Patent Publication Number: US-2022228854-A1

Title: Measurement device and measurement method

Description:
TECHNICAL FIELD 
     The present invention relates to a measurement device and a measurement method for measuring the shape of a measurement subject. 
     BACKGROUND ART 
     Conventionally, a measurement device for measuring the shape of the surface of a measurement subject has been developed. For example, Patent Document 1 (JP 2015-75452A) discloses the shape measurement device described below, as an example of such a measurement device. That is, a shape measurement device includes: a translucent optical component that has a reference surface that faces a surface of a sample; a light source that irradiates the surface of the sample with light that has a predetermined wavelength band and passes through the optical component; an imaging spectroscope that measures a reflection spectrum for each position in a linear region that is defined on the surface of the sample; and a calculation unit that calculates a distance between each position in the linear region and the reference surface based on the reflection spectrum measured for each position in the linear region. 
     Also, Patent Document 2 (JP 2012-7961A) discloses the shape measurement device described below. That is, a shape measurement device includes: a light projecting device that irradiates an uneven shape of a measurement subject with line light; an imaging device that captures an image of a light cutting line formed in the uneven shape by the light projecting device; a driving device that moves the light projecting device in a light emission axis direction thereof so that the width of the light cutting line is the smallest on an upper base and a lower base of the uneven shape; and a processing device that calculates a height or a depth of the uneven shape based on an image in which the width of the light cutting line is a minimum on the upper base of the uneven shape and an image in which the width of the light cutting line is a minimum on the lower base of the uneven shape, the images being captured by the imaging device. 
     CITATION LIST 
     Patent Documents 
     
         
         Patent Document 1: JP 2015-75452A 
         Patent Document 2: JP 2012-7961A 
       
    
     DISCLOSURE OF THE INVENTION 
     Problem to be Solved by the Invention 
     There is demand for a measurement device that is superior to the techniques described in Patent Document 1 and Patent Document 2, and makes it easier to measure the shapes of various measurement subjects. 
     The present invention has been made to solve the above-described problem, and aims to provide a measurement device and a measurement method that make it easier to measure the shapes of various measurement subjects. 
     Means for Solving the Problem 
     (1) To solve the above-described problem, a measurement device according to one aspect of the invention is the measurement device for measuring the shape of a measurement subject, the measurement device includes: a light source unit; a light receiving unit; and a main body that includes a light passing portion from which a line-shaped light ray is emitted, a light projection optical path that is an optical path extending from the light source unit to the light passing portion, and a light receiving optical path that is an optical path extending from the light passing portion to the light receiving unit. 
     As described above, with a configuration that includes the main body that includes the light passing portion, the light projection optical path, and the light receiving optical path, it is possible to radiate the measurement subject with the line-shaped light ray emitted from the light passing portion, in a state where the light passing portion faces the measurement subject. Therefore, for example, in a state where the measurement subject is placed on the main body such that the light passing portion and the measurement subject face each other, it is possible to measure the shape of the measurement subject, using the line-shaped light ray emitted from the light passing portion. Therefore, it is easier to measure the shapes of various measurement subjects. 
     (2) Preferably, the measurement further includes: a light projecting mirror that is provided on the light projection optical path; and a light receiving mirror that is provided on the light receiving optical path, wherein the light projecting mirror reflects light received from the light source unit so that the measurement subject is irradiated therewith through the light passing portion, and the light receiving mirror reflects at least some of the light received from the measurement subject through the light passing portion so that the light receiving unit is irradiated therewith. 
     With such a configuration, it is possible to freely design the light projection optical path and the light receiving optical path in the main body, using the light projecting mirror and the light receiving mirror. Therefore, it is possible to flexibly determine the shape and size of the main body according to the shape measurement of the measurement subject. 
     (3) More preferably, the measurement device further includes a half mirror that is provided at a position on the light projection optical path between the light source unit and the light projecting mirror. 
     With such a configuration, using the light projecting mirror and the half mirror, it is possible to irradiate a plurality of areas of the measurement subject with reflected light rays received from the light source, and simultaneously measure the shapes of the plurality of areas of the measurement subject. 
     (4) Preferably, the measurement device further includes an analysis unit that analyzes the shape of the measurement subject based on a light reception result of the light receiving unit, wherein the analysis unit further generates an image based on the light reception result of the light receiving unit, and detects an object other than the measurement subject based on an analysis result of the image thus generated. 
     With such a configuration, using the image of the area of the measurement subject irradiated with the line-shaped light ray, it is possible to detect the object such as foreign matter, based on the result of visual analysis of the area, for example. 
     (5) Preferably, the measurement device further includes an adjustment mechanism configured to adjust an incident angle of a light ray travelling from the light projection optical path to the light passing portion. 
     With such a configuration, it is possible to adjust the incident angle of the light ray travelling from the light projection optical path to the light passing portion. Therefore, it is possible to measure the shapes of a wider variety of measurement subjects. 
     (6) Preferably, the light passing portion is an opening, the main body further includes a transparent member that closes the opening, and the transparent member is provided on the other side of the measurement subject with respect to the opening. 
     As described above, with a configuration in which the transparent member closes the opening, it is possible to prevent dust or the like from entering the main body. In addition, with a configuration in which the transparent member is provided on the other side of the measurement subject with respect to the opening, it is possible to prevent the measurement subject located so as to face the opening from coming into contact with the transparent member. Therefore, in the case of measuring the shape of the measurement subject in a state where the measurement subject is placed over the opening, for example, it is possible to prevent the measurement subject from deforming under its own weight, and perform more accurate shape measurement. 
     (7) To solve the above-described problem, a measurement method according to one aspect of the invention is the measurement method carried out by a measurement device for measuring the shape of a measurement subject, the measurement device including a main body, the main body including a light passing portion, a light projection optical path, and a light receiving optical path, the measurement method includes: a step of irradiating the measurement subject with a line-shaped light ray that enters the light projection optical path or a line-shaped light ray that is generated on the light projection optical path, through the light passing portion; and a step of receiving a reflected light ray from the measurement subject, through the light passing portion and the light receiving optical path. 
     As described above, with a method that employs the measurement device that includes the light passing portion, the light projection optical path, and the light receiving optical path, to irradiate the measurement subject with the line-shaped light ray through the light passing portion and receive the reflected light ray from the measurement subject through the light passing portion and the light receiving, it is possible to irradiate the measurement subject with the line-shaped light ray, in a state where the light passing portion faces the measurement subject. Therefore, for example, in a state where the measurement subject is placed on the main body such that the light passing portion and the measurement subject face each other, it is possible to measure the shape of the measurement subject, using the line-shaped light ray emitted from the light passing portion. Therefore, it is easier to measure the shapes of various measurement subjects. 
     Effects of the Invention 
     With the present invention, it is easier to measure the shapes of various measurement subjects. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view showing a configuration of a measurement device according to an embodiment of the present invention. 
         FIG. 2  is a plan view showing light that is emitted from the opening of the measurement device according to the embodiment of the present invention, and with which the measurement subject is irradiated. 
         FIG. 3  is a diagram showing a light irradiation line that is formed in the measurement area, by the line light ray emitted from the measurement device according to the embodiment of the present invention, with which the measurement subject is irradiated. 
         FIG. 4  is a diagram showing a state in which the line light ray emitted from the measurement device according to the embodiment of the present invention so that the measurement subject is irradiated therewith is reflected by the surface of the measurement subject. 
         FIG. 5  is a diagram showing an example of an image generated by the analysis unit of the measurement device according to the embodiment of the present invention. 
         FIG. 6  is a diagram showing the result of the analysis of the surface shape of the measurement subject performed by the analysis unit of the measurement device according to the embodiment of the present invention. 
         FIG. 7  is a plan view showing an example of a measurement area that is to be irradiated with a line light ray emitted from the measurement device according to the embodiment of the present invention. 
         FIG. 8  is a diagram showing an example of the content of a measurement performed by the measurement device according to the embodiment of the present invention. 
         FIG. 9  is a diagram showing another example of the content of a measurement performed by the measurement device according to the embodiment of the present invention. 
         FIG. 10  is a side view showing a configuration of a measurement device according to a modification of the embodiment of the present invention. 
         FIG. 11  is a flowchart showing operation procedures that are performed by the measurement device according to the embodiment of the present invention when analyzing the surface shape of the measurement area of the measurement subject. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that, in the drawings, the same reference numerals are given to the same or corresponding components in the drawings, and redundant descriptions thereof are not repeated. Furthermore, at least parts of the embodiments described below may be suitably combined. 
     Configuration and Basic Operations 
       FIG. 1  is a side view showing a configuration of a measurement device according to an embodiment of the present invention. 
     As shown in  FIG. 1 , a measurement device  100  includes a main body  10 , a light source unit  20 , and a light receiving unit  30 . The measurement device  100  is a device for measuring the shape of a measurement subject  200 . The light source unit  20  and the light receiving unit  30  are provided inside the main body  10 , for example. The main body  10  is a housing in which the light source unit  20  and the light receiving unit  30  are provided, for example. 
     The main body  10  includes an opening  70 , a light projection optical path  51 , and a light receiving optical path  52 . The light projection optical path  51  is an optical path extending from the light source unit  20  to the opening  70 . The light receiving optical path  52  is an optical path extending from the opening  70  to the light receiving unit  30 . Due to light from the light source unit  20 , for example, a line-shaped light ray is emitted from the opening  70 . The opening  70  is an example of a light passing portion. 
     The light source unit  20  emits a line-shaped light ray with which the measurement subject  200  is irradiated, through the opening  70 , for example. More specifically, the light source unit  20  includes a light source and an optical member such as a laser line generator lens that converts the light output from the light source into a line-shaped light ray. The light source is not particularly limited, and is a laser light source or an LED (Light Emitting Diode) light source that outputs monochromatic light, for example. 
     The light receiving unit  30  receives the light reflected from the surface or the like of the measurement subject  200 , for example. More specifically, the light receiving unit  30  includes an imaging device such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor). 
     The measurement device  100  measures the shape of the measurement subject  200  in a state where the measurement subject  200  is positioned so as to be separated from the main body  10  as shown in  FIG. 1 , or in a state where the measurement subject  200  is positioned so as to be in contact with the surface in which the opening  70  of the main body  10  is formed. 
     For example, the measurement device  100  also includes a light projecting mirror  61 , a light receiving mirror  62 , an adjustment mechanism  80 , an analysis unit  40 , and a transparent member  71 . The analysis unit  40  is provided outside the main body  10 , for example. The adjustment mechanism  80  is provided inside the main body  10 , for example. Note that the light projecting mirror  61  may be a total reflection mirror or a half mirror. 
     The light projecting mirror  61  is provided on the light projection optical path  51  in the main body  10 . The light projection optical path  51 , which is an optical path extending from the light source unit  20  to the opening  70 , includes an optical path extending from the light source unit  20  to the light projecting mirror  61  and an optical path extending from the light projecting mirror  61  to the opening  70 . 
     The light receiving mirror  62  is provided on the light receiving optical path  52  in the main body  10 . The light receiving optical path  52 , which is an optical path extending from the opening  70  to the light receiving unit  30 , includes an optical path extending from the opening  70  to the light receiving mirror  62  and an optical path extending from the light receiving mirror  62  to the light receiving unit  30 . 
     The transparent member  71  closes the opening  70  of the main body  10 . The transparent member  71  is provided on the other side of the measurement subject  200  with respect to the opening  70 . For example, the width and the length of the surface that faces the opening  70 , of the transparent member  71 , are longer than the width and the length of the opening  70 , respectively. 
       FIG. 2  is a plan view showing light that is emitted from the opening of the measurement device according to the embodiment of the present invention, and with which the measurement subject is irradiated. 
     As shown in  FIGS. 1 and 2 , the light source unit  20  emits a line light ray L 1 , which is a line-shaped light ray, to the light projection optical path  51 . More specifically, the light source unit  20  emits the line light ray L 1  toward the light projecting mirror  61 . 
     The light projecting mirror  61  reflects the line light ray L 1  received from the light source unit  20 , and irradiates the measurement subject  200  with the line light ray L 1  through the transparent member  71  and the opening  70 . For example, the width of the opening  70  is longer than the length thereof in the extension direction of the line light ray L 1  that enters the opening  70 . The light projecting mirror  61  irradiates a measurement area  201  that is a measurement subject area of the surface of the measurement subject  200 , with the line light ray L 1  passing through the opening  70  and the transparent member  71 . Hereinafter, the length in the extension direction of the line light is also referred to as a line width. 
     More specifically, the line light ray L 1  reflected by the light projecting mirror  61  and emitted from the opening  70  and the transparent member  71  travels along an irradiation optical path  53  that is an optical path on an extension line of the light projection optical path  51  extending from the light projecting mirror  61  to the opening  70 , and is an optical path extending from the opening  70  to the measurement subject  200 , and the measurement area  201  is irradiated with the line light ray L 1 . 
       FIG. 3  is a diagram showing a light irradiation line that is formed in the measurement area, by the line light ray emitted from the measurement device according to the embodiment of the present invention, with which the measurement subject is irradiated.  FIG. 3  shows a plan view and a side view of the measurement subject  200 . 
     As shown in  FIG. 3 , the measurement subject  200  has an uneven shape that is constituted by a plurality of protrusions  1 A and a plurality of depressions  1 B that are arranged in the extension direction of the line light ray L 1 . 
     The line light ray L 1  emitted from the measurement device  100  input to the measurement area  201  enters the measurement area  201  of the measurement subject  200  at an incident angle θ 1 , and forms a light irradiation line L 3  in the measurement area  201 . 
     In the plan view, the light irradiation line L 3  formed on a protrusion  1 A and the light irradiation line L 3  formed on a depression  1 B have an interval corresponding to the incident angle θ 1  in a direction that is orthogonal to the extension direction of the line light ray L 1 . 
     More specifically, when the level difference between the protrusion  1 A and the depression  1 B in the measurement area  201  is a level difference d, the distance between the light irradiation line L 3  formed on the protrusion  1 A and the light irradiation line L 3  formed on the depression  1 B is d×tan θ 1  in a plan view. 
     The line light ray L 1  emitted from the main body  10  of the measurement device  100  so that the measurement area  201  of the measurement subject  200  is irradiated therewith is reflected from the measurement area  201 . At least some of the light reflected from the measurement area  201  travels along a reflection optical path  54  and enters the main body  10  via the opening  70  and the transparent member  71 . 
     The light receiving mirror  62  reflects some of the light received from the measurement subject  200  through the opening  70  so that the light receiving unit  30  is irradiated therewith. More specifically, the line light ray L 1  emitted from the main body  10  of the measurement device  100  so that the measurement area  201  of the measurement subject  200  is irradiated therewith is reflected and scattered. At least some of the light reflected and scattered by the measurement area  201  enters the main body  10  via the opening  70  and the transparent member  71 . The light receiving mirror  62  receives the light reflected and scattered by the measurement area  201 , and reflects the received light. At least some of the light reflected by the light receiving mirror  62  enters the light receiving unit  30 . Hereinafter, the light that is reflected by the light receiving mirror  62  and enters the light receiving unit  30 , of the light reflected and scattered by the measurement area  201 , is also referred to as a detection light ray L 2 . 
       FIG. 4  is a diagram showing a state in which the line light ray emitted from the measurement device according to the embodiment of the present invention so that the measurement subject is irradiated therewith is reflected by the surface of the measurement subject. 
     As shown in  FIG. 4 , the line light ray L 1  that travels along the irradiation optical path  53  and enters the protrusion  1 A of the measurement area  201  at an incident angle θ 1  is reflected and scattered by the protrusion  1 A. The detection light ray L 2  reflected at a reflection angle θ 2 , of the light reflected and scattered by the protrusion  1 A, travels along a reflection optical path  54 A, which is an example of the reflection optical path  54 , and enters the main body  10  via the opening  70 . 
     Also, the line light ray L 1  that enters the depression  1 B of the measurement area  201  at the incident angle θ 1  is reflected and scattered by the depression  1 B. The detection light ray L 2  reflected at the reflection angle θ 2 , of the light reflected and scattered by the protrusion  1 B, travels along a reflection optical path  54 B, which is an example of the reflection optical path  54 , and enters the main body  10  via the opening  70 . The reflection optical path  54 A and the reflection optical path  54 B are substantially parallel with each other with an interval D being interposed therebetween. 
     Hereinafter, the detection light ray L 2  that travels along the reflection optical path  54 A and enters the main body  10  via the opening  70  is also referred to as a detection light ray L 2 A, and the detection light ray L 2  that travels along the reflection optical path  54 B and enters the main body  10  via the opening  70  is also referred to as a detection light ray L 2 B. 
     Again, as shown in  FIGS. 1 and 2 , the detection light ray L 2 A and the detection light ray L 2 B reflected in the measurement area  201  and reflected by the light receiving mirror  62  are received by the light receiving unit  30 . 
     The adjustment mechanism  80  can adjust the incident angle of the light ray entering the opening  70  from the light projection optical path  51 . For example, the adjustment mechanism  80  is a stage for adjusting the incident angle and the position of the light on the reflection surfaces of the light projecting mirror  61  and the light receiving mirror  62 . This stage rotates the light projecting mirror  61  and the light receiving mirror  62  about predetermined rotation axes and moves the light projecting mirror  61  and the light receiving mirror  62 , through a manual operation or according to a control signal from a control unit (not shown). 
     More specifically, the adjustment mechanism  80  adjusts the incident angle at which the line light ray L 1  reflected by the light projecting mirror  61  enters the opening  70 , by rotating the light projecting mirror  61  about a predetermined rotation axis. In other words, the adjustment mechanism  80  can adjust the incident angle of the line light ray L 1  entering the measurement area  201  by rotating the light projecting mirror  61  about a predetermined rotation axis. The incident angle θ 1  and the reflection angle θ 2  of the line light ray L 1  entering the measurement area  201  is set to 30°, for example. 
     Also, the adjustment mechanism  80  adjusts the incident angle at which the light reflected in the measurement area  201  enters the light receiving mirror  62 , by rotating the light receiving mirror  62  about a predetermined rotation axis, so that a larger amount of light, of the light reflected in the measurement area  201 , is reflected by the light receiving mirror  62  and enters the light receiving unit  30 , for example. 
     Also, the adjustment mechanism  80  moves the light projecting mirror  61  and the light receiving mirror  62  along a straight line that connects the light source unit  20  and the light receiving unit  30 , i.e., in the direction indicated by the block arrows in  FIG. 1 , while rotating the light projecting mirror  61  and the light receiving mirror  62 , for example. 
     The light receiving unit  30  receives the detection light rays L 2 A and L 2 B reflected from the measurement area  201  and reflected by the light receiving mirror  62 . 
     For example, the length of the light receiving unit  30  in the direction orthogonal to the width of the light-receiving surface thereof is longer than the interval D between the reflection optical path  54 A of the detection light ray L 2 A and the reflection optical path  54 B of the detection light ray L 2 B. 
     Note that  FIG. 4  only shows the detection light ray L 2 A reflected by one protrusion  1 A shown in  FIG. 3  and the detection light ray L 2 B reflected by one depression  1 B shown in  FIG. 3 . When a measurement subject  200  provided with a plurality of protrusions  1 A and a plurality of depressions  1 B is irradiated with the line light ray L 1 , a plurality of sets each composed of the detection light rays L 2 A and L 2 B reflected along the pair of reflection optical paths  54 A and  54 B shown in  FIG. 4  are arranged in the direction orthogonal to the sheet of the drawing. 
     The light receiving unit  30  transmits the result of receiving the detection light rays L 2 A and L 2 B to the analysis unit  40 . 
     The analysis unit  40  analyzes the shape of the measurement subject  200  based on the light reception result of the light receiving unit  30 . 
       FIG. 5  is a diagram showing an example of an image generated by the analysis unit of the measurement device according to the embodiment of the present invention. 
     As shown in  FIG. 5 , the analysis unit  40  generates an image P that includes a luminance line RL 3  corresponding to the light irradiation line L 3  generated on the measurement area  201 , based on the light reception result of the light receiving unit  30 . The luminance line RL 3  includes protrusions  11 A corresponding to protrusions  1 A of the measurement area  201  and depressions  11 B corresponding to depressions  1 B of the measurement area  201 . 
     The analysis unit  40  analyzes the shape of the surface or the like of the measurement area of the measurement subject  200  based on the image P thus generated. More specifically, the analysis unit  40  calculates the level difference d between the protrusion  1 A and the depression  1 B in the measurement area  201  of the measurement subject  200 . 
     More specifically, for example, the number of pixels between the protrusion  11 A and the depression  11 B of the luminance line RL 3  in the Z axis direction is proportional to the interval D between an optical path LPA of the detection light ray L 2 A and an optical path LPB of the detection light ray L 2 B. 
     The analysis unit  40  calculates the interval D between the optical path LPA of the detection light ray L 2 A and the optical path LPB of the detection light ray L 2 B by multiplying the number of pixels between the protrusion  11 A and the depression  11 B of the luminance line RL 3  in the Z axis direction by a predetermined coefficient. 
     The analysis unit  40  calculates the level difference d between the protrusion  1 A and the depression  1 B of the measurement area  201  according to Formula (1) shown below, based on the interval D thus calculated. 
     
       
         
           
             
               
                 
                   
                     [ 
                     
                       Math 
                       . 
                       
                           
                       
                       ⁢ 
                       1 
                     
                     ] 
                   
                   ⁢ 
                   
                       
                   
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   d 
                   = 
                   
                     D 
                     
                       cos 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       θ 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       2 
                       × 
                       
                         ( 
                         
                           
                             tan 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             θ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             1 
                           
                           + 
                           
                             tan 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             θ 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             2 
                           
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
       FIG. 6  is a diagram showing the result of the analysis of the surface shape of the measurement subject performed by the analysis unit of the measurement device according to the embodiment of the present invention. The horizontal axis in  FIG. 6  indicates a position in the measurement area  201  of the measurement subject  200  in the extension direction of the line light ray L 1 , and the vertical axis indicates a position in the direction orthogonal to the surface of the measurement subject  200 . 
     As shown in  FIG. 6 , the analysis unit  40  calculates that the two level differences d between the protrusions  1 A and the depressions  1 B formed in the measurement area  201  are 7.0 mm and 6.9 mm, based on the interval D between the optical path LPA and the optical path LPB and Formula (1). 
       FIG. 7  is a plan view showing an example of a measurement area that is to be irradiated with a line light ray emitted from the measurement device according to the embodiment of the present invention. 
     As shown in  FIG. 7 , the light source unit  20  irradiates a plurality of measurement areas  201 A,  201 B, and  201 C of the measurement subject  200  with the line light rays L 1  at the same time or separately, for example. 
     The light receiving unit  30  receives the detection light rays L 2  reflected from the measurement areas  201 A,  201 B, and  201 C, via the light receiving mirror  62 . 
     Based on the light reception result of the light receiving unit  30 , the analysis unit  40  generates an image PA that includes the luminance line RL 3  corresponding to the light irradiation line L 3  in the measurement area  201 A, an image PB that includes the luminance line RL 3  corresponding to the light irradiation line L 3  in the measurement area  201 B, and an image PC that includes the luminance line RL 3  corresponding to the light irradiation line L 3  in the measurement area  201 C. 
     The analysis unit  40  analyzes the images PA, PB, and PC thus generated. For example, the analysis unit  40  detects an object other than the measurement subject  200  by analyzing the images PA, PB, and PC thus generated. 
     More specifically, the analysis unit  40  analyzes the images PA, PB, and PC respectively corresponding to the plurality of measurement areas  201 A,  201 B, and  201 C, using an image processing method such as pattern matching, and detects an abnormality in the measurement areas  201 A,  201 B, and  201 C based on the result of the analysis. 
     More specifically, the analysis unit  40  compares the images PA, PB, and PC with each other using a pattern matching method, to detect the presence of foreign matter in the measurement areas  201 A,  201 B, and  201 C. 
     In the example shown in  FIG. 7 , foreign matter F is present in the depression  1 B of the measurement area  201 B. The analysis unit  40  compares the generated images PA, PB, and PC with each other using a pattern matching method, to detect that the foreign matter F is visible in the image PB. 
     When the foreign matter F is present in the depression  1 B of the measurement area  201 B, it may be impossible to accurately calculate the level difference d between the protrusion  1 A and the depression  1 B in the measurement area  201 B. Therefore, for example, if the presence of the foreign matter F is detected in the depression  1 B of the measurement area  201 B, the analysis unit  40  analyzes the surface shapes of the measurement areas  201 A and  201 C, but does not analyze the surface shape of the measurement area  201 B. 
     For example, the analysis unit  40  generates images PA 1 , PB 1 , and PC 1  using light in a wavelength band different from the wavelength of the line light ray L 1  based on the light reception result of the light receiving unit  30 , and analyzes the images PA 1 , PB 1 , and PC 1  thus generated. 
     More specifically, for example, the light source unit  20  includes a low wavelength band laser light source and emits a line light ray L 1  in a low wavelength band. 
     Thereafter, the analysis unit  40  generates images PA 1 , PB 1 , and PC 1  using light in a wavelength band higher than the wavelength band of the line light ray L 1 , and analyzes the images PA 1 , PB 1 , and PC 1  thus generated. As a result, it is possible to reduce the influence of the light irradiation line L 3  formed in the measurement area  201  on the analysis of the imeges PA 1 , PB 1 , and PC 1  performed by the analysis unit  40 . 
     In addition, in order to facilitate the analysis of the images PA 1 , PB 1 , and PC 1  by the analysis unit  40 , the measurement device  100  may have a configuration in which, for example, an illumination unit that irradiates the measurement area  201  with visible light is provided at a given position inside the main body  10 , for example. 
     If this is the case, the light receiving unit  30  receives light in the visible light band emitted from the illumination unit and reflected by the measurement area  201 . Thereafter, the analysis unit  40  generates images PA 1 , PB 1 , and PC 1  using light in the visible light band, and analyzes the images PA 1 , PB 1 , and PC 1  thus generated. As a result, it is possible to reduce the influence of the light irradiation line L 3  formed in the measurement area  201  on the analysis of the imeges PA 1 , PB 1 , and PC 1  performed by the analysis unit  40 . 
     Measurement Example 1 
       FIG. 8  is a diagram showing an example of the content of a measurement performed by the measurement device according to the embodiment of the present invention. Note that  FIG. 8  does not show the components provided in the main body  10  of the measurement device  100 , to simplify the description thereof. 
     As shown in  FIG. 8 , the measurement device  100  includes a control unit  81 . The measurement device  100  measures the shape of the measurement subject  200  in a state where the opening  70  faces downward in the vertical direction. The measurement device  100  can measure the surface shape of a measurement subject  200  that is difficult to carry, such as a Braille block installed on the ground. 
     More specifically, the measurement device  100  includes a moving mechanism  21  that can move the main body  10  in one or more directions. 
     The control unit  81  drives the moving mechanism  21  by transmitting a control signal for controlling the moving mechanism  21  to the moving mechanism  21  so that the opening  70  of the main body  10  and the measurement area  201  face each other. More specifically, the control unit  81  drives the moving mechanism  21  to move the main body  10  in one or more horizontal directions so that the opening  70  is located above the measurement area  201  of the Braille block, for example. 
     The control unit  81  performs control to, for example, start and stop the emission of the line light ray L 1  performed by the light source unit  20 , and start and stop the analysis performed by the analysis unit  40 , in a state where the opening  70  of the main body  10  is located above the measurement area  201 . 
     The analysis unit  40  transmits the analysis result indicating the level difference d of the uneven shape of the measurement area  201  to the control unit  81 . 
     The control unit  81  transmits the analysis result received from the analysis unit  40  to a device outside the measurement device  100  via a wire or wirelessly. 
     Measurement Example 2 
       FIG. 9  is a diagram showing another example of the content of a measurement performed by the measurement device according to the embodiment of the present invention. Note that  FIG. 9  does not show the components provided in the main body  10  of the measurement device  100 , to simplify the description thereof. 
     As shown in  FIG. 9 , the measurement device  100  measures the shape of the measurement subject  200  in a state where the opening  70  faces upward in the vertical direction. The measurement device  100  can measure the surface shape of a measurement subject  200  that has a circular shape, for example. 
     More specifically, a pair of sloped portions  31  are provided so as to sandwich the measurement device  100 . For example, when the surface shape of the measurement subject  200  that has a cylindrical shape is to be measured, the measurement subject  200  is moved while being rotated so that the measurement subject  200  passes over the opening  70  in an upper surface  10 A of the main body  10  via the sloped portions  31 . 
     The control unit  81  performs control to, for example, start and stop the emission of the line light ray L 1  performed by the light source unit  20 , and start and stop the analysis performed by the analysis unit  40 , in a state where the measurement area  201  of the measurement subject  200  is located above the opening  70  of the main body  10 . 
     The analysis unit  40  transmits the analysis result indicating the level difference d of the uneven shape of the measurement area  201  to the control unit  81 . 
     The control unit  81  transmits the analysis result received from the analysis unit  40  to a device outside the measurement device  100  via a wire or wirelessly. 
     As described above, the measurement device  100  can measure the surface shape of a measurement subject  200  that has a circular shape, such as a tire attached to a vehicle, for example. For example, by sequentially moving a plurality of vehicles so that the tires sequentially pass over the opening  70  in the upper surface  10 A of the main body  10 , it is possible to continuously measure the shapes of the plurality of tires attached to the vehicles, using the measurement device  100 . 
     For example, the measurement device  100  includes a license plate reading device (not shown). The control unit  81  acquires the vehicle number on a license plate of a vehicle detected by the license plate reading device. The control unit  81  transmits the analysis result received from the analysis unit  40  to a device outside the measurement device  100  in association with the vehicle number thus acquired. 
     For example, the measurement device  100  includes two main bodies  10 . The two main bodies  10  are located separate from each other so that the interval between the respective openings  70  thereof corresponds to the interval between the left and right tires of the vehicles, and simultaneously measure the surface shapes of the left and right tires of each vehicle. 
     For example, tires, which are measurement subjects  200 , do not come into contact with the transparent members  71  in a state where the measurement areas  201  are located above the openings  70  of the main bodies  10 . With such a configuration, it is possible to prevent the measurement areas  201  from deforming due to the weight of the measurement subjects  200  themselves, and therefore it is possible to accurately measure the surface shapes of the measurement areas  201 . 
     Modification 
       FIG. 10  is a side view showing a configuration of a measurement device according to a modification of the embodiment of the present invention. 
     As shown in  FIG. 10 , when compared with the measurement device  100  shown in  FIG. 1 , a measurement device  101  further includes a half mirror  63  that is provided at a position on the light projection optical path  51  between the light source unit  20  and the light projecting mirror  61 . 
     The light source unit  20  emits a line light ray L 1 , which is a line-shaped light ray, to the light projection optical path  51 . More specifically, the light source unit  20  emits the line light ray L 1  toward the light projecting mirror  61 . 
     A half mirror  63  allows a portion of the line light ray L 1  received from the light source unit  20  to pass therethrough while reflecting the remaining portion, and irradiates the measurement subject  200  with the line light ray L 1  through the transparent member  71  and the opening  70 . 
     The light projecting mirror  61  reflects the line light ray L 1  passing through the half mirror  63 , and irradiates the measurement subject  200  with the line light ray L 1  through the transparent member  71  and the opening  70 . 
     More specifically, the light projecting mirror  61  irradiates the measurement area  201 A of the measurement subject  200  with the line light ray L 1  through the opening  70 . The half mirror  63  irradiates the measurement area  201 B of the measurement subject  200  different from the measurement area  201 A with the line light ray L 1  through the opening  70 . That is to say, the light projecting mirror  61  and the half mirror  63  simultaneously irradiate the plurality of measurement areas  201 A and  201 B of the measurement subject  200  with the line light rays L 1 . 
     In the example shown in  FIG. 10 , the measurement device  101  includes one half mirror  63 , but the measurement device  101  may include two or more half mirrors  63 . For example, in the case of a measurement device  101  that includes three half mirrors  63 , the light projecting mirror  61  and two half mirrors  63  simultaneously irradiate the three measurement areas  201 A,  201 B, and  201 C of the measurement subject  200  with the line light rays L 1 . 
     The line light ray L 1  reflected by the light projecting mirror  61  and emitted from the measurement device  100  enters the measurement area  201 A at an incident angle θ 1 , and forms a light irradiation line L 3  in the measurement area  201 A. The line light ray L 1  reflected by the half mirror  63  and emitted from the measurement device  100  enters the measurement area  201 B at an incident angle θ 3  different from the incident angle θ 1 , and forms a light irradiation line L 3  in the measurement area  201 B. 
     The line light ray L 1  from the light projecting mirror  61  entering the measurement area  201 A at the incident angle θ 1  is reflected and scattered by the measurement area  201 A. The detection light ray L 2  reflected at the reflection angle θ 2 , of the light reflected and scattered by the measurement area  201 A, enters the main body  10  via the opening  70 . 
     The line light ray L 1  from the half mirror  63  entering the measurement area  201 A at the incident angle θ 3  is reflected and scattered by the measurement area  201 B. The detection light ray L 2  reflected at a reflection angle θ 4 , of the light reflected and scattered by the measurement area  201 B, enters the main body  10  via the opening  70 . 
     The detection light ray L 2  reflected by the measurement area  201 A and reflected by the light receiving mirror  62 , and the detection light ray L 2  reflected by the measurement area  201 B and reflected by the light receiving mirror  62 , are received by the light receiving unit  30 . 
     The adjustment mechanism  80  adjusts the incident angle at which the line light ray L 1  reflected by the half mirror  63  enters the opening  70 , by rotating the half mirror  63  about a predetermined rotation axis. 
     More specifically, the adjustment mechanism  80  adjusts the incident angle at which the line light ray L 1  reflected by the half mirror  63  enters the opening  70 , so that the detection light ray L 2  reflected by the measurement area  201 A and the detection light ray L 2  reflected by the measurement area  201 B are reflected by the light receiving mirror  62  and enter different positions on the light-receiving surface of the light receiving unit  30 . 
     The light receiving unit  30  receives the detection light ray L 2  reflected by the measurement area  201 A and the detection light ray L 2  reflected by the measurement area  201 B in different areas of the light-receiving surface, and transmits the light reception result to the analysis unit  40 . 
     The analysis unit  40  analyzes the shape of the surface or the like of the measurement subject  200  in the measurement areas  201 A and  201 B based on the light reception result of the light receiving unit  30 . More specifically, the analysis unit  40  generates an image P that includes two luminance lines RL 3  corresponding to the measurement area  201 A and the measurement area  201 B, and analyses the shape of the surface of the measurement subject  200  in the measurement areas  201 A and  201 B based on the image P thus generated. 
     Operation Flow 
     The measurement device according to the embodiment of the present invention is provided with a computer that includes a memory, and a calculation unit such as a CPU of the computer reads out a program that includes some or all of the steps of the following flowchart from the memory, and executes the program. The programs for these devices can be installed from the outside, respectively. The programs for these devices are distributed in a state of being stored in a recording medium, respectively. 
       FIG. 11  is a flowchart showing operation procedures that are performed by the measurement device according to the embodiment of the present invention when analyzing the surface shape of the measurement area of the measurement subject. 
     As shown in  FIG. 11 , first, the measurement device  100  adjusts the incident angle of a light ray travelling from the light projection optical path  51  to the opening  70 , using the adjustment mechanism  80  (step S 102 ). 
     Next, the measurement device  100  irradiates the measurement areas  201 A,  201 B, and  201 C of the measurement subject  200  with the line light ray L 1  via the light projection optical path  51  and the opening  70  in a state where the opening  70  of the main body  10  faces the measurement area  201  of the measurement subject  200 . For example, the measurement device  100  includes two half mirrors  63 , and simultaneously irradiates the measurement areas  201 A,  201 B, and  201 C with line light rays L 1  (step S 104 ). 
     Next, the measurement device  100  receives the reflected light rays from the measurement areas  201 A,  201 B, and  201 C via the opening  70  and the light receiving optical path  52  (S 106 ). 
     Next, the measurement device  100  generates images PA, PB, and PC respectively corresponding to the measurement areas  201 A,  201 B, and  201 C, based on the light reception result of the reflected light rays from the measurement areas  201 A,  201 B, and  201 C (step S 108 ). 
     Next, the measurement device  100  analyzes the generated images PA, PB, and PC using an image processing method such as pattern matching, to detect an abnormality in the measurement areas  201 A,  201 B, and  201 C based on the analysis result (step S 110 ). 
     Next, if an abnormality is detected in the measurement area  201 B, for example, the measurement device  100  analyzes the shapes of the surfaces or the like of the measurement areas  201 A and  201 C based on the light reception result of the reflected light rays from the measurement areas  201 A and  201 C in which no abnormality is detected (step S 112 ). 
     Although the measurement devices  100  and  101  according to the embodiment of the present invention employ a configuration in which the light source unit  20  and the light receiving unit  30  are provided inside the main body  10 , the present invention is not limited to such a configuration. It is possible to employ a configuration in which at least either the light source unit  20  or the light receiving unit  30  may be provided outside the main body  10 . 
     Also, although the measurement devices  100  and  101  according to the embodiment of the present invention employ a configuration in which the light source unit  20  emits a line light ray L 1 , the present invention is not limited to such a configuration. The light source unit  20  may be configured to emit a beam-shaped light ray. If this is the case, the measurement devices  100  and  101  include an optical member for converting light emitted from the light source unit  20  into a line light ray L 1 , provided on the light projection optical path  51 , for example. Light emitted from the light source unit  20  is converted by the optical member into a line light ray L 1 , with which the measurement subject  200  is irradiated via the transparent member  71  and the opening  70 . 
     Also, although the measurement devices  100  and  101  according to the embodiment of the present invention employ a configuration in which the light projecting mirror  61  is provided, the present invention is not limited to such a configuration. The measurement devices  100  and  101  may be configured without the light projecting mirror  61 . If this is the case, the light source unit  20  is provided inside or outside the main body  10  so as to face the measurement subject  200  with the opening  70  being interposed therebetween, and irradiates the measurement area  201  of the measurement subject  200  with a line light ray L 1  via the transparent member  71  and the opening  70 . 
     Also, although the measurement devices  100  and  101  according to the embodiment of the present invention employ a configuration in which the light receiving mirror  62  is provided, the present invention is not limited to such a configuration. The measurement devices  100  and  101  may be configured without the light receiving mirror  62 . If this is the case, the light receiving unit  30  is provided inside or outside the main body  10  so as to face the measurement subject  200  with the opening  70  being interposed therebetween, and receives at least a portion of the light ray reflected by the measurement area  201  of the measurement subject  200  and entering the main body  10 , as a detection light ray L 2 . 
     Also, although the measurement devices  100  and  101  according to the embodiment of the present invention employ a configuration in which the analysis unit  40  is provided, the present invention is not limited to such a configuration. The measurement devices  100  and  101  may be configured without the analysis unit  40 . If this is the case, the light receiving unit  30  transmits the light reception result to an external device wirelessly or via a wire. 
     Also, although the measurement devices  100  and  101  according to the embodiment of the present invention employ a configuration in which the analysis unit  40  analyzes the images PA, PB, and PC respectively corresponding to the measurement areas  201 A,  201 B, and  201 C to detect an abnormality in the measurement areas  201 A,  201 B, and  201 C, the present invention is not limited to such a configuration. It is possible to employ a configuration in which the analysis unit  40  does not generate images PA, PB, and PC, and does not detect an abnormality in the measurement areas  201 A,  201 B, and  201 C. 
     Also, although the measurement devices  100  and  101  according to the embodiment of the present invention employ a configuration in which the adjustment mechanism  80  is provided, the present invention is not limited to such a configuration. The measurement devices  100  and  101  may be configured without the adjustment mechanism  80 . That is to say, the light projecting mirror  61  and the light receiving mirror  62  may be fixed. 
     Also, although the measurement devices  100  and  101  according to the embodiment of the present invention employ a configuration in which the transparent member  71  for closing the opening  70  is provided, the present invention is not limited to such a configuration. The measurement devices  100  and  101  may be configured without the transparent member  71 . 
     Also, although the measurement devices  100  and  101  according to the embodiment of the present invention employ a configuration in which the transparent member  71  is provided on the other side of the measurement subject  200  with respect to the opening  70 , the present invention is not limited to such a configuration. It is possible to employ a configuration in which the transparent member  71  is provided on the same side as the measurement subject  200  with respect to the opening  70 , or a configuration in which the transparent member  71  is attached to the main body  10  so as to fill the opening  70 . 
     The foregoing embodiments are to be construed in all respects as illustrative and not restrictive. The scope of the present invention is defined by the claims rather than the description above, and is intended to include all modifications within the meaning and scope of the claims and equivalents thereof. 
     DESCRIPTIONS OF REFERENCE NUMERALS 
     
         
           10  Main body 
           10 A Upper surface 
           20  Light source unit 
           21  Moving mechanism 
           30  Light receiving unit 
           31  Sloped portion 
           40  Analysis unit 
           51  Light projection optical path 
           52  Light receiving optical path 
           53  Irradiation optical path 
           54  Reflection optical path 
           61  Light projecting mirror 
           62  Light receiving mirror 
           63  Half mirror 
           70  Opening 
           71  Transparent member 
           80  Adjustment mechanism 
           81  Control unit 
           100  Measurement device 
           101  Measurement device 
           200  Measurement subject 
           201  Measurement area