JPH0652586B2 - Optical disk inspection device - Google Patents

Description

The present invention relates to an optical disc inspection apparatus for inspecting an optical disc as an information recording medium, and more particularly to an optical disc inspection apparatus for inspecting an optical disc itself for defects.

[Prior Art] A conventional optical disc inspection apparatus reads a specific track of an optical disc, compares the read pattern with a test pattern written in advance on the specific track, and determines the quality of the optical disc from the error rate. It has become.

[Problems to be Solved] Such a conventional optical disc inspection apparatus has the following problems.

Since the writing pattern and the reading pattern are only collated until the user gets tired, it is not possible to detect a defect (adhesion of foreign matter, mixing, surface scratches, etc.) of the optical disc itself which causes an error. Naturally, the type of defect (bright defect, dark defect, etc.), position, size, etc. are unknown. In this way, we cannot get enough information to analyze the cause of defects,
The inspection results cannot be fully utilized for management of the optical disc manufacturing process.

Only a specific track on the optical disc can be inspected, and it is not possible to inspect any part including the track used by the user. Therefore, it may be determined that the optical disc cannot be used even if the user-used track of the optical disc is normal, and the determination result may not necessarily reflect the usability of the optical disc.

[Object of the Invention] The present invention has been made in view of the problems of such a conventional optical disc inspection apparatus, and an object of the present invention is to provide an optical disc inspection apparatus that can collect information about defects of the optical disc itself. Is.

[Means for Solving the Problems] In order to achieve this object, according to the present invention, an optical disc inspection apparatus illuminates a unit for rotationally driving an optical disc to be inspected and a read position portion of the optical disc. ,
An optical head for receiving the reflected light and photoelectrically converting the reflected light, a means for positioning the optical head at an arbitrary position of the optical disk, a means for generating position information regarding a reading position of the optical head, and A means for detecting a defect based on the level of the output signal of the optical head with respect to the recording position and storing defect information including the position information related to the detected defect in a memory.

[Operation] In the defective part of the optical disc, the reflectance is different from other parts,
Since the output signal level of the optical head changes, the optical disc inspection apparatus having the above-described configuration can detect defects in the optical disc itself. Further, it is possible to obtain defect information including at least information on the position of the defect, analyze the cause of the defect based on the defect information, and reflect it in management of the optical disc manufacturing process.

Since such a defect inspection can be performed at any position in the unrecorded position of the optical disc, it is possible to perform an inspection including the area used by the user, and the usability of the optical disc can be determined more reliably. it can.

Further, since it is not necessary to record the test pattern on a specific track of the optical disc, the user use area of the optical disc can be expanded accordingly.

[Embodiment] An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic block diagram of an optical disc inspection apparatus according to the present invention. In this figure, reference numeral 10 denotes an optical disk to be inspected, which is formatted but data is not written. However,
A test pattern may be recorded on a specific track of the optical disc 10 as in the conventional case. The optical disk 10 is rotationally driven at high speed by the drive mechanism 11. The drive mechanism 11 may be the same as that of a general optical disk drive device, and thus will not be described in detail.

Reference numeral 12 is an optical head for reading the optical disk 10,
The surface of the optical disk 10 is locally illuminated with laser light or the like, and the reflected light is received and converted into an electric signal. The optical head 12 may be the same as that used in a general optical disk drive. In addition, although an access control mechanism 13 for moving and positioning the optical head 12 in the radial direction of the optical disc 10 naturally exists,
Since it may be the same as the access control mechanism of a general optical disk drive, detailed description thereof will be omitted.

That is, the configuration of the portion that drives the optical disc 10 and optically reads the surface thereof may be the same as that of a general optical disc drive device.

Each circuit will be described below, and a timing diagram of signals related to each circuit is shown in FIG.

The optical head 12 outputs an analog signal (readout signal) a having a level proportional to the reflectance of the surface of the optical disc 10 at the reading position. The read signal a is amplified by the DC amplifier 14, and the amplified read signal b is input to the track / sector address read circuit 16 and the analog comparators 18 ₁ and 18 ₂ .

The track / sector address reading circuit 16 outputs an address signal d indicating an address (sector address and track address) peculiar to the sector to be read and a signal c generated at a position in the sector as shown in FIG. To be done. The signal c is input to the timing generation circuit 20, and the address signal d is input to the position information generation circuit 22.

The timing generation circuit 20 outputs a start pulse f, a clock CLK synchronized with this start pulse f, a set signal g, and a data field signal h. The cycle of the clock CLK corresponds to the 1-bit interval of the data on the optical disc 10. The data field signal h is a signal that is turned on during the reading period of the data field of the sector. In this embodiment, since the defect inspection is performed on the data field, the data field signal serves as a signal indicating the defect inspection range.

The position information generating circuit 22 includes a register 24 and a counter 26. The information of the address signal d output from the track / sector address reading circuit 16 is set in the register 24 at the rising edge of the set signal g.
The counter 26 counts the clock CLK after being reset by the start pulse f. This counter 2
The value of 6 is relative position information within the sector of the read position. This information and the information in the register 24 are combined and output as the position information signal m from the position information generating circuit 22.

The analog comparator 18 ₁ outputs the read signal b to the slice level L ₁ in order to detect a bright defect of the optical disc.
To compare with. The other analog comparator 1
8 ₂ is configured to compare the signal b and the read slice level L ₂ in order to detect the bright defect of the optical disk. The relationship between the slice levels L ₁ and L ₂ , the read signal b, and the output signals e ₁ and e ₂ of the comparators 18 ₁ and 18 ₂ is as shown in FIG.

The registers 28 ₁ and 28 ₂ include a host computer 52.
Further, digital data designating the slice levels L ₁ and L ₂ is set via the interface circuit 54. This digital data is converted into an analog voltage by the digital / analog converters 30 ₁ and 30 ₂ ,
The slice levels L ₁ and L ₂ are provided to the analog comparators 18 ₁ and 18 ₂ .

Here, the slice levels L ₁ and L ₂ are determined in consideration of, for example, a condition regarding a defect of an optical disk drive device used on the user side of the optical disk to be inspected.

Output signals e _{1 of} the analog comparators 18 ₁ and 18 ₂
e ₂ and the data field signal h from the timing generation circuit 20 are input to the defect discrimination circuit 32. From the defect discrimination circuit 32, a defect start point pulse i ₁ , a defect end point pulse i ₂ , a defect division signal i ₃ indicating whether the defect is a bright defect or a dark defect, a write timing pulse k,
And the memory address signal j is output.

The defect starting point pulse i ₁ is a pulse that rises at the time of rising of the signals e ₁ and e ₂ (starting point of a bright defect or a dark defect). The defect end point pulse i ₂ is a pulse which rises at the time when the signals e ₁ and e ₂ fall (the end point of a bright defect or the end point of a dark defect). The defect classification signal k is the signal e ₁
Is a signal which is set to the ON state at the rising edge (the start point of the bright defect) and is reset to the OFF state at the rising edge of the signal e ₂ .

A counter 34 for generating a memory address is provided in the defect discrimination circuit 32 and is incremented at the rising edge of the signals e ₁ and e ₂ . The contents of the counter 34 are sent out as a memory address signal j and input to the memory (2-port memory) 38 via the OR circuit 36. That is, the value of the memory address signal j is updated at the detection time of the start point and the end point of the defect. The write timing pulse k is generated when the memory address signal j is updated and its value is determined.

During the off-state period of the data field signal h, the counter 34 is held, the updating of the memory address signal j is prohibited, and the signals i ₁ , i ₂ , i ₃ and k are suppressed.

The memory 38 is for storing defect information. Position information signal m, defect start point pulse i ₁ , defect end point pulse i ₂
The defect classification signal i ₃ is input to the memory 38 as a defect information signal. The defect information collected in the memory 38 is finally read from the memory 38 and sent to the host computer 52. The memory address at that time is sent by the host computer 52 via the interface circuit 54 by the memory address signal n. It is specified.

It should be noted that there is a control unit for performing drive control of the optical disk, access control of the optical head 12, initial setting of each circuit, etc., but they are omitted in the figure.

Next, the operation of the optical disc inspection apparatus will be described with reference to the timing chart of FIG.

Actually, there are prepared a mode in which a specific track is designated and inspected only for it, and a mode in which all the tracks on the optical disc are inspected. The mode case will be described.

When the optical disc 10 to be inspected is set, the drive of the optical disc 10 is started and the optical head 12 is sequentially positioned from the first track to the last track under the control of a controller (not shown). Further, the register 24 and the counters 26 and 34 are reset. The memory 38 has been cleared.

During the reading period of each sector of each track, the track / sector address reading circuit 16 reads the track address and the sector address, and the track address and the sector address are read.
, And the signal c at the timing shown in FIG.
Is sent. In response to the signal c, the timing generation circuit 20 sends out a start pulse f, a clock CLK, a set signal g, and a data field signal h at the timing shown in FIG.

In the position information generating circuit 22, the counter 26 is reset by the start pulse f and then starts counting the clock CLK, and the information of the address signal d is set in the register 24 at the rising edge of the set signal g. Thus, the position information signal m is sent from the position information generating circuit 22 corresponding to the read position on the optical disk 10.

Here, it is assumed that a read signal a having a waveform as shown in FIG. 2 is obtained in the data field (data is not stored) of a certain sector. At the position of a bright defect (A in FIG. 2) such as a portion where a highly reflective foreign substance is attached in the data field, the read signal b exceeds the slice level L ₁ (slice level for bright defect detection). Defect start pulse i ₁ and defect end pulse i ₂
Are sequentially generated, and the defect classification signal i ₃ is turned on.

Similarly, at a dark defect position (B in FIG. 2) such as a portion where a foreign matter having a low reflectance is attached, the read signal b falls below the slice level L ₂ (dark defect detection slice level). The pulse i ₁ and the defect end point pulse i ₂ are sequentially generated, and the defect division signal i ₃ is turned off.

Since any of the defects is in the data field and the data field signal h of the timing generation circuit 20 is in the ON state, the discrimination circuit 34 is in the enabled state, and the defect starting point pulse i ₁ , at the timing shown in FIG. A defect end point pulse i ₂ , a defect division signal i ₃ , and a write timing pulse k are generated. Further, the counter 34 is updated with the start point and the end point of the defect as described above. Therefore, the position of the start point and the end point of each defect (which also indicates the size in the track direction as a result) and the type (classification of bright defect and dark defect) are written in the memory 38 as defect information in the order of detection.

As described above, according to this optical disc inspection apparatus, a defect of the optical disc itself, which cannot be inspected by the conventional collation of write data and read data, is detected with a 1-bit resolution, and the position of the defect is detected. It is possible to collect information on the size (known from the information of the start point position and the end point position) and the type (bright defect and dark defect). Moreover, it is possible to inspect an arbitrary portion or almost the entire area including the user use area of the optical disk without writing a test pattern on the optical disk. Further, since the inspection track in which the test pattern is written as in the conventional case is not required, the user's utilization area can be expanded correspondingly.

When the inspection is completed up to the last sector of the last track, the control unit (not shown) inhibits each circuit, stops the drive of the optical disk, and reports the end to the start host computer 52 of the interface circuit 54.

Upon receiving this report, the host computer 52 uses the memory 3
The defect information is read from No. 8 and the following processing is performed, for example.

First, the defect information is read from the memory 38 and temporarily stored in the internal memory. Next, the detected defects are classified according to size. Since the optical disk device has an error correcting function, it is possible to correct an error due to a minute defect.
Therefore, only defects having a size that causes an error that cannot be corrected by the error correction function are selected, and the number thereof is counted for each sector, for example. Then, based on the number of defects, a pass / fail judgment is made as to whether or not each sector can be used, and based on the result, it is judged whether or not the optical disk can be used.

It should be noted that the process described here is merely an example until the end of life. For example, the distribution of defects for controlling the manufacturing process of an optical disc,
Various kinds of processing relating to defects can be performed as necessary, such as processing for obtaining statistical data such as types, but the description thereof is omitted because it is not related to the gist of the present invention.

Moreover, since the inspection time becomes long when all the tracks of the optical disc are inspected, it is naturally possible to inspect a part of the optical disc as described above. In this case, for example, the inspection area is designated for each track and the address information of the track is set in the control unit in advance. The control unit controls the access of the optical head 12 according to the address information to sequentially read the target track, and the address signal d from the track / sector address reading circuit 16 is read.
Based on the above, the reading period of the target track is grasped and the operation of each circuit is controlled to detect the defect and record the defect information.

Since such control can be easily realized by a known technique, further description will be omitted.

Although one embodiment of the present invention has been described above, the present invention is not limited thereto and can be implemented by appropriately modifying the circuit configuration and the like.

For example, as a result, only one comparator for detection is provided,
The slice level may be set to a level for bright defects to inspect for bright defects, and then set to a slice level for dark defects to inspect for dark defects.

It is also possible to convert a read signal of the optical head into a digital signal and compare the signal with a slice level (digital signal) by a digital comparator to detect a defect.

As for the position information of the defect, only the position information of one of the starting point and the ending point of the defect may be stored.
However, since the size of the defect cannot be known from such position information, if size information is required, it is necessary to change the size information to be stored separately.

[Effects of the Invention] As described above, according to the present invention, the optical disc inspection apparatus illuminates the optical disc to be inspected, the reading position of the optical disc, and receives the reflected light. An optical head for performing photoelectric conversion, means for positioning the optical head at an arbitrary position on the optical disc, means for generating position information regarding the reading position of the optical head, and the optical head for the unrecorded position on the optical disc. The defect is detected based on the level of the output signal, and the defect information including the position information relating to the detected defect is stored in the memory. Obtain defect information including at least information on the position of the defect, analyze the cause of the defect based on it, and manage the manufacturing process of the optical disc. In addition to being able to reflect it, the defect inspection can be performed at any position in the unrecorded position of the optical disc, so that the inspection including the area used by the user is possible, and the usability judgment of the optical disc can be made more surely. Since the test pattern can be performed and it is not necessary to record the test pattern on a specific track of the optical disc, the user-use area of the optical disc can be expanded correspondingly.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an optical disc inspection apparatus according to the present invention, and FIG. 2 is a timing diagram for explaining the operation of the optical disc inspection apparatus. 10 ... Optical disk, 11 ... Drive mechanism, 12 ... Optical head, 13 ... Access control mechanism, 16 ... Track / sector address reading circuit, 18 ₁ , 18 ₂ ... Analog comparator, 20 ... Timing generation circuit , 22
...... Position information generation circuit, 28 ₁ , 28 ₂ ...... Register,
30 ₁ , 30 ₂ ... Digital / analog converter, 32 ...
… Defect discrimination circuit, 38… Memory.

Claims (5)

[Claims] 1. A means for rotatably driving an optical disk to be inspected, an optical head for illuminating a reading position portion of the optical disk, and receiving reflected light thereof for photoelectric conversion, and an optical head for the optical head. Means for positioning at a position, means for generating position information relating to the read position of the optical head, and detecting a defect based on the level of the output signal of the optical head with respect to the unrecorded position of the optical disc, and relating to the detected defect An optical disc inspection apparatus, comprising: means for storing defect information including the position information in a memory. 2. The defect detecting means includes at least one comparator for comparing a slice level with an output signal of the optical head, and the defect includes position information related to a level change point of the output signal of the comparator. The optical disc inspection apparatus according to claim 1, wherein the optical disc inspection apparatus is configured to store information in the memory. 3. The defect detecting means comprises a first comparator for comparing a slice level for detecting a bright defect and an output signal of the optical head, a slice level for detecting a dark defect and an output of the optical head. A second comparator that compares the signal with a signal, and is configured to store defect information including information on a position related to a level change point of the output signal of each comparator in the memory. The optical disk inspection device according to claim 1. 4. The defect information includes information indicating whether the level change point of the output signal of the comparator is a leading edge or a trailing edge, according to claim 2 or 3. Optical disc inspection device according to the item. 5. The defect information according to claim 3, wherein the defect information includes information indicating which of the output signals of the first and second comparators is the change point of the change point. The optical disk inspection device described.