JPH03116533A - Optical disk device - Google Patents

Abstract

PURPOSE:To prevent double writing without fail by comparing the reflected light of a pulse-shaped recording light beam from an optical disk with a prescribed threshold level and stopping a recording operation when the counted value of a pulse more than the prescribed level is more than a prescribed value. CONSTITUTION:The double write is detected by utilizing a property that as for the intensity of the reflected light of the pulse-shaped recording light beam a case the beam is reflected from a recorded area is different from a case that it is reflected from an unrecorded area. Namely, the pulse-shaped recording light beam is radiated from a light output means 5 and the reflected light is compared with the prescribed level. Then, the reflected more than the prescribed level is detected by a detecting means 30 and the number of the pulses more than the prescribed level is counted by a counting means 31. When the counted value is more than the prescribed value, it is judged that the area is the recorded area, and the recording operation is stopped. Thus, an optical disk device, which can prevent the double writing without fail, 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 an optical disc device that optically records or reproduces information on an optical recording medium such as a recordable or erasable optical disc, a semiconductor laser (light output means) is used as a light source. Information on the optical disc is read using a relatively small continuous optical output from the optical disc, while information is recorded on the optical disc using a relatively large optical output that intermittently changes over a predetermined value. Therefore, if an optical disc is irradiated with a light output that exceeds the above-mentioned predetermined value, even if it is not intended to be recorded, undefined information will be written on the optical disc, destroying information that has already been recorded. become.

For example, Japanese Patent Application No. 10097/1987 is used to prevent the destruction of information already recorded on such optical discs.
There are some disclosed in 6.

This method determines that double writing is occurring when a low recorded portion is detected in the reproduced signal during recording.

FIG. 4 shows a waveform of light reflected from an optical disc in such an optical disc device. FIG. 4(a) shows a reflected light waveform during reproduction. A relatively small optical output is obtained, and a high-level part (bright part) exists at a position corresponding to the recorded part, and this becomes significant data. FIG. 5B shows a reflected light waveform in a normal state, that is, when data is recorded in a non-recording area. A pulse-like waveform with a relatively large optical output corresponding to the recorded data can be obtained. Furthermore, the same figure (C) shows the reflected light waveform at the time of double writing. A waveform is obtained in which the reflected light waveform during reproduction and the reflected light waveform during normal recording are superimposed. Then, the reflected light waveform shown in FIG. 4(C) is compared with predetermined threshold levels Thl and Th2.
When detecting data that is larger and smaller than Th2, that is, the presence of a green portion (bright portion), it is determined that double writing has occurred. In other words, it is determined whether the area currently being recorded is an unrecorded area or a low recording area, depending on whether a signal corresponding to the green area is included in the playback signal during recording. This is designed to prevent double writing.

However, the playback signal during recording becomes unstable due to the influence of, for example, undershoot of the recording beam, resulting in false detection or omission of detection, which has the disadvantage that double writing cannot be reliably prevented. Ta.

(Problem to be Solved by the Invention) As described above, the present invention detects whether the area is an unrecorded area or a low recording area using the reproduction signal during recording. This was done to eliminate the drawback that double writing cannot be reliably prevented due to the unstable state caused by the influence of the recording beam, resulting in false detections and omissions.This was done to prevent false detections and omissions. An object of the present invention is to provide an optical disc device that can reliably prevent double writing by IE.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, an optical disk device of the present invention includes a light output means for emitting a pulsed recording light beam and a light emitted from the light output means. a detection means for detecting the reflected light of the recording light beam; a counting means for counting the number of pulses in which the reflected light detected by the detection means is equal to or higher than a predetermined level; and when the counting means counts a predetermined value; It is characterized by comprising a control means for stopping emission of the recording light beam from the light output means.

(Function) The present invention is characterized in that the magnitude of the reflected light of the pulsed recording light beam output from the optical output means is different depending on whether it is reflected from a low recording area or when it is reflected from an unrecorded area. This method detects double writing by emitting a pulsed recording light beam from the optical output means and comparing the reflected light of this pulsed recording light beam with a predetermined level. The reflected light is detected by a detection means, the number of pulses exceeding a predetermined level is counted by a counting means, and when the counted value exceeds a predetermined value, the area is determined to be a low recording area and a recording operation is performed. It was designed to stop. In this way, since the magnitude of the reflected light of the recording light beam is detected, which is relatively stable, stable detection is possible, and double writing is determined after detecting multiple reflected lights of a predetermined level or higher. This makes it possible to reliably prevent double writing.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of an optical disc device as an information recording device of the present invention. In the figure, an optical disk (optical recording medium) 1 is formed by coating a donut-shaped coating layer such as an amorphous thin film or an organic dye film 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. This 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 (control means) 3 is constituted by, for example, random logic, and includes circuits for controlling the rotation of the spindle motor 2 as well as various other controls to be described later.

An optical head 4 is disposed below the first disk 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 is composed of 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 a target for recording or reproduction according to instructions from the control unit 3. It is now moved to the target track.

The semiconductor laser oscillator (light output means) 5 generates a diverging laser beam (light beam) according to the drive signal S1 from the optical output control circuit 14, and records information on the recording film 1a of the optical disc 1. When reading and reproducing information from the recording film 1a of the optical disc 1, a weak laser beam with a constant light intensity is generated. It is designed to generate 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 polarized beam splitter passes through the polarized 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 direction of its optical axis 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 1.a of the optical disc 1. The minimum beam 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 disk 1 is converted into a parallel beam by the objective lens 8 when it is focused, and is returned to the polarized beam splitter 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 with each other in this four-split photodetector 12 are supplied to amplifiers 17 and 18, respectively.

The focus servo circuit 16 includes an error amplifier 19 that inputs the two signals amplified by the amplifiers 17 and 18 and performs error amplification, a phase correction circuit 20 that corrects the phase of the output signal of the error amplifier 19, and a phase correction circuit 20 that corrects the phase of the output signal of the error amplifier 19. An analog switch 21 that controls whether or not to supply the output signal of the circuit 20 to the driver 22, and a driver 2 that amplifies the signal from the analog switch 21 and drives the actuator 21.
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 an adder 23. The signal added by the adder 23 reflects the recorded content of the optical disc 1, and is output as a waveform signal as shown in FIG. In other words, during normal recording in a non-recording area, a signal with a signal level ten times higher than the signal level during playback is obtained, as shown in Figure 3(a), and recording in a low recording area is obtained. When performing so-called double writing, see Figure 3 (
As shown in b), many signals having a higher signal level than the signal level during normal recording are obtained. This is because since the recording light beam is irradiated onto a location that has already been recorded, the amount of reflected light increases at that location. The output signal of the adder 23 having such a waveform is sent to the binarization circuit 24.

The 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 Th. This threshold level Th is set as a signal that is higher than the reflected light signal level when recording is performed in an unrecorded area, and lower than the reflected light signal level when recorded in a low recording area. A signal with a level higher than the threshold level Th is not treated as significant data. The reflected light signal S4 binarized by the binarization circuit 24 is supplied to the detection circuit 30.

The detection circuit (detection means) 30 receives the recording data S11 and the reflected light signal S4 outputted from the binarization circuit 24, and generates a double writing detection signal S8. That is, if the optical disc 1 to be recorded is unrecorded, the binarization circuit 2
4, a significant signal should be obtained. Therefore, the detection circuit 30 checks whether the recorded data S11 and the reflected light signal S4 from the binarization circuit 24 have a one-to-one correspondence.
A double writing detection signal S8 is output when the reflected light signal S4 corresponding to the recording data S11 is not obtained. The double writing detection signal S8 from this detection circuit 30 is
The signal is supplied to a counter circuit 31.

The counter circuit (counting means) 31 counts the number of times the double writing detection signal S8 outputted by the detection circuit 30 is generated, and outputs a recording prohibition signal S9 when the number exceeds a predetermined value. The reason why the recording inhibit signal S9 is output when it is detected that the value exceeds a predetermined value is because, for example, if there is a part of the optical disc 1 whose reflectance has changed due to crystallization or organization from the beginning, it may be impossible to record. This is because the double writing detection signal S8 is output even in the area, 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, please follow the above 2.
The overwriting detection signal S8 continues to be output, but if the recording prohibition signal S9 is output before passing the defective part, a false detection will occur, so the above predetermined value must be at least the minimum allowable value. . The recording inhibit signal S9 from this counter circuit 31 is supplied to an AND gate 33.

Note that the counter circuit 31 is supplied with a clear signal S12 from the control circuit 3 to reset the counter.

The AND gate 33 receives the recording data S10 supplied from an external device (not shown) via the control circuit 3 as one input, and receives the recording prohibition signal S9 outputted from the counter circuit 31.
is used as the other input to output recording data S11 whose prohibition/permission is controlled. This recorded data S11 is supplied to a waveform shaping circuit 32, a detection circuit 30, and a counter circuit 31. Waveform shaping circuit 32
formats the recorded data 811 and sends it to the driver 28, which will be described later.
It is intended to supply

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 that has been charged and converted by the photodetector 13 and taken out 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. A voltage signal S6 outputted from this current-voltage conversion circuit 25 is supplied to an error amplifier 26.

The error amplifier 26 uses the voltage signal S6 as one input and the 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 S6 is converted to the reference voltage Vs.
By feedback control to bring it closer to
A constant output is 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 suppressing double writing during recording in the optical disc device configured as described above will be described with reference to the timing chart of FIG. 2.

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. In other words, the focus on/off signal S3 is sent from the control circuit 3.
By outputting , the analog switch 21 is turned off. This disconnects the focus servo loop and
The objective lens 8 is released from forcing control.

Next, a signal (not shown) for forcibly moving the lens actuator 15 is supplied from the control circuit 3 to the lens actuator 15 via the driver 22 . 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 converts this optical output monitor signal S5 into a voltage signal S6,
Error amplifier 26 is supplied.

In the error amplifier 26, a preset reference voltage Vs
and the voltage signal S6, and output the error amount 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". By supplying this error signal to the driver 28, a feedback loop is formed and the reference voltage Vs and the voltage signal S6 are
The optical output of the semiconductor laser oscillator 5 is thereby kept 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 determined that the in-focus position has been reached, the analog switch 21 is turned on to connect the focus servo loop and complete the initial operation. 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 this state, as shown in Figure 2(a),
The control circuit 3 outputs pulsed recording data SIO. At this time, the recording inhibit signal S9 output from the counter circuit 31 is initially set to a high level by supplying the clear signal S12 from the control circuit 3. Therefore, the recording data S10 is supplied to the waveform shaping circuit 32 via the AND gate 33, 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 S10. 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 to the polarizing beam splitter 7 passes through the polarizing beam splitter 7 and enters the objective lens 8.
The objective lens 8 focuses the light toward the recording film 1a of the optical disc 1. Information is thereby recorded on the recording film 1a.

On the other hand, the diverging laser beam reflected from the recording film 1a of the optical disk 1 during the recording operation is converted into a parallel beam by the objective lens 8 and 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, if the area of the optical disc 1 to which writing is being performed is an area that has already been recorded, as shown in FIG. 2(b).
As shown in the figure, reflected light waveforms with different light intensity levels are obtained. Signals photoelectrically converted by this four-split photodetector 12 are supplied to amplifiers 17 and 18, respectively. Then, one of the signals amplified by the amplifiers 17 and 18 is supplied to the focus servo circuit 16 below the error amplifier 19,
Used for force control. In addition, the amplifier 17
The other of the signals amplified in and 18 is supplied to an adder 23 for addition, and then supplied to a binarization circuit 24.

As shown in FIG. 3, the binarization circuit 24 includes the adder 2
By comparing the signal from 3 with a predetermined threshold level Th, a binarized reflected light signal S4 as shown in FIG. 2(C) is output. At this time, since the reflected light of the laser beam irradiated onto the already recorded portion is greater than the threshold level Th, it is not treated as significant data (the middle dotted line portion in FIG. 2(c)). This reflected light signal S4 is then supplied to the detection circuit 30.

The detection circuit 30 includes a flip-flop (not shown), which is set at the rising edge of the recording data S11 output from the AND gate 33 and reset at the rising edge of the reflected light signal S4. It is.

The output of this flip-flop is output from the detection circuit 30 as a double write detection signal S8, as shown in FIG. 2(d).

The counter circuit 31 inputs the double write detection signal S8, captures the level of the double write detection signal S8 at the falling edge of the recording data Sll, which is the other input, and outputs a count pulse of a built-in counter (not shown). (Figure 2 (
e). This count pulse is counted by a counter, and when a predetermined value is counted, the recording prohibition signal S9 is set to a low level. As a result, one input of the AND gate 33 becomes low level, and the output of the recording data S10 is suppressed. Therefore, from then on, the recording data S11 is not output, the output of the waveform shaping circuit 32 is also suppressed, and recording on the optical disc 1 is prohibited. The recording prohibited state will be maintained until the clear signal S12 from the control circuit 3 is output. This prevents double writing.

In this way, instead of immediately determining that double writing is occurring when a large amount of reflected light from the previous disk 1 is detected, it is determined that double writing is occurring when a predetermined number or more of large amounts of reflected light are detected. This makes it possible to significantly reduce false positives and missed positives.

Furthermore, until a predetermined number or more of the large amount of reflected light from the optical disc 1 is detected, data in the low recording area will be destroyed, but the amount of data destroyed is set so that it is within the error correctable range. The reliability of the recorded data is not compromised.

As described above, when the pulsed recording light beam output from the semiconductor laser oscillator 5 is reflected by the optical disc 1, the magnitude of the reflected light differs between when it is reflected from an already recorded area and when it is reflected from an unrecorded area. Taking advantage of the property that the pulsed recording light beam is different from that when reflected from the optical disc 1, the semiconductor laser oscillator 5 emits a pulsed recording light beam, and the recording light beam is reflected by the optical disk 1 to a predetermined threshold level. The comparison is made into a binary signal, and a detection circuit 30 detects pulses of a predetermined level or higher from this binarized signal.The counter circuit 31 counts the number of pulses of a predetermined level or higher, and the counted value becomes a predetermined value. When the recording light beam exceeds this level, it is determined that the area is a low recording area and the recording operation is stopped, so the size of the reflected light of the relatively stable recording light beam is detected, and the recording operation becomes stable. In addition, double writing is determined after detecting a plurality of reflected lights of a predetermined level or higher, so double writing can be reliably prevented.

In the above embodiment, the detection circuit 30 uses the rising and falling edges of the recording data 510 (Sll).
, the case where the counter circuit 31 and the like are operated has been described, but the phase of the recording data 5IO (Sll) and the reflected light signal S4 changes depending on the recording method and the configuration of the waveform shaping circuit 32, so the recording method and waveform If the operation timing is changed as appropriate depending on the configuration of the shaping circuit 32, the same effects as in the above embodiment can be achieved.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide an optical disc device that can prevent false detections and omissions in detection and reliably prevent double writing.

[Brief explanation of drawings]

1 to 3 show an embodiment of the present invention,
FIG. 1 is a block diagram showing a schematic configuration of an optical disk device.
Figure 2 is a timing chart for explaining the operation, Figure 3 is a diagram for explaining the state of reflected light during normal recording and double writing, and Figure 4 is a diagram for explaining the conventional double writing prevention. FIG. 3 is a diagram for explaining the operation. 1... Optical disk, 2... Spindle motor, 3.
...Control circuit (control means) 4...Optical head, 5.
... Semiconductor laser oscillator (light output means), 8... Objective lens, 12... 4-split photodetector, 13... Photodetector, 14... Light output control circuit, 15... Lens Actuator, 25... Current-voltage conversion circuit, 24... Binarization circuit, 30... Detection circuit (detection means), 31...
- Counter circuit (counting means) 32... Waveform shaping circuit, 33... AND gate (control means).

Claims (1)

[Scope of Claims] Light output means for emitting a pulsed recording light beam; detection means for detecting reflected light of the recording light beam emitted from the light output means; and said reflection detected by the detection means. It is characterized by comprising a counting means for counting the number of pulses in which the light is at a predetermined level or more, and a control means for stopping emission of the recording light beam from the light output means when the counting means has counted a predetermined value. optical disk device.