JP2006084452A - Apparatus for measuring object - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus capable of detecting the position of an object with a mirror finished surface and a normal direction thereof, with high precision, stability, and reliability. <P>SOLUTION: The apparatus for measuring an object comprises at least one pattern plate, a half mirror, an image inputting means for observing a reflected image or a virtual image on the pattern plate via the half mirror to obtain an input image, a means for separating the image into images corresponding to the pattern plate or a region in the pattern plate, an image-pattern associating means for associating an image point of the separated image with a pattern position on the pattern plate, an incident light calculating means for calculating incident light just before incidence upon a reflection point, a reflected light calculating means for calculating reflected light advancing from the reflection point to the image point, and a reflecting point calculating means for calculating the cross point of the incident light and the reflected light. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

Detailed Description of the Invention

[Technical field to which the invention belongs]
The present invention relates to an object measuring apparatus that measures the position and shape of a mirror surface.

[Conventional technology]
Conventional object shape measurement methods target diffusely reflective objects and are generally difficult to apply to specular objects. However, shape measurements of specular objects are required in many fields including industrial applications.
Much research has been conducted on an active method for measuring the position and shape of a mirror surface by projecting a laser beam. In the spot light scanning light cutting method, an example in which the metal surface shape of the solder part is measured using the spot projection method, or the light source and the camera are arranged at substantially the same position and the LED light is returned to the light source direction again. An example in which a mirror surface is measured by detecting a light angle by mechanical scanning has been proposed. However, to increase the measurement resolution, light scanning and a large amount of image input are required.
On the other hand, for the passive method, an example is reported in which the normal direction of the mirror surface is detected and the shape is restored using the illumination of the coded grating light source, assuming reflection on a fixed reference surface. ing. In order to obtain high accuracy, it is limited to the case where the light source is sufficiently far away and the mirror surface is sufficiently small. There is an example that proposes the use of coding pattern projection as a method to solve the drawback, and the feature is that the reference plane is corrected / updated using the local specular normal direction. However, there is a problem that as the distance from the reference point increases, errors are accumulated on the updated reference surface and the measurement error tends to increase.

[Problems to be solved by the invention]
An object of the present invention is to provide means for measuring the position and shape of a mirror surface with high resolution, high accuracy, and high stability by using a pattern plate placed on the front surface of the mirror surface and an image input device. To do.

[Means for solving problems]
In the present invention, at least one pattern plate, a half mirror, and an image input means for obtaining an input image by observing a reflected image or a virtual image of the pattern plate via the half mirror, and separating the images Means for associating an image point of the input image with a pattern position on the pattern board, an incident light ray calculating means for calculating an incident light ray immediately before the reflection point is incident, and a reflection point Reflected light ray calculating means for calculating a reflected light ray traveling to the image point, and reflective point calculating means for calculating an intersection point of the incident light ray and the reflected light ray as a reflection point.

[Embodiment of the Invention]
A first embodiment will be described with reference to FIG. A camera 1 is placed on the left side, and pattern plates 2 and 3 are placed on two places on the right side. The mirror surface 4 to be measured is placed at an arbitrary position, and a virtual image of the pattern plate 2 or 3 is observed by the camera 1.

An arbitrary image point i on the camera image pickup device is a virtual image position at a position p ₁ on the pattern plate 2 and at the same time a virtual image point at a position p ₂ on the pattern plate 3, and these p ₁ , p ₂ Can be detected, the light ray trajectories T ₁ and T ₂ that have passed before the light ray incident on the imaging point i is reflected by the mirror surface 4 can be determined. However, T ₁ and T ₂ are on the same straight line. Ray trajectories after specular T ₃ is determined by the lens principal point and the imaging point position. For this reason, the position of the reflection point A on the mirror surface can be determined by the principle of triangulation.

The imaging point i is given by a feature point on the image. The corresponding positions p ₁ and p ₂ on the pattern plates 2 and 3 are detected by pattern matching between the pattern on the pattern plate and the camera input image. can do. Increasing the number of measurement points as much as possible instead of a single one can be easily realized by displaying the structured pattern on the pattern plate and increasing the number of feature points. When inputting the image of the pattern plate 3, the pattern plate 2 is removed or the pattern plate 2 is moved to the position of the pattern plate 3. The pattern plates 2 and 3 do not necessarily have to be parallel if their directions are known. The pattern plate 2 can be transparent or semi-transparent, and the pattern plate 2 can be transparent or semi-transparent when inputting the image of the pattern plate 3, thereby avoiding movement of the pattern plate. This can be realized by using a transmissive liquid crystal panel. Further, if the pattern plate module is configured using the pattern plate, the handling becomes easy. On the other hand, in order to switch the images of the pattern plates 2 and 3, a mirror may be installed, and the optical path may be switched by moving or rotating the mirror.

FIG. 2 shows the measurement procedure. After entering an image of a pattern plate 2 (11), to identify the corresponding positions p ₁ on each image point i and the pattern plate 2 (12). Then, enter the image of the pattern plate 3 (13), to identify the corresponding position _{p 2} on each image point i and the pattern plate 3 (14). Next, paying attention to the fact that the light rays emitted from p ₁ and p ₂ corresponding to the same image point become the common incident light on the mirror surface, the incident light ray T ₁ is calculated. On the other hand, it calculates the reflected ray T ₃ reaching the image point i reflected by the reflection point A from the camera parameters and the image point. If the intersection of T ₁ and T ₃ is calculated, the position is the position of the reflection point A, and the normal direction n of the mirror surface at the reflection point can also be obtained.

A second embodiment is shown in FIG. A light ray T ₄ from a position p ₁ on the pattern plate 22 passes through the red filter 25 and the half mirror 23 to become a light ray T ₁ , and is reflected by a reflection point A on the mirror surface 4 to become a light ray T ₃ . Image point i is reached. On the other hand, light T ₅ leaving the position p ₂ on the pattern board 22 corresponding to the same image point passes through the blue filter 26, reflected by the mirror 24 and the half mirror 23, consistent with the light T ₁ of the from p ₁ After reaching the reflection point, the image point i is reached. The input image obtained by the color camera 21 is separated into a red component and a blue component. The red component image is created by light passing through the red filter, and the blue component image is created by light passing through the blue filter. Image. Thus, for each pixel, the position of the position and p ₂ of the p ₁ is obtained. If the arrangement of the half mirror 23 and the mirror 24 is determined, the light beam T ₁ can be calculated, while the position of the reflection point A can be determined as the intersection of the light beam T ₃ from the reflection point A to the image point i. .

FIG. 4 shows the processing procedure. After the image input 31, images I ₁ and I ₂ of the ray trajectory T ₄ passing through the red filter 25 and the ray trajectory T ₅ passing through the blue filter 26 are created. (32) Next, determine the position p ₁ on the pattern plate corresponding to each image point. p ₁ is obtained as a distribution depending on each image point i. (33) In the same manner, determine the position p ₂ on the pattern plate corresponding to each image point. (34) Subsequently, focusing on the fact that the light rays T ₄ and T ₅ whose image points coincide with each other become a common incident light beam T ₁ before the specular incidence, the processing results of 33 and 34 and the half mirror 23, mirror 24, and using the placement parameters of the pattern plate 22, and calculates an incident light beam T ₁ corresponding to each image point. (36) T ₁ is determined depending on each image point. On the other hand, the reflected ray T ₃ leading to each image point after reflection is calculated from camera parameters and the image point position. (35) Although the result of the corresponding position on the pattern plate is not used for calculation of the reflected light, in the figure, 33 and 35 are intentionally connected with a line in order to represent the reflected light for the image point i. Using the T ₁ and T ₃ obtained in this way, the position of the intersection A is calculated as a reflection point. (37) Also, the normal direction of the mirror surface 4 can be obtained at the same time.

In the figure, it is assumed that processing is performed for all image points in each step. However, the processing shown in the figure may be performed for each image point, and the processing may be repeated for each image point. In the embodiment, the red and blue filters are used, but it is obvious that other color combinations may be used. If the pattern plate 22 is displayed in a combination of a plurality of colors and the light rays T ₄ and T ₅ are configured to have different light colors, the color filters 25 and 26 may be omitted. Further, if the patterns of the pattern plate 22 are distinguished so that the light beams of T ₄ and T ₅ are temporally different, 25 and 26 are not necessary. Further, the configurations 23 and 24 may be realized by a prism optical element. The pattern plate 22 may be divided into two pattern plates, one of which is used for the light beam T ₄ and the other for the light beam T ₅ . In this case, instead of using the color filters 25 and 26, a color display pattern plate capable of emitting different colors can be used as the pattern plate, which simplifies the apparatus. Further, as long as they can be distinguished from light T ₄ and T ₅ by remembering the pattern structure in the pattern plate may be performed separation by features of the pattern structure in the image separation, in which case, the image input may use a black and white camera.

FIG. 5 shows a third embodiment. The pattern plates 2 and 3 are placed in a crossing direction. It does not necessarily have to be orthogonal. The pattern plate 2 displays a red pattern, and the pattern plate 3 displays a blue pattern. The light beam T ₄ exiting the pattern plate 2 passes through the half mirror 23 to become the incident light beam T ₁ , and the light beam T ₅ exiting the pattern plate 3 is reflected by the half mirror 23 to become T ₁ . By calculating the intersection of T ₁ and T ₃ , the position of the reflection point A and the normal direction of the mirror surface 4 can be obtained. However, in this case, in order to obtain the positions p1 and p2 on the pattern plates 2 and 3 corresponding to the respective image points, the camera uses the color camera 21 and separates the input image into a red component image and a blue component image, Corresponding as images from the pattern plate 2 and the pattern plate 3, respectively. The processing procedure is the same as that shown in FIG.

In this embodiment, the pattern plate may be a pattern plate in which a color filter is placed on the front surface instead of a color displayable pattern plate. The color camera may be a monochrome camera with a color filter on the front. In this embodiment, the combination of the colors of the pattern plates 2 and 3 is red and blue. However, a combination of other colors may be used. Further, a mirror can be provided between the half mirror 23 and the pattern plate 3 so that the direction of the pattern plate 3 can be freely changed. Further, if the pattern plates 2 and 3 are not switched at the same time so as to be switched temporally by a movable light shielding plate or a display lighting circuit, a monochrome camera may be used instead of the color camera.

In the first, second and third embodiments, a camera or a color camera is used, but the present invention is not necessarily limited to an optical camera. Further, what is simply described as a camera may be a monochrome camera or a color camera. Further, the target object surface does not need to be a perfect mirror surface, and may be a surface having a regular reflection component. However, in reality, measurement of a surface with strong diffuse reflection is often inaccurate due to low accuracy. In the description of the embodiments, the described virtual image of the pattern plate is a virtual image of the pattern displayed on the pattern plate.
[The invention's effect]
In order to obtain the position and shape of the mirror surface, it is necessary to detect the reflection point and the distribution in the normal direction of the mirror surface, but conventionally, there are restrictions on the measurement conditions and it has not been possible to detect stably. In the present invention, the method is based on the triangulation principle in which the incident light from the pattern plate and the reflected light on the mirror surface are obtained to calculate the intersection point, so that stable and high accuracy can be obtained. In this case, if the pattern plate is moved, there is a concern about mechanical accuracy deterioration. However, as a solution to this problem, a method that does not require movement of the pattern plate has been disclosed. Further, since the reflection point can be calculated for each image point, there is an advantage that the density of the measurement points can be increased. Further, since no information on the known position of the mirror surface is required at the time of measurement, the mirror surface position at an arbitrary image point can be detected without any information on the mirror surface position at the adjacent image point. For this reason, even when the mirror surface and the irregular reflection surface coexist, the mirror surface portion can be measured.

FIG. 1 is a diagram for explaining a first embodiment of the present invention.
[FIG. 2] shows a processing procedure in the first embodiment.
[FIG. 3] is a figure for demonstrating the 2nd Example of this invention.
[FIG. 4] shows a processing procedure in the second embodiment.
[FIG. 5] is a diagram for explaining a third embodiment.

Explanation of symbols

1: Camera 2, 3: Pattern plate 4: Mirror surface 11: Image input 12: Image-pattern association 13: Image input 14: Image-pattern association 15: Incident ray calculation 16: Reflected ray calculation 17: Reflection point Calculation 21: Color camera 22: Pattern plate 23: Half mirror 24: Mirror 25: Red filter 26: Blue filter 31: Image input 32: Image separation 33, 34: Image-pattern correspondence 35: Reflected ray calculation 36: Incident Ray calculation 37: Reflection point calculation

Claims (10)

One pattern board, means for moving the pattern board, image input means for observing a reflected image or virtual image of the pattern board to obtain an input image, and an image point of the input image and the pattern board Image-pattern correlation means for associating the upper pattern position with each other to obtain a corresponding position, incident light ray calculating means for calculating an incident light ray immediately before the incident of the reflection point, and reflected light ray traveling from the reflection point to the image point An object measuring apparatus comprising: a reflected light ray calculating means for calculating a reflection point; and a reflection point calculating means for calculating an intersection of the incident light ray and the reflected light ray as a reflection point An object measuring apparatus comprising at least two pattern plates and means for moving or rotating at least one of the pattern plates instead of the pattern plate and the pattern plate moving means according to claim 1. 2. The pattern plate according to claim 1, wherein at least two pattern plates are used instead of the pattern plate and the pattern plate moving means, and at least one of the pattern plates is a pattern plate capable of being transparent or translucent. Object measuring device At least two pattern plates, image input means for obtaining an input image by observing a reflection image or a virtual image of the pattern plate, a mirror for selecting a pattern plate to be observed when inputting the input image, and a mirror And an image-pattern association means for associating the image point of the input image with the pattern position on the pattern plate, and incidence for calculating the incident light beam immediately before the reflection point is incident A light ray calculating means; a reflected light ray calculating means for calculating a reflected light ray traveling from the reflection point to the image point; and a reflection point calculating means for calculating an intersection of the incident light ray and the reflected light ray as a reflection point. Object measuring device At least one pattern plate, a half mirror, and image input means for obtaining an input image by observing a reflected image or a virtual image of the pattern plate via the half mirror, and the image is a pattern plate or pattern plate Image separation means for separating an image corresponding to the inner region, image-pattern association means for associating an image point of the separated image with a pattern position on the pattern board, and an incident light beam immediately before the reflection point is incident. Incident light calculation means for calculating, reflected light calculation means for calculating a reflected light beam traveling from the reflection point to the image point, and a reflection point calculation means for calculating an intersection of the incident light beam and the reflected light beam as a reflection point Characteristic object measuring device 6. The object measuring apparatus according to claim 5, further comprising an optical path branching circuit in which a half mirror and a mirror are combined instead of the half mirror. 7. An object measuring apparatus according to claim 5, wherein a prism is used instead of a half mirror or a mirror. An object measuring apparatus comprising a movable light-shielding plate installed on the front surface of the pattern plate or a mechanism for turning on / off the pattern plate instead of the image separating means according to claim 5 or 6. 7. An object measuring apparatus according to claim 5, wherein the image separating means separates an image based on a pattern configuration characteristic of the pattern plate. 7. The image input means according to claim 5, wherein the image input means is an image input means provided with a color filter or a color-corresponding mechanism and capable of inputting a color image, and the pattern board displays a color arrangement or An object measuring device characterized in that it is a pattern plate with a color filter attached to the front surface, and the image separating means separates an input image using color features

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