JPS6220900Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a tracking servo control device in a recorded information reading device, and is particularly used in a so-called scan operation in which a desired image is searched for while viewing a reproduced image while rapidly forwarding an information reading pick-up in the radial direction of a recording disk. This invention relates to a tracking servo control device.

One of the functions of the recorded information reading device is the above-mentioned scan operation function, which periodically controls the tracking servo loop on and off and moves the scanning spot, which is a pick-up, relative to the recording track in the radial direction of the recording disk. This is done by controlling fast forwarding. More specifically, while the tracking servo loop is on, a so-called slider motor that sends the pickup in the disk radial direction is driven by a DC drive signal whose level gradually increases to perform fast forwarding, and during this fast forwarding operation, the scanning spot is It will be biased to track a predetermined recording track. Therefore, the biasing means for biasing the scanning spot for pick-up gradually rotates accordingly and the rotation angle increases, but when the rotation angle reaches almost the rotation limit, over-rotation of the biasing means is prevented. The tracking servo loop should be open (off). When the servo loop opens, the tracking biasing means returns naturally due to the restoring force of its elastic support, and when the biasing means returns to the neutral position, the tracking servo loop is turned on again, and during that time DC is applied from the outside. A slider drive signal of increasing level is applied. The above operations are repeated to perform the scan operation, but while the tracking servo loop is on, the tracking between the scan spot and the recording track is done as accurately as during normal playback. During this time, it is possible to view the reproduced image, making it extremely easy to search for a desired image while visually viewing the reproduced image.

However, in such a scan operation, the return of the biasing means to the neutral point when the servo loop is opened depends only on the restoring force of the elastic body, so depending on the characteristics of the elastic body, the bias may As the return speed of the means increases, the relative speed between the scanning spot and the track at the next loop-on time increases, making stable servo lock-in impossible.

SUMMARY OF THE INVENTION Therefore, the object of the present invention is to provide a tracking servo control device for a recorded information reading device that eliminates the above-mentioned inconvenience when the pickup scanning spot deflection means returns to the neutral point during the scan operation and enables stable servo lock-in. It is to be.

The tracking servo control device according to the present invention is
A brake signal is generated and applied to brake the movement of the pick-up during the tracking servo loop-off period during the scan operation, and the return speed of the pick-up scanning spot biasing means is quickly returned to stably and quickly perform the servo lock-in. It is characterized by the fact that

An embodiment of the present invention will be explained below with reference to the drawings. Fig. 1 is a block diagram of an embodiment of the present invention, in which numeral 1 indicates a part of a certain recording track, in the center of which there is a scanning section for reading information. When the center of spot light 2 exists, tracking spot light 3
and 4 are in such a relationship that they are on both side edges of the track 1. Therefore, the magnitude and polarity of the difference in light quantity between the tracking spot lights 3 and 4 will change depending on the amount and direction of the deviation of the center of the reading spot light 2 with respect to the center of the track 1. Therefore, the signal difference generated by the photoelectric converters 5 and 6 of both spot lights 3 and 4 is converted into a differential amplifier 7.
By extracting the tracking servo signal B, the tracking servo signal B is obtained. This signal B is amplified with frequency and phase compensation by an equalizer amplifier 8 having an equalizer circuit in its negative feedback section, and is inputted to a non-inverting input terminal of a drive amplifier 11 via a loop switch 10. The output of the amplifier 11 drives a motor 1 that drives a tracking mirror (not shown) for deflecting the spot light.
2 is driven and controlled.

A comparator 13 is provided to detect the level of this drive signal (voltage or current) A, and the level is compared with a reference level _V1 , and when a drive signal level higher than this reference level _V1 exists, a comparison detection signal is sent. is generated. The generation of this comparison detection signal triggers an MMV (monostable multivibrator) 19 to generate, for example, a high level control signal D having a constant pulse width. This panel width is determined to have a sufficient time interval for the tracking mirror, which is the deflecting means, to return to its mechanical neutral point, and the loop switch 10 is always turned off at least during the existence period of this pulse D. A command signal F is generated from the switch control circuit 14 to turn off the loop switch 10.

On the other hand, a zero cross detection circuit 15 is provided to turn on the servo loop. That is,
If the servo loop is turned on when the center of the pickup scanning spot light 2 is approximately at the center of the track 1, the tracking servo will be pulled in stably. is detected, and a servo loop close command timing signal E is generated.

Here, since the zero-crossing point of the tracking servo signal exists not only when the spot light 2 is at the center of the track, but also when it is at the center between adjacent tracks, it is necessary to detect the zero-crossing point when the spot light 2 is at the center of the track. In order to achieve this, the level detector 17 performs envelope detection on the reproduced RF output from the photoelectric converter 16 of the scanning spot light 2 to obtain a detection output C, and when this level exceeds a certain value, the zero cross detection circuit 15 detects the detection output C. A close command signal E is generated.

Furthermore, in the present invention, a low-pass filter 18 to which the drive signal A is input is provided as a brake signal generating means, and the output is applied to the inverting input terminal of the drive amplifier. There is.

FIGS. 2A to 2F are waveform diagrams of signals A to F of each part in the block of FIG. The tracking mirror for deflecting light is driven and controlled so that it gradually rotates from its rotation center and increases its rotation angle so that the spot light can track a predetermined recording track.

Therefore, during this time, the driving signal A is a superimposed signal of the tracking servo signal F, which is an AC error component, and the DC component, which is a scan signal, but only the DC component is shown in FIG. 2A for simplicity. There is.

Then, the DC level of drive signal A is the reference level.
When the voltage reaches _V1 , a comparison output is generated from the comparator 13, and the loop switch 10 is opened in response to the timing of this generation. Therefore, the biasing mirror operates to return to the rotational neutral point, but at this time, due to the action of the time constant circuit of the low-pass filter 18, the drive signal just before the loop opens remains in the filter 18, and the remaining drive signal remains in the filter 18. The level gradually decreases with the time constant (see Figure 2A). Since this time constant output is applied via the drive amplifier, it acts on the biasing mirror as a so-called braking force that brakes its movement. Therefore, the relative velocity between the scanning spot light 2 and the track in the disk radial direction is significantly smaller than in the conventional example in which no braking force is applied, and stable servo lock-in is possible.

As the timing for turning on the servo loop, the zero cross detection circuit 15 detects when the scanning spot light 2 is at the center of the track, and the timing at which this detection signal E is generated is used. is turned on, the servo loop is closed again, and image reproduction becomes possible. The scan function is performed by repeating the above operations.

FIG. 3 is a block diagram showing another embodiment of the present invention, in which the same parts as in FIG. 1 are given the same reference numerals. In this example, in order to generate a loop-off timing signal, the reproduced RF signal level by the pick-up spot light 2 is detected, and when the level falls below a predetermined value, the off-timing signal D is generated. For this purpose, the output C of the level detector 17 is compared with the reference level _V2 in the comparator 13.

Since the reproduced RF level decreases when the spot light 2 is greatly biased by the deflecting mirror and exceeds a certain angle, it is obvious that it is possible to detect this level decrease and generate the servo loop off timing signal D. , the other configurations and operations are the same as those described in FIGS. 1 and 2.

Note that the zero-cross detection circuit 15 in the circuits shown in FIGS.
The detection circuit disclosed in the specification of Japanese Patent Application No. 53-111086 may also be used. In other words, due to the presence of eccentricity, which is the deviation between the center of the recording track and the center of rotation of the disk, the relative speed between the track and the spot light changes in a sinusoidal manner during one rotation of the disk. On the other hand, it detects the playback RF signal level generated when the spot light crosses the center of the track, and generates a timing signal to close the servo loop when the speed is low and the playback RF level is high. The details are disclosed in the above-mentioned publication specification.

Furthermore, it is clear that the circuit examples shown in FIGS. 1 and 3 are not limited to these, and that various modifications can be made.

As described above, according to the present invention, since servo lock-in during scanning can be performed stably, a recorded information reproducing apparatus such as a video disk player having a stable scanning function can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram of an embodiment of the present invention.
2 is a waveform diagram of each part of the circuit of FIG. 1, and FIG. 3 is a circuit block diagram of another embodiment of the present invention. Explanation of symbols of main parts, 1...recording track,
2... Scanning spot, 10... Loop switch, 12... Biasing motor, 14... Switch control circuit, 15... Zero cross detection circuit, 18...
Low-pass filter.

Claims (1)

[Scope of utility model registration request] Tracking servo control in a recorded information reading device that enables scanning operation by periodically controlling a tracking servo loop on and off and fast-forwarding an information reading pick-up relative to a recording track in the radial direction of a recording disk. The device has a time constant circuit configured as a low-pass filter that receives the pickup drive signal as input, and applies an output of the time constant circuit to brake the movement of the pickup while the tracking servo loop is off. A device characterized in that it acts as a brake signal.