JP3013413B2 - Defect inspection method of guide groove of optical disk - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection method for a guide groove of an optical disk for detecting, for example, a groove defect of an optical disk.

[Summary of the Invention]

The present invention relates to a defect inspection method for a guide groove of an optical disc for detecting, for example, a groove defect of an optical disc, and relates to a first detection signal detected at a first position of a track of the optical disc and a first detection signal of a track of the disc. By detecting a defect in the guide groove of the disk based on a difference from a second detection signal detected at a second position of the track of the disk offset from the position of the disk in the track direction of the disk, With a simple configuration without adding a new optical system element, without deteriorating the tracking servo margin, and simultaneously with other measurements such as certification (erasing, recording, and reproducing the entire surface of the disk), the guide groove is used. The defect inspection can be performed with high accuracy.

[Conventional technology]

In general, it is well known that a defect in a groove of an optical disc is caused by a defect of a stamper, a foreign matter on a substrate, a pinhole after film formation, and the like. The tracking servo becomes unstable because a zero-cross signal obtained when the light beam spot crosses the spot cannot be detected. For this reason, a defect inspection method for a groove of an optical disk has been conventionally proposed. First, the ninth
The tracking servo will be described with reference to FIG. 10 and FIG.

In FIG. 9, (1) is a laser diode, and the light beam emitted from the laser diode (1) is incident on a collimator lens (2) to be converted into parallel light, and then, for example, by a grating (3). The light beams are made into three light beams, and after passing through the beam splitter (4), the light beams enter the objective lens (5), and are focused on the optical disk (6) by the objective lens (5). These three light beams, that is, three reflected light beams,
As shown in FIG. 11, a first side beam light spot (19) and a main beam light spot (20) are formed on an optical disc (6) on which a groove (17) and a land (18) are formed, respectively.
And a second side beam light spot (21). Then, the reflected beam light from the optical disk (6) is again incident on the beam splitter (5) via the objective lens (5), is reflected on the interface a of the beam splitter (4), and is focused on the focusing lens (7). ), And is focused on the photodiode (8) by the focusing lens (7).

This photodiode (8) is, for example, as shown in FIG. 10, for example, PIN photodiodes (8e) and (8f)
A two-segment photodiode composed of a PIN photodiode (8g) and a two-segment photodiode composed of (8h), and a PIN photodiode (8a), (8b), (8
It is composed of a four-division photodiode composed of c) and (8d), and the three reflected light beams from the optical disk (6) are respectively incident thereon.

That is, as shown in FIG. 10, the reflected beam light corresponding to the spot (19) is incident on the two-division photodiodes (8e) and (8f), and the four-division photodiodes (8a) and (8
b), (8c) and (8d), the reflected beam light corresponding to the spot (20) is incident, and the two-part photodiode (8
The reflected beam light corresponding to the spot (21) is incident on g) and (8h).

First, the reflected beam light (diffraction beam light) corresponding to the spot (19) is received by the photodiodes (8e) and (8f), respectively, and the received reflected beam light is received by the photodiodes (8e) and (8e), respectively. The signal is photoelectrically converted at 8f) and output as detection signals E and F, respectively. And
These detection signals E and F are supplied to a subtracter (9), respectively, and subtraction, that is, an operation of (EF) is performed. On the other hand, reflected beam light (diffraction beam light) corresponding to spot (21)
Are received by the photodiodes (8g) and (8h), respectively, and the received reflected beam light is photoelectrically converted by the photodiodes (8g) and (8h), respectively, and output as detection signals G and H, respectively. Is done. Then, these detection signals G and H are supplied to a subtracter (10), respectively, and subtraction, that is, an operation of (GH) is performed. Then, the output signal (EF) of the subtractor (9) and the output signal (GH) of the subtractor (10) are supplied to an adder (11), respectively. The addition, that is, the operation of (EF) + (GH) is performed.

The reflected beam light (diffraction beam light) corresponding to the spot (20) is the photodiode (8a), (8b), (8c)
And (8d) received by the photodiodes (8a), (8b), and (8b), respectively.
The signals are photoelectrically converted in (8c) and (8d), and the detection signals A,
Output as B, C and D. And these detection signals
A, D and B, C are supplied to adders (13) and (14), respectively.
The addition, that is, the operations of (A + D) and (B + C) are performed, respectively. The output signals (A) of these adders (13) and (14)
+ D) and (B + C) are supplied to a subtractor (15), respectively.
Subtraction, that is, an operation of (A + D)-(B + C) is performed. Further, the output signal (A + D) −
(B + C) and the output signal (EF) of the adder (11) +
(GH) are supplied to the subtracters (12), respectively, and subtracted, that is, [(A + D)-(B + C)]-[(EF) + (G
-H)] is performed. The output signal [(A + D)-(B + C)]-[(EF) + (G-
H)] is supplied via an output terminal (16) as a tracking error signal (detection signal by push-pull) to a tracking servo system (not shown). As a result, it is possible to perform high-accuracy tracking servo in which offsets due to skew and disk eccentricity have been removed.

However, as shown in FIG. 11, when a defect (31) in which the groove (17) is partially missing occurs on the optical disk (6), the tracking error signal from the output terminal (16) becomes Despite the absence of the defective portion (31) of 17), it is almost zero. Therefore, from the tracking error signal, the defect (3
1) cannot be detected. Also, if there is such a missing portion of the groove (17), the optical disc will be of low quality such that a so-called track jump cannot be performed.

For this reason, as shown in FIG. 12, there has been proposed a method of inspecting a groove of an optical disk for defects by a so-called detrack method. This detracking method is performed, for example, so that the center of the beam emitted from the laser diode (1) passes through a position O 'deviated from the center O of the land (18) of the optical disk (6) as shown in FIG. 12A. It was done. This state is called off-track, and tracking is performed with this off-track. Therefore, as shown in FIG. 12B, when tracking is performed so that the center of the light beam emitted from the laser diode (1) passes through the center O of the land (18), the optical disk as shown in FIG. Regardless of the presence or absence of the defect (31) in the groove (17) of (6), the tracking error signal TP is always substantially 0, and the defect (31) of the groove (17) cannot be detected.

However, as shown in FIG. 12B, when tracking is performed such that the center of the light beam emitted from the laser diode (1) passes through a position O ′ shifted from the center O of the land (18), the twelfth is performed. Optical disk (6) as shown in FIG.
The tracking error signal TP 'is always higher than the threshold level in the portion of the groove (17) having no defect (31). Then, in a portion where the groove (17) of the optical disc (6) has a defective portion (31) as shown in FIG. A, the tracking error signal TP 'becomes substantially zero. Therefore, the defective portion (31) of the groove (17) of the optical disk (6)
Can be detected. In the method of inspecting a groove of an optical disk for defects by a method called a detrack method, a beam emitted from the laser diode (1) passes through a position shifted from the center O of the land (18), for example. By doing so, a level difference is generated in the tracking error signal between the portion having the defective portion (31) in the groove (17) and the portion not having the defective portion (31), and the defective portion (31) of the groove (17) is detected. I was

[Problems to be Solved by the Invention] By the way, in an optical disk, erasing, reproduction, recording, and the like (generally called certification) are performed as a quality inspection. This certification is performed in the state of just tracking. Therefore,
Inspection for detecting a groove defect by the above-described detrack method and this certification cannot be performed at the same time, and are performed separately. Therefore, if the defect inspection of the groove by the detrack method is performed, it takes too much time for measurement. There is.

In the groove defect inspection by the detrack method described above, tracking is performed in an off-track state.
There is a disadvantage that the margin is reduced.

The present invention has been made in view of the above point, and has a simple configuration without deteriorating a tracking servo margin, and performing other measurements such as certification (erasing, recording, and reproducing the entire surface of a disk). At the same time, it is an object of the present invention to propose a guide groove defect inspection method for an optical disc which can accurately perform a guide groove defect inspection.

[Means for solving the problem]

As shown in FIG. 1 to FIG. 8, for example, as shown in FIGS. 1 to 8, the guide groove defect inspection system of the present invention employs a first detection signal detected at a first position of a track of an optical disk (6) and a first detection signal. The optical disc (6) is offset from the first position of the track (6) in the track circumferential direction of the optical disc (6) by a difference from a second detection signal detected at a second position of the track of the optical disc (6). The defect (31) of the guide groove (17) of (6) is detected.

Further, the defect inspection method of the guide groove of the optical disk of the present invention uses the first detection signal detected at the first position of the track of the optical disk (6) and the first position of the track of the optical disk (6). A defect (31) in the guide groove (17) of the optical disc is caused by a difference from a second detection signal detected at a second position of the track of the optical disc (6) offset in the track radial direction of the optical disc (6). Is detected.

In the defect inspection method of the guide groove of the optical disc of the present invention, the optical disc (6) is irradiated with three light beams (19), (20), and (21) to irradiate the first position of the track of the optical disc (6). The optical disc (6) is obtained from a first detection signal detected by the optical disc and a first position of a track of the optical disc.
Optical disc (6) offset in the track radius direction
And a first tracking error signal detected at a second position of the track of the optical disc (6), and a first tracking error signal of the track of the optical disc (6) offset from the second position of the track of the optical disc in the track radial direction of the optical disc (6). 3 and a second tracking error signal and a groove defect signal obtained by calculating the first detection signal and the second detection signal, and the first detection signal and the second defect signal. A tracking error signal is output at the same time.

[Action]

According to the present invention described above, the first detection signal detected at the first position of the track of the optical disk (6) and the first position of the track of the disk (6) are used to determine the position of the disk (6). A defect in the guide groove (17) of the disk (6) is detected based on a difference from a second detection signal detected at a second position of the track of the disk (6) offset in the track direction. With a simple configuration, it is possible to accurately inspect the guide groove for defects without deteriorating the tracking servo margin and at the same time as performing other measurements such as certifying (erasing, recording, and reproducing the entire surface of the disk).

〔Example〕

Hereinafter, the defect inspection method of the guide groove of the optical disk of the present invention will be described in detail with reference to FIG. In FIG. 1, portions corresponding to those in FIG. 9 are denoted by the same reference numerals, and description thereof will be omitted.

In FIG. 1, a light beam emitted from a laser diode (1) is incident on a collimator lens (2) and is formed into parallel light, which is then converted into, for example, three light beams by a grating (3). Light enters the objective lens (5) via the beam splitter (4), and is focused on the optical disk (6) by the objective lens (5). As shown in FIG. 3, these three light beams are incident on an optical disk (6) and are positioned at the center of a land (18) or a groove (17).

These three light beams again enter the beam splitter (4) via the objective lens (5), are reflected at the interface a of the beam splitter (4), and are respectively focused on the photodiode (8) by the focusing lens (7). ).

This photodiode (8) is, for example, as shown in FIG. 2, a two-segment photodiode composed of, for example, PIN photodiodes (8e) and (8f), and a two-part photodiode composed of PIN photodiodes (8g) and (8h). Split photodiode, PIN photodiode (8a), (8b), (8c)
And (8d).

As shown in FIG. 2, a two-part photodiode (8
The reflected beam light (side beam light) corresponding to the spot (19) (see FIG. 3) is incident on e) and (8f), and the photodiodes (8a), (8b), (8c) and (8d) The reflected beam light (main beam light) corresponding to the spot (20) (see FIG. 3) is incident on the spot (20), and the spot (21) (see FIG. 3) is incident on the split photodiodes (8g) and (8h). Corresponding reflected beam light (side beam light) is incident.

First, the reflected beam light (diffraction beam light) corresponding to the spot (19) is received by the photodiodes (8e) and (8f), respectively, and the received reflected beam light is received by the photodiodes (8e) and (8e), respectively. The signal is photoelectrically converted at 8f) and output as detection signals E and F, respectively. At the same time, the reflected beam light (diffraction beam light) corresponding to the spot (21) is received by the photodiodes (8g) and (8h), respectively, and the received reflected beam light is received by the photodiodes (8g) and (8g), respectively. 8h), the signals are photoelectrically converted and output as detection signals G and H, respectively. Then, the detection signal G from the photodiode (8g) and the detection signal F from the photodiode (8f) are supplied to the subtractor (32), respectively, and are subtracted by this subtractor (32), that is, (G-F ) Is performed. On the other hand, the detection signal E from the photodiode (8e) and the detection signal H from the photodiode (8h)
Are supplied to the subtractor (33), and the subtractor (33) performs the subtraction, that is, the operation of (E−H). Further, the output signal (G-F) from the subtractor (32) and the output signal (E-H) from the subtractor (33) are supplied to an adder (34), respectively. (G-F) + (E-
H) is performed, and the output signal (G
−F) + (E−H) is supplied to a tracking servo system circuit (not shown) via the second tracking error signal output terminal (36). At the same time, the output signal (E−H) from the subtractor (33) and the output signal (G−F) from the subtractor (32) are supplied to the subtractor (35), respectively. The operation of (E−H) − (G−F) is performed,
The output signal (EH)-(GF) of the subtracter (35) is supplied to a groove defect detection signal output terminal (37) as a groove defect detection signal.

The reflected beam light (diffraction beam light) corresponding to the spot (20) is the photodiode (8a), (8b), (8c)
And (8d) are received respectively, and the received reflected beam light is received by the photodiodes (8a), (8b),
The signals are photoelectrically converted in (8c) and (8d), and the detection signals A,
Output as B, C and D. Then, the detection signals A and D from the photodiodes (8a) and (8d) are supplied to the adder (13), respectively, and are added, that is, the operation of (A + D) is performed. On the other hand, the detection signals B and C from the photodiodes (8b) and (8c) are supplied to the adder (14), respectively, and are added, that is, the operation of (B + C) is performed. And furthermore
The output signal (A + D) from the adder (13) and the adder (1
The output signal (B + C) from 4) is supplied to the subtracter (15), respectively, and subtraction, that is, the operation of (A + D)-(B + C) is performed. Output signal (A + D) from the subtracter (15)
− (B + C) is supplied to a tracking servo system circuit (not shown) via a first tracking error signal output terminal (38). The first tracking error signal (G−F) + (E−H) and the second tracking error signal (A + D) − (B + C) are individually calculated or further processed to form one tracking error signal. As a signal for tracking servo.

As shown in FIG. 3, for example, when there is a defective portion (31) in which the groove of the optical disk (6) is missing, the output signal (GF) from the subtracter (32) (see FIG. 2). As shown in FIG. 4A, there occurs a portion exceeding the negative threshold level, and the output signal (EH) from the subtracter (33) (see FIG. 2) is generated as shown in FIG. 4B. , A portion exceeding the positive threshold level occurs.

Therefore, these output signals (E−H) and (G−F)
Is a subtractor (35) (see FIG. 2), and (E−H) − (G−
When the calculation of F) is performed, the detection sensitivity of the groove defect detection signal output as a result is improved. Thus, each photodiode (8e) and (8f), (8
g) and (8h), (8a), (8b), (8c) and (8d) output signals E and F, G and F, A, B, C and D, respectively, as tracking error signals (G −F) + (E−H),
(A + D)-(B + C), and (EH)-(GF) as the groove defect detection signal, so that the tracking error signal and the groove defect detection signal can be output at the same time. The defect inspection of the groove (17) can be performed with high accuracy without deteriorating the servo margin and at the same time as other measurements such as certify (erasing or recording / reproducing the entire surface of the disk).

In the above-described example, three light beams are incident on different tracks of the optical disk (6) or over different tracks. However, as shown in FIG. 5, the two light beams are spaced on the same track. A photodetector may be provided in correspondence with these two spots (22) and (23) so as to be incident at an interval, and a groove defect detection signal may be obtained by taking the difference between these photodetectors. Also, as shown in FIG. 6, two light beams are respectively incident on different tracks of the optical disk (6) so as to be arranged in the radial direction of the optical disk (6), so that these two spots (24) and A photodetector may be provided corresponding to (25), and a groove defect detection signal may be obtained by taking the difference between the outputs of these photodetectors.

FIG. 7 shows another example of the guide groove defect inspection system of the optical disc of the present invention.

In FIG. 7, (26a) and (26b) are, for example, PIN photodiodes, respectively, and these PIN photodiodes (26a) and (26b) constitute a two-division photodiode. One PIN that constitutes this two-segment photodiode
An output terminal of the photodiode (26a) is connected to a non-inverting input terminal of a subtractor (28) via a delay line (27) for delaying a signal by τ time, and the other PIN photodiode constituting the two-division photodiode is connected. The output terminal of (26b) is connected to the inverting input terminal of the subtracter (28). Then, the reflected beam light (diffraction beam light) corresponding to the spot (30) as shown in FIG.
a) and (26b) respectively.

In the above-described configuration, when there is a defective portion (31) in the groove (17) of the optical disk (6) as shown in FIG. 8, the defective portion (31) is normally subtracted as shown in the figure. However, the detection signal from the photodiode (26a) detected at a certain position of the spot (30) is delayed by τ time by the delay line (27). During this time, the spot (30) moves to the position indicated by the two-dot chain line in the figure. At this time, the subtracter (28) applies the spot (3) indicated by the solid line in the figure.
The detection signal of the photodiode (26a) at the position (0) is supplied, and the spot (30) indicated by the two-dot chain line in the figure is supplied.
The detection signal of the photodiode (26b) at the position is supplied. Therefore, when the spot (30) reaches the position indicated by the two-dot chain line in the drawing, that is, the defect (31), a groove defect detection signal that has detected this defect from the subtractor (28) is output to the output terminal (29). ).

Therefore, as is clear from the above-described examples, the position of the spot on the optical disk is changed spatially or temporally in the track direction, and the reflected light beam corresponding to the spot at the different spatial or temporal position is detected by the light receiving element. With this configuration, the defect of the groove (17) can be reliably detected with the simplest configuration.

It is to be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

〔The invention's effect〕

According to the present invention described above, the first detection signal detected at the first position of the track of the optical disk and the first detection signal of the track of the disk offset from the first position of the track of the disk in the track direction of the disk. Since the defect of the guide groove of the disk is detected based on the difference from the second detection signal detected at the second position, a simple configuration can be used without deteriorating the tracking servo margin and, for example, There is an advantage that the defect inspection of the guide groove can be performed with high accuracy simultaneously with other measurements such as certification (erasing, recording, and reproducing the entire surface of the disk).

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of an optical system for explaining a defect inspection method of a guide groove of the optical disk of the present invention. FIG. 2 is a configuration diagram showing an example of a defect inspection method of a guide groove of the optical disk of the present invention. FIG. 3 is a diagram for explaining an example of a defect inspection method of a guide groove of the optical disk of the present invention, FIG. 4 is a diagram for explaining an example of a defect inspection method of a guide groove of the optical disk of the present invention, and FIG. FIG. 6 is a diagram for explaining an example of a defect inspection method for a guide groove of the optical disk of the present invention, FIG. 6 is a diagram for explaining an example of a defect inspection method for a guide groove of the optical disk of the present invention, and FIG. FIG. 8 is a configuration diagram showing another example of the groove defect inspection system, FIG. 8 is a diagram for explaining another example of the guide groove defect inspection system of the optical disk of the present invention, and FIG. Configuration diagram of an optical system for explaining a defect inspection method, 10 illustration diagram showing a circuit configuration example for explaining a defect inspection method of the guide groove of the conventional optical disk,
FIG. 11 is a diagram for explaining a conventional defect inspection method for a guide groove of an optical disk, and FIG. 12 is a diagram for explaining a conventional defect inspection method for a guide groove of an optical disk. (6) is an optical disk, (8) is a photodiode, (1)
7) It is a groove.

Claims (4)

(57) [Claims] 1. A first detection signal detected at a first position of a track of an optical disk, and a first detection signal of a track of the optical disk that is offset from the first position of the track of the optical disk in a track circumferential direction of the optical disk. 2. A defect inspection method for a guide groove of an optical disc, wherein a defect of the guide groove of the optical disc is detected based on a difference from a second detection signal detected at the position No. 2. 2. The method according to claim 1, wherein said second detection signal is a detection signal obtained by delaying one of detection signals detected by a two-division photodiode. 2. A defect inspection method for a guide groove of an optical disk, wherein the detection signal of No. 1 is the other detection signal of the two-divided photodiode. 3. A first detection signal detected at a first position of a track of an optical disk, and a second detection signal of a track of the optical disk offset from the first position of the track of the optical disk in a track radial direction of the optical disk. A defect in a guide groove of the optical disk, wherein the defect is detected based on a difference from a second detection signal detected at the position. 4. An optical disc is irradiated with three light beams,
A first position detected at a first position of a track on the optical disc;
, A first tracking error signal detected at a second position of the track of the optical disc offset from the first position of the track of the optical disc in the track radial direction of the optical disc, and Obtaining a second detection signal detected at a third position on a track of the optical disk offset from the second position in the track radial direction of the optical disk, and calculating the first detection signal and the second detection signal A second tracking error signal, a groove defect signal, and the first tracking error signal obtained at the same time, which are simultaneously output.