JPH02156428A - Optical disk device - Google Patents

Abstract

PURPOSE:To make exact gain adjustment by shielding the light irradiating a disk by a light shielding means to prevent the reflection of the light from the disk at the time of adjusting the gain of the correction signal forming circuit of a servo circuit. CONSTITUTION:A light shielding plate 4 is inserted into an optical path by a driving means 5 at the time of adjusting the gain of the correction signal forming circuit 10 of the servo circuit 6 according to the quality of the stray light by an optical output detecting circuit 9. The irradiation light to the disk 3 is shut off in this way and the generation of the reflected light from the disk 3 is prevented. The gain of the circuit 10 is thus exactly adjusted according to the quantity of stray light in such a manner that there is no output of the photodetector 7 and the output of a subtracter 8 is decreased to zero.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disc device that removes errors caused by stray light from the output signal of a photodetector and corrects the output signal to a proper output signal.

[Conventional technology]

In an optical disc device, light emitted from a light source is irradiated onto the disc, and a photodetector generates a reproduction signal, a tracking error signal to guide the optical spot to a proper track, and a tracking error signal to focus the optical spot to an appropriate position. is converted into a focus error signal.

However, a part of the light emitted from the light source is reflected by the optical system in the optical pickup and the holder that holds them, and becomes so-called stray light that is unrelated to recording and reproducing information. Since the light intensity distribution of this stray light is not uniform, when a photodetector receives the stray light, accurate tracking error signals and focus error signals cannot be obtained.

Conventionally, the amount of stray light is almost proportional to the laser output of the light source. The error due to this was removed.

Such an optical disc device includes, for example, a servo signal correction means 21, as shown in FIG.

In the servo signal correction means 21, a photodetector 22 receives reflected light from a disk (not shown) and outputs a servo signal for generating a tracking error signal and a focus error signal, and also outputs a servo signal when stray light is received. outputs an error signal that appears as an error. The correction signal generation circuit 23 is outputted from the optical output detection circuit 24,
A correction signal is generated by attenuating an optical output signal corresponding to the optical output of a light source (not shown) based on a predetermined gain. The error signal is subtracted by the subtracter 25 and output as a corrected error signal, and then sent to the corrected error signal detection circuit 2.
6, it is converted into a detection signal and sent to the correction signal generation circuit 23.
will be sent to.

In the correction signal generation circuit 23, the gain is adjusted according to the detection signal, and the optical output signal is attenuated based on this gain to generate a correction signal again. In this way, the gain is repeatedly adjusted and the value at which the corrected error signal becomes O is held.

When recording or reproducing, the servo signal is converted into a tracking error signal and a focus error signal by subtracting a correction signal generated based on the gain adjusted as described above.

[Problem to be solved by the invention]

However, in the conventional optical disc device described above, when the disc is stored, the photodetector 22 receives reflected light from the disc. For this reason, the photodetector 22 cannot output only the error signal caused by the stray light, and the correction signal generation circuit 23 cannot perform gain adjustment according to the error signal caused by the stray light.

Further, as described above, since an appropriate gain cannot be obtained, there is a problem in that the servo signal cannot be corrected correctly.

[Means to solve the problem]

In order to solve the above problems, an optical disk device according to the present invention includes an optical output detection circuit that converts the optical output of a light source into an electrical signal and outputs it as an optical output signal, and a predetermined gain that adjusts according to the amount of stray light. , an optical disk device equipped with a correction signal generation circuit that generates a correction signal by attenuating the optical output signal based on this gain, and a subtracter that subtracts the correction signal from the output signal of the photodetector. The present invention is characterized in that it includes a light shielding means that blocks light irradiated onto the disk and does not reflect it, and a driving means that drives the light shielding means to a light shielding position when the gain is adjusted.

[For production]

With the above configuration, when adjusting the gain of the correction signal generation circuit, the light shielding means is driven by the driving means and moves to the light shielding position. When the light blocking means moves to the light blocking position, the light emitted from the objective lens is blocked and not reflected, so that the disk is not irradiated with light. Therefore, there is no reflected light from the disk, and the photodetector receives only the stray light and outputs a signal. The correction signal generation circuit generates a correction signal by attenuating the optical output signal of the optical output detection circuit based on a predetermined gain. The above-mentioned correction signal is subtracted from the output signal of the photodetector in a subtracter, and the above-mentioned gain is adjusted according to the signal output as a result. Such gain adjustment is performed until the output signal of the subtracter reaches O.

When recording or reproducing, a correction signal is generated based on the gain adjusted in the correction signal generation circuit. Then, by subtracting the correction signal from the output of the photodetector in the subtracter, errors caused by stray light can be accurately removed.

〔Example〕

An embodiment of the present invention will be described below based on FIGS. 1 and 2.

As shown in FIG. 1, the objective lens 1 is provided at the top of an optical pickup (not shown), and is configured to irradiate and focus the light emitted from the light 52 onto the disk 3.

Between the objective lens l and the disk 3, a light-shielding Fi4 serving as a light-shielding means is provided so as to be movable in parallel with the disk 3, and is driven by a driving means 5. During recording or playback, it waits at a standby position. ing.

The driving means 5 is constituted by, for example, a solenoid or the like,
It is designed to generate a driving force that moves the light shielding plate 4 in parallel, and drives the light shielding plate 4 from the standby position to between the objective lens 1 and the disk 3 when adjusting the gain of the correction signal generation circuit 10, which will be described later. It looks like this. Further, when the gain adjustment is completed, the light shielding plate 4 is driven to return to the standby position.

The servo signal correction means 6 shown in FIG. 2 removes errors caused by stray light from signals output from the photodetector 7 that are converted into tracking error signals and focus error signals (hereinafter referred to as servo signals). This is to perform correction.

In the servo signal correction means 6, the photodetector 7 is connected to the subtracter 8.
The optical output detection circuit 9 is connected to the other input side of the subtracter 8 via the correction signal generation circuit 10. The output side of the subtracter 8 is connected to a correction signal generation circuit 10 via a correction error signal detection circuit 11.

The photodetector 7 is a light receiving element that receives light and converts it into an electrical signal, and is adapted to receive reflected light from the disk 3 and output a signal. In addition to the reflected light from the disk 3, the photodetector 7 receives stray light generated within the optical pickup, and outputs a signal (hereinafter referred to as an error signal) having a magnitude corresponding to the amount of stray light. This error signal is apparently included in a part of the servo signal.

The subtracter 8 is a circuit that subtracts the correction signal generated by the correction signal generation circuit 10 from the output signal of the photodetector 7.

The light output detection circuit 9 is a circuit that receives the light emitted from the light source 2 by a light receiving element such as a monitor diode, converts it into an electrical signal, and outputs the electrical signal as a light output.

The correction signal generation circuit 10 generates a correction signal by adjusting the gain according to the detection signal sent from the correction error signal detection circuit 11 and attenuating the optical output signal of the optical output detection circuit 9 based on the gain. This is a circuit that does this.

The correction error signal detection circuit 11 uses a subtracter 8 to subtract the correction error signal of the correction signal generation circuit 10 from the error signal of the photodetector 7 and detects the output signal as a correction error signal, and determines the magnitude of this signal. This circuit outputs a detection signal in response to the

In the above configuration, when recording or reproducing, the light shielding plate 4 is in a standby position, and the light irradiated from the objective lens 1 onto the disk 3 is reflected by the disk 3 and taken into the objective lens l.

When adjusting the gain of the correction signal generation circuit 10 in order to correct the servo signal by the servo signal correction means 6,
The light shielding plate 4 is driven by the driving means 5 and moves from a standby position to between the objective lens 1 and the disk 3, and blocks the light irradiated from the objective lens 1 to the disk 3.

When the light irradiated to the disk 3 is blocked as described above,
There is no reflected light from the disk 3, and the photodetector 7 receives only the stray light and outputs an error signal. On the other hand, the correction signal generation circuit 10 generates a correction signal by attenuating the optical output signal of the optical output detection circuit 9 based on a predetermined gain. The correction signal is subtracted from the erroneous arrival signal by a subtracter 8, and the result is output as a correction error signal. This corrected error signal is
The corrected error signal detection circuit 11 converts it into a detection signal.

In the correction signal generation circuit 10, the correction error signal detection circuit 11
The gain is adjusted in accordance with the detection signal output from the sensor, and a correction signal having a magnitude corresponding to the error signal is generated based on this gain. For example, if the detection signal has a positive value, the gain is adjusted so that the correction signal becomes larger, and if the detection signal has a negative value, the gain is adjusted so that the correction signal becomes smaller. The newly generated correction signal is subtracted from the error signal again in the subtracter 8. Such gain adjustment is repeated until the correction error signal becomes O. When the correction signal becomes O, the correction signal generation circuit 10
The gain at this time is held.

When the gain adjustment is completed, the light shielding plate 4 is driven by the driving means 5 and returns to the standby position, and the light from the light source 2 is irradiated onto the disk 3 again. When recording or reproducing in this state, a correction signal is generated in the correction signal generation circuit 10 based on the gain adjusted as described above.

The servo signal output from the photodetector 7 is converted into a tracking error signal and a focus error signal by subtracting the above-mentioned correction signal in a subtracter 8.

〔Effect of the invention〕

As described above, the optical disk device according to the present invention includes an optical output detection circuit that converts the optical output of a light source into an electrical signal and outputs it as an optical output signal, and an optical output detection circuit that adjusts a predetermined gain according to the amount of stray light. In an optical disc device, the optical disc device includes a correction signal generation circuit that generates a correction signal by attenuating the optical output signal based on the optical output signal, and a subtracter that subtracts the correction signal from the output signal of the photodetector. This configuration includes a light shielding means that blocks light and does not reflect it, and a driving means that drives the light shielding means to a light shielding position when the gain is adjusted.

Thereby, when adjusting the gain of the correction signal generation circuit, the driving means drives the light shielding means to the light shielding position, so that the light emitted from the light source is not focused on the disk. Therefore, less light is reflected from the disk, and the photodetector receives only the stray light and outputs a signal, allowing a gain corresponding to the amount of stray light to be obtained.

Furthermore, when recording or reproducing, a correction signal generated based on the gain is subtracted from the output signal of the photodetector in a subtracter, so that errors caused by stray light can be accurately removed.

Therefore, even if the disc is present in the optical disc device, it is possible to correct the photodetector.

[Brief explanation of the drawing]

1 and 2 show one embodiment of the present invention, in which FIG. 1 is a side view illustrating the operation of the light shielding means, and FIG.
The figure is a block diagram showing the configuration of the servo signal correction means. FIG. 3 is a block diagram showing the configuration of a servo signal correction means in a conventional optical disc device. 4 is a light shielding plate (light shielding means), 5 is a driving means, 7 is a photodetector, 8 is a subtracter, 9 is a light output detection circuit, 10 is a correction signal generation circuit, and 11 is a correction error signal detection circuit.

Claims (1)

[Claims] 1. An optical output detection circuit that converts the optical output of a light source into an electrical signal and outputs it as an optical output signal; and an optical output detection circuit that adjusts a predetermined gain according to the amount of stray light and generates an optical output signal based on this gain. In an optical disc device equipped with a correction signal generation circuit that generates a correction signal by attenuating the correction signal, and a subtracter that subtracts the correction signal from the output signal of a photodetector, the optical disc device blocks the light irradiated from the objective lens to the disc, and,
An optical disc device comprising: a light shielding means that does not cause reflection; and a driving means that drives the light shielding means to a light shielding position when the gain is adjusted.