JP2003035613A - Residual stress inspection device for light pervious substance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a residual stress inspection device for a light pervious substance dispensing with the rotation of an analyzer and capable of inspecting residual stress at a high speed. SOLUTION: Red, green and blue linearly polarized lights, which are passed through three polarizers 27, 28 and 29 arranged in different polarizing directions, are transmitted through an object 32 to be inspected and the analyzer 30. These red, green and blue lights are detected by a color CCD camera 31 and the polarizing characteristics of the object 32 to be inspected are calculated from the intensities of the respective color lights.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a residual stress inspection device for a light transmissive substance. For example, the present invention relates to a residual stress inspection device for detecting residual stress and unevenness of the residual stress existing in an optical component such as a glass substrate or a transparent resin plate used for a liquid crystal display or the like.

[0002]

2. Description of the Related Art In the manufacturing process of glass substrates used for liquid crystal displays and light guide plates, resin molded transparent bodies, etc., various physical properties are measured in order to know the quality of the materials and processing. One is the measurement of residual stress. If the transparent body has residual stress, birefringence occurs when light is transmitted, which causes uneven brightness. Therefore, in these manufacturing processes, residual stress of the product is measured.

As an apparatus for inspecting residual stress, an inspecting apparatus using a rotary analyzer method for detecting a change in polarization state has been conventionally known. FIG. 1 is a diagram showing a configuration of an inspection device using such a rotation analyzer method. In this inspection apparatus 1, a polarizer 3 is placed in front of a monochromatic light source 2, an object 4 to be inspected is placed on the optical path in front of it, an analyzer 5 is placed in front of it, and a CCD is placed in front of it. A camera 6 is arranged. The inspected object 4 is arranged so that the direction of its birefringence is turned by 45 ° with respect to the polarization direction of the polarizer 3, and the analyzer 5 is rotated by the rotation driving means 7 at a predetermined rotation speed. It has been rotated.

The rotation driving means 7 for rotating the analyzer 5 is
By outputting a constant pulse drive signal from the control unit 8 to the pulse step motor 9, the pulse step motor 9 is rotated at a constant speed, and the pulse step motor 9 rotates the analyzer 5 at a constant rotation speed via the transmission mechanism 10. I am letting you. On the other hand, the encoder 11 detects the rotation angle of the analyzer 5. The CCD camera 6 detects the intensity of light emitted from the monochromatic light source 2 and passing through the polarizer 3, the inspection object 4, and the analyzer 5.

The monochromatic light emitted from the monochromatic light source 2 passes through the polarizer 3, is converted into linearly polarized light parallel to the polarization direction of the polarizer 3, and then passes through the inspection object 4. Here, when residual stress is generated in the inspection object 4 and light transmitted through the inspection object 4 undergoes birefringence, the inspection object 4
The light transmitted through is generally elliptically polarized light. Therefore, when the polarization direction of the analyzer 5 for transmitting the elliptically polarized light is rotated around the optical axis, the intensity of light detected by the CCD camera 6 draws a sine curve as shown in FIG. Change. In FIG. 2, Imax is the maximum value of the light intensity when the analyzer 5 is rotated, Imin is the minimum value of the light intensity when the analyzer 5 is rotated, and ψ is the polarization angle of the inspection object 4.

[0006]

However, in the conventional residual stress inspection apparatus by the rotary analyzer method, the analyzer is attached to the rotation driving means so that the analyzer can be rotated, and the analyzer is rotated at least 180 ° to obtain the light intensity. Need to detect changes. That is, by simply transmitting the elliptically polarized light to the analyzer, the birefringence direction (that is, the directions of the fast axis and the slow axis) and the birefringence amount (that is, the electric field of the light wave changes the fast axis direction) of the inspection object. Since it is not possible to simultaneously measure the phase difference between the transmitted light that is directed and the transmitted light that is directed in the slow axis direction, it is necessary to rotate the analyzer in order to measure them simultaneously. Therefore, there is a problem that it takes a long time to inspect the residual stress.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the technical problems of the above-described conventional examples, and an object thereof is to perform residual stress inspection at high speed without the need to rotate an analyzer. An object of the present invention is to provide a residual stress inspection device for a light transmissive material.

The residual stress inspecting device for a light transmitting material according to the present invention transmits the polarized light emitted from the polarized light irradiating means to the light transmitting material and transmits the transmitted light to the light detecting means. In a residual stress inspection device for observing the residual stress of a light-transmitting substance, a means for irradiating the light-transmitting substance with a plurality of polarized lights having different wavelengths and polarization angles and transmitting the light-transmitting substance It is characterized in that it is provided with a light detecting means for transmitting the polarized light and a light receiving means for receiving the polarized light transmitted through the light detecting means.

Since the residual stress inspection apparatus for a light-transmitting substance according to the present invention includes means for irradiating the light-transmitting substance with a plurality of lights having different polarization directions, the light-transmitting substance can be detected without rotating the light-detecting means. The same effect as rotating the means can be obtained, and the residual stress or unevenness of the residual stress can be inspected without rotating the light detecting means. Therefore, it is possible to simplify the structure of the residual stress inspection device without the need for moving parts, and to perform the residual stress inspection at high speed.

Moreover, in this residual stress inspection apparatus, since the wavelengths of the light beams having different polarization directions are different from each other, it is possible to simultaneously irradiate the light transmissive substance with the light beams having different polarization directions.
Further, the inspection can be speeded up. That is, since the lights having different polarization directions have different wavelengths from each other, the light after passing through the light detecting means is separated for each wavelength so that the image after passing through the light detecting means is separated for each polarization direction. The residual stress can be inspected by simultaneously irradiating light with different polarization directions.

In order to separate the images of light having different polarization directions, for example, a color image pickup device is used as a light receiving device, and the light emitted by the polarized light irradiation device is separated by the color image pickup device. It should be the light of the area. For example, red light, blue light, and green light, which are the three primary colors of light, may be used as light having different polarization directions. further,
If a color image pickup device such as a color CCD camera is used, it is possible to obtain a high gain, reduce overlooking due to directivity, and perform residual stress inspection with high speed.

Another apparatus for inspecting residual stress of a light-transmitting substance according to the present invention is obtained by transmitting the polarized light emitted from the polarized light irradiation means to the light-transmitting substance and passing the transmitted light to the light detecting means. In a residual stress inspection device for observing the residual stress of a light-transmitting substance by an image, a means for generating a plurality of polarized lights having different polarization angles and sequentially irradiating the light-transmitting substance with the polarized light, and transmitting the light-transmitting substance. It is characterized in that it is provided with a light detecting means for transmitting the polarized light and a light receiving means for receiving the polarized light transmitted through the light detecting means.

Another residual stress inspection device for a light-transmitting substance according to the present invention is provided with means for irradiating the light-transmitting substance with a plurality of lights having different polarization directions. It is possible to obtain the same effect as that of rotating the light detecting means, and it is possible to inspect the residual stress or unevenness of the residual stress without rotating the light detecting means. Therefore, it is possible to simplify the structure of the residual stress inspection device without the need for moving parts, and to perform the residual stress inspection at high speed.

In addition, since the residual stress inspection device sequentially irradiates light beams having different polarization directions, it is possible to temporally separate the light beams having different polarization directions.
Therefore, it is not necessary to make the wavelengths of lights having different polarization directions different from each other, and the configurations of the polarized light irradiation means and the light receiving means can be simplified.

Since elliptically polarized light is expressed by using three parameters, at least three kinds of light are required as lights having different polarization angles in the residual stress inspection apparatus of the present invention.

The above-described constituent elements of the present invention can be arbitrarily combined as much as possible.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 3 is a schematic diagram showing the structure of a residual stress inspection apparatus 21 according to an embodiment of the present invention. In this residual stress inspection device 21,
The polarized light irradiation means includes three types of light sources (in this embodiment, these are a red light source 22, a green light source 23, and a blue light source 24) and two non-polarized beam splitters 25 and 26.
And three polarizers 27, 28 and 29. The two non-polarizing beam splitters, that is, the first non-polarizing beam splitter 25 and the second non-polarizing beam splitter 26 are arranged along the optical axis of the residual stress inspection device 21, and A red light source 22 is arranged in front of 25 via a first polarizer 27, and a green light source 23 is placed on a side surface of the first non-polarizing beam splitter 25 via a second polarizer 28. Are opposed to each other. In addition, the blue light source 2 is provided on the side surface of the second non-polarizing beam splitter 26 via the third polarizer 29.
4 are arranged facing each other. The red light source 22, the green light source 23, and the blue light source 24 have the same light emission intensity. Further, an analyzer 30 is arranged behind the second non-polarizing beam splitter 26. This analyzer 3
0 is fixed on the optical axis of the residual stress inspection device 21, and a color CCD camera 31 is installed behind it. The non-polarizing beam splitter is an optical element that transmits or reflects light without changing the polarization state of the transmitted or reflected light.

In the residual stress inspection device 21, however, when the red light source 22, the green light source 23 and the blue light source 24 are turned on, the red light emitted from the red light source 22 passes through the first polarizer 27. After being converted into linearly polarized light, the light passes through the first non-polarizing beam splitter 25 and the second non-polarizing beam splitter 26 and goes straight to the analyzer 30. Further, the green light emitted from the green light source 23 is transmitted through the second polarizer 28, converted into linearly polarized light, and then reflected by the cemented surface of the first non-polarizing beam splitter 25, and further, the second non-polarizing beam. The light passes through the polarization beam splitter 26 and goes toward the analyzer 30. Further, the blue light emitted from the blue light source 24 passes through the third polarizer 29 and is converted into linearly polarized light, and then is reflected by the joint surface of the second non-polarizing beam splitter 26 and heads for the analyzer 30. . Here, the polarization directions of the first to third polarizers 27, 28 and 29 are different from each other in the analyzer 3
The polarization angles are different from each other with respect to the polarization direction of 0. For example, the polarization direction of the first polarizer 27 forms an angle (parallel) of 0 ° with the polarization direction of the analyzer 30, and the polarization direction of the second polarizer 28 corresponds to the analyzer 3.
The third polarizer 29 forms an angle of 60 ° with respect to the polarization direction of 0, and the third polarizer 29 forms an angle of 120 ° with respect to the polarization direction of the analyzer 30. In this way, the polarizers 27, 28,
Polarizations having different wavelengths and polarization directions that have passed through 29 are overlapped and applied to the analyzer 30, and the respective polarizations that have simultaneously transmitted through the analyzer 30 are received or photographed by the color CCD camera 31.

When the residual stress of the inspection object (light transmitting substance) 32 is to be inspected, the inspection object 32 is set between the second non-polarizing beam splitter 26 and the analyzer 30. In this state, when the red light source 22, the green light source 23, and the blue light source 24 are turned on, the red polarized light, the green polarized light, and the blue polarized light converted into linearly polarized light having different polarization directions by the polarizers 27, 28, 29 are received. It passes through the inspection object 32. When the inspection object 32 has residual stress, the polarization state of the light that has passed through the inspection object 32 changes, the linearly polarized light of each color is converted into elliptically polarized light, and the linearly polarized light that has passed through the analyzer 30 is The light intensity becomes weaker according to the change of the polarization state caused by the inspection object 32. Inspected object 32 and analyzer 30
The polarized light of each color that has passed through reaches the color CCD camera 31, and the color CCD camera 31 obtains an image of three colors for each wavelength. Then, the birefringence amount and the birefringence direction of the inspection object 32 are calculated based on the light amounts of the respective wavelength images.

Next, the principle of measuring the amount of birefringence and the direction of birefringence in the residual stress inspection device 21 of the present invention will be specifically described. If the inspection object 32 has residual stress, each polarizer 2
The light of each wavelength converted into the linearly polarized light by 7, 28 and 29 is converted into the elliptically polarized light by passing through the inspection object 32. In the case of expressing elliptically polarized light, as shown in FIG. 4, the three parameters of the major radius a, the minor radius b, and the inclination ψ of the ellipse drawn by the tip of the electric field vector in the plane opposed to the traveling direction of light are set. is necessary. However, when either a or b is 0, this elliptically polarized light becomes linearly polarized light,
When a = b, circularly polarized light is obtained.

The linearly polarized light enters the inspection object 32, passes through the inspection object 32, and is converted into elliptically polarized light.
The light intensity I when light is received by the color CCD camera 31 via 0 is expressed by the following equation. I = α + β · cos2 (θ−ψ) (1) where α and β are α = (a ² + b ² ) / 2 β = (a ² − using the major radius a and the minor radius b of FIG. It is expressed as b ² ) / 2. Further, ψ is the direction of the birefringence of the inspection object 32 with reference to the polarization direction of the analyzer 30, and θ
Is an angle formed by the polarization direction of the linearly polarized light incident on the inspection object 32 and the polarization direction of the analyzer 30.

The light intensity I in the above equation (1) ideally changes in the same manner as the sine wave shown in FIG. 2 according to the change in the angle θ of the polarization direction of the polarizer. Here, the maximum value Imax and the minimum value Imin of the light intensity I can be expressed by the following equations, respectively. Imax = a ² Imin = b ²

In the above equation (1), α representing the polarization characteristic,
Since there are three unknown parameters of β and ψ, in order to obtain these parameters, at least three linearly polarized lights having different wavelengths and different polarization angles are irradiated to the inspection object 32, and light of each wavelength is If the output intensity I is measured, the values of three unknowns α, β, ψ can be obtained.

More specifically, as described above, the polarization direction θ of the first polarizer 27 (red linearly polarized light) is 0 °, and this red light passes through the object 32 to be inspected and the analyzer 30 and is colored. It is assumed that the light intensity received by the CCD camera 31 is Ir. Further, the polarization direction θ of the second polarizer 28 (green linearly polarized light) is 60 °, and this green light is the color CCD camera 3
It is assumed that the light intensity received at 1 is Ig. Similarly, the polarization direction θ of the third polarizer 29 (blue linearly polarized light) is 120
It is assumed that the intensity of this blue light received by the color CCD camera 31 is Ib. At this time, the light intensities Ir, Ig, and Ib of the respective wavelengths are calculated by the following equation (2) from the equation (1).
It is expressed as in equation (4). Ir = α + β · cos2 (0 ° −ψ) (2) Ig = α + β · cos2 (60 ° −ψ) (3) Ib = α + β · cos2 (120 ° −ψ) (4) This is an unknown number α, For β and ψ, the following (5)
~ Equation (7) is obtained.

[Equation 1]

When the arithmetic processing unit calculates the parameters α, β, ψ indicating the polarization characteristics based on the light intensity data output from the color CCD camera 31, the arithmetic processing unit stores the obtained parameters in advance. The residual stress is judged as good or bad by comparing it with the standard value.

Alternatively, when the analysis is completed, for example, the angle of the polarization direction ψ may be converted into light and dark gradations and displayed on the display device, or converted into dot sizes and printed out. In this way, the analyzed parameter has a meaning not as a single data for each pixel but as a relative difference with respect to an adjacent pixel, and by displaying this difference, the inspection object 3
The variation of the polarization characteristics of No. 2 can be visually grasped as a whole.

In the residual stress inspection device of the present invention, since it is not necessary to rotate the analyzer 30 as described above, a mechanism for rotating the analyzer 30 is not required and the structure can be simplified. it can. In particular, since it is not necessary to rotate the analyzer 30 to perform the inspection, the time required for the inspection can be shortened, and the inspection speed can be increased and the accuracy can be improved.

The positions of the red light source, the blue light source, and the green light source may be arbitrarily changed. Although three types of light sources are used here, four or more types of light sources may be used.

(Second Embodiment) FIG. 5 is a diagram showing the structure of a residual stress inspection apparatus 41 according to another embodiment of the present invention. In this residual stress inspection device 41, three or more light sources 42, 43 and 44 (three light sources are shown in FIG. 5) are arranged facing each polarizer 27, 28 and 29. ing. These light sources 42, 43 and 44 may be light sources having the same emission intensity, light sources having different wavelengths, or light sources having the same wavelength. In addition, the image pickup means C
The CD camera 45 does not need to distinguish the light of each light source,
Any type may be used as long as it corresponds to the type of light source. For example, if each light source 42, 43, 44 is the same single color light source:
It may be a monochrome CCD camera. CCD camera 4
The light reception signal from 5 is sent to the arithmetic processing circuit 46.

The light sources 42, 43 and 44 are controlled by a light emission timing control circuit 47 to emit light.
2, 43, and 44 are sequentially made to emit light for a short time at intervals by a light emission synchronization signal (trigger pulse signal) from the light emission timing control circuit 47. The light emission synchronization signal is also transmitted to the arithmetic processing circuit 46.

In the residual stress inspection device 41, the light sources 42, 43 and 44 are sequentially caused to emit light in synchronization with the light emission synchronization signal, and the light emission synchronization signal is also sent to the arithmetic processing circuit 46. Since it is sent, the light of each light source 42, 43, 44 can be discriminated even if the wavelength is the same.
The arithmetic processing circuit 46 can know the polarization direction of the linearly polarized light corresponding to the received light signal received from the CCD camera 45. Therefore, according to this embodiment, the birefringence can be measured without rotating the analyzer 30 using the light source of the same wavelength and without using the expensive color CCD camera, as in the first embodiment. You can

[0032]

According to the residual stress inspection device for a light-transmitting substance of the present invention, the same effect as rotating the light detecting means without rotating the light detecting means can be obtained. The residual stress or unevenness of the residual stress can be inspected without rotating. Therefore, it is possible to simplify the structure of the residual stress inspection device without the need for moving parts, and to perform the residual stress inspection at high speed.

Further, in this residual stress inspection apparatus, since the wavelengths of the light beams having different polarization directions are different, it is possible to simultaneously irradiate the light transmissive substance with light beams having different polarization directions.
Further, the inspection can be speeded up. That is, since the lights having different polarization directions have different wavelengths from each other, the light after passing through the light detecting means is separated for each wavelength so that the image after passing through the light detecting means is separated for each polarization direction. The residual stress can be inspected by simultaneously irradiating light with different polarization directions.

Another residual stress inspection apparatus for a light-transmitting substance according to the present invention comprises means for irradiating the light-transmitting substance with a plurality of lights having different polarization directions, so that the light detecting means is not rotated. It is possible to obtain the same effect as that of rotating the light detecting means, and it is possible to inspect the residual stress or unevenness of the residual stress without rotating the light detecting means. Therefore, it is possible to simplify the structure of the residual stress inspection device without the need for moving parts, and to perform the residual stress inspection at high speed.

In addition, since the residual stress inspection device sequentially irradiates light with different polarization directions, it is possible to temporally separate light with different polarization directions.
Therefore, it is not necessary to make the wavelengths of lights having different polarization directions different from each other, and the configurations of the polarized light irradiation means and the light receiving means can be simplified.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an inspection device using a rotation analyzer method.

FIG. 2 is a diagram showing a change in light intensity when a relative polarization rotation angle between an analyzer and a polarizer is changed.

FIG. 3 is a schematic diagram showing a configuration of a residual stress inspection device according to an embodiment of the present invention.

FIG. 4 is a diagram showing a mathematical expression of elliptically polarized light.

FIG. 5 is a schematic diagram showing a configuration of a residual stress inspection device according to another embodiment of the present invention.

[Explanation of symbols]

21 Residual stress inspection device 22 Red light source 23 Green light source 24 blue light source 25,26 Non-polarizing beam splitter 27, 28, 29 Polarizer 30 Analyzer 31 color CCD camera 32 Inspection object

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Claims (4)

[Claims] 1. A residual stress test for observing the residual stress of a light-transmitting substance by an image obtained by transmitting the polarized light emitted from the polarized light irradiation means to the light-transmitting substance and passing the transmitted light through the light-detecting means. In the device, means for generating a plurality of polarized lights having wavelengths and polarization angles different from each other and irradiating the light-transmissive substance with the polarized lights, analyzing means for transmitting the polarized light transmitted through the light-transmissive substance, and the light analyzer And a light receiving means for receiving polarized light transmitted through the means. 2. The light receiving unit is a color image pickup device, and the light emitted by the polarized light irradiation unit is light in a wavelength range that can be separated by the color image pickup device. The residual stress inspection device for a light-transmitting substance according to claim 1. 3. A residual stress test for observing the residual stress of a light transmissive substance by an image obtained by transmitting the polarized light emitted from the polarized light irradiation means to the light transmissive substance and passing the transmitted light through the light detecting means. In the apparatus, means for generating a plurality of polarized lights having different polarization angles and sequentially irradiating the light-transmissive substance with the polarized light; light-analyzing means for transmitting the polarized light having passed through the light-transmissive substance; A residual stress inspection device for a light-transmissive substance, comprising: 4. The residual stress test of a light-transmissive material according to claim 1, wherein the light emitted by the polarized light irradiation means is three or more lights having different polarization angles. apparatus.