Abstract:
The present invention provides an 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.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
         [0001]    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  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to technology for measuring a gap between members or shape thereof by utilizing interference of light.  
           [0004]    2. Description of the Related Art  
           [0005]    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 /( n   e   −n   o ) tan θ  (1) 
           [0006]    where θ designates a prism angle of a Wollaston prism, and n e  and n o  denote refractive indexes of the Wollaston prism.  
           [0007]    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  
         [0008]    The invention is accomplished taking the aforementioned problem into consideration.  
           [0009]    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.  
           [0010]    To achieve the foregoing object, the present invention adopts the following structures.  
           [0011]    (1) A gap measuring method comprising the steps of:  
           [0012]    shifting a wavelength of light stepwise within a predetermined wavelength range to use the light for measuring a gap;  
           [0013]    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;  
           [0014]    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  
           [0015]    determining gap values of a plurality of points of the gap based on the obtained changes in the density.  
           [0016]    (2) A gap measuring method according to (1), wherein said step of determining a gap value includes the steps of:  
           [0017]    obtaining a theoretical change in the intensity of the images, over said predetermined wavelength range, correspondingly to each of preliminarily set gap values; and  
           [0018]    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.  
           [0019]    (3) A gap measuring method according to (1), wherein said step of determining a gap value includes the steps of:  
           [0020]    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.  
           [0021]    (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.  
           [0022]    (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.  
           [0023]    (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.  
           [0024]    (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.  
           [0025]    (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.  
           [0026]    (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.  
           [0027]    (10) A shape measuring method comprising the steps of:  
           [0028]    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  
           [0029]    determining a shape of the other member constituting said gap, based on the measured gap values.  
           [0030]    (11) A gap measuring apparatus comprising:  
           [0031]    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;  
           [0032]    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;  
           [0033]    an image memory for storing images taken by said camera; and  
           [0034]    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.  
           [0035]    (12) A gap measuring apparatus comprising:  
           [0036]    a white light source for applying white light onto a light transmissible object that is to be measured and is provided with a gap;  
           [0037]    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;  
           [0038]    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;  
           [0039]    an image memory for storing images taken by said camera;  
           [0040]    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.  
           [0041]    (13) A gap measuring apparatus comprising:  
           [0042]    a wavelength variable light source for shifting a wavelength of light stepwise within a predetermined range and emitting the light with the shifted wavelength;  
           [0043]    a camera for taking an image of an interference fringe of light;  
           [0044]    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;  
           [0045]    an image memory for storing images of interference fringes formed by the light from said optical means and taken by said camera; and  
           [0046]    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 range; and means for determining gap values of a plurality of points of the gap based on the obtained changes in the intensity.  
           [0047]    (14) A gap measuring apparatus comprising:  
           [0048]    a white light source for emitting white light;  
           [0049]    a camera for taking an image of an interference fringe of light;  
           [0050]    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;  
           [0051]    a filter for shifting, stepwise, a wavelength of the light from said optical means within a predetermined range to send the light with the shifted wavelength to said camera;  
           [0052]    an image memory for storing images of interference fringes formed by the light from said optical means and taken by said camera; and  
           [0053]    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.  
           [0054]    (15) A gap measuring apparatus according to any one of (11)-(14), wherein said means for determining a gap value includes:  
           [0055]    a reference data memory for storing data representing a theoretical change in the intensity of the images, over said predetermined range, correspondingly to each of preliminarily set gap values; and  
           [0056]    gap value comparison and determination means for determining gap values of a plurality of points of gap based on the changes in the intensity the images and the theoretical changes in the intensity.  
           [0057]    (16) A gap measuring apparatus according to any one of (11)-(14), wherein said means for determining the gap values includes:  
           [0058]    means for obtaining a plurality of peaks in said change in the intensity of the images, over the predetermined wavelength range; and means for calculating gap values of a plurality of points of the gap based on a plurality of wavelengths respectively corresponding to the peaks.  
           [0059]    (17) A gap measuring apparatus according to any one of (11)-(16), which further comprises correction means for correcting the change in the density of the images taken by the camera, in consideration of variable factors.  
           [0060]    (18) A shape measuring apparatus comprising:  
           [0061]    a wavelength variable light source for shifting a wavelength of light stepwise within a predetermined range and irradiating the light with the shifted wavelength onto a light transmissible object that is to be measured;  
           [0062]    a light transmissible plate-like element which has a flat surface and is oppositely placed to said object with intervention of a gap;  
           [0063]    a camera for taking an image of an interference fringe formed by the light with the shifted wavelength transmitted by said object and said plate-like element, correspondingly to each step of the shifted wavelength;  
           [0064]    an image memory for storing images taken by said camera;  
           [0065]    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 range; means for determining gap values of a plurality of points of the gap based on the obtained changes in the intensity; and  
           [0066]    gap-value-to-shape conversion means for determining a shape of said object based on the determined gap values.  
           [0067]    (19) A shape measuring apparatus comprising:  
           [0068]    a white light source for emitting white light onto a light transmissible object that is to be measured;  
           [0069]    a light transmissible plate-like element which has a flat surface and is oppositely placed to said object with intervention of a gap;  
           [0070]    a filter for shifting, stepwise, wavelength of the light transmitted by the object and the plate-like element within a predetermined range to send the light with the shifted wavelength to said camera;  
           [0071]    a camera for taking an image of an interference fringe formed by said light transmitted by said filter, correspondingly to each step of the shifted wavelength;  
           [0072]    an image memory for storing images taken by said camera;  
           [0073]    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; means for determining gap values of a plurality of points of the gap based on the obtained changes in the intensity; and  
           [0074]    gap-value-to-shape conversion means for determining a shape of said object based on the determined gap values.  
           [0075]    (20) A shape measuring apparatus comprising:  
           [0076]    a wavelength variable light source for shifting a wavelength of light stepwise within a predetermined range and emitting the light with the shifted wavelength onto an object to be measured;  
           [0077]    a light transmissible plate-like element which has a flat surface and is oppositely placed to said object with intervention of a gap;  
           [0078]    a camera for taking an image of an interference fringe of light;  
           [0079]    optical means for directing the light emitted from said light source to an object to be measured and directing the light reflected by said object and said plate-like element to said camera;  
           [0080]    an image memory for storing images of interference fringes formed by the light from said optical means and taken by said camera;  
           [0081]    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; means for determining gap values of a plurality of points of the gap based on the obtained changes in the intensity; and  
           [0082]    gap-value-to-shape conversion means for determining a shape of said object based on the determined gap values.  
           [0083]    (21) A shape measuring apparatus comprising:  
           [0084]    a white light source for emitting white light onto an object that is to be measured;  
           [0085]    a light transmissible plate-like element which has a flat surface and is oppositely placed to said object with intervention of a gap;  
           [0086]    a camera for taking an image of an interference fringe of light;  
           [0087]    optical means for directing the light emitted from said light source to the object and directing the light reflected by said object and said plate-like element to said camera;  
           [0088]    a filter for shifting, stepwise, wavelength of light transmitted from said optical means within a predetermined range to send the light with the shifted wavelength to said camera;  
           [0089]    an image memory for storing images of interference fringes formed by the light from said filter and taken by said camera;  
           [0090]    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; means for determining gap values of a plurality of points of the gap based on the obtained changes in the intensity; and  
           [0091]    gap-value-to-shape conversion means for determining a shape of said object based on the determined gap values.  
           [0092]    (22) A shape measuring apparatus according to any one of (18)-(21), wherein said means for determining a gap value includes:  
           [0093]    a reference data memory for storing data representing a theoretical change in the intensity of the images, over said predetermined range, correspondingly to each of preliminarily set gap values; and  
           [0094]    gap value comparison and determination means for determining gap values of a plurality of points of the gap based on the changes in intensity of the images and the theoretical changes in the intensity.  
           [0095]    (23) A shape measuring apparatus according to any one of (18)-(21), wherein said means for determining the gap values includes:  
           [0096]    means for obtaining a plurality of peaks in said change in the intensity of the images, over the predetermined wavelength range; and means for calculating gap values of a plurality of the gap based on a plurality of wavelengths respectively corresponding to the peaks.  
           [0097]    (24) A shape measuring apparatus according to any one of (18)-(23), which further comprises correction means for correcting the change in the intensity of the images taken by the camera, in consideration of variable factors.  
           [0098]    (25) A manufacturing method for a liquid crystal device, in which a gap between two substrates is filled with liquid crystal and sealed, wherein gap values of a plurality of points of the gap is measured by utilizing said gap measuring apparatus according to any one of (11)-(17), and wherein liquid crystal is injected into said gap when the gap values are within a prescribed range. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0099]    Other features, objects and advantages of the present invention will become apparent from the following description of preferred embodiments with reference to the drawings in which like reference characters designate like or corresponding parts throughout several views, and in which:  
         [0100]    [0100]FIG. 1 is a diagram illustrating the configuration of a first optical system for obtaining a monochrome image of an interference fringe according to a mode for carrying out the invention;  
         [0101]    [0101]FIG. 2 is a diagram illustrating the configuration of a second optical system for obtaining a monochrome image of an interference fringe according to a mode for carrying out the invention;  
         [0102]    [0102]FIG. 3 is a diagram illustrating configuration of a third optical system for obtaining a monochrome image of an interference fringe according to a mode for carrying out the invention;  
         [0103]    [0103]FIG. 4 is a diagram illustrating the configuration of a fourth optical system for obtaining a monochrome image of an interference fringe according to a mode for carrying out the invention;  
         [0104]    [0104]FIG. 5 is a block diagram illustrating a primary configuration of a gap measuring apparatus that is a first embodiment of the invention;  
         [0105]    [0105]FIG. 6 is a graph illustrating correction data for correcting a change in the intensity of an interference fringe, which is obtained from the image;  
         [0106]    [0106]FIG. 7 is a graph illustrating a change in the intensity of an interference fringe at a certain position in the image within a predetermined range of wavelengths;  
         [0107]    [0107]FIG. 8 is a graph illustrating corrected change in the intensity of an interference fringe at a certain position in the image within a predetermined range of wavelengths;  
         [0108]    [0108]FIG. 9 is a schematic diagram illustrating interference between light waves I 1  and I 2  transmitted by a gap;  
         [0109]    [0109]FIG. 10 is a graph illustrating a theoretical change in the intensity of interference fringes within a predetermined range of wavelengths according to a plurality of predetermined gap values;  
         [0110]    [0110]FIG. 11 is a flowchart illustrating a measuring procedure to be performed by a gap measuring apparatus that is the first embodiment of the invention;  
         [0111]    [0111]FIG. 12A is a block diagram illustrating a primary configuration of a gap measuring apparatus that is a second embodiment of the invention;  
         [0112]    [0112]FIG. 12B is a graph illustrating an operation of calculating a gap value of an object, which is performed by the gap measuring apparatus that is the second embodiment of the invention;  
         [0113]    [0113]FIG. 13 is a flowchart illustrating a measuring procedure to be performed by the gap measuring apparatus that is the second embodiment of the invention;  
         [0114]    [0114]FIG. 14 is a diagram illustrating the configuration of a fifth optical system for obtaining a monochrome image of an interference fringe according to a mode for carrying out the invention;  
         [0115]    [0115]FIG. 15 is a diagram illustrating the configuration of a sixth optical system for obtaining a monochrome image of an interference fringe according to a mode for carrying out the invention;  
         [0116]    [0116]FIG. 16 is a diagram illustrating the configuration of a seventh optical system for obtaining a monochrome image of an interference fringe according to a mode for carrying out the invention;  
         [0117]    [0117]FIG. 17 is a diagram illustrating the configuration of a eighth optical system for obtaining a monochrome image of an interference fringe according to a mode for carrying out the invention;  
         [0118]    [0118]FIG. 18 is a block diagram illustrating a primary configuration of a gap measuring apparatus that is a third embodiment of the invention;  
         [0119]    [0119]FIG. 19 is a block diagram illustrating a primary configuration of a gap measuring apparatus that is a fourth embodiment of the invention;  
         [0120]    [0120]FIG. 20 is a diagram illustrating the configuration of a conventional gap measuring apparatus; and  
         [0121]    [0121]FIG. 21 is a diagram illustrating a process of manufacturing a liquids crystal device according to a mode for carrying out the invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0122]    Hereinafter, the preferred embodiments of the present invention will be described in detail by referring to the accompanying drawings.  
         [0123]    (1) Configuration of Optical System for Obtaining Image Data of Interference Fringe  
         [0124]    (First Example)  
         [0125]    [0125]FIG. 1 is a diagram illustrating the configuration of a first optical system for obtaining an image of an interference fringe according to a mode for carrying out the invention. This system employs a wavelength variable light source  1  enabled to perform wavelength scanning or wavelength shifting at every nanometer within a predetermined range of wavelength from, for example, 450 nm to 550 nm. Light outputted from the wavelength variable light source  1  is applied through a backlight  2  onto an object  100  to be measured. Then, the light is transmitted by the object  100 . Subsequently, an image of interference fringes generated due to a gap  101  provided in the object  100  is taken by a monochrome camera  3 . Therefore, in this case, image data respectively corresponding to 100 wavelengths are obtained.  
         [0126]    Incidentally, a monochrome light source provided with a spectroscope enabled to perform wavelength scanning within a range of wavelength from 250 nm to 1200 nm is currently available. Thus, such a monochrome light source can be used as the wavelength variable light source  1 .  
         [0127]    (Second Example)  
         [0128]    [0128]FIG. 2 is a diagram illustrating the configuration of a second optical system for obtaining an image of an interference fringe according to a mode for carrying out the invention. In this example, light outputted from a white light source  4  is applied through a backlight  2  onto an object  100  to be measured. Then, the light is transmitted by the object  100 . Subsequently, an image of interference fringes generated due to a gap  101  provided in the object  100  is taken by a monochrome camera  3 . Therefore, in this case, image data of 100 wavelengths is obtained. In this system, a wavelength selection filter  5  enabled to perform wavelength scanning at every nanometer within a predetermined range of wavelength from, for instance, 450 nm to 550 nm is provided at the side of the monochrome camera  3 . Further, an image of interference fringes is taken at every scanned wavelength of light transmitted by the wave selection filter  5 . In this case, similarly, image data respectively corresponding to 100 wavelengths are obtained. Incidentally, the wavelength selection filter  5  may be provided in the monochrome camera  3 .  
         [0129]    (Third Example)  
         [0130]    [0130]FIG. 3 is a diagram illustrating the configuration of a third optical system for obtaining an image of an interference fringe according to a mode for carrying out the invention. This system employs a wavelength variable light source  1  enabled to perform wavelength scanning at every nanometer within a predetermined range of wavelength from, for example, 450 nm to 550 nm. Light outputted from the wavelength variable light source  1  is reflected by a beam splitter  6  to an object  100  to be measured. Then, the light is reflected again by the object  100 . Subsequently, the reflected light is transmitted by the beam splitter  6 . An image formed from the transmitted light is taken by a monochrome camera  3 . Thus, an image of the interference fringes generated owing to a gap  101 , which is provided in the object  100 , is taken. In this case, similarly, image data respectively corresponding to 100 wavelengths are obtained.  
         [0131]    (Fourth Example)  
         [0132]    [0132]FIG. 4 is a diagram illustrating the configuration of a fourth optical system for obtaining an image of an interference fringe according to a mode for carrying out the invention. This system employs a white light source  4 . Light outputted from the white light source  4  is reflected by a beam splitter  6  to an object  100  to be measured. Then, the light is reflected again by the object  100 . Subsequently, the reflected light is transmitted by the beam splitter  6 . An image formed from the transmitted light is taken by a monochrome camera  3 . Thus, an image of the interference fringes generated owing to a gap  101 , which is provided in the object  100 , is taken. In this system, a wavelength selection filter  5  enabled to perform wavelength scanning at every nanometer within a predetermined range of wavelength from, for instance, 450 nm to 550 nm is provided at the side of the monochrome camera  3 . Further, an image of interference fringes is taken at every scanned wavelength of light transmitted by the wave selection filter  5 . In this case, similarly, image data respectively corresponding to 100 wavelengths are obtained. Incidentally, the wavelength selection filter  5  may be provided in the monochrome camera  3 .  
         [0133]    In the case of the third and fourth examples, the system may be adapted so that light outputted from the light source is transmitted by the beam splitter  6  toward the object  100 , that then, the light is reflected by the object  100 , that subsequently, the light is reflected again by the beam splitter  6 , and that an image formed from this reflected light is taken by the monochrome camera  3 .  
         [0134]    (2) Gap Measuring Apparatus of the Invention  
         [0135]    First Embodiment  
         [0136]    (i) Configuration  
         [0137]    [0137]FIG. 5 is a block diagram illustrating a primary configuration of a gap measuring apparatus that is an embodiment of the invention. Further, reference numeral  11  designates an optical system for obtaining a monochrome image of an interference fringe, which has been described in the description of the first to fourth examples in Section (1). Reference numeral  12  denotes an image memory for storing image data obtained by the optical system  11 . Reference numeral  13  designates a correction data memory for preliminarily storing correction data which will be described later. Reference numeral  14  denotes a reference data memory for storing reference data relating to a theoretical change in the intensity of the interference fringes within the wavelength scanning range according to a plurality of predetermined gap values.  
         [0138]    Further, reference numeral  15  designates means for determining the gap value of a gap provided in an object to be measured. This means  15  has image intensity change calculation means  151  for obtaining a change in the intensity of a fixed position among predetermined positions (which are arbitrarily set in each image, for example, at all pixels over the image or every pixel on a center line in the width direction of the image) in each image across the images of interference fringes corresponding to the scanned wavelength, which are read out from the image memory  12 , and for correcting the change in the intensity according to correction data stored in the correction data memory  13 , and also has gap value comparison and determination means  152  for comparing a change in the intensity obtained by the image intensity change calculation means  151 , with a theoretical intensity change stored in the reference data memory  14 , to determine a set gap value corresponding to the theoretical change in the intensity, which is most close to the change in the intensity obtained by the image intensity calculation means  151 , as the gap value at the fixed position on the object.  
         [0139]    (ii) Correction Data Stored in Correction Data Memory  13   
         [0140]    An image taken by the monochrome camera  3  is affected mainly by the variable factors, such as (a) the emission spectroscopy characteristics of the light source, (b) the spectral characteristics of a lighting optical system, and (c) the spectral characteristics of the camera. Therefore, influence based on those factors should be eliminated. Hence, it is preferable that a correction table is preliminarily created, and that the change in the intensity, which is obtained from the images taken by the camera, is corrected into an appropriate value. This correction table contains data as illustrated in FIG. 6 that indicates the relation between the wavelength and the intensity (or brightness). This data is obtained by measuring the mean intensity of an image of an interference fringe in a region having a dense interference fringe, at every wavelength or by preparing a sample having a gap that is equal to or longer than a coherence length, and measuring the intensity thereof at every wavelength. When the change in the intensity of the fixed position which is obtained from the images taken by the camera and illustrated in FIG. 7 is divided or subtracted by the data contained in this correction table to normalize, data illustrated in FIG. 8, which represents the corrected change in the intensity of the fixed position in the images, is obtained.  
         [0141]    (iii) Reference Data Stored in Reference Data Memory  14   
         [0142]    When light having a wavelength λ is passed through a gap d provided between parallel flat-plates, light waves I 1  and I 2  passed therethrough interfere with each other as illustrated in FIG. 9. Thus, the intensity I of a fixed position in a image of an interference fringe is given by:  
           I=I   1   +I   2 +2( I   1   ·I   2 /λ) ½ ·cos (4π d )   (2). 
         [0143]    Incidentally, for example, in the case that I 1 +I 2 =2(I 1 ·I 2 ) ½ =½, and that a value within a range to be measured, for instance, from 3000 nm to 4100 nm is given to the gap d, the intensity I of the fixed position in the image is obtained corresponding to each scanned wavelength λ. Further, the theoretical change in the intensity within the wavelength scanning range is obtained according to this intensity I. Such processing is performed correspondingly to each of a plurality of preliminarily set gap values. Consequently, reference data representing the theoretical change in the intensity according to the set gap values, as illustrated in, for instance, a graph of FIG. 10 is obtained.  
         [0144]    (iv) Measuring Procedure  
         [0145]    [0145]FIG. 11 is a flowchart illustrating a measuring procedure to be performed by the gap measuring apparatus that is the first embodiment of the invention.  
         [0146]    First, data representing a plurality of monochrome images of interference fringes corresponding to scanned wavelengths are stored into the image memory  12  at step S 1  by utilizing the optical system  11  for obtaining a monochrome image of an interference fringe.  
         [0147]    Subsequently, the image intensity change calculation means  151  reads out, for example, 100 images from the image memory  12 , obtains a change in the intensity of a fixed position among the aforementioned predetermined positions in each image, across the 100 images, at step S 2 . Then, the image intensity change calculation means  151  corrects the obtained change in the intensity according to the correction data stored in the correction data memory  13  at step S 3 , so that the change in the intensity of the fixed position in the images within the wavelength scanning range is represented by using the corrected data.  
         [0148]    Furthermore, the gap value comparison and determination means  152  compares the change in the intensity obtained by the image intensity change calculation means  151 , with the theoretical intensity change represented by the reference data stored in the reference data memory  14 . Then, the gap value comparison and determination means  152  determines the gap value, which corresponds to a theoretical intensity change that is closest to the obtained change in the intensity of the fixed position in the images, as a gap value of a gap provided in the object at a position corresponding to the fixed position in the images, at step S 4 .  
         [0149]    Therefore, in the case that, for instance, the predetermined positions are set in the central portion of the object with uniform intervals in the direction of width, and the data processing consisting of steps S 2  to S 4  is performed correspondingly to each of the predetermined positions, the gap in the direction of width and in the central portion of the object can be determined.  
         [0150]    Incidentally, the steps S 2  to S 4  may be repeatedly performed for each of the predetermined positions. Further, gap values at all the predetermined positions may be determined by obtaining a change in the intensity of each predetermined position by steps S 2  an S 3  and comparing the obtained change with the theoretical change in the intensity.  
         [0151]    Additionally, in the case that a CCD camera is used as the monochrome camera  3 , and that the process consisting of steps S 2  to S 4  is repeatedly performed on each of the pixels of the obtained image, the gap of the object can be measured in a three-dimensional manner.  
         [0152]    Second Embodiment  
         [0153]    (i) Configuration  
         [0154]    [0154]FIG. 12A is a block diagram illustrating a primary configuration of a gap measuring apparatus that is another embodiment of the invention. Incidentally, each of reference numerals  11  to  13  designates a constituent element that is the same as the corresponding constituent elements described in the description of the first embodiment. Further, means  16  for determining a gap value comprises image intensity change calculation means  161  for reading out a plurality of images from the image, memory  12 , obtaining a change in the intensity of a fixed position among the aforementioned predetermined positions in each image across the read out images, and correcting the change in the intensity according to correction data stored in the correction data memory  13 , and also comprises gap value calculation means  162  for obtaining wavelengths λ 1  and λ 2  corresponding to peaks appearing in the change in the intensity corrected by the means  161  and for calculating the gap value d of the object according to the following equation:  
           d =λ 1 ·λ 2 /2(λ 2 −λ 1 )   (3) 
         [0155]    Incidentally, the equation (3) is explained in FIG. 12B. In a change in the intensity of light with a variable wavelength, at a certain position, if a peak of the intensity appears at wavelength λ 1  and a next peak appears at the wavelength λ 2 , the following equation is adapted.  
           m  λ 1 =2 d,  ( m− 1)λ 2 =2 d,    
         [0156]    where 2d is a difference in optical path lengths caused by the gap, and m is a order number of the wavelength λ 1 . Then, m is deleted from the equations to obtain  
           d =λ 1 ·λ 2 /2(λ 2 −λ 1 ). 
         [0157]    (ii) Measuring Procedure  
         [0158]    [0158]FIG. 13 is a flowchart illustrating the measuring procedure to be performed by the gap the gap measuring apparatus that is the second embodiment of the invention.  
         [0159]    First, a plurality of monochrome images of interference fringes are stored into the image memory  12  at step S 11  by utilizing the optical system  11  for obtaining a monochrome image of an interference fringe.  
         [0160]    Subsequently, the image intensity change calculation means  161  reads out, for example, 100 images from the image memory  12 , obtains a change in the intensity of a fixed position among aforementioned predetermined positions in each image, across the 100 images, at step S 12 . Then, the image intensity change calculation means  161  corrects the obtained change in the intensity according to the correction data stored in the correction data memory  13  at step S 13 , so that the change in the intensity of the fixed position in the images within the wavelength scanning range is represented by using the corrected data.  
         [0161]    Furthermore, the gap value calculation means  162  obtains wavelengths λ 1  and λ 2  corresponding to peaks appearing in the change in the intensity corrected by the means  161  and calculates the gap values of the gap of the object at a position corresponding to the fixed position in the images, at step S 14 .  
         [0162]    Therefore, in the case that, for instance, the predetermined positions are set in the central portion of the object with uniform intervals in the direction of width, and the data processing consisting of steps S 12  to S 14  is performed correspondingly to each of the predetermined positions, the gap in the direction of width and in the central portion of the object can be determined.  
         [0163]    Incidentally, the steps S 12  to S 14  may be repeatedly performed for each of the predetermined positions. Further, gap values at all the predetermined positions may be determined by obtaining a change in the intensity of each predetermined position by steps S 12  and S 13  and comparing the corrected change with the theoretical change in the intensity.  
         [0164]    Additionally, in the case that a CCD camera is used as the monochrome camera  3 , and that the process consisting of steps S 12  to S 14  is repeatedly performed on each of the pixels of the obtained image, the gap of the object can be measured in a three-dimensional manner.  
         [0165]    (3) Shape Measuring Apparatus of the Invention  
         [0166]    (i) Configuration  
         [0167]    A shape measuring apparatus according to an embodiment of the invention is configured by adding additional constituent elements to the gap measuring apparatus described in the description of the first or second embodiment. That is, the optical system  11  for obtaining a monochrome image of an interference fringe as illustrated in FIGS.  1  to  4  is replaced with an optical system  12 , to which a transparent plate-like element  7  having a surface facing an object  200  in such a way as to provide a gap  201  and as to be flat is added, for obtaining a monochrome image of an interference fringe as illustrated in FIGS.  14  to  17 . Moreover, the shape measuring apparatus of the invention has gap-value-to-shape conversion means  17  for determining the shape of the object  200  according to the gap value obtained by gap value determination means  15  or  16 . This utilizes the fact that the difference between the gap values of the gap formed between the transparent plate-like element  7  and the object  200  at given two places on the flat surface of the element  7  corresponds to a change in height of the gap forming surface of the object  200  at the given two places because the transparent plate-like element  7  has the flat shape.  
         [0168]    The configuration of a shape measuring apparatus constituted as a third embodiment of the invention is illustrated in a block diagram of FIG. 18, while that of a shape measuring apparatus constituted as a fourth embodiment of the invention is illustrated in a block diagram of FIG. 19. Incidentally, the third embodiment corresponds to the gap measuring apparatus that is the first embodiment. Further, the fourth embodiment corresponds to the gap measuring apparatus that is the second embodiment.  
         [0169]    (ii) Measuring Procedure  
         [0170]    In the case of the shape measuring apparatus that is the third embodiment, processing to be performed at steps S 2  to S 4  is performed over a measuring range of the object  200  after step S 1  illustrated in FIG. 11. Thus, a plurality of gap values of gaps formed between the transparent plate-like element  7  and the object  200  are determined. Subsequently, the gap-value-to-shape conversion means  17  converts the determined gap value into data representing a change in the shape of the gap forming surface of the object  200 , so that the shape of the gap forming surface of the object  200  in the measuring range is measured.  
         [0171]    In the case of the shape measuring apparatus that is the fourth embodiment, processing to be performed at steps S 12  to S 14  is performed over a measuring range of the object  200  after step S 11  illustrated in FIG. 13. Thus, a plurality of gap values of gaps formed between the transparent plate-like element  7  and the object  200  are determined. Subsequently, the gap-value-to-shape conversion means  17  converts the determined gap value into data representing a change in the shape of the gap forming surface of the object  200 , so that the shape of the gap forming surface of the object  200  in the measuring range is measured.  
         [0172]    According to the gap measuring apparatus of the invention and the shape measuring apparatus of this embodiment thereof, a gap of a transparent liquid crystal cell having a micro-gap and a minute change in the shape of a member can be measured at a high speed with an accuracy of about several nanometers.  
         [0173]    Further, each of the optical systems of the gap measuring apparatuses according to the invention and the shape measuring apparatuses of this embodiment thereof is configured so that the two light waves forming the interference fringes pass through the same optical path. Thus, even when a shock is given thereto, the optical path difference between theses light waves is always stable, and the measuring accuracy thereof can be maintained.  
         [0174]    Incidentally, although the wavelength scanning is performed at every nanometer in the range of wave length from 450 nm to 550 nm according to the mode for carrying out the invention or the embodiments thereof, such values can be suitably determined. However, a higher accuracy measurement is enabled by obtaining about 100 image data at one point.  
         [0175]    Further, although the reference data is preliminarily calculated and stored in the reference data memory  14  according to the mode for carrying out the invention or to the embodiments, means for calculating the reference data may be provided in the apparatuses.  
         [0176]    Furthermore, although the image memory, the correction data memory, and the reference data memory of each of the embodiments are illustrated as different memories, these memories may be constituted as one memory (or unit).  
         [0177]    Additionally, programs for performing the functions of the gap value determination means  15 , the gap-value-to-shape conversion means  17 , or of the gap value determination means  16  and the gap-value-to-shape conversion means  17  may be executed by the same CPU.  
         [0178]    Finally, an example of a process of manufacturing a liquid crystal device utilizing the gap measuring method or apparatus according to the invention is described hereinbelow with reference to FIG. 21.  
         [0179]    At step A, first, necessary circuits are formed on an upper substrate  321  and a lower substrate  331  by using photolithography. For example, a common electrode  322  is formed on the upper substrate  321 , while a thin film transistor  332  is formed on the lower substrate  331 . Incidentally, elements formed at this step are changed according to the kind of the liquid crystal device.  
         [0180]    Subsequently, at step B, an oriented film  323  is formed on the upper substrate  321 , on which the common electrode  322  is formed. Then, rubbing is performed thereon. Moreover, similarly, an oriented film  333  is formed on the lower substrate  331 , on which a thin film transistor  332  is formed, then rubbing is performed thereon.  
         [0181]    Subsequently, at step C, a sealing material  324  for sealing the light crystal is applied to one of the substrates, for instance, the upper substrate  321 . Further, a gap material  334  is sprayed onto the oriented film  333  formed on the lower substrate  331 . Incidentally, the manner of application of the sealing material and spraying of the gap material is not limited to the aforementioned manner. It is possible that the sealing material is applied to and the gap material is sprayed onto one of the substrates.  
         [0182]    Then, at step D, a panel  400  is manufactured by sticking the two substrates  325  and  335  made at steps A to C to each other. Further, the gap formed in this panel  400  is measured by using the aforementioned gap measuring method or apparatus. Moreover, if is checked whether or not the gap value of the gap is within a prescribed range.  
         [0183]    Subsequently, at step E serving as a first breaking step, a strip-like panel  410  is manufactured by parting the panel  400  verified as being within the prescribed range.  
         [0184]    Then, at step F, liquid crystal is injected into the gap through a liquid crystal injecting portion of the strip-like panel  410 . Subsequently, the liquid crystal is sealed by a liquid crystal sealing material  350 .  
         [0185]    Moreover, at step G serving as a second breaking step, a panel  420 , whose size is equal to that of one panel of a product, is formed by parting the strap-like panel  410 , in which the liquid crystal is sealed. Then, a driver IC  360  is mounted on the panel  420 . Thus, a liquid crystal device is completed.  
         [0186]    According to the methods and apparatuses of the invention, a measurement of each of a gap with width or shape of the object can be performed at a high speed with high accuracy without moving the object or apparatus.  
         [0187]    Further, in manufacturing a liquid crystal device, a gap in which liquid crystal is injected is checked at once, so that the manufacturing efficiency of a liquid crystal device is improved.  
         [0188]    Although the preferred embodiments of the present invention have been described above, it should be understood that the present invention is not limited thereto and that other modifications will be apparent to those skilled in the art without departing from the sprint of the invention.  
         [0189]    The scope of the present invention, therefore, should be determined solely by the appended claims.