JPH05196579A - Inspection device of foreign substance - Google Patents

Abstract

PURPOSE:To facilitate unfailing detection of a foreign substance on a front surface even if the foreign substance sticks to a back side of a glass plate by using a light beam of wavelength not penetrating a glass or of which glass penetration coefficient is rather low, as an irradiation light beam. CONSTITUTION:Existence of a foreign substance on a front side of a glass substrate 3 is detected by irradiating an irradiation light beam 1 to the glass substrate 3 and they by judging whether scattered beam is generated by the foreign object in reflecting beam 2 thereof, or not. A glass usually has a characteristic to be penetrated by light beam of which wavelength is between some 300 to 2570nm. Accordingly, a light beam of wavelength other than the wavelength range said above, is used as the irradiation light beam. Therewith, no scattered beam by a foreign substance sticking to a back sike of the glass substrate 3, is generated, and scattered beam is generated only when a foreign substance exists on a front surface of the glass substrate 3, and therefore just the foreign substance on the front surface of the glass substrate 3 can be detected. It can be said that, as a laser that generates a light beam of wavelength not to penetrate a glass, an excimer laser, a CO2 laser and the like can be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting foreign substances on a surface of a substrate used in a liquid crystal panel manufacturing process or the like.

[0002]

2. Description of the Related Art In recent years, liquid crystal panels have come to receive a great deal of attention, and their manufacturing processes have made rapid progress. But,
At present, the foreign matter inspection in each process is performed by human eyes. Automation of this inspection process is desired for mass production. Currently, as a foreign substance inspection device, a device that performs processing by image recognition is generally used, but high-speed inspection is difficult with this method. Therefore, in order to realize high-speed inspection, development of a foreign substance inspection device by a laser scanning method is also in progress. The principle of foreign matter detection by the laser scanning method will be described below with reference to the drawings.

FIG. 2 shows the principle of detecting a foreign matter defect by the laser scanning method. In the figure,
Reference numeral 5 is irradiation light, and 6 is a foreign substance irradiated by the irradiation light 5. 7 is scattered light obtained by scattering the irradiation light 5 by the foreign matter 6. Reference numeral 8 denotes a glass substrate, on the surface of which foreign matter 6 exists. In this way, the presence of the foreign matter is determined by detecting the scattered light generated by the irradiation of the foreign matter on the foreign matter.
That is, when foreign matter is present on the surface of the glass substrate,
Although scattered light is detected, when no light is present on the surface of the glass substrate, the scattered light is not detected. Therefore, it is possible to determine whether or not a foreign substance is present on the surface of the glass substrate based on the presence or absence of scattered light.

[0004]

However, when a general laser beam is irradiated onto the glass substrate, there is a risk of false detection due to the influence of foreign matter on the back surface. This will be described with reference to FIG. In the figure, 9 is irradiation light, and 12 is a glass substrate to be inspected by irradiation light 9. Reference numeral 10 denotes reflected light obtained by reflecting the irradiation light 9 on the surface of the glass substrate 12. 11
Is the transmitted light that the irradiation light 9 is refracted on the surface of the glass substrate 12 and transmitted through the glass substrate 12. Reference numeral 13 is a foreign substance attached to the back surface of the glass substrate 12, 14 is a scattered light generated by the transmitted light 11 hitting the foreign substance 13, and 15 is a scattered light 14
Appear on the surface of the glass substrate 12. In this way, even if there are no foreign substances on the surface of the glass substrate,
Scattered light due to foreign matter adhering to the back surface may appear on the front surface and be mistakenly detected as a foreign matter on the front surface.

Therefore, it is an object of the present invention to provide an apparatus for surely detecting only the foreign matter on the front surface of the glass substrate even when the foreign matter on the back surface of the glass substrate adheres.

[0006]

The above object is achieved by using, as irradiation light for laser scanning, light having a wavelength that does not pass through glass or light having a wavelength at which glass has a low transmittance. .

[0007]

In the present invention, the light having a wavelength that does not pass through the glass or the light having a wavelength at which the glass has a low transmittance is used as the irradiation light, so that it is erroneously detected due to the influence of foreign matter attached to the back surface of the glass substrate. Only the foreign matter on the surface of the glass substrate can be reliably detected without worry.

FIG. 1 shows this principle. In the figure, 1 is irradiation light, and 3 is a glass substrate to be inspected by irradiation light 1. Reference numeral 2 denotes reflected light obtained by reflecting the irradiation light 1 on the surface of the glass substrate 3. Reference numeral 4 denotes a foreign substance attached to the back surface of the glass substrate 3. Here, as the irradiation light, light having a wavelength that does not pass through the glass or has a low transmittance is used, so that there is no or almost no light transmitted through the glass substrate. Therefore, the scattered light due to the foreign matter attached to the back surface is not generated, and the scattered light is generated only when the foreign matter is present on the front surface of the glass substrate, so that only the foreign matter on the front surface can be detected.

[0009]

[Example] Glass usually has a wavelength of 300 nm to 2570 nm
It has the property of transmitting a certain amount of light. Therefore, light having a wavelength outside this range is used as irradiation light. that way,
Since light does not pass through the glass substrate, it is possible to perform a foreign matter inspection on the surface of the glass substrate without being affected by the back surface.

Excimer lasers, CO ₂ lasers and the like are examples of lasers that emit light of a wavelength that does not pass through glass. These lasers are used as the light source for foreign matter inspection equipment.

Alternatively, white light is dispersed by a diffraction grating or a prism, and light having a wavelength that does not pass through glass is taken out by a slit and used as a light source of a foreign matter inspection apparatus.

An embodiment of this method of the present invention will be described below with reference to the drawings. FIG. 4 shows a method of extracting light of a specific wavelength using a diffraction grating. In the figure, 16 is white light, 17 is a diffraction grating that diffracts the white light 16, 18 is diffracted light diffracted by the diffraction grating 17, and 19 is diffracted light 1.
8 is a diffraction grating that diffracts again, 20 is a diffracted light diffracted by the diffraction grating 19 again, 21 is a slit for extracting light of a specific wavelength from the diffracted light 20, and 22 is a slit of the specific wavelength extracted by the slit 21. Light. As described above, by using the diffraction grating, it is possible to extract light having a desired wavelength from the white light source.

FIG. 5 shows a method of extracting light of a specific wavelength using a prism. In the figure, 23 is white light, 24 is a prism for splitting the white light 23, 25 is light split by the prism 24, 26 is a slit for extracting light of a specific wavelength from the split light 25, 27 Is slit 2
It is the light of the specific wavelength extracted by 6. In this way, by using the prism, it is possible to extract light of a desired wavelength from the white light source.

As described above, the light of the wavelength that does not pass through the glass is extracted from the white light and used as the light source of the foreign matter inspection apparatus.

In the above description, the surface inspection of the glass substrate has been described, but a transparent substrate other than glass is irradiated with light having a wavelength that does not pass through the substrate to perform a foreign substance inspection. Good. In this case as well, the principle is exactly the same.

On the glass substrate, a color filter, electrodes, a protective film, etc. may be placed.

[0017]

As described above, according to the present invention, since the irradiation light does not pass through the glass material, the influence of the back surface does not appear on the front surface. Therefore, even if foreign matter is attached to the back surface of the glass material, it is possible to reliably detect only the foreign matter on the front surface. By using this, a high-speed foreign matter inspection device on the surface of the glass material by the laser scanning method becomes possible.

[Brief description of drawings]

FIG. 1 is a diagram showing a principle of problem solving in the present invention.

FIG. 2 is a diagram showing a principle of foreign matter detection in a conventional example.

FIG. 3 is a diagram showing the principle of problems in the conventional example.

FIG. 4 is a configuration diagram showing a method of extracting light of a specific wavelength according to an embodiment of the present invention.

FIG. 5 is a configuration diagram showing a method of extracting light of a specific wavelength according to an embodiment of the present invention.

[Explanation of symbols]

 1,5,9 Irradiated light 2,10 Reflected light 3,8,12 Glass substrate 4,6,13 Foreign matter 7,14,15 Scattered light 11 Transmitted light 16,23 White light 17,19 Diffraction grating 18,20 Diffracted light 21, 26 Slit 22, 27 Light of specific wavelength 24 Prism 25 Spectral light

Claims (1)

[Claims] 1. A foreign substance inspection device using a laser scanning method, wherein light having a wavelength that does not pass through glass or light having a wavelength at which glass has a low transmittance is used as irradiation light.