JP4312638B2 - Peripheral surface defect detection optical system of translucent disk, peripheral surface defect detection device, and peripheral surface defect detection method - Google Patents

Description

  The present invention relates to a peripheral defect detection optical system, a peripheral defect detection apparatus, and a peripheral defect detection method for a translucent disc (semi-transparent or transparent disc). The present invention relates to a peripheral defect detection optical system for a glass disk that can detect defects such as cracks and chippings in an edge portion from each other without detecting adhering foreign matters and can detect them efficiently and with high accuracy.

  In recent years, magnetic disks used as information recording media such as computers have been increasingly required to have a higher storage density, and as a result, films such as magnetic layers and protective films formed on the surface have become thinner. As an example of the manufacturing process of a magnetic disk using a glass disk substrate, first, as shown in FIG. 7, the glass disk is polished with a lapping device (lapping process (1)), and then both surfaces of the glass substrate are polished. There is a step of polishing and polishing the surface to an average surface roughness of about 1 nm (polishing step (2)). Thereafter, the glass substrate is cleaned (first cleaning step (3)), and surface defect inspection and peripheral surface defect inspection are performed (first surface inspection step (4)). Then, the passed glass substrate is cleaned (second cleaning step (5)), and a metal underlayer having a thickness of about 50 to 2000 mm made of chromium, copper, NiAl or the like is formed by a sputtering method or the like (metal underlayer forming step ( 5)) Subsequently, a magnetic layer made of a cobalt-based ferromagnetic alloy thin film or the like having a thickness of about 100 to 1000 mm is formed by sputtering or the like (magnetic layer forming step (7)), and further, for example, a carbon film or a hydrogenated carbon film There is a step of forming a protective film made of a nitrogenated carbon film or the like having a thickness of about 10 to 150 mm (protective film forming step (8)). After the protective film is formed in such a manufacturing process, the surface of the magnetic disk is cleaned with a polishing apparatus in order to remove small protrusions generated in the film forming process and clean the surface (burnish and wiping). Step (9)) and finally surface inspection is performed again (second surface inspection step (10)).

  Recently, a magnetic disk, which is one of information recording media, is made of a glass disk, and a magnetic film is formed thereon. The surface of a glass disk is smoothened by polishing the surface. However, the edge of the inner periphery or the outer periphery may be chipped or cracked during polishing work or handling, thereby reducing the quality of the disk. In the first surface inspection step (4), chipping, cracking, etc. are inspected, and when the degree is small, the surface is re-polished. The degree of 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, each having 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 chamfered in the vicinity of the side surface 1c to form an upper peripheral edge portion (hereinafter referred to as chamfer) ChU and a lower chamfer ChD, and the range of the inner length d from the side surface 1c is the outer peripheral edge portion E ( The chip or crack generated here is the peripheral defect K. Note that the length d varies depending on the size of the disk 1, and is, for example, 0.2 mm in the case of 2.5 inches.

Recently, such a glass disk substrate has become mainstream, and its thickness is further reduced, and the length d is further shortened due to the demand for high-density recording. For this reason, the conventional peripheral surface defect inspection method cannot perform sufficient detection.
As a conventional defect detection method for the outer peripheral edge, in addition to the first light receiving system for projecting light to the chamfer part at an incident angle of about 30 ° as viewed from the normal to the upper part of the outer peripheral part and receiving scattered light, An invention by the applicant having a second light receiving system for receiving scattered light in a direction facing the outer peripheral side surface of the disk is known (Japanese Patent No. 3141974-JP-A-7-190950-Patent Document 1).
Furthermore, although it is not a peripheral surface defect, a linear light is irradiated from the upper part of the transparent disk to the disk surface, and this is totally reflected inside the disk to receive scattered light from the outer peripheral side surface and receive a defect on the disk surface. There is a known defect detection device for detecting the above (Patent Document 2).

JP 7-190950 A (Patent No. 3141974) JP-A-64-57154

In recent years, disk drives (HDDs) have come to use high-speed disks exceeding 5400 rpm in addition to further increasing the recording density. For this reason, the thickness of the glass disk is reduced, and the recorded track portion is set to the outermost or innermost limit. As a result, smaller peripheral surface defects (chip defects and crack defects) occurring on the inner periphery or outer periphery have affected the disk quality more than ever. There is a high probability of causing a failure when such a disk is incorporated in the HDD.
When a smaller peripheral surface defect is a problem, if a chip defect or a crack defect existing at the outer peripheral edge of the disk is detected by the technique disclosed in Japanese Patent Application Laid-Open No. Hei 7-190950, There is a drawback that adhering foreign matter is also detected at the same time. Therefore, there is a problem that the product yield deteriorates. Therefore, at present, the defect detection technique disclosed in Japanese Patent Application Laid-Open No. Hei 7-190950 has been unable to cope with the manufacture of high-density recording HDD devices. For this reason, there is a strong demand for more accurate detection of chipping defects and cracking defects at the outer peripheral edge portion, which excludes the detection of attached foreign matter.
The object of the present invention was made in response to the above-mentioned request, and the defect such as cracking and chipping of the outer peripheral edge portion with respect to the translucent disc was efficiently separated from this without almost detecting the attached foreign matter, An object of the present invention is to provide a peripheral surface defect detection optical system, a peripheral surface defect detection device, and a peripheral surface defect detection method for a translucent disc that can be detected with high accuracy.

The structure of the peripheral defect detecting optical system and the peripheral defect detecting device of the translucent disc according to the present invention is such that a light beam is incident on the peripheral surface of the translucent disc to be inspected at a predetermined incident angle. A light projecting system that irradiates the inspection area on the outer peripheral surface or inner peripheral surface of the disk from the inside through the inside of the disk, and scattered light from the inspection area that is provided in the vicinity of the inspection area outside the disk. A first light receiving system and a second light receiving system.
Further, the light beam is a laser beam that is a spot, the peripheral surface on which the light beam spot is incident is an outer peripheral surface, and the first light receiving system is a scattered light from the inspection region in the rotating disk. The disc is a glass disc, the spot is incident on the outer peripheral side of the outer peripheral surface, and the second light receiving system is on the outer peripheral side with respect to the diameter line of the disc passing through the inspection area. The scattered light from the inspection area that has propagated through the inside of the disk emitted to the outside of the disk at a position further separated from the position of the outer peripheral side surface symmetrical to the incident position of the spot is received outside the disk,
The light receiving surface of the first light receiving system is set to face the chamfer surface on the back side of the disk in order to detect defects in the disk chamfer, and detects a defect on the inner peripheral surface or outer peripheral side surface of the disk. Therefore, the light receiving surface of the second light receiving system is set to be substantially perpendicular to the chamfer surface on the back surface side of the disk .

In these inventions, as described above, the light beam spot is irradiated from the inside to the inspection area on the peripheral surface through the inside of the disk, and the first is provided in the vicinity of the inspection area outside the inside of the disk. The light receiving system receives scattered light from the inspection area and detects a peripheral surface defect of the disk. Therefore, almost no scattered light is generated from the foreign matter adhering to the outside of the disk.
As a result, various defects, excluding attached foreign matter, such as chipping defects and cracking defects present on the inner or outer edge of the glass disk, can be distinguished from these with little detection of attached foreign matter. It can be detected with accuracy.
By the way, since the disc has a hole in the central portion, here, the peripheral surface far from the central hole in the peripheral surface of the disc is defined as the outer peripheral surface, and the side along the central hole is here. The peripheral surface will be described as the inner peripheral surface.

FIG. 1 is an explanatory view of an embodiment of a glass disk inspection apparatus to which the detection optical system of the present invention is applied, FIG. 2 (a) is an explanatory view of the incident state of a laser spot on the disk, and FIG. An explanatory diagram of the relationship between the light beam incident on the inside of the disc and the inspection area,
3A is an explanatory diagram of the chamfer defect detection system, FIG. 3B is an explanatory diagram of the outer peripheral side defect detection system of the disc, and FIG. 3C is an illustration of the internal scattered light inside the disc and the outer peripheral side defect detection system. 4A is a plan view illustrating the principle of detecting a defect by giving a predetermined offset OF from the reflected light emission position of the disk, and FIG. 4B is a cross-sectional explanatory view of the outer peripheral portion thereof. FIG. 5 is an explanatory view of another embodiment of the present invention for detecting defects on the inner peripheral surface, FIG. 6 (a) is an explanatory view of the outer peripheral edge E of the glass disk and its defects, and FIG. 6 (b). FIG. 7 is a cross-sectional view of an outer peripheral portion thereof, and FIG. 7 is an explanatory view of an example of a manufacturing process of a magnetic disk using a glass substrate.

  In FIG. 1, a defect detection optical system 9 of a defect inspection apparatus 10 includes a spindle 2 that rotates with a glass disk 1 (hereinafter referred to as a disk) 1 to be inspected, and an incident angle θi≈45 ° with respect to a side surface of the disk 1. Then, a laser spot Sp from the laser light source 31 is irradiated to the side surface position P (see FIGS. 1 and 2B), and the inspection area (light-receiving outer peripheral surface) Q (see FIG. )) From the inside, a first light receiving system 4 (see FIG. 3A) that receives scattered light from the inspection area Q, and a first light receiving system that propagates scattered light from the inside of the disk from the inspection area Q. 2 light receiving systems 5 (see FIG. 3B).

As shown in FIG. 3A, the first light receiving system 4 includes an optical fiber 41 and a light receiving surface forming portion 42 (hereinafter referred to as a light receiving surface 42), and the light receiving surface 42 is projected light from the optical system 3. In the direction of the light receiving angle θj (see FIG. 3) with respect to the surface of the disk 1 so as to face the lower chamfer ChD of the inspection area Q inside the outer periphery of the disk 1 to be received, that is, parallel to the chamfer ChD surface. (See (a)) provided outside the surface of the disk 1.
The light receiving surface 42 may be the light receiving surface itself of the optical fiber 41 or may be formed as a light receiving member as a light receiving surface coupled to the end of the optical fiber 41.
Accordingly, scattered light from the chamfers ChU and ChD having a predetermined inclination from the horizontal direction can be easily received, but scattered light on the outer peripheral side surface perpendicular to the horizontal direction is difficult to receive. Therefore, the first light receiving system 4 becomes a detection system for detecting a chip defect in the chamfer portion.

On the other hand, as shown in FIG. 3B, the second light receiving system 5 includes an optical fiber 51 and a light receiving surface forming portion 52 (hereinafter referred to as a light receiving surface 52). From the emission position R (point R) at which the specularly reflected light from the laser spot Sp from the disk 1 is emitted to the outside, a predetermined offset OF, for example, a disk of about 3.3 inches has an OF of about 10 mm. In the detection position S (point S) of the outer peripheral surface, it is provided obliquely above this. The light receiving surface of the second light receiving system 5 is set in the light receiving angle θk direction (see FIG. 3B) with respect to the surface of the disk 1 so as to be perpendicular to the surface of the lower chamfer ChD.
This makes it easier to receive scattered light on the outer peripheral side surface perpendicular to the horizontal direction, but it is difficult to receive scattered light from the chamfers ChU and ChD having a predetermined inclination from the horizontal direction. Therefore, the second light receiving system 5 becomes a detection system for detecting a chip defect on the outer peripheral side surface.
The emission position R from which the specularly reflected light of the laser spot Sp is emitted is symmetrical to the incident position P on the side surface where the incident light enters with respect to (or with respect to) the Y axis (diameter line of the disk) passing through the inspection region Q. In the right position.

Here, the defect detection optical system 9 is configured such that a laser spot Sp is passed through the inside of the disk 1 by the light projecting system 3 to the outer peripheral edge E (see FIG. 6) of the rotating glass disk 1 from the inside to the outer periphery of the disk 1 Project to the part. This irradiation position by the laser spot Sp forms the inspection region Q. As shown in FIG. 3, the scattered light Lj of each peripheral surface defect is received by the first light receiving system 4, and the scattered light Lk in the vicinity of the specularly reflected light propagated therein is received by the second light receiving system 5. Is done.
Here, the first light receiving system 4 detects defects in the chamfer ChU and chamfer ChD in the inspection region Q by the light receiving surface 42. On the other hand, the second light receiving system 5 detects defects on the outer peripheral side surface by the light receiving surface 52. Thus, by providing a light receiving system for detecting a chamfer defect and a defect on the outer peripheral side surface, and dividing them into two systems, small chip defects and crack defects can be detected with higher accuracy. Further, the scattered light generated in the inspection region Q is obtained by the irradiation light from the inside of the disk 1, thereby preventing the detection of adhered foreign matter. This is because no foreign matter adheres to the inside of the disk 1. Even if foreign matter is simultaneously attached to the outer peripheral position having a chip defect or a crack defect, the scattered light is totally reflected with the peripheral surface or end face of the disk as a boundary surface, so that the light receiving surface 42 of the optical fiber 41 and the optical fiber 51 It does not reach the light receiving surface 52. Therefore, the defects detected by the detection optical system are mostly chip defects and crack defects at the outer peripheral edge portion.

FIG. 2 is an explanatory diagram of the light projecting system 3 that projects from the inside of the disk 1 to the outer periphery of the disk 1 in this case.
In FIG. 2A, reference numeral 31 denotes a laser light source of the optical system 3, which has a focusing lens therein, and the focal point of the laser beam 32 is F. The laser beam 32 is converged on the focal point F and then enters the incident position P of the outer peripheral surface 1c of the disk 1 as a laser spot Sp. Here, the disk 1 is 3.3 inches, and its thickness t is t = 1.27 mm.
The laser spot Sp at the incident position P of the outer peripheral surface 1c is an ellipse having a major axis having a width of about 1.0 mm, and the major axis has a height Z1 of the outer peripheral surface 1c excluding the chamfers ChU and ChD (FIG. 2). Corresponding to (b)), as shown in FIG. 1, for example, it is incident obliquely at θi = 45 °.

As shown in FIG. 2B, at this time, after being focused at the focal point F, the laser spot Sp of the laser beam 32 is at an angle .theta.p with respect to a line parallel to the disk surface and has a height Z1 on the outer peripheral surface 1c. Irradiated with. Then, it refracts and enters the inside of the disk, becomes an angle θq inside, reaches the inspection area Q from the incident position P, and has a height Z2 that covers the chamfers ChU and ChD and the outer peripheral side surface 1c in the inspection area Q. The positional relationship between the angle θp and the focal point F that satisfies this relationship is set.
Thereby, the obtained scattered light can be substantially limited to the chip defect or crack defect generated at the outer peripheral edge, and the influence of the scattered light from the foreign matter adhering to the front surface or the back surface of the disk 1 does not occur.
As described above, if the incident light θp is made smaller than the total reflection angle and is incident obliquely, the ratio of the light that exits from the front surface or the back surface of the disk 1 can be reduced. As a result, the scattered light from the attached foreign matter on the front surface or the back surface of the disk 1 is reduced, and the rate of detecting the attached foreign matter is reduced.
The angle θp of the incident light of the laser beam 32 with respect to the outer peripheral surface 1 c may be set larger than the total reflection angle with respect to the front surface or the back surface of the disk 1. This is because the light incident on the inside of the disc 1 is totally reflected on the inner side of the front surface and the inner side of the back surface and hardly comes out of the disc 1.
As shown in FIG. 1, at this time, the light incident on the inside of the disk is refracted according to the refractive index n = 1.536 of the glass, and enters the inspection region Q that coincides with the intersection with the Y axis that is the carriage traveling direction. Irradiated.

FIG. 3 is an explanatory diagram of the first and second light receiving systems 4 and 5.
As shown in FIG. 3A, the first light receiving system 4 includes an optical fiber 41, and is substantially parallel to the surface of the lower chamfer ChD in the inspection region Q at the outer peripheral edge portion. The angle θj is set. That is, the light receiving surface 42 of the optical fiber 41 is disposed at an angle of θj≈40 ° from the surface of the disk 1 and at a height of about 15 mm from the upper surface and at a distance of about 24 mm from the outer peripheral edge of the disk. ing. As a result, the light receiving surface 42 faces the surface of the lower chamfer ChD.
The rear end of the optical fiber 41 is connected to the light receiving surface of an avalanche photodiode (APD) built in the optical fiber light receiver (APD light receiving module) 43.
In FIG. 3A, the white solid arrow indicates the incident light of the laser spot Sp with respect to the inspection region Q, and the dotted arrow indicates the direct transmitted light of the laser spot Sp that passes through the inspection region Q.
On the other hand, the second light receiving system 5 also has an optical fiber 51 as shown in FIG. The second light receiving system 5 is located at a detection position S (light receiving position) that is further deviated from the emission position R that receives specularly reflected light (internally propagated reflected light) from the inspection region (light receiving surface) Q inside the disk 1. Set to an angle θk substantially parallel to the lower chamfer ChD on the lower side of the disk 1, that is, set to be above θk≈about 40 ° from the back surface and at a height of about 15 mm from the front surface, The light receiving surface 52 of the optical fiber 51 is disposed at a position about 24 mm away from the outer peripheral edge (the end surface) of the disk. The rear end of the optical fiber 51 is connected to the light receiving surface of an avalanche photodiode (APD) built in the optical fiber light receiver (APD light receiving module) 53.

The angles θj and θk may be angles that receive scattered light from the chamfer and the outer side surface, and are angles that avoid transmitted light or regular reflected light, and are angles at which a lot of scattered light is received. Is good. The range in which the angle can be selected is about 20 ° to 60 ° with respect to the front or back surface of the disk 1.
By the way, as shown in FIG. 3C, the light reflected in the direction inside the disk 1 in the inspection region Q at the outer peripheral edge part travels along the regular reflection light LR while being totally reflected and scattered inside the disk. Therefore, the offset OF is necessary as an appropriate position for capturing the scattered light. Further, the scattered light generated in the inspection region Q does not go out of the disk 1 but becomes internal scattered light, which is reflected multiple times between the outer peripheral surface inner side and the inner peripheral surface inner side. The set detection position S is reached.

FIG. 4 is a plan view for explaining the principle of defect detection having a predetermined offset OF from the emission position R of regular reflection light.
The radius r of the 3.3-inch disk 1 is set to 42 mm, and the refractive index n of the glass is set to 1.536. Then, the angle of the FIG. 4 (a), the incident angle .theta.i = 45 °, in the sectional view of FIG. 4 (b), the emission angle gamma = 40 DEG from the position of the detection position S (= θj), in its horizontal plane α (see FIG. 4A) = 0 °. Further, the offset OF from the position of the emission position R of the regular reflection light is set to 10 mm, and the X and Y axes are taken with the center of the disk 1 as the origin O.

Thereby, the coordinates (Xq, Yq) of the inspection region Q are (0, 42 mm), and the coordinates (Xp, Yp) of the incident position P are (34.3286 mm, −24.1981 mm). The coordinates (Xr, Yr) of the regular reflection light emission position R are symmetrical positions (−34.3286 mm, −24.1981 mm) with respect to the incident position P with respect to the Y axis. As a result, the coordinates (Xs, Ys) of the detection position S are Xs = −r · sin θs and Ys = −r · cos θs (−27.6351 mm, −31.6275 mm). However, θL = 2arcsin ((L / 2) / r) = 13.67428 °, θs = 2θt−θL = 41.14588 °, and L = OF = 10 mm. Here, θs is an angle when the central angle on the arc PS is 2θs, θL is the angle between the half angle of the central angle on the arc PR and the angle θs, θt = Arcsin (1 / n · sinθi) = 27.41008 ° and n = 1.536 (see FIG. 4).
When the coordinate point in the vicinity of the outer peripheral side surface of the inspection region Q is traced with light in the reverse direction from the point S to the point P at the angles α = 0 ° and γ = 40 ° of the point S, the coordinates of the reflected light obtained at the point S Q ′ is (−0.89097, 41.99055 mm).
The position of the coordinate Q ′ is a position near the coordinate Q (0, 42 mm) that is slightly shifted by about 0.9 mm in the X direction, and corresponds to the position where scattered light is generated.
Thereby, the scattered light of the outer peripheral edge part of the test | inspection area | region Q can be caught substantially. If the position of the point in the vicinity of this point Q deviates further, it will deviate from the scattered light receiving point, and conversely, if it is too close to the inspection region Q, it will receive regular reflection light, and defect detection on the outer peripheral side surface of the inspection region Q Can not.

Now, returning to FIG. 1, the detection signals of the respective optical fiber receivers 43 and 53 are input to the defect detection circuit 6 via the amplifiers 44 and 54, respectively. The defect detection circuit 6 receives detection signals from the amplifier 44 by bandpass filters (BPF) 61a and 61b, and comparators (COM) 62a and 62b detect defects from the detection signals that exceed the thresholds Tha and Thb. Detection signals Da and Db are generated as signals. Here, the threshold value Tha, Thb of, there is provided for noise removal, Ru is set from the control circuit 7.
The detection signals Da and Db are each sampled as bit data according to the sampling clock from the data sampling clock generation circuit 75 and stored in the defective memory 63.
The defect detection circuit 6 operates not only as a peripheral surface defect but also as a surface defect detection circuit of the disk 1. Here, a peripheral surface defect is detected using the same detection circuit 6.

A control circuit 7 includes an interface 71, a Y table drive circuit 72, a spindle motor drive circuit 73, an R / θ coordinate generation circuit 74, and a data sampling clock generation circuit 75. The thresholds Tha and Thb are sent from the data processing device 8 to the control circuit 7 as data.
Then, the control circuit 7 drives the motor 76 of the Y moving mechanism that moves the spindle 2 in the Y-axis direction (radius R direction) by the Y table driving circuit 72, and outputs R · θ from the encoder 77 provided in the motor 76. The coordinate generation circuit 74 obtains a coordinate position signal in the Y direction (radius R direction). Further, the spindle motor 78 is driven by the spindle motor driving circuit 73 to rotate the spindle 2. The R / θ coordinate generation circuit 74 obtains a coordinate position signal in the θ direction and an index signal serving as a rotation reference from an encoder 79 provided in the spindle motor 78.
The control circuit 7 is controlled from the data processing device 8 via the interface 71.
In such a control circuit 7, when a peripheral surface defect is detected, the Y table drive circuit 72 is set to a fixed value r without being moved. Then, the defect data for one round is collected in the defect memory 63 according to the index signal.

This will be described in detail below.
The R · θ coordinate generation circuit 74 receives a control signal from the data processing device 8 via the interface 71 and enters a peripheral surface defect detection operation. Then, an index signal which is the rotation reference position of the disk 1 is obtained from the encoder 79, and the data sampling clock generation circuit 75 is driven in accordance with this signal, thereby generating a sampling clock having a predetermined cycle. The generated sampling clock is supplied to the defective memory 63, the address is updated at the sampling clock cycle, and the bit data of the detection signals Da and Db are sequentially stored in the updated address positions. Then, the R · θ coordinate generation circuit 74 sends an inspection end signal to the interface 71 when the inspection for one rotation is completed with reference to the generation of the index signal, and simultaneously sends a stop signal to the data sampling clock generation circuit 75. Then, the sampling clock generation operation is stopped.
The interface 71 receives the inspection end signal from the R · θ coordinate generation circuit, and in response to this, reads out the defect detection data for each round of the defect detection signals Da and Db from the defect memory 63 to determine the first data position. Two types of defect data based on the defect detection signals Da and Db are sent to the data processing device 8 as the rotation reference of the disk 1.

The data processing device 8 includes an MPU 81, a memory 82, a CRT display 83, a keyboard 84, and the like, which are connected to each other via a bus 85. The memory 82 includes a defect classification program 82a, a defect size determination program 82b, a defect map display program 82c, and the like, and further includes stereoscopic image data 82d of the disc 1.
The defect classification program 82a is executed by the MPU 81, and the MPU 81 receives the defect detection data for one rotation for each of the defect detection signals Da and Db, and determines the defects on the defect detection signal Da side as chamfer ChU and chamfer ChD, respectively. The defect on the chamfer part is classified, and the defect on the defect detection signal Db side is classified as a defect on the outer peripheral side surface (end surface). Further, the position of the defect data is calculated by calculating the outer peripheral coordinate (θ coordinate) of each defect data position corresponding to the frequency of the sampling clock. The detection resolution at this time is determined by the frequency of the sampling clock and can be set to a high resolution.

Next, the MPU 81 executes the defect size determination program 82b and refers to both the chamfer part defect and the end face (outer peripheral surface) defect classified by the execution of the defect classification program 82a. The size of the defective bits is determined by grouping according to the continuity of the defective bits. At this time, the continuity between the defect of the chamfer part and the defect of the end face is also determined, and these are regarded as one defect. Here, the size of the defect is, for example, 5 levels. Next, the MPU 81 executes the defect map display program 82c to display the map by superimposing the detection reference position (index signal generation position) on the stereoscopic image video of the disk 1 as a reference. At this time, the defect of the chamfer part and the defect of the end face are color-coded, and the large grouped defect is displayed as a graphic divided into five levels.
Of course, when the defect of the chamfer part and the defect of the end face become one, both colors are superimposed.

FIG. 5 is an explanatory diagram of another embodiment of the present invention for detecting defects on the inner peripheral surface.
The incident angle θi of the laser spot Sp is 18.4 °, and the laser beam Lt refracted on the irradiation surface of the disk 1 and enters the inside is at the position of the inspection region (light receiving surface inside the inner peripheral surface of the disk) Q. It is set to irradiate at substantially 45 °. In addition, the laser beam Lt is set so that the straightly traveling light approaches the inner peripheral surface N of the disk 1 without contacting it in the direction in which the incident laser beam travels straight without refraction at the incident point P (see the dashed line in FIG. 5). The incident angle θi is set so that the straight light crosses the radial line of the disk 1 at a position H (point H) where the inner peripheral surface N closest to the inner peripheral surface N is not irradiated. If such conditions are set, it is possible to irradiate an incident laser beam having a large angle with respect to the inspection region Q on the inner peripheral surface. Thereby, the reflectance of the internal reflected light is increased, and the scattered light is increased accordingly. When the straight light comes into contact with the inner peripheral surface N, the disturbance light inside the disk 1 increases accordingly.
Therefore, as shown in the figure, when the intersection angle between the radial line of the disk 1 and the outer periphery is the reflected light emission position R, the incident angle θi is calculated in reverse and the optimum θi = 18.4 °. It becomes.
As a result, as shown in the drawing, the inspection region Q here is set inside the inner peripheral surface of the disk l and irradiated with the laser spot Sp refracted at the incident point P.
Here, as in the case of FIG. 4, the disk 1 is a 3.3 inch disk, the radius r is 42 mm, and the refractive index n of the glass is 1.536. θa = 38.7 °, θb = 12.1 °, θp = 32.8 °, θs = 20.3 °, and the irradiation angle θq to the point Q is θq = 45 °.
The inner diameter ri = 12.5 mm, the coordinates of the point P are (22.783, -35.283), and the coordinates of the point H are (-8.298, -10.340).

Incidentally, in this figure, the first light receiving system 4 and the second light receiving system 5 are not shown, but each is provided in the same manner as in FIG. The positional relationship between the inspection region Q and the first light receiving system 4 and the positional relationship between the second light receiving system 5 and the detection position S (point S) are the same as those shown in FIG. Omit. Further, the offset OF between the emission position R (point R) and the detection position S (point S) is about 10 mm as in the embodiment of FIG.
With such a configuration, a defect on the inner peripheral surface of the disk 1 can be detected.
The incident angle .theta.i is determined by the outer diameter r and inner diameter ri of the disk 1 and the position of the incident point P. For a 3.3 inch disk, the range of .theta.i = 15 DEG to 20 DEG is preferable. .

As described above, the received light signals of the scattered light Lj and Lk received by either or both of the light receiving systems 4 and 5 are compared with the thresholds Tha and Thb set by the control circuit 7 in the defect detection circuit 6. Are detected, sent to the data processing device 8 via the control circuit 7, classified, determined in size, and displayed on a map.
In the embodiment of FIG. 1, an example in which the light receiving position S is provided between the emission position R and the incident position P is shown. However, the light reception position S is provided between the emission position R and the inspection region Q. Also good. Similarly, in the embodiment of FIG. 5, the light receiving position S may be provided behind the emission position R with respect to the incident position P.
In the embodiment, a light receiver using an optical fiber is provided as a light receiving system, but this is not limited to a light receiver using an optical fiber, and various light receiving elements such as an image sensor, Can be used.
In the embodiment, the laser spot is irradiated to the inspection region by the laser light source. However, the present invention is not limited to such a laser pot and of course a general light beam may be used. It is.
By the way, in the embodiments, a glass disk is taken as an example, but since it is light transmissive even in the state of a final product magnetic disk in which a magnetic layer and a protective layer are attached to a glass substrate, it may be a detection target in the present invention. Furthermore, the present invention is not limited to such a glass disk, and it is needless to say that the present invention can be applied to defect inspection of the inner or outer peripheral edge of a general translucent disk.
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 view of an embodiment of a glass disk inspection apparatus to which the detection optical system of the present invention is applied. FIG. 2 is an explanatory diagram of the light projecting system portion. FIG. 3 is an explanatory diagram of the light receiving system portion. FIG. 4 is a plan view for explaining the principle of detecting a defect with a predetermined offset OF from the reflected light emission position of the disk. FIG. 5 is an explanatory diagram of another embodiment of the present invention for detecting defects on the inner peripheral surface. FIG. 6 is an explanatory diagram of the outer peripheral edge E of the glass disk and the defect R thereof. FIG. 7 is an explanatory diagram of an example of a manufacturing process of a magnetic disk using a glass substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Glass disk, 1a ... Upper surface, 1b ... Lower surface (back surface),
1c ... peripheral surface, 2 ... spindle,
3 ... light projecting system, 4 ... first light receiving system, 5 ... second light receiving system,
6 ... Defect detection circuit, 7 ... Control circuit,
8 ... Data processing device, 9 ... Defect detection optical system,
10: Defect inspection device,
31 ... Laser light source, 32 ... Laser beam,
41, 51 ... optical fiber, 42, 52 ... light receiving surface,
43, 53 ... optical fiber receiver, 44, 54 ... amplifier,
61a, 61b ... band pass filter (BPF),
62a, 62b ... comparators,
63 ... defective memory,
71 ... interface, 72 ... Y table drive circuit,
73 ... Spindle motor drive circuit,
74. R / θ coordinate generation circuit,
75: Data sampling clock generation circuit,
76: Y moving mechanism motor, 77, 79 ... encoder,
ChU ... Upper peripheral edge (Chamfer),
ChD: Lower peripheral edge (Chamfer),
81 ... MPU, 82 ... memory,
83 ... CRT display, 84 ... Keyboard,
82a ... defect classification program,
82b ... Defect size determination program,
82c ... Defect map display program.
LT ... laser beam, Sp ... laser spot,
θT… incident angle, θR… regular reflection angle or light receiving angle,
Lj, Lk ... scattered light.

Claims (3)

A light beam is incident on the peripheral surface of the translucent disc to be inspected at a predetermined incident angle, and the optical beam is irradiated from the inside to the inspection area of the outer peripheral surface or the inner peripheral surface of the disc through the inside of the disc. A floodlighting system,
A first light receiving system that is provided in the vicinity of the inspection area outside the inside of the disk and receives scattered light from the inspection area ;
A second light receiving system ,
The light beam is a laser beam, which is a spot, the peripheral surface on which the light beam spot is incident is the outer peripheral surface, and the first light receiving system is scattered from the inspection region in the rotating disk. Receive light,
The disk is a glass disk, and the spot is incident on an outer peripheral side surface of the outer peripheral surface,
The second light receiving system has a predetermined offset separation from the position of the outer peripheral side surface symmetrical to the incident position of the spot on the outer peripheral side surface with respect to the diameter line of the disk passing through the inspection region. The scattered light from the inspection area that has propagated inside the disk emitted to the outside is received outside the disk,
The light receiving surface of the first light receiving system is set to face the surface of the chamfer on the back side of the disk in order to detect defects in the chamfer of the disk,
The light receiving surface of the second light receiving system is set so as to be substantially perpendicular to the surface of the chamfer on the back surface side of the disc in order to detect defects on the inner peripheral side surface or the outer peripheral side surface of the disc. An optical system for detecting a peripheral surface defect of a translucent disc. A light beam is incident on the peripheral surface of the translucent disc to be inspected at a predetermined incident angle, and the optical beam is irradiated from the inside to the inspection area of the outer peripheral surface or the inner peripheral surface of the disc through the inside of the disc. A floodlighting system,
A first light receiving system that is provided in the vicinity of the inspection area outside the inside of the disk and receives scattered light from the inspection area ;
A second light receiving system ,
The light beam is a laser beam, which is a spot, the peripheral surface on which the light beam spot is incident is the outer peripheral surface, and the first light receiving system is scattered from the inspection region in the rotating disk. Receive light,
The disk is a glass disk, and the spot is incident on an outer peripheral side surface of the outer peripheral surface,
The second light receiving system has a predetermined offset separation from the position of the outer peripheral side surface symmetrical to the incident position of the spot on the outer peripheral side surface with respect to the diameter line of the disk passing through the inspection region. The scattered light from the inspection area that has propagated inside the disk emitted to the outside is received outside the disk,
The first and second light receiving systems are light receivers having optical fibers, and the light receiving surface of the optical fiber of the first light receiving system is a back surface of the disk for detecting defects in the chamfer of the disk. The light receiving surface of the optical fiber of the second light receiving system is set to face the surface of the chamfer on the side to detect defects on the inner peripheral side surface or the outer peripheral side surface of the disc. A peripheral defect detection optical system of a translucent disc set so as to be substantially perpendicular to the surface of the chamfer on the side. A light beam is incident at a predetermined incident angle on the peripheral surface of the translucent disk to be inspected, and the light beam is transmitted from the inside to the inspection area on the outer peripheral surface or inner peripheral surface of the disk through the inside of the disk. A projection system to irradiate;
A first light receiving system that is provided in the vicinity of the inspection area outside the inside of the disk and receives scattered light from the inspection area;
A driving mechanism for rotating the disk by rotating a spindle on which the disk is mounted;
A detection circuit for detecting a detection signal in the inspection area of the disk by obtaining a detection signal from the first light receiving system while the disk is rotating ;
A second light receiving system,
The light beam is a laser beam as a spot, and the peripheral surface on which the light beam spot is incident is the outer peripheral surface,
The disk is a glass disk, and the spot is incident on an outer peripheral side surface of the outer peripheral surface,
The second light receiving system further includes a predetermined offset separation from a position of the outer peripheral side surface symmetrical to the incident position of the light beam spot on the outer peripheral side surface with respect to the diameter line of the disk passing through the inspection region. The scattered light from the inspection area that has propagated inside the disk emitted to the outside of the disk is received outside the disk,
The light receiving surface of the first light receiving system is set to face the surface of the chamfer on the back side of the disk in order to detect defects in the chamfer of the disk,
The light receiving surface of the second light receiving system is set so as to be substantially perpendicular to the surface of the chamfer on the back surface side of the disc in order to detect defects on the inner peripheral side surface or the outer peripheral side surface of the disc. A peripheral surface defect detection device.

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