JP3066970B2 - Optical disk drive - Google Patents

Description

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

(Prior Art) Conventionally, in an optical disc apparatus that optically records or reproduces information on an optical recording medium such as a write-once or erasable optical disc, a comparison is made between a semiconductor laser (light output means) as a light source. While reading information on the optical disk with a continuously small optical output, information is recorded on the optical disk with an optical output that changes intermittently over a relatively large predetermined value. Therefore, if the optical output is radiated to the optical disk at a predetermined value or more, even if the optical output is not intended to be recorded, indefinite information is written on the optical disk and the already recorded information is destroyed. become.

As a device for preventing the destruction of information already recorded on such an optical disk, there is one disclosed in Japanese Patent Application No. 60-100976, for example. In this method, when a recorded portion is detected in a reproduced signal at the time of recording, it is determined that double writing is performed.

FIG. 4 shows a reflected light waveform from an optical disk in such an optical disk device. FIG. 7A shows a reflected light waveform at the time of reproduction. A relatively small light output,
Higher level part (bright part) at the position corresponding to the recorded part
Exist, which is significant data. FIG. 6B shows a reflected light waveform in a normal state, that is, when data is recorded in a non-recording area. A pulse-like waveform having a relatively large optical output corresponding to the recording data is obtained. FIG. 3C shows a 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.
The reflected light waveform shown in FIG. 4 (c) is compared with the predetermined threshold levels Th1 and Th2 to detect data larger than Th1 and smaller than Th2, that is, when the presence of a recorded portion (bright portion) is detected. It is determined to be double writing. That is, it is determined whether the currently recorded area is an unrecorded area or a recorded area based on whether or not a signal corresponding to a recorded part is included in a reproduction signal at the time of recording. It is designed to prevent overwriting.

However, since the reproduced signal at the time of recording becomes unstable due to the influence of, for example, undershoot of the recording beam, erroneous detection or omission of detection occurs, and there is a disadvantage that double writing cannot be prevented reliably. Was.

(Problems to be Solved by the Invention) The present invention, as described above, detects whether a recorded signal is an unrecorded area or a recorded area by using a reproduced signal at the time of recording. In order to eliminate the drawback that double writing cannot be reliably prevented due to the unstable state due to the influence of the recording beam, which caused false detection and omission of detection. And surely 2
It is an object of the present invention to provide an optical disk device capable of preventing double writing.

[Constitution of the Invention] (Means for Solving the Problems) An optical disk device of the present invention is an optical disk device for recording information by irradiating a light beam based on a pulse-like recording signal onto the optical disk. And a light output means for irradiating the optical disc with a light beam based on a pulse-like recording signal corresponding to recording information, and detecting a reflected light of the recording light beam emitted from the light output means from the optical disc. Detecting means for binarizing the reflected light detected by the detecting means, and comparing the reflected light with a predetermined level so that a signal having a level higher than a predetermined level is not treated as significant data. Conversion means, and detection means for generating a double-write detection signal from the signal binarized by the binarization means,
The double writing detection signal generated by this detecting means is counted,
Means for outputting a recording prohibition signal when the count value becomes equal to or more than a predetermined value. The data amount of the recording area irradiated with the light beam can be corrected while counting the double writing detection signal. Counting means set to be within a range, and control means for performing control to stop irradiation of the recording light beam by the light output means in response to a recording prohibition signal from the counting means. I do.

(Function) The present invention is characterized in that the magnitude of the reflected light of the pulsed recording light beam output from the light output means is different between the case where the reflected light is reflected from the recorded area and the case where the reflected light is reflected from the unrecorded area. When recording information on an optical disc, a light beam based on a pulse-like recording signal corresponding to the record information is irradiated from the light output means onto the optical disc. A reflected light of the recording light beam from the optical disc is detected, the detected reflected light is binarized, and the reflected light is compared with a predetermined level, and a signal having a level higher than a predetermined level is not treated as significant data. In this manner, a double-write detection signal is generated from the binarized signal, the generated double-write detection signal is counted, and the counted value is determined while counting the double-write detection signal. When the data amount of the recording area irradiated with the light beam is equal to or more than a predetermined value set so as to be in an error-correctable range, a recording prohibition signal is output. The control for stopping the irradiation of the recording light beam by the means is performed. As described above, since the magnitude of the reflected light of the recording light beam, which is relatively stable, is detected, stable detection can be performed, and the reflected light of a plurality of predetermined levels or more is detected, and then the double writing is determined. Therefore, double writing can be reliably prevented.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of an optical disk device as an information recording device of the present invention. In the figure, an optical disc (optical recording medium) 1 is formed by coating a substrate formed into a circular shape with, for example, glass or plastics on a surface of a substrate such as an amorphous thin film or an organic dye film in a donut shape. .

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

The control circuit (control means) 3 is composed of, for example, random logic or the like, and includes a circuit that performs various controls described below in addition to the rotation control of the spindle motor 2.

An optical head 4 is provided below the optical disc 1. The optical head 4 records or reproduces information on or from the optical disk 1, and includes a semiconductor laser oscillator 5, a collimator lens 6, a polarizing beam splitter 7, an objective lens 8, a cylindrical lens 9, and a convex lens.
Well-known astigmatism optical system consisting of 10
12 and a photodetector 13 and the like. The optical head 4 is provided so as to be movable in the radial direction of the optical disk 1 by a moving mechanism (not shown) constituted by, for example, a linear motor, and is subjected to recording or reproduction in accordance with an instruction from the control unit 3. It will be moved to the target track.

The semiconductor laser oscillator (light output means) 5 generates divergent laser light (light beam) according to the drive signal S1 from the light output control circuit 14, and records information on the recording film 1a of the optical disc 1. When the information is to be recorded, a strong laser beam whose light intensity is modulated according to the information to be recorded is generated. When the information is read out from the recording film 1a of the optical disc 1 and reproduced, a weak laser beam having a constant light intensity is generated. Is caused to occur.

The divergent laser light generated from the semiconductor laser oscillator 5 is converted into a parallel light beam by the collimator lens 6 and guided to the polarization beam splitter 7. The laser beam guided to the polarization beam splitter 7 is transmitted through the polarization beam splitter 7 and is incident on the objective lens 8, where the laser light is focused toward the recording film 1 a of the optical disc 1.

The objective lens 8 is supported by a lens actuator 15 as a lens driving mechanism so as to be movable in the optical axis direction. When the laser beam is moved in the optical axis direction by the servo signal S2 from the focus servo circuit 16, the converging laser light passing through the objective lens 8 is projected on the surface of the recording film 1a of the optical disk 1, and the minimum beam The 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. The objective lens 8 is moved in a direction perpendicular to the optical axis by a servo signal from a tracking servo circuit (not shown). Has become. And
The converging laser light passing through the objective lens 8 is projected onto the surface of the recording film 1a of the optical disk 1, and is irradiated onto the recording track formed on the surface of the recording film 1a of the optical disk 1. ing. In this state, the objective lens 8 is in the combined track state. In the focused state and the focused track state, information can be written and read.

On the other hand, the divergent laser light reflected from the recording film 1a of the optical disk 1 is converted into a parallel light beam by the objective lens 8 at the time of focusing, and is returned to the polarization beam splitter 7 again. Then, the light is reflected by the polarization beam splitter 7 and guided to a four-divided photodetector 12 by an astigmatism optical system 11 composed of a cylindrical lens 9 and a convex lens 10, and the image is formed in a state where the focus shift appears as a change in shape. It is supposed to be. The quadrant photodetector 12 is constituted by four photodetection cells that convert light formed by the astigmatism optical system 11 into an electric signal. The two sets of signals output from the two photodetector cells arranged diagonally to each other in the four-split photodetector 12 are supplied to amplifiers 17 and 18 respectively.
It is supplied to.

The focus servo circuit 16 includes the amplifiers 17 and 18
Error amplifier 19 for inputting the two signals amplified in the step (a) and performing error amplification, a phase correction circuit 20 for correcting the phase of an output signal of the error amplifier 19, and supplying an output signal of the phase correction circuit 20 to a driver 22. Analog switch to control whether or not
And a driver 22 for amplifying a signal from the analog switch 21 to drive the actuator 21. When the analog switch 21 is turned on by a focus on / off signal S3 from the control circuit 3, a signal from the phase correction circuit 20 is supplied to the actuator 15 via the driver 22 to form a focus servo loop. It has become so.

The output signals from the amplifiers 17 and 18 are added to an adder 23.
It is supplied to. The signal added by the adder 23 reflects the recorded contents of the optical disk 1, and is output as a waveform signal as shown in FIG. That is, during normal recording in which recording is performed in a non-recording area, as shown in FIG. 3 (a), a signal having a signal level which is ten and several times higher than the signal level at the time of reproduction is obtained, and is recorded in the already recorded area. Figure 3 (b)
As shown in (1), many signals having a signal level higher than the signal level during normal recording can be obtained. This is because the recording light beam is applied to the already recorded portion, and the amount of reflected light increases in that portion. The output signal of the adder 23 having such a waveform is sent to the binarization circuit 24.

The binarization circuit 24 is formed of, for example, a comparator, and performs binarization by comparing an analog signal output from the adder 23 with a predetermined threshold level Th. The threshold level Th is set as a signal that is higher in level than the reflected light signal level when recording is performed on an unrecorded area and lower than the reflected light signal level when recording is performed on an already recorded area.
A signal having 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 output to the detection circuit 30
It is supplied to.

The detection circuit (detection means) 30 receives the recording data S11 and the reflected light signal S4 output from the binarization circuit 24,
This is to generate the overwriting detection signal S8. That is, if the optical disk 1 to be recorded is not recorded, a significant signal should be obtained from the binarization circuit 24 corresponding to the recording data S11 (S10). Therefore, the detection circuit 30 checks whether or not the recording data S11 and the reflected light signal S4 from the binarization circuit 24 have a one-to-one correspondence, and a reflected light signal S4 corresponding to the recording data S11 is obtained. If not found, double writing detection signal
Outputs S8. The double write detection signal S8 from the detection circuit 30 is supplied to the counter circuit 31.

The counter circuit (counting means) 31 counts the number of occurrences of the double write detection signal S8 output by the detection circuit 30, and outputs a recording prohibition signal S9 when the count exceeds a predetermined value. The detection of the recording prohibition signal S9 when it is detected that the value has exceeded the predetermined value is performed because, for example, when there is a portion of the optical disc 1 where the reflectance has changed due to crystallization or denaturation from the beginning, unrecorded data is recorded. This is because the double-write detection signal S8 is output even in the area, resulting in erroneous detection. The predetermined value is determined as follows. That is, the upper limit of the predetermined value is
It is regulated by the burst error correction capability of the device. This is because recording must be stopped while data destroyed by double writing is in a state where it can be repaired by an error correction circuit (not shown). On the other hand, the lower limit of the predetermined value is determined by an allowable range of a defect such as a pinhole on the optical disc 1. In other words, while recording is performed on a defective portion on the optical disc 1, the above-described double write detection signal S8 is continuously output, but if the write inhibit signal S9 is output before passing through the defective portion, erroneous detection is performed. Therefore, the predetermined value must be equal to or more than the minimum allowable value. The recording inhibit signal S9 from the counter circuit 31
Is supplied to the AND gate 33. Note that the clear signal S12 is supplied from the control circuit 3 to the counter circuit 31, and the counter is reset.

The AND gate 33 is connected to the control circuit 3 from an external device (not shown).
The recording data S10 supplied via the as one input,
The recording inhibition signal S9 output from the counter circuit 31 is used as the other input to output recording data S11 whose inhibition / permission is controlled. The recording data S11 is supplied to the waveform shaping circuit 32, the detection circuit 30, and the counter circuit 31. The waveform shaping circuit 32 shapes the recording data S11 and supplies it to the driver 28 described later.

Further, a photodetector 13 provided with a photoelectric conversion element such as a photodiode, which is provided to face the light emitting port of the semiconductor laser oscillator 5 opposite to the light emitting port of the laser beam for recording or reproduction, is provided with the semiconductor laser. By irradiating the monitor light from the laser oscillator 5, the monitor light is converted into an electric signal (photocurrent) and supplied to the optical output control circuit 14 as the optical 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 be kept 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 receives the optical output monitor signal S5 photoelectrically converted by the photodetector 13 and taken out as a current signal, and receives the light intensity received by the photodetector 13, that is, the semiconductor laser oscillator 5
This is converted into a voltage signal S6 corresponding to the optical output of the above and output. The voltage signal S6 output from the current / voltage conversion circuit 25 is supplied to the error amplifier 26.

The error amplifier 26 receives the voltage signal S6 as one input,
The reference voltage V _s generated by a not-shown constant voltage source as the other input, and compares these two voltages S6 and V _s, and outputs an error signal by amplifying the difference. The reference voltage V _s is a constant voltage for obtaining an optical output necessary for reproduction. The feedback control is performed to bring the voltage signal S6 closer to the reference voltage V _s , so that a constant optical output from the semiconductor laser oscillator 5 is obtained. Is obtained.
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, whereby an optical output for recording is output from the semiconductor laser oscillator 5. It is supposed to be.
The driver 28 has an error amplifier 26 during reproduction.
Is input, and at the time of recording, a voltage signal which is held by a sample and hold circuit (not shown) at the voltage value input at the time of the immediately preceding reproduction is input. Switching can be made depending on whether to perform recording or reproduction. In both cases of recording and reproduction, feedback control is performed at the level of the light output at the time of reproduction.

Next, in the optical disc device configured as described above, an operation in the case of suppressing double writing during recording will be described.
This will be described with reference to the timing chart of FIG.

First, prior to performing the recording operation, an initial operation for checking the validity of the light emission output of the semiconductor laser oscillator 5 is performed. That is, the focus on / off signal S3
, The analog switch 21 is turned off. This breaks the focus servo loop,
The objective lens 8 is released from the focusing control.
Next, a signal (not shown) for forcibly moving the lens actuator 15 is sent from the control circuit 3 to the driver 22.
Is supplied to the lens actuator 15 via the. Thereby, the objective lens 8 is forcibly moved to the position shown by the dotted line in FIG. 1, and a defocused state is created. In this defocus state, the semiconductor laser oscillator 5 is turned on by supplying power to the light output control circuit 14, and the output of the laser beam is started. As a result, the monitor light generated from the semiconductor laser oscillator 5 is converted by the photodetector 13 into a current corresponding to the light output and output as a light output monitor signal S5. The current-voltage conversion circuit 25 converts the optical output monitor signal S5 into a voltage signal S6, and supplies the voltage signal S6 to the error amplifier. In the error amplifier 26, a predetermined reference voltage
Comparing the V _s and the voltage signal S6, and outputs the error component as an error signal. This error signal is expressed as “voltage signal S6> reference signal
If “V _s ”, the optical output of the semiconductor laser oscillator 5 is reduced, and if “voltage signal S6 <reference signal V _s ”, the optical output of the semiconductor laser oscillator 5 is increased. The error signal feedback loop is formed by supplying to the driver 28 and the reference voltage V _s and the voltage signal S6 is controlled to be equal, thereby the light output of the semiconductor laser oscillator 5 is kept constant.

Next, the control circuit 3 controls the actuator via the driver 22.
By driving 15, the objective lens 8 is moved in the direction of the focal point. Then, 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 the initial operation is completed. Later,
Automatic focus control is performed by a focus servo loop, and normal operations such as reading and writing of information from the optical disc 1 are performed.

In such a state, as shown in FIG. 2A, pulse-like recording data S10 is output from the control circuit 3. 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 via the AND gate 33.
32, and further supplied to the driver 28. As a result, the semiconductor laser oscillator 5 emits intermittent high-output laser light corresponding to the recording data S10. This laser light is converted into a parallel light beam by the collimator lens 6 and guided to the polarization beam splitter 7. The laser beam guided to the polarization beam splitter 7 is
Is transmitted to the objective lens 8 and the objective lens 8
Is focused toward the recording film 1a of the optical disc 1.
Thus, information is recorded on the recording film 1a.

On the other hand, the divergent laser light reflected from the recording film 1a of the optical disc 1 during the recording operation is converted into a parallel light beam by the objective lens 8 and returned to the polarization beam splitter 7 again. Then, the light is reflected by the polarization beam splitter 7 and is imaged on a four-division photodetector 12 by an astigmatism optical system 11 composed of a cylindrical lens 9 and a convex lens 10. At this time, if the area of the optical disc 1 on which writing is being performed is an already recorded area, reflected light waveforms having different light intensity levels are obtained as shown in FIG. 2 (b). The signal photoelectrically converted by the quadrant photodetector 12 is supplied to amplifiers 17 and 18, respectively. And amplifier 17
One of the signals amplified by and is supplied to the focus servo circuit 16 below the error amplifier 19 and used for focusing control. The other of the signals amplified by the amplifiers 17 and 18 is supplied to an adder 23, where the signal is added, and then supplied to a binarization circuit 24.

As shown in FIG. 3, the binarizing circuit 24 includes the adder 23
Is compared with a predetermined threshold level Th to output a binarized reflected light signal S4 as shown in FIG. 2 (c). At this time, the laser light applied to the already recorded portion is not treated as significant data because the reflected light is larger than the threshold level Th (the middle dotted line in FIG. 2 (c)). Then, the reflected light signal S4 is supplied to the detection circuit 30.

The detection circuit 30 includes a flip-flop (not shown). The flip-flop is set at the rising edge of the recording data S11 output from the AND gate 33,
It is reset at the rising edge of the reflected light signal S4. The output of the flip-flop is output from the detection circuit 30 as a double write detection signal S8 as shown in FIG.

The counter circuit 31 receives the double write detection signal S8, captures the level of the double write detection signal S8 at the falling edge of the recording data S11 which is the other input, and counts the count pulse of the built-in counter (not shown). (Fig. 2 (e)
See). When the count pulse is counted by a counter and a predetermined value is counted, the recording inhibition 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, thereafter, 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. Then, the recording prohibition state is maintained until the clear signal S12 is output from the control circuit 3. This prevents double writing.

As described above, it is not immediately determined that double writing is performed when an object with a large amount of reflected light from the optical disk 1 is detected, but is determined as double writing when a predetermined number or more of objects with a large amount of reflected light are detected. As a result, erroneous detection and omission of detection can be greatly reduced.

Until a predetermined amount or more of light reflected from the optical disc 1 is detected, the data in the recorded area is destroyed. However, the amount of data destroyed is set to be within an error-correctable range. It does not impair the reliability of the recorded data.

As described above, the magnitude of the reflected light when the pulsed recording light beam output from the semiconductor laser oscillator 5 is reflected by the optical disc 1 depends on whether the reflected light is reflected from an already recorded area or not. Utilizing the property of being different from the case where light is reflected from the optical disk, a pulsed recording light beam is emitted from the semiconductor laser oscillator 5, and the reflected light reflected by the optical disk 1 is compared with a predetermined threshold level. In this way, a pulse equal to or higher than a predetermined level is detected by the detection circuit 30 from the binarized signal.
Since the count is made at 31 and the count value is equal to or greater than a predetermined value, the area is determined to be a recorded area and the recording operation is stopped, so that the recording light beam which is relatively stable is reflected. Since the magnitude of the light is detected, stable detection can be performed, and the reflected light of a plurality of predetermined levels or more is detected, and then the double writing is determined.
Overwriting can be prevented.

In the above embodiment, the case where the detection circuit 30, the counter circuit 31, and the like are operated using the rising and falling edges of the recording data S10 (S11) has been described. However, the recording method and the configuration of the waveform shaping circuit 32 are described. Record data by etc.
Since the phase of S10 (S11) and the reflected light signal S4 change, if the operation timing is appropriately changed according to the recording method, the configuration of the waveform shaping circuit 32, and the like, the same effect as in the above embodiment can be obtained. Play.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide an optical disk device capable of preventing erroneous detection or omission of detection and reliably preventing double writing.

[Brief description of the 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,
FIG. 2 is a timing chart for explaining the operation, FIG. 3 is a diagram for explaining the state of the reflected light at the time of normal recording and at the time of double writing, and FIG. It is a figure for explaining operation. DESCRIPTION OF SYMBOLS 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 photodetectors, 13… photodetectors, 14… optical output control circuits, 15… lens actuators, 25… current-voltage conversion circuits, 24… binarization circuits, 30… detection circuits ( Detecting means), 31 ... counter circuit (counting means), 32 ... waveform shaping circuit, 33 ... AND gate (control means).

Continuation of the front page (72) Inventor Akihiko Doi 70, Yanagicho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba Intelligent Technology Co., Ltd. (56) References JP-A-64-76424 (JP, A) JP, A)

Claims (2)

(57) [Claims] An optical disk device for recording information by irradiating a light beam based on a pulse-like recording signal onto an optical disk, wherein when recording information on the optical disk, a pulse-like recording signal corresponding to the recording information is recorded. Light output means for irradiating the optical disc with a light beam based on the light beam; detection means for detecting reflected light from the optical disc of the recording light beam irradiated from the light output means; and detecting the reflected light detected by the detection means. Binarizing means for comparing the reflected light with a predetermined level so that a signal of a higher level than the predetermined level is not treated as significant data; and a signal binarized by the binarizing means. Detecting means for generating a double-write detection signal from the detection means; counting the double-write detection signal generated by the detection means;
Means for outputting a recording prohibition signal when the count value becomes equal to or more than a predetermined value. The data amount of the recording area irradiated with the light beam can be corrected while counting the double writing detection signal. Counting means set so as to be within a range, and control means for performing control to stop irradiation of the recording light beam by the light output means in response to a recording inhibition signal from the counting means. Optical disk device. 2. The optical output means according to claim 1, wherein the monitor light is converted into an electric signal by a photoelectric conversion element provided opposite to a light emitting port opposite to the light emitting port of the pulsed recording light beam. 2. The optical disk device according to claim 1, wherein the optical output of the output means is controlled to be constant.