 7 device capable of outputting reflected light; 3 is an operational amplifier circuit for detecting tracking error (No. 8) from the reflected light; 4 is provided in the optical pickup 7 software and 12; This is the drive circuit for tracking coil tracking.

Note that the tracking fill is normally used to control the objective lens or the reflective mirror drive 1/-the nine rays so that the recording trunk of the optical disc 1 is irradiated accurately.

Reference numeral 5 indicates an integrating circuit for detecting DC component fire from the tracking error signal, and the output of this integrating circuit is power-amplified by a power amplifier 6, and then the entire optical pink pump device 2 is connected to a spark plug that moves in the radial direction. It is supplied to the feed motor 7 or a linear motor.

Note that 8 is a spindle motor that rotates the turntable, and 9 is a feed screw.

In this tracking servo mechanism, the tracking coil is controlled by the tracking error signal output from the optical pink 7-pin device 2, so that it can prevent, for example, a chunking error of the optical disc 1, an error in the roundness of the trunk, etc. Also, it is possible to irradiate the laser beam while accurately following the recording track, and the movement of the optical near 7' device 2 is also controlled by the average value of the tracking error signal.

The radial position 1a of the recording track that continues to continue, and the light pink 7-tube f! The moving distance at t2 can also be constant.

However, when shock-like vibrations are applied from the outside during playback, or immediately after a jump is made using the original pick 7 amplifier i1.2 w 7 access signal to read a specific piece of music, tracking will deteriorate significantly. .

Figure 2 shows a waveform diagram of the tracking error signal, where A is the tracking error signal in the normal playback state. In this case, it is a nearly sinusoidal signal whose period T is one rotation of the original disk. The waveform is not very large, and its amplitude is not very large.However, if the optical pickup is moved a large distance due to a jump command, or if a shocking disturbance is applied to the device, the relative position of the optical disk and optical pickup may suddenly change. Optical pickup device 2
A traverse signal is generated as shown in B when a large number of recording track gaps are skipped.

The amplitude of this traverse signal B becomes high, and when this is supplied to the tracking coil as a tracking error, the two-axis tracking servo becomes unstable, and at the same time, variations in the optical system are added. Positive
The signal output is asymmetrical in the negative direction. Therefore, when such a signal is input to the integrating circuit 5, it generates a low-frequency passthrough component as shown in C), and this erroneous feed servo signal drives the optical pickup device aZV, causing the optical The pink-up device 2 becomes increasingly unstable, and thereafter a phenomenon occurs in which the tracking servo is not stable for a long time.

[Purpose of the invention]

The present invention provides a servo circuit sent by an optical head whose purpose is to eliminate unstable tracking conditions caused by external shock vibrations or jumps of the original pickup.

[Summary of the invention]

This invention provides a feeding shore 1' for moving a light pink 7-band device.
tlt? : On the input side of the driving servo circuit, positive and negative constant /
A limiter circuit is inserted to limit the amplitude with a bell. Therefore, even if the tracking signal becomes unstable, the limiter circuit keeps its amplitude constant in both positive and negative directions, and the servo signal obtained by integrating these signals is not affected by disturbances in the tracking signal.

〔Example〕

FIG. 3 is a diagram showing one embodiment of the present invention.
The same reference numerals as in the figure indicate the same parts.

In this figure, numeral 10 denotes an η-limiting circuit placed before the integrating circuit 5 (p-pass filter).

This No. 3 control circuit 10 includes, for example, Kr and Dimate D, which are connected in reverse to each other as shown in Figure 4.

D2 and unit 7 unit G.

As is well known, these reversely connected diodes D, , D conduct at approximately 0.5 V i As shown in Figure 2, the range is ±0.
．． Signals of 5 V or higher (7, 0 or higher, with a certain level or higher centered around 0) should not be output from the 7,0V signal.

Therefore, only a signal of /bell whose positive and negative values are constant is inputted to the integrating circuit 5, and as described above, an unstable forward current signal component does not occur in the feed→]--bo signal. However, the tracking error signal in the normal reproduction state is supplied to the integrating circuit 5 without being short-circuited by the diodes D, D2, and is sent as a feed servo signal to move the original pink-up device R2 in the radial direction. Supplied to motor I.

As the signal limiting circuit 10, an energy diode may be used instead of the diodes D, , D, and it goes without saying that other active elements such as transistors can also be used as a limiter.

[Effect of understanding]

As explained above, in the optical head feed servo circuit of the present invention, a limiter circuit is inserted at the entrance of the servo circuit, and an asymmetrical signal such as a traverse signal when the optical pink 7-tube moves is inputted. Even in the event of an error, the envelope is made vertically symmetrical by the limiter action and input to the integrating circuit, so that the sending mechanism will not operate due to an erroneous sending servo signal. Therefore, even if there is a jump in the optical pickup or a disturbance vibration, the tracking servo recovers in a short time, and the optical pink amplifier device thickens the recording trunk (jumping phenomenon or unstable tracking occurs). It has the advantage of being able to

[Brief explanation of drawings]

Figure 1 is a block diagram for explaining the trucking sensor, Figure 2 is a waveform diagram of the trucking error (g and sending servo signal, Figure 3 is a block diagram showing an embodiment of this five-way servo signal). , 1iiE Figure 4 (Yoiasaki: l1l
FIG. 2 is a circuit diagram showing a specific example of an l li1 additional circuit. In the figure, 3 is an operational amplifier circuit, 4 is a dry 7° r6.5 is an integrating circuit, 6 is a power amplifier, 7 is a V-node feed motor, and 10 is a signal limiting circuit.

Claims (1)

[Claims] Tracking error signal OV on the input side of the feed servo circuit
An optical head feed servo circuit characterized by inserting a limiter that limits the amplitude at a constant positive and negative level at the center of the bevel.