Three-dimensional shape measurement device

Abstract

This three-dimensional shape measurement device comprises: a light source device that generates stripe pattern light including a stripe pattern for three-dimensional measurement; a projection optical system that converts the stripe pattern light into projection light and projects the projection light onto a measurement object; and an imaging unit that images the measurement object irradiated with the projection light. The projection optical system includes an optical element that changes the aspect ratio of the stripe pattern light generated by the light source device so that expansion of the pattern pitch of the stripe pattern is suppressed.

Description

Three-dimensional shape measurement device

[0001] The present invention relates to a three-dimensional shape measurement device that measures the three-dimensional shape of a measurement object using stripe pattern light.

[0002] In three-dimensional measurement by the phase shift method, stripe pattern light is projected onto the measurement object. Based on a plurality of images of the measurement object captured by shifting the positions of light and dark of the stripe pattern light, the three-dimensional shape of the measurement object can be obtained. Patent Document 1 discloses a three-dimensional shape measurement device using a DMD (Digital Mirror Device) that can generate stripe pattern light by simply reflecting the light of a light source.

[0003] In order to improve the accuracy of three-dimensional measurement, it is necessary to acquire an image of the measurement object onto which stripe pattern light with a shorter stripe pattern pitch is projected. However, the field of view of the camera for acquiring the image and the projection area of the projection light of the stripe pattern light may not match. In this case, wasteful projection light is irradiated outside the camera field of view, and as a result, imaging of the measurement object onto which short-pitch stripe pattern light is projected may not be possible.

[0004] Japanese Patent No. 5780659

[0005] An object of the present invention is to provide a three-dimensional shape measurement device that can accurately measure the three-dimensional shape of a measurement object using stripe pattern light.

[0006] A three-dimensional shape measurement device according to one aspect of the present invention includes a light source device that generates stripe pattern light including a stripe pattern for three-dimensional measurement, a projection optical system that converts the stripe pattern light into projection light and projects it onto a measurement object, and an imaging unit that images the measurement object irradiated with the projection light. The projection optical system includes an optical element that changes the aspect ratio of the stripe pattern light generated by the light source device so as to suppress an expansion of the pattern pitch of the stripe pattern.

[0007] Figure 1 is a diagram showing the configuration of a printed circuit board production line, which is an example of an application of the three-dimensional shape measuring device according to the present invention. Figure 2 is a block diagram showing the configuration of the three-dimensional shape measuring device according to an embodiment of the present invention. Figure 3 is a diagram showing the configuration of a projector including a light source device and a projection optical system. Figure 4 is an optical path diagram showing the details of the projection optical system shown in Figure 3. Figure 5(A) is a perspective view showing an optical element consisting of a pair of anamorphic prisms, and Figure 5(B) is an explanatory diagram of the change in the aspect ratio of the fringe pattern light by the optical element. Figure 6 is a diagram showing the projection of fringe pattern light and imaging of the fringe pattern according to a comparative example. Figure 7 is a diagram showing the projection of fringe pattern light and imaging of the fringe pattern according to an embodiment. Figure 8 is an optical path diagram showing a modified example of the projection optical system. Figure 9 is an optical path diagram showing a modified example of the light source device. Figure 10 is an optical path diagram showing another modified example of the light source device.

[0008] Embodiments of the present invention will be described in detail below with reference to the drawings. The three-dimensional shape measuring device according to the present invention can be widely applied to acquiring three-dimensional shape information, such as the height and outer diameter, of various industrial products, semi-finished products, machine parts, electronic components, food products, agricultural products, and other objects to be measured. For example, a suitable application of the three-dimensional shape measuring device of the present invention is to perform three-dimensional measurement to inspect the mounting state of a component mounted on a printed circuit board.

[0009] [Example of Application of Three-Dimensional Shape Measurement Device: Printed Circuit Board Production Line] Figure 1 is a diagram of the configuration of a printed circuit board production line 1, which is an example of an application of the three-dimensional shape measurement device according to the present invention. In Figure 1, each component of the printed circuit board production line 1 is shown in simplified blocks. The printed circuit board production line 1 includes a printing press 11, a printing inspection machine 12, a mounter 13, a board inspection machine 14, a reflow oven 15, and a visual inspection machine 16, which are arranged in tandem along a conveyor 10 that transports printed circuit boards in the direction indicated by the arrows in the figure. At the upstream end of the printed circuit board production line 1, there is a loader 17 that loads boards into the printing press 11, and at the downstream end, there is an unloader 18 that removes the produced boards from the visual inspection machine 16.

[0010] The printing press 11 applies solder to the pad portion of the printed circuit board. For example, the printing press 11 places a mask with openings for solder application onto the printed circuit board and applies solder paste from above the mask. The printing inspection machine 12 takes an image of the soldered printed circuit board to determine the two-dimensional and three-dimensional shape of the solder and inspects whether the position, amount, and height of the solder applied to the printed circuit board are appropriate.

[0011] The mounter 13 is equipped with a head for mounting components and mounts the required electronic components onto the printed circuit board. In the example shown in Figure 1, three mounters 13 are arranged in a row. That is, the first mounter 13A, the second mounter 13B, and the third mounter 13C are arranged in tandem from the upstream side. The board inspection machine 14 images the printed circuit board after it has passed through the mounter 13 and inspects for misalignment of electronic components mounted on the printed circuit board, component lifting, mounting omissions, soldering defects, etc.

[0012] The reflow oven 15 heats the printed circuit board on which electronic components are mounted to melt the solder and fix the electronic components to the printed circuit board. The visual inspection machine 16 takes an image of the printed circuit board after the heating process in the reflow oven 15 and inspects for misalignment of electronic components, loose components, missing components, soldering defects, etc., in the same way as the board inspection machine 14.

[0013] The three-dimensional shape measuring device according to the present invention can be applied to the printing inspection machine 12, the substrate inspection machine 14, and the visual inspection machine 16 described above. In the printing inspection machine 12, the three-dimensional shape measuring device can be used to inspect whether or not solder is applied to the printed circuit board in a normal shape. In the substrate inspection machine 14 and the visual inspection machine 16, the three-dimensional shape measuring device can be used to inspect whether or not electronic components are properly mounted on the printed circuit board.

[0014] [Overall Configuration of the Three-Dimensional Shape Measurement Device] Figure 2 is a block diagram showing the configuration of the three-dimensional shape measurement device 100 according to this embodiment. The three-dimensional shape measurement device 100 includes a conveyor 10, a head movement mechanism 20, an imaging head unit 30, and a control device 40. A substrate P on which electronic components are mounted is shown as an example of the object to be measured by the three-dimensional shape measurement device 100. Figure 2 shows the three orthogonal axes X, Y, and Z for the purpose of explaining direction. This does not limit the direction in the actual device, but for example, the X direction is the transport direction of the substrate P and is the horizontal direction, the Y direction is the direction perpendicular to the X direction on the horizontal plane, and the Z direction is the vertical direction perpendicular to both the X and Y directions. Z1 is the upward direction, and Z2 is the downward direction.

[0015] The conveyor 10 transports the substrate P in the X direction. A measurement stage is set up below the imaging head 30. The conveyor 10 brings the substrate P in from the outside toward the measurement stage, stops the substrate P on the measurement stage, and holds it there. After a predetermined measurement operation on the substrate P by the imaging head 30, the conveyor 10 transports the substrate P away from the measurement stage to the outside.

[0016] The head movement mechanism 20 moves the imaging head 30 in the XYZ directions. That is, the head movement mechanism 20 has ball screw axes for the X, Y, and Z axes as head movement axes. In order to move the imaging head 30 by driving these head movement axes, the head movement mechanism 20 includes an X-axis motor 21, a Y-axis motor 22, and a Z-axis motor 23. These motors 21, 22, and 23 are, for example, servo motors. The head movement mechanism 20 may also be a mechanism using linear motors or a robot hand.

[0017] The imaging head unit 30 performs imaging necessary for three-dimensional measurement of the object to be measured using the phase shift method. In the phase shift method, imaging is performed while changing the phase of the light irradiated onto the object to be measured, thereby acquiring three-dimensional data of the surface of the object to be measured. In this embodiment, the imaging head unit 30 images the substrate P on the conveyor belt 10 for inspection of the substrate P itself to which solder has been applied, or of electronic components mounted on the substrate P. The imaging head unit 30 includes a camera 31 as the imaging unit for the substrate P, and a projector 32 that irradiates the substrate P with measurement projection light.

[0018] Camera 31 is positioned above the measurement stage and captures images of the substrate P illuminated by the projection light. Camera 31 includes a lens barrel 31a and an image sensor 31b. The lens barrel 31a causes the reflected light image of the substrate P illuminated by the projection light to enter the camera 31 along the imaging axis CA, and forms an image of the reflected light image on the image sensor 31b. The image sensor 31b converts the reflected light image into an image by photoelectric conversion and generates image data for inspection. This image data is sent to the control device 40.

[0019] The projector 32 projects light containing a striped pattern onto the substrate P along the projection optical axis AX. The projector 32 is positioned above the measurement stage with a predetermined inclination angle with respect to the Z direction. In other words, the projection optical axis AX is inclined by a predetermined angle with respect to the imaging axis CA which extends vertically. Figure 2 shows only two projectors 32 arranged symmetrically on either side of the imaging axis CA. For example, four or eight projectors 32 are arranged at equal intervals in the circumferential direction of a virtual circle centered on the imaging axis CA. The detailed structure of the projector 32 will be described in detail later based on Figure 3.

[0020] The control device 40 includes a control unit 41, an axis control unit 42, a projection control unit 43, an imaging control unit 44, an image processing unit 45, a storage unit 46, and a calculation unit 47. The control unit 41 consists of a processor that performs logical operations and comprehensively controls the operation of the axis control unit 42, the projection control unit 43, and the imaging control unit 44. The control unit 41 controls the axis control unit 42 so that the imaging head unit 30 moves according to a predetermined measurement sequence. The control unit 41 controls the projection control unit 43 and the imaging control unit 44 so that the imaging head unit 30 performs a predetermined imaging operation under the illumination of projection light. Furthermore, the control unit 41 controls the image processing unit 45 and the calculation unit 47 so that they perform the necessary processing.

[0021] The axis control unit 42 controls the driving of the X-axis motor 21, Y-axis motor 22, and Z-axis motor 23 of the head movement mechanism 20 based on the control signals provided by the control unit 41. The imaging head unit 30 moves in the XYZ directions through the drive control of the axis control unit 42. The axis control unit 42 also controls the driving of a motor (not shown) that drives the conveyor 10.

[0022] The projection control unit 43 controls the projector 32 to project light containing a striped pattern onto the measurement area of ​​the substrate P. The imaging control unit 44 controls the camera 31 mounted on the imaging head unit 30 to image the substrate P, which is illuminated by the projected light, at predetermined timings. The projector 32 is controlled to project striped pattern light with different phases four times per field of view of the camera 31. The camera 31 is controlled to take an image each time the projected light is irradiated. Based on the brightness changes in the four acquired images, phase changes originating from the surface shape of the substrate P are analyzed. Based on the analysis results, three-dimensional data such as the height of components on the substrate P is obtained.

[0023] The image processing unit 45 acquires image data of the substrate P captured by the camera 31. The image processing unit 45 performs necessary image processing on the image data, such as contrast and brightness correction and noise reduction.

[0024] The storage unit 46 temporarily stores the image data of the substrate P after the image processing unit 45 has performed image processing. The storage unit 46 also stores various data and setting values ​​necessary for the operation of the three-dimensional shape measuring device 100. Substrate data such as the size and type of the substrate P to be measured, component data such as the type, size, and arrangement of components mounted on the substrate P, and information on the stripe pattern to be used are also stored in the storage unit 46.

[0025] The calculation unit 47 performs processing to calculate three-dimensional data such as height data of electronic components and solder patterns on the substrate P based on the image data of the substrate P stored in the storage unit 46. Specifically, the calculation unit 47 obtains height data by analyzing the phase changes of multiple images irradiated with stripe pattern light of different phases.

[0026] [Projector Details] Figure 3 shows the internal configuration of the projector 32. The projector 32 includes a light source device 33, a projection optical system 34, a control board 35, and a housing 32H that accommodates them. Figure 4 is an optical path diagram showing the details of the projection optical system 34. The light source device 33 generates striped pattern light L1, which includes a striped pattern for three-dimensional measurement. The light source device 33 includes a light source 331, a focusing lens 332, a mirror 333, and a DMD element 36.

[0027] The light source 331 emits light that forms the basis of the projected light emitted by the projector 32. For example, a white LED can be used as the light source 331. The focusing lens 332 converts the diffused light emitted by the light source 331 into parallel light. The mirror 333 reflects the light from the light source 331 so that it is incident on the DMD element 36 at a predetermined oblique angle. In other words, the light emitted from the light source 331 is irradiated onto the DMD element 36 via the focusing lens 332 and the mirror 333.

[0028] The DMD element 36 has a reflective surface 36R that reflects light from the irradiated light source 331. The light reflected by the reflective surface 36R becomes striped pattern light L1. Striped pattern light L1 is light with a light and dark pattern in which sinusoidal light intensity distributions appear at equal intervals. The reflective surface 36R has a plurality of movable micromirrors (hereinafter referred to as pixels) arranged in a matrix. The plurality of pixels can be electrically driven individually, and by turning them on, they can reflect light in a predetermined direction with any gradation. By controlling the on / off state of the plurality of pixels, a reflective surface 36R capable of emitting striped pattern light L1 is formed. Generally, the reflective surface 36R of the DMD element 36 has a rectangular shape with a longitudinal direction and a transverse direction. In Figure 4, an example of a reflective surface 36R in which the pixels are controlled so as to be able to generate striped pattern light L1 having a beam cross-section in which the stripes ST of the striped pattern are aligned parallel to the transverse direction is shown.

[0029] The light source device 33 has a fitting portion 334 for mounting to the housing 32H. The fitting portion 334 supports the light source device 33 so that it can rotate and move linearly relative to the housing 32H. The fitting portion 334 allows the light source device 33 to rotate approximately 90 degrees around the normal N of the DMD element 36. By rotating the light source device 33, the DMD element 36 and the light source 331 rotate around the normal N. The light source device 33 can also move linearly along the direction of the projection optical axis AX. The shape and size of the projection area LP can be changed by the rotation and movement of the light source device 33 as described above.

[0030] The projection optical system 34 converts the fringe pattern light L1 into projection light L2 and projects it onto the substrate P, which is the object to be measured. The projection optical system 34 includes a projection lens group 34R and optical elements 37. The projection lens group 34R is a group of optical lenses that converts the fringe pattern light L1 into projection light L2 at the required magnification. Generally, the projection lens group 34R is a group of optical lenses that produces projection light L2 by magnifying the fringe pattern light L1. However, if the object to be measured or the measurement area is small, a group of optical lenses that produces reduced projection light L2 may be used as the projection lens group 34R.

[0031] The optical element 37 is an optical component that changes the aspect ratio of the fringe pattern light L1. The reflective surface 36R of the DMD element 36 has a rectangular shape in plan view. Therefore, the shape of the beam cross section of the fringe pattern light L1 created by reflection at the reflective surface 36R in the direction perpendicular to the projection optical axis AX is also rectangular. The optical element 37 changes the aspect ratio of the fringe pattern light L1 so as to suppress the expansion of the pattern pitch SP of the fringes ST included in the projected light L2.

[0032] Figure 4 shows the projection surface of the substrate P irradiated with projection light L2. The projection region LP is shown as the area on the substrate P irradiated with projection light L2. As previously described, the projection light axis AX is inclined with respect to the Z direction, so the projection region LP that appears on the projection surface of the substrate P is trapezoidal. The reflective surface 36R of the DMD element 36 generates striped pattern light L1 in which the stripes ST of the striped pattern are arranged parallel to the short side within a rectangular area. The optical element 37 generates projection light L2 by stretching the striped pattern light L1 in the direction in which the stripes ST extend. When the vertical and horizontal directions of the striped pattern light L1 are expanded equally, the pattern pitch SP also expands according to the magnification ratio. The optical element 37 stretches the stripes ST, that is, it creates projection light L2 with unequal magnification, where the short side of the striped pattern light L1 is magnified at a larger magnification than the long side.

[0033] Various optical components can be used as the optical element 37, as long as they have the function of unequal magnification of the beam cross-section described above. For example, the optical element 37 may be a combination of at least two wedge-shaped prisms, or an optical element 37 using one or more cylindrical lenses. Figure 4 illustrates an optical element 37 composed of two anamorphic prisms: a first anamorphic prism 38 and a second anamorphic prism 39.

[0034] Figure 5(A) is a perspective view showing an optical element 37 consisting of a pair of anamorphic prisms 38 and 39, and Figure 5(B) is an explanatory diagram illustrating the change in the aspect ratio of the fringed pattern light L1 by the optical element 37. Anamorphic prisms possess anisotropy in refractive index and have the property of refracting light incident at a specific angle in different directions. In other words, anamorphic prisms have the property of compressing or expanding light in a specific direction. By adjusting the arrangement angle of the pair of anamorphic prisms 38 and 39 having this property and the incident angle of the fringed pattern light L1, the beam cross-section can be magnified unevenly in the vertical and horizontal directions.

[0035] Specifically, as shown in Figure 5(B), the inclination angle θ1 of the first anamorphic prism 38 with respect to the reference direction, the inclination angle θ2 of the second anamorphic prism 39 with respect to the reference direction, the distance D between the two prisms, and the incident angle of the fringe pattern light L1 are selected in order to convert the beam cross-section of the fringe pattern light L1 to a desired aspect ratio.

[0036] The first anamorphic prism 38 has a triangular cross-section and includes a first surface 381 and a second surface 382 as the light rays of the striped pattern light L1. The second anamorphic prism 39 also has a triangular cross-section and includes a third surface 391 and a fourth surface 392 as the light ray passage surfaces. The first surface 381 and the third surface 391 are the incident surfaces of the light rays, and the second surface 382 and the fourth surface 392 are the exit surfaces of the light rays. The first surface 381 and the third surface 391 are arranged obliquely to the direction of propagation of the light rays.

[0037] The fringed pattern light L1 with a beam cross-sectional width D1, reflected by the reflective surface 36R of the DMD element 36, is incident on the first surface 381 of the first anamorphic prism 38 at a predetermined inclination angle. The inclination angle is set to the Brewster angle Br with respect to the vertical line of the first surface 381. In other words, the inclination angle θ1 is set to the angle that realizes the Brewster angle Br. After the fringed pattern light L1 is emitted from the second surface 382, ​​it is incident on the third surface 391 of the second anamorphic prism 39 at a predetermined inclination angle. The inclination angle θ2 is set to the angle that realizes the said incident angle. The fringed pattern light L1E, after aspect ratio conversion and emitted from the fourth surface 392, has a beam cross-sectional width D2 that is larger than D1. The optical element 37 converts the fringed pattern light L1 so that the ratio of D1 to D2 is different in the vertical and horizontal directions of the beam cross-section.

[0038] The control board 35 controls the operation of the light source 331 and the DMD element 36 of the light source device 33. The control board 35 lights up the light source 331 at a predetermined timing to generate the striped pattern light L1. The control board 35 also controls the on / off state of the numerous pixels of the DMD element 36 to form the required striped pattern on the reflective surface 36R.

[0039] [Explanation of Comparative Examples and Examples of Stripe Pattern Projection] Figure 6 is a diagram showing steps 1 to 3 relating to the projection of stripe pattern light L1 and imaging of the stripe pattern according to the comparative example. In the comparative example, an example is shown in which the stripe pattern light L1 is projected with the length and width magnified to the same extent. The DMD element 36 has a rectangular reflective surface 36R with a long side X1 and a short side Y1. That is, it creates a stripe pattern light L1 with a beam cross-section having a size of X1 in the long direction and Y1 in the short direction. The stripes ST of the stripe pattern light L1 are arranged parallel to the short direction. Note that if the stripes ST are arranged parallel to the long direction, the number of stripes ST will naturally decrease. Therefore, the control board 35 controls the on / off state of the pixels of the DMD element 36 so that the stripes ST are arranged parallel to the short direction.

[0040] Figure 6 illustrates the case where the camera field of view CV of camera 31 is square. The camera field of view CV is usually the size that images a portion of the substrate P. If it is necessary to inspect the entire substrate P or an area exceeding the camera field of view CV, multiple images are taken of a single substrate P. In step 1, the size of the beam cross-section of the fringe pattern light L1 created by the DMD element 36 and the camera field of view CV are checked.

[0041] In step 2, the magnification of the fringe pattern light L1 by the projection optical system 34 is determined so as to cover the entire camera field of view CV. In other words, the projection magnification by the projection lens group 34R of the projection optical system 34 is set so that the camera field of view CV fits within the projection area LP1 of the projection light L2 created by the projection optical system 34. In the comparative example, since the optical element 37 that converts the aspect ratio is not used, the projection optical system 34 magnifies and projects the fringe pattern light L1 at 1:1 ratio in both the vertical and horizontal (XY) directions. The projection area LP1 has expanded long sides X2 and short sides Y2 relative to the long side X1 and short side Y1 of the fringe pattern light L1. Since it is a 1:1 projection, X1:Y1 = X2:Y2. The pattern pitch SP1 of the fringe ST in the projected light L2 becomes an expanded pitch in the ratio of X1:X2.

[0042] In step 3, the camera 31 images the substrate P irradiated with the projection light L2. Although the camera field of view CV is within the projection area LP1, there are also useless portions that do not fit within the camera field of view CV. Also, since the pattern pitch SP1 of the stripe ST is expanded, the number of stripes ST that fit within the camera field of view CV decreases. That is, the pattern pitch SP1 within the camera field of view CV is coarse. The higher the density of the stripes ST within the camera field of view CV, the higher the measurement resolution of the three-dimensional shape. Therefore, it is difficult to perform high-precision three-dimensional shape measurement in the comparative example.

[0043] FIG. 7 is a diagram showing steps 1 to 3 regarding the projection of the stripe pattern light L1 and the imaging mode of the stripe pattern according to an embodiment of the present invention. The embodiment shows an example in which the vertical and horizontal directions of the stripe pattern light L1 are enlarged at unequal magnification. That is, an example in which the projection optical system 34 includes an optical element 37 that changes the aspect ratio of the stripe pattern light L1 is shown. Regarding the size confirmation of the beam cross-sectional size of the stripe pattern light L1 created by the DMD element 36 in step 1 and the camera field of view CV, it is the same as in the comparative example.

[0044] In step 2, the arrangement of the anamorphic prisms 38 and 39 of the projection optical system 34 and the projection magnification of the projection lens group 34R are set so that the projection area LP2 of the projection light L2 created by the projection optical system 34 fits within the camera field of view CV. The stripe pattern light L1 has a rectangular beam cross-section having a long side X1 and a short side Y1. In contrast, the camera field of view CV is square. For this reason, the projection magnification is set so that the long side X1 has a predetermined small magnification and the short side Y1 has a magnification larger than the long side X1.

[0045] The projection region LP2 has extended long sides X3 and short sides Y3 relative to the long side X1 and short side Y1 of the fringe pattern light L1, but since it is an unequal projection, X1:Y1 ≠ X3:Y3. Also, since it is an unequal projection that lengthens the short side Y1, the relationship (X3 / X1) < (Y3 / Y1) holds. The pattern pitch SP2 of the fringe ST in the projection light L2 is an extended pitch in the ratio of X1:X3. However, compared to the comparative example, the relationship (X2 / X1) > (X3 / X1) holds, so the extended width of the pattern pitch SP2 in the embodiment is smaller than that of the comparative example. In short, the projection light L2 of the projection region LP2 is a manifestation in which the fringe pattern light L1 is stretched in the direction in which the fringe ST extends.

[0046] In step 3, the camera 31 images the substrate P illuminated by the projection light L2. The camera field of view CV and the projection area LP2 generally coincide. Furthermore, because the magnification of the long side X3 is small, the expansion of the pattern pitch SP2 of the stripes ST is suppressed. In other words, the projection light L2 can be illuminated into the camera field of view CV without significantly expanding the pattern pitch SP2. As a result, the number of stripes ST that fit within the camera field of view CV can be increased compared to the comparative example. Consequently, the camera 31 can capture an image of the substrate P illuminated by projection light L2 with a short stripe pattern pitch. As a result, the calculation unit 47 of the control device 40 can perform highly accurate three-dimensional shape measurement of the substrate P.

[0047] [Modifications] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. In the above embodiments, an example was shown in which two anamorphic prisms 38 and 39 are used as optical elements to change the aspect ratio of the stripe pattern light L1. The optical elements may also be configured to use at least one cylindrical lens.

[0048] FIG. 8 is an optical path diagram showing the projector 32A according to the modified example. The projector 32A includes a light source device 33 and a projection optical system 34A. The configuration of the light source device 33 is the same as the configuration shown in FIGS. 3 and 4 described above, and includes a DMD element 36 having a reflection surface 36R. The projection optical system 34A includes a projection lens group 34R and a single cylindrical lens 37A as an optical element. The cylindrical lens 37A has a curvature that performs a predetermined magnification in one direction of the lens surface, while having no curvature or a gentle magnification curvature in the other direction orthogonal to the position direction. Therefore, the cylindrical lens 37A has a function of condensing the incident light in a shape close to a straight line.

[0049] The striped pattern light L1 is created by the reflection surface 36R of the DMD element 36 reflecting the light emitted from the light source. After passing through the projection lens group 34R, the striped pattern light L1 enters the cylindrical lens 37A. By passing through the cylindrical lens 37A, the projection light L2 with the aspect ratio of the striped pattern light L1 changed is created. In the example of FIG. 8, the cylindrical lens 37A suppresses the expansion in the Y direction of the striped pattern light L1. The projection light L2 is irradiated onto the substrate P as the measurement object. The irradiated projection light L2 has the stripe ST stretched in the X direction while the expansion in the Y direction in which the stripes ST are arranged is suppressed. That is, the cylindrical lens 37A changes the aspect ratio of the striped pattern light L1 so that the expansion of the pattern pitch of the stripe ST included in the projection light L2 is suppressed.

[0050] In the above embodiment, the light source device 33 including the light source 331 and the DMD element 36 is exemplified as the generation source of the striped pattern light L1. Instead of the DMD element 36, for example, a reflective liquid crystal panel such as a liquid crystal on silicon (LCOS) or a transmissive liquid crystal panel may be used to generate the striped pattern light L1.

[0051] Figure 9 shows a modified light source device 33A. The light source device 33A includes an LCOS 51 as a source of striped pattern light L1 and a polarizing beam splitter 52. The LCOS 51 has a reflective surface that reflects the irradiated light as striped pattern light. The polarizing beam splitter 52 has a cube shape formed by joining two right-angle prisms, and has a coating layer 52R on the joined surface.

[0052] Light emitted from the light source is reflected by the coating layer 52R and incident on the reflective surface of LCOS 51. The reflected light from LCOS 51 passes through the coating layer 52R and heads toward the downstream projection lens group 34R. By being reflected by the reflective surface of LCOS 51, the light from the light source is converted into striped pattern light L1. After passing through the projection lens group 34R, the striped pattern light L1 is incident on the optical element that changes the aspect ratio.

[0053] Figure 10 shows a light source device 33B according to another modification. The light source device 33B includes an LCD 53 as a source of striped pattern light L1 and a pair of polarizing plates 54 arranged to sandwich the LCD 53. The LCD 53 has a transmissive surface with bright and dark areas. Light emitted from the light source passes through the pair of polarizing plates 54 and the LCD 53 and is incident on the projection lens group 34R. When the light passes through the LCD 53, the light from the light source is converted into striped pattern light L1. After passing through the projection lens group 34R, the striped pattern light L1 is incident on an optical element that changes the aspect ratio.

[0054] There are no particular limitations on the manner in which the aspect ratio of the beam cross-section of the striped pattern light L1 is changed by the optical element 37. As in the above embodiment, it is possible to enlarge both the vertical and horizontal directions while using different magnifications for the vertical and horizontal directions, or to enlarge only the vertical or horizontal direction. Furthermore, if the irradiation range of the projected light L2 is narrow, it is possible to reduce both the vertical and horizontal directions of the beam cross-section, or to reduce only the vertical or horizontal direction.

[0055] [Inventions included in the above embodiments] The embodiments described above include the following inventions.

[0056] A three-dimensional shape measuring apparatus according to one aspect of the present invention comprises a light source device that generates striped pattern light including a striped pattern for three-dimensional measurement, a projection optical system that converts the striped pattern light into projection light and projects it onto an object to be measured, and an imaging unit that images the object to be measured irradiated with the projection light, wherein the projection optical system includes an optical element that changes the aspect ratio of the striped pattern light generated by the light source device so as to suppress the expansion of the pattern pitch of the striped pattern.

[0057] According to this embodiment, the optical elements of the projection optical system have a function to change the aspect ratio of the fringe pattern light so as to suppress the expansion of the pattern pitch. Therefore, it is possible to match the illumination range of the projected fringe pattern light with the field of view of the imaging unit without expanding the pattern pitch. Consequently, the imaging unit can acquire an image of the object to be measured illuminated with projected light that has a short fringe pattern pitch. As a result, highly accurate three-dimensional shape measurement of the object to be measured can be performed.

[0058] In the above-described three-dimensional shape measuring apparatus, it is desirable that the light source device generates stripe pattern light in which the stripes of the stripe pattern are arranged parallel to the shorter direction within a rectangular area, and that the optical element generates projected light by stretching the stripe pattern light in the direction in which the stripes extend.

[0059] According to this embodiment, the projected light of the striped pattern is projected onto an area that is closer to a square than a rectangle. In other words, the projection area can be changed while suppressing the expansion of the pattern pitch. Therefore, when the field of view of the imaging unit is square or a rectangle close to a square, the illumination range of the projected light and the field of view of the imaging unit can be aligned while maintaining a short striped pattern pitch.

[0060] In the above-described three-dimensional shape measuring device, it is desirable that the optical element includes at least two anamorphic prisms.

[0061] According to this embodiment, a rectangular optical image can be expanded in one direction by combining two anamorphic prisms. Therefore, a projection optical system that changes the aspect ratio of the fringed pattern light while suppressing the expansion of the pattern pitch of the fringed pattern can be easily constructed.

[0062] In the above-described three-dimensional shape measuring device, the optical element may include at least one cylindrical lens. This configuration also allows for the easy construction of a projection optical system that changes the aspect ratio of the fringe pattern light while suppressing the expansion of the pattern pitch of the fringe pattern.

[0063] In the above-described three-dimensional shape measuring apparatus, it is preferable that the light source device includes a light source and a digital mirror device that generates the striped pattern light by reflecting the light emitted from the light source.

[0064] A digital mirror device can generate striped pattern light simply by reflecting light from a light source. According to the above embodiment, the light source device that generates striped pattern light can be simplified.

[0065] In the above-described three-dimensional shape measuring apparatus, the light source device may include a light source and a reflective liquid crystal device that generates the striped pattern light by reflecting the light emitted from the light source. Alternatively, the light source device may include a light source and a transmissive liquid crystal device that generates the striped pattern light by transmitting the light emitted from the light source.

[0066] Reflective liquid crystal devices can generate striped patterns simply by reflecting light from a light source. Similarly, transmissive liquid crystal devices can generate striped patterns simply by transmitting light from a light source. These embodiments allow for the simplification of the light source device that generates the striped patterns.

Claims

1. A three-dimensional shape measuring device comprising: a light source device that generates striped pattern light including a striped pattern for three-dimensional measurement; a projection optical system that converts the striped pattern light into projection light and projects it onto an object to be measured; and an imaging unit that images the object to be measured irradiated with the projection light, wherein the projection optical system includes an optical element that changes the aspect ratio of the striped pattern light generated by the light source device so as to suppress the expansion of the pattern pitch of the striped pattern.

2. A three-dimensional shape measuring device according to claim 1, wherein the light source device generates stripe pattern light in which the stripes of the stripe pattern are arranged parallel to the short side direction within a rectangular area, and the optical element generates projected light by stretching the stripe pattern light in the direction in which the stripes extend.

3. A three-dimensional shape measuring device according to claim 1 or 2, wherein the optical element includes at least two anamorphic prisms.

4. A three-dimensional shape measuring device according to claim 1 or 2, wherein the optical element includes at least one cylindrical lens.

5. A three-dimensional shape measuring apparatus according to claim 1 or 2, wherein the light source device includes a light source and a digital mirror device that generates the striped pattern light by reflecting light irradiated from the light source.

6. A three-dimensional shape measuring apparatus according to claim 1 or 2, wherein the light source device includes a light source and a reflective liquid crystal device that generates the striped pattern light by reflecting light irradiated from the light source.

7. A three-dimensional shape measuring apparatus according to claim 1 or 2, wherein the light source device includes a light source and a transmissive liquid crystal device that generates the striped pattern light by transmitting light irradiated from the light source.

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