JPS6190376A - Loop gain adjusting circuit of tracking servo circuit - Google Patents

Abstract

PURPOSE:To automatically adjust the volume of a loop gain properly against an external disturbance and to obtain a stableness of tracking, by identifying the disturbance according to the variance of an average value of tracking error signals and information signals which occur against the external disturbance. CONSTITUTION:The current which corresponds with intensity of light received by B, C parts of photodetector 12 through a lens 11 is added t amplifiers 21, 22, and 23, and forms a information signal 27 recorded on the disc. The average value of the envelope of the information signal is detected 24, and according to the output and the delayed 25 output, a hysteresis comparator 26 detects the external disturbance. Due to the existence of this disturbance, the tracking error signal is increased, and the comparator 26 outputs the detection signal only when the output of the detector 24 is the average value of the envelope of information signal and the average of the lost part is smaller than other average values. And, by the increase of the tracking error signal a level detector 19 issues detection signal, and a selection circuit 20 keeps a variable loop filter 17 at the loop gain of normal reproduction.

Description

[Detailed Description of the Invention] [Field of Application on Pressure] This invention relates to a loop gain adjustment circuit for a tracking servo circuit. t9 relates to the loop gain adjustment circuit of the tracking servo circuit that can automatically adjust the loop gain of the fvr-tracking servo circuit to an appropriate value of M with less tracking and less distortion.

[Conventional technology]

Conventionally, in an information recording disk reproducing device that uses a light beam as an FP amplifier reproducing element, the pickup reproducing element is tracked and controlled by a tracking error signal so that the pickup reproducing element accurately follows and scans on the friend track where the hell is recorded with gC. That's what I do. The loop gain A circuit of the tracking servo circuit is a process that increases the loop gain of the tracking servo circuit by detecting level fluctuations in the tracking error signal that occur in response to disturbances applied to the pickup Niyu element and the playback device. A tracking servo circuit is known in which the VC is set.

A conventional example of a loop gain adjustment circuit for this unconventional tracking servo path is shown in FIG. There are 2 optical inspections in the figure!
I (l device (via the track (9) on the A part and D part of the chest) (10) It is output in a size according to the intensity of the light incident through the sword lens (8) and mirror (7). The current is converted into a rolling force by the front amplifier US+ and O.
A tracking error number 1g representing the deviation from the track center is obtained. For normal tracking without disturbance, variable loop filter Qη and servo increase 1m@i
The loop gain is set to the optimal gain for tracking control by @u6. The tracking error signals of the front three are amplified and phase compensated to the optimum magnitude for tracking control by a variable loop filter 117) and a servo amplifier (16), and are applied to a drive circuit μs), which fully drives the tracking mirror (7). A light beam spot (not shown) on the disk is controlled to follow and scan the entire track. If a disturbance causes the spot on the disk to deviate from the track, the tracking error signal output from the differential amplifier (b) will increase, and the level change of this tracking error signal will be detected by the level detector w and selected. By modifying the circuit, the variable loop gain tarry η is set so that the loop gain becomes large, and it works to prevent the spot on the disk from deviating from the track.By the way, the disk on which information is recorded has a transparent recording surface. Itsuki B'fi (
9), and air bubbles or opaque foreign matter may be mixed into the structure. This work') field θ,
The bubble in the butt causes some lens effect, the refractive index in the bubble part of the disc is different from that in the transparent part, the light beam moves and the tracking error signal becomes large, and the loop gain is set to a larger value so that the spot is not tracked. A plow that follows the top. However, in the case of opaque foreign matter, a phenomenon occurs in which the entire light intensity distribution is distorted, so that the tracking error signal increases even if the pot is not off track.

Along with this, the loop gain is also set high and the circuit works to return the spot to the track. However, since the spot was not actually off the track, the spot was moved off the track by the above-mentioned operation, and the reproduction characteristics deteriorated significantly.

[Problem that the invention seeks to solve]

With the above configuration, the loop gain adjustment circuit of the conventional tracking servo circuit is subject to disturbances such as vibrations on the disk that actually cause the spot to deviate from the track and increase the tracking error signal. Bubbles can be dealt with by increasing the loop gain, but the tracking error No. 18 will also increase, but in reality, the spot will be affected by disturbances that are not off track, such as scratches and opaque foreign objects on the disk. On the other hand, the total loop gain is 211! It is preferable to set it to the same value as during tracking control without normal disturbances, or lower than that, and it is said that the loop gain adjustment circuit that adjusts the loop gain to make the loop gain higher will not increase the disturbance in response to such disturbances. There were a lot of problems.

The present invention has been developed to solve these problems by providing a tracking circuit that can automatically adjust the loop gain of a ranking servo circuit to an appropriate amount for all kinds of disturbances and that does not cause malfunctions. There is a loop gain regulator whose entire purpose is to gain control.

[Means for deciding the issue]

Ludag 1 of tracking servo circuit according to this invention
The adjustment circuit includes a level detector that detects level fluctuations of the tracking error signal, and a pickup reproduction system that detects information B.
An average detector for detecting fluctuations in the average value of the envelope of the information signal obtained from the track to be scanned on the c-recording disc, and a gain adjustment means and metal part installed in a part of the tracking servo loop. It is.

[Effect]

In the above configuration, the level detector detects the level of the detection signal that detects the fluctuation caused by the disturbance Vc of the average value of the envelope of the information signal recorded on the disk using the average value detector, and the conventional tracking error signal. 7) Determine whether or not the zero disturbance has caused the spot to deviate from the track and the track difference 1g has become large using the fc detection signal, and The variable loop filter, that is, the loop gain variable means, is fully automatically added to the loop gain in order to add to the loop gain that is consistent with disturbances, and comfortable servo production can be obtained.

[Actual M example]

FIG. 1 is a block diagram showing the air path of an information RID recording disk reproducing device embodying the present invention, and parts of Ib1 are given the same reference numerals as those in FIG. 4.

The example is an average value detector that detects the average value of the envelope of the information signal output from the summing amplifier E+, Naka1 is a delay circuit that delays the output of the average value detector example by a time gap, and nr is the average value detector Saku. This is a hysteresis comparator that compares and detects the output and the output of the delay circuit. Since the operation of the control loop has been described above, a detailed description thereof will be avoided here, and the operation of the detection function based on the average value of the envelope of the previous 8-pin information signal, which is the main part of this invention, will be explained. Photodetector (3 parts of the lens, lens α, 1 in the C part) outputs 9 magnitudes according to the intensity of the light that enters the T-valve, fCC mudflow, and 1 pressure at the preamplifier ■11. Replaced, these, engineering 8
The output of the amplifier 1211 t is the Ω arithmetic amplifier (4))
The information is calculated by 77D and recorded on the disc. By the way, the amount of light incident on the photodetector (121) is small because the light beam is diffusely reflected at the protruding pits 4 forming the tracks (9) of the disk.
On other mirror surfaces of the disk, most of the emitted light is reflected and returned to the surface. Figure 2 (a) shows this relationship, and shows that the incident light intensity is the point tP when the spot β is following the track center, and that the spot deviates from the track as it moves to both sides of the track, and the amount of incident light is increase When the optical beam follows the track, the minimum amount of incident light when the spot is above the bit and the maximum amount of incident light when the spot is on the mirror surface do not change. However, in the case of disturbances, in this case shooting and air bubbles on the disk, the maximum incident light intensity when the spot is on the mirror surface VC does not change, but the reflected photoelectricity when the spot is on the track VC is, for example, as shown in Figure 2 (B). When the spot β moves in the X direction of the arrow due to a disturbance as shown in Fig. 2, 6.
) Ic L'd as shown by the arrow. Therefore, Figure 3 H)
Figure 3 (
In contrast, if there is hot water or opaque foreign matter on the disk, the scratches and opaque foreign matter will distort the light intensity distribution.
The weight of light incident on the light detector 6 is reduced. The reduction ratio is the same whether it is on a spot or in focus or on a mirror surface. Therefore, since the amount of change changes in proportion to the absolute K VC of the amount of incident light, the amount of change in the minimum amount of incident light when the spot is on the bit VC and the amount of change in the amount of take-up incident light when the spot is on the @ plane are significant. Since this is a mystery, the information signal envelope is missing the upper part, as shown in Figure 3-1. In other words, the average value of the information signal envelope is detected by the average value detector, and the output signal is sent to the delay circuit Liu.
Hysteresis comparator □
By performing comparative detection using □□, it is possible to detect which disturbance caused the disturbance. In addition, since the tracking error signal increases as a result of any of the disturbances mentioned above, the hysteresis comparator '2JJI, which is a comparison detector, detects the missing part of the upper part of the signal envelope, that is, the disturbance on the disk. It is good to output the detection number H only in the case of scratches or opaque foreign objects. Therefore, the output of the hysteresis comparator GIBI is, for example, the average of the information signal envelope in Figure 3 e>, and the average value of the B point is equal to the average of the missing part 111
If N is smaller than the average amount at point A delayed by time T, a detection signal is output. In normal disturbance-free reproduction, the information signal envelope is completely free of defects as shown in FIG. In addition, since the tracking error signal does not show large fluctuations, the level detector 119) does not output the full detection signal, and the 9-variable loop filter u'7) is not operated by the selection circuit 1.201, and tracking control during normal playback is performed. The loop gain calculated by vca is maintained. Next, the added disturbance, here ``c'', is the output &- even if the bottom of the information signal envelope is missing due to shooting or air bubbles on the disk. The average number of shifts is shown as ρj,
Since the point B, which is the average value of the defective value of the hysteresis comparator (A), is larger than the point A, no information signal is output.

However, the tracking error signal increases, and the Lebel detector (selection circuit 20 based on the output VC of the IQ) operates the 9-variable loop filter (17) to increase the loop gain. Also, if the upper part of the information signal is lost due to hot water on the disk or an opaque foreign object, and it is input to the average value detector example, the average value will be the f1000%j value shown in Figure 6BJ, and hysteresis will occur. Comparator example C detects that the average value at point B and the average value at the 1V defective portion are delayed by time T by the delay circuit (25iK) and is smaller than the average value at point 7'cA, and outputs a detection signal. When the tracking error increases by 1g, a detection signal is output from the ELI level detector (19), and the selection circuit (■) selects m! from the two detection signals. 1)i
iT variable loop filter I: Traverse to 17' and operate to maintain the same loop gain during playback.

In the above embodiment, the seismic loop filter IJTJ was set in two stages: normal and when the loop gain is increased. When the detection signal is output and the loop gain is adjusted, the detection signal that is output from the level detector (191) and the upper part of the information signal envelope at that time is missing, so the signal is output from the hysteresis comparator Q!B+. The 9-variable loop filter may be set in all three stages, including when the gain is lowered from the normal level with the detection signal.

〔Effect of the invention〕

As described above, according to the present invention, the loop gain is determined to be appropriate for the light beam spot to follow the track after all disturbances are identified by the variation between the tracking difference signal generated in response to the disturbance and the average value of the information signal. Since it is automatically adjusted, there is no need for complicated operations, and the effect is that stable tracking can always be performed in response to external disturbances.

[Brief explanation of the drawing]

Fig. 1 is a block system diagram showing an example of this % brightness, and Fig. 2 (t(), f) shows the transfer of the original beam! FIG. 6 is an explanatory diagram for explaining changes in the amount of incident light due to g. (b), t'S) are explanatory diagrams of each issue of information signals and tracking errors for explaining the detection circuit of the present invention, No. 4
The figure is a block system diagram "'C" showing a conventional example. In the figure, (9) is a disk, α0) is a track, M
ノ is a 9-variable loop filter, σ is a level detector, (5)
) is the selection circuit, - is the average value detector, the example is the delay circuit, and the symbol is the hysteresis conoparator.

Claims (2)

[Claims] (1) In a tracking servo circuit in which a pickup reproducing element amplifies a tracking control reference signal obtained from a track to be scanned on an information recording disk to obtain a tracking error signal, and in which the pickup reproducing element is subjected to tracking control using this tracking error signal. , a level detector for detecting a level variation of the tracking error signal; and an average value detection means for detecting a variation in an average value of an envelope of an information signal obtained by the pickup/reproducing element from a track to be scanned on the information recording disk. and gain variable means provided in a part of the tracking servo loop for setting the tracking servo loop gain to an optimal gain based on the level fluctuation detected by the level detector. Adjustment circuit. (2) The average value detection means includes an average value detector, a delay circuit that delays the average value of the envelope of the information signal detected by the average value detector by a predetermined time, and a signal that passes through the delay circuit. The tracking servo circuit according to claim 1, further comprising a comparison detector that compares the signal with the signal that does not pass through the delay circuit and outputs a detection signal depending on the magnitude of the signal. loop gain adjustment circuit.