Patent Publication Number: US-10788318-B2

Title: Three-dimensional shape measurement apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. patent application Ser. No. 15/735,021, filed Dec. 8, 2017 (currently pending), the disclosure of which is herein incorporated by reference in its entirety. The U.S. patent application Ser. No. 15/735,021 is a national entry of International Application No. PCT/KR2016/005891, filed on Jun. 3, 2016, which claims priority to Korean Application No. 10-2015-0080284 filed on Jun. 8, 2015, the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a three-dimensional shape measurement apparatus. More particularly, the present invention relates to a three-dimensional shape measurement apparatus measuring a three-dimensional shape based on height. 
     BACKGROUND ART 
     Generally, at least one printed circuit board (PCB) is employed in an electronic device, and various shaped elements are mounted on the PCB. In order to inspect defects of these elements, a three-dimensional shape measurement apparatus is typically used. 
     A conventional three-dimensional shape measurement apparatus illuminates light to a measurement target such as a PCB by using an imaging optical system, and image-captures a reflection image thereof using a camera. Then, a three-dimensional shape based on the height of the measurement target is measured using the captured reflection image. 
     Conventional imaging optical systems may be configured in various configurations. An optical triangulation method, a stereo method, etc. among the various configurations may be employed in the imaging optical system. 
     The optical triangulation method is a method using such as a bucket algorithm after acquiring a grating pattern, and widely used at present. However, this method has a problem that the height that is measurable is restricted by a pitch of a grating generating the pattern image. 
     The stereo method uses a stereo camera. Just as a person&#39;s perspective to an object can be perceived by synthesizing information input through two eyes into distance information, a stereo camera may also calculate three-dimensional distance information by capturing images from two cameras. 
     That is, a three-dimensional shape may be measured by using two or more images obtained by photographing at different positions. Particularly, in the two images including texture of a measurement target on a real space, position information of the measurement target in the real space of the measurement target is obtained by using a geometric structure based on the texture, to thereby measure the three-dimensional shape of the measurement target. 
     Thus, in case that the measurement target has texture, the three-dimensional shape of the measurement target may be measured based on the texture, but in case that the surface of the measurement target is smooth, since it is impossible to use a geometric structure based on the texture of the measurement target, the stereo method may be unavailable. 
     DISCLOSURE 
     Technical Problem 
     Accordingly, the present invention provides a three-dimensional shape measurement apparatus capable of measuring a three-dimensional shape of a measurement target by using a stereo method even though there is no texture or unclear texture. 
     Technical Solution 
     According to an exemplary embodiment of the present invention, a three-dimensional shape measurement apparatus includes a plurality of main pattern illumination parts, a plurality of main image-capturing parts and a control part. The main pattern illumination parts obliquely illuminate grating pattern light in different directions toward a measurement target. The main image-capturing parts obtain a grating pattern image of the measurement target by receiving reflection light of the grating pattern light that is illuminated from the main pattern illumination parts to the measurement target and obliquely reflected by the measurement target. The control part produces height data of the measurement target by using grating pattern images of the measurement target, or produces height data of the measurement target by using image positions of plane images for the measurement target and texture information of the measurement target. The control part employs a grating pattern illuminated on the measurement target as the texture information to produce height data of the measurement target. 
     In an exemplary embodiment, the three-dimensional shape measurement apparatus may further include an illumination part illuminating light toward the measurement target. The plurality of main image-capturing parts obtain a plane image of the measurement target by receiving reflection light of the light that is illuminated from the illumination part to the measurement target and reflected by the measurement target. 
     In an exemplary embodiment, the plane images of the measurement target may be image-captured without the grating pattern light or obtained by averaging the grating pattern images. 
     In an exemplary embodiment, the grating pattern may be employed as the texture information to produce the height data of the measurement target in case that there is no texture information of the measurement target. 
     In an exemplary embodiment, the control part may produce the height data of the measurement target by using the grating pattern images of the measurement target with respect to less than a reference height, and produce the height data of the measurement target by using the image positions of the plane images for the measurement target and the texture information of the measurement target with respect to the reference height or higher. For example, the reference height may be less than or equal to a measurable height according to the grating pattern light of the main pattern illumination parts. Meanwhile, at least two of the main pattern illumination parts may include gratings having different grating pitches to generate grating pattern lights having different equivalent wavelengths, and the reference height may be less than or equal to an integrated measurable height according to the different equivalent wavelengths. 
     In an exemplary embodiment, the three-dimensional shape measurement apparatus may further include a top pattern illumination part disposed over the measurement target to perpendicularly illuminate grating pattern light toward the measurement target. 
     In an exemplary embodiment, the three-dimensional shape measurement apparatus may further include a top image-capturing part disposed over the measurement target to obtain the grating pattern image of the measurement target by receiving reflection light of the grating pattern light that is perpendicularly reflected by the measurement target. The control part may produce the height data of the measurement target by using the grating pattern image obtained between the top image-capturing part and each main image-capturing part. 
     In an exemplary embodiment, the main pattern illumination parts may be spaced apart from each other along circumferential direction around the measurement target, and the main image-capturing parts may be spaced apart from each other along circumferential direction about the measurement target. Herein, the main pattern illumination parts and the main image-capturing; parts may form one set and may be arranged in correspondence with each other. 
     According to another exemplary embodiment of the present invention, a three-dimensional shape measurement apparatus includes a plurality of main pattern illumination parts, a plurality of main image-capturing parts and a control part. The main pattern illumination parts obliquely illuminates grating pattern light in different directions toward a measurement target. The main image-capturing parts obtain a grating pattern image of the measurement target by receiving reflection light of the grating pattern light that is illuminated from the main pattern illumination parts to the measurement target and obliquely reflected by the measurement target. The control part produces height data of the measurement target by selectively applying a first method of producing the height data of the measurement target by using the grating pattern image of the measurement target, a second method of producing the height data of the measurement target by using image positions of plane images for the measurement target and texture information of the measurement target, and a third method of producing the height data of the measurement target by utilizing the grating pattern illuminated on the measurement target as the texture information of the measurement target. 
     For example, the control part may determine which of the first, second, and third methods to apply. 
     Advantageous Effects 
     According to the present invention, in measuring a three-dimensional shape of a measurement target, an optical triangulation method and a stereo measurement method are both or selectively used, in which grating pattern illuminated on the measurement target may be used as texture information of the measurement target in case that it is difficult to utilize the texture information, to thereby measure the three-dimensional shape more easily and accurately. 
     In addition, in duality based on a predetermined reference height, the optical triangulation method may be used for less than the reference height to produce height data, and the stereo measurement method may be used for greater than or equal to the reference height to produce height data, to thereby maintain measurement accuracy at low height while extending a range of measurable heights. 
     In addition, by generating grating pattern light from multiple pattern illumination parts and capturing grating pattern images in multiple image-capturing parts, more accurate and precise three-dimensional shape measurement may be available at various directions and angles according to an optical triangulation method and a stereo measurement method. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a front view schematically showing a three-dimensional shape measurement apparatus according to an exemplary embodiment of the present invention. 
         FIG. 2  is a plan view of the three-dimensional shape measurement apparatus shown in  FIG. 1 . 
         FIG. 3  is a conceptual view for explaining a process of measuring the three-dimensional shape by using a stereo method in the control part of the three-dimensional shape measurement apparatus in  FIG. 1 . 
         FIG. 4  is a plan view of a three-dimensional shape measurement apparatus according to another exemplary embodiment of the present invention. 
         FIG. 5  is a plan view of a three-dimensional shape measurement apparatus according to still another exemplary embodiment of the present invention. 
         FIG. 6  is a plan view of a three-dimensional shape measurement apparatus according to still another exemplary embodiment of the present invention. 
         FIG. 7  is a plan view of a three-dimensional shape measurement apparatus according to still another exemplary embodiment of the present invention. 
     
    
    
     MODE FOR INVENTION 
     The present invention is described more fully hereinafter with reference to the accompanying drawings, in which example embodiments of the present invention are shown. The present invention may, however, be embodied in many different forms and should not be construed as limited to the example embodiments set forth herein. Rather, these example embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. In the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. 
     It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, or section discussed below could be termed a second element, component, or section without departing from the teachings of the present invention. 
     The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. 
     It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Hereinafter, with reference to the drawings, preferred embodiments of the present invention will be described in detail. 
       FIG. 1  is a front view schematically showing a three-dimensional shape measurement apparatus according to an exemplary embodiment of the present invention.  FIG. 2  is a plan view of the three-dimensional shape measurement apparatus shown in  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , a three-dimensional shape measurement apparatus  100  according to an exemplary embodiment of the present invention may include a plurality of main pattern illumination parts  110   a , a plurality of main image-capturing parts  120   a , and a control part  130 , etc. 
     The main pattern illumination parts  110   a  obliquely illuminate grating pattern light PL in different directions towards the measurement target  10 . In other words, the main pattern illumination parts  110   a  may illuminate the grating pattern light PL for obtaining three-dimensional shape information of the measurement target  10  with the grating pattern light PL being inclined with respect to a normal perpendicular to the plane of the measurement target. 
     The measurement target  10  may include solder or components formed on a board  20  such as a printed circuit board (PCB). The board  20  may be disposed and supported on a stage  30 . The stage  30  may transfer the measurement target  10  to a measurement position by a transfer device (not shown). 
     In one embodiment, the main pattern illumination parts  110   a  may illuminate the grating pattern light PL toward the measurement target  10  by N times, and a grating pattern may be transferred N times by using a grating transfer instrument or by using a pattern image of a liquid crystal display (LCD) device to illuminate a phase-shifted grating pattern light. In the main image-capturing part  120   a  described later, grating pattern images according to illuminated grating pattern lights PL may be obtained. 
     In one embodiment, each of the main pattern illumination parts  110   a  may include a light source  112 , a grating  114 , a grating transfer instrument  116 , and a projection lens portion  118 . 
     The light source  112  illuminates light towards the measurement target  10 . The grating  114  converts the light emitted from the light source  112  into the grating pattern light PL. The grating  114  is moved N times by 2π/N through the grating transfer instrument  116 , for example, such as a piezo actuator (PZT), so as to generate a phase-shifted grating pattern light PL (N is a natural number not less than 2). The projection lens portion  118  projects the grating pattern light PL generated by the grating  114  onto the measurement target  10 . The projection lens portion  118  may include, for example, a plurality of lens combinations, and focuses the grating pattern light PL formed through the grating  114  onto the measurement target  10 . Thus, each main pattern illumination part  110  provides the grating pattern light PL to the measurement target  10  at each transfer, while transferring the grating  114  N times. 
     In one embodiment, the three-dimensional shape measurement apparatus  100  may include four main pattern illumination parts  110   a , as shown in  FIG. 2 . The four main pattern illumination parts  110   a  may be spaced apart from each other around the measurement target  10  in the circumferential direction or arranged at respective vertexes of a polygon around the measurement target  10 , when the measurement target  10  is viewed in a plan view. Thus, the main pattern illumination parts  110   a  may be provided in various numbers, for example, such as two, four, eight, etc. 
     The main image-capturing parts  120   a  capture a grating pattern image of the measurement target  10  by receiving reflection light RL of grating pattern light, which is illuminated from the main pattern illumination parts  110   a  and obliquely reflected by the measurement target  10 . 
     In one embodiment, each of the main image-capturing parts  120   a  may include a camera  122  and an imaging lens  124 . For example, the camera  122  may employ a CCD or a CMOS camera. The reflection light RL of the grating pattern light, which is reflected from the measurement target  10  may be imaged by the imaging lens  124  and captured by the camera  122 . 
     In one embodiment, the three-dimensional shape measurement apparatus  100  may include four main image-capturing parts  120   a , as shown in  FIG. 2 . The four main image-capturing parts  120   a  may be spaced apart from each other around the measurement target  10  in the circumferential direction or arranged at respective vertexes of a polygon around the measurement target  10 , when the measurement target  10  is viewed in a plan view. Thus, the main image-capturing parts  120   a  may be provided in various numbers, for example, such as two, four, eight, etc. 
     The main pattern illumination parts  110   a  and the main image-capturing parts  120   a  may be disposed alternately with each other, as shown in  FIG. 2 . In one embodiment, the four main pattern illumination parts  110   a  and the four main image-capturing parts  120   a  may be alternately and equally spaced apart from each other at eight positions around the circumference, when the measurement target  10  is viewed in a plan view. In  FIG. 2 , the main pattern illumination parts  110   a  and the main image-capturing parts  120   a  are arranged along the circumference of the same circle when viewed in a plan view, but alternatively it is obvious that the main image-capturing parts  120   a  and the main image capturing parts  120   a  may be disposed along the circumference of the circles of respectively different radii. 
     When the main pattern illumination parts  110   a  and the main image-capturing parts  120   a  are alternately disposed as described above, the grating pattern images that are formed by the grating pattern lights PL generated from the main pattern illumination parts  110   a  may be sequentially or simultaneously captured by all of the main image-capturing parts  120   a.    
     Meanwhile, the main pattern illumination parts  110   a  and the main image-capturing parts  120   a  may optionally employ optical path changing elements such as a mirror, so that substantial placement positions may be configured as the above, even though actual placement positions are somewhat different from the above. 
     The control part  130  produces height data of the measurement target  10 . 
     Particularly, the control part  130  may produce the height data of the measurement target  10  by using the grating pattern images of the measurement target  10  captured in the main image-capturing parts  120   a . That is, the control part  130  may produce the height data of the measurement target  10  by using an optical triangulation method. For example, the control part  130  may apply the well-known bucket algorithm to the grating pattern images captured in the main image-capturing parts  120   a , to obtain the height data of the measurement target  10 . 
     Also, the control part  130  may produce the height data of the measurement target  10  by using the image position of the plane images of the measurement target  10  and texture information of the measurement target  10 . That is, the control part  130  may produce the height data of the measurement target  10  by using a stereo method. 
       FIG. 3  is a conceptual view for explaining a process of measuring the three-dimensional shape by using a stereo method in the control part of the three-dimensional shape measurement apparatus in  FIG. 1 . 
     Referring to  FIG. 3 , the measurement target  10  applies a triangular technique to the image position of the measurement target  10  based on an image obtained from at least two image-capturing parts  120   a , to thereby obtain the height data of the measurement target  20 . 
     As shown in  FIG. 3 , the imaging lenses  124  are disposed at a predetermined distance B, and distances D 1  and D 2  imaged on the image-capturing elements  122   a  of the cameras  122  are measured based on the center axis CA of the imaging lenses  124 . Meanwhile, when the focal length of the imaging lens  124  is ‘f’, a relationship between the distances and the focal length satisfies Equation 1.
 
 S 1= fB/|D 1 −D 2|  [Equation 1]
 
     Therefore, since a distance S 1  from the imaging lens  124  to the measurement target  10  may be known, the height data of the measurement target  10  may be obtained. 
     Based on the same principle, the control part  130  may obtain the height data of the measurement target  10  from the plane images of the measurement target  10  by using a stereo method. 
     Herein, at least two plane images captured at different positions, such as the above, may use the texture information of the measurement target  10  to find a matching point indicating the same point in an actual space. 
     Herein, the grating pattern illuminated on the measurement target ( 10 ) may be used as the texture information. For example, when the surface of the measurement target ( 10 ) is smooth, the texture information may not be obtained, and thus in case that the texture information may not be obtained, the grating pattern illuminated on the measurement target  10  may be utilized. 
     Accordingly, in case that there is texture information in the measurement target  10 , the texture information may be applied to a stereo method to obtain the height data of the measurement target  10 , and in case that there is no texture information in the measurement target  10 , the grating pattern illuminated on the measurement target may be employed as the texture information, which is applied to a stereo method, to thereby obtain the height data of the measurement target  10 . Of course, even though there is texture information in the measurement target  10 , the grating pattern illuminated on the measurement target  10  may be used as the texture information. In addition, since the plane image of the measurement target  10  may be obtained in units of a field of view of the main image-capturing part  120   a , only a part of the field of view of the measurement target  10  has no texture information, the grating pattern illuminated on the measurement target  10  may be used as the texture information for the corresponding field of view. 
     The three-dimensional shape measurement apparatus  100  may further include an illumination part  140  for acquiring a two-dimensional plane image of the measurement target  10 . The illumination part  140  is disposed over the board  20  to illuminate light L toward the measurement target  10 . For example, the illumination part  140  may include a plurality of illumination units  142  arranged in a circle with respect to a central axis passing through the center of the measurement target  10  when viewed in a plan view. For example, the illumination part  140  may illuminate a plurality of different color lights at different inclination angles, each of which may have LED light continuously arranged to have a ring shape, thereby generating monochromatic illumination. 
     The main image-capturing parts  120   a  obtain a plane image of the measurement target  10  by receiving reflection light RL of the light, which is illuminated from the illumination part  140  and reflected by the measurement target  10 . The control part  130  may obtain the height data of the measurement target  10  by using the stereo method from the plane images of the measurement target  10  obtained as described above. 
     Alternatively the plane images of the measurement target  10  may be obtained by averaging the grating pattern images. Particularly, N grating pattern images may be acquired by grating pattern light PL generated in any one of the main pattern illumination parts  110   a , and brightness values of the N grating pattern images are summed and divided by N for each pixel, to thereby obtain a plane image of the measurement target  10  having an average value of brightness values per pixel. 
     The control part  130  may produce the height data of the measurement target  10  by using the grating pattern images of the measurement target  10  captured in the main image capturing parts  120   a , and in this case, since the reflection lights RL of the grating pattern lights PL generated in the ‘m’ main pattern illumination parts  110   a  are captured in the ‘n’ main image-capturing parts  120   a , the height data of the measurement target  10  may be produced as m×n. In addition, the control part  130  may produce the height data of the measurement target  10  by using the image position of the plane images of the measurement target  10  and the texture information of the measurement target  10 , and in this case, since a stereo method may be applied by using the plane images obtained from the two image-capturing parts  120   a  of the ‘n’ main image-capturing parts  120   a , the height data of the measurement target  10  may be produced as n(n−1)/2. 
     As described above, the height data of the measurement target  10  may be obtained in plurality for any one point, so that the plurality of height data may be selectively used or processed to obtain final height data. Also, the control part  130  may produce the height data by selectively applying a first method of producing the height data of the measurement target  10  by using the grating pattern images of the measurement target  10 , a second method of producing the height data of the measurement target  10  by using the image position of the plane images of the measurement target  10  and the texture information of the measurement target  10 , and a third method of producing the height data of the measurement target  10  by utilizing the grating pattern illuminated on the measurement target  10  as the texture information of the measurement target  10 . Herein, the control part  130  may determine which of the first, second, and third methods to apply, and may determine to apply two or more of the methods. 
     That is, three-dimensional shapes using the methods may be matched with respect to one measurement target, and a more precise three-dimensional shape measurement may be available. 
     For example, the control part  130  may select images or image pixels with high reliability among the grating pattern images captured by the main image-capturing parts  120   a , and combine the selected images or image pixels, to obtain the height data of the measurement target  10 . 
     The reliability may include at least one of brightness, visibility, signal-to-noise ratio (SNR), the measurement range (λ) corresponding to each grating pitch of the grating pattern lights PL, and relative position information between each main image-capturing part  120   a  and each main pattern illumination part  110   a.    
     Depending on the location of the measurement target  10  in the captured grating pattern image, a shadow region and a saturation region may occur. These shadow region and saturation region are regions having low reliability, and may be excluded when the height data of the measurement target  10  is acquired. For example, the shadow region may be defined as an area in which average brightness is less than a reference brightness value and visibility or SNR is less than a reference value, and the saturation region may be defined as an area in which average brightness is greater than a reference brightness value and visibility or SNR is less than a reference value. The remaining regions except the shadow region and the saturation region may be defined as a non-saturation region, and the non-saturation region may be included in obtaining the height data of the measurement target  10  as a region having high reliability. 
     In addition, the shadow region and the saturation region may be generated differently depending on the relative positions between the main image-capturing part  120   a  and the main pattern illumination part  110   a . For example, two main pattern illumination parts  110   a  adjacent to one main image-capturing part  120   a  and two main pattern illumination parts  110   a  not adjacent to the one main image-capturing part  120   a  form different shadow regions and saturation regions. Therefore, the reliability may be set by the relative position information between each main image-capturing part  120   a  and each main pattern illumination part  110   a.    
     In addition, since the grating pitch of the main pattern illumination parts  110   a  may determine a measurement range, that is, a measurable height, the reliability of the height data may vary depending on the height of the measurement target  10 . Therefore, the reliability may be set based on the grating pitch and the height information of the measurement target  10 . 
     Meanwhile, the control part  130  may set a reference height and produce the height data in duality based on the reference height. Particularly, the control part  130  may produce the height data of the measurement target  10  by using the grating pattern images of the measurement target  10  for less than the reference height, and may produce the height data of the measurement target  10  by using the image position of the plane images of the measurement target  10  and the texture information of the measurement target  10  for greater than the reference height. 
     Herein, the reference height may be less than or equal to the measurable height according to the grating pattern light PL of the main pattern illumination parts  110   a . The measurable height according to the grating pattern light PL means a height, measurement of which is possible, defined by the grating pitch that produces the grating pattern light, as described above. 
     When the main pattern illumination parts  110   a  employ multiple wavelengths, at least one of the main pattern illumination parts  110   a  may have a different grating pitch, or one main pattern illumination part  110   a  may have two or more different grating pitches. For example, at least two of the main pattern illumination parts  110   a  may include gratings  114  having different grating pitches, to respectively generate grating pattern light PL having an equivalent wavelength different from each other. In this case, the reference height may be set to less than or equal to an integrated measurable height according to the different equivalent wavelengths. 
     In this way when producing the height of the measurement target  10  in duality, the height of the measurement target  10  may be obtained by the height measurement method of the stereo method having a wide range of the measurable height at the height higher than or equal to the reference height, and the height of the measurement target  10  may be obtained by the height measurement method of the optical triangulation method at the height lower than the reference height. 
     The control part  130  may be a device capable of performing image processing, shape information processing, calculation, and the like, and may include, for example, a computer. The control part  130  may control the operation of the above components such as the main pattern illumination parts  110   a  and the main image-capturing parts  120   a.    
     In one embodiment, the control part  130  may control the main pattern illumination part  110   a , so that the main image-capturing parts  120   a  capture an image at the same time while projecting the grating pattern light PL onto the measurement target  10 . Alternatively, the control part  130  may control that only a main image-capturing part  120   a  not adjacent to one main pattern illumination part  110   a  captures the grating pattern light PL projected onto the measurement target  10 . 
     Meanwhile, each main image-capturing; part  120   a  captures a grating pattern image with being inclined at a predetermined angle in a vertical direction to the measurement target  10 , and thus some distortion may be generated as compared with the case of capturing a grating pattern image in a vertical direction to the measurement target  10 . Accordingly, the control part  130  may acquire a two-dimensional image or a three-dimensional image captured at the upper portion on the basis of a normal perpendicular to the plane of the measurement target  10  in advance, and then correction of capturing distortion may be performed. The pre-acquired image may be obtained for the measurement target  10  or for a predetermined specimen. 
       FIG. 4  is a plan view of a three-dimensional shape measurement apparatus according to another exemplary embodiment of the present invention. 
     Referring to  FIG. 4 , a three-dimensional shape measurement apparatus  101  according to another exemplary embodiment of the present invention may include a plurality of main pattern illumination parts  110   a , a plurality of main image-capturing parts  120   a , a control part  130  (refer to  FIG. 1 ), a plurality of beam-splitting parts (not shown), etc. 
     The three-dimensional shape measurement apparatus  101  is substantially the same as the three-dimensional shape measurement apparatus  100  shown in  FIGS. 1 and 2  except for the placement configuration of the main pattern illumination parts  110   a  and the main image-capturing parts  120   a , and including the beam-splitting parts. Thus, detailed description thereof will be omitted. 
     As shown in  FIG. 4 , the main pattern illumination parts  110   a  and the main image-capturing parts  120   a  may be spaced apart from each other around the measurement target  10  in the circumferential direction or arranged at respective vertexes of a polygon around the measurement target  10 . The main pattern illumination parts  110   a  and the main image-capturing parts  120   a  may be disposed in correspondence with each other. Accordingly, as shown in  FIG. 4 , the main pattern illumination part  110   a  and the main image-capturing part  120   a  that correspond to each other form a set. 
     The three-dimensional shape measurement apparatus  101  may include a beam-splitting part (not shown), for example, a beam splitter. 
     The beam-splitting part is disposed corresponding to the main pattern illumination part  110   a  and the main image-capturing part  120   a  forming a set. The beam-splitting part transmits the grating pattern light PL generated from the main pattern illumination part  110   a  toward the measurement target  10 , and separates reflection light RL that are emitted from the main pattern illumination parts  110   a  and reflected by the measurement target  10 , to thereby provide the reflection light RL to the main image-capturing part  120   a.    
     In the three-dimensional shape measurement apparatus  101 , since the main pattern illumination part  110   a , the main image-capturing part  120   a  and the beam-splitting part are formed to correspond to each other, more compact arrangement of the apparatus and more effective three-dimensional shape measurement of the measurement target  10  may be available. 
     In this case, the reflection light RL of the grating pattern light PL emitted by one main pattern illumination part  110   a  may be image-captured by all of the main image-capturing parts  120   a , or by main image-capturing parts  120   a  except for only a main image-capturing part forming the same set with the one main pattern illumination part  110   a . In case of capturing by all of the main image-capturing parts  120   a , the grating pattern image captured in the main image-capturing part forming the same set with the one main pattern illumination part  110   a  may be excluded from producing the height data. The operation control and calculation control of the main image-capturing part  120   a  may be performed by the control part  130 . 
       FIG. 5  is a plan view of a three-dimensional shape measurement apparatus according to still another exemplary embodiment of the present invention. 
     Referring to  FIG. 5 , a three-dimensional shape measurement apparatus  102  according to still another exemplary of the present invention may include a plurality of main pattern illumination parts  110   a , a plurality of main image-capturing parts  120   a , a control part  130  (refer to  FIG. 1 ), a top pattern illumination part  110   b , etc. The three-dimensional shape measurement apparatus  102  is substantially the same as the three-dimensional shape measurement apparatus  100  shown in  FIG. 1  and  FIG. 2  except for including the top pattern illumination part  110   b . Thus, detailed description thereof will be omitted. 
     The top pattern illumination part  110   b  is disposed over the measurement target  10  (refer to  FIG. 1 ), and may vertically provide the grating pattern light PL (refer  FIG. 1 ) toward the measurement target  10 . The grating pattern light PL according to the top pattern illumination part  110   b  may be simultaneously captured by the main image-capturing parts  120   a  after being reflected by the measurement target  10 . 
     Meanwhile, the top pattern illumination part  110   b  may optionally employ optical path changing elements such as a mirror, so that substantial placement positions may be configured as the above, even though actual placement positions are somewhat different from the above. 
     Thus, since the three-dimensional shape measurement apparatus  102  has the top pattern illumination part  110   b , the grating pattern light PL is provided perpendicular to the measurement target  10 . Thus, a more accurate three-dimensional shape measurement for the measurement target  10  may be available. 
       FIG. 6  is a plan view of a three-dimensional shape measurement apparatus according to still another exemplary embodiment of the present invention. 
     Referring to  FIG. 6 , a three-dimensional shape measurement apparatus  103  according to still another exemplary of the present invention may include a plurality of main pattern illumination parts  110   a , a plurality of main image-capturing parts  120   a , a control part  130  (refer to  FIG. 1 ), a top pattern illumination part  110   b , a top image-capturing part  120   b , etc. The three-dimensional shape measurement apparatus  103  is substantially the same as the three-dimensional shape measurement apparatus  102  shown in  FIG. 5  except for including the top image-capturing part  120   b . Thus, detailed description thereof will be omitted. 
     The top pattern illumination part  120   b  is disposed over the measurement target  10  (refer to  FIG. 1 ), and may capture the grating pattern image that is formed by a process, in which the grating pattern light PL (refer to  FIG. 1 ) is emitted from at one of the main pattern illumination parts  110   a  and the top pattern illumination part  110   b , and vertically reflected by the measurement target  10 , to thereby form the grating pattern image. 
     In addition, when the illumination part  140  (refer  FIG. 1 ) is provided, the top image-capturing part  120   b  may capture a two-dimensional plane image that is formed by a process, in which light emitted from the illumination part  140  and vertically reflected by the measurement target  10 , to thereby form the two-dimensional plane image. 
     That is, the top image-capturing part  120   b  may image-capture the grating pattern light PL emitted from the top pattern illumination part  110   b  and then average the captured grating pattern images to generate a two-dimensional plane image in which a grating pattern is removed, and capture a two-dimensional plane image that is formed by a process in which light emitted from the illumination part  140  and vertically reflected by the measurement target  10 , to thereby form the two-dimensional plane image. Thus, two-dimensional inspection may be performed based on at least one two-dimensional plane image generated or captured, and the imaging distortion of the measurement target  10  captured by the image-capturing parts  120   a  may be easily corrected. 
     The three-dimensional shape measurement apparatus  103  may include a beam-splitting part (not shown), for example, a beam splitter. The beam-splitting part transmits the grating pattern light PL generated from the top pattern illumination part  110   b  toward the measurement target  10 , and reflects at least one of the reflection lights RL that are emitted from the plurality of main pattern illumination parts  110   a  and the top pattern illumination part  110   b  and reflected by the measurement target  10 , to the top image-capturing part  120   b.    
     Meanwhile, the top image-capturing part  120   b  may optionally employ optical path changing elements such as a mirror, so that substantial placement positions may be configured as the above, even though actual placement positions are somewhat different from the above. 
     In  FIG. 6 , although it is described that the top image-capturing part  120   b  and the top pattern illumination part  110   b  are provided together, only the top image-capturing part  120   b  may be provided without the top pattern illumination part  110   b.    
     Thus, since the three-dimensional shape measurement apparatus  103  has the top image-capturing part  120   b , the grating pattern light PL that is vertically reflected is obtained. Thus, a more accurate three-dimensional shape measurement for the measurement target  10  may be available. 
     Meanwhile, the grating pattern illuminated on the measurement target  10  may be used as the texture information, so that the height data of the measurement target  10  may be also obtained by a stereo method between the top image-capturing part  120   b  and each main image-capturing part  120   a , by which the three-dimensional shape may be measured. Thus, for each field of view (FOV) of the image-capturing part, measurement location or height of the measurement target, main/top illumination parts, main/top image-capturing parts may be selectively image-captured, or an image having high reliability may be selected from captured images, to thereby produce a more accurate three-dimensional shape. 
       FIG. 7  is a plan view of a three-dimensional shape measurement apparatus according to still another exemplary embodiment of the present invention. 
     Referring to  FIG. 7 , a three-dimensional shape measurement apparatus  104  according to still another exemplary of the present invention a include a plurality of main pattern illumination parts  110   a , a plurality of main image-capturing parts  120   a , a control part  130  (refer to  FIG. 1 ), a top pattern illumination part  110   b , a top image-capturing part  120   b , a plurality of beam-splitting parts (not shown), etc. The three-dimensional shape measurement apparatus  104  is substantially the same as the three-dimensional shape measurement apparatus  103  shown in  FIG. 6  except that the main pattern illumination parts  110   a , the main image-capturing parts  120   a  and the beam-splitting parts  150  are disposed corresponding to each other as shown in  FIG. 4 . Thus, detailed description thereof will be omitted. 
     Particularly, the three-dimensional shape measurement apparatus  104  employs the arrangement of the top pattern illumination part  110   b  and the top image-capturing part  120   b  shown in  FIG. 6 , and employs the arrangement of the main pattern illumination parts  110   a  and the main image-capturing parts  120   a  shown in  FIG. 4 . 
     Thus, it may be possible to include as many pattern illumination parts and image-capturing parts as possible, so that a more precise three-dimensional shape measurement for the measurement target  10  (refer to  FIG. 1 ) may be available. 
     Meanwhile, in various embodiments of the present invention described above, main/top illumination parts and main/top image-capturing parts arranged for height data acquisition of the measurement target  10  may be possible in various choices and combinations thereof for applying an optical triangulation method or a stereo method. For example, it may be possible to combine the main illumination parts or combine the main illumination part and the top illumination part for applying an optical triangulation method, and it may be also possible to combine main/top image-capturing parts that capture pattern illumination of the illumination parts, apart from the combination of the illumination parts, for applying an optical triangulation method. 
     In addition, it may be possible to combine main image-capturing parts or combine the main image-capturing part and the top image-capturing part for applying a stereo method. These selections and combinations may be based on various factors such as field of views (FOV) of the image-capturing part, measurement location, height of the measurement target, reliability of the captured image, etc. 
     According to the present invention described above, in measuring a three-dimensional shape of a measurement target, an optical triangulation method and a stereo measurement method are both or selectively used, in which grating pattern illuminated on the measurement target may be used as texture information of the measurement target in case that it is difficult to utilize the texture information, to thereby measure the three-dimensional shape more easily and accurately. 
     In addition, in duality based on a predetermined reference height, the optical triangulation method may be used for less than the reference height to produce height data, and the stereo measurement method may be used for greater than or equal to the reference height to produce height data, to thereby maintain measurement accuracy at low height while extending a range of measurable heights. 
     In addition, by generating grating pattern light from multiple pattern illumination parts and capturing grating pattern images in multiple image-capturing parts, more accurate and precise three-dimensional shape measurement may be available at various directions a angles according to an optical triangulation method and a stereo measurement method. 
     It will be apparent to those skilled in the art that various modifications and variations may be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.