JP6193609B2 - 3D shape measuring device, 3D shape measuring method - Google Patents

Description

  The present invention relates to a three-dimensional shape measuring apparatus and a three-dimensional shape measuring method.

  Several methods have been proposed as a three-dimensional shape measurement method used in a three-dimensional shape measurement apparatus. There are known a passive method in which shape measurement is performed only by an imaging device without using a projection device, and an active method in which a projection device and an imaging device are used in combination. In the active method, the three-dimensional shape of the target object is measured from an image obtained by capturing the projected target object. Since the target object has a three-dimensional shape, the three-dimensional shape measurement apparatus is required to satisfy the accuracy necessary for shape measurement in the depth direction.

  Patent Documents 1 and 2 are disclosed as examples of such an active three-dimensional shape measuring apparatus. Patent Document 1 discloses a technique for irradiating a target object with a slit-shaped projection, controlling a light source so that an integrated irradiation intensity distribution has a triangular wave shape, and performing three-dimensional shape measurement using the principle of the phase shift method. Has been. Patent Document 2 discloses a technique for making a sine wave pattern by defocusing a projection pattern of digital gradation values and performing three-dimensional shape measurement using the principle of the phase shift method as in Patent Document 1. .

Japanese Patent Laid-Open No. 11-118443 JP 2007-85862 A

  However, with the three-dimensional shape measuring apparatus described in Patent Document 1, it is difficult to satisfy the required accuracy in the entire depth direction of the target object. Similarly, in the three-dimensional shape measuring apparatus described in Patent Document 2, it is difficult to satisfy the required accuracy over the entire depth direction of the target object. This is because the amount of light captured by the image capturing device decreases when the image capturing device is separated from the image capturing device, and the captured image becomes dark. When the image obtained by photographing the target object is dark, the SN (ratio of signal to noise) of the photographing apparatus is deteriorated, so that the accuracy of the three-dimensional shape is deteriorated. Further, the contrast deteriorates with defocusing from the focus surface of the projection optical system, and the accuracy of the three-dimensional shape calculated from the image with deteriorated contrast deteriorates.

  Specifically, in the case of a target object having a depth as in Patent Document 1, the amount of light captured by the imaging device is reduced on the back surface relative to the front surface of the imaging device, and the captured image becomes dark. Along with this, the SN of the photographing apparatus deteriorates, and the measurement accuracy deteriorates. For this reason, there is a problem that the measurement accuracy on the surface far from the measurement accuracy on the surface closest to the photographing apparatus is greatly deteriorated, and it is difficult to satisfy the required accuracy in the entire area in the depth direction.

  Further, as in Patent Document 2, when the focus plane of the projection pattern is outside the region where the target object exists, the contrast of the projection pattern is directed toward a plane far from the plane of the target object close to the focus plane of the projection pattern. descend. As a result, the contrast of the captured image is lowered, so that the measurement accuracy is deteriorated, and there is a problem that it is difficult to satisfy the necessary accuracy in the entire area in the depth direction as in Patent Document 1.

  In view of the above-described problems, an object of the present invention is to suppress a decrease in measurement accuracy in the depth direction and obtain good measurement accuracy in the entire measurement space.

In order to achieve the above object, a three-dimensional shape measuring apparatus according to the present invention shoots a pattern light having a bright part and a dark part on a target object, and shoots the target object on which the pattern light is projected. An imaging means for measuring, and a measuring means for measuring the three-dimensional shape of the target object based on the taken image, and the focal position of the projection optical system of the projection means is projected to the projection means Set behind the intersection of the projection axis of the imaging means and the imaging axis of the imaging means, or behind the point on the projection axis where the projection axis of the projection means and the imaging axis of the imaging means are closest. The contrast value between the bright part and the dark part in the image photographed by the photographing unit is a point on the photographing axis at which the intersection or the projection axis of the projecting unit and the photographing axis of the photographing unit are closest to each other. the imaging than It characterized by having the maximum value in the back region with respect to stages.

  According to the present invention, it is possible to suppress a decrease in measurement accuracy in the depth direction and to obtain good measurement accuracy in the entire measurement space.

The lineblock diagram of the three-dimensional shape measuring device concerning a 1st embodiment. The figure which shows the measurement space which concerns on 1st Embodiment. The figure which shows the projection pattern which concerns on 1st Embodiment. 1 is a schematic diagram of an optical system according to a first embodiment. 1 is a schematic diagram of an optical system according to a first embodiment. The block diagram of the three-dimensional shape measuring apparatus which concerns on 2nd Embodiment. The figure which shows the measurement space which concerns on 2nd Embodiment. The schematic diagram of the optical system which concerns on 2nd Embodiment. The schematic diagram of the optical system which concerns on 2nd Embodiment. The block diagram of the three-dimensional shape measuring apparatus which concerns on 3rd Embodiment. The figure which shows the measurement space which concerns on 3rd Embodiment. The schematic diagram of the optical system which concerns on 3rd Embodiment. The block diagram of the three-dimensional shape measuring apparatus which concerns on 4th Embodiment. The figure which shows the measurement space which concerns on 4th Embodiment. The schematic diagram of the optical system which concerns on 4th Embodiment. The figure which shows the relationship between the shooting distance and contrast which concern on 1st Embodiment, or the relationship between a shooting distance and the brightness of a picked-up image. The figure which shows the relationship between the imaging distance which concerns on 1st Embodiment, and a measurement error. The arrangement plan of the three-dimensional shape measuring device concerning a 4th embodiment. The block diagram of the three-dimensional shape measuring apparatus which concerns on 5th Embodiment. The figure which shows the measurement space which concerns on 5th Embodiment. The schematic diagram of the optical system which concerns on 5th Embodiment.

(First embodiment)
With reference to FIG. 1, the structure of the three-dimensional shape measuring apparatus according to the first embodiment will be described. The three-dimensional shape measurement apparatus includes a projection unit 101, an imaging unit 102, and a control unit 103.

  The projection unit 101 is a projector that performs a projection operation of projecting pattern light that projects a predetermined projection pattern onto the target object 104. The projection unit 101 can project into the space indicated by the projection range 105. Assume that the projection unit 101 does not match the optical axis and the center of the projected image, like a projector used for upward projection in a conference room or the like.

  The photographing unit 102 is a camera that photographs the target object 104 onto which pattern light is projected. The photographing unit 102 can photograph the space indicated by the photographing range 106. The control unit 103 is a personal computer, for example, and controls operations of the projection unit 101 and the photographing unit 102. The control unit 103 also executes processing for measuring the three-dimensional shape of the target object 104.

  Next, the measurement space according to the first embodiment will be described with reference to FIG. The projection axis 107 is an axis from the projection unit 101 toward the center of the projection image, and does not coincide with the optical axis. The optical axis 108 is the optical axis of the imaging unit 102 (imaging axis toward the imaging center). An intersection 109 is a point where the projection axis 107 and the optical axis 108 intersect. The measurement space 110 is a space that is included in both the projection range 105 and the imaging range 106 and is defined by the projection range 105 and the imaging range 106. In the present embodiment, the intersection 109 is included in the measurement space, and is arranged so as to bisect the depth direction distance of the measurement space 110 when observed from the projection unit 101. The measurement surface 116 is the measurement surface closest to the projection unit 101 and the imaging unit 102 in the measurement space 110. The measurement surface 117 is the measurement surface farthest from the projection unit 101 and the imaging unit 102 in the measurement space 110. In the present embodiment, the intersection 109 is set inside the measurement space 110, but is not necessarily limited to the inside and may be outside.

  The three-dimensional shape measurement apparatus according to the present embodiment performs shape measurement by a spatial encoding method. First, the projection unit 101 projects a light / dark pattern 111 as shown in FIG. Then, the photographing unit 102 photographs the target object 104 on which the light and dark pattern 111 is projected. The control unit 103 processes the image photographed by the photographing unit 102 and measures the three-dimensional shape of the target object 104. More specifically, the light / dark edge position of the light / dark pattern 111 is detected, and projection is performed based on the principle of triangulation based on the angle formed by the projection axis of the projection unit 101 and the imaging axis of the imaging unit 102 corresponding to the edge position. The distance from the unit 101 and the imaging unit 102 to the target object 104 is calculated.

  In the present embodiment, a negative / positive intersection detection method is used as a method for detecting the edge position of the light / dark pattern 111. The negative / positive intersection detection method is a method in which the projection unit 101 continuously projects a pattern in which the light / dark position of the light / dark pattern 111 is switched, and the intersection of the intensity distribution of the image captured by the image capturing unit 102 is used as the edge position.

  In the negative / positive intersection detection method, it is generally known that the higher the contrast of a light and dark pattern photographed by the photographing unit 102, the higher the edge position detection accuracy. Further, the SN (ratio of signal to noise) of the photographing unit 102 is improved when the brightness of the image photographed by the photographing unit 102 is high. Therefore, the projection from the projection unit 101 has higher edge position detection accuracy when the brightness is higher.

  In the three-dimensional shape measurement apparatus according to the present embodiment, it is necessary to measure the shape with a precision higher than necessary over the entire measurement space 110. However, as shown in FIG. 16A, the image photographed by the photographing unit 102 has a high contrast at the focus position (focal position), but the contrast decreases when the image deviates from the focus position. As shown in FIG. 16B, when the distance from the photographing unit 102 is short, the capture angle becomes large and the image becomes bright, but when the distance from the photographing unit 102 is long, the capture angle becomes small and the image becomes small. Becomes darker.

  Therefore, when the focus position of the projection unit 101 is set to the intersection 109, the contrast on the measurement surface 116 decreases due to defocusing, but the captured image is bright because the measurement surface 116 is close to the imaging unit 102. On the other hand, on the measurement surface 117, the contrast is reduced due to defocusing, and the captured image is also dark because the measurement surface 117 is far from the imaging unit 102. Therefore, the relationship between the shooting distance and the measurement error is as shown in FIG. 17A, and the measurement accuracy is lower on the measurement surface 117 than on the measurement surface 116. Therefore, in the present embodiment, the focus position of the projection unit 101 is set to be far behind the intersection point 109 when viewed from the projection unit 101.

  FIG. 4 shows the state of the focus position of the photographing unit 102. The lens 114 schematically represents the photographing optical system of the photographing unit 102 as one lens, and the photographing element 115 converts the light that has entered from the lens 114 into an electrical signal. As shown in FIG. 4, the focus position of the photographing unit 102 is set to the intersection 109.

  On the other hand, FIG. 5 shows the focus position of the projection unit 101. The lens 112 schematically represents the projection optical system of the projection unit 101 as a single lens, and the display element 113 displays a light / dark pattern. As shown in FIG. 5, the focus position 118 of the projection unit 101 is set behind the intersection 109.

  With the configuration shown in FIGS. 4 and 5, as shown in FIG. 16C, the contrast reduction due to the defocus of the projection unit 101 on the measurement surface 116 is caused by the contrast reduction on the measurement surface 117. Bigger than. Accordingly, the relationship between the shooting distance and the measurement error is as shown in FIG. 17B, and when combined with the change in brightness of the shot image according to the distance from the shooting unit 102, the measurement accuracy of the measurement surface 116 is measured. The measurement accuracy of the measurement surface 117 is about the same. In addition, since the focus position of the projection unit 101 is behind the intersection 109, the reduction in contrast on the measurement surface 117 is small compared to when the focus position is at the intersection 109. Therefore, the measurement accuracy on the measurement surface 117 is improved as compared with the case where the focus position is at the intersection 109. That is, the measurement error is within a certain range over the entire photographing distance, and the accuracy is not drastically reduced, and a certain measurement accuracy can be obtained as a whole.

  As described above, by setting the focus position of the projection unit 102 behind the intersection 109, a certain measurement accuracy can be obtained in the entire measurement space 110. When the focus position of the projection unit 102 is set to the intersection point 109, in order to obtain the same measurement accuracy as the present embodiment in the entire measurement space 110, the imaging performance of the projection unit 101 or the imaging unit 102 is increased and the captured image is captured. It is necessary to improve the contrast or to increase the amount of light projected from the projection unit 101. However, since this is not necessary in this embodiment, it is not necessary to increase the imaging performance of the projection unit 101 and the imaging unit 102 more than necessary, and the number of lenses constituting the projection unit 101 and the imaging unit 102 can be reduced. As a whole, it leads to cost reduction. In addition, by reducing the output of the light source of the projection unit 101, the power consumption is reduced, and the heat generated from the light source is reduced, so that the cooling system can be made smaller, leading to miniaturization.

  Here, when the depth of the measurement space is large and the distance between the measurement surface 116 and the measurement surface 117 is further away, the difference between the brightness of the captured image on the measurement surface 116 and the brightness of the captured image on the measurement surface 117 is larger. Therefore, the focus position of the projection unit 101 is set to a position closer to the measurement surface 117. As a result, a decrease in contrast due to defocus on the measurement surface 117 is reduced, and a decrease in accuracy on the measurement surface 117 can be further reduced.

  When the contrast reduction due to the defocus of the lens 112 of the projection unit 101 is large, the focus position of the projection unit 101 is set to a position close to the intersection 109. As a result, a decrease in contrast due to defocus on the measurement surface 116 is reduced, and a decrease in accuracy on the measurement surface 116 can be further reduced.

  As a method for adjusting the focus position of the projection unit 101 to the back of the intersection 109, the focus position may be set to the back of the intersection 109 when designing the projection optical system of the projection unit 101. In addition, when the projection unit 101 has an autofocus function, a method for adjusting the focus by placing a focus adjustment chart at a position to be focused, or after adjusting the focus at the intersection 109, You may take the method of focusing on the back side using a lens. In addition, when the focus position is too deep, a portion where the measurement accuracy is lowered appears. Therefore, the focus position may be set to an appropriate position depending on the relationship between the contrast and the brightness of the image.

  Further, as a method for detecting the intersection 109, the projection unit 101 projects an image only at the center of the projection image, and the captured image is observed when the imaging unit 102 observes the screen arranged on the measurement surface 116 while moving the screen to the back. There is a method of setting the intersection 109 to the position where the center of the projected image comes to the center of.

  In this embodiment, three-dimensional shape measurement is performed by a spatial encoding method, and a negative / positive intersection detection method is used as a method for detecting an edge position. However, the method is not limited to the negative / positive intersection detection method, and a method of detecting an edge position using a differential filter or detecting the center of gravity of an intensity distribution may be used. Further, the three-dimensional shape measurement method is not limited to the spatial encoding method, and a phase shift method or a light cutting method for projecting a sine wave pattern may be used.

(Second Embodiment)
With reference to FIG. 6, the structure of the three-dimensional shape measuring apparatus which concerns on 2nd Embodiment is demonstrated. The three-dimensional shape measurement apparatus includes a projection unit 201, an imaging unit 202, and a control unit 203.

  The projection unit 201 is a projector that performs a projection operation of projecting pattern light onto the target object 204. The projection unit 201 can project into the space indicated by the projection range 205. The projection unit 201 is different from the first embodiment in that the optical axis coincides with the center of the projection image.

  The imaging unit 202 is a camera that captures the target object 204 onto which pattern light is projected. The photographing unit 202 can photograph the space indicated by the photographing range 206. The control unit 203 is a personal computer, for example, and controls operations of the projection unit 201 and the imaging unit 202. The control unit 203 also executes processing for measuring the three-dimensional shape of the target object 204.

  Next, a measurement space according to the second embodiment will be described with reference to FIG. The optical axis 207 is an axis from the projection unit 201 toward the center of the projection image, and coincides with the projection axis. An optical axis 208 is an optical axis of the imaging unit 202 (imaging axis toward the imaging center). The intersection point 209 is a point where the optical axis 207 and the optical axis 208 intersect. The measurement space 210 is a space that is included in both the projection range 205 and the imaging range 206 and is defined by the projection range 205 and the imaging range 206. In the present embodiment, the intersection point 209 is included in the measurement space and is arranged so as to bisect the depth direction distance of the measurement space 210 when observed from the projection unit 201. The measurement surface 216 is the measurement surface closest to the projection unit 201 and the imaging unit 202 in the measurement space 210. The measurement surface 217 is the measurement surface farthest from the projection unit 201 and the imaging unit 202 in the measurement space 210. In the present embodiment, the intersection 209 is set inside the measurement space 210, but is not necessarily limited to the inside and may be outside.

  Similar to the first embodiment, the three-dimensional shape measurement apparatus according to the present embodiment performs shape measurement by the spatial encoding method, and uses the negative / positive intersection detection method as the edge position detection method.

  Also in the present embodiment, the focus position of the photographing unit 202 is adjusted to the intersection point 209, and the focus position of the projection unit 201 is adjusted to be farther than the intersection point 209.

  FIG. 8 shows the state of the focus position of the photographing unit 202. The lens 214 schematically represents the photographing optical system of the photographing unit 202 as one lens, and the photographing element 215 converts light that has entered from the lens 214 into an electrical signal. As shown in FIG. 8, the focus position of the photographing unit 202 is adjusted to the intersection point 209.

  On the other hand, FIG. 9 shows the state of the focus position of the projection unit 201. The lens 212 schematically represents the projection optical system of the projection unit 201 as one lens, and the display element 213 displays a light / dark pattern. As shown in FIG. 9, the focus position of the projection unit 201 is set farther than the intersection 209.

  With the configuration shown in FIGS. 8 and 9, the contrast reduction due to the defocus of the projection unit 201 on the measurement surface 216 is larger than the contrast reduction on the measurement surface 217. Therefore, the measurement accuracy of the measurement surface 216 and the measurement accuracy of the measurement surface 217 are comparable when combined with the change in brightness of the captured image due to the distance from the imaging unit 202. In addition, since the focus position of the projection unit 201 is farther than the intersection point 209, the reduction in contrast on the measurement surface 217 is small compared to when the focus position is at the intersection point 209. Therefore, the measurement accuracy on the measurement surface 217 is improved as compared with the case where the focus position is at the intersection 209. That is, the measurement error is within a certain range over the entire photographing distance, and the accuracy is not drastically reduced, and a certain measurement accuracy can be obtained as a whole.

  As described above, by setting the focus position of the projection unit 201 farther from the intersection 209, it is possible to obtain a certain measurement accuracy over the entire measurement space 210. When the focus position of the projection unit 201 is set to the intersection point 209, in order to obtain the same measurement accuracy as that of the present embodiment in the entire measurement space 210, the imaging performance of the projection unit 201 or the imaging unit 202 is increased and the captured image is captured. Or the amount of light projected from the projection unit 201 needs to be increased. However, since this is not necessary in the present embodiment, it is not necessary to increase the imaging performance of the projection unit 201 and the imaging unit 202 more than necessary, and the number of lenses constituting the projection unit 201 and the imaging unit 202 can be reduced. As a whole, it leads to cost reduction. Further, by reducing the output of the light source of the projection unit 201, the power consumption is reduced, and the heat generated from the light source is reduced, so that the cooling system can be made smaller, leading to miniaturization.

(Third embodiment)
With reference to FIG. 10, the structure of the three-dimensional shape measuring apparatus which concerns on 3rd Embodiment is demonstrated. The three-dimensional shape measurement apparatus includes a projection unit 301, an imaging unit 302, and a control unit 303.

  The projection unit 301 is a projector that performs a projection operation of projecting pattern light onto the target object 304. The projection unit 301 can project into the space indicated by the projection range 305. The projection unit 301 is different from the first embodiment in that the optical axis and the center of the projection image coincide with each other.

  The imaging unit 302 is a camera that captures the target object 304 onto which pattern light is projected. The photographing unit 302 can photograph the space indicated by the photographing range 306. The control unit 303 is a personal computer, for example, and controls operations of the projection unit 301 and the imaging unit 302. The control unit 303 also executes processing for measuring the three-dimensional shape of the target object 304.

  Next, a measurement space according to the third embodiment will be described with reference to FIG. An optical axis 307 is an axis from the projection unit 301 toward the center of the projection image, and coincides with the projection axis. An optical axis 308 is an optical axis of the imaging unit 302 (imaging axis toward the imaging center). The intersection point 309 is a point where the optical axis 307 and the optical axis 308 intersect. The measurement space 310 is a space that is included in both the projection range 305 and the imaging range 306 and is defined by the projection range 305 and the imaging range 306. In the present embodiment, the intersection point 309 is included in the measurement space. The measurement surface 316 is the measurement surface closest to the projection unit 301 and the imaging unit 302 in the measurement space 310. The measurement surface 317 is the measurement surface farthest from the projection unit 301 and the imaging unit 302 in the measurement space 310. In this embodiment, the intersection point 309 is set inside the measurement space 310, but is not necessarily limited to the inside and may be outside.

  Similar to the first embodiment, the three-dimensional shape measurement apparatus according to the present embodiment performs shape measurement by the spatial encoding method, and uses the negative / positive intersection detection method as the edge position detection method.

  In the present embodiment, the focus position of the projection unit 301 and the focus position of the imaging unit 302 are set to the back of the intersection point 309.

  FIG. 12 shows the focus positions of the projection unit 301 and the imaging unit 302. The lens 312 schematically represents the projection optical system of the projection unit 301 as one lens, and the display element 313 displays a light / dark pattern. The lens 314 schematically represents the imaging optical system of the imaging unit 302 as a single lens, and the imaging element 315 converts light that has entered from the lens 314 into an electrical signal. As shown in FIG. 12, the focus position 319 of the projection unit 301 and the focus position 320 of the imaging unit 302 are set farther from the intersection 309. Further, the focus position 319 of the projection unit 301 and the focus position 320 of the imaging unit 302 are on a plane perpendicular to the optical axis 307.

  With the configuration shown in FIG. 12, the contrast reduction due to the defocus of the projection unit 301 and the imaging unit 302 on the measurement surface 316 is larger than the contrast reduction on the measurement surface 317. Therefore, the measurement accuracy of the measurement surface 316 and the measurement accuracy of the measurement surface 317 are comparable when combined with the change in brightness of the captured image due to the distance from the imaging unit 302. In addition, since the focus positions of the projection unit 301 and the imaging unit 302 are farther from the intersection point 309, the contrast reduction on the measurement surface 317 is smaller than when the focus position is at the intersection point 309. Therefore, the measurement accuracy on the measurement surface 317 is improved as compared with the case where the focus position is at the intersection point 309. That is, the measurement error is within a certain range over the entire photographing distance, and the accuracy is not drastically reduced, and a certain measurement accuracy can be obtained as a whole.

  In addition, when the influence of contrast reduction due to defocus of the projection optical system of the projection unit 301 is small, the contrast of the image through the entire system of projection and photographing is the same even if the focus position of the projection unit 301 is behind the intersection 309. It becomes the best near the intersection 309 that is the focus position of the imaging unit 302, and the effect of setting the focus position of the projection unit 301 behind the intersection 309 is reduced. Therefore, by setting the focus positions of the projection unit 301 and the imaging unit 302 both behind the intersection point 309, the contrast of the image through the entire system of projection and imaging is surely best at the back of the intersection point 309. The effect of the present invention is further increased.

  As described above, by setting the focus position of the projection unit 301 far from the intersection 309, it is possible to obtain a certain measurement accuracy in the entire measurement space 310. When the focus positions of the projection unit 301 and the imaging unit 302 are adjusted to the intersection point 309, the imaging performance of the projection unit 301 or the imaging unit 302 is set in order to obtain the same measurement accuracy as the present embodiment in the entire measurement space 310. It is necessary to increase the contrast of the photographed image or increase the amount of light projected from the projection unit 301. However, since this is not necessary in the present embodiment, it is not necessary to increase the imaging performance of the projection unit 301 and the imaging unit 302 more than necessary, and the number of lenses constituting the projection unit 301 and the imaging unit 302 can be reduced. As a whole, it leads to cost reduction. Further, by reducing the output of the light source of the projection unit 301, the power consumption can be reduced, and the heat generated from the light source can be reduced, so that the cooling system can be reduced, leading to miniaturization.

  As in the present embodiment, since the focus positions of the projection unit 301 and the imaging unit 302 are on a plane perpendicular to the optical axis 307 of the projection unit 301, the projection unit 301 is in focus adjustment of the projection unit 301 and the imaging unit 302. The focus can be adjusted by placing the chart at the same distance from. Therefore, since the focus adjustment of the projection unit 301 and the imaging unit 302 can be performed without moving the chart, the number of steps for focus adjustment can be reduced.

(Fourth embodiment)
With reference to FIG. 13, the structure of the three-dimensional shape measuring apparatus which concerns on 4th Embodiment is demonstrated. The three-dimensional shape measurement apparatus includes a projection unit 401, an imaging unit 402, and a control unit 403.

  The projection unit 401 is a projector that performs a projection operation of projecting pattern light onto the target object 404. The projection unit 401 can project into the space indicated by the projection range 405. The projection unit 401 is different from the first embodiment in that the optical axis and the center of the projection image coincide with each other.

  The imaging unit 402 is a camera that captures the target object 404 onto which pattern light is projected. The photographing unit 402 can photograph the space indicated by the photographing range 406. The control unit 403 is, for example, a personal computer, and controls the operations of the projection unit 401 and the photographing unit 402. The control unit 403 also executes processing for measuring the three-dimensional shape of the target object 404.

  Next, a measurement space according to the fourth embodiment will be described with reference to FIG. The optical axis 407 is an axis from the projection unit 401 toward the center of the projection image, and coincides with the projection axis. An optical axis 408 is an optical axis of the imaging unit 402 (imaging axis toward the imaging center). As shown in FIG. 18, the optical axis 407 and the optical axis 408 do not have an intersection, but a proximity point on the optical axis 407 (on the projection axis) when the distance between the optical axis 407 and the optical axis 408 is the shortest. 409. This may be caused by a case where there is no intersection on the optical axis on purpose to shift the measurement space, or may be caused by an attachment error between the projection unit 401 and the imaging unit 402. The measurement space 410 is a space that is included in both the projection range 405 and the imaging range 406 and is defined by the projection range 405 and the imaging range 406. In the present embodiment, the proximity point 409 is included in the measurement space. The measurement surface 416 is the measurement surface closest to the projection unit 401 and the imaging unit 402 in the measurement space 410. The measurement surface 417 is the measurement surface farthest from the projection unit 401 and the imaging unit 402 in the measurement space 410. In the present embodiment, the proximity point 409 is set inside the measurement space 410, but is not necessarily limited to the inside and may be outside.

  Similar to the first embodiment, the three-dimensional shape measurement apparatus according to the present embodiment performs shape measurement by the spatial encoding method, and uses the negative / positive intersection detection method as the edge position detection method.

  In the present embodiment, the focus position of the projection unit 401 and the focus position of the imaging unit 402 are set to the back of the proximity point 409.

  FIG. 15 shows the focus positions of the projection unit 401 and the imaging unit 402. The lens 412 schematically represents the projection optical system of the projection unit 401 as one lens, and the display element 413 displays a light / dark pattern. The lens 414 schematically represents the photographing optical system of the photographing unit 402 as one lens, and the photographing element 415 converts the light that has entered from the lens 414 into an electrical signal. As shown in FIG. 15, the focus position 419 of the projection unit 401 and the focus position 420 of the imaging unit 402 are set to the back of the proximity point 409.

  With the configuration shown in FIG. 15, since the focus position of the projection unit 401 and the imaging unit 402 is farther from the proximity point 409, the measurement surface 417 is compared to the case where the focus position is at the proximity point 409. The decrease in contrast is small. Therefore, the measurement accuracy on the measurement surface 417 is improved as compared with the case where the focus position is at the proximity point 409. That is, the measurement error is within a certain range over the entire photographing distance, and the accuracy is not drastically reduced, and a certain measurement accuracy can be obtained as a whole.

  As described above, by setting the focus position of the projection unit 401 farther than the proximity point 409, a certain measurement accuracy can be obtained in the entire measurement space 410. When the focus positions of the projection unit 401 and the imaging unit 402 are adjusted to the proximity point 409, the imaging performance of the projection unit 401 or the imaging unit 402 is obtained in order to obtain the same measurement accuracy as the present embodiment in the entire measurement space 410. To improve the contrast of the captured image, or to increase the amount of light projected from the projection unit 401. However, since this is not necessary in the present embodiment, it is not necessary to increase the imaging performance of the projection unit 401 and the imaging unit 402 more than necessary, and the number of lenses constituting the projection unit 401 and the imaging unit 402 can be reduced. As a whole, it leads to cost reduction. In addition, by reducing the output of the light source of the projection unit 401, the power consumption is reduced, and the heat generated from the light source is reduced, so that the cooling system can be reduced, leading to miniaturization.

  As a method for detecting the proximity point 409, the projection unit 401 projects an image only at the center of the projection image, and when the imaging unit 402 observes the screen arranged on the measurement surface 416 while moving the screen to the back, There is a method in which the proximity point 409 is a position where the center and the center of the projected image are closest.

(Fifth embodiment)
With reference to FIG. 19, the structure of the three-dimensional shape measuring apparatus which concerns on 5th Embodiment is demonstrated. The three-dimensional shape measurement apparatus includes a projection unit 501, an imaging unit 502, an imaging unit 503 (second imaging unit), and a control unit 504.

  The projection unit 501 is a projector that executes a projection operation for projecting pattern light onto the target object 505. The projection unit 501 can project into the space indicated by the projection range 506. The projection unit 501 is different from the first embodiment in that the optical axis coincides with the center of the projection image.

  The photographing unit 502 and the photographing unit 503 are cameras that photograph the target object 504 on which the pattern light is projected. The photographing unit 502 can photograph the space indicated by the photographing range 507. The photographing unit 503 can photograph the space indicated by the photographing range 508. The control unit 504 is, for example, a personal computer, and controls operations of the projection unit 501, the imaging unit 502, and the imaging unit 503. The control unit 504 also executes processing for measuring the three-dimensional shape of the target object 505.

  Next, a measurement space according to the fifth embodiment will be described with reference to FIG. The optical axis 509 is an axis from the projection unit 501 toward the center of the projection image, and coincides with the projection axis. An optical axis 510 is an optical axis of the imaging unit 502 (imaging axis toward the imaging center). The optical axis 511 is the optical axis of the imaging unit 503 (imaging axis toward the imaging center). The intersection 512 is a point where the optical axis 509 intersects with the optical axis 510 and the optical axis 511. The measurement space 513 is a space that is included in both the projection range 506, the shooting range 507, and the shooting range 508, and is defined by the projection range 506, the shooting range 507, and the shooting range 508. In the present embodiment, the intersection 512 is included in the measurement space. The measurement surface 514 is the measurement surface closest to the projection unit 501, the imaging unit 502, and the imaging unit 503 in the measurement space 513. The measurement surface 515 is the measurement surface farthest from the projection unit 501, the imaging unit 502, and the imaging unit 503 in the measurement space 513. In this embodiment, the intersection 512 is set inside the measurement space 513, but is not necessarily limited to the inside and may be outside. Further, the optical axis 509, the optical axis 510, and the optical axis 511 do not necessarily need to have an intersection at one point.

  In the three-dimensional shape measurement apparatus according to the present embodiment, unlike the first to fourth embodiments, the target object 505 projected by the projection unit 501 is obtained from each image captured by the imaging unit 502 and the imaging unit 503. An active stereo method (stereo method) that calculates the distance to the target object 505 using the principle of triangulation is adopted.

  In the active stereo method, a feature amount such as an edge of a pattern projected onto a target object 505 by a projection unit 501 is detected from a captured image, and triangulation is performed by associating images captured by the imaging unit 502 and the imaging unit 503. Therefore, the higher the contrast of the projection pattern of the target object 505 photographed by the photographing unit 502 and the photographing unit 503, the higher the edge position detection accuracy. In addition, the SN of the photographing unit 502 and the photographing unit 503 is improved when the brightness of the images photographed by the photographing unit 502 and the photographing unit 503 is high. Therefore, the projection from the projection unit 501 has higher edge position detection accuracy when the brightness is higher.

  Therefore, also in the present embodiment, the focus positions of the projection unit 501, the imaging unit 502, and the imaging unit 503 are adjusted to the far side from the intersection 512.

  FIG. 21 illustrates the focus positions of the projection unit 501, the imaging unit 502, and the imaging unit 503. The lens 516 schematically represents the projection optical system of the projection unit 501 as one lens, and the display element 517 displays a light / dark pattern. The lens 518 schematically represents the photographing optical system of the photographing unit 502 as one lens, and the photographing element 519 converts light that has entered from the lens 518 into an electrical signal. The lens 520 schematically represents the photographing optical system of the photographing unit 503 as a single lens, and the photographing element 521 converts light that has entered from the lens 520 into an electrical signal. As shown in FIG. 21, the focus position 522 of the projection unit 501, the focus position 523 of the imaging unit 502, and the focus position 524 of the imaging unit 503 are set farther from the intersection 512. Further, the focus position 522 of the shadow portion 501, the focus position 523 of the imaging unit 502, and the focus position 524 of the imaging unit 503 are on a plane perpendicular to the optical axis 509.

  With the configuration shown in FIG. 21, the contrast reduction due to defocusing of the projection unit 501, the imaging unit 502, and the imaging unit 503 on the measurement surface 514 is larger than the contrast reduction on the measurement surface 515. Therefore, the measurement accuracy of the measurement surface 514 and the measurement accuracy of the measurement surface 515 are comparable when combined with the change in brightness of the captured image depending on the distance from the imaging unit 502 and the imaging unit 503. In addition, since the focus positions of the projection unit 501, the imaging unit 502, and the imaging unit 503 are farther from the intersection 512, the contrast reduction on the measurement surface 515 is smaller than when the focus position is at the intersection 512. Therefore, the measurement accuracy on the measurement surface 515 is improved as compared with the case where the focus position is at the intersection 512. That is, the measurement error is within a certain range over the entire photographing distance, and the accuracy is not drastically reduced, and a certain measurement accuracy can be obtained as a whole.

  As described above, by setting the focus positions of the projection unit 501, the image capturing unit 502, and the image capturing unit 503 farther from the intersection 512, it is possible to obtain a certain measurement accuracy in the entire measurement space 513. When the focus positions of the projection unit 501, the imaging unit 502, and the imaging unit 503 are adjusted to the intersection point 512, the projection unit 501 or the imaging unit 502, It is necessary to improve the contrast of the captured image by improving the imaging performance of the imaging unit 503 or to increase the amount of light projected from the projection unit 501. However, since this is not necessary in the present embodiment, it is not necessary to improve the imaging performance of the projection unit 501, the imaging unit 502, and the imaging unit 503 more than necessary, and the projection unit 501, the imaging unit 502, and the imaging unit 503 are configured. The number of lenses can be reduced, leading to cost reduction as a whole. In addition, by reducing the output of the light source of the projection unit 501, power consumption can be reduced and the cooling system can be reduced because heat generated from the light source is reduced, leading to miniaturization.

  As in the present embodiment, the projection unit 501, the imaging unit 502, and the focus position of the imaging unit 503 are on a plane perpendicular to the optical axis 509 of the projection unit 501, so that the projection unit 501, the imaging unit 502, and the imaging unit. At the time of focus adjustment 503, the focus can be adjusted by placing the chart at the same distance from the projection unit 501. Therefore, since the focus adjustment of the projection unit 501, the imaging unit 502, and the imaging unit 503 can be performed without moving the chart, the number of man-hours during the focus adjustment can be reduced.

(Other embodiments)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (5)

Projection means for projecting pattern light having a bright part and a dark part onto a target object;
Photographing means for photographing the target object onto which the pattern light is projected;
Measuring means for measuring the three-dimensional shape of the target object based on the captured image;
The focal position of the projection optical system of the projection means is behind the intersection of the projection axis of the projection means and the imaging axis of the imaging means with respect to the projection means, or the projection axis of the projection means and the imaging means Is set behind the point on the projection axis that is closest to the shooting axis of
The contrast value between the bright part and the dark part in the image photographed by the photographing unit is greater than the point on the photographing axis where the intersection or the projection axis of the projecting unit and the photographing axis of the photographing unit are closest to each other. A three-dimensional shape measuring apparatus having a maximum value in a back area with respect to the photographing means. Projection means for projecting pattern light onto a target object;
Photographing means for photographing the target object onto which the pattern light is projected;
Measuring means for measuring the three-dimensional shape of the target object based on the captured image;
The focal position of the projection optical system of the projection means is behind the intersection of the projection axis of the projection means and the imaging axis of the imaging means with respect to the projection means, or the projection axis of the projection means and the imaging means Is set behind the point on the projection axis that is closest to the shooting axis of
The focal position of the photographing optical system of the photographing means is farthest from the intersection of the projection axis of the projection means and the photographing axis of the photographing means with respect to the photographing means, or the projection axis and the photographing axis are the most. A three-dimensional shape measuring apparatus, characterized in that the three-dimensional shape measuring apparatus is set behind a point on the imaging axis that is close.   The focal position of the projection optical system of the projection unit and the focal position of the imaging optical system of the imaging unit are on the projection axis or a plane perpendicular to the imaging axis. Three-dimensional shape measuring device. The projection means projects a light and dark pattern onto the target object,
The three-dimensional shape measuring apparatus according to claim 2 or 3, wherein the measuring means measures the shape of the target object by a spatial encoding method. The projection means projects a sine wave pattern onto the target object,
The three-dimensional shape measurement apparatus according to claim 2, wherein the measurement unit measures the shape of the target object by a phase shift method.

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