JP2753071B2 - 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.

2. Description of the Related Art Conventionally, in an information recording apparatus such as 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 semiconductor laser (light output) is used as a light source. Means) to read information on the optical disk with a relatively small continuous optical output, and to record information on the optical disk with a relatively large intermittently changing optical output of a predetermined value or more. 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 pit is detected in a reproduction 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,
There is a low-level portion (dark portion) at a position corresponding to the pit, and this becomes significant data. FIG. 4B shows a normal state.
That is, it shows a reflected light waveform 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. Then, the reflected light waveform shown in FIG. 4 (c) is compared with a predetermined threshold level Th, and when the presence of a pit (dark portion) is detected, it is determined that double writing is performed. That is, whether or not the currently recorded area is an unrecorded area or an already recorded area is determined based on whether or not a signal corresponding to a pit is included in a reproduced signal at the time of recording. Is to be prevented.

However, the reproduction signal at the time of recording becomes unstable due to the influence of, for example, an under short-circuit of the recording beam, so that erroneous detection or omission of detection occurs, so that double writing cannot be prevented reliably. Was. Although a means for detecting and preventing the occurrence of double writing is provided, there is no means for notifying the host device of information to that effect. There was a drawback that no treatment could be performed on the device side.

(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. The disadvantage is that erroneous detection or omission of detection occurs due to the unstable state due to the influence of the recording beam and double writing cannot be reliably prevented, and the means for detecting and preventing the occurrence of double writing is as follows. I have,
There is no means for notifying the host device of such information, and the host device is unable to take any action against the occurrence of double writing. It is an object of the present invention to provide an optical disk device capable of preventing double writing by surely preventing detection and omission, and capable of performing a predetermined measure on the host device side for occurrence of double writing.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, an optical disc device of the present invention has a light output means for emitting a pulsed light beam and a light beam emitted from the light output means. Detecting means for detecting the reflected light of the light beam; counting means for counting the number of pulses in which the reflected light detected by the detecting means is equal to or lower than a predetermined level; Control means for stopping the emission of the light beam from the output means, and processing means for receiving information to that effect and outputting the information to an external device when the emission of the light beam is stopped by the control means. I do.

(Operation) The present invention is characterized in that the magnitude of the reflected light of the pulsed light beam output from the light output means is different between the case where the light is reflected from a recorded area and the case where the light is reflected from an unrecorded area. Is used to detect double writing, and to notify an external device of the detection result. The light output means emits a pulsed light beam, and the reflected light of the pulsed light beam is set to a predetermined level. By comparing, the pulse below the predetermined level is detected by the detection means, the number of pulses below this predetermined level is counted by the counting means, and when the count value becomes above the predetermined value, the area is a recorded area. And the recording operation is stopped. Further, with the stop of the recording operation, the control means outputs a signal indicating double writing to the processing means, and the processing means further outputs the signal to an external device. As described above, since the magnitude of the reflected light of the light beam that is relatively stable is detected, stable detection can be performed, and the reflected light having a plurality of predetermined levels or less is detected, and then the double writing is determined. As a result, double writing can be reliably prevented, and the external device that has received the signal indicating double writing can transfer the information of the double-written area to another area, for example, and transfer the information of the double-written area to another area. And other measures can be taken.

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 of the present invention. In the figure, an optical disk (optical recording medium) 1
Is a doughnut-shaped metal coating layer such as tellurium or bismuth coated on the surface of a substrate formed into a circle with glass or plastics, for example.

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 the control circuit 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 meter 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 or the like, and performs recording or reproduction according to a control signal from the control unit 3. To a different 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 by the four-split photodetector 12 are respectively amplified by amplifiers 17 and 18
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. 3A, a signal having a signal level which is ten and several times higher than the signal level at the time of reproduction is obtained. In the case of so-called double writing for recording, as shown in FIG. 3B, many signals having a signal level several times the signal level at the time of reproduction are obtained. This is because a recording light beam is applied to a portion where a pit has already been formed, so that the amount of reflected light is reduced at the pit portion. The output signal of the adder 23 having such a waveform is sent to the binarization circuit 24.

The binarization circuit 24 includes, 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 lower in level than the reflected light signal level when recording is performed on an unrecorded area and higher than the reflected light signal level when recording is performed on an already recorded area. The reflected light signal S4 binarized by the binarization circuit 24 is
The signal is supplied to the detection circuit 30.

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 recording inhibition signal S9 is output when it is detected that the predetermined value or more is reached. For example, if there is a portion where the reflection film is missing from the beginning, such as a pinhole, on the optical disc 1, 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 detection signal S8 for double writing is continuously output. However, if the recording inhibition 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. A recording inhibit signal from this counter circuit 31
S9 is supplied to the AND gate 33 and also to the microprocessor 36 which controls the recording of information. Also, a clear signal generated by the control circuit 3 according to the control signal from the microprocessor 36 is provided to the counter circuit 31.
S12 is supplied, and the counter is reset. A control signal between the control circuit 3 and the microprocessor 36 is transmitted and received by a data bus (or interface bus) 36.

The microprocessor 36 transmits and receives information to and from the control circuit 3 and also transmits and receives information to and from a host device (not shown) as an external device.

The AND gate 33 has print data S10 supplied from a host device (not shown) via the control circuit 3 as one input, and has a print inhibit signal S9 output from the counter circuit 31 as the other input, so that inhibition and permission are controlled. Recorded data S11
Is output. 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 stores the recording data S1
1 is formed and supplied to a 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, 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 Vs generated by a constant voltage source (not shown) is used as the other input, the two voltages S6 and Vs are compared, and the difference is amplified and output as an error signal. The reference voltage Vs is a constant voltage for obtaining an optical output required for reproduction. By performing feedback control to bring the voltage signal S6 closer to the reference voltage Vs, a constant optical output is obtained from the semiconductor laser oscillator 5. It is supposed to be.
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
Vs is compared with voltage signal S6, and the error is output as an error signal. This error signal is expressed as “voltage signal S6> reference signal
In the case of “Vs”, the optical output of the semiconductor laser oscillator 5 is reduced, and in the case of “voltage signal S6 <reference signal Vs”, the optical output of the semiconductor laser oscillator 5 is increased. By supplying this error signal to the driver 28, a feedback loop is formed so that the reference voltage Vs and the voltage signal S6 are controlled to be equal, whereby the optical 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 detected 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, the control circuit 3 responds to the recording data sent from the host device (not shown) via the microprocessor 36.
Outputs pulse-like recording data S10. On this occasion,
The recording prohibition 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 S1
0 is supplied to the waveform shaping circuit 32 via the AND gate 33, and further supplied to the driver. 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 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. This makes the recording film
A pit is formed on 1a, and information is recorded.

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 disk 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 the amplifier 17 and
One of the signals amplified by 18 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 pits already formed does not appear as significant data because the reflected light is small (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, has the level of the double write detection signal S8 at the falling edge of the recording data S11 as the other input, and has a count pulse of a 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. The recording prohibited state is set by the clear signal S12 from the control circuit 3 in response to a command from the microprocessor 36.
Will be maintained until is output. This gives 2
Prevents overwriting. Further, since the write inhibit signal S9 is also supplied to the microprocessor 36, when the microprocessor 36 receives the write inhibit signal S9, it notifies the host device that double writing has occurred. Hereinafter, the host device displays the fact that double writing has occurred on the display unit of the host device to notify the operator, or re-records the data of the area of the optical disc 1 where the double writing has occurred in another area. Thus, measures such as maintaining the reliability of the data are performed.

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

Until a predetermined number 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 to be 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 a property that is different from the case where light is reflected from the optical disk 1, a pulse-like recording light beam is emitted from the semiconductor laser oscillator 5, and the pulse-like recording light beam changes the reflected light reflected by the optical disc 1 to a predetermined threshold level. Binarized by comparing with
A pulse equal to or lower than a predetermined level is detected from the binarized signal by the detection circuit 30, and the number of pulses equal to or lower than the predetermined level is counted by the counter circuit 31. When the counted value becomes equal to or higher than the predetermined value, the corresponding area is detected. Is determined to be a recorded area and the recording operation is stopped, so that the magnitude of the reflected light of the recording light beam, which is relatively stable, is detected, and stable detection can be performed. Since the double writing is determined after detecting the reflected light of a predetermined level or less, the double writing can be surely prevented. Further, with the stop of the recording operation, the control circuit 3 outputs a signal to the effect that the writing is double writing to the microprocessor 36,
Since the microprocessor 36 further outputs the signal to the host device as an external device, the host device that receives the signal indicating that the data is double-written via the microprocessor 36 is, for example, an area in the optical disk 1 where the double-writing is performed. The information can be moved to another area to take measures such as improving the reliability of the stored contents.

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 above in detail, according to the present invention, erroneous detection or omission of detection is prevented, double writing is reliably prevented, and the occurrence of double writing is determined on the host device side. It is possible to provide an optical disk device that can perform a predetermined treatment.

[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), 35 data bus, 36 microprocessor (processing means).

Claims (1)

(57) [Claims] A light output means for emitting a pulsed light beam; a detection means for detecting reflected light of the light beam emitted from the light output means; Counting means for counting the number of pulses equal to or lower than the level; control means for stopping emission of the light beam from the light output means when the predetermined value is counted by the counting means; and stopping emission of the light beam by the control means. Processing means for receiving the information to that effect and outputting the information to an external device.