JPH03142716A - Optical disk device - Google Patents

Abstract

PURPOSE:To enable a double-write preventing function with the small amount of a hardware and to obtain a compact and low-priced optical disk device by switching an amplification factor for cases that reflected light is caused by a light beam at the time of reproducing and that it is caused by a recording light beam. CONSTITUTION:The laser beam is transmitted through a polarized beam splitter 7, made incident to an objective lens 8 and converged toward a recording film 1a of an optical disk 1 by the objective lens 8 and information are recorded onto the recording film 1a. The detection of double writing is executed parallelly with a recording operation. An analog switch 51 is controlled to OFF at the time of reproducing and controlled to ON at the time of recording and one of signals amplified by amplifiers 17 and 18 is supplied to a focus servo circuit 16 after an error amplifier 19 and used for focusing control. The other one of the signals amplified by the amplifiers 17 and 18 is supplied to an adder 29 and after executing addition, the signal is supplied to a recorded signal binarizing circuit 30. Thus, the compact and low-priced optical disk device can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an optical disc device for recording and reproducing information on and from an optical recording medium such as an optical disc.

(Prior Art) Conventionally, in information recording devices such as optical disk devices that optically record or reproduce information on optical recording media such as write-once or erasable optical disks, comparisons have been made with semiconductor lasers as light sources. Information on the optical disk is read using a continuous optical output with a relatively small value, while information is recorded on the optical disk using an optical output that is intermittently changed over a relatively large predetermined value. Therefore, when the optical disc is irradiated with a light output equal to or higher than the predetermined value, even if this is due to a malfunction, indefinite information is written on the optical disc. If this is performed on an optical disc on which information has already been recorded, so-called double writing will occur and the recorded information will be destroyed.

In order to prevent such destruction of recorded information on an optical disc, the level of reflected light from the already recorded area, that is, the area where pits are formed, is lower than that from the unrecorded area. Taking advantage of the property of being low,
One idea is to photoelectrically convert the light reflected from the optical disk during recording, similar to when playing back, and determine that double writing is occurring when a low-level signal is detected in the photoelectrically converted playback signal. ing.

FIG. 4 shows the configuration of a circuit that photoelectrically converts the reflected light from such an optical disk to binarize it. In the figure, a photodetector 12 photoelectrically converts reflected light from an optical disk and outputs a photocurrent. Note that the photodetector 12 shown in FIG. 4 shows, for example, one photodetection cell 12a of a four-part photodetector. The other three photodetectors have been omitted to simplify the explanation. The photocurrent photoelectrically converted by the photodetector 12 is converted into a voltage signal by a current-voltage conversion circuit 40 composed of an operational amplifier 40a and a resistor Ro. One of these voltage signals is connected to the operational amplifier 41a1 resistor R,
, R, and is amplified by an amplifier circuit 41 and supplied to the adder 23.

In addition to the photodetection cell 12a, the adder 23 inputs and adds signals from three other photodetection cells (not shown) of the above-mentioned 4-split photodetector. This adder 23
The added signal corresponds to the information stored on the optical disc, and is supplied to the video signal binarization circuit 24. The video signal is then binarized by the video signal binarization circuit 24 and sent as a reproduction signal to a control section (not shown) for display or the like.

The other voltage signal outputted from the current-voltage conversion circuit 40 is amplified by an amplifier circuit 42 composed of an operational amplifier 42a, resistors R1, R4 and R5, and is supplied to an adder 29. In addition to the photodetection cell 12a, the two adders input and add signals from three other photodetection cells (not shown) of the above-mentioned 4-split photodetector. This adder 2
The signal added in step 9 corresponds to the reflected light from the optical disc, and is supplied to the recording signal binarization circuit 30.

The signal is then binarized by a recording signal binarization circuit 30, and sent as a recording light reproduction signal to a control section (not shown), where it is used for double writing detection.

In this way, conventional optical disk devices equipped with a double writing prevention function are equipped with separate amplification circuits 41 and 42 for playback and recording, which increases the amount of hardware, increases the size of the device, and increases costs. The drawback was that it was inviting high prices.

(Problems to be Solved by the Invention) As described above, the conventional optical disc device equipped with a double writing prevention function is equipped with separate amplification circuits for playback and recording. This was done in order to eliminate the drawbacks of increased device size and higher cost due to the increase in the number of optical discs, and to provide a small and low-cost optical disk device that achieves a double-write prevention function with a small amount of hardware. The purpose is to

[Structure of the Invention] (Means for Solving the Problems) The optical disk device of the present invention includes a light output means for emitting a light beam, and a detection means for detecting reflected light of the light beam emitted from the light output means. , a selection means for selecting whether to amplify the signal detected by the detection means by a first amplification factor or a second amplification factor; and a first or second amplification factor selected by the selection means. an amplification means for amplifying the signal detected by the detection means; and a first binarization for binarizing the signal amplified by the first amplification factor by the amplification means to obtain reproduction information of the reproduction light beam. and a second binarization unit that binarizes the signal amplified by the amplification unit at the second amplification factor to obtain reproduction information of the recording light beam.

(Function) The present invention detects the reflected light of the light beam emitted from the optical output means, and when the detected reflected light is due to the reproduction light beam, the first amplification factor is set; If so, select amplification using the second amplification factor, 'perform appropriate amplification for each light beam with this selected amplification factor, and then binarize this amplified signal. This is what I did. In this way, the amplification factor of one amplification means is selected to perform amplification suitable for each light beam, so
This makes it possible to reduce the amount of deware.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. Note that parts equivalent to those of the conventional example will be described with the same reference numerals.

FIG. 2 shows a schematic configuration of the optical disc device of the present invention. In the figure, an optical disk 1 is formed by coating a metal film layer of tellurium, bismuth, or the like in a donut shape on the surface of a circularly molded substrate made of, for example, glass or plastic.

The optical disc 1 is rotated by a spindle motor 2. The spindle motor 2 is
A motor control circuit (not shown) that operates in response to a control signal from the control circuit 3 controls the start and stop of rotation, the number of rotations, and the like.

The control circuit 3 is composed of, for example, a microcomputer, and in addition to controlling the rotation of the spindle motor 2,
It includes circuits that manage various controls described below.

An optical head 4 is disposed below the optical disc 1 . This optical head 4 records or reproduces information on the optical disc 1, and includes a semiconductor laser oscillator 5, a collimator lens 6, and a polarizing beam splitter 7.
, objective lens 8, cylindrical lens 9 and convex lens 1
The astigmatism optical system includes a well-known astigmatism optical system 11, a 4-split photodetector 12, a photodetector 13, and the like. The optical head 4 is disposed so as to be movable in the radial direction of the optical disc 1 by a moving mechanism (not shown) constituted by, for example, a linear motor, and is configured to record or reproduce objects according to control signals from the control unit 3. It is now possible to move to the target track.

The semiconductor laser oscillator 5 generates a diverging laser beam (light beam) according to the drive signal S1 from the optical output control circuit 14, and transmits information to the recording film 1 of the optical disc 1.
When recording on the optical disc 1, a strong laser beam whose light intensity is modulated according to the information to be recorded is generated, and when information is read and reproduced from the recording film 1a of the optical disc 1, the laser beam has a constant light intensity. It is designed to generate weak laser light.

The diverging laser beam generated by the semiconductor laser oscillator 5 is converted into a parallel beam by a collimator lens 6 and guided to a polarizing beam splitter 7. The laser beam guided by the polarizing beam splitter 7 passes through the polarizing beam splitter 7 and enters the objective lens 8, and is focused by the objective lens 8 toward the recording film 1a of the optical disc 1.

The objective lens 8 is supported movably in the forward axis direction by a lens actuator 15 as a lens drive mechanism. By being moved in the optical axis direction by the servo signal S2 from the focus servo circuit 16, the focused laser beam that has passed through the objective lens 8 is projected onto the surface of the recording film 13a of the optical disc 1, and the minimum beam A spot is formed on the surface of the recording film 1a of the optical disc 1. In this state, the objective lens 8 is in a focused state.

The objective lens 8 is also movable in a direction perpendicular to the optical axis, and is moved in the direction perpendicular to the optical axis by a servo signal from a tracking servo circuit (not shown). It has become. Then, the focused laser beam that has passed through the objective lens 8 is projected onto the surface of the recording film 1a of the optical disc 1, and is irradiated onto the recording tracks formed on the surface of the recording film 1a of the optical disc 1. It has become. In this state, the objective lens 8 is in a matching track state. In the focused point and focused track state, information can be written and read.

On the other hand, the diverging laser beam reflected from the recording film 1a of the optical disc 1 is converted into a parallel beam by the objective lens 8 when it is focused, and is returned to the polarizing beam splitter 7 again. Then, it is reflected by this polarizing beam splitter 7 and guided onto a 4-split photodetector 12 by an astigmatism optical system 11 consisting of a cylindrical lens 9 and a convex lens 10, and an image is formed in a state where defocus appears as a change in shape. It is now possible to do so. The four-split photodetector 12 is composed of four photodetection cells that convert the light imaged by the astigmatism optical system 11 into electrical signals.

Two sets of signals output from two photodetection cells arranged diagonally to each other in this four-split photodetector 12 are supplied to amplifiers 17 and 18, respectively.

The four-force spout circuit 16 includes an error amplifier 19 which inputs the two signals amplified by the amplifiers 17 and 18 and performs error amplification, a phase correction circuit 20 which corrects the phase of the output signal of one of the error amplifiers, and a phase correction circuit 20 which corrects the phase of the output signal of one of the error amplifiers. An analog switch 21 that controls whether to supply the output signal of the correction circuit 20 to the driver 22, and a driver 2 that amplifies the signal from the analog switch 21 and drives the actuator 15.
2. When this analog switch 21 is turned on by the focus on/off signal S3 from the control circuit 3, a focus servo loop is formed by supplying the signal from the phase correction circuit 20 to the actuator 15 via the driver 22. It has become so.

Further, the output signals from the amplifiers 17 and 18 are supplied to adders 23 and 29. The signal added by the adder 23 is added to the optical disc 1 during playback operation.
It reflects the recorded contents of , and is supplied to the video signal binarization circuit 24 .

The video signal binarization circuit 24 is composed of, for example, a comparator, and performs binarization by comparing the analog signal output from the adder 23 with a predetermined threshold level Thl. The reflected light signal S4 binarized by the video signal binarization circuit 24 is supplied to the control circuit 3. And control circuit 3
After being subjected to predetermined processing, the signal is sent as a reproduction signal to a host device (not shown).

Further, the signal added by the adder 29 reflects the recorded content of the optical disc 1 during the recording operation, and is the third signal.
It is output as a waveform signal as shown in the figure. In other words, during normal recording in which recording is performed in a non-recording area, as shown in Fig. 3 (
As shown in Fig. 3(b), a signal having a signal level ten times higher than the signal level during reproduction is obtained, but when recording in an already recorded area, so-called double writing, as shown in Fig. 3(b). As shown in FIG. 2, many signals having a signal level several times higher than the signal level during reproduction can be obtained. This is because the recording light beam is irradiated onto a portion where a pit has already been formed, so the amount of reflected light is reduced at that bit portion. The output signal of the adder 29 having such a waveform is sent to a recording signal binarization circuit 30. The recording signal binarization circuit 30 is constituted by, for example, a comparator, and performs binarization by comparing the analog signals output from the two adders with a predetermined threshold level Th2. This threshold level Th
2 is set as a signal having a lower level than the reflected light signal level when recording on an unrecorded area and higher than the reflected light signal level when recording on an already recorded area. The reflected light signal S8 binarized by the recording signal binarization circuit 30 is supplied to the control circuit 3.

The control circuit 3 receives the reflected light signal S8 output from the recording signal binarization circuit 30 and detects double writing. That is, if the optical disc 1 to be recorded is unrecorded, a significant signal should be obtained from the recording binarization circuit 30 corresponding to the recording data S10. Therefore, the control circuit 3 checks whether or not there is a one-to-one correspondence between the recorded data S11 and the reflected light signal S8 from the recorded signal binarization circuit 30, and the reflected light signal S8 corresponding to the recorded data S10 is If it is not obtained, it is detected that there is double writing.

The detection result is then supplied to a counter (not shown), which counts the number of double writing detections, and when the number of double writing detections exceeds a predetermined value, the recording operation is prohibited. The reason why recording is prohibited when a predetermined value or more is detected is because the reflective film is missing from the beginning, such as a pinhole on the optical disc 1, or an unrecorded area. Even if it is, double writing will be detected, resulting in false detection.

The above predetermined value is determined as follows. In other words, the upper limit of the predetermined value is regulated by the burst error correction capability of the device. This is because recording must be stopped before data destroyed by double writing can be repaired by an error correction circuit (not shown).

On the other hand, the lower limit of the predetermined value is determined by the allowable range of defects such as pinholes on the optical disc 1. In other words, when recording on a defective area on the optical disc 1, the above-mentioned double writing will continue to be detected, but if recording is prohibited before passing through the defective area, a false detection will occur, so this is acceptable. The predetermined value must be greater than the minimum possible value.

The waveform shaping circuit 32 receives recording data S10 supplied from a host device (not shown) via the control circuit 3, and outputs a waveform-shaped recording pulse signal S7. This recording pulse signal S7 is transmitted to the last week control circuit 1 which will be described later.
The signal is supplied to the driver 28 of No. 4.

Here, a more detailed configuration of the amplifiers 17 and 18 will be explained with reference to FIG. In the figure, the photodetector 12 photoelectrically converts the reflected light from the optical disk, as described above, and outputs a photocurrent. In addition, the first
The photodetector 12 shown in the figure is, for example, one photodetection cell 12a of a four-part photodetector. The other three photodetectors have been omitted to simplify the explanation. Photodetector 12
The photocurrent photoelectrically converted is converted into a voltage signal by a current-voltage conversion circuit 40 comprising an operational amplifier 40a and a resistor R0. This voltage signal is applied to the operational amplifier 50a1 resistor R
+, R2, R3, R4, and an amplifier circuit 50 including an analog switch 51, and then supplied to adders 23 and 29.

The analog switch 51 is controlled by a control signal from the control circuit 3 to be turned off during playback and turned on during recording. Now, when compared with the conventional circuit shown in FIG. 4, when the analog switch 51 is turned off, the circuit becomes approximately equivalent to the amplifier circuit 41 shown in FIG. 4, and when the analog switch 51 is turned on, In this case, the circuit becomes equivalent to the amplifier circuit 42. Note that the resistance R2 has the same resistance value as the conventional one, and the resistance value of the resistance R1 is selected so as to satisfy 1/Rs-1/R2+1/R3 (1).

In addition to the photodetection cell 12a, the adders 23 and 2 include:
Signals from other three photodetection cells (not shown) of the above-mentioned four-division photodetector are input and added. The signal added by the adder 23 corresponds to information stored on the optical disc, and is added by the video signal binarization circuit 2.
4. The video signal is then binarized by the video signal binarization circuit 24, and sent as a reproduction signal to the control circuit 3 for display or the like. Further, the signal added by the two adders corresponds to the reflected light from the optical disc, and is supplied to the recording signal binarization circuit 30. The recording signal is then binarized by the recording signal binarization circuit 30 and sent to the control circuit 3 as a recording light reproduction signal, where it is used for double writing detection.

Further, a photodetector 13 constituted by a photoelectric conversion element such as a photodiode, which is provided facing a light emitting port opposite to a light emitting port for recording or reproducing laser light of the semiconductor laser oscillator 5, is configured by a photoelectric conversion element such as a photodiode. When the monitor light from the laser oscillator 5 is irradiated, the monitor light is converted into an electric signal (photocurrent) and supplied to the light output control circuit 14 as the light output monitor signal S5 of the semiconductor laser oscillator 5. ing.

The optical output control circuit 14 controls the optical output of the semiconductor laser oscillator 5 to keep it constant by inputting the optical output monitor signal S5 output from the semiconductor laser oscillator 5 and performing feedback control. That is, the current-voltage conversion circuit 25 inputs the optical output monitor signal S5 photoelectrically converted by the photodetector 13 and extracted as a current signal, and converts the light intensity received by the photodetector 13, that is, the light of the semiconductor laser oscillator 5. It converts into a voltage signal S6 according to the output and outputs it. The voltage signal S6 output from this current-voltage conversion circuit 25 is supplied to an error amplifier 261.

The error amplifier 26 uses the voltage signal S6 as one input and a reference voltage Vs generated by a constant voltage source (not shown) as the other input, compares the two types of pressures S6 and Vs, and amplifies the difference. This is output as an error signal. The reference voltage Vs is a constant voltage for obtaining the optical output necessary for reproduction, and the voltage signal $6 is applied to the reference voltage Vs.
By feedback control to bring it closer to
A constant optical output can be obtained from the semiconductor laser oscillator 5. The error signal from the error amplifier 26 is supplied to a driver 28.

The driver 28 is supplied with a recording pulse signal S7 corresponding to the information to be recorded from the above-mentioned waveform shaping circuit 32, so that the optical output for recording is output from the semiconductor laser oscillator 5. It is now possible to do so. Note that the voltage signal output from the error amplifier 26 is input to the driver 28 during reproduction, and the voltage signal output from the error amplifier 26 is input to the driver 28 during recording.
A voltage signal is input in which the voltage value input during the previous playback is held in a sample-and-hold circuit (not shown), and these two inputs can be switched depending on whether recording or playback is being performed. It has become. In both recording and reproduction, feedback control is performed based on the level of optical output during reproduction.

Next, the operation of the optical disc device configured as described above will be explained.

First, before performing a recording operation, an initial operation is performed to check the validity of the light emission output of the semiconductor laser oscillator 5. That is, a linear motor (not shown) is driven by a control signal from the control circuit 3, and the objective lens 8 is made to face the non-recorded area of the optical disc 1. This non-recording area is provided on the innermost or outermost side of the optical disc 1, and is a portion where no information is recorded. By initially moving the optical head 4 to such a position, even if the laser beam is abnormally emitted for some reason, the low recorded data will not be destroyed.

Next, the analog switch 21 is turned off by outputting the focus on/off signal S3 from the control circuit 3. As a result, the focus servo loop is disconnected, and the objective lens 8 is released from focusing control. Next, a signal (not shown) for forcibly moving the lens actuator 15 is sent from the control circuit 3 to the driver 2.
2 to the lens actuator 15. As a result, the objective lens 8 is forcibly moved to the position shown by the dotted line in FIG. 1, creating a defocused state. In this defocused state, power is supplied to the optical output control circuit 14 to turn on the semiconductor laser oscillator 5 and start outputting a laser beam. As a result, the monitor light generated from the semiconductor laser oscillator 5 is converted into a current according to the light output by the photodetector 13 and output as a light output monitor signal S5. The current-voltage conversion circuit 25 is
This optical output monitor signal S5 is converted into a voltage signal S6 and supplied to the error amplifier 26. The error amplifier 26 compares the preset reference voltage Vs and the voltage signal S6,
The error amount is output as an error signal. This error signal is a signal that "reduces the optical output of the semiconductor laser oscillator 5 if the voltage signal S6>reference signal VsJ, and increases the optical output of the semiconductor laser oscillator 5 if the voltage signal S6<reference signal VsJ". This error signal is sent to the driver 281;
By supplying the voltage, a feedback loop is formed and the reference voltage Vs is controlled to be equal to the voltage signal S6, thereby keeping the optical output of the semiconductor laser oscillator 5 constant.

Next, the control circuit 3 drives the actuator 15 via the driver 22 to move the objective lens 8 toward the in-focus position. When it is detected that the in-focus position has been reached, the analog switch 21 is turned on, the focus servo loop is connected, and the initial operation is completed. Thereafter, automatic focus control is performed by a focus servo loop, and normal operations such as reading and writing information from the optical disc 1 are performed.

In such a state, the recording operation is performed as follows. That is, first, prior to the recording operation, the analog switch 51 is turned on by a control signal from the control circuit 3. Next, the recording data sent from the host device (not shown) is supplied to the control circuit 3.
Pulsed recording data SIO is output from. This recording data S10 is supplied to the waveform shaping circuit 32 and further supplied to the driver 28. As a result, the semiconductor laser oscillator 5 emits intermittent high-output laser light according to the recording data SIO. This laser light is converted into a parallel beam by a collimator lens 6 and guided to a polarizing beam splitter 7. The laser beam guided by the polarizing beam splitter 7 passes through the polarizing beam splitter 7 and enters the objective lens 8, and is focused by the objective lens 8 toward the recording film 1a of the optical disc 1. Information is thereby recorded on the recording film la.

Further, double writing is detected in parallel with the above recording operation. That is, the diverging laser beam reflected from the recording film 1a of the optical disc 1 during recording is converted into a parallel beam by the objective lens 8, and is returned to the polarizing beam splitter 7 again. Then, it is reflected by this polarizing beam splitter 7 and imaged onto a four-split photodetector 12 by an astigmatism optical system 11 consisting of a cylindrical lens 9 and a convex lens 10 . At this time, the optical disc 1 that is being written to
If the area has already been recorded, reflected light waveforms with different light intensity levels are obtained, as shown in FIG. 3(b). Signals photoelectrically converted by this four-split photodetector 12 are supplied to amplifiers 17 and 18, respectively. and,
One of the signals amplified by the amplifiers 17 and 18 is supplied to the focus servo circuit 16 below the error amplifier 19 and used for focusing control. Further, the other of the signals amplified by the amplifiers 17 and 18 is supplied to two adders to perform addition, and then supplied to the recording signal binarization circuit 30.

The recording signal binarization circuit 30 outputs a binarized reflected light signal S8 by comparing the signal from the adder 29 with a predetermined threshold level Th2. At this time, the reflected light of the laser light irradiated onto the already formed bits is small, so it does not appear as significant data. This reflected light signal S8 is then supplied to the control circuit 3.

Then, the control circuit 3 counts the number of pulses that do not appear as significant data, and prohibits the recording operation when a predetermined value is counted. This prevents double writing.

On the other hand, the reproduction operation is performed as follows. That is, first, prior to the reproduction operation, the analog switch 51 is turned off by a control signal from the control circuit 3. Next, the voltage held in the sample hold circuit (not shown) is applied to the driver 2.
8, the semiconductor laser oscillator 5 emits laser light with a constant level of low optical output. This laser light is converted into a parallel beam by a collimator lens 6 and guided to a polarizing beam splitter 7. The laser beam guided by the polarizing beam splitter 7 passes through the polarizing beam splitter 7 and enters the objective lens 8, and is focused by the objective lens 8 toward the recording film 1a of the optical disc 1. Then, the diverging laser beam reflected from the recording film 1a of the optical disk 1 is converted into a parallel beam by the objective lens 8, and is returned to the polarizing beam splitter 7 again.

The light beam is then reflected by the polarizing beam splitter 7 and is imaged onto a four-split photodetector 1'2 by an astigmatism optical system 11 comprising a cylindrical lens 9 and a convex lens 10. The signal photoelectrically converted by this 4-split photodetector 12 is
are supplied to amplifiers 17 and 18, respectively. One of the signals amplified by the amplifiers 17 and 18 is supplied to the focus servo circuit 16 below the error amplifier 19, and is used for focusing control. The other of the signals amplified by the amplifiers 17 and 18 is supplied to an adder 23 for addition, and then supplied to a video digitization circuit 24. The video binarization circuit 24 outputs a binarized reflected light signal S4 by comparing the signal from the adder 23 with a predetermined threshold level Thl. This reflected light signal S4 is then supplied to the control circuit 3. The data is then sent to a host device (not shown) via the control circuit 3, where it is displayed, printed, etc.

As described above, the reflected light of the light beam emitted from the semiconductor laser oscillator 5 is photoelectrically converted, and if this photoelectrically converted reflected light is due to the light beam during reproduction, the analog switch 51 is turned off. amplification is performed with a first amplification factor by changing the resistance value, and when the recording light beam is used, the resistance value is changed by turning on the analog switch 51 and amplification is performed with a second amplification factor. Since this amplified signal is binarized, one operational amplifier 50a can perform amplification suitable for each light beam, and the amount of hardware can be reduced.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a small and low-cost optical disc device that realizes a double writing prevention function with a small amount of hardware.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention,
Fig. 1 is a circuit diagram showing the detailed configuration of the amplifier, Fig. 2 is a block diagram showing the schematic structure of the optical disk device, Fig. 3 is a waveform diagram for explaining the operation, and Fig. 4 is a conventional amplifier. FIG. 2 is a circuit diagram for explaining. DESCRIPTION OF SYMBOLS 1... Optical disk, 3... Control circuit, 4... Optical head, 5... Semiconductor laser oscillator (light output means),
12... Four-split photodetector (detection means), 13... Photodetector, 14... Optical output control circuit, 24... Video signal binarization circuit (first binarization means) , 30... Recording signal binarization circuit (second binarization means), 32... Waveform shaping circuit, 50... Amplification circuit (amplification means), 51...
- Analog switch (selection means). Figure Figure

Claims (1)

[Scope of Claims] A light output means for emitting a light beam; a detection means for detecting reflected light of the light beam emitted from the light output means; and a signal detected by the detection means by a first amplification factor. a selection means for selecting whether to amplify by a first amplification factor or a second amplification factor; and an amplification means for amplifying the signal detected by the detection means by a first or second amplification factor selected by the selection means. , first binarization means that binarizes the signal amplified by the first amplification factor by the amplification means to obtain reproduction information of the reproduction light beam; and amplification by the amplification means by the second amplification factor. 1. An optical disc apparatus comprising: second binarization means for binarizing the signal and converting the signal into reproduction information for a recording light beam.