JPH09179043A - Variable dimming method of positioning optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously dim reflected light from one of two kinds of substrate when the substrate is larger in reflection factor. SOLUTION: The illumination light LT of a light source 61 is random polarized light; and a 1st polarizing plate 67 which is variable in angle of polarization is inserted between the light source 61 and both the substrates 1 and 2 and a 2nd polarizing plate 68 which has its angle of polarization set to one direction is inserted between both the substrates and a CCD camera 65. When one of the substrates 1 and 2 is larger in reflection factor and the image signal of the CCD camera 65 is saturated with its reflected light, the angle of polarization of the illumination light LT is adjusted by the rotation of the angle of polarization of the 1st polarizing plate 67 to adequately dim the reflected light transmitted through the 2nd polarizing plate 68. Therefore, the saturation of the CCD camera 65 is prevented to a precisely position both the substrates 1 and 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable dimming method for continuously dimming illumination light of an alignment optical system for two types of substrates which are superposed.

[0002]

2. Description of the Related Art A color filter (substrate) and a TFT substrate, which are constituent elements of an LCD (liquid crystal panel), will be described as examples of two types of substrates to which the present invention is applied. FIG. 2 shows a color filter substrate 1 and a TFT substrate 2. In FIG. 2 (a), the substrate 1 is a rectangular glass substrate on which a large number of minute color pixels are arranged in a matrix, and the two surrounding pixels are opposed to each other.
Alignment marks (hereinafter simply marks) M _C1 and M _C2 are arranged in the corners. In the substrate 2, TFT elements corresponding to each color pixel are arranged on the surface of the glass substrate, and the marks M _C1 and M _C2 corresponding to the above marks M _C1 and M _C2 are provided in the two corners around the TFT elements.
_T1 and M _T2 are arranged. Both marks M _C and M _T are, for example, square as shown in the drawing, and M _T is made smaller than Mc. As shown in (b), these substrates 1 and 2 are aligned by superposing them with a minute gap G, and then fixing four sides by a sealant S to put LC (liquid crystal) in the gap G. Injected and used for color LCD panel.

FIG. 3 shows the structure of a superposing device 10 for both substrates 1 and 2, and its operation will be described below. In FIG. 3, the TFT substrate 2 is positioned and adsorbed on the upper surface of the lower stage 4 by the positioning tools 41a to 41d provided at the four corners thereof, and the color filter substrate 1 is adhered to the lower surface of the upper stage 5 as described above. Is positioned and adsorbed. The sealant S is applied to the four sides of both substrates 1 and 2, and the upper stage 5
Is lowered to superpose the substrate 1 on the substrate 2 and temporarily fixed.
In this temporary fixing, the corresponding marks M _C and M _T are
As in (a), the state is intentionally separated by a minute distance Δx in the X direction. Round holes 51a and 51b at the two corners of the upper stage 5
And two sets of alignment optical systems 6 (A) and 6 (B) are provided on the top of each.

FIG. 4 shows both alignment optical systems 6 (A) and (B).
Is shown. The illumination light L _T from the light source 61 is collimated by the illumination lens system 62, reflected by the half mirror 63, passes through the round holes 51a, 51b, and the marks (M _C1 , M _T1 ).
And the marks (M _C2 , M _T2 ) are illuminated, each image is magnified by the objective lens 64, captured by the CCD camera 65, and each image signal is output. In FIG. 3 again, the image signal of the CCD camera 65 of the alignment optical system 6 (A) is processed by the image processing circuit 71 of the image processing section 7, and the XY coordinates of the center O of M _C1 shown in (a) are shown. (X ₁ , y ₁ )
And the XY coordinates (x ₁ ', y ₁ ') of the center _O'of M _T1 are calculated, the image signal of the alignment optical system 6 (B) is also processed, and the XY coordinate of the center O of M _C2 is calculated. and _{(x 2, y 2),} 'XY coordinates (x _2' center O of M _T1, y ₂ ') and is calculated. These four sets of XY coordinate values are passed to the control circuit 72, and the control mechanism outputs the control signal to operate the moving mechanism 3 to move the substrate 2 in X or Y, or rotate by θ to rotate the marks M _C1 and M.
_T1 and the marks M _C2 and M _T2 are respectively aligned, and when this is completed, both substrates 1 and 2 are permanently fixed by the sealant S.

[0005]

The reflectances on the surfaces of the above-mentioned substrates 1 and 2 may differ greatly from each other. Initially, both marks M _C and M _T were made of ITO (Indium Tin Oxide) as a material and were deposited on the surface of a glass substrate, and both reflectivity was the same, but recently, Since metal such as aluminum or chrome is used for the material of the mark M _T , and a protective film is further coated thereon, the TFT substrate 1 has a large reflectance,
Since this enters the CCD camera 66 and the image signal of the mark M _T is saturated, it becomes difficult to calculate the coordinate values. Therefore, in order to prevent the saturation of the image signal, as shown in FIG. 4, conventionally, an attenuation filter 66 is inserted between the illumination lens system 62 and the half mirror 63 to reduce the illumination light L _T, and Saturation is prevented. However, since the reflectance of the substrate 1 greatly changes depending on the type of the material metal of the mark M _{T and} the material of the protective film, the neutral density filter 66 is provided with several different levels of neutral density. The method of replacing the substrate 1 with a suitable one and using it is adopted. However,
With this method, replacement of the neutral density filter 66 is troublesome,
In addition, there is a drawback in that it is not possible to finely adjust the light amount in the middle by gradually reducing the light amount. This invention, by simple means,
The reflected light from the substrate with a high reflectance is continuously dimmed, and CC
An object is to prevent saturation of the image signal of the D camera.

[0006]

SUMMARY OF THE INVENTION The present invention is a variable dimming method for an alignment optical system which solves the above-mentioned problems, in which illumination light of a light source is randomly polarized light and is inserted between the light source and both substrates. There is provided a first polarizing plate having a rotatable polarization angle and a second polarizing plate inserted between both substrates and the CCD camera and having the polarization angle set in a fixed direction. When the reflectance of one of the two substrates is large and the image signal of the CCD camera is saturated by the reflected light, the polarization angle of the illumination light is adjusted by rotating the polarization angle of the first polarization plate, and the second polarization plate is adjusted. This reflected light that passes through is attenuated to prevent saturation of the image signal.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the above variable dimming method,
Since the polarization angle of the first polarizing plate inserted between the light source and both substrates is rotatable, the polarization angle of randomly polarized illumination light can be continuously changed. On the other hand, since the polarization angle of the second polarizing plate inserted between both substrates and the CCD camera is set to a fixed direction, the polarization angle of the first polarizing plate can be changed by rotating the polarization angle of the first polarizing plate. When the light reflected by the substrate having a high reflectance is transmitted through the second polarizing plate, the amount of the transmitted light continuously changes according to the difference in the polarization angle between the first and second polarizing plates. The light is dimmed to prevent saturation of the image signal of the CCD camera.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the construction of an embodiment of an alignment optical system 6 to which the variable dimming method of the present invention is applied. In FIG. 1, the alignment optical system 6 includes a neutral density filter 66 shown in FIG.
Instead of the first polarizing plate 67, the objective lens
A second polarizing plate 68 is inserted between 64 and the CCD camera 65. The first polarizing plate 67 is housed in a suitable holder 671,
The handle 672 is rotated as shown by arrow C so that the polarization angle can be continuously changed. The second polarizing plate 68 sets the polarization angle in a fixed direction.

With the above construction, the illumination light L _T of the light source 61 is randomly polarized, and the first polarization plate 67 selects the polarization component corresponding to the polarization component through the illumination lens system 62, and the half mirror 63 is selected. The first and second substrates 1 and 2 are reflected by the second polarizing plate 68 through the objective lens 64, and the reflected light is continuously dimmed according to the difference in polarization angle between the polarizing plates 67 and 68. It is input to the CCD camera. If the reflectance of the substrate 2 is now high, the handle 671
By rotating the polarization angle of the polarizing plate 67 of the second polarizing plate 68 and adjusting the dimming amount of the second polarizing plate 68, the mark M _T of the CCD camera 65
Is prevented from being saturated. As a result, the coordinate values of the centers O and O'of both marks M _C and M _T are correctly calculated by the image processing circuit 71, and the positioning of these by the moving mechanism 3 is accurately performed.

Although the above-described embodiment is directed to the color filter substrate 1 and the TFT substrate 2, it is needless to say that it can be applied to the alignment of any two kinds of substrates other than this, which have a large difference in reflectance. .

[0011]

As described above, in the variable dimming method according to the present invention, when the light reflected by the substrate having a large reflectance is transmitted through the second polarizing plate by simply rotating the first polarizing plate. The amount of transmitted light is appropriately dimmed to prevent saturation of the image signal of the CCD camera, so that the coordinate values of the alignment marks of both substrates are calculated correctly, and the effect of accurate alignment is There is a big one.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of an alignment optical system for a color filter and a TFT substrate in an LCD panel to which the present invention is applied.

2A and 2B are explanatory views of a color filter substrate and a TFT substrate, FIG. 2A is a plan view showing a configuration of both substrates, and FIG. 2B is a cross-sectional view in which both substrates are superposed.

FIG. 3 is a configuration diagram of a superposing device for both substrates.

FIG. 4 is a configuration diagram of an alignment optical system for a color filter and a TFT substrate in a conventional LCD panel.

[Explanation of symbols]

1 ... Color filter substrate, 2 ... TFT substrate, 3 ... Moving mechanism, 4 ... Lower stage, 5 ... Upper stage, 51a, 51b ... Round hole, 6, 6 (A), 6 (B) ... Positioning optical system, 61 ... Light source, 62 ... Illumination lens system, 63 ... Half mirror, 64 ... Objective lens, 65 ... CCD camera, 66 ... Dark filter, 67 ... First
Polarizer, 671 ... Holder, 672 ... Handle, 68 ... Second
Polarizing plate, M _C , M _T ... Alignment mark, S ... Sealing agent,
L _T ... Illumination light.

Claims (1)

[Claims] 1. Positioning in which two types of substrates are superposed, and alignment marks which are respectively provided on both substrates and are separated from each other by a minute distance are irradiated with illumination light from a light source and imaged by a CCD camera. In the optical system, the illumination light is randomly polarized light, is inserted between the light source and both substrates, and is inserted between the first polarizing plate having a rotatable polarization angle, the both substrates and the CCD camera, A second polarizing plate whose polarization angle is set in a fixed direction is provided, and when the reflectance of one of the substrates is high and the reflected light saturates the image signal of the CCD camera, the first polarized light The polarization angle of the illumination light is adjusted by rotating the polarization angle of the plate to reduce the amount of the reflected light that passes through the second polarizing plate and prevent saturation of the image signal. Variable dimming method for alignment optical system.