Optical information recording and reproducing apparatus having an improved detection system for detecting fouling of a disk or an internal optical system

The apparatus includes a one-chip microcontroller, an error flag counter and an error comparison circuit to detect whether or not an optical disk or an internal optical head of the apparatus is fouled. Test data is recorded on a self-diagnostic area of the optical disk when the optical disk loaded in the apparatus is new and has not yet been used, and initial error information detected in the test data reproduced from the self-diagnostic area is registered on an error managing area of the optical disk. When an optical disk which has already been used is loaded, error information detected in the test data recorded on and reproduced from the self-diagnostic area of the optical disk is compared with the initial error information registered in the error managing area of the optical disk. When the comparison shows that the number of data errors is greater than a predetermined reference value, the optical disk or the internal optical head is fouled to such an extent that the recording and reproducing function cannot be satisfactorily performed.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an optical information recording and reproducing 
apparatus. 
2. Description of Related Art 
FIG. 6 is a block diagram showing the structure of a prior art optical 
information recording and reproducing apparatus using an optical disk. 
Referring to FIG. 6, an optical disk 1 is rotated by a drive motor 2. An 
optical head 3 writes information on the optical disk 1 by directing a 
focused laser beam onto the optical disk 1 and reads out the recorded 
information by detecting a change in the laser beam focused and reflected 
from the optical disk 1. A laser drive/head amplifier circuit 4 includes a 
laser drive part for driving the laser source of the optical head 3 and a 
head amplifier part for detecting a focusing error signal 100, a tracking 
error signal 101 and a reproduced information signal 102. An actuator for 
actuating the optical head 3 is driven by a focusing control circuit 5 to 
which the focusing error signal 100 is applied, so that the laser beam can 
be accurately focused on a guide track of the optical disk 1. The actuator 
actuating the optical head 3 is also driven by a tracking control circuit 
6 to which the tracking error signal 101 is applied, so that the laser 
beam can accurately trace the guide track of the optical disk 1. A data 
modulation/demodulation circuit 7 modulates input data 103 to produce a 
data signal 104 to be recorded on the optical disk 1 and demodulates the 
signal 102 reproduced from the optical disk 1 to deliver it as output data 
105. A control CPU 8 controls the information recording and reproducing 
system of the apparatus. 
In the prior art optical information recording and reproducing apparatus 
having a structure as described above, the optical head 3 converges the 
laser beam and directs the focused laser beam onto a guide track of the 
optical disk 1 rotating at a predetermined constant high speed. A focusing 
error signal 100 and a tracking error signal 101 detected by the head 
amplifier part of the laser drive/head amplifier circuit 4 are applied to 
the focusing control circuit 5 and the tracking control circuit 6 
respectively, and these control circuits 5 and 6 drive the actuator 
actuating the optical head 3 for carrying out the focusing control and 
tracking control respectively, so that the focused laser beam can be 
accurately directed onto the guide track of the optical disk 1. 
In the data recording mode, the data modulation/demodulation circuit 7 
modulates input data 103 to produce a data signal 104 to be recorded on 
the optical disk 1. 
This signal 104 is applied to the laser drive/head amplifier circuit 4 to 
modulate the laser beam which has a recordable intensity, and the optical 
head 3 directs the laser beam onto the optical disk 1 to record the data. 
On the other hand, in the data reproduction mode, the laser beam, whose 
level is too low to record any data, is directed from the optical head 3 
onto the optical disk 1. The laser drive/head amplifier circuit 4 receives 
the reflection of the focused laser beam from the optical disk 1 to 
reproduce the signal 102, and this reproduced signal 102 is demodulated in 
the data modulation/demodulation circuit 7 to appear as output data 105. 
However, when the optical disk 1 in the prior art optical information 
recording and reproducing apparatus having a structure as described above 
is continuously used for a long period of time and rotated at high speed, 
the optical disk 1, whose basic material is an electrical insulating resin 
or glass, becomes electrostatically charged, and dust floating in the 
ambient air is attracted to the surface of the optical disk 1. Also, dust 
intruding into the apparatus attaches to parts such as optical disk 1 and 
the lens. Because the attracted dust absorbs and scatters the laser beam, 
the recording and reproducing power of the laser beam is lowered by about 
several-ten percents. As a result, the recording and reproducing power of 
the laser beam to be directed onto the recording layer deposited on the 
guide tracks of the optical disk 1 is greatly diminished, and signals 
cannot be satisfactorily recorded on and reproduced from the optical disk 
1. 
This gives rise to a decreased amplitude of the reproduced signal and 
corresponding degradation of the bit error rate. Further, because the 
reduced recording power of the laser beam results in corresponding 
insufficient formation of recording pits, the prior art optical 
information recording and reproducing apparatus has had such a 
disadvantage that the progressive deterioration of the recording pits with 
time leads to a shortened useful service life of the optical disk. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an optical information 
recording and reproducing apparatus in which means are provided so as to 
detect whether or not an optical disk or an internal optical system of the 
apparatus is fouled with dust. 
In accordance with the present invention, there is provided an optical 
information recording and reproducing apparatus comprising recording and 
reproducing means for recording and reproducing information on and from an 
optical disk loaded in the apparatus; status-of-use checking means for 
checking whether the loaded optical disk is new and has not yet been used 
or has already been used; error detecting means recording and reproducing 
test data on and from a self-diagnostic area of the optical disk for 
detecting error information from the reproduced test data; error 
information recording means for registering, on an error managing region 
of the optical disk, the error information detected when the 
self-diagnostic area of the optical disk is first used; and error 
comparing means for comparing the error information detected by the error 
detecting means with the initial error information reproduced from the 
error managing area of the optical disk. 
In the optical information recording and reproducing apparatus of the 
present invention, whether an optical disk loaded in the apparatus is new 
and has not yet been used or has already been used is checked. When the 
result of checking proves that the loaded optical disk has not yet been 
used, test data is recorded on and reproduced from the self-diagnostic 
area of the optical disk, and initial error information detected in the 
reproduced test data is registered on the error managing area of the 
optical disk. On the other hand, when the result of checking proves that 
the loaded optical disk has already been used, error information detected 
in the test data recorded in and then reproduced from the self-diagnostic 
area is compared with the initial error information reproduced from the 
error managing area. When the result of comparison proves that the number 
of detected errors is more than that detected at the beginning of the use 
of the optical disk, fouling of the optical disk or the internal optical 
system is detected.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 is a block diagram showing the structure of a first embodiment of 
the present invention. Referring to FIG. 1, a one-chip microcontroller 11 
controls the overall apparatus in response to a device command 110 
transmitted from a host computer 10. A drive unit 12 sends out signals 112 
reproduced from sectors of an optical disk (not shown) by an optical head 
(not shown). The one-chip microcontroller 11 instructs a target sector 
address 113, and a sector detection circuit 13 detects the instructed 
target sector address 113 among the reproduced signals 112 sent out from 
the drive unit 12. An envelope detection circuit 24 detects an envelope 
signal representing data contained in the signal 112 reproduced from the 
target sector of the optical disk. A demodulation circuit 14 demodulates 
the data contained in the reproduced signal 112 and applies its output 
signal 115 representing the demodulated data to a decoder 16 and a data 
buffer 22. A modulation circuit 15 modulates data and applies its output 
signal 114 representing the modulated data to be recorded on the optical 
disk to the drive unit 12. The decoder 16 detects and corrects errors that 
may be included in the demodulated data 115, and, when errors are 
detected, applies error flags 120 corresponding to the number of detected 
errors to an error flag counter 25 which counts the number of the error 
flags 120. An encoder 17 adds an error detection and correction code to 
buffer data 117 derived from the data buffer 22. An error comparison 
circuit 20 compares error information data 121 read out from an error 
information memory 23 with error total-number data 122 supplied from the 
one-chip microcontroller 11. 
FIG. 2 shows an arrangement of various areas of an optical disk preferably 
used in the apparatus of the present invention. Referring to FIG. 2, the 
optical disk includes a self-diagnostic area 32 for recording test data to 
be reproduced so as to detect error information, an error managing area 31 
for registering initial error information detected as a result of the 
reproduction of the test data recorded on the self-diagnostic area 32, and 
a user's area 33 for recording user's data thereon. 
The flow chart of FIG. 3 illustrates the steps of self-diagnostic operation 
carried out in the first embodiment of the optical information recording 
and reproducing apparatus having a structure as described above when an 
optical disk having various areas as shown in FIG. 2 is newly loaded. 
Step 1 
A drive interrupt signal 123 is applied to the one-chip microcontroller 11 
from the drive unit 12. In response to this drive interrupt signal 123, 
the one-chip microcontroller 11 sends out to the drive unit 12 a drive 
command 124 requesting the status of the disk drive in the drive unit 12. 
In response to the drive command 124, the drive unit 12 applies a drive 
status signal 125 to the one-chip microcontroller 11, and, by checking 
this drive status signal 125, the one-chip microcontroller 11 detects that 
an optical disk is newly loaded in the apparatus. 
Step 2 
As a target sector address 113, the one-chip microcontroller 11 selects a 
sector address in the error managing area 31 of the optical disk and 
applies such an address signal 113 to the sector detection circuit 13. In 
response to this address signal 113, the sector detection circuit 13 
detects sector address information contained in the signal 112 reproduced 
from the selected sector and applied from the drive unit 12, so as to 
detect coincidence between the target sector address 113 and the sector 
address information. When the target sector is detected as a result of the 
coincidence detection, the sector detection circuit 13 generates a sector 
detection signal 126 so as to activate the envelope detection circuit 24 
and the demodulation circuit 14. 
When the envelope detection circuit 24 detects an envelope signal of 
representing data contained in the reproduced signal 112, it applies an 
envelope detection signal 131 to the one-chip microcontroller 11. The 
one-chip microcontroller 11 checks to determine whether or not the 
envelope detection signal 131 is detected within a rotational delay time 
corresponding to one sector. When the result of checking proves that the 
envelope detection signal 131 is not detected because the optical disk is 
new and has not been used yet, step 2 is followed by step 3. On the other 
hand, when the result of checking proves that the optical disk has been 
used already, step 2 is followed by step 7. 
Step 3 
As the target sector address 113, the one-chip microcontroller 11 selects a 
sector address in the self-diagnostic area 32 of the optical disk and 
applies such an address signal 113 to the sector detection circuit 13. In 
response to the address signal 113, the sector detection circuit 13 
detects sector address information contained in the signal 112 reproduced 
from the selected sector and applied from the drive unit 12, so as to 
detect coincidence between the target sector address 113 and the sector 
address information. When the target sector is detected as a result of the 
coincidence detection, the sector detection circuit 13 generates the 
sector detection signal 126 so as to activate the modulation circuit 15. 
First, test data 118 read out from a test data memory 21 is supplied to the 
data buffer 22 to appear as buffer data 117 from the data buffer 22. The 
encoder 17 adds an error detection and correction code to the buffer data 
117 to provide coded data 129 which is supplied to the modulation circuit 
15. The modulation circuit 15 modulates the coded data 129 to produce a 
signal 114 to be recorded, and this signal 114 is applied to the drive 
unit 12 to be recorded on the self-diagnostic area 32 of the optical disk. 
The one-chip microcontroller 11 selects a sector address in the 
self-diagnostic area of the optical disk as the target sector address 113 
again and applies such an address signal 113 to the sector detection 
circuit 13. The sector detection circuit 13 detects sector address 
information contained in the signal 112 reproduced from the selected 
sector and applied from the drive unit 12, so as to detect coincidence 
between the target sector address 113 and the sector address information. 
When the target sector is detected as a result of the coincidence 
detection, the sector detection circuit 13 generates the sector detection 
signal 126 so as to activate the demodulation circuit 14. 
The demodulation circuit 14 demodulates the reproduced signal 112 applied 
from the drive unit 12 while discriminating data contained in the 
reproduced signal 112 and supplies the demodulated data 115 to the decoder 
16. 
Step 4 
The decoder 16 detects and corrects errors included in the demodulated data 
115. That is, the decoder 16 carries out error correction by grouping 
errors into an error syndrome, calculating the number of error symbols for 
each individual code word, and finding error symbol locations and error 
symbol values. For the purpose of this manner of error detection and 
correction, a BCH code is used. Such a method of error detection and 
correction by the use of the BCH code is described in detail in chapter 9 
of a book entitled "ERROR-CORRECTING CODES", SECOND EDITION (W. Wesley 
Peterson and E. J. Weldon Jr., The MIT PRESS, CAMBRIDGE MASSACHUSETTS AND 
LONDON, ENGLAND, 1975). 
In the course of error detection and correction the decoder 16 detects the 
number of error symbols for a given code word and sends out an error flag 
120 representing the number of error symbols to the error flag counter 25. 
The error flag counter 25 sends out the count of the error flags 120 
representing the same number to the one-chip microcontroller 11 as error 
data 128. In the one-chip microcontroller 11, the count of the error flags 
120 representing the same number is multiplied by the number of the error 
symbols represented by that error flag 120 to calculate the total number 
of the error symbols. 
Suppose, for example, that the decoder 16 can detect a maximum of three 
error symbols for each individual code word, and there are L.sub.1, 
L.sub.2 and L.sub.3 code words having one, two and three error symbols 
respectively. When the decoder 17 detects one, two or three error symbols 
in each individual code word, an error flag 120 indicating one, two or 
three errors is sent out from the decoder 16 to the error flag counter 25. 
Thus, the one-chip microcontroller 11 receiving the error data 128 from 
the error flag counter 25 is informed that there are L.sub.1, L.sub.2 and 
L.sub.3 code words having one error symbol, two error symbols and three 
error symbols respectively. The one-chip microcontroller 11 calculates the 
total number of error symbols according to the following equation: 
EQU (Total number of error sumbols)=L.sub.1 .times.1+L.sub.2 .times.2+L.sub.3 
.times.3 
Step 5 
When the one-chip microcontroller 11 finds that the total number of error 
symbols is equal to or larger than a predetermined reference value N, it 
decides that the optical disk or the internal optical system of the 
apparatus is fouled to such an extent that the optical information 
recording and reproducing function cannot be normally performed. In this 
case, step 5 is followed by step 9. 
Step 6 
When the total number of error symbols is smaller than the predetermined 
reference value N, error total-number data 122 obtained by formatting the 
total number of error symbols is sent out to the data buffer 22 from the 
one-chip microcontroller 11. 
Further, the one-chip microcontroller 11 selects a sector address in the 
error managing area 31 of the optical disk as the target sector address 
113 and applies such an address signal 113 to the sector detection circuit 
13. The sector detection circuit 13 detects sector address information 
contained in the signal 112 reproduced from the selected sector and 
applied from the drive unit 12, so as to detect coincidence between the 
target sector address and the sector address information. When the target 
sector is detected as a result of the coincidence detection, the sector 
detection circuit 25 generates the sector detection signal 126 for 
activating the modulation circuit 15. 
The error total-number data 122 supplied to the data buffer 22 from the 
one-chip microcontroller 11 appears as buffer data 117 from the data 
buffer 22, and the encoder 17 adds the error detection and correction code 
to the buffer data 117 to provide coded data 129 which is supplied to the 
modulation circuit 15. The modulation circuit 15 modulates the coded data 
129 to produce a signal 114 to be recorded, and this signal 114 is applied 
to the drive unit 12. Thus, the total number of initial error symbols 
detected on the self-diagnostic area 32 is now recorded on the error 
managing area 31 of the optical disk, thereby completing execution of the 
self-diagnostic operation. 
Step 7 
This step is executed when the result of checking in the step 2 proves that 
the optical disk is not new and has already been used. 
The demodulation circuit 14 demodulates the reproduced signal 112 applied 
from the drive unit 12 while discriminating data contained in the 
reproduced signal 112 and supplies the demodulated data 115 to the decoder 
16. The decoder 16 detects and corrects errors included in the demodulated 
data 115 and supplies reproduced data 116 to the data buffer 22. Further, 
the data representing the total number of initial error symbols detected 
on the self-diagnostic area 32 of the optical disk by recording and 
reproducing test data thereon and derived from the data buffer 22 as 
buffer data 117 is stored in the error information memory 23 under control 
of the one-chip microcontroller 11. 
Step 8 
The error total-number data 122 obtained by formatting the total number of 
error symbols is sent out to the data buffer 22 from the one-chip 
microcontroller 11. 
The error comparison circuit 20 compares the buffer data 117 derived from 
the data buffer 22 with the error information data 121 read out from the 
error information memory 23 to calculate the ratio between the data 117 
and 121. When the calculated ratio is equal to or larger than a 
predetermined reference value M, the optical disk or the internal optical 
system of the apparatus is fouled, and the optical information recording 
and reproducing function cannot be normally performed. A signal 130 
indicating the impossibility of normally performing the recording and 
reproducing function is applied from the error comparison circuit 20 to 
the one-chip microcontroller 11. On the other hand, when the ratio 
described above is smaller than the predetermined reference value M, the 
optical information recording and reproducing function is normal, and the 
execution of the self-diagnostic operation is completed. 
Step 9 
When, in response to the device command 110 transmitted from the host 
computer 10, the one-chip microcontroller 11 applies sense information 111 
to the host computer 10 to inform the host that the optical disk or the 
internal optical system is fouled, and the optical information recording 
and reproducing function cannot be normally performed, the execution of 
the self-diagnostic operation is completed. 
In step 2, the envelope detection circuit 24 can detect the envelope signal 
by detecting that a retriggerable monostable multivibrator, to which the 
binary reproduced signal 112 is applied as an input, generates an output 
which becomes continuously active by a number of times which is a 
predetermined multiple of the time constant T of the multivibrator. The 
fact that the output of the multivibrator becomes continuously active can 
be confirmed by detecting that the output becomes active by k times as a 
result of sampling the output by n times. Further, although a 
determination is made as to whether or not the optical disk has already 
been used is made on the basis of the envelope detection signal 131, it 
can be decided on the basis of a busy signal 127 generated from the 
demodulation circuit 14 when the demodulation circuit 14 is activated by 
the signal 126 produced on the basis of the signal 112 reproduced from the 
recorded sector. 
Further, those skilled in the art will readily understand that the host 
computer 11 can perform the functions of the error flag counter 25 and 
error comparison circuit 20 employed in the first embodiment. 
It will be seen from the above description that, in the first embodiment of 
the optical information recording and reproducing apparatus of the present 
invention, the error flag counter 25 counts the number of error flags 120 
detected by the decoder 16 when an optical disk which is new and has not 
yet been used commenses use for optical information recording and 
reproduction and also during the use of the optical disk for the same 
purpose. The total number of the error symbols counted in the latter case 
is compared in the error comparison circuit 20 with that counted in the 
former case. When an increase in the data errors is detected as a result 
of the error flag comparison in the error comparison circuit 20, the 
one-chip microcontroller 11 can detect that the optical information 
recording and reproducing function cannot be normally performed due to, 
for example, fouling of the optical disk or the internal optical system of 
the apparatus. 
FIG. 4 is a block diagram showing the structure of a second embodiment of 
the optical information recording and reproducing apparatus of the present 
invention. In FIG. 4, the reference numerals 10 to 17, 24, 110 to 118 and 
121 to 131 designate the same parts and signals as those used in the first 
embodiment shown in FIG. 1. Referring to FIG. 4, an error bit detection 
circuit 18 compares buffer data 117 derived from the data buffer 22 with 
test data 118 read out from the test data memory 21 to detect error 
information. An error bit counter 19 counts error bits represented by an 
output signal 119 of the error bit detection circuit 18. 
The arrangement of various areas of an optical disk preferably used in the 
second embodiment of the present invention is the same as that of the 
optical disk shown in FIG. 2. 
The self-diagnostic operation of the second embodiment of the optical 
information recording and reproducing apparatus having the illustrated 
structure, when an optical disk is newly loaded, will be described with 
reference to a flow chart of FIG. 5. 
In the following description, operations in steps 1, 2 and 9 in FIG. 5 are 
the same as those in steps 1, 2 and 9 respectively in FIG. 3, and 
operations in steps 12 to 15 in FIG. 5 are also the same as those in steps 
5 to 8 respectively in FIG. 3, except that the term "error symbol" is 
replaced by the term "error bit". Therefore, those steps need not be 
described again, and operations in steps 10 and 11 will only be described 
herein. 
Step 10 
As in case of the step 3, test data is recorded on and reproduced from the 
self-diagnostic area 32 of the optical disk. However, step 10 differs from 
step 3 in that, buffer data 117 is directly supplied to the modulation 
circuit 15 without being passed through the encoder 17, whereas coded data 
129 provided by adding the error detection and correction code to test 
data 118 by the encoder 17 is supplied to the modulation circuit 15 in 
step 3. 
Step 11 
Error information is detected by the error bit detection circuit 18. First, 
the demodulation circuit 14 demodulates a reproduced signal 112 applied 
from the drive unit 12 while discriminating data contained in the signal 
112, and the demodulated data 115 from the demodulation circuit 14 is 
directly supplied to the data buffer 22 without being passed through the 
decoder 16. In the error bit detection circuit 18, the buffer data 117 
derived from the data buffer 22 is compared bit-to-bit with the test data 
118 read out from the test data memory 21, and, each time non-coincidence 
therebetween is detected, an error bit detection signal 119 is applied to 
the error bit counter 19. The data representing the number of error bit 
detection signals 119 counted by the error bit counter 19 is supplied to 
the one-chip microcontroller 11 as error data 128. The value of this error 
data 128 represents the total number of occurred error bits. 
The error bit detecting operation of the error bit detection circuit 18 and 
the error bit counting operation of the error bit counter 19 in the second 
embodiment can be easily realized by means of software prepared in the 
one-chip microcontroller 11 to dispense with the provision of such 
hardware parts. Also, the operations of the error bit detection circuit 
18, error bit counter 19 and error comparison circuit 20 can be easily 
done by the host computer 10. 
Further, the operation of the error comparison circuit 20 in each of the 
first and second embodiments may also be easily realized by means of 
software prepared in the one-chip microcontroller 11. Further, although 
the test data 118 recorded on the optical disk so as to obtain error 
information is stored in the test data memory 21, the test data 118 may be 
supplied from the host computer 10. 
In the second embodiment of the optical information recording and 
reproducing apparatus having features as described above, the error bit 
detection circuit 18 detects error bits included in demodulated data not 
subjected to error correction, and the error bit counter 19 counts the 
total number of such error bits. The total number of error bits counted 
when use is commenced of an optical disk, which is new and has not yet 
been used, for the optical information recording and reproducing purpose 
and that counted during the use of the optical disk for the same purpose 
are compared in the error comparison circuit 20. When an increase in the 
data errors is detected as a result of the error bit comparison in the 
error comparison circuit 20, the one-chip microcontroller 11 can detect 
that the optical information recording and reproducing function cannot be 
normally performed due to, for example, fouling of the optical disk or the 
internal optical system of the apparatus. 
In the aforementioned embodiments of the present invention, the 
self-diagnostic operation for detecting fouling of an optical disk or the 
internal optical system of the apparatus starts when the optical disk is 
loaded in position in the apparatus. However, this self-diagnostic 
operation may start when the power supply for the apparatus is turned on 
or when a device command 110 requesting diagnosis is transmitted from the 
host computer 10. Therefore, the self-diagnostic operation is also carried 
out even in an optical information recording and reproducing apparatus of 
the type in which an optical disk is completely enclosed. 
It will be understood from the foregoing detailed description that the 
present invention provides an optical information recording and 
reproducing apparatus in which fouling of an optical disk or its internal 
optical system is detected by comparing the total number of errors 
detected when use is commenced of the optical disk, which is new and has 
not yet been used, for optical information recording and reproduction with 
that detected during the use of the optical disk, thereby detecting an 
increase in errors included in recorded and reproduced test data. 
Therefore, fouling of the optical disk and the internal optical system of 
the apparatus can be detected with high reliability, and the apparatus has 
great practical advantages and effects.