KR950014832B1 - Focus servo gain setting circuit for optical record disk reproducing apparatus - Google Patents

Abstract

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Description

Focus servo gain adjustment circuit of optical disc player

1 is a block diagram showing an embodiment of the present invention.

2 is a timing diagram for explaining the operation of the embodiment shown in FIG.

3 is a block diagram showing a modification of the embodiment shown in FIG.

4 and 5 are block diagrams showing a conventional focus gain gain adjusting circuit and timing diagrams for explaining the operation thereof, respectively.

* Explanation of symbols for main parts of the drawings

11 photodetector 12 subtraction circuit

13 gain variable amplifier circuit 14 switch circuit

15 lens driving signal generation circuit 16 phase protection circuit

17: drive circuit 18: focus moving coil

19: FE level detection circuit 20: focus operation control circuit

21: Addition circuit 22: Output terminal

[Industrial use]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, an optical disc reproducing apparatus such as a compact disc player, and more particularly, to an improvement in a focus servo gain adjusting circuit which is capable of automatically adjusting the focus servo gain. will be.

[Traditional Technology and Problems]

As is well known, in the fields of audio equipment and image equipment, information signals are converted into digital data and recorded on a disc in order to record / reproduce information as high as possible, and high fidelity. Background Art Optical disc reproducing apparatuses, which read digital data, have become popular. In the optical disc reproducing apparatus of this type, when reproducing data recorded on a disc, the objective lens of the optical pickup is first focused as a focus search means (hereinafter referred to as a "focal point position"). The object is held in the focal position by focusing means.

In practice, however, the objective lens of the optical pickup is moved many times in the focusing direction before the focus search is performed to determine the level of the focus error signal obtained when the objective lens passes near the focal point position. It is supposed to adjust.

4 shows a conventional focus gain gain adjusting circuit as described above, in which reference numeral 11 denotes a photodetector installed in the optical pickup. The photodetector 11 receives the reflected light of the laser beam irradiated onto the disc through an objective lens (not shown), and is configured in a so-called four-dividing manner having four light receiving regions 1 to d, where The signals output from each of the light receiving regions a and d and the light receiving regions b and c in the diagonal relationship are respectively added with current. Subsequently, both addition signals are subtracted by the subtraction circuit 12, so that the signal FE is generated at the focal point corresponding to the degree to which the objective lens is shifted from the focal point position.

The focus error signal FE is supplied to the first common contact 14a of the switch circuit 14 via the gain variable amplifier circuit 13. In addition, the lens driving signal S15 output from the gain adjustment lens driving signal generation circuit 15 is supplied to the second fixed contact point 14b of the switch circuit 14. The focus error signal FE and the lens driving signal S15 are selectively controlled by the switch circuit 14 through the phase compensation circuit 16 and the driving circuit 17 to focus the objective lens, i.e., the disk. It is supplied to the focus movable coil 18 which moves in the direction perpendicular to the surface.

In addition, the focus error signal FE is supplied to the FE level detection circuit 19 and the level is detected. The FE level detection circuit 19 changes the gain according to the level of the detected focus error signal FE. By adjusting the gain of the amplifier circuit 13, the focus gain gain is adjusted. The switch circuit 14 and the lens drive signal generation circuit 15 are controlled by the focus operation control circuit 200.

In the above configuration, when the disc is required to be regenerated, the focus operation control circuit 20 controls the switch circuit 14 to be switched to the terminal 14b and drives the lens drive signal generation circuit 15. As shown in Fig. 5A, the low frequency lens driving signal S15 is generated. Then, the lens driving signal S15 is supplied to the focus movable coil 18 via the switch circuit 14, the phase compensation circuit 16 and the drive circuit 17, as shown in FIG. 5 (b). The position L of the objective lens moves a lot in the focusing direction in response to the lens driving signal S15.

Then, when the objective lens passes through the focal point position F, the focus error signal FE as shown in FIG. 5C is obtained from the subtraction circuit 12, and the obtained signal FE The gain of the gain variable amplifier circuit 13 is set by detecting the level by the FE level detection circuit 19. By repeating this operation a plurality of times, for example six times, it is adjusted to an appropriate gain state.

Thereafter, when the focus search is performed by a conventional focus search means (not shown), the focus operation control circuit 20 switches the control so that the switch circuit 14 is connected to the terminal 14a side and generates a lens drive signal. The generation operation of the lens drive signal S15 from the circuit 15 is stopped. Thereafter, the objective lens is controlled by the focus error signal FE output from the subtraction circuit 12. The focus servo is performed by the gain of the gain variable amplification circuit 13 set here first, and is recorded on the disc. The information signal is reproduced.

However, the above conventional focus gain gain adjusting means has the following problems. That is, since the lens driving signal S15 must have an amplitude capable of moving the objective lens over the entire range of its movable range, the period becomes longer by 0.5 seconds to 1 second, and the focus error signal FE Since is only generated when the objective lens reaches the near focus position, the focus error signal FE is only generated twice in one cycle period of the lens driving signal S15.

Therefore, when the FE level detection circuit 19 detects the level of the focus error signal FE, since only a few of the focus error signals FE are detected, accurate level detection is impossible, and further focus is achieved. The problem is that the servo gain cannot be adjusted accurately. In particular, since the focus error signal FE may not be generated correctly due to damage on the disk or the like, this problem becomes more serious.

Therefore, in order to solve the above problem, if the focus error signal FE is inputted to the FE level detection circuit 19 to perform accurate level detection, the lens driving signal S15 may be several cycles (for example, about three cycles). It takes a long time of 1.5 seconds to 3 seconds only to adjust the focus gain, so that it takes a long time to actually play the sound after the disc is required to play. do.

As described above, according to the conventional focus-up gain adjustment circuit, it is difficult to accurately adjust the gain and a long adjustment time is caused.

[Purpose of invention]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a focus servo gain adjusting circuit of an optical disc reproducing apparatus which can accurately adjust the focus gain in a short time.

[Configuration of Invention]

In order to achieve the above object, the present invention determines that the objective lens has reached the focal point position based on the signal read out by the optical pickup, and reverses the polarity of the lens driving signal to focus the direction of the objective lens. The objective lens is vibrated near the focal point position by repeating the operation of reversing a predetermined number of times after passing the position.

[Action]

According to the above configuration, since the objective lens passes through the focusing position a plurality of times, and thus a plurality of focusing error signals can be obtained, accurate focus servo gain adjustment can be performed in a short time.

EXAMPLE

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a block diagram of an adjustment circuit according to an embodiment of the present invention. In FIG. 1, the same parts as in FIG. 4 are denoted by the same reference numerals, and detailed description thereof will be omitted. That is, the polarity of the lens driving signal S15 generated from the lens driving signal generating circuit 15 whenever the focus error signal FE is supplied to the lens driving signal generating circuit 15 so that the focus error signal FE is supplied. It is different from the prior art that the reversed.

On the other hand, two addition signals in which the signals output from the light receiving regions a and d are output from the light receiving regions b and c, respectively, are added by the addition circuit 21 to generate an RF signal. Is supplied to a signal processing circuit system (not shown) via the output terminal 22 to be converted into an analog signal and reproduced after data generation or error correction processing is performed.

In the above configuration, if the lens driving signal S15 is generated as shown in Fig. 2A at the time T0 during the second drawing, the position L of the objective lens as shown in Fig. 2B. ) Will change. When the objective lens passes through the focal point position F at the time T1, the focal error signal FE as shown in Fig. 2C is generated from the subtraction circuit 12. At this time, the level of the RF signal generated from the addition circuit 21 is maximized as shown in FIG.

At the timing at which the focus error signal FE is not generated at time T2, the polarity of the output signal of the lens drive signal generation circuit 15, that is, the lens drive signal S15 is inverted, and then the object is continued at time T3. The direction of the lens is reversed. This operation is repeated a predetermined number of times, such that the lens driving signal S15 and the position L of the objective lens vibrate in a short period as shown in FIGS. 2A and 2B. That is, the objective lens passes through the focal point position F within a short time to generate the focal error signal FE.

For this reason, the objective lens passes through the focal point position F several times within a short time, so that a plurality of focus error signals FE can be obtained within a short time, and the FE level detection circuit 19 causes the focus error signal ( It is possible to correctly perform level detection of FE). Thus, accurate focus gain gain adjustment can be performed in a short time.

3 shows a variation of the above-described embodiment, which inverts the polarity of the lens drive signal S15 generated from the lens drive signal generation circuit 15 by the RF signal output from the addition circuit 21. As shown in FIG. It was made to be.

According to this configuration, as shown in FIG. 2, since the RF signal is generated at the same time as the focus error signal FE, the same effect as in the above embodiment can be obtained. Further, the trigger signal for inverting the polarity of the lens driving signal S15 is not limited to the focus error signal FE or the RF signal, and may be any signal as long as it can determine that the objective lens has reached the focal point position. It becomes usable.

This invention is not limited only to the above-mentioned embodiment, It can be variously modified and implemented in the range which does not deviate from the summary.

[Effects of the Invention]

According to the present invention described above, it is possible to provide a focal servo gain adjusting circuit of a very good optical disc reproducing apparatus capable of performing accurate focal servo gain adjustment in a short time.

Claims (4)

A focus servo gain adjustment circuit of an optical disc reproducing apparatus, having a gain variable amplifier circuit 13 capable of adjusting gain and a laser beam generating source, for reproducing recording information from an optical disc with a laser beam, wherein A lens drive signal generation circuit 15 for generating a lens drive signal S15, an objective lens having a predetermined focus and moving in a direction perpendicular to the disk surface in response to the lens drive signal S15; An optical pickup apparatus having focus error signal generating means (11, 12) for generating a focus error signal (FE) in response to a focus movement of an objective lens, for picking up information recorded on a disc and generating a corresponding information signal; And a FE level detection circuit 19 for adjusting a gain of the gain variable amplifier circuit 13 in response to receiving a predetermined number of focus error signals FE. The lens driving signal generation circuit 15 inverts the polarity of the lens driving signal S15 as its output whenever the focus error signal FE or the RF signal is received, thereby increasing the speed of generation of the focus error signal FE. A focus servo gain adjustment circuit of an optical disc reproducing apparatus, characterized in that it is arranged to increase. 2. The optical pickup device according to claim 1, wherein the optical pickup device drives the lens drive signal generation circuit 15 in accordance with a focus search command and stops the lens drive signal generation circuit 15 in response to the completion of the focus search. An eye control gain adjusting circuit of the optical disc reproducing apparatus, further comprising an operation control circuit 20. The focus servo of the optical disc reproducing apparatus according to claim 1, wherein the lens driving signal generating circuit (15) is adapted to respond to a focus error signal (FE) of the focus error signal generating means (11, 12). Gain adjustment circuit. 2. The optical pickup apparatus according to claim 1, further comprising an RF signal generating circuit (21) for reproducing the recording information of the disk, wherein the lens driving signal generating circuit (15) is provided with the RF signal generating circuit (21). A focus servo gain adjustment circuit of an optical disc reproducing apparatus, characterized in that it is adapted to respond to an RF signal.

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