JP2011002240A - Three-dimensional shape measurement method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a three-dimensional shape measurement method and a device reducing the unmeasurable area of the surface of a measurement object, by reducing the noise components of reflected light due to the reflection characteristics of the surface of the measurement object, including halation.SOLUTION: The three-dimensional shape measuring device 100 includes a projector 2 projecting pattern light 12b to the measurement object 1; a CCD camera 3 imaging the measurement object 1, on which the pattern light 12b is projected and obtaining a reflected light image from the surface of the measurement object 1; a calculation section 4 calculating the three-dimensional shape of the measurement object 1 from the reflected light image; a polarizing filter 9 disposed between the measurement object 1 and the CCD camera 3; and a polarizing filter 7 disposed between the projector 2 and the measurement object 1. In the polarizing filters 7, 9, the direction of transmission axis is adjustably set.

Description

  The present invention relates to a three-dimensional shape measuring method and apparatus. For example, projecting pattern light for shape measurement onto the object to be measured, obtaining a reflected light image by reflected light from the surface of the object to be measured, and calculating a three-dimensional shape of the object to be measured from the reflected light image The present invention relates to an original shape measuring method and apparatus.

Conventionally, in the three-dimensional shape measuring method and apparatus, pattern light for shape measurement is projected onto the object to be measured, and a reflected light image by reflected light from the surface of the object to be measured on which this pattern light is projected is obtained. It is known to calculate a three-dimensional shape from this reflected light image based on the principle of triangulation.
As such a three-dimensional shape measurement method and apparatus, for example, Patent Document 1 discloses that a plurality of binary projection patterns, which are stripe-shaped light patterns, are projected as pattern light for shape measurement. When one point on the object to be measured is projected, the light beam projected onto the point being observed blinks to form a code, and the code is used. A three-dimensional shape measuring method and apparatus based on a so-called spatial coding method for measuring the three-dimensional shape of an object to be measured is described.
In such a spatial coding method, the value indicated by the code and the direction of the light beam have a one-to-one relationship, and the direction of the line of sight of the observation position can be determined from the position of the light spot on the object to be measured. Since the direction of the light beam can be determined from the value indicated by the code, the distance to all the light spots on the object to be measured can be obtained by the principle of triangulation, thereby measuring the three-dimensional shape of the object to be measured in a non-contact manner. can do.
Japanese Patent Application Laid-Open No. H10-228707 describes a color having a large difference in luminance value on the surface of the object to be measured by capturing reflected light images based on a binarized projection pattern with a plurality of exposure time patterns and synthesizing those images. 3D shape measuring method and apparatus capable of obtaining the brightness difference of the slit pattern over the entire image area, and obtaining a stable measurement result that does not depend on the brightness difference of the surface color of the object to be measured. Is also described.

JP 2007-315864 A

However, the conventional three-dimensional shape measuring method and apparatus as described above have the following problems.
With the technique described in Patent Document 1, although stable measurement can be performed even if there is a luminance difference in the surface color of the object to be measured, the influence of halation that occurs when a glossy surface exists on the surface cannot be removed. For this reason, in the reflected light image on the glossy surface of the object to be measured, there is a problem that pattern light having a sufficient luminance difference cannot be acquired, and as a result, the three-dimensional shape of the glossy surface cannot be measured.
For example, in the photograph of the doll of the object to be measured shown in FIG. 2 of Patent Document 1, a high-luminance portion estimated to be halation due to the influence of the glossy surface is found near the forehead (forehead). The three-dimensional shape is not restored in the measurement result of the corresponding portion shown in FIG.

  The present invention has been made in view of the above problems. For example, the noise component of the reflected light due to the reflection characteristics of the surface of the object to be measured such as halation is reduced, and the non-measurable range of the surface of the object to be measured is determined. An object of the present invention is to provide a three-dimensional shape measuring method and apparatus capable of reducing the above.

In order to solve the above-described problems, the three-dimensional shape measurement method of the present invention projects a pattern light for shape measurement onto an object to be measured, and obtains a reflected light image by reflected light from the surface of the object to be measured. A three-dimensional shape measurement method for calculating a three-dimensional shape of the object to be measured from the reflected light image, wherein at least one of the pattern light for shape measurement and the reflected light from the surface of the object to be measured The reflected light image is acquired after passing through the polarizing optical element.
According to the present invention, since the reflected light image is acquired after passing at least one of the pattern light for shape measurement and the reflected light from the surface of the measured object through the polarizing optical element, the measured object in the reflected light image is obtained. The amount of the reflected light of the component polarized by the reflection on the surface can be regulated by the polarization direction. For this reason, for example, the reflected light polarized by being reflected by the glossy surface of the object to be measured can be removed or reduced from the reflected light of the object to be measured, and noise components such as so-called halation can be removed or reduced. it can.

In the three-dimensional shape measurement method of the present invention, polarized light is used as the pattern measurement pattern light, and the direction of the transmission axis of the polarization optical element is reflected by the surface of the object to be measured and polarized reflected light. It is preferable to obtain the reflected light image after adjusting so as to intersect the direction of the polarization axis having the largest light quantity component.
In this case, the direction of the transmission axis of the polarizing optical element is adjusted so that the direction of the polarization axis having the largest light quantity component of the reflected light reflected by the surface of the object to be measured and thereby polarized is intersected. The reflected light can be reduced, and a reflected light image in which the influence of the noise component is reduced can be acquired.

In the three-dimensional shape measuring method for adjusting the direction of the transmission axis of the polarizing optical element of the present invention, the direction of the transmission axis of the polarizing optical element and the polarization axis of the reflected light reflected by the surface of the object to be measured The angle at which the direction intersects is preferably adjusted to 90 °.
In this case, the direction of the transmission axis of the polarizing optical element is adjusted so that it intersects with the direction of the polarization axis having the largest light quantity component of the reflected light reflected by the surface of the object to be measured and thereby 90 °. The reflected light image in which the polarized reflected light is removed and the influence of the noise component is minimized can be acquired.

The three-dimensional shape measurement apparatus of the present invention images a measurement object on which the shape measurement pattern light is projected by the projection unit that projects shape measurement pattern light onto the measurement object, An imaging unit that acquires a reflected light image by reflected light from the surface of the object to be measured, an arithmetic unit that calculates a three-dimensional shape of the object to be measured from the reflected light image acquired by the imaging unit, and the measured object A polarizing optical element that is disposed between the object and the imaging unit and regulates the transmittance of the reflected light from the surface of the object to be measured according to the polarization direction, and the polarizing optical element is in the direction of the transmission axis Is configured to be adjustable.
According to this invention, the projection unit projects the pattern light for shape measurement onto the object to be measured, and adjusts the direction of the transmission axis of the first polarizing optical element with the reflected light from the surface of the object to be measured. Can be transmitted according to the polarization direction. For this reason, the reflected light image can be acquired by the imaging unit in a state in which the luminance of the reflected light reflected and polarized by the surface of the object to be measured is adjusted. And the three-dimensional shape of a to-be-measured object can be calculated from the reflected light image acquired by the imaging part by the calculating part.

In the three-dimensional shape measuring apparatus of the present invention, it is preferable that the polarizing optical element has an antireflection structure on the surface.
In this case, since the antireflection structure is provided on the surface of the polarizing optical element, it is possible to reduce the light reflected by the surface of the polarizing optical element and returning to the object to be measured. For this reason, light which becomes noise on the surface of the object to be measured can be reduced.

Another three-dimensional shape measuring apparatus of the present invention is configured to project a measurement unit that projects pattern light for shape measurement onto a measurement target, and the measurement target on which the pattern light for shape measurement is projected by the projection unit. An imaging unit that acquires a reflected light image by reflected light from the surface of the object to be measured; an arithmetic unit that calculates a three-dimensional shape of the object to be measured from the reflected light image acquired by the imaging unit; A first polarizing optical element that is disposed between the object to be measured and the imaging unit and regulates the transmittance of reflected light from the surface of the object to be measured according to the polarization direction, the projection unit, and the object to be measured A second polarizing optical element that is disposed between the first polarizing optical element and the second polarizing optical element that regulates a transmittance of projection light projected onto the object to be measured according to a polarization direction, and the first polarizing optical element and the second polarizing optical element. At least one of the polarizing optical elements can adjust the direction of the transmission axis Configuration to that provided in the.
According to this invention, when the pattern measuring pattern light is projected onto the object to be measured by the projection unit, the pattern light is polarized by the second polarizing optical element and then projected onto the object to be measured. The reflected light from the surface of the object to be measured can be transmitted according to the polarization direction by adjusting the direction of the transmission axis of the first polarizing optical element. For this reason, a reflected light image can be acquired by an imaging part in the state which adjusted the brightness | luminance of the reflected light polarized by being reflected by the surface of a to-be-measured object. And the three-dimensional shape of a to-be-measured object can be calculated from the reflected light image acquired by the imaging part by the calculating part.

In another three-dimensional shape measuring apparatus of the present invention, it is preferable that the first and second polarizing optical elements have an antireflection structure on the surface.
In this case, since the antireflection structure is provided on the surfaces of the first and second polarizing optical elements, light that is reflected by the surfaces of the first and second polarizing optical elements and returns to the object to be measured is reduced. Can do. For this reason, light which becomes noise on the surface of the object to be measured can be reduced.

  According to the three-dimensional shape measuring method and apparatus of the present invention, it is possible to obtain a reflected light image in which the influence of reflected light polarized by reflection on the surface of the object to be measured is reduced. There is an effect that the noise component of the reflected light due to the reflection characteristics of the surface can be reduced, and the unmeasurable area of the surface of the object to be measured can be reduced.

It is a typical block diagram which shows schematic structure of the three-dimensional shape measuring apparatus which concerns on the 1st Embodiment of this invention. It is the front view of the polarization optical element and transmission axis adjustment mechanism of the three-dimensional shape measuring apparatus which concern on the 1st Embodiment of this invention, and its AA sectional drawing. It is a photograph which shows an example of a to-be-measured object. It is a schematic diagram explaining the measurement principle of the three-dimensional shape measuring method which concerns on the 1st Embodiment of this invention. The enlarged photograph which shows an example of the to-be-measured object irradiated with the pattern light for shape measurement by the three-dimensional shape measuring apparatus which concerns on the 1st Embodiment of this invention, and the calculation result of the three-dimensional shape of this to-be-measured object are shown. It is an image. It is an enlarged photograph which shows an example of the to-be-measured object irradiated with the pattern light for shape measurement by the three-dimensional shape measuring apparatus of a comparative example, and an image which shows the calculation result of the three-dimensional shape of this to-be-measured object. It is a schematic diagram which shows the reflected light image which can measure a three-dimensional shape, and a schematic diagram which shows the reflected light image which cannot measure a three-dimensional shape. It is a photograph which shows the other example of the to-be-measured object irradiated with the pattern light for shape measurement by the three-dimensional shape measuring apparatus which concerns on the 1st Embodiment of this invention, and the apparatus of a comparative example. It is a typical block diagram which shows schematic structure of the three-dimensional shape measuring apparatus which concerns on the 2nd Embodiment of this invention. It is a schematic diagram explaining the measurement principle of the three-dimensional shape measuring method which concerns on the 2nd Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In all the drawings, even if the embodiments are different, the same or corresponding members are denoted by the same reference numerals, and common description is omitted.

[First Embodiment]
A three-dimensional shape measuring apparatus according to a first embodiment of the present invention will be described.
FIG. 1 is a schematic configuration diagram showing a schematic configuration of the three-dimensional shape measuring apparatus according to the first embodiment of the present invention. FIG. 2A is a front view of the polarizing optical element and the transmission axis adjusting mechanism of the three-dimensional shape measuring apparatus according to the first embodiment of the present invention. FIG.2 (b) is AA sectional drawing in Fig.2 (a).

The three-dimensional shape measuring apparatus 100 according to the present embodiment projects pattern light for shape measurement onto a measured object, acquires a reflected light image by reflected light from the measured object, and measures the measured object from the reflected light image. As shown in FIG. 1, the three-dimensional shape is arranged above the table 5 that holds the DUT 1.
As the DUT 1, an appropriate member having a three-dimensional shape composed of a combination of various uneven shapes can be employed. The surface 1a of the DUT 1 may be a scattering surface or a glossy surface.
For example, it is possible to measure a three-dimensional shape by adopting an injection molded resin part as the DUT 1. In this case, the three-dimensional shape of the resin part can be compared with the three-dimensional CAD data used for the design and the like to inspect for molding defects. Since molds for resin parts are often mirror-finished, the surface of many resin parts is glossy. In addition, for example, a resin part used for an exterior such as a cover may be colored by coating or the like on the surface or the surface gloss may be increased.

The schematic configuration of the three-dimensional shape measuring apparatus 100 includes a projector 2 (projection unit) that projects pattern light for shape measurement onto an object to be measured 1 held on a table 5, and pattern light for shape measurement by the projector 2. A CCD camera 3 (imaging unit) that captures an image of the projected measurement object 1 and acquires a reflected light image by reflected light from the measurement object 1, and controls the operations of the projector 2 and the CCD camera 3 and the CCD camera 3 And an arithmetic unit 4 that calculates the three-dimensional shape of the DUT 1 from the reflected light image captured in (1).
A monitor 15 is electrically connected to the CCD camera 3 and the calculation unit 4 so that images captured by the CCD camera 3 and calculation results of the calculation unit 4 can be displayed.
The optical axis of the projection light of the projector 2 and the imaging optical axis of the CCD camera 3 are crossed obliquely at a certain angle.

Between the DUT 1 and the CCD camera 3, a polarizing filter 9 (first polarizing optical element) that restricts the transmittance of reflected light from the DUT 1 according to the polarization direction is disposed.
As shown in FIGS. 2A and 2B, the polarizing filter 9 of the present embodiment has a disk shape, and an antireflection film 9a is provided on the surface of the DUT 1 as an antireflection structure. ing.
The outer peripheral part of the polarizing filter 9 is fitted and fixed to one end side of the substantially annular polarizing filter holder 8. The other end side of the polarizing filter holder 8 is frictionally fitted to a cylindrical rotation holding portion 11 provided coaxially with the optical axis of the CCD camera 3 so that it can rotate and stop at a rotation position.
Accordingly, for example, the polarizing filter holder 8 can be rotated with respect to the rotation holding unit 11 by rotating the outer peripheral side of the polarizing filter holder 8 by hand, and the rotation can be stopped at an appropriate position. As a result, the transmission axis 9 b of the polarizing filter 9 fixed to the polarizing filter holder 8 is rotated around the optical axis of the CCD camera 3 and the angle of the reflected light from the DUT 1 incident on the polarizing filter 9 with respect to the polarizing axis. Can be adjusted.
That is, in this embodiment, the polarizing filter holder 8 and the rotation holding unit 11 are the first transmission axis that adjusts the direction of the transmission axis 9 b of the polarizing filter 9 with respect to the polarization axis of the reflected light from the DUT 1. An adjustment mechanism is configured.

In addition, a polarizing filter 7 (second polarization optical element) that regulates the transmittance of the projection light projected from the projector 2 to the measured object 1 according to the polarization direction between the projector 2 and the measured object 1. Is arranged.
As shown in FIGS. 2A and 2B, the polarizing filter 7 of the present embodiment has a disk shape, and an antireflection film 7a is provided on the surface of the DUT 1 as an antireflection structure. ing.
The outer peripheral portion of the polarizing filter 7 is fitted and fixed to one end side of the substantially annular polarizing filter holder 6. The other end side of the polarizing filter holder 6 is friction-fitted to the cylindrical rotation holding unit 10 provided coaxially with the optical axis of the projector 2 so as to be able to rotate and stop at the rotation position.
Thereby, for example, the polarizing filter holder 6 can be rotated with respect to the rotation holding unit 10 by rotating the outer peripheral side of the polarizing filter holder 6 by hand, and the rotation can be stopped at an appropriate position. As a result, the transmission axis 7b of the polarization filter 7 fixed to the polarization filter holder 6 is rotated around the optical axis of the projector 2, and the polarization direction of the projection light from the projector 2 incident on the polarization filter 7 is changed to the transmission axis 7b. The direction of the polarization axis of the projection light can be adjusted by polarizing in the direction along the direction.
That is, in the present embodiment, the polarizing filter holder 6 and the rotation holding unit 10 constitute a second transmission axis adjusting mechanism that adjusts the direction of the transmission axis 7 b of the polarizing filter 7.

  The operation control performed by the calculation unit 4 includes the control of the pattern shape of the pattern light for shape measurement projected from the projector 2 and the reflected light image captured by the CCD camera 3 in synchronization with the timing of switching the pattern light. For example, control for acquiring image data can be given.

For example, when the projector 2 includes a spatial modulation element such as a liquid crystal display element, and the spatial light is spatially modulated by the spatial modulation element to form a plurality of shape measurement pattern lights, a plurality of modulation data for the spatial modulation element is used. Are sequentially transmitted to the projector 2.
As an example of the pattern light pattern for shape measurement, when the spatial coding method is used, the fringe pitch is switched so that the image area of the DUT 1 can be divided and a spatial code can be given to each image area. A checkered pattern group can be employed.
Although not used for shape measurement, by setting modulation data for invalidating modulation in the projector 2, uniform illumination pattern light having no spatial luminance difference is generated to illuminate the DUT 1. be able to.

Further, as the calculation performed by the calculation unit 4, a calculation for calculating the three-dimensional shape of the DUT 1 using a known technique such as a spatial encoding method, a phase shift method, a moire method, and the calculation result are monitored 15. For example, an operation for generating image data to be displayed in 3D can be used.
As the calculation for calculating the three-dimensional shape by the spatial coding method, a known appropriate calculation can be employed. For example, the calculation etc. which were indicated by JP, 2007-315864, A can be adopted.
In this embodiment, the arithmetic unit 4 is configured by a computer including a CPU, a memory, an input / output interface, an external storage device, and the like. The above control operations and calculations are realized by executing appropriate control programs and calculation programs by this computer.

Next, the operation of the three-dimensional shape measuring apparatus 100 will be described together with the three-dimensional shape measuring method of this embodiment.
FIG. 3 is a photograph showing an example of an object to be measured. FIG. 4 is a schematic diagram illustrating the measurement principle of the three-dimensional shape measurement method according to the first embodiment of the present invention. Fig.5 (a) is an enlarged photograph which shows an example of the to-be-measured object irradiated with the pattern light for shape measurement by the three-dimensional shape measuring apparatus which concerns on the 1st Embodiment of this invention. FIG. 5B is an image showing the calculation result of the three-dimensional shape of the object to be measured shown in FIG. Fig.6 (a) is an enlarged photograph which shows an example of the to-be-measured object irradiated with the pattern light for shape measurement by the three-dimensional shape measuring apparatus of a comparative example. FIG. 6B is an image showing the calculation result of the three-dimensional shape of the object to be measured shown in FIG. FIG. 7A is a schematic diagram showing a reflected light image capable of measuring a three-dimensional shape. FIG. 7B is a schematic diagram illustrating a reflected light image in which the three-dimensional shape measurement cannot be performed. FIG. 8A is a photograph showing another example of the measurement object irradiated with the pattern light for shape measurement by the three-dimensional shape measurement apparatus according to the first embodiment of the present invention. FIG. 8B is a photograph showing another example of the measurement object irradiated with the pattern light for shape measurement by the three-dimensional shape measurement apparatus of the comparative example.

In order to measure the three-dimensional shape of the DUT 1 by the three-dimensional shape measuring apparatus 100, first, the DUT 1 is placed on the table 5 as shown in FIG.
Next, the position of the polarizing filter 9 in the direction of the transmission axis 9b is adjusted.
For this reason, pattern light 12b whose modulation is invalidated is emitted from the projector 2, and this is used as illumination to be photographed by the CCD camera 3. That is, in the projector 2, as shown in FIG. 4, based on the modulation data that invalidates the modulation from the calculation unit 4, the light projected from the light source is substantially uniformly illuminated without being modulated by the spatial modulation element. The pattern light 12 a is projected toward the DUT 1 on the table 5.
Here, since FIG. 4 is a schematic diagram, the illustration is simplified and the surface 1a is enlarged and drawn in a planar shape.

The pattern light 12 a passes through the polarizing filter 7 and is projected onto the DUT 1 as pattern light 12 b that is polarized in a direction along the transmission axis 7 b of the polarizing filter 7.
The pattern light 12b is polarized because it is scattered and reflected radially in various directions according to the reflection characteristics of the surface 1a of the object 1 to be measured and reflected as a whole by non-polarized scattered reflected light 13a and Fresnel's law. The polarized reflected light 14 is mixed. The greater the glossiness of the surface 1a, the greater the proportion of polarized reflected light 14.
The scattered reflected light 13 a and the polarized reflected light 14 pass through the polarizing filter 9, and polarized light in a direction along the transmission axis 9 b of the polarizing filter 9 enters the CCD camera 3. The light incident on the CCD camera 3 is photoelectrically converted by the imaging device of the CCD camera 3 and displayed on the monitor 15 as a reflected light image by the reflected light from the DUT 1.

As an example, in FIG. 3, a member whose surface is glossy painted after being molded with resin is assembled, and a mouse having a three-dimensional shape that forms a convex surface as a whole is placed as the DUT 1 and modulated from the projector 2. An image photographed by the CCD camera 3 using the pattern light 12b in which is invalidated as illumination is shown.
Since most of the surface of the DUT 1 is a glossy surface, for example, as can be seen remarkably in part B of FIG. Such reflected light noise is called halation.
Note that the plurality of white circle images on the DUT 1 are provided for experiments for purposes different from the three-dimensional shape measurement, and have nothing to do with the product shape of the mouse or the following three-dimensional shape measurement.

Here, when the polarizing filter holder 8 is rotated, the transmission axis 9b is rotated, and the reflected light image displayed on the monitor 15 changes according to the polarization direction of the reflected light. Since the scattered reflected light 13a is non-polarized light, the reflected light image by the scattered reflected light 13b transmitted through the polarizing filter 9 does not change even if the transmission axis 9b rotates, but the polarized reflected light 14 is polarized. The transmittance with respect to the polarizing filter 9 varies depending on the direction of the transmission axis 9b.
Therefore, the measurer rotates the polarizing filter holder 8 while looking at the image displayed on the monitor 15 to check the change in the size of the halation area, and at the position where the halation area becomes the minimum, the measuring apparatus. Stop rotating.
In particular, when the direction of the transmission axis 9b intersects the direction of the polarization axis of the polarized reflected light 14 at 90 °, that is, in a crossed Nicol state, the transmittance of the polarized reflected light 14 becomes approximately 0%, and the polarized light reflected. This is preferable because the influence of the light 14 can be almost completely removed.
When the direction of the polarization axis of the polarized reflected light 14 is known in advance, the rotation amount of the polarization filter holder 8 is measured without performing the above adjustment, and the polarization axis of the polarized reflected light 14 and the transmission axis 9b are determined. It only has to match the direction that intersects at 90 degrees.

In this state, once the object to be measured 1 and the table 5 are removed and the positions of the polarization filter holders 6 and 8 are fixed, a known calibration is performed in the same manner as in the conventional three-dimensional shape measuring apparatus.
Thereafter, the table 5 is installed again, and the DUT 1 is fixed on the table 5.

Next, the calculation unit 4 sends modulation data for forming a fixed shape measuring pattern light to the projector 2 by the projector 2. In this embodiment, modulation data of a checkered pattern in which a straight line and a space are repeated in a fixed direction with a pitch w and a width w / 2 is transmitted.
In the projector 2, the light projected from the light source is modulated by the spatial modulation element based on the modulation data from the calculation unit 4, and as shown in FIG. Pattern light 12a is projected.
The pattern light 12 a passes through the polarizing filter 7 and is projected onto the DUT 1 as a pattern light 12 b having a checkered pattern that is polarized in the direction along the transmission axis 7 b of the polarizing filter 7.

  The pattern light 12 b is divided into scattered reflected light 13 a and polarized reflected light 14, passes through the polarizing filter 9, and polarized light in the direction along the transmission axis 9 b of the polarizing filter 9 enters the CCD camera 3. The light incident on the CCD camera 3 is photoelectrically converted by the image pickup device of the CCD camera 3 and displayed on the monitor 15 as a reflected light image by the reflected light from the DUT 1 and sent to the calculation unit 4 for calculation processing. Is done.

  In the present embodiment, since the antireflection films 7a and 9a are provided on the surfaces of the polarizing filters 7 and 9 on the measured object 1 side, respectively, the scattered reflected light 13a and the polarized reflected light 14 from the surface 1a are provided. The reflectance of the surfaces of the polarizing filters 7 and 9 is sufficiently low. For this reason, the noise light component generated when the light reflected from the surfaces of the polarizing filters 7 and 9 toward the DUT 1 is re-reflected by the surface 1a is extremely small.

For example, the image shown in FIG. 5A is obtained when the direction of the transmission axis 9b is adjusted to a direction intersecting with the direction of the polarization axis of the polarized reflected light 90 at 90 ° so that the halation is minimized. 2 is a reflected light image of the DUT 1. However, for the sake of easy viewing, a photograph taken from a viewpoint slightly shifted from the viewpoint shown in FIG.
As described above, in the portion C of FIG. 5A, there is almost no halation, and an image of a checkered pattern having a good luminance difference is observed.

The calculation unit 4 calculates the three-dimensional shape of the DUT 1 using the reflected light image acquired in this way, and displays the calculation result on the monitor 15.
In the spatial coding method, the reflected light image is stored in the calculation unit 4 and the brightness of each image area is recorded as, for example, 0, 1 or the like. Then, pattern light 12b is generated by sequentially subdividing the lattice fringe pitch w of the pattern light for shape measurement into w / 2, w / 4,..., And the above operation is repeated for each image region. A space code consisting of a sequence of 0 and 1 is calculated.
And the deformation | transformation of a lattice fringe is detected by investigating the coordinate of the pixel to which the same space code was provided. This amount of deformation is converted into position coordinates in a three-dimensional space using the principle of triangulation from the relative positional relationship between the projector 2 and the CCD camera 3.

In this way, the calculated three-dimensional shape of the DUT 1 is compared with design data such as three-dimensional CAD data, and can be used for shape inspection or the like.
The calculation unit 4 displays the three-dimensional shape on the monitor 15 using a 3D display technique such as a polygon.
FIG. 5B is an example of the three-dimensional shape of the DUT 1 measured by the three-dimensional shape measuring apparatus 100. In the drawing, a three-dimensional shape in which a light gray curved surface is calculated is shown. The same portion as the background color is a portion where a three-dimensional shape is not calculated because a reflected light image having a luminance difference due to pattern light is not acquired. In this example, it can be seen that such non-computable places have many dark parts such as grooves.
On the other hand, in a portion corresponding to a location where strong halation is generated as shown in B portion of FIG. 3 (see D portion of FIG. 5B), a good measurement result is obtained even if there is strong halation. I understand that.

In order to evaluate the effect of the present embodiment, as a comparative example, three-dimensional shape measurement was performed in the same manner as described above, using a device in which the polarizing filters 7 and 9 were removed from the three-dimensional shape measurement device 100.
FIGS. 6A and 6B show the reflected light image by the reflected light of the DUT 1 corresponding to FIGS. 5A and 5B and the three-dimensional shape measurement result, respectively.
As shown in FIG. 6B, the three-dimensional shape measurement result of the comparative example shows that the gray portion is markedly smaller than that in FIG. 5B, and the portion where the three-dimensional shape is accurately measured is entirely. It is running low. This is related to the fact that almost the entire DUT 1 is a glossy surface.
For example, when comparing the portion C corresponding to the portion B of FIG. 3 where the halation is noticeable due to the influence of the glossy surface, the portion C of FIG. An image is observed. On the other hand, in the part C of FIG. 6A, a high-luminance part is formed by halation, and the image has a checkered pattern.

  When this difference is schematically represented, in the portion C of FIG. 5A, as shown in FIG. 7A, the line image L1 which is a bright portion having a uniform width w / 2 is obtained almost only by the scattered reflected light 13b. , L2, L3, and L4, space images S1, S2, S3, and S4, which are dark portions of equal width w / 2, are formed. On the other hand, in the part C of FIG. 6A, as shown in FIG. 7B, the polarized reflected light 14 is superimposed on a part of the line images L1, L2, L3, and L4 and the line width is increased. As a result, The space images S1 and S4 are thin, and the space images S2 and S3 are cut off.

For example, when considering the point P on the reflected light image in FIGS. 7A and 7B, the point P in FIG. 7A is a dark part at the time of spatial coding. Since the point P in (b) is a bright part, for example, 1 is given. Next, when the pitch of the checkered pattern is subdivided, in FIG. 7A, light and dark are regularly changed, and an arbitrary point is spatially coded.
On the other hand, in FIG. 7B, the point near the point P remains a bright part even if the pitch of the lattice fringes is subdivided, so that a correct spatial code cannot be given. For this reason, in the reflected light image of the comparative example, it is difficult to measure the three-dimensional shape at a portion where the halation is remarkable, such as in the vicinity of the point P.

In FIGS. 5A and 6A, since the pasted image appears to be crushed due to insufficient gradation, other examples in which a clearer difference can be observed are shown in FIGS. 8A and 8B. Show. This object to be measured is an exterior body of a telephone receiver.
In FIG. 8A, which is a reflected light image by the three-dimensional shape measuring apparatus 100 of the present embodiment, an image of a checkerboard pattern having a luminance difference is acquired over the whole, but acquired by the apparatus of the comparative example. In the reflected light image shown in FIG. 8B, an image of a checkered pattern having a good luminance difference is not obtained due to remarkable halation as in the E portion.

  As described above, in the three-dimensional shape measuring apparatus 100, the polarization filter 7 is used to polarize the pattern light 12 b for shape measurement, and the direction of the transmission axis 9 b of the polarization filter 9 is reflected by the object 1 to be polarized. The brightness of the polarized reflected light 14 can be reduced by obtaining the reflected light image after adjusting so as to intersect the direction of the polarization axis of the polarized reflected light 14, so that noise components such as halation can be reduced. A reflected light image with reduced influence can be acquired. Thereby, since the reflected light image is acquired as an image having a good luminance difference, it is possible to reduce the non-measurable area even if the surface 1a of the DUT 1 is a glossy surface.

[Second Embodiment]
Next, a three-dimensional shape measuring apparatus according to the second embodiment of the present invention will be described.
FIG. 9 is a schematic configuration diagram showing a schematic configuration of a three-dimensional shape measuring apparatus according to the second embodiment of the present invention. FIG. 10 is a schematic diagram for explaining the measurement principle of the three-dimensional shape measurement method according to the second embodiment of the present invention.

In the three-dimensional shape measuring apparatus 200 of the present embodiment, as shown in FIG. 9, the device under test 21 is a polyhedron as a whole, such as a notebook computer exterior body, and the three-dimensional shape is made into a plurality of substantially planar shapes. This is particularly suitable when the measurement can be performed separately in the measurement region.
The configuration of the three-dimensional shape measuring apparatus 200 is obtained by deleting the polarizing filter 7 and the polarizing filter holder 6 of the three-dimensional shape measuring apparatus 100 of the first embodiment. Hereinafter, a description will be given centering on differences from the first embodiment.

In order to perform the three-dimensional shape measurement of the object to be measured 21 by the three-dimensional shape measuring apparatus 200, first, the object to be measured 21 is arranged on the table 5 as shown in FIG. At this time, the projector 2 and the CCD camera 3 are arranged toward one of the planar measurement areas of the object to be measured 21.
Next, the position of the polarizing filter 9 (polarizing optical element) in the direction of the transmission axis 9b is adjusted.
For this reason, the pattern light 12a in which the modulation is invalidated is emitted from the projector 2, and the CCD camera 3 takes an image of this as illumination. That is, in the projector 2, as shown in FIG. 10, the pattern light 12 a that is substantially uniform illumination based on the modulation data that invalidates the modulation from the calculation unit 4 is directed toward the object 21 to be measured on the table 5. Project.

The pattern light 12a is polarized because it is scattered and reflected radially in various directions according to the reflection characteristics of the surface 21a of the object to be measured 21 and reflected as a whole by non-polarized scattered reflected light 13a and Fresnel's law. The polarized reflected light 24a is mixed. The greater the glossiness of the surface 21a, the greater the proportion of the polarized reflected light 24a.
Even when the pattern light 12a is not polarized, the polarized polarized reflected light 24a is generated by the p-polarized light in the plane including the normal vector of the pattern light 12a and the surface 21a in the Fresnel reflection of the glossy surface. This is because the reflectance differs between s-polarized light that vibrates in a plane perpendicular to p-polarized light.
The scattered reflected light 13a and the polarized reflected light 24a are transmitted through the polarizing filter 9, and the scattered reflected light 13b and the polarized reflected light 24b, which are polarized components in the direction along the transmission axis 9b of the polarizing filter 9, are converted into the CCD camera 3. Is incident on. The light incident on the CCD camera 3 is photoelectrically converted by the imaging device of the CCD camera 3 and displayed on the monitor 15 as a reflected light image by the reflected light from the DUT 1.

Here, as in the first embodiment, when the polarizing filter holder 8 is rotated, the transmission axis 9b rotates, and the reflected light image displayed on the monitor 15 changes according to the polarization direction of the reflected light. . Since the scattered reflected light 13a is non-polarized light, the reflected light image by the scattered reflected light 13b does not change even if the transmission axis 9b rotates. However, since the polarized reflected light 24a is polarized, it depends on the direction of the transmission axis 9b. The transmittance with respect to the polarizing filter 9 changes, and the light quantity of the polarized reflected light 24b changes.
Therefore, the measurer rotates the polarizing filter holder 8 while viewing the image displayed on the monitor 15 to check the change in the size of the halation region, and the position where the halation region is minimized (the polarization reflected light 24b). The rotation of the polarizing filter holder 8 is stopped at the position where the light quantity is minimized.
Here, the light quantity of the polarized reflected light 24b can be minimized by adjusting the transmission axis 9b of the polarizing filter 9 intersecting with the polarization axis of the polarized light included in the polarized reflected light 24a in a large amount at 90 °.
In the case of a substantially flat surface like the surface 21a, the ratio of the polarization component of the polarized reflected light 24a is determined by the reflection characteristics of the surface 21a and the incident angle of the pattern light 12a. Therefore, when the polarization axis of the polarization component that is most contained in the polarized reflected light 24a determined from these is known in advance, the amount of rotation of the polarizing filter holder 8 is measured and the polarized reflected light is measured without performing the above adjustment. What is necessary is just to match | combine with the direction which the polarization axis of the polarization component contained most in 24a and the transmission axis 9b cross | intersect at 90 degrees.

In this state, the known object 21 and the table 5 are once removed and the position of the polarizing filter holder 8 is fixed, and a known calibration is performed as in the conventional three-dimensional shape measuring apparatus.
Thereafter, the table 5 is installed again, and the object to be measured 21 is fixed on the table 5.

Next, as in the first embodiment, the calculation unit 4 sends to the projector 2 modulation data for forming a certain shape measurement pattern light, for example, a checkered pattern, by the projector 2.
In the projector 2, the light projected from the light source is modulated by the spatial modulation element based on the modulation data from the calculation unit 4, and as shown in FIG. The pattern light 12 a is projected, whereby a checkerboard pattern is projected onto the DUT 1.

The pattern light 12a is divided into scattered reflected light 13a and polarized reflected light 24a. The scattered reflected light 13b and polarized reflected light 24b, which are polarized light in the direction along the transmission axis 9b of the polarizing filter 9, are transmitted through the polarizing filter 9. Incident on the CCD camera 3. The light incident on the CCD camera 3 is photoelectrically converted by the image pickup device of the CCD camera 3 and displayed on the monitor 15 as a reflected light image by the reflected light from the object to be measured 21, and sent to the arithmetic unit 4 to perform arithmetic processing. Is done.
Here, since the antireflection film 9a is provided on the surface of the polarizing filter 9 on the measured object 21 side, the reflection of the surface of the polarizing filter 9 with respect to the scattered reflected light 13a and the polarized reflected light 24a from the surface 21a. The rate is low enough. For this reason, the noise light component produced when the light reflected from the surface of the polarizing filter 9 toward the DUT 21 is re-reflected by the surface 21a is extremely small.

  In the calculation unit 4, the three-dimensional shape of the device under test 21 is calculated using the reflected light image acquired in this manner, and the calculation result is displayed on the monitor 15 in the same manner as in the first embodiment. .

As described above, in the three-dimensional shape measuring apparatus 200, the polarized light that causes the halation, the direction of the transmission axis 9 b of the polarizing filter 9, and the polarization axis of the polarized reflected light 24 a that is reflected by the measured object 21 and polarized. Since the brightness of the polarized reflected light 24b can be reduced by obtaining the reflected light image after adjusting so as to intersect the direction, a reflected light image in which the influence of noise components such as halation is reduced is obtained. can do. Thereby, since the reflected light image is acquired as an image having a good luminance difference, it is possible to reduce the non-measurable area even if the surface 21a of the object to be measured 21 is a glossy surface.
In addition, according to the three-dimensional shape measuring apparatus 200, since only one polarization optical element is required, the number of parts can be reduced and the apparatus configuration can be simplified.

  In the above description, when the position of the polarizing filter 9 in the direction of the transmission axis 9b is adjusted, the modulation of the pattern light 12a is invalidated and projected as an approximately uniform illumination light onto the object to be measured. However, if noise components such as halation can be evaluated, modulation data may be given and projected onto the object to be measured as pattern light for shape measurement.

  In the description of the first embodiment, the example in which the direction of the transmission axis 9b of the polarizing filter 9 is adjusted while the position of the transmission axis 7b of the polarizing filter 7 is fixed has been described. While the filter 9 is removed, a reflected light image of the object to be measured is acquired, and the polarizing filter holder 6 is rotated while viewing the reflected light image on the monitor 15 so that the halation area is minimized. After adjusting the rotation amount 6, the direction of the transmission axis 9 b of the polarizing filter 9 may be adjusted.

In the first embodiment, when the three-dimensional shape measuring apparatus includes the first and second polarizing optical elements, in the second embodiment, the three-dimensional shape measuring apparatus is the first polarizing optical element. However, the three-dimensional shape measuring apparatus of the present invention may include only the second polarization optical element.
For example, as described in the first embodiment, Fresnel reflection in a substantially planar measurement region like the object to be measured 21 generates strong polarized light. Therefore, such an object to be measured 21 is measured exclusively. In that case, the polarizing filter 9 and the polarizing filter holder 8 may be omitted from the three-dimensional shape measuring apparatus 100 of the first embodiment. In this case, since only one polarizing optical element is required, the number of parts can be reduced and the apparatus configuration can be simplified.

  In the above description, the polarizing filters 7 and 9 have been described as examples in the case where the antireflection structure including the antireflection films 7a and 9a is provided, but the reflected light on the surfaces of the polarizing filters 7 and 9 is described. When the amount returned to the object to be measured is sufficiently small, the antireflection films 7a and 9a may be omitted.

In the description of the first embodiment, the example in which the pattern light 12 b projected onto the DUT 1 is polarized using the polarizing filter 7 has been described. However, as the light source of the projector 2, linearly polarized light is used. If the laser beam is used, the polarizing filter 7 can be omitted.
Further, even when a reflective spatial modulation element is used as the spatial modulation element of the projector 2, the polarized light of the reflected light becomes strong, so that the polarization filter 7 can be omitted also in this case.

  Moreover, all the components described in the above embodiments and modifications can be implemented in appropriate combination within the scope of the technical idea of the present invention.

1, 21 DUT 1a, 21a Surface 2 Projector (projection unit)
3 CCD camera (imaging part)
4 Arithmetic Units 6 and 8 Polarizing Filter Holder 7 Polarizing Filter (Second Polarizing Optical Element)
7a, 9a Antireflection films 7b, 9b Transmission axis 9 Polarizing filter (first polarizing optical element, polarizing optical element)
10, 11 Rotation holding parts 12a, 12b Pattern light (pattern light for shape measurement)
13a, 13b Scattered reflected light 14, 24a, 24b Polarized reflected light 15 Monitor 100, 200 Three-dimensional shape measuring apparatus

Claims (7)

Projecting pattern light for shape measurement onto an object to be measured, obtaining a reflected light image by reflected light from the surface of the object to be measured, and calculating a three-dimensional shape of the object to be measured from the reflected light image An original shape measuring method,
A three-dimensional shape measurement method, wherein the reflected light image is acquired after passing at least one of the pattern light for shape measurement and the reflected light from the surface of the object to be measured through a polarizing optical element. Using polarized light for pattern light for shape measurement,
The direction of the transmission axis of the polarizing optical element is adjusted so as to intersect the direction of the polarization axis having the largest light quantity component of the reflected light reflected and polarized by the surface of the object to be measured, and then the reflected light The three-dimensional shape measurement method according to claim 1, wherein an image is acquired.   The angle at which the direction of the transmission axis of the polarizing optical element intersects with the direction of the polarization axis of the reflected light reflected by the surface of the object to be measured is adjusted to 90 °. The three-dimensional shape measuring method described. A projection unit that projects pattern light for shape measurement onto an object to be measured;
An imaging unit that captures an image of the measurement object on which the pattern measuring pattern light is projected by the projection unit, and obtains a reflected light image by reflected light from the surface of the measurement object;
A calculation unit that calculates a three-dimensional shape of the object to be measured from the reflected light image acquired by the imaging unit;
A polarizing optical element that is disposed between the object to be measured and the imaging unit and regulates the transmittance of reflected light from the surface of the object to be measured according to the polarization direction;
The polarizing optical element is provided so that the direction of the transmission axis can be adjusted.   The three-dimensional shape measuring apparatus according to claim 4, wherein an antireflection structure is provided on a surface of the polarizing optical element. A projection unit that projects pattern light for shape measurement onto an object to be measured;
An imaging unit that captures an image of the measurement object on which the pattern measuring pattern light is projected by the projection unit, and obtains a reflected light image by reflected light from the surface of the measurement object;
A calculation unit that calculates a three-dimensional shape of the object to be measured from the reflected light image acquired by the imaging unit;
A first polarizing optical element that is disposed between the object to be measured and the imaging unit and restricts the transmittance of reflected light from the surface of the object to be measured according to a polarization direction;
A second polarizing optical element that is arranged between the projection unit and the object to be measured and regulates the transmittance of the projection light projected onto the object to be measured according to the polarization direction;
At least one of the first polarizing optical element and the second polarizing optical element is provided so that the direction of the transmission axis can be adjusted.   The three-dimensional shape measuring apparatus according to claim 6, wherein an antireflection structure is provided on a surface of each of the first and second polarizing optical elements.