JPH0713052Y2 - Disk type recording medium tester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial field of use The present invention relates to a disk type recording medium used for inspecting the quality of the recording surface of a disk type recording medium such as a hard magnetic disk at the time of manufacturing or before assembly. Regarding the tester.

2. Description of the Related Art As a method for inspecting the quality of the recording surface of a disk type recording medium such as a hard magnetic disk, the following method has been implemented. That is, a test signal of a constant level is first written over the entire track of the recording medium, the written test signal is read next, and the average level of the read signal for each track is obtained by the average level detector. Then, the average level of the read signal obtained by the read level detector is compared with the read signal. Then, when the read output is outside the frame of the reference value using a constant value determined based on the average level as a reference value, this is detected as a read error, and the quality of the recording medium is determined by the presence or absence of the error signal. It is to inspect.

The conventional tester used for the quality inspection as described above includes a single read / write head, and the single read / write head is used to both write and read a test signal.

However, in the conventional disk type recording medium tester, the inevitable result of using a single head is to write a test signal using the head over the entire track of the recording medium. Then, the written test signal had to be read again by the same head over the entire track. Furthermore, the average level of the read signal for each track is calculated,
Since the average level is compared with the read signal, the test signals are read twice by the same head (read for obtaining the average level of the read signal and read for comparing the average level and the read signal). Had to do.

For this reason, when inspecting the quality of the one-sided disk type recording medium, the recording medium must be rotated 3 degrees over the entire track in order to perform writing and reading twice with one read / write head. It was

Further, in order to erase the test signal and check the erase error after the inspection, it was necessary to rotate the disk type recording medium twice as well.

If the retry is performed (the test signal is read again for inspection for confirmation) in order to improve the inspection accuracy, the number of rotations of the recording medium must be further increased.

Therefore, in the conventional single-head tester, the recording medium must be rotated over the entire track by a total of 5 degrees or more by the end of the entire quality inspection process for the one-sided disk type recording medium. There was a problem that the inspection took too long.

The present invention has been made in view of the above points, and an object thereof is to provide a disk-type recording medium tester capable of inspecting the quality of the recording surface of the disk-type recording medium in a short time.

Means for Solving the Problems A disk type recording medium tester according to the present invention comprises a drive device for rotationally driving a disk type recording medium to be inspected, and a drive device for separating the disk type recording medium at a predetermined interval in the circumferential direction of the rotation. A write head and at least two read heads for writing or reading a signal on the recording surface of the disk-type recording medium, the write head and the at least two read heads each being radially movable by a carriage. A write circuit for supplying a predetermined test signal to the write head is provided independently for each read head, and the level of the read signal from the corresponding read head is compared with the reference level. An inspection circuit that outputs a signal indicating the presence or absence of a recording error, and an output signal of each inspection circuit corresponding to each of the read heads are provided to separate the head separation distance. And an error signal forming circuit for forming an error signal indicating the presence or absence of a recording error by taking the logical product of the output signals of the respective synchronized inspection circuits. It is characterized in that writing by the write head and reading by the read heads are performed in parallel on adjacent tracks.

Since the write head and each read head are provided independently, when the disk type recording medium to be inspected is rotated at the same time, the write head writes the test signal and each read head outputs the test signal. Can be read in parallel. That is, it is possible to control the writing by the writing head and the reading by the respective reading heads in parallel with respect to the same or adjacent tracks on the disk type recording medium, whereby the writing and the reading of the test signal can be performed at the same rotation. You will be able to do it at the same time. Similarly, when erasing test data after inspection, it is possible to perform erasing by the write head and erasure error check by the read head in parallel during the same rotation of the disk type recording medium. .

An error signal indicating the presence or absence of a recording error is obtained by synchronizing the output signals of the respective inspection circuits corresponding to the respective read heads in accordance with the spacing between the heads and taking the logical product of the synchronized respective inspection circuit output signals. So that
Only when the same error is detected based on the read signals of at least two read heads, the error can be treated as a true error, and the inspection accuracy is improved.

When the average level of the read signal for one track is used as the reference level, the inspection circuit obtains an average level of the read signal for one track from each read head, and an average level detection circuit. It is preferable to include an error detection circuit that compares the read signal of the next track with the average level of each track obtained by the level detection circuit as a reference level and outputs a signal indicating the presence or absence of the recording error. . By doing so, it becomes possible to perform the reading for the inspection and the reading for obtaining the average level at the same time, and it becomes unnecessary to perform the reading only for obtaining the average level as in the conventional case.

Further, in order to efficiently perform the retry, it is preferable that a plurality of the read heads are provided separately from each other and the read signals of the read beds are simultaneously inspected at the same rotation. By doing so, the original inspection and the inspection as the retry can be performed at the same time by rotating the disc-type recording medium to be inspected almost once for each track, so that it is possible to perform the inspection with higher accuracy. Become.

Embodiment Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is an electrical block diagram showing an embodiment of a disk type recording medium tester according to the present invention. This tester has
A drive device 4 for rotating and driving a hard magnetic disk to be inspected is provided, and the hard magnetic disk is detachably set in the drive device 4 and is inspected. The arrow on the outside of the circumference of the drawing indicates the rotation direction of the drive device 4.

The write head 1 is for writing a test signal on the hard magnetic disk set in the drive device 4, and the read head 2 and the re-read head 3 are for writing the test signal on the magnetic disk. It is for reading. The write head 1, the read head 2, and the reread head 3 have a circumference of rotation of the drive device 4 in the order in which the read head 2 first reads the signal written by the write head 1. Are arranged at predetermined intervals in the direction, and can be independently moved in the radial direction by a carriage (not shown). These three heads are adapted to write and read in parallel on the same or adjacent tracks on the hard magnetic disk.

The write circuit 5 is for supplying a predetermined test signal to the write head 1, and the test signal output from the write circuit 5 is written by the write head 1 on the hard magnetic disk. Be done. In this example, the writing circuit 5 writes a signal of a constant level over the entire track.

On the other hand, the test signal read from the magnetic disk by the read head 2 and the reread head 3 is input to the inspection circuits 6a and 6b. The inspection circuits 6a and 6b have exactly the same configuration, and the amplification circuits 7a and 7b, the average level detection circuits 8a and 8b, and the error detection circuit 9a and
Includes 9b.

The amplifier circuits 7a and 7b receive the read signals output from the read head 2 and the reread head 3, respectively, and amplify the read signals to the average level detection circuits 8a and 8b and the error detection circuits 9a and 9b. It is for output.

The average level detection circuits 8a and 8b are for obtaining the average level of the input read signal for one track. The read signals output from the read head 2 and the reread head 3 are the amplification circuits 7a and 7b, respectively.
Is inputted to the average level detection circuits 8a and 8b via the, and the average level of the read signal level for each track is obtained here. The signals representing the average level are output to the error detection circuits 9a and 9b, respectively.

The error detection circuits 9a and 9b are output from the read head 2 and the reread head 3, respectively, and amplified by the amplifier circuits 7a and 7b.
The read signal amplified by and the average level signal of the read signal for each track output from the average level detection circuits 8a and 8b are input. The error detection circuits 9a and 9b are for comparing with the read signal using the input average level as a reference level.
At that time, the average level of the read signal of the track immediately before the track currently being read is used as the reference level. Then, as a result of the comparison, a signal indicating the presence or absence of a recording error is output from the error detection circuit depending on whether or not the level of the read signal is within a predetermined allowable range based on the reference level (reference level If it is less than the allowable range according to, an error is detected and the signal "1" is output.

By using the inspection circuits 6a and 6b including the above circuits, the read head 2 is read from the hard magnetic disk.
It is possible to detect the recording error of the test signals read by the rereading head 3.

Next, the signals indicating the presence / absence of the recording error output from the error detection circuits 9a and 9b in the inspection circuits 6a and 6b are input to the error signal forming circuit 10. Error signal forming circuit 10
Includes a position synchronization circuit 11 and an AND circuit 12, but the signal output from the error detection circuit 9a is the position synchronization circuit 11
To the AND circuit 12 and then to the error detection circuit
The signal output from 9b is directly input to the AND circuit 12. As described above, on the drive device 4, the test signals recorded on the hard magnetic disk are separated by a predetermined interval so that the read head 2 first reads the test signal and then the reread head 3 reads it. The read signal output from the read head 3 has a certain time delay with respect to the read signal output from the read head 2 at the same location. Correspondingly, the signal indicating whether or not there is a recording error output from the error detection circuit 9b also has a certain time delay with respect to the signal output from the error detection circuit 9a. The position synchronization circuit 11 has a function of delaying the input signal by the same time as the time delay of the error detection circuit 9b.
It is provided for the purpose of synchronizing the output signal of the above and the output signal of the error detection circuit 9b.

The position synchronization circuit 11 synchronizes the signals, which are output from the error detection circuits 9a and 9b and indicate the presence or absence of the recording error, and are input to the AND circuit 12. The AND circuit 12 takes the logical product of the signals output from both error detection circuits 9a and 9b,
Both of the error detection circuits 9a and 9b output error signals only for those detected as recording errors.

The recording errors respectively detected by the inspection circuits 6a and 6b are synchronized and logically ANDed by the error signal forming circuit 10 having the above-mentioned configuration, and an error signal is formed.

The error signal formed by the error signal forming circuit 10 is stored in the buffer memory 13. The buffer memory
The error signal stored in 13 is processed by a CPU (central processing unit of computer) 14. Since the inspection result is temporarily stored in the buffer memory 13 as described above, the inspection of the hard magnetic disk by the tester of the present invention and the processing by the CPU 14 can be performed asynchronously, and the disk to be inspected is rotated regardless of the processing time of the CPU 14. Can be continuously performed, and the inspection time can be shortened.

Next, an example of the read / write operation of each head 1, 2, 3 at the time of disc inspection will be described. First, the write head 1 starts writing from the start point of the first track, and the start point of the first track is the read head 2. When the head 2 starts to read the first track, and when the starting point of the first track reaches the position of the reread head 3, the head 3 starts to read the first track,
In this way, writing and reading of the same track are performed by the heads 1, 2, and 3 almost at the same time. Writing bed 1 is first
When the writing of the track is completed, the process then shifts to the writing of the second track. At this time, the read head 2 and the re-read head 3 are still reading the remaining portion of the first track, but at an appropriate time. After each head 2,3
Shifts to the reading of the second track. In this way, the heads 1, 2 and 3 perform writing and reading in parallel with respect to the same or adjacent tracks, and the inspection tracks are switched one after another.

The read signals output from the read head 2 and the reread head 3 during the above-described write and read operations are input to the inspection circuits 6a and 6b, respectively. Here, the reading of the track currently under inspection is performed. Signal is error detection circuit 9a
9b and 9b as signals to be inspected and also to the average level detection circuits 8a and 8b for obtaining the average level to be the reference level of the next track. On the other hand, during the read operation of the track, the average level obtained in the previous track is continuously supplied to the error detection circuits 9a and 9b. Thus, as described above, the comparison between the read signal of the track currently under inspection and the average level of the read signal of the previous track is made. Here, if there is no storage error, the signal "0" is output, and if there is a recording error, the signal "1" is output from the error detection circuits 9a and 9b. The read signal of the next track is also input to the error detection circuits 9a and 9b as the signal to be inspected and compared with the reference level to detect the recording error, and further averaged to create the reference level of the next track. The input to the level detection circuits 8a and 8b is repeated. As described above, the read signals of the respective tracks output from the read head 2 and the reread head 3 are error detection circuits as the read signals of the current track.
It is input to 9a and 9b and also used by the error detection circuits 9a and 9b as a reference level of the read signal of the next track through the average level detection circuits 8a and 8b. Therefore, in order to detect a recording error by the inspection circuits 6 (a) and 6 (b), the test data written on the hard magnetic disk only needs to be read once. With only one rotation per track of the magnetic disk, it is possible to inspect the recording error twice by two pairs of independent read heads and inspection circuits. However, when the first track of the hard magnetic disk to be inspected is read, there is no read signal of the previous track that should be the reference level, so only the first track is 2
It is necessary to take another method such as rotating the same multiple times and using the average level obtained by the first rotation as the reference level.

Further, the signals indicating the presence / absence of a recording error detected by the above-mentioned two pairs of independent reading heads and the inspection circuit are ANDed by the error signal forming circuit 10, and both the inspection circuits judge that there is a recording error. If it is not, an error signal is not formed, so that a more accurate inspection can be performed.

Further, the test signal written for the inspection needs to be erased after the inspection is completed, but since the writing head and the reading head are independent, the erasing and reading by the writing head are performed in the same manner as described above. It is possible to perform an erasure error check by a recording head in parallel with the same rotation of the hard magnetic disk.

As described above, by using the disk-type recording medium tester according to the present embodiment, two independent inspections (inspection and retry) and erasure and erasure error check for the hard magnetic disk on one side are performed. It will be completed only by rotating the track a total of two times.

In the embodiment, the read head 2 is used as a head for reading the test signal written on the hard magnetic disk.
And the rereading head 3 are provided, but the number of the heads may be one or three or more. In one case, two revolutions per track would result in two tests, including retries. Further, in the case of three or more, it becomes possible to perform an inspection including a plurality of retries twice or more within the same rotation.

Although the error forming circuit 10 includes the AND circuit 12 in the embodiment shown in the figure, the error forming circuit 10 may include an OR circuit instead of the AND circuit 12. When the OR circuit is included, the error forming circuit 10 forms an error signal when at least one of two independent inspections (inspection and retry) detects a recording error.

The present invention is not limited to magnetic disks, but can be applied to other disk type recording media.

As described above, according to the present invention, the write head and the at least one read head are arranged at predetermined intervals in the circumferential direction of the drive device, and each of them is radially moved by the carriage. Since it is movable and an independent inspection device is provided for each read head, the disk-type recording medium to be inspected can be rotated about once per track, and the test signal Writing and reading (including retries in the case of multiple read heads) can be performed in parallel. Similarly, when the written test signal is erased and the erase error check is performed,
It can be done in parallel with just one revolution per track. Therefore, in order to complete the entire process of the quality inspection of the recording surface of the conventional disc type recording medium, it is necessary to rotate the recording medium about 5 times per track, whereas according to the present invention, the total of 2 times is required. Since the entire inspection process (including retry when multiple read heads are included) can be completed by rotation, quality inspection of the recording surface of the disk-type recording medium (retry when multiple read heads are used) It is possible to perform a more accurate inspection including the above) in a shorter time.

Further, an error signal indicating the presence or absence of a recording error is obtained by synchronizing the output signals of the respective inspection circuits corresponding to the respective read heads in accordance with the spacing between the heads and taking the logical product of the synchronized respective inspection circuit output signals. So that
Only when the same error is detected based on the read signals of at least two read heads, the error can be treated as a true error, and the inspection accuracy is improved.

[Brief description of drawings]

FIG. 1 is an electrical block diagram showing an embodiment of this invention. 1 ... write head, 2 ... read head, 3 ...
Rereading head, 4 ... Drive device, 5 ... Writing circuit, 6a, 6b ... Inspection circuit, 7a, 7b ... Amplifying circuit, 8a, 8
b …… Average level detection circuit, 9a, 9b …… Error detection circuit,
10 ... Error signal forming circuit, 11 ... Position synchronization circuit, 12 ...
… And circuit, 13 …… buffer memory, 14 …… CPU

Claims (2)

[Scope of utility model registration request] 1. A drive device for rotationally driving a disk-type recording medium to be inspected, and a drive device, which are arranged at predetermined intervals in a circumferential direction of the rotation, and are moved in a radial direction by a carriage. A writing head and at least two reading heads for writing or reading a signal on a recording surface of the disk-type recording medium, and writing for supplying a predetermined test signal to the writing head. Circuit, and an inspection circuit which is provided independently for each of the read heads, compares the level of the read signal from the corresponding read head with a reference level, and outputs a signal indicating the presence or absence of a recording error according to the comparison result. And the output signals of the inspection circuits corresponding to the read heads are synchronized in accordance with the distance between the heads, and the logic of the synchronized inspection circuit output signals is synchronized. And an error signal forming circuit that forms an error signal indicating the presence or absence of a recording error by taking the steps of: writing by the writing head and reading by the reading head with respect to the same or adjacent tracks on the disk type recording medium. A disk-type recording medium tester, which is characterized by being performed in parallel. 2. The inspection circuit includes an average level detection circuit for obtaining an average level of the levels of the read signals for one track, and a circuit immediately before the read signal for a certain track is output from the read head. A utility model registration claim including an error detection circuit that compares the read signal by using the average level obtained by the average level detection circuit for the track as the reference level and outputs a signal indicating the presence or absence of the recording error. 2. A disk type recording medium tester according to claim 1.