JP3798212B2 - 3D shape measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to three-dimensional shape measurement using light.
[0002]
[Technical background]
The three-dimensional shape measurement is roughly classified into various methods as shown in FIG. Applications are being made not only in the fields of molds, mechanical engineering, electrical / electronics, and optics, but also for 3D measurement of living organisms and soft materials. In this three-dimensional shape measurement, a free-form surface and a complicated shape measurement can be performed. For this reason, higher accuracy and higher resolution are required, and high-speed measurement is desired. For this reason, research and development of a non-contact method using light is active among various three-dimensional shape measurements as shown in FIG.
Non-contact three-dimensional measurement using light includes, for example, a light cutting method, a light scanning method, a moire topography method, and the like shown in FIG. Many of these measurements use an optical confocal method that utilizes a decrease in light intensity during defocusing. In the measurement by this method, in order to eliminate the blind spot for causing a shadow and increase the measurement speed, it is necessary to move the target object or the measurement system, and there is a limit to speeding up.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to obtain a three-dimensional shape measuring apparatus capable of measuring a three-dimensional shape with a configuration in which a shadow is hardly generated.
[0004]
[Means for Solving the Problems]
To achieve the above object, the present invention provides a three-dimensional shape measuring apparatus for measuring a three-dimensional shape of an object using light, a two-dimensional light source having an angle with respect to an optical axis, and the two-dimensional light source. An optical system for projecting an image on the object, scanning means inserted in the optical system, a sensor for detecting the intensity of reflected or transmitted light of the two-dimensional light source image from the measurement object, and And a means for forming a plurality of the two-dimensional light source images by the scanning means , and the optical axis direction is defined as the z-axis based on the detected data of the reflected light or transmitted light of the plurality of detected two-dimensional light source images. Z-axis coordinates that maximize the light intensity are obtained for all x and y coordinates from the detected two-dimensional light source images, and the cubic is obtained. It is characterized by forming an original shape.
With this configuration , the measurement can be performed without producing a shadow and without moving the measurement target, so that the three-dimensional shape can be measured at high speed.
[0005]
When obtaining the z-axis coordinate at which the light intensity is maximum, the z-axis coordinate at which the maximum is obtained can be obtained by applying the data obtained to the convex function.
The scanning unit may be a mirror scan using a reflecting mirror that rotates.
The two-dimensional light source may be, for example, a parallel light and pinhole or diffraction optical element array, a light emitting diode array, or a laser beam two-dimensional scan as a two-dimensional point light source array.
At this time, it is also possible to detect the intensity of the reflected light or transmitted light from the object via a pinhole array having the same configuration as the two-dimensional point light source array.
The two-dimensional light source is a planar light source having a sinusoidal light intensity distribution, and frequency-filtering detection data of reflected light or transmitted light of a plurality of detected two-dimensional light source images, It can also be formed.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in detail with reference to the drawings.
In the present invention, in order to measure in the depth direction, a two-dimensional surface light source is arranged inclined with respect to the optical axis direction, and the reflected light from the object of the image is detected by a photodetector using a confocal method. A three-dimensional shape is measured by measuring and optically scanning.
A configuration example of the embodiment will be described with reference to FIG. In this configuration, in order to configure the surface light source as a point light source array, the light from the light source 10 is converted into parallel rays by the lens 71 and then passed through the two-dimensional pinhole array 40. On the object plane of the imaging system (lens 73, lens 74) provided with the scanner 50, the pinhole array 40 is installed at an angle of 0 to 90 degrees with respect to the optical axis. A two-dimensional light spot array tilted with respect to the optical axis is formed on the image plane, and this is projected onto the object 60. The reflected light from the pinhole image 45 formed on the object is passed through the pinhole array 40, and the transmitted light amount is measured by the detector array 20. When the light spot is focused on the measurement object, the reflected light forms an image on the pinhole array 40, so that the amount of transmitted light increases. By tilting the pinhole array 40, a tilted cross-sectional image can be measured. By driving the scanner 50 and moving the inclined light spot image 45 in a direction perpendicular to the optical axis and including the component of the normal vector of the inclined surface, the three-dimensional space can be scanned. By measuring the position where the intensity of the reflected light transmitted through the pinhole array 40 increases, information on the surface shape of the object 60 can be obtained.
[0007]
The method for obtaining the surface shape will be described in detail. For each position of the scanner 50, the light intensity is detected by the optical sensor array 20 to obtain a plurality of two-dimensional data. By using the fact that the light quantity is the maximum when the light spot is focused on the object, the obtained two-dimensional data is stacked to obtain received light three-dimensional data.
Now, the z axis perpendicular to the x and y coordinates on the plane on which a certain object is placed is the optical axis. Using this, all the light intensities at certain x and y coordinate points in the obtained two-dimensional data are compared to determine the z-axis coordinate that provides the maximum light amount. Similarly, for all x and y coordinates, z-axis coordinates that maximize the light intensity are obtained and used as surface shape data.
When obtaining the z-axis coordinate at which the light intensity becomes maximum, a convex function such as a Gaussian function is applied to the obtained intensity distribution data in the z-axis direction, so that the position where the maximum value of the light intensity is obtained can be further determined. It can be determined accurately.
[0008]
<Example>
In the shape measurement system (see FIG. 3) in the embodiment, the light source 10 is a halogen lamp and the pinhole array 40 is formed by etching a metal thin film. The pinhole diameter was 50 μm, and the pinholes were arranged at a pitch of 150 μm in the x direction and 300 μm in the y direction. The effective pinhole part is 10 mm square. The pinhole array 40 is installed so as to be inclined at about 45 degrees with respect to the optical axis. The pinhole array 40 projected an inclined light spot array onto the target object 60, scanned while rotating the mirror 50, and the reflected light was measured by the CCD camera 20. Unlike the above-described embodiment, the CCD camera detects reflected light without going through a pinhole array.
[0009]
FIG. 4 shows an observation image when a white sphere having a diameter of 3.2 mm is used as a target object. In the example of each observation image shown in FIGS. 4A to 4D, it can be seen that plane images at different positions of the scanner are obtained. While scanning in this manner, the measurement was performed 13 times in synchronization with the mirror scanner position.
Sampling is performed from such a measurement image at a pinhole position, and a place with light intensity below a certain threshold is regarded as the background and masking is performed. Coordinates in the object are determined for each point on the plane of the obtained data from the positional relationship of the imaging corresponding to each scanner position. The maximum value of the light intensity is obtained for each depth direction of the object between the measurement data, and the position in the depth direction that takes the maximum value is determined as the presence position of the surface of the object. The measurement result of the obtained object surface shape is shown in FIG. The shape shown in FIG. 5 is smoothed to remove noise.
[0010]
<Other embodiments>
Unlike the configuration of the embodiment shown in FIG. 2, the pinhole array having the same configuration as that of the pinhole array 40 on the light source side is provided in front of the detector array 20 without using the pinhole array 40 as a light source. The array may be installed at the same tilt angle with respect to the optical axis.
Moreover, the use efficiency of light can be improved by using a microlens for each pinhole of the pinhole array 40 used in the above embodiment.
In the above-described embodiment, in order to obtain a two-dimensional point light source, a pinhole array is installed with respect to parallel light from the light source. However, for example, a light emitting diode array or a laser is used. It is possible to scan the beam two-dimensionally or use a diffraction optical element that forms a light spot array.
As scanning for obtaining a plurality of cross-sectional images, coherent light is used as a light source, diffraction is performed by an acoustooptic device, and a diffraction angle is changed, so that scanning similar to that of the above-described mirror scanner can be performed.
Further, in the above-described embodiment, the shape is detected using the pattern by the point light source, but in addition to this, a planar light source having a sinusoidal density distribution installed at a certain angle with respect to the optical axis is used. It may be used. In this case, the obtained image is subjected to frequency filtering to detect a light intensity that is relatively maximum, to obtain a coincidence of focus, and to form a three-dimensional shape.
When the measurement object is moving with respect to the optical axis, such as when the target object 60 in FIG. 2 is on a conveyor, the mirror scanner 50 in FIG. 2 is not necessary.
If the measurement system shown in FIG. 2 is configured to detect light below the object 60 and detect transmitted light, it can also be used to measure a transmitted object.
In addition, since an oblique light source having different focal points is used, this system records information by distributing, for example, a minute portion whose refractive index has changed in the volume of a transparent medium in multiple layers. It can also be applied to optical memory reading.
[0011]
<Advantages of the present invention>
By using such a configuration, the present invention has the following advantages.
In the present invention, since the projection of light and the detection of the reflection thereof are in the same direction, a shadow that causes a problem does not occur in a technique based on triangular measurement such as a light cutting method.
Further, since optical scanning by a scanner is used, it is not necessary to move an object, and the speed can be increased.
Since interference is not used for measurement, it is highly resistant to vibration.
Since the light having the strongest reflected light is detected, the influence of the intensity difference of the reflected light due to the light absorption of each portion of the measurement object can be suppressed.
The three-dimensional shape generation process after the detection of the reflected light is simple, and real-time processing is easy due to high-speed signal processing.
Since the formation of a three-dimensional image by this configuration is in principle compatible with volume scanning type stereoscopic display, there is a possibility of a stereoscopic television system.
[0012]
【The invention's effect】
With the configuration of the present invention, it is possible to obtain a three-dimensional shape of an object without causing a blind spot due to a shadow.
[Brief description of the drawings]
FIG. 1 is a diagram showing a conventional three-dimensional shape measurement.
FIG. 2 is a diagram illustrating a configuration of an embodiment.
FIG. 3 is a diagram illustrating a configuration of an example.
FIG. 4 is an example of a measurement image of an object (sphere) obtained from the example.
FIG. 5 is a diagram illustrating a shape of an object generated from a measurement image.
[Explanation of symbols]
10 Light source 20 Detector array (CCD camera)
30 Beam splitter 40 Pinhole array 45 Pinhole array image 50 Mirror scanner 60 Object 71, 72, 73, 74 Lens

Claims (7)

In a three-dimensional shape measuring apparatus that measures the three-dimensional shape of an object using light,
A two-dimensional light source having an angle with respect to the optical axis;
An optical system that projects the two-dimensional light source so as to form an image on the object;
Scanning means inserted into the optical system;
A sensor that detects the intensity of reflected or transmitted light of the two-dimensional light source image from the measurement object;
Means for forming a plurality of the two-dimensional light source images by the scanning means, and based on detected data of reflected light or transmitted light of the plurality of detected two-dimensional light source images, the optical axis direction is defined as the z axis, Assuming that the coordinates in the direction perpendicular to x and y are x and y, the z-axis coordinate that maximizes the light intensity is obtained for all x and y coordinates from the detected two-dimensional light source images. A three-dimensional shape measuring apparatus characterized by forming a shape. The three-dimensional shape measuring apparatus according to claim 1,
A three-dimensional shape measuring apparatus for obtaining a maximum z-axis coordinate by applying data obtained to a convex function when determining a z-axis coordinate having a maximum light intensity. 3. The three-dimensional shape measuring apparatus according to claim 1 , wherein the scanning unit is a mirror scan using a reflecting mirror that rotates. The three-dimensional shape measuring apparatus according to any one of claims 1 to 3 , wherein the two-dimensional light source is a two-dimensional point light source array. In the three-dimensional shape measuring apparatus according to claim 4 ,
The two-dimensional point light source array is selected from a parallel beam and pinhole or diffraction optical element array, a light-emitting diode array, and a two-dimensional scan of a laser beam. Shape measuring device. In the three-dimensional shape measuring apparatus according to claim 4 or 5 ,
A three-dimensional shape measuring apparatus for detecting light intensity of reflected light or transmitted light from an object through a pinhole array having the same configuration as the two-dimensional point light source array. In the three-dimensional shape measuring apparatus according to any one of claims 1 to 3
The two-dimensional light source is a planar light source having a sinusoidal light intensity distribution, and forms a three-dimensional shape after frequency-filtering the detected data of reflected light or transmitted light of a plurality of detected two-dimensional light source images. A three-dimensional shape measuring apparatus.

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