JPH029030A - Recording and/or reproducing device for optical disk - Google Patents

Abstract

PURPOSE:To dynamically cancel a stray light component even if the laser beam quantity is varied by detecting the light quantity from a laser beam source and controlling the level of a reflected or transmission light detecting signal. CONSTITUTION:The light quantity from a laser beam source passing through a beam splitter 13b is detected by an automatic power control (APC) detecting element 16, passes through an LPF 5 and supplied, a gain adjustment and an offset adjustment are executed by a control amplifier 6, and light emission power of a laser diode 11 is controlled so as to become constant through a light emission driving circuit 7. Subsequently, a signal from the amplifier 6 is supplied to a stray light cancelling circuit 8, a signal from the circuit 8 is applied to a servo-circuit 3, and stray light component in a reflected light detecting signal from a disk 1 by a photodetection element 27 of a servo photodetecting part 18 is cancelled dynamically and satisfactorily even if the laser beam quantity is varied.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an optical disc recording and/or reproducing device, and in particular to an optical disc recording and/or reproducing device that can cancel signal errors caused by so-called stray light in an optical system. Or regarding a playback device.

[Summary of the invention]

The present invention provides an optical disc recording and/or reproducing apparatus that records and/or reproduces signals while irradiating an optical disc with a laser beam through an optical system, in which at least a photodetecting element is detected according to a light amount detection output of a laser light source. By controlling the detection signal level from the optical system, signal errors caused by so-called stray light in the optical system can be dynamically canceled.

[Conventional technology]

Optical systems used in devices for recording and/or reproducing optical disks such as so-called CDs (compact disks), optical video disks, or magneto-optical disks, such as optical pickup devices, contain so-called stray light, i.e. There is unnecessary light generated by causes other than regular refraction or reflection, and this stray light enters a photodetector for signal detection and adversely affects the detection signal.

In order to eliminate signal errors (stray light errors) caused by this stray light, conventionally, electrical DC offset adjustment has been performed individually for each detection element.

This is to cancel errors by subtracting a signal level (DC offset) corresponding to the stray light component entering each detection element from the level of the detection signal.

[Problem to be solved by the invention]

By the way, the stray light error can be canceled by DC offset adjustment as described above when the stray light inside the optical system such as an optical pickup device is approximately constant and the stray light components entering each detection element are approximately unchanged. However, if the light emission scene of the laser light source changes, the amount of stray light will change accordingly, so there is a risk that cancellation will not be performed properly and the effects of stray light errors will remain. be. In particular, in recordable optical disks such as magneto-optical disks, there are recording, erasing, and reproducing modes, and the laser emission intensity or light amount differs for each mode, and during recording, the laser emission intensity is modulated according to the data signal. Therefore, the change in the amount of stray light within the optical system is large, and the negative effects caused by the stray light error can hardly be resolved by the DC offset adjustment.

Further, even when handling disks with different reflectances, stray light errors cannot be canceled only by the DC offset adjustment described above.

Therefore, in the optical pink amplifier device for recordable optical discs, all parts of the internal wall of the optical system that are likely to reflect or scatter light are treated with anti-reflection and light-absorbing treatments such as black dyeing and flocking. It is currently being assembled. However, when such processing is performed, in order to ensure mechanical precision, it becomes necessary to calculate the thickness of each coating (several μm) before processing, which increases costs both in terms of design and man-hours. It turns out. Moreover, even if such processing is performed, the light reflected from the internal surface of the optical component cannot be completely reduced to zero, and some stray light will remain, resulting in the effects of stray light errors remaining.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical disc recording and/or reproducing device that can effectively cancel stray light errors even when the emission intensity of a laser light source changes. shall be.

[Means for solving the problem] An optical disc recording and/or reproducing device according to the present invention includes:
In order to solve the above-mentioned problems, a laser beam is irradiated onto an optical disk through an optical system, and the reflected light or transmitted light is detected by a photodetection element in the optical system, while recording and/or recording signals. Alternatively, in a recording and/or reproducing apparatus for an optical disc that performs reproduction, the level of the detection signal from the photodetecting element is adjusted according to the detection output from the laser beam detection means for detecting the amount of light from the laser beam source. It is characterized by control.

Here, the photodetecting element may be, for example, a photodetecting element for detecting a tracking error or a focus error for servo-controlling the positional relationship between the optical disk and the optical system, or a photodetecting element for detecting a data signal. A photodetecting element etc. can be considered. Further, as a level control process of the detection signal from the photodetecting element according to the detection output from the laser light amount detection means, the laser light amount detection output is converted into a signal of a stray light component included in the detection signal from the photodetection element. A conceivable process is to adjust the gain according to the level, reverse the polarity, and add it to the detection signal.

[For production]

Even if the stray light component included in the detection signal from the photodetection element fluctuates according to the change in the laser light intensity, the stray light component in the detection signal can be controlled by controlling the level of the detection signal according to the nuclear laser light intensity. can be canceled dynamically.

(Embodiment) FIG. 1 is a schematic diagram showing a schematic configuration of a magneto-optical disk recording and reproducing apparatus which is an embodiment of the optical disk recording and/or reproducing apparatus according to the present invention.

In the apparatus shown in FIG. 1, an optical pickup device 10 for irradiating a magneto-optical disk l with a laser beam and introducing reflected light for detection includes at least a laser diode 11 serving as a laser light source, a collimating lens, and a collimating lens. 12 and
Beam sulfur printer 13 (in the embodiment, two beam spherules)
The laser diode 11 has a splitter 13a, 13b), an objective lens 14, and a reflected light signal detection section 15, and also has a so-called APC (automatic power control) that automatically controls the emission power (light amount) of the laser diode 11 to be constant. The photodetecting element of the light amount detecting means (for example, the so-called PI
N photodiodes) 16 are provided. In this optical pickup device 10, a laser diode 1
The laser beam emitted from the collimating lens 12
The beam is made into a parallel light beam by the beam splitter 13a.
and 13b, and is projected onto the magneto-optical disk 1 via the objective lens 14. Here, beam splitter 13
A part of the light beam incident on b is incident on the photodetecting element 16 for APC via the lens 17. The reflected light from the magneto-optical disk 1 is incident on the beam splitter 13b via the objective lens 14, a part of which is reflected and guided to the reflected light signal detection section 15, and the other part is transmitted and becomes the beam. - The beam enters the beam splitter 13a, is reflected by the beam splitter 13a, and is guided to the servo photodetector 18.

As the reflected light signal detection unit 15, a so-called differential detection type configuration consisting of, for example, a λ/2 plate 21, a polarized beam splinter (PBS) 22, and two photodetection elements 23 and 24 is used. However, various other configurations of the reflected light signal detection section can be used.

The servo light detection unit 18 includes a detection lens 26 and a PIN
The detection output signal from the photodetection element 27 is sent to the servo circuit 3 and is processed by a predetermined servo control signal, such as a tracking servo control signal or a focus servo control i>5. It is output as a signal. By sending the servo control output signal from the servo circuit 3 to the servo drive mechanism 4, at least the objective lens 14 is driven and controlled, and predetermined tracking servo and focus servo are performed.

Here, the detection signal of the laser emission power (laser light amount) from the photodetector element 16 for APC is several kHz to several +
k) lz signal is sent to the control amplifier circuit 6 via the LPF C low-pass filter) 5, and after gain adjustment and offset adjustment are performed in the control amplifier circuit 6, the light emission drive of the laser diode 11 is performed. It is sent to circuit 7. As a result, the light emitting power or light amount of the laser diode 11 is automatically controlled to be constant.

In the embodiment of the present invention, stray light is canceled by controlling the signal level of the servo circuit system, etc., according to the laser light amount detection signal of the PC circuit system, and specifically, the laser light amount detection signal is By adjusting the polarity so that it is reversed and adding (in other words, subtracting) it to the servo error signal of the servo circuit system, the stray light component (depending on the amount of laser light) contained in the servo error signal, etc. This dynamically cancels out fluctuating stray light components.

That is, the light emission power detection signal of the APC circuit system, for example, the output signal from the control amplifier circuit 6, is sent to the stray light canceling circuit 8, and the stray light canceling signal output from the stray light canceling circuit 8 is sent to, for example, the servo circuit 3. It is subtracted from the servo error signal.

Next, FIG. 2 is a block circuit diagram showing a specific configuration example of a part of the APC circuit system and the stray light canceling circuit 8. In FIG. In this FIG. 2, a photodetector element (PIN
The detection signal from the photodiode) 16 is sent, for example, via a trans-impedance type head amplifier 31 to an LPF 5 consisting of a resistor 5'' and a capacitor 5C, which detects signals from several kHz to several tens of kiloliters (z). This is the data signal component (usually M
] (z order). This LPF5
The laser light amount detection signal from
The signal is sent to the APC signal output terminal 34 via the rectifying amplifier 33. The output signal from this gain adjustment amplifier 32 is sent via the buffer amplifier 35 of the stray light canceling circuit 8 to gain adjustment amplifiers 36, 37, 38, etc. for each servo.

These gain adjustment amplifiers 36, 37, and 38 are used to generate stray light canceling signals with appropriate gain and polarity in response to stray light components included in various servo error signals, and for example, to cancel stray light from the amplifier 36. The signal is sent to the tracking/knocking servo circuit for tracking/knocking.
The stray light cancellation signal from the amplifier 37 is sent to the focus servo circuit and added to the focus error signal, and the stray light cancellation signal from the amplifier 38 is sent to the disk motor pull-in servo circuit to pull it in. It is used in such a way that it is added to the error signal. In addition, adjustments can be made to send stray light cancellation signals to various servo circuits.

In addition, when performing stray light cancellation processing according to the laser emission power on the output signal from the data signal detection element, the so-called RF multiplied signal, the laser emission power detection signal including the band up to the RF signal level is used. By performing gain adjustment including polarity using the RF signal to generate a stray light canceling signal, and adding the RF multiplied signal, stray light can be canceled extremely effectively.

According to the embodiments described above, the servo error signal and R
Even if the stray light component included in the F signal varies depending on the emission power or light intensity of the laser diode that is the laser light source, the stray light cancellation signal changes to follow the emission power or light intensity, so it is always effective. Stray light cancellation is possible.

Note that the present invention is not limited to the above embodiments,
For example, in addition to magneto-optical disk recording and reproducing devices, the present invention is not only applicable to various optical disk recording and reproducing devices such as write-once optical disk recording and reproducing devices, but also to recording-only or reproducing-only devices. You can also do it. Of course, various modifications can be made without departing from the gist of this invention.

〔Effect of the invention〕

According to the optical disc recording and/or reproducing apparatus according to the present invention, even when the stray light component included in the detection output signal from the photodetecting element varies depending on the light intensity of the laser light source, stray light cancellation of the detection output signal is performed. By changing the level control amount to follow the above laser light amount,
Stray light can be canceled dynamically, and bad images caused by stray light errors can be effectively prevented with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of an embodiment of an optical disc recording and/or reproducing apparatus according to the present invention, and FIG. 2 is a diagram showing a specific configuration of a part of an APC circuit system and a stray light canceling circuit in the embodiment. FIG. 2 is a block circuit diagram illustrating an example. 1・・・・・・・・・Magneto-optical disk 3・・・・・・
... Servo circuit

Claims (1)

[Scope of Claims] An optical disc in which signals are recorded and/or reproduced by irradiating a laser beam onto the optical disc via an optical system and detecting the reflected light or transmitted light by a light detection element within the optical system. The recording and/or reproducing device is characterized in that the level of the detection signal from the photodetecting element is controlled according to the detection output from the laser light amount detection means for detecting the light amount from the laser light source. Optical disc recording and/or playback device.