JP2741984B2 - 3D shape measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a continuous stereo image (E).
The present invention relates to an apparatus for measuring a three-dimensional shape of an object to be measured, based on pipolar-plane image (EPI).
In particular, three-dimensional shapes that can determine the corresponding points of multiple parallax original images at once without performing feature point extraction processing, and that can perform high-speed processing by hardware to measure the three-dimensional shape of the measured object It relates to a measuring device.

[0002]

2. Description of the Related Art In general, three-dimensional image measurement aims to measure the three-dimensional shape of a target object and its three-dimensional position in a non-contact manner. Recently, such three-dimensional image measurement has been demanded in a wide range of fields, and the performance required therefor is also various.

[0003] That is, there is a wide range of requirements from simple ones that do not require much accuracy to those that require very high accuracy. Further, according to the purpose, there are two types, one in which only the shape and relative positional relationship are simply measured, and the other in which only the absolute position is required.

[0004] As a method for measuring the three-dimensional shape of an object to be measured in a non-contact manner, a passive method (lens focus method, monocular vision, stereo method, moving image) and an active method (optical radar method) are used. , Active stereo method, photometric stereo method, moiré method, interferometry). In general, the active method has higher reliability, but the passive method is more general-purpose and has less restrictions such as the shape size of the object whose shape is to be measured. The present invention relates to a stereo method (continuous image method) as this passive three-dimensional shape measurement.

The stereo method applies the principle of triangulation,
This is a method of measuring the shape of the measured object from a plurality of original parallax images obtained by photographing the measured object from different positions.
The most important process of the stereo method is a process of finding out where a point visible in a certain original image corresponds to another original image, that is, a process of determining corresponding points (matching). Various methods such as image correlation have been considered as a method for determining the corresponding points. Generally, before determining the corresponding points, a process of extracting feature points of the original image is performed.

That is, a continuous stereo image is a two-dimensional image obtained by continuously stacking a large number of images while continuously moving a camera. When the camera is moved linearly, the corresponding point is located on a straight line on the continuous stereo image as shown in FIG. 7, and the depth of the corresponding point can be obtained from the inclination of the straight line. And conventionally,
As a method of obtaining three-dimensional information from a continuous stereo image,
A general method is to extract feature points from a continuous stereo image and perform matching of the feature points to calculate the inclination of a straight line of the continuous stereo image to obtain three-dimensional information.

[0007] However, such a method has a problem that three-dimensional information can be obtained only from an original image from which an appropriate feature point can be extracted. In other words, this feature point extraction is a process performed to simplify the determination of the corresponding points. However, it is necessary to change the feature point extraction process depending on the brightness, complexity, etc. of the original image. ing. In the case of an object having a curved surface, an error often occurs in determining a corresponding point.

When three or more parallax images are used as an original image, the process of determining corresponding points is performed a plurality of times, two images at a time, and tracking the corresponding points. For this reason, the processing takes a very long time, and there is a possibility that the corresponding errors are accumulated and become large.

Further, the conventional processing requires processing such as condition judgment and the like, and is not suitable for hardware measurement of a three-dimensional shape.

[0010]

As described above, in the conventional three-dimensional shape measuring method, not only is it necessary to perform feature point extraction processing, but errors in determining corresponding points are accumulated.
Further, there is a problem that the processing is not suitable for hardware and takes a very long time.

The present invention has been made in order to solve the above-described problems, and it is possible to determine the corresponding points of a plurality of parallax original images at a time without performing a feature point extraction process. It is an object of the present invention to provide an extremely reliable three-dimensional shape measuring apparatus capable of measuring a three-dimensional shape of an object to be measured by performing processing.

[0012]

According to the present invention, there is provided an apparatus for measuring a three-dimensional shape of an object to be measured, comprising a plurality of parallaxes obtained by photographing the object from different positions. A continuous stereo image creating means for creating a continuous stereo image of the measured object from the original image, a Fourier transform means for performing a Fourier transform process on the continuous stereo image created by the continuous stereo image creating means, and a Fourier transform means Filtering means for filtering only the sloping component in the frequency space in order on the transformed image, and inverse Fourier transform processing on the filtered image by the filtering means, and only a certain depth portion Inverse Fourier transform means for extracting the image of, and extraction by the inverse Fourier transform means Are composed image and a three-dimensional voxel data reconstruction means for reconstructing a three-dimensional voxel data.

[0013]

Therefore, in the three-dimensional shape measuring apparatus of the present invention, a continuous stereo image of the object to be measured is created from a plurality of original parallax images of the object to be measured from different positions, and this continuous stereo image is subjected to Fourier transform processing. Then, only the components of the inclination are sequentially filtered by the filter in the frequency space, and an image of only a certain depth portion is extracted by performing an inverse Fourier transform process.

Then, continuous stereo images of various heights of the original image are decomposed into directional components, and the continuous stereo images decomposed into directional components for each height are stacked in the depth direction. Three-dimensional voxel data is reconstructed by stacking each continuous stereo image at the created height position.

This eliminates the need to perform feature point extraction processing on an original image or a continuous stereo image.
Further, it is possible to determine the corresponding points of a plurality of parallax original images at once. Furthermore, high-speed processing by hardware can be performed because only Fourier transform and simple filtering processing are required, and higher-speed processing is performed because Fourier transform processing can be parallelized. be able to.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the concept of the present invention will be described.

In an ideal continuous stereo image (where the camera moves on a straight line and the optical axis of the camera is always perpendicular to the direction of movement), all corresponding points are on a straight line, and the inclination indicates information on depth. Is shown. The Fourier transform is for transforming a real space into a frequency space. When a straight line exists in the real space, a frequency component is generated in a direction orthogonal to the straight line, and when Fourier transform is performed, the distribution of the straight line in the frequency space exists in a portion orthogonal to the straight line. Therefore, when it is desired to extract only a straight line having a certain inclination, it is possible to extract only a straight line in a direction orthogonal to the filter by applying a fan-shaped filter in the frequency space and performing an inverse Fourier transform (FIG. 4).

Therefore, in the present invention, as shown in FIG.
By performing a Fourier transform process on a continuous stereo image, filtering only a gradient component in order by a fan-shaped filter in the frequency space, and performing an inverse Fourier transform process, an image of only a certain depth portion can be extracted.

Then, as shown in FIG. 6, the continuous stereo images of various heights of the original image are decomposed into three directional components, and the continuous stereo images decomposed into directional components at each height are separated in the depth direction. The three-dimensional space can be reconstructed by stacking the cross sections at a certain time and further stacking the cross sections at a certain time at the height position where each continuous stereo image is created. Here, for convenience of explanation, 3
Although it was decomposed into directional components, it can be decomposed into more directional components.

Hereinafter, an embodiment of the present invention based on the above concept will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an example of the overall configuration of a three-dimensional shape measuring apparatus according to the present invention. That is, as shown in FIG. 1, the three-dimensional shape measuring apparatus of the present embodiment is connected to a plurality of (four in the figure) cameras 11, 12, 13, and 14 arranged at regular intervals. Stereo image creating means 2, Fourier transform means 3, filtering means 4
, Inverse Fourier transform means 5, and three-dimensional voxel data reconstructing means 6.

Here, the cameras 11, 12, 13, 14
Is to capture a plurality of (four in the figure) parallax original images by photographing the measured object 7 from different positions.

The continuous stereo image creating means 2 creates a continuous stereo image of the measured object 7 from four original parallax images obtained by the cameras 11, 12, 13, and 14.

Further, the Fourier transform means 3 performs a Fourier transform process on the continuous stereo image created by the continuous stereo image creating means 2.

On the other hand, the filtering means 4 is for filtering only the gradient component of the image which has been subjected to the Fourier transform processing by the Fourier transform means 3 by a fan-shaped filter in the frequency space.

The inverse Fourier transform unit 5 performs an inverse Fourier transform process on the image subjected to the filtering process by the filtering unit 4 to extract an image of only a certain depth portion.

Further, the three-dimensional voxel data reconstructing means 6 reconstructs three-dimensional voxel data from the image extracted by the inverse Fourier transform means 5.

Next, the operation of the three-dimensional shape measuring apparatus of the present embodiment configured as described above will be described with reference to FIGS. FIG. 2 is a flowchart illustrating an example of processing using Fourier transform, and FIG. 3 is a flowchart illustrating an example of parallel processing using Fourier transform.

In FIG. 1, first, cameras 11, 12,
13 and 14, the object 7 to be measured is photographed from different positions, and four original parallax images are obtained.

Next, in the continuous stereo image creating means 2,
From the four parallax original images obtained by the cameras 11, 12, 13, and 14, a continuous stereo image of the measured object 7 is created.

Next, in the Fourier transform means 3, Fourier transform processing is performed on the continuous stereo image created by the continuous stereo image creating means 2, and the real space is converted into the frequency space.

Next, in the filtering means 4, the image subjected to the Fourier transform processing by the Fourier transform means 3 is subjected to the filtering processing only for the component of the inclination in order by the fan-shaped filter in the frequency space.

Next, in the inverse Fourier transform means 5, the images subjected to the filtering processing by the filtering means 4 are respectively subjected to inverse Fourier transform processing, and an image of only a certain depth portion is extracted.

Finally, the three-dimensional voxel data reconstructing means 6 reconstructs three-dimensional voxel data from the image extracted by the inverse Fourier transform means 5. That is, continuous stereo images of various heights of the original image are decomposed into directional components, continuous stereo images decomposed into directional components for each height are stacked in the depth direction, and further, a cross section at a certain time is The three-dimensional voxel data is reconstructed by being stacked at the height position where the continuous stereo images are created.

As described above, the three-dimensional shape measuring apparatus according to the present embodiment captures the object 7 to be measured from different positions and obtains four original parallax images.
4 and 4 obtained by the cameras 11, 12, 13, and 14.
A continuous stereo image creating means 2 for creating a continuous stereo image of the measured object 7 from the original parallax images, and a Fourier transform means for performing a Fourier transform process on the continuous stereo image created by the continuous stereo image creating means 2 3 and
Filtering means 4 for filtering only the components of the slopes sequentially with a fan-shaped filter in the frequency space on the image subjected to the Fourier transform processing by the Fourier transforming means 3, and inverse Fourier filtering on the image filtered by the filtering means 4. An inverse Fourier transform unit 5 for performing a conversion process and extracting an image of only a certain depth portion; a three-dimensional voxel data reconstructing unit 6 for reconstructing three-dimensional voxel data from the image extracted by the inverse Fourier transform unit 5 It consists of.

Therefore, it is not necessary to perform the process of extracting feature points in an original image or a continuous stereo image as in the related art.

Further, it is possible to determine the corresponding points of a plurality of parallax original images at once.

Further, since the measurement can be performed only by the Fourier transform and the simple filtering processing, high-speed processing by hardware is possible.

Furthermore, since the Fourier transform process can be parallelized, it is possible to perform a higher-speed process.

It should be noted that the present invention is not limited to the above embodiment, but can be implemented as follows.

In the above embodiment, four cameras 11, 1
The case where two, 13, and 14 are installed to obtain four parallax original images of the measured object 7 has been described. However, the present invention is not limited to this, and one camera is installed, and the cameras are arranged at a constant interval (pitch).
Alternatively, three parallax original images may be obtained by photographing the measured object 7 while moving on a straight line.

[0042]

As described above, according to the present invention, in a device for measuring a three-dimensional shape of a measured object, a plurality of original parallax images obtained by photographing the measured object from different positions are measured. A continuous stereo image creating means for creating a continuous stereo image of the object, a Fourier transform means for performing a Fourier transform process on the continuous stereo image created by the continuous stereo image creating means, and an image subjected to Fourier transform processing by the Fourier transform means In contrast, a filtering means for sequentially filtering only the components of the inclination by a filter in the frequency space, and an inverse Fourier transform processing on the image filtered by the filtering means are performed to extract an image of only a certain depth portion. An inverse Fourier transform means, and a cubic image from the image extracted by the inverse Fourier transform means. 3D voxel data reconstruction means for reconstructing voxel data, so that corresponding points of multiple parallax originals can be determined at once without performing feature point extraction processing. And a very reliable three-dimensional shape measuring apparatus capable of measuring the three-dimensional shape of the object to be measured by performing the above-described steps.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a three-dimensional shape measuring apparatus according to the present invention.

FIG. 2 is a flowchart for explaining the operation in the embodiment.

FIG. 3 is a flowchart for explaining the operation in the embodiment.

FIG. 4 is a schematic diagram for explaining the concept of the present invention.

FIG. 5 is a schematic diagram for explaining the concept of the present invention.

FIG. 6 is a schematic diagram for explaining the concept of the present invention.

FIG. 7 is a schematic diagram for explaining a relationship between a shooting position and an original image in a stereo method.

[Explanation of symbols]

11, 12, 13, 14 ... camera, 2 ... continuous stereo image creating means, 3 ... Fourier transform means, 4 ... filtering means, 5 ... inverse Fourier transform means, 6 ... 3D voxel data reconstruction means, 7 ... measured object.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Susumu Takahashi 1-5-1, Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd. (72) Inventor Katsuo Honda 1913-12 72) Inventor Masahiro Yamaguchi 4-1-1-502, Kamata, Setagaya-ku, Tokyo (72) Inventor Nagaaki Oyama 2-3-9 Kannon, Kawasaki-ku, Kawasaki-shi, Kanagawa (56) References JP-A-2-257011 (JP) JP-A-2-206294 (JP, A) JP-A-2-100589 (JP, A) JP-A-59-183326 (JP, A)

Claims (1)

(57) [Claims] 1. An apparatus for measuring a three-dimensional shape of an object to be measured, wherein a continuous stereo image of the object to be measured is created from a plurality of original parallax images obtained by photographing the object to be measured from different positions. Stereo image creating means, Fourier transform means for performing Fourier transform processing on the continuous stereo image created by the continuous stereo image creating means, and an image subjected to Fourier transform processing by the Fourier transform means, in a frequency space. A filtering unit that sequentially filters only components of the inclination by a filter, and an inverse Fourier transform unit that performs an inverse Fourier transform process on the image filtered by the filtering unit and extracts an image of only a certain depth portion, From the image extracted by the inverse Fourier transform means, a three-dimensional box Three-dimensional shape measuring apparatus characterized in that it comprises a three-dimensional voxel data reconstruction means for reconstructing the data.