JPH0154778B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical information recording and reproducing device for recording information on a disc-shaped recording medium (disc) that can be optically recorded and reproduced, and for reproducing the recorded information from this disc. It is related to.

Conventional structure and its problems Recording and reproducing signals at high density on an optical recording disk by concentrating the light of a laser or other device into a beam with a diameter of 1 μm or less is often done when recording signals on the master disc of a video disk. . Furthermore, with the recent development of new optical recording materials, optical recording and reproduction of digital signals and video signals is being carried out on optical disks. In addition, in order to record and reproduce high-density signals with a simple device, it is possible to use a disk with an optically detectable guide track and record and reproduce signals along or within the guide track. It is being done.

An example of an optical recording disk 2 having a guide track 1 is shown in FIG. As an example of the above-mentioned guide track, it has been proposed to use a groove with a depth of about 1/4 of the wavelength of light from a light source used for recording and reproduction and a width of ω (0.5 to 1 μm). These grooves are arranged spirally or concentrically at an appropriate track pitch P over the entire signal recording area on the disk.

When a recording material 4 is deposited on such a disk and a laser beam is focused on and irradiated with a minute spot, the reflectance of the recording material changes and recording bits 5 are formed.
FIG. 2 shows an example of the format of an optical recording disk. In FIG. 2, only one signal recording track is shown to simplify the drawing. In the figure, N indicates an address signal in which a unique address number is recorded in advance to distinguish the signal recording track from other tracks. n ₁ , n ₂ , . . . , n _n represent sector address signals in which sector address signals unique to each sector are recorded for use by dividing one signal recording track into a large number of sectors. l ₁ , l ₂ …,
_ln indicates an information recording area in which necessary information signals are recorded and reproduced corresponding to each sector address; the arrow indicates the rotation direction of the disk. There are several methods to guarantee the recorded contents of an optical recording disk. For example, there is a pre-check recording method in which dropouts in an information recording area that cause recording signal loss are checked before recording, and no recording is performed in sectors where dropouts exist. FIG. 3 shows the configuration of an optical information recording/reproducing apparatus having a pre-check recording function. 6 is a semiconductor laser, 7 is a condensing lens, 8 is, for example, a beam splitter, 9 is a tracking mirror, and 10 is an aperture lens. The aperture lens 10 focuses the light from the semiconductor laser 6 onto the optical recording disk 2 into a light beam having a diameter of about 1 μm. A photodetector 11 detects the reflected light from the disk 2 and converts it into an electrical signal. 12 indicates a disk motor;
The optical recording disk 2 is rotated at a specified speed. 1
Reference numeral 3 denotes a semiconductor laser drive circuit, which switches the optical output of the semiconductor laser 6 according to recording or reproduction, or performs optical modulation using data for one sector, and receives a recording signal from the control device 21. 1
Reference numeral 4 denotes the amplifier, which can output changes in the amount of reflected light from the disk as a reproduction signal. Using this reproduced signal, the track address detector 15 and the sector address detector 16 detect the track address and sector address, respectively, and access a specific sector information area. The dropout detector 17 detects the dropout in the sector information area.
is detected from the reproduced signal, and if there are more than a specified number of dropouts, the dropout detector 1
8 is activated, the sector is treated as a bad sector, no recording is performed, and the sector is skipped to the next succeeding sector information area. In this way, recording signals are guaranteed by determining a prescribed number of dropouts based on a judgment as to whether the demodulated signal can be error corrected or not, and recording only the sector information area that is less than the prescribed number.

When such a pre-check recording method is used, before recording information, it is necessary to reproduce the information recording area in which information is to be recorded and check for dropouts. If there is only one optical head that scans a track, a waiting time of one rotation is required even when recording in one information recording area.
That is, when recording information in the No information recording area of track address N and sector address n, a dropout check of the _{No information} recording area is first performed in the first rotation of the track scan. Next, track jumping is performed, and during the next one rotation of track scanning, data is recorded in the _No. information recording area based on the result of the dropout inspection. The occurrence of such waiting time significantly reduces data transfer speed. If the total number of sectors in one track is m, the transfer speed is 1/m compared to continuous recording without pre-check recording.
become. When performing pre-check recording on several tracks in succession, dropout inspection can be performed on one track or m sectors of information recording area at once. However, even in this case, the minimum
Since one track's waiting time is required to record a track, the data transfer speed is reduced by half. Furthermore, a circuit for storing the dropout test results for each track is required, making the structure complicated. The pre-check recording method, which performs a dropout check before recording information, has the drawback of slowing down the data transfer speed, which is inconvenient when it is necessary to record data continuously at high speed.

Purpose of the Invention The present invention solves the above-mentioned problems of the prior art, and uses reflected light from the recording light during information recording to reliably detect dropouts that cause large envelope defects in recording/reproduction signals. The purpose of this process is to improve the error rate after demodulation without slowing down the data transfer rate.

Structure of the Invention The present invention detects a dropout in an information recording area based on a difference signal between the outputs of the photodetector, which receives reflected light from the recording light with a photodetector while recording information, and
Based on the dropout inspection results, if it is determined that error correction during demodulation of the information recording area where dropout has occurred is impossible, a defective recording identification signal is recorded in a part of the information recording area and the information recording area is This is an optical recording and reproducing device that records the same information recorded in another information recording area and checks for dropouts.It is an optical recording and reproducing device that records the same information content recorded in another information recording area and checks for dropouts. Dropouts that cause defects in the envelope of recording/reproduction signals can be reliably detected, and highly reliable optical recording can be realized with a simple configuration.

DESCRIPTION OF EMBODIMENTS FIG. 4 is a diagram showing the configuration of an optical information recording/reproducing apparatus according to an embodiment of the present invention. The same components as those in FIG. 3 showing the configuration of the conventional example are given the same numbers. The reflected light from the optical recording disk 2 is received by a photodetector having at least two split surfaces, and the split photodetector outputs are input to difference amplifiers 20 and 21, respectively, to generate a focus error signal b and tracking. An error signal c is output.
On the other hand, the output of each divided photodetector is summed by amplifier 2.
2, a sum signal d representing the amount of total reflection light from the optical recording disk is output.
When the divided total photodetector outputs are input to the high frequency amplifier 23, reproduced signals a and a' are output. Note that the reproduced signal a is generated by the reproduced light, and the reproduced signal a' is generated by the reflected light of the recording light. The reproduction signal is input to a track address detection section 15 and a sector address detection section 16, and the information recording area for recording and reproduction is identified. A digital demodulation section 19 demodulates the information signal recorded in the information recording area. FIG. 5 shows signal waveforms at each part a to g shown in FIG. Waveforms other than the reproduced signal a indicate signal waveforms in a state where information is being recorded in each information recording area.

The focus error signal b and the tracking error signal c are input to gain control circuits 24 and 25, pass through a drive circuit 26, and drive a pickup 27 that performs focus control and tracking control. The gain control circuits 24 and 25 keep the amplitudes of the focus error signal b and the tracking error signal c constant depending on the amount of light reflected from the optical recording disk 2. That is, the gain control circuit signal output always shows a constant amount of control error even if the amount of reflected light from the optical recording disk 2 changes. There are two possible cases where the amount of reflected light from the optical recording disk changes. One is when the reflectance of the optical recording disk itself changes, and the other is when the amount of reflected light changes because the optical power is irradiated several times as much during recording as compared to when reproducing. Furthermore, since the peripheral speed of an optical recording disk differs depending on the recording location, the recording power may be changed depending on the recording location. FIG. 5 shows how information is continuously recorded in each information recording area except for a, as described above. The reproduction signal output during recording is shown in a'. 28 is a sector address area, 29 is an information recording area, and 30 is a reproduced signal detected by modulated recording light reflected from the optical recording disk.
31 is a normal recording/reproducing signal waveform by reproduction light.
Now, if a dropout exists in the information recording area, the envelope will be missing in the recording/reproduction signal as shown at 32, and a demodulation error will occur depending on the width, number, etc. of the dropout. The causes of dropouts that cause such large envelope chips include defects in the groove structure that forms the guide track, and unevenness in the base material of the optical recording disk itself, which makes it impossible for the focus control to follow the focus error signal. In most cases, this will cause errors.
FIG. 6 is a diagram schematically depicting the form of dropout that causes such a large envelope defect. FIG. 6a is a view of the guide track 1 seen from above the disk, and FIG. 6b is a sectional view in a direction parallel to the guide track. 33 indicates the level of the groove bottom, and 34 indicates the level between the grooves. 35 is an example of a dropout caused by a defect in the groove structure of the guide track described above, and the guide track is slow to run. This kind of dropout is the fifth
As shown in Figure 32, a large envelope gap occurs in the recording/playback signal, but the playback signal output during recording is
It is hardly detected in a′. This is because the reproduced signal can detect changes in the amount of total reflected light from the optical recording disk, but it cannot detect changes in the diffraction distribution of reflected light, such as dropouts caused by defects in the groove structure. Such a dropout is detected by the difference signal output of the guide track and the vertically divided photodetector, that is, the tracking error signal c, as shown in the waveform of FIG. 537. On the other hand, dropouts caused by unevenness of the base material itself, as shown in FIGS. 36 and 36', also cause large dropouts in the recording/reproduction signal. This type of dropout also causes almost no change in reflectance, so it is not detected in the reproduced signal output during recording (FIG. 5a'). However, since this unevenness corresponds to a displacement in the focus control direction, it is detected by the focus error signal b as shown in the waveform shown in FIG. 537.

As mentioned above, dropout, which causes a large gap in the envelope of the recording/playback signal for which error correction is judged to be impossible during demodulation, is caused by the dropout in the playback signal during recording.
It cannot be detected from a' and can only be detected using the tracking error signal c or the focus error signal b. By the way, during recording, as shown in FIG. 5, the focus error signal b and the tracking error signal c in the information recording area are affected not only by the drop-out part as shown in 37 but also by the increase in the amount of reflected light from the recording light. The amplitude of the illuminated area also changes. Therefore, as described above, by using the focus error signal b' and the tracking error signal c' whose gains are controlled according to the amount of reflected light from the optical recording disk, it is possible to detect only the change in signal amplitude due to dropout (the Figure 5 b′, c′). Figure 5d
represents the amplitude change during recording of the sum signal d, but the area irradiated with the recording light is hardly affected by the modulation by the information signal of the recording light, and the average value of the amount of reflected light of the recording light It shows the level. This is because the signal band of the sum amplifier 22 is much lower than the band of the information recording signal. FIG. 7 shows an example of a gain control circuit. Since the resistance value between the drain and the source of the FET 38 can be controlled by the gate voltage, the resistance between the drain and the source of this FET is used as a feedback resistance of the operational amplifier 39. Add the sum signal output d to the gate, and set the DC bias 4 so that the product of the operational amplifier gain and gate voltage is constant.
Set to 0.

The focus error signal b' and the tracking error signal c' whose gain is controlled by the amount of reflected light in this way are input to dropout detection circuits 41 and 42,
The signal is compared with the reference level shown at 44 and is output into pulses (FIG. 5 b'', c'').

FIG. 8 shows an example of a dropout detection circuit. The output of the gain control circuit is input to a forward amplifier 45 and an inverting amplifier 46, each of which is diode-clamped and set to a reference level 43 by a comparator 47 for a dropout in the positive direction, and set to a reference level by a comparator 48 for a dropout in a negative direction. The signal is compared and outputted at 44 and converted into a pulse. The reference levels 43 and 44 are set at dropout signal amplitude levels that cause a drop in the envelope such that error correction is impossible when the recording/reproducing signal is demodulated. Dropout inspection units 49 and 50 count the width, number, etc. of dropouts during recording, and send the data to the control device 21. When the control device 21 demodulates the information recording area _l3 currently being recorded and determines that there is a dropout for which error correction is not possible, the control device 21 transmits the recording gate signal e to the digital modulation section 5.
Stop sending to 1. Instead, a recording gate signal f is sent to the identification signal generator 52 indicating that the information recording area is defective, as shown in FIG.
Control is performed so that a defective recording identification signal as shown in FIG.
Furthermore, a re-recording request 54 is sent to the digital modulation,
Control is performed so that the information contents (data #2 in FIG. 5) that were defectively recorded are recorded again in the next information recording area _l4 . FIG. 5g shows the timing of the content of modulation data output to the semiconductor laser drive circuit. It goes without saying that re-recording is not limited to the subsequent information recording area _n4 , but that alternative information recording areas for defective recording may be provided in other areas of the optical recording disk and recording may be performed in this area.

As described above, according to this embodiment, while recording information, the focus error signal to which gain control is applied,
By detecting dropouts from tracking error signals, it is possible to reliably detect the information recording area of defective records in real time during recording, without slowing down the data transfer speed unlike pre-check recording, and to replay the defective records. By recording, highly reliable optical recording can be realized with a simple configuration.

Effects of the Invention The optical recording/reproducing device of the present invention receives the reflected light from the optical recording disk by the recording light during recording of information with a photodetector having at least two or more dividing planes, and outputs an output from the photodetector. Dropouts in the information recording area are reliably detected even during recording based on the difference signal between the two, and when it is determined that error correction during demodulation of the information recording area where the dropout has occurred is impossible based on the dropout inspection results. The pre-check recording method records a defective recording identification signal in a part of the information recording area, records the same information recorded in the information recording area in another information recording area, and checks dropouts again. In real time during recording, without slowing down the data transfer speed, only dropouts that cause defects in the envelope of the recording/playback signal are detected, regardless of changes in the amount of reflected light from the optical recording disk, to guarantee the recorded content. Moreover, highly reliable optical recording can be realized with a simple configuration.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the structure of an optical recording disk having a guide track, FIG. 2 is a diagram showing the format of the optical recording disk, and FIG. 3 is a diagram showing the configuration of an optical recording/reproducing apparatus using a conventional pre-check recording method. FIG. 4 is a block diagram showing the configuration of an optical recording/reproducing apparatus in an embodiment of the present invention.
FIG. 5 is a diagram showing signal waveforms of various parts in the same embodiment, FIG. 6 is a schematic diagram showing a dropout form, and FIG. 7 is a circuit diagram showing an example of a gain control circuit.
FIG. 8 is a circuit diagram showing an example of a dropout detection circuit. 1...Guide track, 2...Optical recording disk, N...
Track address area, n... Sector address area, l... Information recording area, 11... Photodetector, b... Focus error signal, c... Tracking error signal, d... Sum signal, 24, 25... Gain control circuit, 41, 42 ... Dropout detection circuit, 49, 50... Dropout inspection section.

Claims (1)

[Scope of Claims] 1 A light source such as a semiconductor laser is focused into a minute spot light and irradiated onto an optical recording disk having a concentric or spiral guide track, a track address area, a sector address area and an information recording area to record information. a means for recording and reproducing the information; and a photodetector having at least two dividing surfaces to receive reflected light from the optical recording disk by the recording light modulated by the information signal during recording of the information; means for detecting dropouts in the information recording area being recorded based on output difference signals; inspection means for measuring the size and number of the detected dropouts; and information on the occurrence of dropouts based on the results of the inspection means. a determining means for determining whether error correction is possible or impossible during demodulation of a recording area; and when the determining means determines that error correction is not possible during demodulation, it is determined that there is defective recording in a part of the information recording area; If the determining means determines that error correction during demodulation is impossible, the same information content as the information recording area where the defective recording occurred is recorded in the information recording area where the defective recording occurred. An optical information recording/reproducing device comprising means for recording in the next information recording area or another alternative information recording area subsequent to the first information recording area. 2. The means for detecting dropout detects dropout using a signal obtained by applying gain control to a focus error signal, which is a difference signal of the output of a photodetector, in accordance with a change in reflected light from an optical recording disk. The optical information recording and reproducing device described in 2. 3. The means for detecting dropout detects dropout using a signal obtained by applying gain control to a tracking error signal, which is a difference signal of the output of a photodetector, in accordance with a change in reflected light from an optical recording disk. The optical information recording and reproducing device described in 2.