JP2009204373A - Light-projecting device and three-dimensional shaped measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost small light-projecting device capable of high-speed, wide-range measurement with high accuracy, and to provide a three-dimensional shaped measuring apparatus. <P>SOLUTION: The three-dimensional shaped measuring apparatus 1 comprises: a light source 3 generating belt-like light beams; scanning devices 4, 5 for scanning a projection plane with the light emitted from the light source; a light source control device 6 for controlling the light amount from the light source 3; an imaging device 7; and an image processing device 8 for capturing the image information from the imaging device 8 and calculating three-dimensional information. The light beams are moved parallel, in a direction perpendicular to the length direction on the projection plane by the scanning devices 4, 5, and the light amount from the light source 3 is changed by the light source control device 6 which makes the parallel movement of the light beams synchronized. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

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

As a technique for optically measuring a three-dimensional shape, a method based on trigonometry is performed. For example, Patent Document 1 describes a three-dimensional measurement apparatus and method based on a light cutting method. A diffuser plate on which the object to be measured is placed, one or more illumination light sources installed below the diffuser plate, a light projecting device that irradiates the diffuser with line light from above, and an object above the object to be measured A three-dimensional measuring device comprising an arranged image pickup means, an object insertion hole, a control section, and an image processing section, wherein the image pickup means is an alternative light source for illumination and illumination The image processing unit calculates the two-dimensional shape information of the measurement object from the image at the time of illumination light source irradiation, calculates the height information of the measurement object from the image at the time of line light irradiation, The three-dimensional measurement information of the object to be measured is calculated from these pieces of information.

In addition, there is a method called a grid projection method, in which light of a grid pattern is projected and imaged on a measurement target surface, and the entire surface is analyzed at once to obtain contour information. Here, in order to project light with a grid pattern, there are a method using a projector (Patent Document 2), a method of irradiating light from a halogen lamp through a glass plate or the like on which a grid pattern is written (Patent Document 3), and the like. is there. In addition, a technique for projecting periodic stripes by displaying periodic stripes on a liquid crystal panel and passing light therethrough has also been implemented.
JP 2006-98384 A Japanese Patent No. 3507865 Japanese Patent No. 3554816

With the light cutting method described in Patent Document 1, only information that appears on one light beam can be captured by one imaging. In order to obtain all information on the target surface, it is necessary to repeat imaging while translating linear rays. Therefore, it takes a long time to acquire the entire information. Accordingly, the measurement time becomes long. Also, it cannot follow things that move in a short time.

On the other hand, according to the lattice projection method, since the entire surface can be analyzed at once, the measurement time is short and real-time measurement is also possible. However, in the lattice projection using a projector, since the projector itself is large and expensive, the entire measuring apparatus is also expensive. When using a glass plate or the like with a lattice pattern, a plurality of glass plates must be prepared and used while changing the lattice pattern. The method of displaying periodic stripes on the liquid crystal panel can change the projection pattern at a relatively high speed, but the amount of light is reduced when light passes through such a liquid crystal panel. Discontinuity of light caused between liquid crystal pixels occurs, and the resolution in the scanning direction is limited by the number of pixels. Since the brightness is controlled digitally, it must be stepped to the degree of shading. Furthermore, in the conventional methods of projecting light through a lens, the in-focus range is limited, and surface observation with a large height difference cannot be performed.

An object of the present invention is to provide a light projection device and a three-dimensional shape measuring device that can measure a wide range at high speed and with high accuracy, and that are small and inexpensive.

In order to solve the above-described object, an optical projection device of the present invention includes a light source that generates a strip-shaped light beam, a scanning device that scans light projected from the light source onto a projection surface, and a light source that controls the light amount of the light source. And a light source control device for changing the light quantity of the light source in synchronization with the parallel movement of the light beam. To do. As a scanning device, a mirror that reflects the light beam projected from the light source and a driving device that moves the mirror can be used. Here, the periodic change is a sine wave function, and projection is performed while shifting the phase by π / 2, imaging is performed for each phase, and three-dimensional shape information can be calculated from four times of image information. This is true. Furthermore, the projection and imaging of the light beam based on the sine wave function of the first cycle and the projection and imaging of the light beam based on the sine wave function of the second cycle different from the first cycle may be performed. it can.

A three-dimensional shape measuring apparatus according to the present invention includes the above-described optical projection apparatus, an imaging apparatus, and an image processing apparatus that takes in image information from the imaging apparatus and calculates three-dimensional shape information. The light source controller synchronizes with the parallel movement of the light beam to change the light quantity of the light source based on the sine wave function, and further, the projection is performed while shifting the phase by π / 2, and imaging is performed for each phase. Three-dimensional shape information can be calculated from the image information of the batch. Further, the projection and imaging of the light beam based on the sine wave function of the first cycle and the projection and imaging of the light beam based on the sine wave function of the second cycle different from the first cycle are performed to obtain a three-dimensional shape. Information can be calculated.

The light projection device and the three-dimensional shape measurement device according to the present invention measure the band of light projected from the light source on the projection surface by the scanning device while changing the light amount of the light source in conjunction with the movement. A predetermined pattern of light can be projected onto the surface, and high-speed three-dimensional shape measurement can be performed with a small device. The pattern of the projection light can also be set freely, which has the effect that it can be used for various measurements.

The best mode for carrying out the present invention will be described. FIG. 1 is a block diagram showing an outline of a three-dimensional shape measuring apparatus. The three-dimensional shape measuring apparatus 1 captures image information from a light source 3 that generates a strip-shaped light beam, a scanning device, a light source control device 6 that controls the amount of light of the light source, an imaging device 7, and the imaging device 7 to obtain a three-dimensional shape. And an image processing device 8 for calculating shape information.

That is, the light projection device 2 includes a light source 3, a scanning device, and a light source control device 6. The light source 3 generates a strip-shaped light beam. That is, it is parallel light in the width direction of the band shape. On the other hand, it extends in the length direction according to the distance from the light source. As such a light source, an apparatus having a configuration in which light from a halogen lamp or a light-emitting diode is formed into a belt-like light beam by two types of lenses may be used. In this embodiment, a line laser is used as the light source 3.

The scanning device scans light projected from a light source on a projection surface. The light source 3 itself may be moved, or an optical element such as a mirror or a prism that changes the direction of the light beam may be rotated or translated. In this embodiment, it is configured as an apparatus that uses the mirror 4. The mirror 4 has a rotating shaft 9 and is rotatable about the rotating shaft 9. A driving device 5 for rotating the mirror 4 is connected to the rotating shaft 9. Here, the term “rotation” includes not only the case of continuing to rotate in a certain direction but also the case of swinging within a certain angle range. The light emitted from the line laser 3 is turned by the mirror 4 and projected onto the measurement target surface.

The power supply 10 of the line laser 3 can adjust the output, thereby changing the intensity of the laser beam.

The power source 10 of the driving device 5 and the line laser 3 is controlled by the light source control device 6.

The imaging device 7 captures a measurement target surface as an image, and a digital camera, a video camera, or the like can be used. An image processing device 8 is connected to the imaging device 7. The image processing device 8 acquires image information from the imaging device 7 and calculates three-dimensional shape information of the measurement object from the image information. The calculated three-dimensional shape information is output to a display device 11 such as an image monitor by, for example, contour display.

The light source control device 6 and the image processing device 8 may be configured as separate equipment, but may be configured as a single unit by a general-purpose personal computer or the like.

Next, the operation of this three-dimensional shape measuring apparatus and a three-dimensional shape measuring method using the same will be described. The laser light emitted from the line laser 3 is turned by the mirror 4 and projected onto the target surface. Here, the positions of the line laser 3 and the mirror 4 are set so that the length direction of the laser light is parallel to the rotation axis 9 of the mirror 4. Further, the rotation axis 9 of the mirror 4 is set substantially parallel to the projection plane. The laser light is projected in an oblique direction with respect to the projection plane. Since there is no element that reduces light between the line laser 3 as the light source and the projection surface, a strong light beam can be projected.

When the mirror 4 is rotated by the driving device 5, the direction of the reflected light changes. As a result, the laser light moves on the target surface. If the distance between the mirror 4 and the target surface is sufficiently long with respect to the width of the target surface, the rotation angle of the mirror 4 and the amount of movement of the laser light are substantially proportional. If the output of the power supply 10 is changed in conjunction with the rotation of the mirror 4, the intensity of the laser light changes while moving on the target surface. Here, the belt-like laser light moves in parallel on the projection plane in a direction perpendicular to the length direction. The light source control device 6 controls the power source 10 so that the intensity of the laser beam varies at a predetermined period with respect to the moving length.

The rotational speed of the mirror 4 is set sufficiently high, and the band-shaped laser light is scanned in a shorter time than the time required for the imaging device 7 to perform one imaging, so that the desired light is projected onto the target surface. Strength is formed. For example, a periodic pattern by a laser beam is realized by causing the light source control device 6 to periodically change the amount of light. FIG. 2 is a plan view schematically showing a projection pattern on the measurement target surface. Here, it is assumed that the surface to be measured has no unevenness. The y axis is taken along the length direction of the laser beam, and the x axis is taken in the direction perpendicular to the y axis. The pattern is such that the amount of light periodically changes along the x direction. Here, the length of the pattern in the y direction is determined by the distance from the line laser 3 to the projection plane. On the other hand, the repetition interval of the pattern in the x direction is determined by the output modulation period of the power source, the rotation speed of the mirror 4, and the distance from the mirror 4 to the projection plane. Therefore, the pattern in the x direction can be freely set depending on how the output modulation of the power supply is controlled. By performing output modulation of the power supply in an analog manner, light intensity can be continuously controlled. Since the scanning is also continuously performed by the swinging of the mirror, the shading change along the scanning direction can be continuously formed. Therefore, the resolution in the scanning direction of this optical projection apparatus may be considered as unlimited.

FIG. 3 is a graph showing a change in light amount in the x direction. In this example, the amount of light changes along the x axis according to a sine wave function. If the light quantity at the brightest point is Imax, the light quantity at the darkest point is Imin, and the repetition period is λ, the light quantity at a certain point (x, y) is
I (x, y) = (Imax−Imin) · sin (2πx / λ) + Imin
It becomes. Thus, phase analysis can be performed by projecting with a pattern based on a sine wave function.

A three-dimensional shape is measured on this projection plane. Laser light is projected in a pattern as shown in FIG. 3, and the first imaging is performed by the imaging device 7. This image data is captured by the image processing device 7 and stored in the storage area m1. Next, irradiation is performed with a pattern in which the phase is shifted by π / 2, that is, a pattern that is shifted by a distance of λ / 4 in the x direction with the same repetition period λ. Such a pattern can be easily and accurately generated by the light source control device 6. In this way, the second imaging is performed, and the image data is stored in the storage area m2. Further, the third and fourth imaging are performed while shifting the pattern by π / 2, and the image data is stored in the storage area m3 and the storage area m4. As described above, information necessary for one measurement can be acquired by four times of imaging.

Next, phase analysis using these image data will be described. The measurement brightness data for a certain point (x, y) is read from the storage areas m1 to m4 as the first to fourth imaging data. These values are I0, I1, I2, and I3.

FIG. 4 is a graph showing an outline of the phase shift method. The relationship between the four luminance data I 0, I 1, I 2, and I 3 for the point (x, y) and the phase of the projected light pattern is shown in the graph as follows.
I (x, y) = a (x, y) .cos (θ (x, y) + α) + b (x, y)
Here, a and b are coefficients depending on the reflectance of the point, θ is phase data including height information, α is the phase of the sine wave of the projection light pattern (here, 0, π / 2, π, 3π / 2). The phase data θ can be obtained by the following procedure.

I0, I1, I2, and I3 are respectively
I0 = a · cos θ + b
I1 = a · cos (θ + π / 2) + b = −a · sin θ + b
I2 = a · cos (θ + π) + b = −a · cos θ + b
I3 = a · cos (θ + 3π / 2) + b = a · sin θ + b
It becomes. As described above, the coefficients a and b depending on the reflectance can be eliminated from the equation (4), and θ can be obtained by the following equation.
tan θ = − (I3−I1) / (I2−I0)

First, without placing anything on the reference projection plane, as described above, images are captured in a pattern of α = 0, π / 2, π, 3π / 2, and phase data θ is obtained for each value of x. The phase data on this reference plane is defined as θb (x).

Next, an object to be measured is placed on the projection surface, and images are captured in a pattern of α = 0, π / 2, π, 3π / 2. The phase data θ is obtained from the measured luminance data I0, I1, I2, and I3 for a certain point (x, y). This phase data is θt (x, y). Then, the phase shift θd due to the height of the point with respect to the reference plane is θd = θt (x, y) −θb (x).
Is required. From this θd, the height of the point (x, y) can be obtained.

As described above, by performing the same calculation for all points, the three-dimensional shape information of the entire measurement target surface can be calculated. This can be displayed on the display device by contour lines, for example.

As described above, the three-dimensional shape measurement was performed once only by four times of imaging. If the height difference is relatively small and within the repetitive period width of the projection pattern, it can be measured accurately. However, when the phase θ due to the height difference is larger than the repetition period width of the projection pattern, the phase corresponding to the height is θ + 2nπ (n = integer).
Therefore, it is necessary to obtain n. Therefore, after performing the above-described measurement at the first period λ1 as the pattern period width, the measurement can be performed again at the second period λ2 which is another pattern period width.

If the phase obtained by the period λ1 is θ1, and the phase obtained by the period λ2 is θ2, the phase that can correspond to each height is θ1 + 2nπ (n = integer)
θ2 + 2mπ (m = integer)
However, the only n or m that satisfies this can be determined.

It is a block diagram which shows the outline | summary of a three-dimensional shape measuring apparatus. It is a top view which shows typically the projection pattern on a measurement object surface. It is a graph which shows the light quantity change in x direction. It is a graph which shows the outline | summary of a phase shift method.

Explanation of symbols

1. 1. Three-dimensional shape measuring device 2. Light projection device Light source (line laser)
4). Mirror 5 Drive device 6. 6. Light source control device Imaging device 8. Image processing device

Claims (5)

A light source that generates a strip-shaped light beam, a scanning device that scans the light projected from the light source onto the projection surface, and a light source control device that controls the amount of light from the light source. A light projection device characterized by being translated in a direction perpendicular to the direction and changing the light quantity of the light source in synchronization with the parallel movement of the light beam by a light source control device. The light projection device according to claim 1, further comprising: a mirror that reflects a light beam projected from a light source as a scanning device; and a drive device that moves the mirror. A three-dimensional shape measuring apparatus comprising: the light projection device according to claim 1; an imaging device; and an image processing device that calculates image information by taking image information from the imaging device. The light source controller synchronizes with the parallel movement of the light beam and changes the light amount of the light source based on a sine wave function, performs projection while shifting its phase by π / 2, and performs imaging for each phase. The three-dimensional shape measurement apparatus according to claim 3, wherein the three-dimensional shape information is calculated from four times of image information. 5. The projection and imaging of a light beam based on a sine wave function having a first cycle and the projection and imaging of a light beam based on a sine wave function having a second cycle different from the first cycle. The three-dimensional shape measuring apparatus described.

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