JP3141974B2 - Peripheral defect detecting apparatus and peripheral defect detecting method for glass disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system for detecting an outer peripheral defect of a glass disk and a method of detecting the outer peripheral defect.

[0002]

2. Description of the Related Art A magnetic disk as an information recording medium is made of a glass disk as a raw material and has a magnetic film formed thereon. Although the surface of a glass disk is polished to be smooth, the edge of the outer periphery may be chipped during a polishing operation or during handling, thereby deteriorating the quality of the disk.
When the degree of chipping is small, re-polishing is performed. When the degree of chipping is large, the disk is determined to be defective, and the degree of chipping is inspected and determined by an inspection device.

Referring to FIG. 3, an outer peripheral edge portion of a glass disk and a chipped defect thereof will be described. In FIG. 3A, the glass disk 1 has various outer diameters, each of which has a center hole H having a predetermined diameter. (b) shows a cross section of the outer peripheral portion, wherein the upper surface is 1a and the lower surface (back surface) is 1b.
, And the side surface of the outer circumference is 1c. The disk 1 is chamfered in the vicinity of the side surface 1c, and the upper peripheral portion (hereinafter, chamfer)
ChU and a lower chamfer Chd are formed, and a range of a length d inward from the side surface 1c is defined as an outer peripheral edge portion E,
The chipping generated here is defined as an outer peripheral defect K. The length d depends on the size of the disk 1, and for example, is 0.2 mm for 2.5 inches.

FIG. 4 shows a part of the structure of an inspection apparatus conventionally used for inspecting the surface defects of various disks, which is applied to the inspection of the outer peripheral defects of a chamfer. The glass disk 1 to be inspected is mounted on the spindle 2 and rotates θ. With respect to the surface of the disk 1, for example,
The light projecting system 3 is provided at an incident angle θT of about 30 °, and is moved in the direction of the radius R of the disk 1 and stopped at a position corresponding to the outer peripheral edge E. The laser beam LT from the laser light source 31 is focused on the spot SP by the focusing lens 32 and projected on the outer peripheral edge portion E. If there is a defect K, the spot SP is scattered, and the scattered light LR is condensed by the condensing lens 41 of the light receiving system 4 provided with the direction of the regular reflection angle with respect to the incident angle θT as the light receiving angle θR. Is divided into transmission and reflection.

The transmitted scattered light LR is transmitted to a spatial filter 43.
The specular reflection component is removed by the
Received. Only the specular component of the reflected scattered light LR passes through the circular hole of the slit plate 45 and is received by the light receiver 46. When there is no defect K or when the defect K is minute,
The light reception signal of the light receiver 44 is 0 or minute, and the light reception signal of the light receiver 46 is large. On the contrary, if the defect is large to some extent, the light receiving signal of the light receiving device 44 is large and the light receiving signal of the light receiving device 46 is small. Each light reception signal of both light receivers 44 and 46 is
The signal is input to a signal processing circuit (not shown) to calculate the difference between the two received light signals.
The N ratio is improved, and the outer peripheral defect K is detected by comparison with a predetermined threshold value.

[0006] The defect K at the outer peripheral edge portion E is as follows.
Depending on its location, the scattered light may not be received by the light receiving system 4. This will be described with reference to FIG. FIG. 5 exemplifies the positions of various defects K in the outer peripheral edge portion E. FIG. 5A shows the position existing on the surface 1a, which is referred to as a defect Ka. (B) is Kb of the upper chamfer ChU, and (c) is Kc, which straddles the chamfer ChU and the side surface 1c, and (d) is the surface 1a.
And the chamfer ChU and the side face 1c. Although there are also the back surface 1b and the lower chamfer ChD, since the disk 1 is inverted and inspected, these defects Ka to Kd are used here.
May be considered.

In the above inspection apparatus, the incident angle θT of the light projecting system 3 and the light receiving angle θR of the light receiving system 4 are set to be equal to about 30 °, while the scattered light LR of the defect Ka rises upward. Since the light is scattered, the light is well received by the light receiving system 4 and is reliably detected. However, in the defect Kb, the chamfer ChU
Is inclined and scattered obliquely to the upper right, so that there are many that do not enter the light receiving angle θR of the light receiving system 4 and the detection is uncertain. At the defect Kc, the scattered light LR is mainly scattered rightward, so that only a small amount of light is received by the light receiving system 4 and, therefore, is hardly detected. However, the defect Kd
The light scattered on the surface 1a is received by the light receiving system 4 and detected almost satisfactorily.

[0008]

In the light receiving system 4 described above,
Since the detection of the defect Kb is uncertain and the defect Kc is hardly detectable, there is a demand for an optical system capable of receiving the scattered light of each defect, including these, without fail. The present invention
An object of the present invention is to provide an optical system capable of receiving scattered light of the above-described various types of defects existing at different positions on the outer peripheral edge portion of a glass disk and a method of detecting the defects.

[0009]

SUMMARY OF THE INVENTION A feature of the apparatus for detecting an outer peripheral defect of a glass disk according to the present invention is that, in the above-described conventional defect inspection apparatus, the light-projecting system is used as it is and the conventional light-receiving system is used as the first light-receiving system. , And a second light receiving system is added thereto. The second light receiving system has a light receiving angle in a direction different from that of the first light receiving system with respect to the incident angle of the light projecting system, and is located at an upper peripheral portion of the outer peripheral edge portion by the irradiation light from the light projecting system.
Provided at a position capable of receiving light scattered light due to scattering light and / or outer circumferential defects, including missing present across the outer peripheral surface of the peripheral portion and the outer peripheral edge portion by the outer peripheral defects, including missing the first A chip defect that cannot be detected by the light receiving system is detected by the second light receiving system.

A feature of the method for detecting an outer peripheral defect of a glass disk according to the present invention is that a laser spot is projected at a predetermined incident angle onto an outer peripheral edge of a rotating glass disk, and a regular reflection angle with respect to the incident angle. the direction and the acceptance angle
Chipping the outer peripheral receives a part or all of the light scattered by the outer peripheral defects existing in the edge portion, and overlying the periphery of the outer peripheral edge portion and a light receiving angle <br/> a direction different from the light-receiving angle Including
Chipping defect by receiving the scattered light due to the outer peripheral defect and / or the scattered light due to the outer peripheral defect including the chip existing over the peripheral edge portion and the outer peripheral side surface of the outer peripheral edge portion.
Is to detect an outer peripheral defect including.

[0011]

In the above outer peripheral defect detecting device, the light projecting system, as in the prior art, is used for the rotating glass disk.
The laser spot is projected at a predetermined angle, for example, an incident angle of about 30 °. The first light receiving system, similar to the conventional light receiving system, has the direction of the regular reflection angle with respect to the incident angle as the light receiving angle, and receives the scattered light of the defect existing on the upper surface of the outer peripheral edge portion. In contrast, the added second light receiving system has is provided in the direction perpendicular to the outer peripheral surface, the chipping defects present across missing defect or the chamfer and the outer peripheral side surface, of the upper chamfer scattering Since the light is mainly scattered in the direction of the second light receiving system, the light is well received by the second light receiving system. That is, in the present invention, the first light receiving system
A chip defect that cannot be detected more is detected by the second light receiving system.
You . In addition, the defect which straddles the upper surface, the upper chamfer, and the outer peripheral side surface is received by both the first and second light receiving systems. This is the same for the method of detecting the outer peripheral defect. As described above, the scattered light of each of the defects is received without any light receiving system or both, and the respective light receiving signals are compared with the threshold value set in the signal processing circuit, and the magnitude of the light receiving signal exceeds the threshold value. As long as each defect is detected reliably.

[0012]

FIG. 1 shows an embodiment of a glass disk inspection apparatus to which the peripheral defect detecting apparatus and the peripheral defect detecting method of the present invention are applied. The inspection apparatus includes a spindle mechanism 2 which mounts and rotates a glass disk 1 to be inspected as in the prior art, an optical system 3 which projects a laser spot Sp on the disk 1 at an incident angle θT, and an optical system 3 for the incident angle θT. There is provided a light receiving system 4 provided at a light receiving angle θR in the direction of the regular reflection light, and this is defined as a first light receiving system. On the other hand, the second light receiving system 5
Is added. The second light receiving system 5 is provided in a direction perpendicular to the outer peripheral side surface 1c of the disk 1, and includes a condenser lens 51 and a light receiver 52.

In the defect inspection, a laser spot Sp is projected by the light projecting system 3 onto the outer peripheral edge E of the rotating glass disk 1, and the scattered light LR of each outer peripheral defect is
Each of the first light receiving system 4 and the second light receiving system 5 or both receive light. (A) to (D) shown in FIG.
The directivity of each of the scattered lights LRa to LRd is shown corresponding to each of the defects Ka to Kd in FIGS.
Since the scattered light LRa of (a) is scattered upward, it is received by the first light receiving system 4 as in the conventional case. (B) Scattered light LRb
Although a part thereof faces upward, most of it faces the horizontal direction, the light is mainly received by the second light receiving system 5. Since the scattered light LRc in (c) is directed almost horizontally, the second light receiving system 5
Received. Further, the scattered light LRd of (d) is the surface 1a
Is received by the first light receiving system 4, and the scattered light of the chamfer ChU and the side surface 1c is received by the second light receiving system 5.

As described above, one of the two light receiving systems 4 and 5
Alternatively, the received light signals of the scattered lights LRa to LRd received by both are compared with a threshold value set in the signal processing circuit, and all the outer peripheral defects Ka to Kd having a size exceeding this threshold value are reliably detected. . By the way, in the embodiments, the glass substrate itself is used as an example of the glass disk. However, even in the state of the final product magnetic disk in which the magnetic layer and the protective layer are applied to the glass substrate, the peripheral portion is exposed and the portion is formed of the glass substrate. Some remain. Therefore, the glass disk referred to here including the claims is treated as a concept including a magnetic disk in which the peripheral edge portion is exposed as described above. Similarly, the word "defect" in this specification is used not only for defects and omissions but also for a general concept of flaws, and the same applies to the terms in the claims.

[0015]

As described above, in the outer peripheral defect detecting apparatus and the detecting method according to the present invention, the scattered light of various defects existing at the outer peripheral edge portion of the glass disk and having different locations exists. Received by the first and second light receiving systems,
As long as the light receiving signal exceeds a predetermined threshold value, each defect can be reliably detected and inspection can be performed, and greatly contributes to the inspection of the outer periphery of the glass disk.

[Brief description of the drawings]

FIG. 1 shows one embodiment of a glass disk inspection apparatus to which an outer peripheral defect detecting apparatus and an outer peripheral defect detecting method of the present invention are applied.

FIG. 2 shows the directivity of scattered light from various peripheral defects Ka to Kd.

FIG. 3 shows an outer peripheral edge portion E of a glass disk;
FIG. 4 is an explanatory diagram of the defect K.

FIG. 4 is a configuration diagram of a conventional defect inspection apparatus for a glass disk.

FIG. 5 is a view showing various types of defects K in an outer peripheral edge portion E;
FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass disk, 1a ... Upper surface, 1b ... Lower surface (back surface), 1c ... Peripheral side surface, 2 ... Spindle or spindle mechanism, 3 ... Projection system, 31 ... Laser light source, 3
2 ... focusing lens, 4 ... light receiving system, or first light receiving system, 4
DESCRIPTION OF SYMBOLS 1 ... Condensing lens, 42 ... Half mirror, 43 ... Spatial filter, 44 ... Light receiver, 45 ... Slit plate, 46 ... Light receiver, 5 ... Second light receiving system, 51 ... Condenser lens, 52 ... Light receiver E: outer peripheral edge portion, K, Ka, Kb, Kc, Kd ...
Outer peripheral defect, d: length, ChU: upper peripheral portion (chamfer), Chd: lower peripheral portion (chamfer), LT: laser beam, Sp: laser spot, θT: incident angle, θ
R: Regular reflection angle or light reception angle, LR, LRa, LRb, LR
c, LRd: scattered light.

Continuing on the front page (72) Inventor Masaomi Takeda 2-6-1 Otemachi, Chiyoda-ku, Tokyo Inside Hitachi Electronics Engineering Co., Ltd. (72) Inventor Akinori Kurikawa 2-7-5 Nakaochiai, Shinjuku-ku, Tokyo e (56) References JP-A-64-57154 (JP, A) JP-A-3-186739 (JP, A)

Claims (4)

(57) [Claims] 1. A spindle mechanism for mounting and rotating a glass disk to be inspected, and a projection mechanism for projecting a laser spot at a predetermined incident angle onto an outer peripheral edge of the glass disk rotated by the spindle mechanism. An optical system, a first light receiving system that receives a part or all of scattered light due to an outer peripheral defect existing at the outer peripheral edge with a direction of a regular reflection angle with respect to the incident angle as a light receiving angle, and A direction different from that of the first light receiving system is defined as a light receiving angle, which is present on the upper peripheral portion of the outer peripheral edge portion by the irradiation light from the light projecting system.
The 2 provided at a position capable of receiving light scattered light by the outer circumferential defects, including missing that are present across the scattered light and by an outer peripheral defects, including missing / or the peripheral portion and the outer peripheral surface of the outer peripheral edge portion of A defect detecting device that detects a chipped defect that cannot be detected by the first light receiving system by the second light receiving system. 2. The light receiving system according to claim 1, wherein the first light receiving system has a first light receiving device for receiving scattered light due to a defect existing on the surface of the glass disk and a second light receiving device for receiving a specularly reflected light component. 2. The outer peripheral defect detecting device for a glass disk according to claim 1. 3. A laser spot is projected at a predetermined incident angle onto an outer peripheral edge of a rotating glass disk,
Wherein the direction of the specular reflection angle with respect to the incident angle and the light receiving part or all of the light scattered by the outer peripheral defects present in Kigaishu edge prior to the acceptance angle, and the front direction different from the acceptance angle and the acceptance angle overlying the periphery of Kigaishu edge portion
In order to receive the scattered light due to the outer peripheral defect including the notch and / or the scattered light due to the outer peripheral defect including the notch existing over the peripheral edge portion and the outer peripheral side surface of the outer peripheral edge portion.
A method for detecting an outer peripheral defect of a glass disk, wherein the outer peripheral defect including a more defective defect is detected . 4. An apparatus according to claim 1, wherein said outer peripheral edge portion is located on an upper peripheral portion of said outer peripheral edge portion .
The scattered light due to the outer peripheral defect including the chipped portion and / or the scattered light due to the outer peripheral defect extending over the peripheral portion and the outer peripheral side surface of the outer peripheral edge portion is received in a direction perpendicular to the outer peripheral side surface of the glass disk. 4. The method according to claim 3, wherein the defect is detected.