JP2008111830A - Method and device for detecting peripheral surface defect of disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for detecting a peripheral surface of a disk capable of detecting highly accurately an outer peripheral defect such as a chuck impression, a flaw or a chip remaining when chucking a disk substrate, almost without detecting foreign matter which is one of defects. <P>SOLUTION: Regularly reflected light of light incident at an angle in the range of 45°±5° with respect to the surface of a chamfer part is received by a photodetector through a diaphragm, and thereby decline of a level of a light receiving signal of foreign matter generating much scattered light is suppressed small, similarly to a noise, and a level of a light receiving signal of a flaw or the like caused by the chuck impression is lowered greatly, to thereby enlarge a level difference between each detection signal of the foreign matter and the flaw. Then, fluctuation of a signal reference level of the light receiving signal caused by deflection in the vertical direction of a disk outer circumferential surface generated by rotation of the disk is suppressed, or the fluctuation is canceled. Hereby, a detection signal of the outer peripheral defect having a greatly reduced level in the light receiving signal can be acquired easily. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a disk peripheral surface defect detection method and detection device, and more specifically, such as chuck marks, wrinkles and chippings remaining when a disk substrate is chucked with almost no foreign matter adhering as one of the defects. The present invention relates to a disk peripheral surface defect detection method and a detection apparatus that can detect peripheral defects with high accuracy.

  Conventionally, magnetic disks, which are one of information recording media such as computers, have been made of aluminum disks. However, in recent years, glass disks have been made of materials to meet the demand for smaller and higher recording density, and a magnetic film is formed on the disk. Yes. The glass disk is smoothened by polishing the surface, but the inner peripheral edge or the outer peripheral edge may be chipped or broken during polishing work or handling. As a result, the quality of the disk deteriorates, so that in the surface inspection process, chipping, cracking, etc. are inspected, and if the degree is small, it is re-polished, and if this is large, the disk is considered defective. The degree of the chipping and cracking is inspected and determined by a defect inspection apparatus.

With reference to FIG. 6, the outer peripheral edge portion of the glass disk and its chip defect will be described.
6A, the glass disk 1 has various outer diameters, and each has a center hole H having a predetermined diameter. (B) shows a cross section of the outer peripheral portion, where the upper surface is 1a, the lower surface (back surface) is 1b, and the outer side surface is 1c. The disk 1 is formed with an upper peripheral edge (hereinafter referred to as a chamfer) ChU and a lower chamfer ChD chamfered in the vicinity of the side surface 1c. The chip or crack generated here is the peripheral defect K. The length d differs depending on the size of the disk 1, and is, for example, 0.2 mm in the case of 2.5 inches.

Hard disk devices (HDD) are now widely used in the fields of automobile products, home appliances, and acoustic products, and hard disk drive devices of 3.5 inches to 1.8 inches and even 1.0 inches or less are various products. Built and used. Moreover, due to the high recording density magnetic head and the improved head positioning accuracy, recently, in addition to the glass disk substrate (glass substrate), an inexpensive aluminum disk substrate (aluminum substrate) is often used. These boards are used properly.
As a conventional method for detecting defects at the outer peripheral edge of a magnetic disk using a glass substrate, the scattered light is received by projecting light onto the chamfered portion at an incident angle of about 30 ° as viewed from the normal line above the outer peripheral edge portion E. An invention by the applicant that has a first light receiving system and a second light receiving system for receiving scattered light in a direction opposite to the outer peripheral side surface of the disk in addition to this is known (Patent Document 1).
Furthermore, although it is not a peripheral surface defect detection device, the disk surface is irradiated with linear light from the upper part of the transparent disk, and this is totally reflected inside the disk to receive the scattered light from the outer peripheral side surface. A defect detection apparatus for detecting defects on the surface is known (Patent Document 2).
Japanese Patent Application Laid-Open No. 7-190950 JP-A-64-57154

In the case of a high recording density HDD using an aluminum substrate or an aluminum magnetic disk (hereinafter referred to as an aluminum disk) using the aluminum substrate as a substrate, the width of the outer peripheral edge E of the disk or the width of the chamfer is currently The track is formed as narrow as 0.15 mm or less, and to the limit of the outer edge portion E. The thickness of the disk is about 0.5 mm to 1.3 mm depending on the outer diameter, the angle of the chamfer is inclined about 45 ° ± 5 °, and the width of the side surface 1c is also narrowed.
Such an aluminum disk has a softer surface than a glass disk, and tends to have a chuck mark during disk handling.

Since the disk chuck is usually performed at the edges (chamfer part and side surface) provided on the outer periphery of the disk, the chamfer part is likely to have a chuck flaw. The chuck mark of the aluminum disk is shallower than the wrinkles and chips of the glass disk substrate, and has a size of about 100 μm. Since the aluminum disk is an opaque material, transmission type detection cannot be performed.
Such a chuck mark smaller than the conventional scissors has a low detection signal level even if the defect detection is performed by the conventional defect detection method of the outer peripheral edge of the glass disk as shown in Patent Document 1, and the foreign matter adhered to the chamfer. There is a drawback that it is difficult to distinguish between and chuck chucks.
Adhered foreign matter (hereinafter referred to as foreign matter) can be removed by cleaning, but a disc with a chuck mark that causes a problem is defective or is polished and removed in some cases.
On the other hand, the glass disk is often chipped without becoming a chuck mark, and there are some that are relatively small. Even in such a case, when the defect is detected, the level of the detection signal is low, and it is difficult to distinguish between the foreign matter adhering to the chamfer and the chuck.

One reason why it is not possible to distinguish between a foreign object and a chuck rod is the vertical deflection of the outer peripheral surface of the disc due to the disc runout caused by the rotation of the disc to be inspected.
That is, since the disc to be inspected is inserted into the spindle and subjected to a defect inspection in a rotating state, the vertical runout of the outer peripheral surface of the disc at the time of detecting a defect becomes large due to the disc runout. Therefore, there is a problem that the reference level of the wrinkle detection signal due to the chuck mark fluctuates due to the shake of the disk, and the wrinkle detection signal due to the chuck mark and the detection signal of foreign matter cannot be clearly separated. Detecting a foreign object as a flaw or a defect deteriorates the yield of the disk.
An object of the present invention is to solve such a problem of the prior art, and the chuck mark, wrinkles and chipping remaining when the disk substrate is chucked without almost detecting a foreign matter which is one of the defects. It is an object of the present invention to provide a disk peripheral surface defect detection method capable of detecting peripheral defects such as those with high accuracy.
Another object of the present invention is to provide a disk peripheral surface defect detection apparatus capable of detecting a defect on the outer peripheral surface with high accuracy without detecting foreign matter.

  In order to achieve such an object, the peripheral surface defect detecting method or peripheral surface defect detecting apparatus of the present invention has a configuration of 45 ° ± 5 ° with respect to the surface of the outer peripheral chamfer portion of the rotating disk. A light beam is irradiated onto the outer chamfer part at a certain incident angle, and a regular reflection light from the outer chamfer part is received through a diaphragm with a light receiver provided at a predetermined distance from the outer chamfer part to obtain a received light signal. The detection signal of the defect on the outer peripheral surface is obtained by suppressing or canceling the fluctuation of the signal reference level of the received light signal due to the fluctuation of the outer peripheral surface of the disk caused by the rotation of the disk.

As described above, according to the present invention, the specularly reflected light incident at an incident angle in the range of 45 ° ± 5 ° with respect to the surface of the chamfer portion is received by the light receiver through the diaphragm, so that the scattered light is received. Reduce the level of the received light signal of foreign objects to a small level, make it close to noise, greatly reduce the level of received light signals such as wrinkles due to chuck marks, and increase the level difference between the foreign object and wrinkle detection signals To do. After that, the fluctuation of the signal reference level of the received light signal due to the vertical fluctuation of the outer circumferential surface of the disk caused by the rotation of the disk is suppressed or the fluctuation is canceled.
Thereby, it is possible to easily obtain the detection signal of the peripheral defect whose level is greatly lowered in the light reception signal.
In order to suppress or cancel the fluctuation of the signal reference level of the received light signal, a reference level fluctuation suppressing circuit can be provided. As an example of the circuit, a circuit that extracts a signal corresponding to a change in the signal reference level as a detection reference signal from a light reception signal through a low-pass filter or a bandpass filter, and compares the detection reference signal with the light reception signal. be able to. As another example, a circuit that removes a fluctuation component of the signal reference level of the received light signal by passing through a high-pass filter and extracts a defect detection signal from the received light signal can be cited.
Such a light receiving signal reference level fluctuation suppressing circuit can detect defects on the outer peripheral chamfered portion including defects due to chuck marks from foreign objects and hardly detect foreign objects.
As a result, in the peripheral surface defect detection apparatus to which the present invention is applied, defects such as wrinkles and chips caused by chuck marks or the like in the outer peripheral chamfer portion of the disk can be separated from foreign matters and detected efficiently and with high accuracy. .

FIG. 1 is an explanatory view of an embodiment of an aluminum disk peripheral surface defect detection apparatus to which the disk peripheral surface defect detection method of the present invention is applied, and FIG. 2 (a) is a case where foreign matter adheres to the chamfer portion of the disk. FIG. 2B is an explanatory diagram in the case where there is a flaw due to a chuck mark or the like in the chamfer portion of the disk, FIG. 3 is an explanatory diagram of a detection signal for one track, and FIG. FIG. 4B is an explanatory diagram of a signal waveform obtained by filtering the detection signal of the photoreceiver, FIG. 4B is an explanatory diagram of a defect detection signal that has passed through the reference level fluctuation suppression circuit, and FIG. 5 is a reference level fluctuation suppression of another received light signal. It is a block diagram of a defect detection circuit using a circuit.
In FIG. 1, reference numeral 10 denotes a defect inspection apparatus, which includes a spindle 2, a defect detection optical system 3, a defect detection circuit 5, a data processing device 6, and a disk reversing mechanism 8.
The defect detection optical system 3 includes a light projecting system 3 a and a light receiving system 4.
The spindle 2 rotates with an aluminum disk (hereinafter referred to as disk) 1 to be inspected. The light projecting system 3a irradiates the inspection area Q on the outer peripheral surface of the disc with a laser spot Sp from the light source (laser light source) 31 at an incident angle θi≈45 ° with respect to the outer peripheral chamfer 1d on the surface 1a side of the disc 1. .

The light receiving system 4 includes an imaging lens 41, an aperture plate 42, and a light receiver 43. The aperture plate 42 is provided in front of the light receiver 43.
The light receiver 43 is an avalanche photodiode (APD), and is disposed at an upper part at a predetermined distance from the outer peripheral chamfered portion 1d in a direction perpendicular to the surface 1a of the disk 1, and an imaging lens 41, The regular reflection light from the inspection region Q is received through the aperture plate 42.
The incident angle θi is in the range of 45 ° ± 5 ° with respect to the normal line standing on the surface of the outer peripheral chamfer 1d on the surface side. The aperture plate 42 has an aperture 42a having a size that allows only regular reflection light from the chamfer portion 1d to pass therethrough. The hole diameter can be adjusted. Although the diameter of the laser spot Sp is larger than the thickness of the disk 1, the light receiver 43 is positioned above the outer peripheral chamfer portion 1d in a direction perpendicular to the surface 1a of the disk 1 and the presence of the aperture hole 42a. Only the regular reflection light from the part 1d can be received.

In FIG. 1, reference numeral 5 denotes a defect detection circuit, which includes a preamplifier (AMP) 51, an LPF (low pass filter) 52, an HPF (high pass filter) 53, a comparison amplifier (COM) 54, and an A / D 55. The output of D55 is sent to the data processing device 6, and the data processing device 6 detects the number and size of defects in the chamfer portion 1d of the disk 1.
Here, the LPF 52 is a circuit for extracting a reference signal of a received light signal generated due to the vertical fluctuation of the outer peripheral surface of the disc. The HPF 53 is inserted between the output terminal of the LPF 52 and the ground GND to generate a high frequency noise component. And a circuit for dropping detection signal components such as wrinkles and foreign matters to the ground GND. The comparison amplifier (COM) 54 is a circuit that cancels the fluctuation of the reference level of the received light signal caused by the vertical fluctuation of the outer peripheral surface of the disk and generates a detection signal of the outer peripheral defect.

The detection signal of the light receiver 43 is input to the (+) input of the comparison amplifier 54 through the preamplifier 51, the LPF (low pass filter) 52, and the HPF (high pass filter) 53 of the defect detection circuit 5. The (−) input of the comparison amplifier 54 receives the output of the preamplifier 51.
The data processing device 6 includes an MPU 61, a memory 62, a display 63, a keyboard 64, an interface circuit (I / F) 65, and the like, which are connected to each other via a bus 66. Reference numeral 67 denotes an external storage device such as an HDD.
The memory 62 is provided with a defect detection program 62a, a defect size determination program 62b, a disk pass / fail determination program 62c, and a work area 62d.
The MPU 61 receives an index signal IND obtained from the encoder 2a provided on the spindle 2 side corresponding to one rotation of the disk as an interrupt signal via the bus 66.
A disk reversing mechanism 8 is provided adjacent to the disk 1 mounted on the spindle 2. This disk reversing mechanism 8 chucks the outer peripheral side surface of the disk 1 with a chuck mechanism and lifts the disk 1 from the spindle 2 to receive it. Then, the disk 1 is retracted from the position of the spindle 2 by retreating on the rail (not shown), and the front side outer peripheral chamfer 1d reverses the inspected disk 1 and advances on the rail with the back side as the surface. Then, the disk 1 is returned to the top of the spindle 2 and remounted on the spindle 2. Since various types of disk reversing mechanisms are known, details are omitted.

2A and 2B are explanatory diagrams for detection of an outer peripheral defect of the defect detection optical system. FIG. 2A is an explanatory diagram when a foreign substance adheres to the chamfer portion 1d of the disk 1, and FIG. FIG. 5 is an explanatory diagram when a chamfer F due to a chuck mark or the like is present on the chamfer portion 1d of the disk 1; In these drawings, the diaphragm 42 is omitted for convenience of explanation.
As shown in FIG. 2A, when there is a foreign substance in the chamfer part, the foreign substance generates a lot of forward / backward scattered light and the regular reflection light is reduced. Each waveform as indicated by points P1, P2, and P3 in FIG. 3 appears in the received light signal (detection signal S).
When the chamfered portion 1d of the disk 1 has wrinkles F due to chuck marks or the like, as shown in FIG. 2 (b), the specular reflection light is greatly reduced, so that the light reception signal of the light receiver 43 is lowered. A pulse-like waveform as indicated by the point KF is obtained as a detection signal of 疵 F. On the other hand, the detection signals (hereinafter referred to as the detection signal at point P1, the detection signal at point P2, and the detection signal at point P3) of the waveforms indicated by points P1, P2, and P3 corresponding to the foreign matter are respectively at point KF. The level decrease of the received light signal is smaller than the detection signal having the waveform shown (hereinafter, the detection signal at the point KF).
However, when the detection signal at the point KF is at the peak position of the detection signal S due to the change in the reference level of the received light signal, or when the level drop is small, or conversely, the detection signal at the point P3 of the pulse waveform is When the level is good or large, it may be difficult to distinguish.

Therefore, the detection signal S is passed through an LPF (low-pass filter) 52 and an HPF (high-pass filter) 53, and the LPF 52 passes a signal component corresponding to the vibration of the disk 1, and the remaining high-frequency noise and points P1, P2, P3, Each detection signal component of KF is dropped to the ground by the HPF 53, and as a result, the detection of the vibration waveform corresponding to the vibration of the disk 1 having almost no noise as shown in FIG. Extract the reference signal.
By adding this vibration waveform to the (+) input of the comparison amplifier (COM) 54, the fluctuation of the reference signal level of the received light signal on the (−) input side is canceled.
Since the detection signal S is not a perfect sine wave, it is necessary to pass these filters. However, the rotation speed of the spindle is, for example, 10,000 rotations, and the cutoff frequency of the LPF 52 is, for example, 200 Hz, 2.5. If the signal component corresponding to the vertical deflection of the outer peripheral surface of the inch disk is allowed to pass, both can be used even in the case of 1.8 inches.
The LPF 52 extracts signal components corresponding to the frequency of the signal component corresponding to the vertical vibration of the outer peripheral surface of each disk at one or more diameters in the detection signal S, depending on the number of rotations of the spindle. BPF (band-pass filter) can be used. Therefore, the LPF 52 may be a BPF.

Therefore, as a result of comparing the signal of FIG. 4 (a) with the detection signal S of FIG. 3 (a) by the comparison amplifier 53, the points P1, P2, P3 and the point KF at which the comparison amplifier 53 is reduced to a pulse signal are obtained. A defect detection signal Sk as shown in FIG. 4B can be obtained at the position of each detection signal.
In this way, not only is the change in the reference level of the received light signal canceled, but the detection signal corresponding to the foreign matter indicated by the detection signals at points P1 and P2 has a small level drop and is noisy. Therefore, most of them do not appear at the output of the comparison amplifier 54, as indicated by the dotted line in FIG.
Since the comparison amplifier 54 is a high gain non-inverting DC amplifier, there is a possibility that the high frequency noise of the input signal of the (−) input may be amplified, but this is somewhat removed in the operation dead band of the non-inverting DC amplifier, Further, although not shown in the drawing, it is removed by dropping to the ground GND with a capacitor or the like. As a result, the detection signals at the points P1 and P2 close to the high frequency noise are removed.
As a result, the defect detection signal Sk can be obtained by using the detection signal as shown in FIG. Here, the detection signals for many foreign substances are dropped. Of course, no high frequency noise is output at this time.

As a result, what is detected has a relatively low level corresponding to the foreign matter, and if so, a pulse-like detection signal at point P3 and a detection signal at point KF corresponding to 疵 F having a large reduction level. become. Each of the detection signals at point P3 and point KF appears at the output of the comparison amplifier 54 as a pulse signal having a level corresponding to the difference in the attenuation level of the received light. In addition, the detection signal of the pulse point P3 is rarely generated.
The A / D 55 receives the pulse signals corresponding to the detection signals at the points P3 and KF as the defect detection signal Sk. The level of this signal is converted into a digital value every time the defect detection signal Sk is generated and sequentially stored in the work area 62d.

The data processing device 6 receives the index signal IND and calls the defect detection program 62a when the inspection of the chamfer for one round of the disk 1 is completed. The defect detection program 62a is executed by the MPU 61. The MPU 61 detects the defect detection signal Sk having a level equal to or higher than a predetermined value as a defect (defect including a chuck mark) in the chamfer portion 1d, and the work area 62d. The level value is stored in each predetermined storage position and the number is counted. At this time, the detection signal of the relatively large pulse point P3 is compared with a predetermined reference value and excluded as a foreign matter detection signal.
The predetermined reference value is selected as a level at which the detection signal of the point P3 with respect to the foreign matter is eliminated, and wrinkles due to chuck marks or other wrinkles can be detected.

Next, the MPU 61 calls the defect size determination program 62b.
The defect size determination program 62b is executed by the MPU 61, and the MPU 61 has three stages of large, medium, and small defects from the level of each detection signal of the defect detection signal Sk stored at a predetermined storage position in the work area 62d. And stored in a predetermined storage location different from the above in the work area 62d. Then, the disk pass / fail judgment program 62c is called.
The disk pass / fail determination program 62c is executed by the MPU 61, and the MPU 61 rejects when there is one large size data by referring to the size-classified data stored in the work area 62d. It is also rejected when there are two or more insides. If there are more than 5 small items, it will be rejected. As a result of the pass / fail judgment, the disk whose front side is rejected is displayed on the display 63, and the rejected disk is removed from the spindle 2 by the handling robot and transported to the rejected cassette (NG cassette). Is done.

For the disk that has passed the inspection of the front side chamfer part ChU, the MPU 61 drives the disk reversing mechanism 8, reverses the accepted disk by the disk reversing mechanism 8, and uses the back side chamfer part ChD as the outer chamfer part 1d. Re-insert into 2
Then, after waiting for the index signal IND, the same inspection as described above is performed on the rear chamfer section ChD.
The MPU 61 displays the result of the pass / fail determination of the inspection disk on the display 63 when the back-side disk pass / fail determination is completed, and conveys the failed disk to the NG cassette.
As a result, the disc that failed on either the front or back side is stored in the NG cassette, and the disc that is G (passed) is stored in the pass (G) cassette. End and proceed to the inspection of the next new disc to be inspected.
Incidentally, as described above, in the embodiment of FIG. 1, the pulse-like detection signal at the point P3 is excluded in comparison with the predetermined reference value. However, the detection signal at the point P3 and the detection signal at the point KF are excluded. For the exclusion, a comparator for comparing the defect detection signal Sk with a predetermined reference value may be provided between the comparison amplifier 54 and the A / D 55 so that the detection signal at the point P3 is excluded from the defect detection signal Sk. Next, an example will be described.

FIG. 5 is a block diagram of a defect detection circuit using another received light signal reference level fluctuation suppression circuit. The defect inspection apparatus 10 uses a defect detection circuit 7 instead of the defect detection circuit 5 of FIG.
In the defect detection circuit 7, the connection relationship between the LPF 52 and the HPF 53 in FIG. 1 is reversed, and the LPF 52 is cascade-connected after the HPF 53. The output of the LPF 52 is input to the comparator 54a, and the output “1” or “0” of the comparator 54a is input to the A / D 55. As a result, when the period “1” of the comparator 54a is long, the level “1” corresponding to the period is continuously converted to A / D in a predetermined cycle.
Note that a defective bit memory may be provided in place of the A / D 55 to store bit data for one round of the disk, and the MPU 61 may read the bit data.
Normally, the configuration in which the LPF 53 is cascade-connected to the HPF 52 is a BPF (bandpass filter).

Here, the HPF 53 sets the cutoff frequency to 200 Hz and sets the fluctuation frequency of the signal reference level of the received light signal corresponding to the frequency due to the vertical fluctuation of the outer peripheral surface of the disk to be equal to or lower than the cutoff frequency, thereby A signal obtained by smoothing the signal reference level by removing the frequency due to shake is extracted. Thereby, the fluctuation | variation of the reference level of a received light signal is suppressed.
The LPF 52 sets the cutoff frequency to 3 MHz. This is a filter that cuts high frequency noise from the received light signal and eliminates defect detection signals including foreign matter.
Eventually, a defect detection signal is extracted by providing a filter having a BPF band of 200 Hz to 3 MHz consisting of HPF 53 and LPF 52.
By inputting this defect detection signal to the (−) input of the comparator 54a having the reference value (threshold value) Vth as a comparison reference on the (+) input side, points P1, P2, Each detection signal at P3 is cut from the defect detection signal to obtain a detection signal at point KF obtained by removing the detection signal at point P3 from the defect detection signal Sk shown in FIG.
The reference value Vth of the comparator 54a is adjusted to a value for removing the detection signal at the point P3.

Although the comparison amplifier is used in the embodiment of FIG. 1 as described above, a normal comparator or differential amplifier can be used when the level of the received signal amplified by the amplifier is large.
In the embodiments, an aluminum disk (aluminum substrate, a magnetic disk having an aluminum substrate) is described as an example. However, the present invention is not limited to an aluminum disk, but a magnetic having a glass substrate. It can also be applied to discs and other media discs.
Further, although the APD is used as the light receiver of the embodiment, various light receiving elements and light receivers such as a CCD and a photomultiplier can be used in the present invention.

Furthermore, in the embodiment, only the front side chamfer part of the disk is to be inspected. However, the present invention provides a light receiver corresponding to the back side chamfer part, and irradiates the back side chamfer part with a light beam. You may make it detect the outer periphery defect of the chamfer part of a back surface side with the light receiver provided in the side. Moreover, you may make it detect the outer periphery defect of the chamfer part of front and back simultaneously.
Further, in the embodiment, the irradiation light is a laser beam, but the irradiation light may be white light.
The term “defect” in this specification is used not only as a deficiency or a deficiency but also as a broad concept for the general public, and this also applies to the term in the claims.

FIG. 1 is an explanatory diagram of an embodiment of an aluminum disk peripheral surface defect detection apparatus to which the disk peripheral surface defect detection method of the present invention is applied. FIG. 2A is an explanatory diagram when foreign matter adheres to the chamfer portion of the disk, and FIG. 2B is an explanatory diagram when wrinkles due to chuck marks or the like are present on the chamfer portion of the disk. FIG. 3 is an explanatory diagram of detection signals for one track. FIG. 4A is an explanatory diagram of a signal waveform obtained by filtering the detection signal of the light receiver, and FIG. 4B is an explanatory diagram of a defect detection signal that has passed through the reference level fluctuation suppression circuit. FIG. 5 is a block diagram of a defect detection circuit using another reference level fluctuation suppression circuit for received light signals. FIG. 6A is an explanatory diagram of a glass disk, and FIG. 6B is an explanatory diagram of an outer peripheral edge portion and defects.

Explanation of symbols

1 ... aluminum disk, 1a ... outer chamfer part,
2 ... Spindle, 3 ... Defect detection optical system,
3a ... Projection system, 31 ... Light source (laser light source),
4 ... light receiving system, 41 ... imaging lens, 42 ... aperture plate, 43 ... light receiver,
5, 7 ... Defect detection circuit,
51 ... Preamplifier, 52 ... LPF (low pass filter),
53 ... HPF (High Pass Filter),
54, 54a ... comparator, 55 ... A / D,
6 ... Data processing device, 61 ... MPU,
62 ... Memory, 62a ... Defect detection program,
62b ... Defect size determination program,
62c: Disc pass / fail judgment program,
62d: Work area. 63 ... Display,
64 ... Keyboard,
8 ... disk reversing mechanism, 10 ... defect inspection device,
Q: Inspection area.

Claims (15)

In the disk peripheral surface defect detection method of detecting a defect on the outer peripheral surface of the disk,
Irradiating the outer chamfer part with a light beam at an incident angle in a range of 45 ° ± 5 ° with respect to the surface of the outer chamfer part of the rotating disk;
A regular reflection light from the outer peripheral chamfer part is received through a diaphragm with a light receiver provided at a predetermined distance from the outer peripheral chamfer part to obtain a received light signal,
A disc peripheral surface defect detection method for obtaining a detection signal of a defect on the outer peripheral surface by suppressing or canceling the fluctuation of the signal reference level of the received light signal due to the shake of the outer peripheral surface caused by the rotation of the disc.   The disk peripheral surface defect detection method according to claim 1, wherein a specularly reflected light corresponding to a width of the outer peripheral chamfer portion is allowed to pass by selecting a hole diameter of the diaphragm.   A low-pass filter or a band-pass filter that passes a signal having a frequency corresponding to the fluctuation of the signal reference level in order to suppress or cancel the fluctuation of the signal reference level of the received light signal, and the fluctuation of the signal reference level 3. The disk periphery according to claim 2, wherein the light reception signal is passed through any one of the filter circuits of a high-pass filter that blocks a signal having a frequency to be received, and a defect detection signal on the outer peripheral surface is obtained based on the signal obtained from the filter circuit. Surface defect detection method.   The filter circuit includes another high-pass filter that removes high-frequency noise and a defect detection signal, and responds to fluctuations in the signal reference level through the other high-pass filter and one of the low-pass filter and the band-pass filter. 4. The disk peripheral surface defect detection method according to claim 3, wherein a frequency signal is obtained as a detection reference signal, and a detection signal of the defect on the outer peripheral surface is obtained by comparing this signal with the received light signal.   The high-pass fill is a band-pass filter, and the filter circuit uses the band-pass filter to eliminate the frequency signal due to the shake of the outer peripheral surface and extract the received light signal that has smoothed the signal reference level of the received light signal. 4. The disk peripheral surface defect detection method according to claim 3, wherein a detection signal of the peripheral surface defect is obtained based on the extracted received light signal.   6. The disk peripheral surface defect detection method according to claim 5, wherein the extracted light reception signal is compared with a predetermined reference value by a comparator to obtain a detection signal of the peripheral surface defect. In the disk peripheral surface defect detection device for detecting defects on the outer peripheral surface of the disk,
A light projecting system that irradiates the outer chamfer part with a light beam at an incident angle in a range of 45 ° ± 5 ° with respect to the surface of the outer chamfer part of the rotating disk;
A light receiver that receives a specularly reflected light from the outer peripheral chamfer part through a diaphragm provided at a predetermined distance from the outer peripheral chamfer part and generates a light reception signal;
A reference level fluctuation suppression circuit that suppresses or cancels fluctuations in the signal reference level of the received light signal due to fluctuation of the outer circumference of the disk caused by rotation of the disk;
A disk peripheral surface defect detection apparatus for obtaining a detection signal of the peripheral surface defect based on a signal obtained from the reference level fluctuation inhibiting circuit.   The disk peripheral surface defect detection apparatus according to claim 7, wherein the aperture diameter of the aperture allows specular reflection light corresponding to the width of the outer peripheral chamfer portion to pass therethrough.   The reference level fluctuation suppression circuit is one of a low-pass filter or a band-pass filter that passes a signal having a frequency corresponding to the fluctuation of the signal reference level, and a high-pass filter that blocks a signal having a frequency corresponding to the fluctuation of the signal reference level. The disk peripheral surface defect detection apparatus according to claim 8, wherein a detection signal of a defect on the outer peripheral surface is obtained based on a signal obtained by passing the received light signal through the filter circuit. The filter circuit includes either the low-pass filter or the band-pass filter and another high-pass filter that removes high-frequency noise and a defect detection signal.
The reference level fluctuation suppression circuit removes high frequency noise and a defect detection signal through the other high-pass filter to obtain a signal having a frequency corresponding to the fluctuation of the signal reference level as a detection reference signal, and the detection reference signal The disk peripheral surface defect detection apparatus according to claim 9, wherein a defect detection signal is obtained for a defect on the outer peripheral surface by comparing the received light signal with the received light signal.   The light beam is laser light, the light receiver is arranged in a direction perpendicular to the surface of the disk, and the detection reference signal and the light reception signal are one of a comparison amplifier, a comparator, and a differential amplifier. The disk peripheral surface defect detection apparatus according to claim 10, which is compared with each other.   The high-pass fill is a band-pass filter, and the band-pass filter is used to extract the light-receiving signal obtained by smoothing the signal reference level of the light-receiving signal by eliminating the signal of the frequency due to the shake of the outer peripheral surface. The disk peripheral surface defect detection device according to claim 9, wherein a detection signal of the defect on the outer peripheral surface is obtained based on a light reception signal.   Further, a comparator is provided, the light beam is laser light, the light receiver is arranged in a direction perpendicular to the surface of the disk, and the extracted signal is compared with a predetermined reference value by the comparator. The disk peripheral surface defect detection apparatus according to claim 12, wherein a detection signal of a defect on the outer peripheral surface is obtained based on an output of the comparator.   The A / D conversion circuit and a data processing device are further included, and the defect detection signal is input to the data processing device as a digital value by the A / D conversion circuit. 14. The disk peripheral surface defect detection apparatus according to claim 13, wherein it is determined whether or not the outer peripheral surface is a defect according to a level, and whether the disk is acceptable or not is determined based on the number of defects on the outer peripheral surface.   The disk peripheral surface defect detection device according to claim 14, wherein the disk is selected from an aluminum substrate, a magnetic disk having an aluminum substrate, a magnetic disk having a glass substrate, and other media disks. .

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