OPTICAL DATA RECORDING AND REPRODUCING APPARATUS WITH ERASE FUNCTION DIAGNOSIS

Abstract: An optical recording and reproducing apparatus for recording and reproducing data in an optical disk (200) is disclosed. The optical disk has a plurality of erase test sectors in tracks (20l - 205), in one of which the accumulated number of tests together with test data is written. The data read from the erase test sector is compared with the recorded data to effect an erase function diagnosis. If data comparison shows an incoincidence or the accumulated number of tests exceeds a predetermined level, a new erase test sector is used. The fatigue of the recording medium caused by a defect of the medium or reduced erasing efficiency due to an increased number of erasures of the recording medium is checked by controlling the accumulated number, completely separately from the fault of erase function of the apparatus, thus improving the reliability of the erase function self-diagnosis. Upon detection of an error in the read data or when the accumulated number of tests exceeds a predetermined level, a marking signal is written in the data field (l5) of a defective sector, shifting to a new erase test sector not yet marked for subsequent erase function self-diagnosis, thereby making possible erase function self-diagnosis without being affected by the fatigue of the recording medium.

Description: BACKGROUND OF THE INVENTION The present invention relates to an optical data recording and reproducing apparatus, or more in particular, to the diagnosis of the erase function of an apparatus for recording and reproducing data on an optical disk. Fig. 3 shows a phase change between an amorphous state A and crystal state C of a phase-change recording medium of a conventional optical data recording and reproducing apparatus. The reflectivity in amorphous state A is smaller than that in crystal state C. When a part of the recording medium is increased to a temperature near the melting point and annealed, a crystal state is obtained. When the part in crystal state C is locally increased in temperature to a level near the melting point followed by quenching, in contrast, the amorphous state A is attained. Fig. 4(a) shows a configuration of a light beam for realizing conditions for temperature increase followed by quenching and temperature increase by annealing of the recording medium, and Fig. 4(b) a light distribution therefor. In Fig. 4, reference numeral l3 designates a guide track deposited with a recording layer by evapora­ tion, numeral l4 an identifier (ID field) for a sector including such data as track address and sector address, numeral l5 a data field for recording data, numerals l6a, l6b gaps for absorbing time variations due to rotational variations of the disk, numeral l7 a recording and reproducing light beam in short diameter, numeral l9 a light intensity distribution thereof, numeral l8 an erase light beam in long diameter, and numeral 20 a light intensity distribution thereof. Two light beams, by creating annealing conditions with long diameter and quenching conditions with short diameter, perform the erasing and recording operations in one revolution of the disk, thus making what is called the simultaneous erasing possible. Fig. 4(c) shows a waveform of a reproduction signal produced from the sector identifier (ID field) l4, data field l5, gap l6a, l6b formed on the guide track of the optical disk, with the reflectivity of the sector identifier (ID field) l4, gap l6a, l6b and data field l5 decreasing in that order. Fig. 4(d) shows a write gate signal l02 for commanding the writing of the recording-reproducing light beam l7 set in record mode and modulated with the write data, in the data field l5. Fig. 4(e) shows an erase gate signal l03 for controlling the time during which the erase light beam l8 is irradiated on the data field l5 of the guide track l3 with a predetermined intensity. Data is recorded in the data field l5 with the succeeding recording-reproducing light beam l7 while erasing the data field l5 with the preceding erase light beam l8 by enabling the write gate signal l02 and the erase gate signal l03. At the end of data recording, the write gate signal l02 and the erase gate signal l03 are both turned off. In the above-mentioned configuration, however, the erase light beam l8 and the recording-reproducing light beam l7 are exactly aligned on the same guide track, and therefore it is necessary both to trace the guide track l3 with high accuracy and to irradiate the erase light beam l8 and the recording-reproducing light beam l7 on a sector to be erased with a predetermined erasing power and recording power respectively. For simultaneous erasing, it is important to determine by prior diagnosis that these operations are performed normally. Diagnosis of the erase function is performed by rewriting a predetermined data in a predetermined sector and comparing the data read from an optical disc with original write data. With the increase in the number of erasing and recording processes, the grooves of the guide track of the recording medium are deformed and the recording film is separated from the disk material as a strain of heat cycle. This phenomenon is called the fatigue of the recording medium and sharply deteriorates the bit error rate (BER) of the optical disk. Especially, a long burst that results poses the problem of inaccurate self-­ diagnosis of the erase function making it impossible to determine whether a burst error has been caused by the erasing failure due to an inferior erase function or the deterioration of the recording medium. SUMMARY OF THE INVENTION The object of the present invention is to provide an optical data recording and reproducing apparatus capable of self-diagnosis of the erase function without being affected by the deterioration of the recording medium. According to the present invention, there is provided an optical data recording and reproducing apparatus wherein the number of accumulated tests is written with test data in one of a plurality of erase test sectors of an optical disk, the data read from the erase test sector is compared with the recorded data, or an error is detected by an error correction detection code, so that when the data error detections or the accumulated tests exceeds a predetermined number, a new erase test sector is used in subsequent erase function diagnosis. According to the present invention as configured above, the fatigue of the recording medium which is caused by a defect or a deteriorated erasing efficiency with the increase in the number of erasing is controlled by the number of accumulations. The fatigue of the recording medium and the fault of the erase function are completely separated from each other thereby to improve the reliability of self-diagnosis of the erase function. Self-diagnosis of the erase function is accomplished in such a manner that test data together with the accumulated number of tests are recorded in and read from an erase test sector of the erase self-diagnosis sector, and the recorded data is compared with the read data, or an error is detected by an error correction detection code. When data error detections or the accumulated number of tests exceeds a predetermined level, a marking signal is written in the data field of the particular sector, and a new erase test sector not yet marked is used for subsequent self-diagnosis of erase function thereby making possible erase function self-­ diagnosis without being affected by the fatigue of the recording medium. Any erase test sector with a marking signal, which is detected by sequentially reading the erase test sectors in the beginning of the self-diagnosis, is not used. BRIEF DESCRIPTION OF THE DRAWINGS Fig. l is a block diagram showing an optical data recording and reproducing apparatus according to an embodiment of the present invention. Fig. 2 is a diagram showing a track map accord­ ing to an embodiment of an optical disk having an erase self-diagnosis track. Fig. 3 shows phase changes between amorphous state A and crystal state C of a phase-change recording medium of a conventional optical data recording and reproducing apparatus. Fig. 4 is a diagram for explaining a configura­ tion and distribution of a light beam and erasure and recording thereof for realizing the conditions for temperature increase followed by quenching and tempera­ ture increase followed by annealing of the recording medium. DESCRIPTION OF THE PREFERRED EMBODIMENTS A block diagram of an optical data recording and reproducing apparatus according to an embodiment of the present invention is shown in Fig. l. In Fig. l, numeral l designates a host computer, numeral 2 a memory for writing data or test data and the accumulated number of tests, numeral 3 an ECC encoding section for generat­ ing an error correction code, numeral 4 a data modulator for modulating data with ECC code digitally, numeral 5 an adder for adding a marking signal lll, numeral 6 an optical disk drive, numeral 8 a data demodulator for demodulating a reproduction signal l04 digitally, numeral 8 an ECC decoder for correcting an error, and numeral 9 a read memory for storing data with the error corrected. Numeral l0 designates a comparator for comparing the written data of the write memory 2 with the read data of the read memory 9 and also the accumulated number of tests read with a set number of erasures. Numeral ll designates a marking signal generator-detector for generating a marking signal to be recorded in an erase test sector and detecting a marked signal recorded. Numeral l00 designates an input data signal, numeral l0l a signal for writing data in the optical disk drive, numeral l02 a write gate signal, numeral l03 an erase gate signal, numeral l04 a reproduction signal from the optical disk drive, numeral l05 an output data signal, numeral l06 a record data signal, numeral l07 a read data signal, numeral l08 a data incoincidence signal, numeral l09 a signal indicat­ ing a set number of erasures exceeded, numeral ll0 a marking start signal, numeral lll a marking signal, numeral ll2 a marking detection signal, and numeral ll3 a sector detection signal. Explanation will be made now of the operation of an optical data recording and reproducing apparatus according to the present embodiment configured as above. First, the host CPU l instructs the optical disk drive 6 to seek the erase function self-diagnosis track. The host CPU l identifies a predetermined erase test sector on the basis of the reproduction signal l04 from the optical disk drive 6. Then, the host CPU l reads out an erase test sector. The reproduction signal l04 from the erase test sector is demodulated at the data demodulator 7, so that an error in the data is corrected in the ECC decoder 8 and stored in the read memory 9. The data/number comparator l0 checks whether the accumulated number of tests on the read memory 9 has not exceeded a predetermined number of erasures. If a predetermined number of erasures is not exceeded by the accumulated number of tests thus read, the host CPU l applies a testing recording data to the input data signal l00 and loads the write memory 2. Then, the accumulated number of tests read is incremented, and the resulting number is written in the write memory 2 by the host CPU l. The error correction code is added to the data of the write memory 2 at the ECC encoder 3, and the resulting signal is digitally modulated at the data modulator 4. The write data signal l0l enables the write gate signal l02 and the erase gate signal l03 and applies them to the optical disk drive 6, thereby writing data by erasure or recording in the erase test sector. Next, the host CPU l reads this erase test sector. The reproduction signal l04 from the erase test sector is demodulated at the data demodulator 7, and an error in the data is corrected at the ECC decoder 8 and stored in the read memory 9. The data in the read memory 9 is compared with the write data of the write memory 2 at the data/number comparator l0. If the read data of the read memory 9 coincides with the write data of the write memory 2, the erase function self-­ diagnosis is normal. An error occurrence can be known and the deterioration of the erase test sector can be determined from an error syndrome formed in the ECC decoder 8. In the case where the accumulated number of tests thus read out is found to have exceeded a predeter­ mined number of erasures, the data/number comparator l0 applies the set number of erasures over signal l09 to the host CPU l. If the write data of the read memory 9 fails to coincide with the read data of the write memory 2, on the other hand, the data incoincidence signal l08 is applied to the host CPU l, so that the host CPU l marks the erase test sector. This marking indicates that the particular sector is unusable for an erase test. The host CPU l sets the ID data of the track address and the sector address of the erase test sector in the ID detector l2, and drives the marking signal generator detector ll to start the marking with the marking start signal ll0. Upon detection of the erase test sector by the ID detector l2, the sector detection signal ll3 is applied to the marking signal generator detector ll, with the result that the marking signal lll is applied to the adder 5. The marking signal lll, as a write data signal l0l, is applied together with the write gate signal l02 and the erase gate signal l03 to the optical disk drive 6 and recorded in the data field section l5 of the erase test sector. The marking in the erase test sector is detected at the marking signal generator detector ll on the basis of the reproduction signal l04 of the optical disk drive 6, and applied as a marking detection signal ll2 to the host CPU l. The host CPU l identifies the erase test sector by jumping to a sector not marked. The erase test sector of the erase function self-­ diagnosis track of the new optical disk is initialized before operation. Specifically, with the accumulated number of tests at l, test data are recorded in all the erase test sectors. Then, data are read and compared with the write (recorded) data to check for any defect of the recording medium and write a marking signal in the incoincident sector. By doing so, an erase test sector free of any defect of the recording medium is prepared. A special signal easily distinguished from a burst signal, a pulse train signal, a gated RF signal or other data signal is used as a marking signal. Fig. 2 shows an embodiment of the track map of an optical disk 200 having an erase function self-­ diagnosis track. The optical disk includes an erase function self-diagnosis track 20l for self-diagnosing the erase function, an ID 202 track for recording the control ID data of the optical disk, and a replacement track 205 for replacing defective tracks 203 and user tracks 204 for recording user data. As mentioned above, according to the present embodiment, the accumulated number of tests together with the test data are written in an erase test sector and the record data is compared with the read data thereby to perform self-diagnosis of the erase function. In the case incoincidence as the result of comparison or the accumulated number of tests exceeds a predetermined level, the data field of the particular sector is written with a marking signal. In this way, self-­ diagnosis of the erase function is accurately performed without being affected by the fatigue of the recording medium. In the above-mentioned embodiment, if the erase test is conducted by track instead of by erase test sector, it is possible to diagnose the erase function including the tracking accuracy and the accuracy of alignment of the erase light beam l8 and the recording-­ reproducing light beam l7 on the guide track l3. It will thus be understood from the foregoing description that according to the present invention, self-diagnosis of the erase function is made possible without being adversely affected by the fatigue of the recording medium, thereby resulting in a great practical advantage.

Claims: 1. An optical data recording and reproducing apparatus comprising: an optical disk (200) for recording and reproducing data having an optically detectable guide track (l3) divided into a plurality of sectors each including a sector identifier (l4) and a data field (l5), said optical disk further including a plurality of erase test sectors; means (2, 3, 4) for writing the accumulated number of tests together with test data in an erase test sector; means (7, 8, 9) for reading data from the sector; means (3, 8) for generating and detecting an error of the read data; and means (l0) for checking the accumulated number of tests; said data read means reading the test data and the accumulated number of tests written by said data write means, said data error generation and detection means checking the completeness of the read data thereby to perform the erase function diagnosis; wherein in selected one of the cases where an error is detected by said data error detection means and where the accumulated number of tests exceeds a predeter­ mined level, subsequent erase function diagnosis is effected in a new erase test sector. 2. An optical data recording and reproducing apparatus according to Claim l, further comprising means (ll) for writing a marking signal in the data field of a sector in which an error has been detected by the data error generation and detection means or the test number checking means has detected that the accumulated number of tests has exceeded a predetermined level, wherein the erase function diagnosis subsequent to the writing of a marking signal is performed in a new erase test sector not yet marked. 3. An optical data recording and reproducing apparatus according to Claim l, where said data error detection means detects an erase test sector by checking the presence or absence of a marking signal recorded from the forward end of the erase function self-­ diagnosis track for performing erase function self-­ diagnosis. 4. An optical recording and reproducing apparatus according to Claim l, wherein said data error detection means detects an error by comparing the original test data with read test data. 5. An optical data recording and reproducing apparatus according to Claim l, wherein said data write means adds an error correction detection code to the test data and the accumulated number of tests. 6. An optical data recording and reproducing apparatus according to Claim 5, wherein said data error detection means detects an error exceeding an error correction limit from an error syndrome of the error correction detection code thereby to suspend subsequent erase function diagnosis of the particular sector. 7. An optical data recording and reproducing apparatus accordint to Claim l, wherein said plurality of erase test sectors is written with the accumulated number l of test together with the test data at the start of the optical disk operation. 8. An optical data recording and reproducing apparatus according to Claim l, wherein a value suf­ ficiently smaller than the number of repetitive erasures of the recording medium is set as an accumulated number of tests in said accumulated test number check means. 9. An optical data recording and reproducing apparatus according to Claim l, wherein the erase function diagnosis is effected by track to determine whether the erase light beam and the recording-reproducing light beam are aligned on the same guide track.

Inventors: FUKUSHIMA, YOSHIHISA, ICHINOSE, MAKOTO, KUROKI, YUZURU, SATOH, ISAO,, TAKAGI, YUJI
Applicants: MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1986
Main classification: G11B27
IPC codes: G11B27, G11B20, G11B7