JPH0495861A - Detector of defect of transparent circular work - Google Patents

Abstract

PURPOSE:To distinguish among an inner defect, a surface particle and a surface crack by making a light beam incident in a direction of a diameter from both inner and outer peripheral faces, receiving scattered components in a direction closely perpendicular to a surface and in addition scanning the surface in the direction of the diameter to respectively receive components close to regular reflection light and components close to the scattered light. CONSTITUTION:A circular work 1 is captured by four rollers 4 along an outer circumference and rotated with the center of the circle as a rotation axis. A projected 2 laser beam P1 is emitted toward a mirror 11 placed at the center of the work 1, enters from an inner peripheral face from an inner part toward an outer part along a direction of a radius, and scattered components are received 3 in a direction closely perpendicular to a surface. A projected 5 laser beam P3 scans on the surface along a direction of a diameter, while components close to regular reflection light at the time of reflection are received 6 and components close to scattered light are similarly received 7. Then the received 3, 6, 7 components are supplied from a defect distinguishing unit 8 from a defect identifying unit 9, where distinction among an inner defect, a surface particle and a surface crack is made, allowing correct detection.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention relates to a defect inspection device for a transparent circular workpiece made of glass or plastic that serves as a substrate for a ceramic disk, an optical disk, a magneto-optical disk, etc. In particular, it relates to a technique for detecting defects by type.

(Prior art) In defect inspection of transparent circular workpieces (transparent disks) that serve as substrates for high-density information recording media, inspection is performed depending on the location of the defect (front or inside, front or rear surface), and the type of defect. It is necessary to judge whether the product is good or defective depending on whether it is a surface flaw or a particle.

That is, internal defects such as bubbles and particles that can be removed by cleaning are not fatal and may not cause any problem in terms of substrate quality.

Japanese Patent Publication No. 63-9177 and Japanese Patent Application Laid-open No. 1-260348 are known as defect inspection devices for such transparent glass disks, etc.
As shown in the issue, a laser beam is irradiated perpendicularly to the glass surface, and two types of light receiving systems are installed to receive the reflected light, one focused on each defect on the front and back surfaces. A method has been proposed to distinguish between the front side and the back side based on the level difference of each signal. This method is shown in FIG. In the figure, 1 is a transparent circular workpiece, Pi is a laser beam irradiated perpendicularly to the workpiece 1, 40 is a light receiver focused on the workpiece surface, and 41 is a light receiver focused on the backside of the workpiece.

In both cases, the focal point of the light receiving system is placed on the target surface, a spatial filter is placed on the light receiving and imaging surface, and signal components from the non-focal surface are suppressed to differentiate the front and back surfaces based on the difference in level of detection signals. It is.

(Problem to be Solved by the Invention) Transparent glass disks may contain bubbles and foreign matter inside as well as on the surface, and when these exist, it is difficult to distinguish between internal defects and back surface defects. Not only that, but the defect is determined to be an internal defect that can be considered a non-defective product. Similarly, it is difficult to distinguish between particles that are good products and surface flaws that are bad products. The reason for this is that, as shown in FIG. 4, the intensity distribution of the reflected light at each defective portion is similar, making it difficult to obtain a sufficiently significant difference in each signal level.

Furthermore, in these surface defect inspection apparatuses, the defects to be detected are extremely small, on the order of a micrometer, and the measurement resolution must be at this level. However, improving resolution and shortening inspection time are contradictory factors, and conventional devices have not been able to achieve a satisfactory result.

The purpose of the present invention is to provide an inspection device that can classify harmless defects such as internal defects and particles and surface defects that are harmful defects on transparent circular workpieces (mainly glass disks, etc.), and can inspect the entire surface at high speed. It's about doing.

[Structure of the Invention (Means for Solving the Problems and Their Functions) The basic structure and functions of the defect inspection apparatus for transparent circular workpieces according to the present invention will be explained with reference to FIGS. 2 and 3. As shown in FIG. 3, a laser beam P having a beam center on the outer or inner radius of the circular workpiece 1 and having a uniform energy density,
1 is continuously irradiated. If there is a defect inside the transparent body as shown in FIGS. 3(a 1) and (a 2), light is diffused at the defective portion. When the scanning phosphor Rλ1 is placed in the normal direction of the surface and scanned on the radial axis, it captures the diffused light at the defective area and becomes an internal defect signal as shown in (a) in Figure 2 (a), indicating that there is no defect. It is possible to obtain a signal with a very high signal-to-noise ratio.

On the other hand, the laser beam P,3 is projected at a projection angle of θ1 with respect to the surface normal.
irradiate.

This beam scans on the same radial axis as the continuous irradiation P,1. (Indicated by ■ in Figure 3).

At least two light receivers are arranged for the scanning type projector P,3. One is a receiver R, 3, with an incident angle of θ1-θ2.
3, and the other is 1θ, −θ31=600 receiver R,
Place 3,3.

The amount of light received by the R13#2 receiver may be 2nd due to dirt or scratches on the surface.
The amount of received light decreases as shown in (C) and (e) in Figure (A), but if there is a back surface defect or an internal defect, the amount of received light increases as shown in (A) (a) and (d). Defects on the front and back sides can be determined from this increase/decrease state. For this purpose, see Figure 3(e).
As shown in , it is necessary to suppress the component of reflected light from the defect-free back surface as much as possible.

Furthermore, in the other photoreceiver Rλ3θ3, 1θ1-θ31 is set at about 60° in order to create a light receiving system that is highly sensitive to convex defects such as surface particles, as shown in Figure 3 (
For particle defects like b),
As shown in b), it is possible to obtain very high-level signals.

If the scans of the scanning fluorescent lamp R11 and the scanning projector Pi3 are synchronized, a signal as shown in FIG. 2 will be obtained, and internal defects and surface defects, as well as surface defects and back surface defects, can be detected separately.

(Embodiment) FIG. 1 shows a schematic configuration of a defect inspection apparatus according to an embodiment of the present invention.

A transparent glass disk (circular workpiece) 1 is gripped at its outer periphery by four rollers 4 and rotated about a rotating shaft at the center of the circle.

A light projector 2, which is a light source for an internal defect detection system, is placed below the center of the workpiece 1, and irradiates laser beams P and 1 toward a reflecting mirror 11 placed at the center of the workpiece 1. The laser beam P is reflected by the mirror 11, becomes parallel to the workpiece 1, enters the transparent body of the workpiece 1 from the inner peripheral surface of the workpiece 1, and heads from the inside to the outside in the radial direction of the workpiece 1. A scanning phosphor 3 is placed above the path of the laser beams P, 1 in the weave, and the scanning phosphor 3 detects the light diffused by the internal defects of the laser beams P, 1.

On the other hand, the beam scanning position of the scanning type projector 5 is scanned at the same position as the internal defect detection laser beams P and 1. This laser beam is received by a light receiver 6 and a scattered component light receiver 7 on the regular reflection optical axis, which are set at an angle θ2 that is approximately the same as the incident angle θ1. The light receiving angle θ3 of this light receiver 7 is placed at a position sufficiently apart from θ2, and the light receiver 7 is arranged so that a high amount of light can be obtained from the diffused light component.

The outputs of these three photoreceivers 3.6.7 are supplied to the defect discrimination section 8. In the defect discrimination section 8, the internal defect signal is discriminated by comparing the output of the light receiver 3 at a predetermined level,
In addition, the surface defect signal is discriminated by comparing the signals in the bright direction of the output of the light receiver 6 at a predetermined level, and the light receiver 7
Particle defect signals are discriminated by comparing the outputs of the two at predetermined levels.

The three systems of defect signals (pulse signals) described above are sent to the defect determination section 9.
is supplied to Further, a rotation synchronization signal from the rotation sensor 10 is also input to the determination section 9 . In the defect determination section 9, upon receiving the three types of defect pulse signals described above, the defect determination unit 9 stores the defect by type in a memory having an address corresponding to each area as information for each unit area divided in the radial direction and rotational direction of the workpiece 1. The presence or absence of is memorized. Once the entire surface of workpiece 1 has been inspected, the information in the memory is read out to determine the presence or absence of defects.
Displays the type of defect and the location of the defect. Furthermore, the quality of the workpiece 1 is determined and output based on the type and amount of defects. In this determination section 9, when the signals overlap at the same address, the signal corresponding to the type of defect is preferentially left among the signals from each photoreceiver.

The transparent glass disk inspection apparatus constructed in this manner constitutes an independent detection system for internal defects and surface defects, and therefore has a high degree of freedom in determining the type of defects, and is extremely useful industrially.

In order to speed up the inspection time, by arranging the above-mentioned configuration in another system on the diameter, the inspection time can be shortened to 1/2. At this time, another light emitter 2a for detecting the internal defect may be used to emit light from the opposite direction to the light emitter 2 as shown in FIG. 1, and the light diffused by the internal defect may be received by the light receiver 3a.

Another detection system corresponding to the scanning optical device 5 is omitted from the figure.

Furthermore, in order to reduce costs, it is possible to share the light receiver 3 and the light receiver 7, in which case the wavelength λ1 (λ
2) and λ3 are light sources of the same wavelength, and the scanning fluorescent device 3 receives the superimposed light.

At this time, make a difference in the irradiation power of P□3 and Pil (P
13>>Pit) and provide separate discrimination levels for internal defects and particle defects as shown in FIGS. 1 and 2, the same effect as in the previous embodiment can be expected.

[Effects of the Invention] As explained in detail above, the defect inspection device of the present invention has high independence of the internal defect detection system, the front and back surface defect detection system, and the particle defect detection system, so it is possible to detect defects in transparent circular workpieces. The classification ability is significantly improved compared to conventional devices, and it is possible to distinguish between harmful and non-hazardous defects with high reliability. Therefore, only truly defective products can be accurately detected.
It is extremely effective not only in improving product yield but also in controlling process quality.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a defect inspection device according to an embodiment of the present invention, and FIG. 2 is a waveform diagram showing signal processing of the device of the present invention.
FIG. 3 is an explanatory diagram of the inspection principle of the apparatus of the present invention, '! ! ! 4
FIG. 4 is an explanatory diagram of the inspection principle showing the problems of the conventional device. DESCRIPTION OF SYMBOLS 1... Transparent circular workpiece, 2.2a... First emitter, 3.3a... First light receiver, 4... Rotating roller, 5... Second emitter, 6. ...Second light receiver, 7.Third light receiver, 8.Defect discriminator, 9.Defect discriminator, 10.Rotation sensor, 11.Reflection mirror FIG.

Claims (11)

[Claims] (1) means for rotating a transparent circular workpiece around the center of the circle; a first projector that makes a light beam enter the circular workpiece in the radial direction of the circle from the inner circumferential surface or outer circumferential surface of the circular workpiece; a first scanning light receiver that receives components of the light beam from the light projector that are scattered at the defective portion in a direction close to perpendicular to the surface of the circular work; and a defect signal is discriminated from the output of the first scanning light receiver. a first defect discriminator that scans the surface of the circular work with a light beam in the radial direction; and a second light projector that scans the surface of the circular workpiece with a light beam; a second light receiver that receives a component close to reflected light; a third light receiver that receives a component close to scattered light when the light beam from the second projector is reflected on the surface of the circular workpiece; a second defect discriminator that discriminates a defect signal from the output of the second photoreceiver; a third defect discriminator that discriminates the defect signal from the output of the third photoreceiver; A defect inspection device for a transparent circular workpiece, comprising a defect determination section that receives an output from the defect discrimination section and identifies whether it is an internal defect, a surface particle, or a surface flaw. (2) A defect inspection apparatus for transparent circular workpieces according to claim 1, wherein the wavelengths of the first light projector and the second light projector are different to such an extent that they can be detected separately by the light receiving system. (3) A defect inspection apparatus for a transparent circular workpiece according to claim 1, wherein the scanning position of the light beam of the first projector and the scanning position of the second projector are substantially the same and in the same direction. (4) In the configuration according to claim 1, the first defect discriminating section discriminates the internal defect signal by comparing the output of the first light receiver at a predetermined level. Inspection equipment. (5) In the structure of claim 1, the second defect discriminating section discriminates the surface defect signal by comparing the signals in the bright region direction of the output of the second light receiver at a predetermined level. Defect inspection equipment for transparent circular workpieces. (6) In the configuration according to claim 1, the third defect discriminating section discriminates the particle defect signal by comparing the output of the third light receiver at a predetermined level. Inspection equipment. (7) In the structure of claim 1, there are two pairs of a first light emitter and a first light receiver, each of which shares half of the diameter line of the circular work. Workpiece defect inspection device. (8) In the configuration of claim 1, the incident angle θ_1 of the second projector and the solid angle of reception w of the second light receiver are such that θ_1 is large and w is small so that the back reflection component is included. Features: Defect inspection equipment for transparent circular workpieces. (9) A defect inspection apparatus for a transparent circular workpiece according to claim 1, wherein the first light receiver and the third light receiver are a common light receiver. (10) In the configuration according to claim 1, the defect determining section:
A defect inspection apparatus for a transparent circular workpiece, characterized in that the presence or absence of a defect and the type of defect are determined and displayed for a unit area in a rotational direction and a radial direction of the circular workpiece. (11) The defect inspection apparatus for a transparent circular workpiece according to claim 1, wherein the defect determining section determines the quality of the circular workpiece based on the type and amount of defects.