JPH0312377B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a write-once optical disc device that optically records/reproduces data, and particularly relates to a write-once optical disc device that optically records/reproduces data, and in particular, a method of continuously emitting a light beam for a predetermined data length onto an optical disc medium. The present invention relates to an optical disk device that accurately reads predetermined marks formed by irradiation.

Optical disk devices, which are expected to be used as high-capacity external storage devices for information processing devices, are capable of recording at a density more than ten times that of conventionally used magnetic disk devices. It has the disadvantage of a very high error rate due to defects and non-uniformity.

On the other hand, since data is recorded in an optical disk device by irradiating a light beam onto the surface of the optical disk medium to make holes (pits), the data can be stored for a long period of time.

However, when an error occurs during data recording in a predetermined area, or if you want to erase data that has already been recorded to maintain confidentiality, there is no way to accurately detect that the data is being erased, and the data must be erased. There has been a strong desire to put into practical use optical disc devices equipped with a method for accurately detecting regions.

[Problems to be solved by conventional technology and invention]

Fig. 5 is a diagram of the optical system configuration of a write-once optical disc device, and Fig. 6 is a diagram showing the configuration of the optical system of a write-once optical disc device.
The playback status diagram and FIG. 7 each show a schematic diagram of the configuration of the optical disc medium.

Recordable optical disk devices generally use recording materials that do not require post-recording processing. By strongly focusing the laser beam onto this recording material, pits (holes) are thermally made in the recording film 11 (there is also a method of changing the recording film 11, but in this example, a method of making pits (holes) is used) data is recorded by

The laser light narrowed down by the focusing lens 34 is
The optical disk medium 12 is irradiated with a minute spot of about 1 to 2 μm in diameter, and the pit (hole) formed is about 0.6 to 1.0 μm in diameter. Incidentally, when forming the pits (holes) and recording data, the output of the laser diode 31 on the recording film 11 is approximately 5 to 10 mW. Further, during data reproduction, the power on the recording film 11 is approximately 1 to 2 mW.

During both data recording and reproduction, the photodetector 32 detects changes in the amount of transmitted laser light from the recording film 11 (method shown in FIG. 6A) or reflected light (method shown in FIG. 6B). A detection signal is obtained by detecting the

That is, when recording data, the laser diode 31
is oscillated at a high output (several tens of milliwatts) in response to an input signal transferred from a circuit (not shown), and a pit (hole) is recorded on the optical disk medium 12.

On the other hand, when reproducing data, the laser diode 3
1 is continuously oscillated at several mW, and the optical disk medium 12
A beam splitter 35 guides the reflected light beam from above to a photodetector 32 for signal detection. Note that the diaphragm lens 34 and the follow-up mirror 33 are movable in the direction of the arrow in order to follow the minute pits (holes) on the optical disk medium 12.

Such an optical disk medium 12 has a structure as shown in FIG. 7 (top view and sectional view).
That is, it consists of a transparent substrate 10 and a recording film 11, and the recording film 11 portion consists of a preformat section 1 on which index marks, track numbers, sector numbers, etc. are recorded in advance, and a groove section 2 on which data is recorded. ing.

The preformat section 1 and the groove section 2 are formed on a transparent substrate 10 using a stamping technique, and then a recording film 11 is deposited thereon.
Data recording/reproduction is performed by irradiating the recording film 11 with a laser beam while tracking the groove portion 2.

When processing data recorded by such an optical disk device as invalid data due to a defect in the optical disk medium 12, etc., the following method has conventionally been used.

That is, the management information necessary for data recording/reproduction (for example, whether recording data in a given sector is valid/invalid, recorded sector number, etc.) is stored in another recording device, such as a floppy disk device. If you want to erase the data in the specified sector,
By performing processing such as erasing the management information on the other storage device, invalid data erasure processing is performed.

However, with this method, if there is a failure in another storage device, etc., data will be reproduced even if it is an invalid data portion, which poses a problem in terms of data confidentiality. It has been devised to form erase marks on the optical disk medium 12 by continuously irradiating a predetermined length of the upper data recording portion with a laser beam.

However, when detecting erase marks recorded using this method, conventional recording/reproducing means first drill pits (holes) and then record them again, making it difficult to detect erase marks due to effects such as the diffusion of the thermal energy of the laser beam. There was a problem in that it was not possible to record erase marks on the disk, and therefore it was not possible to accurately detect erase marks.

[Means for solving problems]

It is an object of the present invention to realize a novel optical disk device that solves the above-mentioned problems. The reflected light amount fluctuation signal obtained by extracting only the reflected light amount fluctuation signal and the reflected light amount fluctuation signal are passed through a low-pass filter circuit having a time constant sufficiently longer than the continuous irradiation time of the light beam required to create the predetermined mark. This problem is solved by the optical disk device according to the present invention, which detects the predetermined mark by comparing the output signal with a predetermined offset added thereto.

[Effect]

In other words, a predetermined mark (erase mark) is recorded on a predetermined portion of an optical disk medium by continuously irradiating a laser beam for a period sufficiently longer than one data recording bit length.
A reflected light amount variation signal that is obtained by extracting only the DC component from a reflected light amount signal of a laser beam irradiated with the light intensity during reproduction, and a low-pass filter having a time constant sufficiently longer than that of the predetermined mark portion to pass this reflected light amount variation signal into the reflected light amount signal. By passing the light through the detector circuit to perform an integration operation and comparing the level value with the level-shifted signal, it is ensured that there is a sharp change in the amount of reflected light between the data recording area and the predetermined mark (erase mark) area. This made it possible to detect

〔Example〕

The gist of the present invention will be specifically explained below with reference to embodiments shown in FIGS. 1 to 4.

FIG. 1 is a block diagram showing an embodiment of the erase mark detection circuit according to the present invention, FIG. 2 is a diagram showing the state of erasure mark recording on an optical disk medium, and FIG. 3 is a diagram showing various signals in the example of the detection circuit shown in FIG. 1. The waveforms and FIG. 4 each show an example of how the erase mark is applied. The same reference numerals indicate the same objects throughout the figures.

Next, the operation of this embodiment will be explained.

The write-once optical disc device uses an optical disc medium 12 in which a recorded portion cannot be erased and recorded again. Therefore, optical disk medium 1
2, recording, for example, a predetermined mark, is required to distinguish between data-recorded portions and unrecorded portions.

Furthermore, even if it is desired to erase data from a previously recorded data portion for the purpose of data security, etc., the purpose can be achieved by continuously recording predetermined marks.

These predetermined marks a (hereinafter referred to as erase marks a) are created by continuously oscillating a high-output (several tens of mW) laser beam from the laser diode 31 for a predetermined length.
Erase mark a is recorded on groove 2 as shown in FIG.

The erase mark a recorded in this manner is reproduced as follows. That is, the laser diode 31 is continuously oscillated at several milliwatts to irradiate the optical disk medium 12, and the amount of reflected light is detected by the photodetector 32.
Detect with. The detection signal at this time has a signal waveform shown in FIG. 31.

The photodetector 32 is composed of four sensors (not shown), and the sum of the detection signals of the respective sensors (not shown) is used as the detection signal of the photodetector 32.

This detection signal is obtained by detecting a variation in the amount of reflected light received by a sensor (not shown) as a voltage variation. Further, '' in FIG. 3 is a reflected light amount fluctuation signal obtained by extracting only the DC fluctuation component of the detection signal, and can be easily obtained using a generally well-known integrator (not shown).

Since data was recorded in the erase mark a section c shown in Fig. 3, the data could not be completely erased due to the influence of the diffusion of thermal energy of the irradiated laser beam, and the erase mark a section If only the DC signal component of the reflected light amount detection signal is detected using an integrator (not shown) that has a time constant that is sufficient to detect fluctuations, noise will remain in the detection signal (reflected light amount fluctuation signal'). It turns out. Therefore, processing such as noise removal is performed by passing the signal through a low-pass filter having a time constant sufficiently longer than the length of the erase mark a to further filter the high-frequency components.

The block diagram shown in FIG. 1 is a circuit showing an embodiment of the present invention for detecting erase marks a and c. Amplifier 5 is a circuit that adds a predetermined offset voltage to the output from the low-pass filter.

The final stage is a comparator 6, which is a circuit that compares the signal obtained by adding a predetermined offset to the output from the low-pass filter and the signal '.

Analog switch 4 is normally switched off. That is, when detecting the preformat 1 section a shown in FIG. 3, the output of the operational amplifier 3 is set to zero voltage by the analog switch 4 (controlled by a signal).

This is because in the transient region from preformat 1 part a to data part b, there is a part where the light intensity changes sharply, similar to when changing from data part b to erase mark a part c, and this is called erase mark a. This is to avoid false detection.

When data detection is started, the analog switch 4 receives a data area signal from a circuit not shown, releases the short of the operational amplifier 3, and a detection signal ' is inputted.

The detection signal ' sent to the operational amplifier 3 is processed by a feedback circuit (resistor R3, capacitor C1) having a time constant τ sufficiently longer than the length of the erase mark a.
) and then sent to the second stage operational amplifier 5.

Note that the time constant τ of the feedback circuit (consisting of resistor R3 and capacitor C1) is selected to be approximately 16 μsec in this embodiment. This is to avoid detection of signals smaller than this time width (signals of defects, noise, etc. in the optical disk medium 12), since the time width of the erase mark a section c is set to about 11 μsec.

The operational amplifier 5 connects the sent signal to the power supply +
A voltage (approximately -100 mV in this embodiment) adjusted by a variable resistor RV (approximately -100 mV in this embodiment) is added as an offset voltage and sent to the (-) terminal of the comparator 6 as a signal. On the other hand, the signal is (+) of comparator 6.
The comparator 6 compares the signals and sends the matched signal waveform as an erase mark a detection signal to a circuit (not shown). It is possible to detect that this signal becomes low level in a predetermined section and determine that the area is an erase mark a area.

In this embodiment described above, the erase mark a is detected as a mark for erasing recorded data, but by assigning meaning to the location where the erase mark a is recorded on groove 2, various identification signals can be detected. It can be used as

That is, as shown in FIG. 4, for example, write marks d are used to distinguish recorded and unrecorded parts of data, and marks e and e' are used to separate data in recorded parts. It is possible to use it. This determination can be realized by changing the writing time of a predetermined mark in continuous irradiation, thereby changing the detection length of each mark, and giving specific meaning to d, e, and e'. In this way, by having a predetermined mark other than the pit configuration in the groove area, the subsequent data can be processed quickly and reliably, and data with the normal pit configuration can be detected and the same data can be extracted from the combination of the head data. This method has the advantage of being simpler, faster, and more reliable than other methods.

〔Effect of the invention〕

According to the present invention as described above, since the erase mark can be recorded directly on the medium and the erase mark can be reliably detected, it is possible to maintain complete confidentiality of data, and furthermore, the erase mark can be recorded on the medium in various ways. By using it as a recognition mark, there is an effect that management information when recording/reproducing data can be obtained more easily.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the erase mark detection circuit according to the present invention, FIG. 2 is a diagram showing the state of erasure mark recording on an optical disk medium, and FIG. 3 is a diagram showing various signals in the example of the detection circuit shown in FIG. 1. Waveform, Figure 4 is an example of erase mark application, Figure 5
The figure is a diagram of the optical system configuration of a write-once optical disc device, No. 6.
The figure shows a state of recording/reproducing data on an optical disk medium, and FIG. 7 shows a schematic diagram of the structure of the optical disk medium. In the figure, 1 is a preformat section, 2 is a groove section, 3 and 5 are operational amplifiers, 4 is an analog switch, 6 is a comparator, 10 is a transparent substrate, 11 is a recording film, 12 is an optical disk medium, and 30 is an optical system. mechanism, 31 is a laser diode, 32 is a photodetector,
33 is a follow-up mirror, 34 is a diaphragm lens, 35
indicates a beam splitter, and 36 indicates a lens.

Claims (1)

[Claims] 1. A preformat section 1 on which information regarding tracks and sectors, timing information, etc. are recorded in advance, and a groove section 2 which has a guide groove for tracking and records data. , optically record data by irradiating a light beam output from the laser diode 31, and also irradiate the light beam onto the data-recorded or unrecorded area on the medium surface for a period sufficiently longer than the length of one data recording bit. An optical disk device that records a predetermined mark a by continuously irradiating a portion of the predetermined mark a, the amount of reflected light obtained by detecting the reflected light of the light beam irradiated onto the predetermined mark a portion and extracting only the DC fluctuation component thereof. The fluctuation signal 'and the reflected light amount fluctuation signal' are passed through a low-pass filter circuit having a time constant sufficiently longer than the continuous irradiation time of the light beam required to create the predetermined mark a, and further a predetermined offset is added. output signal,
An optical disc device characterized in that the predetermined mark a is detected by comparing the predetermined mark a. 2. The low-pass filter circuit includes a resistor R3 of a predetermined value.
and a feedback section consisting of a capacitor C1,
It is composed of an operational amplifier 3 and an analog switch section 4, and when reading the information of the preformat section 1, the capacitor C1 is short-circuited by the analog switch section 4, and the output of the low-pass filter circuit is turned off. An optical disk device according to claim 1, characterized in that: