JP2016125968A - Check device and method for checking - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a check device capable of highly sensitive defect detection.SOLUTION: The check device has a light projecting unit irradiating a checking target with parallel light, a light receiving unit receiving light of the parallel light which is diffused by defects generated in the testing target, and a checking unit processing a signal obtained in the light receiving unit and checking the defects.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an inspection apparatus and an inspection method for inspecting an object to be inspected.

2. Description of the Related Art Conventionally, a plate-like object to be inspected such as flat glass has been inspected. For example, the presence or absence of defects (such as dents, scratches, foreign objects, bubbles, etc.) and details of the defects (size, number, etc.) are inspected by an inspection device.
Patent Document 1 discloses an inspection method using an optical system (bright field optical system) that detects transmitted light from a light projecting unit. In such a bright field optical system, the contrast between a detection target such as a defect and the background dominates the detection sensitivity.

  Patent Document 2 discloses an inspection method using an optical system (dark field optical system) that detects light scattered from a defect by condensing light from a light projecting unit on a glass surface or inside with a condenser lens. Is disclosed. In such a dark field optical system, light from the light projecting unit is not directly received, but only scattered light scattered by the defect is received.

Japanese Patent Laid-Open No. 2004-117059 JP 2007-24733 A

However, when an inspection is performed with a bright field optical system as shown in Patent Document 1, for example, when the defect is small, there is a problem that the luminance of the background becomes too high and the detection sensitivity of the defect is not sufficient. Although the detection sensitivity can be improved to some extent by using a more sensitive camera as the light receiving part, it cannot be said to be sufficient for detecting a dense cluster of defects of different sizes. . Further, if an expensive high-sensitivity camera is used, the inspection cost is remarkably increased.
As described above, in the bright field optical system, it is difficult to detect the defect dense body with high sensitivity, and thus the size of the defect dense body cannot be measured correctly.

The dark field optical system disclosed in Patent Document 2 can receive only scattered light from a defect, so that a dense defect can be detected with high sensitivity. Patent Document 2 describes a condensing optical system, which employs a complicated optical system to finely adjust the focal point. Therefore, it can be clearly determined whether the detected defect exists inside the glass or the glass surface.
However, since the condensing optical system disclosed in Patent Document 2 is an optical system that condenses on the glass surface or inside by a condensing lens, the region irradiated by the object to be inspected is narrow, and a plurality of defects It is not suitable for testing for the presence or absence at the same time. For this reason, it is difficult to detect a defect cluster in which defects of different sizes are collected, and the size of the defect cluster cannot be measured correctly.

  That is, the conventional technique has a problem that it is difficult to detect with high sensitivity a defect dense body in which defects of different sizes are collected.

  An object of the present invention is to provide an inspection apparatus and an inspection method capable of detecting defects with high sensitivity.

  An inspection apparatus according to the present invention includes a light projecting unit that irradiates parallel light to an object to be inspected, and a light receiving unit that receives light scattered by a defect generated in the object to be inspected by the parallel light irradiated from the light projecting unit. And an inspection unit that inspects defects by processing a signal obtained by the light receiving unit.

  According to the present invention, since the parallel light is used as the light emitted from the light projecting unit, the light scattered by the defect of the inspection object is clearly detected and obtained regardless of the position where the defect occurs. A good quality defect and a non-defective product defect can be distinguished based on the signal. For this reason, a dense defect can be detected with high sensitivity and accurately measured.

In the inspection apparatus of the present invention, the object to be inspected is a plate-like member in which a defect occurs in the surface portion, and the light projecting portion has a light projection optical axis of 90 with respect to a perpendicular perpendicular to the plane of the plate-like member. It is preferable that the light receiving unit is disposed at an angle of less than 0 ° so that the perpendicular of the object to be inspected and the light receiving optical axis coincide with each other.
Since the scattered light reflected by the back surface of the surface to be inspected is not detected by the light receiving unit, the defect images on the surface to be inspected and the back surface are not overlapped and are not measured excessively. Therefore, it is possible to provide an inspection apparatus capable of measuring the defect dense body more accurately. And since the to-be-inspected object is plate-shaped, the inspection apparatus which can be detected even if there are fluctuations in plate thickness or vertical fluctuations can be provided.

In the inspection apparatus of the present invention, the thickness of the object to be inspected is t (mm), and the angle at which the light projecting portion is disposed with respect to the perpendicular to the object to be inspected is θ, where 0 ° <θ <90 ° , When the waveform half-value width of the signal cross section sensed by the light receiving unit is d (mm),
t × sin θ ≦ d / 2
It is preferable to satisfy this relationship.
If it is the range of the said relational expression, the range of the visual field which the light-receiving part in the surface of a to-be-inspected object can detect can be illuminated with the irradiation light from a light projection part.
Therefore, within the range of the relational expression, scattered light from a defect can be detected with sufficient intensity even if there is a fluctuation in plate thickness or vertical fluctuation.

In the inspection apparatus of the present invention, the object to be inspected may have a light-transmitting property, and the light projecting unit may be disposed on one side with respect to the surface of the object to be inspected, and the light receiving unit may be disposed on the other side. .
With this arrangement, since the light projecting unit and the light receiving unit are arranged on the opposite side across the object to be inspected, the light projecting unit and the light receiving unit do not interfere with each other at the installation location. .

In the inspection apparatus of the present invention, both the light projecting unit and the light receiving unit may be arranged on one side with respect to the surface of the object to be inspected.
With this arrangement, since the light projecting unit and the light receiving unit are arranged on the same side with respect to the surface of the object to be inspected, for example, a transport roller is arranged below the object to be inspected. Even if there is no gap, the light projecting unit and the light receiving unit can be installed.
Moreover, although it can test | inspect even if the said to-be-inspected object is a transparent body which has translucency, it is suitable for the test | inspection of the opaque body which does not have translucency.

In the inspection apparatus according to the aspect of the invention, the inspection object has translucency, and the light projecting unit is disposed on one side and the light receiving unit is disposed on the other side of the surface of the inspection object. , The angle θ at which the light projecting unit is installed with respect to the normal of the object to be inspected is
10 ° <θ ≦ 30 °
It is preferable that
The contrast (S / N ratio) of the image from the defect with respect to the background noise is high, and the detection sensitivity to the defect is increased, so that the defect dense body can be detected with higher sensitivity and can be measured more accurately.

In the inspection apparatus of the present invention, the light projecting unit may include a plurality of different types of light sources.
For example, light is irradiated simultaneously from a plurality of light sources having different emission brightness, emission wavelength, and the like. Since the type of defect such as the size of a defect with high detection sensitivity differs for each type of light, various types of defects can be detected simultaneously.

In the inspection apparatus of the present invention, the light projecting unit may be lit in a pulse shape.
For example, by irradiating light of different brightness in a pulsed manner, the effect is the same as irradiating from light sources with substantially different emission brightness, and the size of the defect with high detection sensitivity for each light intensity Since the types are different, various types of defects can be detected simultaneously.
In general, when an optical system using a plurality of different types of light is constructed, a combination of a plurality of light projecting units and a plurality of light receiving units is required. By performing pulsed lighting, only one set of the light projecting unit and the light receiving unit can be provided. As a result, it is possible to avoid interference with the installation location that occurs when a plurality of optical systems are installed, and to reduce costs.

The inspection method of the present invention irradiates the object to be inspected with parallel light from the light projecting unit, and the light received by the light receiving unit receives the light scattered by the defect generated in the object to be inspected by the parallel light irradiated from the light projecting unit. The signal obtained by the light receiving unit is processed by the inspection unit to inspect defects.
According to the inspection method of the present invention, the same effect as that of the inspection apparatus can be obtained. In other words, since the parallel light is used, the light scattered by the defect of the inspection object is clearly detected regardless of the position where the defect occurs, and the obtained signal is processed to determine whether the defect is defective or defective. Can be determined. For this reason, a dense defect can be detected with high sensitivity and measured more accurately.

It is a lineblock diagram of the glass substrate washing line to which the inspection device of a 1st embodiment of the present invention is applied. It is a perspective view which shows the inspection apparatus of 1st Embodiment. (A) is sectional drawing of 1st Embodiment shown in FIG. 2, (B) is the top view seen from the upper side which imaged irradiation light. (A) is a conceptual diagram of a double image generation mechanism, and (B) is an image diagram of the generated double image. It is the graph which showed the experimental result of signal / noise ratio and defect detection sensitivity when changing the installation angle of a light projection part. (A) is a perspective view of an image in which irradiated light is irradiated on a light-transmitting object to be inspected, and (B) shows a luminance distribution in the band width direction (irradiation cross-sectional direction) of the irradiated light and its half-value width. It is a graph. It is an image figure of the detection sensitivity with respect to the plate | board thickness change of the to-be-inspected object which has the zone width and translucency of irradiation light, (A) is a case where a thin board is test | inspected with irradiation light with a wide zone width, (B) is a zone | band. When inspecting a thick plate with irradiation light having a wide width, (C) is for inspecting a thin plate with irradiation light with a narrow band width, and (D) is for inspecting a thick plate with irradiation light with a narrow band width. . It is the figure which showed the experimental result of the detection sensitivity of the defect with respect to the plate | board thickness change of the glass which is a to-be-inspected object. It is the figure which showed the experimental result of the detection sensitivity of the defect with respect to the light quantity irradiated from a light projection part. It is the graph which showed the experimental result of the displacement of a plate pressure direction with respect to the half value width of the luminance distribution of irradiation light, and required light quantity. It is sectional drawing which shows 2nd Embodiment of this invention.

<First Embodiment>
(Outline of the first embodiment)
An example for carrying out the present invention will be described.
First, a first embodiment will be described with reference to FIGS. The inspection apparatus according to the first embodiment is used in a glass substrate cleaning line shown in FIG.
As shown in FIG. 1, in the cleaning line, the glass substrate G that is an object to be inspected is transported by the transport device 1, and is collected and shipped after passing through the cleaning device 2, the draining device 3, and the inspection device 4 in this order. It may be sent to another process before shipment.
The glass substrate G to be inspected in the first embodiment is manufactured by the float process, and then cut into a necessary size and processed as it is or after several processing steps, in the glass substrate cleaning line of FIG. The defect D is inspected by the detection device 4 after being cleaned.

Here, the reason why the defect D (see FIG. 3) occurs in the glass substrate G in the float process will be briefly described.
In a general glass manufacturing process, the necessary type of glass raw material powder is put into a high-temperature glass melting furnace, melted, and homogeneously mixed into a high-temperature viscous fluid (hereinafter sometimes referred to as melt) To. The melt is poured out on molten tin metal (hereinafter sometimes referred to as molten tin). Since the melt, which is a glass precursor prepared by the float process, has a specific gravity sufficiently lower than that of molten tin, the melt floats on the molten tin and spreads wet. By sufficiently spreading and spreading, the melt is formed into a flat plate having a predetermined thickness. A flat glass is obtained by sufficiently cooling and solidifying the melt formed into a flat plate shape. The process so far is called the float method.
The flat glass produced by this float process is flat both on the surface that is in contact with the molten tin and on the surface that is not in contact with anything at the top.

In the above float process, the container filled with molten tin needs to have an atmosphere in which oxygen is exhausted, but even in an atmosphere in which oxygen is exhausted, a slight amount of oxygen cannot be avoided. Tin metal generated in the tin bath and metal vapor mixed as impurities come into contact with oxygen to form fine tin oxide and other metal oxides, which are fixed on the surface of the melt (or glass) with increased viscosity. Things become defects D.
This defect derived from tin oxide (tin oxide defect) is the main defect D to be inspected in the first embodiment. Other defects D include scratches on the glass surface. In addition, a tin oxide defect fixed on a scratch on the glass surface is also conceivable.

The configuration of the inspection apparatus 4 of the first embodiment is shown in FIG.
In FIG. 2, the inspection apparatus 4 is obtained by a light projecting unit 12 that irradiates the parallel light L toward the glass substrate G, a light receiving unit 13 that receives and images light scattered by the defect D, and a light receiving unit 13. And an inspection section 14 for inspecting the defect by processing the received signal. In FIG. 2, in order to make the positions of the light projecting unit 12 and the light receiving unit 13 easier to understand, the position of the glass substrate G is shifted and illustrated.
In the transport device 1, the rotating rollers 1B are arranged at approximately equal intervals between the two rails 1A, and the glass substrate G can be moved by the rotation of the rotating rollers 1B. The interval between the rotating rollers 1B is about 50 mm, and the interval is sufficient to allow the parallel light L to pass between the rotating rollers 1B and perform the inspection.
The light projecting unit 12 has an irradiation width that is sufficiently wider than the width of the glass substrate G with respect to the direction orthogonal to the transport direction F of the transport device 1 (the width direction of the transport device 1).

The plurality of light receiving units 13 are arranged in one row in the width direction of the transport device 1 so that there is no inspection omission in the width direction.
The inspection unit 14 displays an image captured by the light receiving unit 13, and calculates and displays the dimension of the defect D as necessary. The inspection unit 14 immediately determines whether the defect D is a non-defective product defect or a defective product defect by inputting in advance conditions such as the presence / absence of the defect D or the size of the defect D. Can do.
The relationship between the light projecting unit 12 and the light receiving unit 13 is shown in FIG. As shown in the cross-sectional view of FIG. 3A, the transmitted light Lt transmitted through the glass substrate G does not reach the light receiving unit 13, but only the scattered light Ls scattered by the defect D is received by the light receiving unit 13. It is a dark field optical system to be detected. In this dark field optical system, only the scattered light Ls from the defect D forms a bright image where the background is black, and the defect D can be easily detected.

(Detailed configuration of the first embodiment)
The light projecting unit 12 used in the first embodiment is, for example, LED illumination that irradiates parallel light L in a line by arranging high-luminance LED elements as light sources in an irradiation device. The maximum current value is 650 (mA), the maximum power consumption is 750 (W), the width of the illumination area is 600 (mm), and the maximum slit width is 8 (mm).
The light receiving unit 13 used in the first embodiment is, for example, a CCD camera. The resolution is approximately 30 (μm).

FIG. 3A shows a schematic diagram of the optical system of the first embodiment.
In FIG. 3A, the parallel light L emitted from the light projecting unit 12 becomes transmitted light Lt that passes through the glass substrate G and scattered light Ls that is scattered by the defect D. In addition, although the parallel light L is reflected by the back surface and the front surface of the glass substrate G, the reflected light is negligible and is not relevant in this inspection, so the description of the reflected light is omitted here.
The light emitted from the light projecting unit 12 becomes substantially parallel light L in the vicinity of the glass substrate G. The light emitted from the light projecting unit 12 is a light beam that is condensed when viewed from the cross-sectional direction, but since the condensing point of the light beam is sufficiently away from the glass substrate G, the width is near the glass substrate G. The width (hereinafter referred to as the band width M) is, for example, substantially constant in the direction of the thickness t (transmission direction) of the glass substrate G shown in FIG. An image of the band width M with respect to the light projecting unit 12 and the glass substrate G viewed from the light receiving unit 13 is as shown in a plan view viewed from above in FIG.

As shown in FIG. 4A, since the glass substrate G has translucency, when the light receiving unit 13 is arranged so as to deviate from the normal P direction of the glass substrate G, the scattered light Ls of the defect D When the image Da by the light Ls1 partially reflected by the back surface of the glass substrate G is detected by the light receiving unit 13, it may be detected as a virtual image Db on the surface of the glass substrate G. As shown in FIG. 4B, the image of the defect D and the virtual image Db are simultaneously seen and detected as a double image. In this double image, the defect D and the virtual image Db appear to be integrated, and the dimension of the defect D cannot be correctly evaluated. Alternatively, the defect D and the virtual image Db are recognized as different images, and the virtual image Db that does not actually exist is also recognized as a defect, resulting in a decrease in product yield.
In order not to recognize the virtual image Db, it is preferable that the light receiving unit 13 is disposed on the perpendicular P of the glass substrate G. It is difficult to accurately install the light receiving unit 13 on the perpendicular line P without shifting. According to the results of numerous experiments conducted by the inventor of the present invention to the present invention and abundant experience in the past, the arrangement error of the light receiving unit 13 with respect to the normal P direction of the glass substrate G should be within ± 5 °. In this case, it is confirmed that the virtual image Db is not detected.

(Optimization of configuration parameters of the first embodiment)
As shown in FIG. 3A, the light projecting unit 13 is disposed at an angle of less than 90 ° with respect to the perpendicular P of the object to be inspected, and the angle θ is the contrast of the image from the defect D with respect to background noise. (S / N ratio) and detection sensitivity to defects are optimized.
FIG. 5 shows the experimental results of evaluating the S / N ratio and the detection sensitivity when the installation angle of the light projecting unit is changed.
As shown in FIG. 5, the S / N ratio tends to improve as the angle value increases, and 17 ° is the maximum. The detection sensitivity tends to decrease as the angle value increases. The S / N ratio needs to be at least about 0.5, and the installation angle of the light projecting unit 12 is preferably more than 10 ° and not more than 30 °. If the installation angle exceeds 30 °, the detection sensitivity may be significantly reduced. More preferably, the installation angle is more than 10 ° and not more than 20 °, more preferably not less than 13 ° and not more than 17 °.

FIG. 6A shows an image in which the parallel light L emitted from the light projecting unit 12 is applied to the translucent glass substrate G.
In FIG. 6 (A), the light emitted from the light projecting unit 12 is a light beam that collects light, but since the focal point of the light beam is sufficiently away from the glass substrate G, it is substantially near the glass substrate G. Therefore, it becomes parallel light L.
The band width M of the parallel light L is actually unclear, so the length of the band width M cannot be measured visually. Therefore, a means for quantitatively evaluating the band width M without using visual observation is required. That is, the luminance distribution in the irradiation cross section direction is read from the signal obtained by the light receiving unit 13, and as shown in FIG. Hereinafter, it is read as half width).
The half value width d of the luminance is a value proportional to the band width M and can be used as an index of the band width M.

  FIG. 7 shows an image diagram of the detection sensitivity with respect to the band width M of the parallel light L and the thickness change of the glass substrate G having translucency. FIG. 7A shows a case where a thin plate is inspected with a parallel light L having a wide band width M, and FIG. 7B shows a case where a thick plate is inspected with a parallel light L having a wide band width M. ) Shows a case where a thin plate is inspected with a parallel light L having a narrow band width M, and FIG. 7D shows a case where a thick plate is inspected with a parallel light L having a narrow band width M. If the band width M is sufficiently wide, the light receiving unit 13 is sufficient to scatter the scattered light Ls from the defect D regardless of the thickness of the glass substrate G, as shown in FIGS. 7 (A) and 7 (B). Light can be received with high sensitivity. Even when the band width M is narrow, as shown in FIG. 7D, when the glass substrate G is thick, the light receiving unit 13 can receive light with sufficient sensitivity. However, as shown in FIG. 7C, when the glass substrate G is thin, the defect D is not irradiated with a sufficient amount of light, and the light receiving unit 13 cannot receive light with sufficient sensitivity.

In the optical system of the first embodiment shown in FIG. 3A, the light receiving section 13 can receive light with sufficient sensitivity when the band width M satisfies the following conditions. That is, the thickness of the glass substrate G is t (mm), the angle at which the light projecting unit 12 is disposed with respect to the normal P of the glass substrate G is θ, where 0 ° <θ <90 °, and the signal that the light receiving unit 13 senses. When the full width at half maximum of the cross section is d (mm),
t × sin θ ≦ d / 2 (Formula 1)
Satisfy the relationship. Considering the fluctuation value t1 (mm) when the glass substrate G moves up and down during conveyance, t in Equation 1 can be read as (t + t1).

  When the light projecting optical axis of the parallel light L from the light projecting unit 12 and the visual field center line (perpendicular line P) of the light receiving unit 13 intersect at the lower surface (back surface) of the glass substrate G, the surface of the glass substrate G The distance between the point through which the visual field center line of the light receiving unit 13 passes and the light projecting optical axis of the parallel light L from the light projecting unit 12 is the left side (t × sin θ) of Equation 1. (T × sin θ) can be regarded as the maximum deviation between the center line of the light projecting optical axis of the parallel light L and the visual field center line of the light receiving unit 13. If the half value of d indicating the half width of the parallel light L is equal to or greater than (t × sin θ), the parallel light L from the light projecting unit 12 illuminates the range of the visual field that can be detected by the light receiving unit 13. Thus, the defect D can be detected with high sensitivity.

FIG. 8 shows an experimental result of the detection sensitivity of the defect D with respect to a change in the thickness of the glass when the angle θ of the light projecting unit 12 is 15 ° (experimental condition 1).
In FIG. 8, the detection sensitivity of the defect D tends to decrease as the glass plate which is the glass substrate G becomes thicker. However, when the half width is 16.7 (mm) and 9.4 (mm), the glass substrate G The detection sensitivity is almost constant until the thickness is about 1.5 (mm). However, when the half-value width is 6.7 (mm), the detection sensitivity is remarkably lowered, and when the thickness of the glass substrate G is 2 (mm), it is almost halved.

FIG. 9 shows an experimental result of the detection sensitivity of the defect D obtained by the light receiving unit 13 with respect to the amount of the parallel light L emitted from the light projecting unit 12 under the experimental condition 1.
In FIG. 9, the light quantity of the parallel light L emitted from the light projecting unit 12 is proportional to the current value consumed by the light projecting unit 12. As the current value increases, the detection sensitivity for the defect D tends to increase. The detection sensitivity tends to increase as the half-value width decreases.

  FIG. 10 shows the experimental results correlating with the half-width as an index of the band width M in the experimental condition 1 and the detection sensitivity of the glass substrate G at the time of the plate thickness or vertical fluctuation and the magnitude of the amount of light. The detection sensitivity is represented by the ratio of the detection signal intensity of the defect D before and after the height of the glass substrate G is increased by 0.6 (mm), and is 1.0 if there is no change in the signal intensity, and 1 if it is attenuated. The value is less than 0.0. The light quantity index is represented by a current margin, and 1.0 indicates that the light quantity has the most allowance. According to the experimental results, when the half-value width is wide, the detection sensitivity of defects at the time of plate thickness or vertical fluctuation is high, and when the half-value width is narrow, a large amount of light can be provided. Although there is a tendency that the detection sensitivity and the margin of the light quantity are in conflict, it is preferable that the half width is 5 (mm) or more and 20 (mm) or less when the balance between them is balanced. More preferably, they are 5 (mm) or more and 15 (mm), More preferably, they are 6 (mm) or more and 7 (mm) or less. Note that, in the experimental condition 1, all of the experimental values with the full width at half maximum shown in FIG. Here, the current value margin is a value obtained by subtracting “current value necessary for detection” / “maximum current value” from 1, and when “current value necessary for detection is set to a current value, Is a value obtained by subtracting from 1 the value “how much is used compared to the maximum current value”. The current value margin indicates how much current can still flow through the illumination when the current value is set to a value that can provide the sensitivity necessary for detection.

(Effect of 1st Embodiment)
In the first embodiment, the following effects can be achieved.
(1) Since the parallel light L is used as the light emitted from the light projecting unit 12, the scattered light Ls scattered by the defect D of the glass substrate G is clearly detected and obtained regardless of the position where the defect D occurs. The received signal can be processed to discriminate between a non-defective product defect and a non-defective product defect. For this reason, a dense defect can be detected with high sensitivity and measured more accurately.

(2) Since the glass substrate G has translucency, the light projecting unit 12 is disposed on one side of the surface of the glass substrate G, and the light receiving unit 13 is disposed on the other side. The part 13 does not interfere with the installation location.

(3) The light projecting unit 12 is disposed obliquely with a light projecting optical axis of less than 90 ° with respect to the perpendicular P perpendicular to the plane of the glass substrate G, which is a plate-like member, and the light receiving unit 13 includes the perpendicular P and the received light. Since the axes are arranged to coincide with each other, the light receiving unit 13 does not detect the scattered light Ls reflected by the back surface of the surface to be inspected. As a result, the virtual image Db on the surface to be inspected and the back surface do not overlap and are not displayed excessively. Therefore, it is possible to provide the inspection apparatus 4 that can measure the defect dense body more accurately. Moreover, since the glass substrate G is plate-shaped, it is possible to provide an inspection apparatus 4 that can detect even if there is a plate thickness variation or vertical variation.

(4) The thickness of the glass substrate G is t (mm), and the angle at which the light projecting unit 12 is arranged with respect to the perpendicular P of the glass substrate G is θ, where 0 ° <θ <90 °, and the light receiving unit 13 senses. When the full width at half maximum of the signal section is d (mm),
t × sin θ ≦ d / 2 (Formula 1)
Therefore, the parallel light L from the light projecting unit 12 can illuminate the range of the field of view that can be detected by the light receiving unit 13 on the surface of the glass substrate G. Scattered light Ls from the defect can be detected by intensity.

(5) The angle θ at which the light projecting unit 12 is installed with respect to the perpendicular P is
10 ° <θ ≦ 30 °
If so, the contrast (S / N ratio) of the image from the defect to the background noise is high, and the detection sensitivity to the defect is high. For this reason, it is possible to detect defect dense bodies with higher sensitivity and measure them more accurately.

(6) When the angle θ of the light projecting unit 12 is 15 °, if the half width d of the signal section sensed by the light receiving unit 13 is 5 (mm) or more and 20 (mm) or less, the detection sensitivity of the defect D is It is sufficient and a sufficient amount of light (power amount) of the irradiation light source can be provided.

Second Embodiment
A second embodiment of the present invention will be described with reference to FIG. The second embodiment is different from the first embodiment in the arrangement position of the light projecting units, and the other configurations are the same as those of the first embodiment. In the description of the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.
The first embodiment is a transmission optical system in which the light projecting unit 12 is arranged on one side and the light receiving unit 13 is arranged on the other side with respect to the surface of the glass substrate G. As shown by 11, it is constituted by a reflective optical system in which both the light projecting unit 12 and the light receiving unit 13 are arranged on the surface of the glass substrate G.

Also in the optical system of the second embodiment, similarly to the first embodiment, when the band width M satisfies the following conditions, the light receiving unit 13 can receive light with sufficient sensitivity. That is, the height fluctuation value t1 (mm) of the glass substrate G and the angle at which the light projecting unit 12 is arranged with respect to the perpendicular P of the glass substrate G is α, where 0 ° <α <90 ° is a signal sensed by the light receiving unit 13. When the full width at half maximum of the cross section is d (mm),
t1 × sin α ≦ d / 2 (Formula 2)
Satisfy the relationship.
In the reflective optical system of the second embodiment, the thickness t of the glass substrate G does not affect the expression 2.

In the second embodiment, the object to be inspected is not limited to the light-transmitting material such as the glass substrate G, and may be opaque. For example, it is suitable for inspecting the surface of an object to be inspected such as a resin such as metal, ceramics, opaque crystallized glass, and plastic.
In addition, when the to-be-inspected object does not have translucency, reflection by the back surface of to-be-inspected object does not occur, and the virtual image Db of the defect D does not appear. Therefore, the light receiving unit 13 may not be disposed on the perpendicular line P.

(Effect of 2nd Embodiment)
In the second embodiment having such a configuration, the same effects as those of the first embodiment (1), (3), (5), and (6) can be obtained, and the following effects can be obtained.
(7) Since both the light projecting unit 12 and the light receiving unit 13 are arranged on one side with respect to the surface of the glass substrate G, a clearance is provided because, for example, a transport roller is arranged below the glass substrate G. Even if there is no light, the light projecting unit 12 and the light receiving unit 13 can be installed.

(8) Since it is a reflection optical system, defect inspection can be performed even if the object to be inspected is an opaque body that does not have translucency.

(9) When the object to be inspected is an opaque body that does not have translucency, the light receiving portion 13 may not be disposed on the perpendicular line P. Therefore, there is a degree of freedom in the installation position of the light receiving unit 13, and the light projecting unit 12 and the light receiving unit 13 can easily avoid interference at the installation location.

<Modification>
Note that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope in which the object of the present invention can be achieved are included in the present invention.
For example, in each embodiment, the object to be inspected is a glass substrate that is a plate-like material having translucency, and the cleaning line of the glass substrate is illustrated and described, but the present invention is not limited thereto. Absent. For example, the defect D can be inspected by the inspection apparatus 4 of the present invention at least before and after the surface treatment process, polishing process, coating process, and the like.

When the object to be inspected is formed from a translucent material, a material other than glass may be used. As this material, for example, a resin material such as acrylic, a translucent ceramic material, a transparent or translucent (translucent) crystallized glass material, and the like can be considered.
In each embodiment, the object to be inspected has a plate shape, but the present invention is not limited to a plate shape. For example, it is possible to detect a defect D on a bent plate (such as an automobile window glass) or a plate (such as a concave, convex, or wedge shape) whose thickness is not constant.

In each embodiment, it has been described that the defect D is a tin oxide defect, an impurity oxide defect, a scratch on the surface of the object to be inspected, a tin oxide defect fixed on the scratch, or an impurity oxide defect. It is not limited to. Even dust fixed on the surface of the glass substrate G is recognized as a defect D by the inspection device 4.
Moreover, even if it is a bubble or a foreign substance inside the object to be inspected (if the object to be inspected is glass, the raw material remains undissolved or a crystallized material generated during the melting process) is recognized as a defect D by the inspection apparatus 4 Is done.

  In each embodiment, the collimating point of the collimated light L from the light projecting unit 12 is substantially shifted from the object to be inspected so that the collimated lens system is used. It may be parallel light. The collimating lens system can also have a beam expander function, and the width M can be adjusted freely by controlling the beam width of the parallel light L. Alternatively, the band width M may be adjusted by using a single lens and controlling the beam width of the parallel light L passing through the object to be inspected while shifting the focus.

In each embodiment, although LED is used for the light source of the light projection part 12, it does not specifically limit to LED. For example, a high-intensity light source such as a halogen lamp, a mercury lamp, or a xenon lamp, or a laser light source may be used. The emission wavelength of the light source is not limited to visible light. It may be ultraviolet light, near infrared light, or infrared light.
In each embodiment, one type of LED illumination device is used as the light source of the light projecting unit 12, but a plurality of LED illumination devices may be installed. If the input current value, the half width, etc. are changed for each lighting device, different types of defects D can be detected simultaneously.

A plurality of different types of lighting devices may be installed in the light source of the light projecting unit 12. The illuminating device has different emission wavelengths, luminances, and the like, so that different types of defects D can be detected simultaneously.
The light source of the light projecting unit 12 may be turned on in pulses. For example, by irradiating light of different brightness in a pulsed manner, the same effect as that of simultaneously irradiating light of substantially different emission luminance from the light projecting unit 12 can be obtained. Further, by performing pulsed lighting, only one combination of the light projecting unit and the light receiving unit can be achieved. As a result, it is possible to avoid interference with the installation location that occurs when a plurality of optical systems are installed, and to reduce costs.
In each embodiment, the light receiving element of the light receiving unit 13 is a CCD element, but is not particularly limited to a CCD. For example, the light receiving element may be a CMOS.

  The inspection apparatus of the present invention can be used for detecting defects in a glass substrate cleaning line or the like.

12 Light Emitting Part 13 Light Receiving Part G Glass Substrate (Inspected Object)
D defect L parallel light Lt transmitted light Ls scattered light

Claims (9)

A light projecting unit that radiates parallel light onto the object to be inspected;
A light receiving unit that receives light scattered by a defect generated in the object to be inspected by the parallel light emitted from the light projecting unit;
An inspection unit for inspecting defects by processing a signal obtained by the light receiving unit;
An inspection apparatus comprising: The inspection apparatus according to claim 1,
The object to be inspected is a plate-shaped member,
The light projecting portion is disposed obliquely with a light projecting optical axis of less than 90 ° with respect to a perpendicular perpendicular to the plane of the plate-like member,
The inspection apparatus, wherein the light receiving unit is arranged so that a perpendicular line of the object to be inspected and a light receiving optical axis coincide with each other. The inspection apparatus according to claim 2,
The thickness of the object to be inspected is t (mm),
An angle at which the light projecting unit is disposed with respect to the normal of the object to be inspected is θ,
However, 0 ° <θ <90 °,
When the half width of the waveform of the signal section sensed by the light receiving unit is d (mm),
t × sin θ ≦ d / 2
Inspection equipment characterized by satisfying the relationship In the inspection apparatus according to claim 2 or claim 3,
The object to be inspected has translucency,
The light projecting portion is arranged on one side with respect to the surface of the inspection object,
The inspection device is characterized in that the light receiving unit is arranged on the other side. In the inspection apparatus according to claim 2 or claim 3,
Both the light projecting unit and the light receiving unit are arranged on one side with respect to the surface of the object to be inspected. The inspection apparatus according to claim 4,
The angle θ at which the light projecting unit is installed with respect to the normal of the object to be inspected is
10 ° <θ ≦ 30 °
An inspection apparatus characterized by being. In the inspection apparatus according to any one of claims 1 to 6,
The light projecting unit has a plurality of light sources of different types. In the inspection device according to any one of claims 1 to 7,
The light projecting unit is lit in a pulse shape. The object to be inspected is irradiated with parallel light from the light projecting unit,
The light received from the light projecting unit is scattered by a defect generated in the object to be inspected by the light receiving unit,
An inspection method comprising: inspecting a defect by processing a signal obtained by the light receiving unit in an inspection unit.

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