JPH05188004A - Foreign matter detecting device - Google Patents

Abstract

PURPOSE:To detect only foreign matters such as debris attached on the surface of a body to be inspected which is light transmittable and where patterns are formed thereupon, at a high speed and with high accuracy, and simplify the constitution. CONSTITUTION:The light projected from a light-projecting optical system 2 on a body to be inspected 1 at the specified angle. This light is projected on the body to be inspected 1, and is reflected thereby, and a converging optical system 6 is arranged on the side of the internal angle formed by the respective optical paths of the incident light and the regularly reflected light in this condition. Thus, when there is a foreign matter on the surface of the body to be inspected 1, the scattered light caused by this foreign matter is made incident on a photodetector 8 after being converged by the converging optical system 6. This photodetector 8 outputs the electrical signals corresponding to the received light quantity, and a judging means 9 makes a judgement of the existence of the foreign matter from the received light quantity by these electrical signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign matter detecting device for detecting dust adhering to the surface of an object to be inspected having a light transmitting property such as a liquid crystal display panel.

[0002]

2. Description of the Related Art There are various techniques for detecting dust adhering to the surface of a light-transmitting object as described below.

(1) Two light sources are installed, each light emitted from these light sources is irradiated to the object to be inspected, each scattered light by these light irradiation is detected by each light receiver, and the light intensity is compared. A technique for detecting dust by means of the Japanese Patent Laid-Open No. Sho 63-186132.

(2) A plurality of light detecting means are provided, and when the inspection object is irradiated with light from each direction, each light receiver receives the scattered light on the inspection object and compares the received light amounts of these scattered lights. To detect dust (Japanese Patent Laid-Open No. 63-241343).

(3) The angle of incidence and reflection of light with respect to the object to be inspected is set to 90 °, and an optical slit plate is arranged immediately in front of the light receiver for receiving the reflected light. Thereby, a technique of guiding only scattered light generated by dust to a light receiver to detect dust (Japanese Patent Laid-Open No. 2-72248).

(4) Further, as a technique for detecting dust when a pattern is formed on the surface of the object to be inspected, only the irregular signal is extracted by utilizing the regularity of the pattern, and the signal is extracted from this signal. Technology for detecting dust (Japanese Patent Laid-Open No. 61-25344)
No. 8). (5) There is a technique (Japanese Patent Publication No. 1-49222) that utilizes the difference in polarization between reflected light due to a pattern and scattered light due to dust.

However, in each of the above techniques, when detecting only the dust adhering to the liquid crystal display panel on which the pattern is formed, the configuration becomes complicated by disposing a plurality of light receivers. Further, even if the optical slit plate is arranged, it is difficult to receive light from dust with high accuracy.

Further, when a pattern is formed, it is necessary to eliminate the influence of scattered light and diffracted light due to the pattern, and even if this measure is taken, the structure becomes complicated. Therefore, the inspection time is long and the cost of the apparatus is high.

[0009]

As described above, in order to detect dust adhering to the surface of an object to be inspected, which is transparent to light and has a pattern, a plurality of light receivers are arranged. Therefore, the structure becomes complicated, and it is difficult to distinguish the pattern from the dust.

Therefore, the present invention can detect only foreign matters such as dust adhering to the surface of the inspection object on which the pattern is formed, which is transparent to light, at high speed and with high accuracy, and the structure is simple. It is an object of the present invention to provide a foreign matter detection device that can be realized.

[0011]

The present invention provides a light irradiation optical system for irradiating a light-transmissive and patterned object to be inspected with light at a predetermined angle, and a light irradiation optical system. A condensing optical system which is arranged on the inner angle side formed by each optical path of the light incident on the inspection object and the specular reflection light from the inspection object, and detects scattered light generated on the surface of the inspection object, and the condensing optical system. A light receiver that receives the light collected by the optical system and outputs an electrical signal according to the amount of received light, and a judgment that determines the foreign object based on the amount of received light by receiving the electrical signal output from this light receiver And a means for achieving the above object.

[0012]

By providing such means, the light irradiation optical system irradiates the inspection object with light at a predetermined angle.
This light is irradiated onto the object to be inspected and reflected, and in this state, the condensing optical system is arranged on the inner angle side formed by the optical paths of the incident light and the specularly reflected light. As a result, when a foreign substance is present on the surface of the object to be inspected, the scattered light generated by the foreign substance is condensed by the condensing optical system and is incident on the light receiver. The light receiver outputs an electric signal according to the amount of received light, and the determination means receives the electric signal and determines a foreign substance from the magnitude of the amount of received light.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a foreign matter detection device. A light irradiation optical system 2 is arranged obliquely above a liquid crystal display panel 1 as an object to be inspected. The liquid crystal display panel 1 has a light-transmitting property, and a light-transmitting electrode pattern is formed on the surface thereof. Then, the liquid crystal display panel 1 is placed on an XY table (not shown) and moves in the arrow (a) direction at a predetermined moving speed.

The light irradiation optical system 2 has a function of one-dimensionally scanning and irradiating the laser beam L with respect to the liquid crystal display panel 1 at a predetermined angle, for example, an incident angle of 20 ° to 60 °. Explaining a specific configuration, a laser oscillator 3 such as a laser diode is provided, and a polygon mirror 4 is arranged in the laser output direction of the laser oscillator 3.
The polygon mirror 4 rotates in the direction of the arrow at a constant rotation speed to scan the laser beam L one-dimensionally within a constant range. In the scanning line direction of this polygon mirror 4, f · θ
A lens 5 is arranged to form a spot diameter of the laser beam L on the surface of the liquid crystal display panel 1 to have a predetermined size.

On the other hand, just above the irradiation position of the laser beam L on the surface of the liquid crystal display panel 1, a cylindrical lens 6 as a condensing optical system is arranged. The cylindrical lens 6 detects scattered light generated by dust on the surface of the liquid crystal display panel 1.

Further, an optical slit plate 7 and a photoelectric converter 8 such as a photomultiplier are arranged above the cylindrical lens 6. Of these, the optical slit plate 7 is arranged at the image forming point of the cylindrical lens 6, and an optical slit parallel to the scanning direction of the laser beam L is formed.
The photoelectric converter 8 is formed as a one-dimensional sensor parallel to the scanning direction of the laser beam L. A determination circuit 9 is connected to the output terminal of the photoelectric converter 8.

In the judgment circuit 9, a threshold value is set in advance according to the amount of scattered light due to dust, and the threshold value is compared with the electric signal level from the photoelectric converter 8, and when the electric signal level is higher than the threshold value. It has a function of determining that there is dust. Further, this judgment circuit 9 inputs the synchronizing signal from the XY table for moving the liquid crystal display panel 1,
It has a function of detecting the position of dust by inputting an electric signal from the photoelectric converter 8 in synchronization with this synchronization signal. Next, the operation of the device configured as described above will be described.

When the laser beam L is output from the laser oscillator 3, the laser beam L is one-dimensionally scanned by the polygon mirror 4, passes through the f.theta. Lens 5, and is incident on the surface of the liquid crystal display panel 1 in a predetermined manner. Angle 20 ° -60 °
Is illuminated by. At this time, the laser beam L is formed with a predetermined spot diameter on the surface of the liquid crystal display panel 1 by the action of the f · θ lens 5.

When the surface of the liquid crystal display panel 1 is irradiated with the laser beam L in this manner, a specularly reflected laser beam La is generated on the surface of the liquid crystal display panel 1, and scattered light is generated if there is a pattern or dust.

FIG. 2 shows an intensity distribution of diffracted light when the electrode pattern 10 on the surface of the liquid crystal display panel 1 is irradiated with the laser beam L. From this figure, when the edge of the electrode pattern 10 is irradiated with the laser beam L, the regular reflection laser beam La is generated and the scattered light Ls is unevenly distributed along the regular reflection laser beam La.

FIG. 3 shows the intensity distribution of the diffracted light when the dust 11 on the surface of the liquid crystal display panel 1 is irradiated with the laser beam L. From this figure, the laser beam L
When the dust 11 is irradiated with, the specularly reflected laser beam La is generated and the scattered light Lf is generated. The direction of this scattered light Lf is omnidirectional.

On the other hand, since the liquid crystal display panel 1 is light transmissive, the laser beam L passes through the inside of the liquid crystal display panel 1 as shown in FIG.
Reflect on. The reflected laser beam Lr passes through the inside of the liquid crystal display panel 1, is emitted from the surface of the liquid crystal display panel 1, and is condensed by the cylindrical lands 6. However, the light condensing point by the cylindrical lands 6 is located outside the slit of the optical slit plate 7 as shown in FIG. Therefore, the reflected laser beam Lr is blocked by the optical slit plate 7 and does not enter the photoelectric converter 8.

Therefore, the scattered lights Ls and Lf are condensed by the cylindrical lands 6, and enter the photoelectric converter 8 through the optical slit plate 7. The photoelectric converter 8 converts into an electric signal according to the amount of received light and outputs the electric signal, which is sent to the determination circuit 9.

The determination circuit 9 inputs the electric signal from the photoelectric converter 8 in synchronization with the synchronization signal from the XY table, compares the electric signal level with a threshold value, and the electric signal level is higher than the threshold value. In this case, it is determined that there is dust.
The determination circuit 9 also detects the position of the dust 11 from the synchronization signal.

As described above, in the above-described embodiment, the laser beam L is applied to the liquid crystal display panel 1 at a predetermined angle, and the scattered light generated on the surface of the liquid crystal display panel 1 at this time is removed by the cylindrical lens 6. Is collected by the photoelectric converter 8 through the optical slit plate 7,
The electric signal according to the amount of received light is compared with a threshold value to remove dust 1
Since 1 is determined, only foreign matter such as dust 11 that is light-transmissive and has a pattern formed on the surface thereof is attached to the surface of the liquid crystal display panel 1, and the influence of scattered light due to the pattern and the liquid crystal display panel 1 Accurate detection can be performed without being affected by scattered light due to dust on the back surface.
Further, since the liquid crystal display panel 1 is moved in the direction of the arrow (a), the dust 11 on the entire surface of the liquid crystal display panel 1 can be automatically detected.

Since only one laser oscillator 3 is required and it is composed of the cylindrical lens 6, the optical slit plate 7 and the photoelectric converter 8, the structure of the optical system is simple. Further, since the determination circuit 9 only needs to compare the threshold value and the electric signal, it can be realized with a simple circuit configuration. The present invention is not limited to the above-mentioned embodiment, and may be modified within the scope of the invention.

For example, the optical system including the cylindrical lens 6, the optical slit plate 7 and the photoelectric converter 8 is arranged at any position on the inside angle formed by the optical paths of the laser beam L and the regular reflection laser beam La. You may.

The light irradiation optical system 2 does not scan the laser beam L but emits linear light into the liquid crystal display panel 1.
The surface may be irradiated with light, and a galvano mirror may be used instead of the polygon mirror 4.

The photoelectric converter 8 may have a one-dimensional light receiving surface, and for example, the optical slit plate 7 may be omitted and a plurality of optical fibers may be arranged in a line. Alternatively, a CCD line sensor may be used.

Further, the light irradiation optical system 2 irradiates the liquid crystal display panel 1 without scanning the laser beam L, and in this state, the liquid crystal display panel 1 is moved to the XY table by the X-axis.
The laser beam L may be scanned by moving it on the Y plane. Further, the cylindrical lens 6 may be replaced with a selfoc array.

[0032]

As described above in detail, according to the present invention, only foreign matters such as dust adhering to the surface of the object to be inspected, which is light-transmissive and has a pattern formed thereon, can be processed at high speed and with high accuracy. Therefore, it is possible to provide a foreign matter detection device that can detect a foreign matter and that has a simple configuration.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a foreign matter detection device according to the present invention.

FIG. 2 is an intensity distribution diagram of diffracted light generated in an electrode pattern of a liquid crystal display panel.

FIG. 3 is an intensity distribution diagram of diffracted light generated in dust on a liquid crystal display panel.

FIG. 4 is a schematic diagram showing an optical path of a reflected laser beam from the back surface of the liquid crystal display panel.

[Explanation of symbols]

1 ... Liquid crystal display panel, 2 ... Light irradiation optical system, 3 ...
Laser oscillator, 4 ... Polycon mirror, 5 ... f.theta. Lens, 6 ... Cylindrical lens, 7 ... Optical slit plate, 8
Photoelectric converter, 9 ... Judgment circuit.

Claims (1)

[Claims] 1. A light irradiation optical system for irradiating a light-transmissive object having a pattern formed on its surface with light at a predetermined angle, and the light irradiation optical system to enter the object to be inspected. A condensing optical system which is arranged on the inner angle side formed by each optical path of light and specularly reflected light from the inspected object and detects scattered light generated on the surface of the inspected object, and this condensing optical system. A light receiver that receives the light collected by the sensor and outputs an electric signal according to the amount of the received light, and a judgment that determines the foreign substance based on the amount of the received light by receiving the electric signal output from the light receiver And a means for detecting foreign matter.