JP2018096893A - Three-dimensional measurement device and three-dimensional measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a three-dimensional measurement device and three-dimensional measurement method that can improve measurement accuracy of a measured object.SOLUTION: A three-dimensional measurement device comprises: a projector (10) that projects pattern light toward a loading face (13) side where a measured object (2) is loaded; an imaging device (9) that images reflection light from the loading face side; a storage device (16) that stores conversion information regarding a relationship expression between a phase for each pixel of an imaging image by the imaging device and a height with respect to a reference face set between the imaging device and the loading face in association with each of a plurality of sections in a direction going across the reference face; and a computation device (15) that calculates the height with respect to the reference face on the basis of a measurement phase obtained from the imaging image of the measured object having the pattern light projected and the conversion information of a section corresponding to the measurement phase.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a three-dimensional measurement apparatus and a three-dimensional measurement method that can measure the shape (height from a reference) of a measurement object.

  As a method for measuring the shape of a measurement object, three-dimensional measurement based on a phase shift method is known (for example, see Patent Document 1). In the measurement method disclosed in Patent Document 1, the phase of the reference plane is acquired as the reference phase for all pixels, and a sine wave pattern is obtained by projecting a sine wave pattern onto the measurement target when measuring the measurement target. The height of the measurement object can be obtained by subtracting the reference phase from the phase calculated from the captured image. Specifically, the phase at a predetermined position in the measurement object is φa, the reference phase is φb, the pitch of the sine wave pattern grating is Pitch, and the incident angle when the sine wave pattern is projected onto the measurement object or the reference plane is As α, the height of the measurement object is calculated using an equation of Height = Pitch × (φa−φb) / 2π × sin α.

JP 2006-84286 A

  However, the relationship between height and phase actually exhibits nonlinear characteristics due to the influence of optical characteristics. For this reason, there is a possibility that an error may occur in the measurement method using the above one equation, and as a result, it may be difficult to accurately grasp the shape of the measurement object.

  This invention is made | formed in view of such a situation, The objective is to provide the three-dimensional measuring apparatus and three-dimensional measuring method which can raise a measurement precision.

The three-dimensional measuring apparatus of the present invention is proposed to achieve the above object, and is a three-dimensional measuring apparatus that measures the shape of a measurement object,
A projector that projects pattern light toward a placement surface on which the measurement object is placed;
A photographing machine for photographing the reflected light from the mounting surface side,
The conversion information relating to the relational expression between the phase of each pixel of the image captured by the camera and the height with respect to the reference surface set between the camera and the placement surface in the direction intersecting the reference surface. A storage device stored corresponding to each of a plurality of sections;
Based on the measurement phase obtained from the captured image of the measurement object onto which the pattern light is projected and the conversion information of the section corresponding to the measurement phase, the height of the measurement object with respect to the reference plane is calculated. A computing device to calculate,
It is characterized by providing.

  According to the present invention, as compared with the configuration in which the height is obtained from the phase based on one conventional approximate expression, the height is obtained from the phase by the relational expression corresponding to each of the plurality of sections, thereby providing an optical Errors due to the influence of characteristics can be reduced. Thereby, it is possible to measure a three-dimensional shape with higher accuracy.

  In the above configuration, the conversion information is information related to an approximate expression obtained for each section based on the sample phase and the height with respect to the reference plane at a plurality of measurement points that respectively define the ends of the plurality of sections. It is desirable to adopt a configuration.

  According to this, since the approximate expression is obtained for each section based on the sample phase at the measurement point and the height with respect to the reference plane, the relational expression can be acquired more easily.

  Further, in the above configuration, the conversion information includes the sample phase of each of the measurement points defining the same section and the height relative to the reference plane, the sample phase at the section measurement point set between these measurement points, and A configuration that is information about an approximate expression obtained by least square approximation based on the height with respect to the reference plane may be employed.

  According to this, the sample phase at each measurement point that defines the same section and the height relative to the reference plane are set to the sample phase at the section measurement point further set between these measurement points and the height relative to the reference plane. In addition, the three-dimensional shape can be measured with higher accuracy by obtaining an approximate expression by least square approximation.

The three-dimensional measurement method of the present invention includes a projector that projects pattern light toward a placement surface on which a measurement object is placed, and a photographing device that photographs reflected light from the placement surface. A three-dimensional measurement method for measuring the shape of the measurement object in a three-dimensional measurement apparatus comprising:
A direction that intersects the reference plane with conversion information relating to a relational expression between a phase for each pixel of an image captured by the camera and a height relative to a reference plane set between the camera and the mounting surface. Conversion information acquisition step to acquire for each of the plurality of sections,
Based on the measurement phase obtained from the captured image of the measurement object onto which the pattern light is projected and the conversion information of the section corresponding to the measurement phase, the height of the measurement object with respect to the reference plane is calculated. A height calculating step to calculate,
It is characterized by having.

It is a block diagram explaining the structure of one form of the three-dimensional measuring apparatus of this invention. It is a flowchart explaining the flow of a conversion information acquisition process. It is a graph which shows the relationship between the sample phase and height in each measurement point. It is a flowchart explaining the measurement process of a measurement object. It is a graph which shows the relationship between the sample phase and height of each measurement point in 2nd Embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. In the embodiments described below, various limitations are made as preferred specific examples of the present invention. However, the scope of the present invention is not limited to the following description unless otherwise specified. However, the present invention is not limited to these embodiments.

  FIG. 1 is a block diagram showing a configuration of an embodiment of a three-dimensional measuring apparatus 1 according to the present invention. The three-dimensional measuring apparatus 1 in this embodiment includes a Z stage 3, a measuring instrument group 5, a computer 6, a display device 7 such as a liquid crystal display, and the like, and the shape of the measuring object 2 (high from the reference plane). ) Is measured using the phase shift method. The measurement object 2 is placed on the placement plate 12 set on the Z stage 3. The placement surface 13 which is the upper surface of the placement plate 12 (the surface facing the measuring instrument group 5) also functions as a measurement surface described later. The mounting plate 12 is configured to be movable in the Z direction, that is, the direction approaching or moving away from the measuring instrument group 5 by the lifting mechanism of the Z stage 3.

  The measuring machine group 5 in the present embodiment includes a photographing machine 9, a projector 10, and a height measuring machine 11. The projector 10 includes a light source, a pattern grating, a lens, and the like (not shown), and has a stripe shape due to brightness and darkness of the luminance value toward the placement surface 13 (measurement surface) or the measurement object 2 placed on the placement surface 13. A sine wave pattern P (corresponding to the pattern light in the present invention) P is projected. Hereinafter, the sine wave pattern P actually projected on the measurement object 2 or the placement surface 13 (measurement surface) is also referred to as a projection pattern. The projector 10 can shift the phase of the projection pattern by moving the pattern grating in the direction intersecting the optical axis. The photographing machine 9 includes a lens, an image sensor (CCD), and the like (not shown), receives reflected light from the mounting surface 13 (measurement surface) on which the projection pattern is projected and the measurement object 2 by the image sensor, and takes a captured image. The data is converted and output to the computer 6. The height measuring device 11 is composed of, for example, a laser distance meter, irradiates a laser beam toward the mounting surface 13 and receives reflected light reflected by the mounting surface 13, and measures the measurement surface based on the light receiving state. The distance to the mounting surface 13 (position in the Z direction) is measured. The measurement value of the height measuring device 11 is converted as height data and output to the computer 6. That is, the height measuring device 11 is used to measure the height in the Z direction of the measurement surface. The height measuring device 11 is not limited to one using laser light, and any device that can measure the distance to the mounting surface 13 may be used. Further, the measurement surface is not necessarily limited to the placement surface 13 of the placement plate 12, and a surface different from the placement surface 13 may be employed.

  The computer 6 in this embodiment includes a calculation unit 15 (corresponding to the calculation device in the present invention) and a storage unit 16 (corresponding to the storage device in the present invention). The storage unit 16 includes, for example, a hard disk drive, and the storage unit 16 stores an operation system, various application programs, other calculation data, and the like. The calculation unit 15 includes a CPU, a ROM, a RAM, and the like (not shown), and performs various processes such as image processing according to the operation system stored in the storage unit 16. Further, photographic image data (hereinafter simply referred to as a photographic image) of the measurement surface or measurement object 2 input from the photographic machine 9 is stored in the storage unit 16. Further, as will be described later, the storage unit 16 stores conversion information related to the relational expression between the phase of the projection pattern and the height in the Z direction (relative position with respect to the reference surface) between the measuring instrument group 5 and the mounting surface 13. It is stored in correspondence with each of a plurality of sections in between.

  Next, the conversion information acquisition step that is executed before the measurement target 2 is actually measured in the three-dimensional measurement apparatus 1 having the above-described configuration will be described.

  FIG. 2 is a flowchart for explaining the flow of the conversion information acquisition process. First, a plurality of sections are set within a predetermined range in the Z direction between the mounting surface 13 of the mounting plate 12 lowered to the bottom dead center in the Z direction and the measuring instrument group 5 (step S1). The predetermined range is arbitrarily determined based on the size (height) of the measurement object 2. That is, it is determined in the range in which the measurement object 2 enters in the Z direction. In the present embodiment, the predetermined range is set to a range of ± 1 mm with respect to a virtual reference plane described later. The placement surface 13 at the bottom dead center is set as a measurement point A that is the lower limit value of this range, and from there, a fixed interval (for example, 0) toward the upper side in the Z direction (the measuring instrument group 5 side). A total of 5 measurement points of B, C, D, and E are set in order. For this reason, in this embodiment, the section AB between the measurement point A and the measurement point B, the section BC between the measurement point B and the measurement point C, and the section CD between the measurement point C and the measurement point D. , And a total of four sections of a section DE between the measurement point D and the measurement point E are set. Measurement points A to E define the end of each section. In addition, the placement surface 13 arranged at each measurement point at the time of acquiring the sample phase described below functions as a measurement surface. And the measurement surface when located in the measurement point C among the said measurement points is made into a reference plane in this embodiment. That is, a measurement range of ± 1 mm is determined with the measurement point C as 0 (reference plane). Of course, the position of the reference plane, the number of sections (the number of measurement points), and the interval between them can be arbitrarily determined based on the height difference of the unevenness of the surface of the measurement object 2.

  Next, the mounting surface 13 as a measurement surface is sequentially moved and arranged at each measurement point set as described above, and the sample phase is acquired by the phase shift method in each. That is, according to a predetermined measurement order, for example, when the measurement point A is designated at the first designated height, the placement surface 13 is moved and arranged at the measurement point A by the Z stage 3 (step S2). The height of the mounting surface 13 is adjusted based on distance information detected by the height measuring device 11. In the present embodiment, since the height of the mounting surface 13 (measurement surface) at the measurement point is based on the detection value of the height measuring instrument 11, for example, the mounting surface 13 is in the Z direction. Even when the position in the Z direction is not constant in the plane due to the slight inclination, when it is referred to as “the height of the mounting surface 13 at the measurement point”, it is uniformly detected by the height measuring device 11. It is assumed that the height is based on

  Subsequently, the sample phase φ is obtained by the phase shift method at the measurement point (step S3). That is, the calculation unit 15 projects the sine wave pattern P toward the placement surface 13 as the measurement surface arranged at the measurement point by the projector 10 and images the projection pattern on the measurement surface by the photographing device 9. At this time, the phase of the sine wave pattern P is shifted a plurality of times at regular intervals and photographed each time, and the photographed image is stored in the storage unit 16. For example, captured images of three projection patterns are acquired by shifting the phase by 2π / 3. Then, the phase is obtained for each pixel as the sample phase from the luminance value of each captured image. Various well-known methods can be adopted as a method for calculating the phase. Then, the sample phase is obtained for all the pixels, is associated with the coordinates (X, Y) of each pixel, and is stored in the storage unit 16 as the sample phase φA at the measurement point A. Note that the incident angle and direction of the sine wave pattern P with respect to the measurement surface and the measurement object 2 are not limited to those illustrated, but may be a more suitable incident angle according to the uneven shape of the surface of the measurement object 2. Can be set.

  Next, it is determined whether or not the sample phase φ has been acquired for all of the predetermined measurement points (step S4). If there is a measurement point for which the sample phase φ has not yet been acquired (No), the process proceeds to step S2. Returning, the placement surface 13 is moved / placed to the next measurement point (step S2), and the sample phase is acquired for all the pixels by the phase shift method at the measurement point in the same manner as described above (step S3). On the other hand, if it is determined in step S4 that the sample phase has been acquired for all of the predetermined measurement points (Yes), then the phase and high values for all pixels are determined for each section based on the sample phase at each measurement point. A relational expression (approximate expression) is calculated (step S5).

FIG. 3 is a graph showing the relationship between the sample phase at each measurement point and the height of the measurement point in the Z direction (relative position from the reference plane) for a predetermined pixel. In the figure, the horizontal axis indicates the phase, and the vertical axis indicates the height. As described above, since the sample phases φA to φE corresponding to the respective measurement points A to E are acquired for each pixel, it can be plotted as shown in FIG. Then, the calculation unit 15 calculates an approximate expression (relational expression) for the phase and height for each of the sections AB, BC, CD, and DE based on the height of the measurement points A to E and the sample phases φA to φB. calculate. That is, for example, the approximate expression of the section AB is a linear expression such as the following (1) where the height is Hab, the slope is Sab, and the intercept is Iab.
Hab = Sab × φ + Iab (1)
Similarly, approximate expressions for the sections BC, CD, and DE are obtained as follows.
Hbc = Sbc × φ + Ibc (2)
Hcd = Scd × φ + Icd (3)
Hde = Sde × φ + Ide (4)
If an approximate expression is obtained for each section, the calculation unit 15 stores, for example, the inclination and intercept of the approximate expression in the storage unit 16 in association with each section and each pixel as conversion information about the phase and height. (Step S6). Of course, the conversion information is not limited to the slope and intercept of the approximate expression, and any information that can uniquely identify the approximate expression may be used. The conversion information acquisition process is performed as described above. In addition, regarding the conversion information, it is acquired in advance at the stage before shipment as a product of the three-dimensional measurement apparatus 1 and is stored in the storage unit 16 as a preset, and is preset according to the size (height difference) of the unevenness to be measured and the measurement application. Can be adopted. Thereby, it becomes possible to measure more rapidly.

  FIG. 4 is a flowchart for explaining a step of actually measuring the shape of the measurement object 2 using the conversion information (corresponding to a height calculation step in the present invention). First, the measurement object 2 is placed on the placement surface 13 (step S10). Subsequently, the placement surface 13 is arranged at the measurement point (step S11). For example, when A is designated as a measurement point, the mounting surface 13 is moved and arranged at the measurement point A by the Z stage 3. Subsequently, the phase is acquired as the measurement phase for each pixel based on the captured image of the projection pattern of the measurement object 2 on the placement surface 13 arranged at the measurement point (step S12). That is, the calculation unit 15 projects the sine wave pattern P onto the measurement object 2 using the projector 10 and images the measurement object 2 using the camera 9. Then, captured images with different phases of the projection pattern are acquired, and a measurement phase φx is obtained for each pixel from each captured image. The obtained measurement phase φx is stored in the storage unit 16 in association with the coordinates of the pixels.

  Next, the calculation unit 15 searches for a section corresponding to the measurement phase φx obtained as described above (step S13), and corresponds to the corresponding section from the conversion information stored in the storage unit 16. Read conversion information. For example, as shown in FIG. 3, when the measurement phase φx is a value between the sample phases φC and φD, it is determined that the measurement phase φx corresponds to the section CD. In response to this, the conversion information corresponding to the section CD, that is, the slope Scd and the intercept Icd related to the equation (3) are read out from the conversion information stored in the storage unit 16. And the calculating part 15 acquires height Hx corresponding to the said measurement phase (phi) x by substituting measurement phase (phi) x to the formula identified from the read conversion information. That is, in the case of FIG. 3, the calculation unit 15 substitutes the measurement phase φx into the above equation (3) obtained from the slope Scd and the intercept Icd, thereby obtaining the height Hx (from the reference plane) corresponding to the measurement phase φx. Is calculated). As described above, the calculation unit 15 searches for a section for the measurement phase φx of each pixel, and calculates the height Hx based on the conversion information of the corresponding section.

  As described above, the three-dimensional shape of the measurement object 2 is grasped based on the height Hx of each pixel obtained from the captured image of the projection pattern for the measurement object 2. According to the three-dimensional measuring apparatus 1 and the three-dimensional measuring method according to the present invention, the height from the phase is calculated by an approximate expression corresponding to a plurality of sections, as compared with the conventional configuration in which the height is calculated by one approximate expression. As a result, errors due to the influence of optical characteristics can be reduced. Thereby, it is possible to measure a three-dimensional shape with higher accuracy. In the present embodiment, an approximate expression (primary expression) is obtained based on the respective sample phases and heights with respect to the reference plane at two measurement points that define the same section. ) Can be obtained.

  In the first embodiment, the example in which the approximate expression (conversion information) of each section is obtained from two measurement points has been described, but the present invention is not limited to this. As shown in FIG. 5, it is also possible to set a plurality of section measurement points in each section and calculate an approximate expression (relational expression) by least square approximation from the sample phase and height at each section measurement point. is there. For example, with the measurement point C as the reference (0), a section AB defined by the measurement point A (−1 mm) and the measurement point B (−0.5 mm) is further reduced by −0.9 mm (height) at intervals of 0.1 mm. ha), -0.8 mm (height hb), -0.7 mm (height hc), and -0.6 mm (height hd) are set for each section measurement point, and the sample phase is set at each of the section measurement points. φa to φd are calculated, and an approximate expression (relational expression) can be calculated from the total of six sample phases and the height of each measurement point by least square approximation. According to this configuration, the error can be further reduced, so that a three-dimensional shape can be measured with higher accuracy.

In addition, this invention is not limited to above-described embodiment, A various deformation | transformation is possible based on description of a claim.
For example, the set number of measurement points and the set number of section measurement points can be arbitrarily changed according to the size of the measurement object and the required measurement accuracy.
Moreover, in the said embodiment, although the structure which raises / lowers the mounting surface 13 and the measurement target object 2 with respect to the measuring instrument group 5 with the Z stage 3 was illustrated, it is not restricted to this, In short, the measuring instrument group 5 and Any configuration may be employed as long as the placement surface 13 and the measurement target 2 are relatively moved (adjacent or separated). For this reason, it can be said that the measurement surface and the reference surface described above are surfaces determined according to the relative position (distance) between the mounting surface 13 and the measurement object 2 and the measuring instrument group 5.

  DESCRIPTION OF SYMBOLS 1 ... Three-dimensional measuring device, 2 ... Measurement object, 3 ... Z stage, 5 ... Measuring machine group, 6 ... Computer, 7 ... Display apparatus, 9 ... Photographing 10 ... projector 11 ... height measuring machine 12 ... mounting plate 15 ... calculation unit 16 ... storage unit

Claims (4)

A three-dimensional measuring device for measuring the shape of a measurement object,
A projector that projects pattern light toward a placement surface on which the measurement object is placed;
A photographing machine for photographing the reflected light from the mounting surface side,
The conversion information relating to the relational expression between the phase of each pixel of the image captured by the camera and the height with respect to the reference surface set between the camera and the placement surface in the direction intersecting the reference surface. A storage device stored corresponding to each of a plurality of sections;
Based on the measurement phase obtained from the captured image of the measurement object onto which the pattern light is projected and the conversion information of the section corresponding to the measurement phase, the height of the measurement object with respect to the reference plane is calculated. A computing device to calculate,
A three-dimensional measuring apparatus comprising:   The conversion information is information related to an approximate expression obtained for each section based on sample phases and heights with respect to the reference plane at a plurality of measurement points that respectively define ends of the plurality of sections. Item 3. The three-dimensional measurement apparatus according to item 1.   The conversion information includes the respective sample phases of the measurement points that define the same section and the height with respect to the reference plane, and the sample phase at the section measurement points set between these measurement points and the height with respect to the reference plane. The three-dimensional measuring apparatus according to claim 2, wherein the information is related to an approximate expression obtained by least square approximation based on. The measurement in a three-dimensional measurement apparatus comprising: a projector that projects pattern light toward a placement surface on which a measurement object is placed; and a photographing device that photographs reflected light from the placement surface. A three-dimensional measurement method for measuring the shape of an object,
A direction that intersects the reference plane with conversion information relating to a relational expression between a phase for each pixel of an image captured by the camera and a height relative to a reference plane set between the camera and the mounting surface. Conversion information acquisition step to acquire for each of the plurality of sections,
Based on the measurement phase obtained from the captured image of the measurement object onto which the pattern light is projected and the conversion information of the section corresponding to the measurement phase, the height of the measurement object with respect to the reference plane is calculated. A height calculating step to calculate,
A three-dimensional measurement method comprising:

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