Optics: measuring and testing – By light interference – For dimensional measurement
Reexamination Certificate
2001-10-31
2004-05-11
Font, Frank G. (Department: 2877)
Optics: measuring and testing
By light interference
For dimensional measurement
C349S184000
Reexamination Certificate
active
06734977
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2001-323731, filed on Oct. 22, 2001, entitled “METHOD AND APPARATUS FOR MEASURING GAP, METHOD AND APPARATUS FOR MEASURING SHAPE AND METHOD FOR MANUFACTURING LIQUID CRYSTAL DEVICE”. The contents of that application are incorporated herein by reference in their entirely.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to technology for measuring a gap between members or shape thereof by utilizing interference of light.
2. Description of the Related Art
For example, a conventional gap measuring apparatus having a configuration shown in
FIG. 20
has been developed as an apparatus for measuring a gap between light transmission members, such as liquid crystal cells. This apparatus utilizes a phenomenon that light waves respectively reflected by the top surface and the bottom surface of a gap having an effective thickness d (incidentally, the refractive index of a medium is assumed to be n) illuminated by light, which is irradiated from an objective lens of a microscope through a half-mirror, return thereto in such a way as to cause a phase difference 2nd therebetween, and that these light waves pass through a Wollaston prism and polarizing plates A and P to thereby generate interference fringes. That is, the value of the gap d is determined by measuring the peak gap y between an interference fringe, which is generated by the interference between light waves both reflected by one of the top and bottom surfaces, and another interference fringe, which is generated on the line of intersection between the wavefronts of light waves respectively reflected by the top and bottom surfaces, according to the following equation (1):
y=nd
/(
e
−n
o
) tan &thgr; (1)
where &zgr; designates a prism angle of a Wollaston prism, and n
e
and n
o
denote refractive indexes of the Wollaston prism.
However, the conventional gap measuring apparatus is operative to measure the gap therebetween correspondingly to one point of an object at a time. Thus, to measure the distribution of the gaps in a predetermined section, the conventional gap measuring apparatus should repeatedly perform the measurement of the gap by shifting the object therein. Thus, an operation of measuring the gap is complex and time-consuming.
SUMMARY OF THE INVENTION
The invention is accomplished taking the aforementioned problem into consideration.
Accordingly, an object of the invention is to provide a method and apparatus each enabled to measure the gap or shape of an object at a high speed with high accuracy and a method for effectively manufacturing a liquid crystal device.
To achieve the foregoing object, the present invention adopts the following structures.
(1) A gap measuring method comprising the steps of:
shifting a wavelength of light stepwise within a predetermined wavelength range to use the light for measuring a gap;
taking an image of an interference fringe, which is generated owing to a gap provided in a measured object and the used light with the shifted wavelength, by a camera correspondingly to each step of the shifted wavelength;
obtaining a change in the intensity of the images of the interference fringes taken by said camera at each of predetermined positions of each image, over said predetermined wavelength range; and
determining gap values of a plurality of points of the gap based on the obtained changes in the density.
(2) A gap measuring method according to (1), wherein said step of determining a gap value includes the steps of:
obtaining a theoretical change in the intensity of the images, over said predetermined wavelength range, correspondingly to each of preliminarily set gap values; and
determining the gap value of said measured object based on the change in the intensity of the fixed position of each image taken by the camera and the obtained theoretical changes in the intensity.
(3) A gap measuring method according to (1), wherein said step of determining a gap value includes the steps of:
obtaining a plurality of peaks in said change in the intensity of the images, over the predetermined wavelength range; and calculating gap values of a plurality of points of the measured object based on a plurality of wavelengths respectively corresponding to the peaks.
(4) A gap measuring method according to any one of (1)~(3), wherein said interference fringe is obtained by utilizing light transmitted by said measured object.
(5) A gap measuring method according to any one of (1)~(3), wherein said interference fringe is obtained by utilizing light reflected from said measured object.
(6) A gap measuring method according to any one of (1)~(5), wherein said shifted wavelength of the used light is obtained by shifting a wavelength of light emitted from a light source to said measured object.
(7) A gap measuring method according to any one of (1)~(5), wherein said shifted wavelength of the used light is obtained by providing a filter, which is adapted to selectively transmit a certain wavelength of light to the side of said camera.
(8) A gap measuring method according to any one of (1)~(7), wherein said change in the density of images taken by the camera, is corrected in consideration of variable factors.
(9) A gap measuring method according to any one of (1)~(8), wherein the said image consists of a plurality of pixels, to measure the gap value for each of the pixels.
(10) A shape measuring method comprising the steps of:
measuring gap values of a gap between a pair of members, one of which has a flat surface, by the gap measuring method according to any one of (1)~(9); and
determining a shape of the other member constituting said gap, based on the measured gap values.
(11) A gap measuring apparatus comprising:
a wavelength variable light source for shifting a wavelength of light stepwise within a predetermined range and applying the light with the shifted wavelength onto a light transmissible object that is to be measured and is provided with a gap;
a camera for taking an image of an interference fringe formed by the light transmitted by said object, correspondingly to each step of the shifted wavelength;
an image memory for storing images taken by said camera; and
means for obtaining a change in the intensity of the images taken by said camera, at each of predetermined positions of each image over said predetermined wavelength range; and means for determining gap values of a plurality of points of the gap based on the obtained changes in the intensity.
(12) A gap measuring apparatus comprising:
a white light source for applying white light onto a light transmissible object that is to be measured and is provided with a gap;
a filter for shifting, stepwise, a wavelength of the light transmitted by said measured object within a predetermined wavelength range to send the light with the shifted wavelength to said camera;
a camera for taking an image of an interference fringe formed by said light transmitted by the filter, correspondingly to each step of the shifted wavelength;
an image memory for storing images taken by said camera;
means for obtaining a change in the intensity of the images taken by said camera, at each of predetermined positions of each image over said predetermined wavelength range; and means for determining gap values of a plurality of points of the gap based on the obtained changes in the intensity.
(13) A gap measuring apparatus comprising:
a wavelength variable light source for shifting a wavelength of light stepwise within a predetermined range and emitting the light with the shifted wavelength;
a camera for taking an image of an interference fringe of light;
optical means for directing the light emitted from said light source to a measured object provided with a gap and directing the light reflected by said measured object to said camera;
an image memory for storing images of interference fringes formed by the light from said optical means and taken by said camera; and
means for obtaining a change in the
Connolly Patrick
Font Frank G.
Harness & Dickey & Pierce P.L.C.
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