KR102248197B1 - Large reflector 3D surface shape measuring method by using Fringe Pattern Reflection Technique - Google Patents

Abstract

The present invention relates to a method of measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technique, and to a method of accurately measuring a three-dimensional surface of an object that reflects light, such as a mirror, using a structured light pattern.
The proposed structured light pattern reflection technique (fringe pattern reflection) can be used to measure the three-dimensional surface shape of a large reflective light collecting plate in a short time, and analyze the curvature, distortion, and light collection rate of the reflecting plate.

Description

Large reflector 3D surface shape measuring method by using Fringe Pattern Reflection Technique}

The present invention relates to a method of measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technology, and more particularly, to a method of accurately measuring a three-dimensional surface of an object that reflects light, such as a mirror, using a structured light pattern. For.

The three-dimensional surface shape measurement technology is being used in the measurement technology of precision parts in industrial sites as the precision, resolution and reliability of equipment increase. In particular, 3D vision systems using optical technology in automated systems have begun to gain attention because they can obtain distance information or shape information about an object, and are usefully applied in automatic inspection systems that detect surface inspections or defects of semiconductors. Has become.

This three-dimensional surface shape measurement technology initially confirmed the surface shape by contacting the object surface through a contact sensor. However, this has a disadvantage in that the speed is slow, it is difficult to apply it to a large area locally, and it cannot be used in an area that can damage the surface even with a small pressure. Since then, optical-based non-contact technologies such as optical triangulation, confocal microscopes, optical interferometers, and near-field optical microscopes have been developing in various ways depending on the measurement precision, measurement time, and characteristics of the object to be measured.

Optical non-contacting 3-D Profile Measurement Method varies depending on the characteristics and types of light such as laser line scan method, holography, spherography, electronic speckle interferometer, and Moire method. Recently, the structured light pattern reflection technique (Fringe Pattern Reflection Technique), which obtains shape information by projecting a light pattern pattern, is representative.

Structured light pattern reflection technology projects a structured light pattern displayed on a monitor onto an object to be measured, and acquires a pattern deformed according to the shape of the object through a camera, and determines the surface height and inclination of the object through a series of tilt extraction processes. This is how to check.

Recently, in order to collect solar heat for efficient use of solar energy, a large mirror-type condensing reflector in the form of a parabolic cylinder is used. However, as the reflective light collecting plate increases in size, distortion such as warpage due to its own weight or tightening of bolts and nuts occurs, and the light collecting efficiency decreases. Therefore, it is necessary to optimize the curvature of the condensing reflector by measuring the three-dimensional surface of the manufactured large condensing reflector. To this end, the laser line scan method is used to measure the condensing reflector, and although it has the advantage of being able to measure precisely, there is a problem that it takes very long time to measure a large object.

An object of the present invention is a structure to measure the three-dimensional surface shape of a large reflective light collecting plate in a short time using the proposed fringe pattern reflection method, and to analyze the curvature, distortion, and light collection rate of the reflecting plate. It is to provide a method of measuring a three-dimensional surface shape of a large reflector using a light pattern reflection technology.

The object of the present invention is not limited to the objects mentioned above, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

According to one aspect for achieving this purpose, (a) a process of calibrating the camera by arranging a flat mirror so that the structured light pattern displayed on the projector screen appears on the flat mirror, and the process of correcting the geometry of the screen and the flat mirror. , A setup step of performing a process of recording the reference address of the structured light pattern; And (b) arranging a large reflector to be measured instead of the flat mirror, and reflecting from the reflector based on the reference address of the screen corresponding to the plane mirror and the external variable matrices of the screen and the structured light pattern obtained in the geometric correction process of the setup step. And a measuring step of measuring the modified structured light pattern.

Preferably, in the setup step, the projector is arranged so that the structured light pattern can be illuminated on the screen, the flat mirror is arranged so that the structured light pattern displayed on the screen appears on the flat mirror, and the environment is arranged so that the camera can photograph the flat mirror. After construction, the camera corrects the camera calibration process, the geometric correction process for the flat mirror and the screen, and the structured light pattern that appears on the flat mirror is captured by the camera, based on the three-dimensional position coordinates of the screen corresponding to the position coordinates of each pixel of the structured light pattern image. Perform the process of registering by address.

Preferably, in the measurement step, a large reflector to be measured is placed instead of a flat mirror, and based on the reference address of the screen corresponding to the planar mirror and the external variable matrices of the screen and the structured light pattern obtained in the geometric correction process of the setup step. The three-dimensional surface shape of a large reflector that calculates the local tilt of the reflector by measuring the reflected deformed structured light pattern is measured.

In addition, the setup step preferably includes: a camera correction step of obtaining a relationship between distortion correction that may appear in the camera and an image coordinate obtained from the camera and a three-dimensional camera coordinate based on the camera focus; A geometric correction step of obtaining an external variable matrix (rotation matrix and movement vector) capable of obtaining the three-dimensional coordinates of the plane mirror and the three-dimensional coordinates of the screen corresponding to the pixel coordinates of the image acquired from the camera; And the structured light pattern projected on the screen by the projector is projected onto a flat mirror and then photographed by the camera, and the three-dimensional position coordinates of the screen corresponding to the position coordinates of each pixel of the structured light pattern image are registered as a reference address. And setting up a three-dimensional surface shape measurement of a large reflector.

Preferably, the geometric correction process is performed by projecting a screen with a specific pattern, such as a checker board with a predetermined standard, from the projector to the screen during the setup step of measuring the three-dimensional surface shape of a large reflector, and the camera photographs a checkerboard reflected from a flat mirror, and The external variable matrix (rotation matrix and motion vector) for screen) is obtained using Equation 4.

(Equation 4)

와

는 가상 스크린에 대한 외부변수,

는 회전행렬,

는 이동벡터를 의미한다.Where n is the normal vector of the plane mirror, d is the distance from the camera origin to the mirror, and I is the unit matrix,

Wow

Is an external variable to the virtual screen,

Is the rotation matrix,

Means a motion vector.

Preferably, the process of recording the reference address of the structured light pattern is the decoded horizontal/vertical data obtained from the camera in a three-dimensional coordinate system with the camera as the origin for the decoded horizontal/vertical structured light pattern after geometric correction for the camera-planar mirror-screen. A reference address is registered for a three-dimensional position coordinate value of the screen corresponding to the position coordinate of each pixel of the structured light pattern image.

And, preferably, the measuring step uses the reference address of the screen corresponding to each pixel value of the deformed structured light pattern image obtained by photographing the reflector with a camera and the external variable matrices of the screen and the flat mirror obtained in the geometric correction process of the setup step. After obtaining the input light vector i and the output light vector r corresponding to each pixel value of the structured light pattern image, a normal vector is obtained according to Equation 5, and a local slope of the reflector is calculated using Equation 7.

(Equation 5)

(Equation 7)

: 평면거울 좌표,

: 반사체 표면의 높이,

: 스크린 좌표,

: 영상 좌표,

: 평면거울과 카메라의 거리,

: 거울과 스크린의 거리 i : input light vector in planar mirror coordinate M, r : output light vector in planar mirror coordinate M, n : normal vector in planar mirror coordinate M,

: Plane mirror coordinates,

: Height of reflector surface,

: Screen coordinates,

: Image coordinates,

: Distance between the flat mirror and the camera,

: Distance between mirror and screen

According to the method for measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technique according to the present invention, a three-dimensional surface shape of a large reflective light collecting plate is measured in a short time using the proposed structured light pattern reflection technique (fringe pattern reflection). And, it is possible to perform analysis of the curvature, distortion, and light collection rate of the reflector. In addition, it is possible to accurately and quickly measure the three-dimensional shape of the surface of automobiles, aircraft, and ships. Therefore, since it is possible to accurately measure the surface of a large object made of a material that reflects light produced through mold-injection, it can be used for verification of mold-injection products.

1 is an exemplary view showing a measurement environment in a method of measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technique according to an embodiment of the present invention.
2 is an exemplary view showing a step of measuring a 3D surface shape in a method for measuring a 3D surface shape of a large reflector using a structured light pattern reflection technique according to an embodiment of the present invention.
3 is an exemplary view showing a geometric correction process of a camera-planar mirror-monitor configuration using a virtual screen concept in a method of measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technique according to an embodiment of the present invention.
4 is a view showing some examples of structured light patterns reflected on a flat mirror in a method for measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technique according to an embodiment of the present invention.
5 is an exemplary view showing a structured light pattern decoded in a method of measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technique according to an embodiment of the present invention.
FIG. 6 is an exemplary view showing inclination measurement of a surface shape of a reflector by a structured light pattern reflection technique in a method of measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technique according to an embodiment of the present invention.
7 is an exemplary view showing some examples of a structured light pattern reflected on a light collecting reflector in a method for measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technique according to an embodiment of the present invention.
8 is an exemplary view showing a result of decoding a structured light pattern reflected on a light collecting reflector in a method for measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technique according to an embodiment of the present invention.
9 is an exemplary view showing a result of measuring the inclination of a light collecting reflector in a method of measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technique according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings and the following description. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed contents may be thorough and complete, and the spirit of the present invention may be sufficiently conveyed to those skilled in the art. The same reference numbers throughout the specification indicate the same elements. Meanwhile, terms used in the present specification are for describing exemplary embodiments and are not intended to limit the present invention. In this specification, the singular form also includes the plural form unless specifically stated in the phrase. As used herein, "comprises" and/or "comprising" refers to the presence of one or more other components, steps, actions and/or elements in which the recited component, step, operation and/or element is Or does not preclude additions.

Hereinafter, a system and method for driving a moving body according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In the case of a three-dimensional surface measurement method using structured light pattern reflection technology, a three-dimensional shape is measured by projecting a pattern through a monitor and receiving the reflected pattern transformed by a reflective object into a camera and calculating the surface height of the object to be measured. In general, in the case of a small reflective object, a three-dimensional surface shape can be measured by projecting a structured light pattern on the entire reflector using a monitor, but it is difficult to measure when the size of the reflector is larger than that of the monitor. Accordingly, in a method of measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technology according to an embodiment of the present invention, a structured light pattern reflection technology for measuring the surface of a large reflector is proposed.

In the case of a three-dimensional surface measurement method using the existing structured light pattern reflection technology, a small reflector is usually measured, so the measurement environment is composed of a ``monitor-measurement object-camera'' as shown in Fig.1 (a), but the object to be measured is a large reflector In the case of, it is difficult to measure the surface shape of a large reflector because the structured light pattern displayed on a small monitor does not illuminate the entire reflector but only a part of it.

Therefore, in this embodiment, in order to illuminate the entire large reflector, a measurement environment is constructed with a "projector-screen-measurement object-camera" that uses a projector and a large screen as shown in (b) of FIG. 1 without using a monitor. . The structure changed according to the surface curvature of the reflector by projecting a structured light pattern from the projector to a large screen through this environment, illuminating the structured light pattern displayed on the large screen to the reflector, and photographing the structured light pattern reflected from the reflector with a camera. By analyzing the degree of deformation of the light pattern, the three-dimensional surface shape of the reflector is measured.

The 3D shape measurement method using the proposed structured light pattern reflection technique performs the same steps as in FIG. 2. First, camera calibration is performed to obtain the camera's internal variables and corrects the camera's own inherent distortion (radiation distortion, tangential distortion, etc.). Then, by performing geometric calibration, an external variable indicating the relative position between “camera-plane mirror-screen” is obtained. The camera external variable is a variable representing the transformation relationship between the camera coordinate system and the world coordinate system, and is a variable related to the external space such as rotation, translation, or the position and direction of the camera between the two coordinate systems. In order to obtain the external variable of the camera, it can be obtained as a matrix that performs rotation transformation and movement transformation through matching of the 3D world coordinate system and 2D image coordinates sampled while the internal variable is obtained. The geometric correction steps are as follows.

① 2D image-3D camera coordinate transformation matrix calculation: Calculate the transformation relationship between the coordinate system of the 2D image captured by the camera and the coordinate system of the 3D camera. Through this process, a 3D coordinate value in the camera coordinate system corresponding to the position of each pixel of the 2D image may be obtained.

② Calculation of camera-plane mirror conversion matrix: Using a plane mirror, the camera coordinate system is used as the reference coordinate, and the conversion relationship that can calculate the coordinate value on the plane mirror is calculated. Using the transformation relationship obtained in ① and the transformation relationship obtained through this process, the 3D coordinate value of the image appearing in the plane mirror corresponding to the position of each pixel of the 2D image can be obtained when the image displayed in the plane mirror is photographed with a camera. I can.

③ Calculation of camera-screen transformation matrix: Calculate the transformation relationship to obtain the three-dimensional spatial coordinates of pixels displayed on the screen using the camera coordinate system as the reference coordinate. However, since the screen faces the same direction as the camera, since the camera cannot directly see the screen, it does not directly correct the geometry of the screen, and uses a virtual screen method that measures and corrects the screen screen reflected by a flat mirror.

Meanwhile, the structured light pattern generated by a computer is projected through a projector and displayed on a large screen. The reference address corresponding to the three-dimensional spatial coordinates of the structured light pattern displayed on the screen is measured using a flat mirror and recorded in memory. do. Finally, the reflector to be measured is placed at the position of the plane mirror, and the three-dimensional shape of the reflector is measured using the internal and external variables obtained in the process of camera calibration and geometric correction, and the registered structured light pattern address information.

A method of measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technique according to an embodiment of the present invention relates to a method of accurately measuring a three-dimensional surface of an object that reflects light, such as a mirror, using a structured light pattern. . In particular, according to the present embodiment, it can be applied to precise measurement of a large reflective light collecting plate that collects sunlight or a large object surface that reflects light well, such as a surface of a car, ship, or airplane.

In the case of the three-dimensional surface measurement method using the existing structured light pattern reflection technology, only a small reflector was measured, but in this embodiment, the three-dimensional surface shape of a large reflector was measured in a short time, and the curvature, distortion, and light collection rate of the reflector were analyzed. You can do it. Therefore, it is possible to accurately and quickly measure the three-dimensional surface shape of large reflectors such as large light collecting plates, automobiles, aircraft, and ship surfaces.

In a method of measuring a 3D surface shape of a large reflector using a structured light pattern reflection technique proposed in an embodiment of the present invention, a method of measuring a 3D surface shape of a large reflector may be divided into a setup step and a measurement step.

First, in the setup stage, the basic parameters of the 3D surface shape measurement using a planar mirror are determined. As shown in Fig. 3, the environment of the setup stage is arranged so that the structured light pattern can be illuminated on the screen from the projector, the flat mirror is placed so that the structured light pattern displayed on the screen appears on the flat mirror, and the camera Arrange it so that you can shoot.

In the setup step, first, through camera correction, the relationship between the distortion correction that may appear from the camera and the image coordinate obtained from the camera and the coordinates of the 3D camera based on the camera focus is obtained. Thereafter, a geometric correction process is performed. In the geometric correction, a matrix of external variables of the plane mirror and the screen is obtained based on the camera coordinates. For geometric correction for a flat mirror, attach a specific pattern (checkerboard pattern, etc.) with a predetermined standard to the flat mirror and shoot with a calibrated camera to create a matrix of external variables (rotation matrix and movement vector) for the flat mirror based on the camera coordinates. Seek. In addition, for the geometric correction of the screen, a specific pattern screen with a predetermined standard is projected from the projector to the screen, and the camera photographs the pattern reflected from the flat mirror to obtain a matrix of external variables (rotation matrix and motion vector) for the screen. Through this geometric correction process, the three-dimensional coordinates of the plane mirror and the three-dimensional coordinates of the screen corresponding to the pixel coordinates of the image acquired from the camera can be obtained. Finally, the structured light pattern is projected on the screen from the projector, and the camera photographs the structured light pattern that appears on the flat mirror, and the three-dimensional position coordinates of the screen corresponding to the positional coordinates of each pixel of the structured light pattern image are used as a reference address. ) To register.

In the measurement step, a large reflector to be measured is placed instead of a flat mirror, and the reflected from the reflector is based on the reference address of the screen corresponding to the plane mirror and external variable matrices of the screen and the structured light pattern obtained in the geometric correction process of the setup step. By measuring the modified structured light pattern, the local inclination of the reflector is measured. Then, the three-dimensional shape of the reflector is restored using an integration process or a model-based estimation method of the local slope of the reflector.

Camera correction, geometric correction, structured light pattern generation, a method of registering three-dimensional coordinates (reference address) of a structured light pattern displayed on a screen, and a method of measuring a local inclination of a large reflector used in an embodiment of the present invention are as follows.

(Camera calibration)

First, camera calibration will be described as follows. The camera image can be obtained by projecting points in a three-dimensional space onto a two-dimensional image plane (Perspective Projection). The camera calibration process informs the geometric model of the camera and the distortion model of the lens, and determines the relationship between the points in the 3D space and the pixels of the 2D image plane. Camera calibration is a process necessary to determine the relationship between points on a 3D space and pixels on a 2D image plane and use it as a computer vision. In general, the camera correction method used is in the order of shooting a chessboard, extracting corners from the captured image, minimizing the error value of corner extraction through optimization, obtaining correction parameters, and obtaining non-distorted images based on the parameters. Proceeds to

The relationship between the image coordinate obtained through camera correction, the camera coordinate, and the world coordinate is shown in Equation 1.

[Equation 1]

는 영상의 화소 위치 (x,y)에 대응하는 카메라 좌표계의 3차원 좌표이고, (X,Y)는 월드좌표계에서의 3차원 좌표이다. [R T]는 월드 좌표계를 카메라 좌표계로 변환시키기 위한 회전/이동 변환 행렬이다. Where s is the scale factor, A is the camera internal variable matrix,

Is the 3D coordinate of the camera coordinate system corresponding to the pixel position (x,y) of the image, and (X,Y) is the 3D coordinate in the world coordinate system. [RT] is a rotation/movement transformation matrix for converting the world coordinate system to the camera coordinate system.

를 구할 수 있다.If the G matrix is defined as Equation 2 and Equation 1 is applied, all pixel coordinates (x,y) of all captured images can be converted into 3D coordinates of the camera coordinate system by Equation 3. In the end, 3D camera coordinates for image coordinates (x, y) by Equation 3

Can be obtained.

[Equation 2]

[Equation 3]

(Geometric correction)

The geometric correction between'camera-flat mirror-screen' using a virtual screen will be described. A method of measuring a three-dimensional shape of a large reflector using the structured light pattern reflection technique presented in the present invention is as follows. The projector irradiates the structured light pattern onto the screen, and the structured light pattern of the screen is formed on the reflector, and the structured light pattern reflected from the reflector is deformed according to the surface shape of the reflector. By analyzing the relationship between the incident ray and the reflected ray using the modified structured light pattern information and the coordinate system conversion information between the screen-reflector-camera, the local surface slope of the reflector is calculated. Measure the three-dimensional surface shape. For this measurement, a reference coordinate for the reflector is required, and a plane mirror is used to set the reference coordinate for the reflector. In this way, the process of calculating the relationship of the coordinate system between the screen-plane mirror-camera is called geometric calibration.

3 shows a geometric correction process using the concept of a virtual screen. The input light i from the coordinate S of the screen is reflected from the coordinate M of the plane mirror, and the reflected light r passes through the camera origin to form an image on the image C. If the geometric correction is correct, you can know the world coordinates for the image coordinates, screen coordinates, and plane mirror coordinates. Therefore, when the input light vector i and the output light vector r are obtained, the normal vector n to the mirror coordinate M can be obtained, and thus the local slope at the coordinate M is obtained.

,

]을 계산하는 것이다. 이 과정을 통해 카메라와 평면거울 간의 좌표변환을 할 수 있게 되어 촬영된 영상의 각 화소 위치에 대응하는 평면거울의 3차원 좌표값을 계산할 수 있다. The geometric correction process for a flat mirror is to attach a checker board to the flat mirror and shoot with a calibrated camera, and the external variables [

,

]. Through this process, it is possible to convert the coordinates between the camera and the plane mirror, so that the three-dimensional coordinate value of the plane mirror corresponding to the position of each pixel of the photographed image can be calculated.

,

]을 계산한다. 그리고 스크린에 대한 실제 회전행렬과 이동벡터 [

,

]는 수학식 4를 이용하여 구한다. The geometric correction for the screen can also be performed in the same way as the geometric correction process for a flat mirror. However, since the screen faces the same direction as the camera, the camera cannot directly see the screen. Therefore, it is not possible to directly correct the geometry of the screen, but it is corrected using the screen screen reflected by the flat mirror. This concept is called a virtual screen. The geometric correction process using the concept of a virtual screen projects a checkerboard screen with a predetermined standard from the projector to the screen, and the camera shoots a checkerboard reflected from a flat mirror, and external variables [

,

] Is calculated. And the actual rotation matrix and motion vector for the screen [

,

] Is obtained using Equation 4.

[Equation 4]

와

는 가상 스크린에 대한 외부변수,

는 회전행렬,

는 이동벡터를 의미한다.Where n is the normal vector of the plane mirror, d is the distance from the camera origin to the mirror, and I is the unit matrix,

Wow

Is an external variable to the virtual screen,

Is the rotation matrix,

Means a motion vector.

(Structured light pattern creation and reference address registration)

The structured light pattern generation and reference address registration will be described as follows.

Recently, a three-dimensional surface measurement method using a structured light pattern is mainly used as a measurement method that simplifies the optical system while maintaining excellent measurement accuracy. 4 shows some bit patterns of a 10-bit gray-coded horizontal/vertical structured light pattern formed on a slightly tilted flat mirror, and FIG. 5 shows a decoded structured light pattern image.

In order to measure a three-dimensional surface shape using a structured light pattern, it is necessary to know a one-to-one correspondence between each pixel of a camera image photographing a structured light pattern reflected in a mirror and a screen pixel. Therefore, the screen corresponding to the position coordinates of each pixel of the decoded structured light pattern image acquired from the camera in the 3D coordinate system with the camera as the origin for the decoded horizontal/vertical structure pattern after geometric correction for the camera-plane mirror-screen. The three-dimensional position coordinates of are registered as a reference address and used in the process of measuring the surface shape of the reflector. The three-dimensional coordinate value of the screen corresponding to the decoded structure pattern value is registered in the reference address.

(Measurement of local inclination of reflector and restoration of 3D shape by structured light pattern reflection technology)

에서 나오는 입력 광 i는 평면거울의 좌표

에서 반사체에 반사되고, 반사광 r은 카메라 원점을 통과하여 영상

에 상을 맺는다. 기하 보정이 정확하면 영상 좌표에 대응하는 스크린과 평면 거울에 대한 3차원 좌표를 알 수 있다. 따라서 입력 광 벡터 i와 출력 광 벡터 r을 구할 수 있고, 좌표

에서의 반사체에 대한 법선벡터 n을 수학식 5로 구할 수 있다. 이때 2차원 영상좌표는 수학식 3 을 이용하여 3차원 카메라 좌표로 변환한다.6 shows the interrelationship of screen coordinates, plane mirror coordinates, and camera coordinates in the camera coordinate system. Screen coordinates

The input light i emitted from is the coordinates of the plane mirror

Is reflected by the reflector, and the reflected light r passes through the camera origin

The prize is on. If the geometric correction is accurate, the three-dimensional coordinates for the screen and the plane mirror corresponding to the image coordinates can be known. Therefore, the input light vector i and the output light vector r can be obtained , and the coordinates

The normal vector n for the reflector at can be obtained by Equation 5. At this time, the 2D image coordinates are converted into 3D camera coordinates using Equation 3.

(Equation 5)

i : input light vector in planar mirror coordinate M, r : output light vector in planar mirror coordinate M, n : normal vector in planar mirror coordinate M

) 좌표에서 반사체 표면의 수평, 수직방향 기울기는 수학식 6으로 계산된다.And (

) In the coordinates, the horizontal and vertical slope of the reflector surface is calculated by Equation 6.

(Equation 6)

)에서 반사체 표면의 높이는

로 나타낼 수 있으므로 수학식 6의 기울기는 수학식 7로 표현할 수 있다.Plane mirror coordinates (

), the height of the reflector surface is

Since it can be expressed as Equation 6, the slope of Equation 6 can be expressed as Equation 7.

(Equation 7)

는 거울과 카메라의 거리,

는 거울과 스크린의 거리이다. 그리고

,

,

,

,

는 기하학적으로 구할 수 있다. 한편

,

,

는 구조광 패턴 편향 측정을 통해 구한다. here

Is the distance between the mirror and the camera,

Is the distance between the mirror and the screen. And

,

,

,

,

Can be obtained geometrically. Meanwhile

,

,

Is obtained by measuring the deflection of the structured light pattern.

,

) 좌표에서 반사체에 나타난 구조광 패턴 값에 대응하는 3차원 스크린 좌표를 구하면

,

,

을 계산할 수 있다. 하지만 식 (7)에서

은 3차원 복원과정에서 반복적인 연산을 통해 구해지는 값이데, 초기값으로 평면거울의

을 적용하여 계산한다. The structural pattern shown on the reflector has a deformed pattern value compared to the flat mirror according to the surface shape.

,

) If you obtain the 3D screen coordinates corresponding to the structured light pattern value displayed on the reflector from the coordinates,

,

,

Can be calculated. But in equation (7)

Is a value obtained through repetitive operations in the 3D restoration process, and is the initial value of the flat mirror.

Calculate by applying.

,

) 좌표에서 반사판에 나타난 구조광 패턴 값에 대응하는 3차원 스크린 좌표를 구하면

,

,

을 계산할 수 있다. 하지만 식 (7)에서 반사판의 z(

,

)은 3차원 복원과정에서 반복적인 연산을 통해 구해지는 값이데, 초기값으로 평면거울의 높이

을 적용하여 계산한다. 3차원 형상복원은 기울기에 대한 integration 처리 또는 모델기반의 추정방식이 주로 사용된다.7 shows the fifth horizontal/vertical structured light pattern modified by the surface shape of the light collecting reflector, and FIG. 8 shows the decoded structure pattern. 9 shows the inclination of the light collecting reflector in the horizontal and vertical directions. The structured light pattern displayed on the condensing reflector has a pattern value different from the reference address registered using a flat mirror according to the surface shape.

,

) If you obtain the 3D screen coordinates corresponding to the structured light pattern value displayed on the reflector from the coordinates,

,

,

Can be calculated. But in equation (7), z(

,

) Is a value obtained through repetitive operations in the 3D restoration process, and is the initial value of the height of the flat mirror.

Calculate by applying. In 3D shape restoration, the integration process for the slope or model-based estimation method is mainly used.

The method of measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technology according to an embodiment of the present invention can accurately and quickly measure the three-dimensional shape of the surface of a large-sized light-converging reflector, automobile, aircraft, and ship. Therefore, since it is possible to accurately measure the surface of a large object made of a material that reflects light produced through mold-injection, it can be used for verification of mold-injection products.

,

,

) : 영상의 화소 위치 (x, y)에 대응하는 카메라 좌표계의 3차원 좌표, (X, Y) : 월드좌표계에서의 3차원 좌표, [R T] : 월드 좌표계를 카메라 좌표계로 변환시키기 위한 회전/이동 변환 행렬이다.In the method of measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technique according to an embodiment of the present invention, terms (symbols) will be described as follows. s: scale factor of the camera, A: matrix of camera internal variables, (

,

,

): 3D coordinates of the camera coordinate system corresponding to the pixel position (x, y) of the image, (X, Y): 3D coordinates in the world coordinate system, [RT]: Rotation to convert the world coordinate system to the camera coordinate system It is a shift transformation matrix.

: 스크린의 좌표,

: 카메라 좌표,

: 평면 거울의 좌표, i : 평면 거울좌표 M에서의 입력 광 벡터, r : 평면 거울좌표 M에서의 출력 광 벡터, n : 평면 거울좌표 M에서의 법선벡터(normal vector),

: 평면거울과 카메라의 거리,

: 거울과 스크린의 거리

: The coordinates of the screen,

: Camera coordinates,

: Coordinates of the plane mirror, i : input light vector in plane mirror coordinate M, r : output light vector in plane mirror coordinate M, n : normal vector in plane mirror coordinate M,

: Distance between the flat mirror and the camera,

: Distance between mirror and screen

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention within the scope not departing from the spirit and scope of the present invention described in the following claims. You will understand that you can.

Claims (7)

(a) The process of calibrating the camera by arranging the flat mirror so that the structured light pattern displayed on the large screen of the projector appears on the flat mirror, the geometric correction process for the large screen and the flat mirror, and the reference address of the structured light pattern. A setup step of performing a recording process; And
(b) Place a large reflector to be measured in place of the flat mirror, and the large reflector based on the reference address of the large screen corresponding to the plane mirror and the external variable matrices of the screen and the structured light pattern obtained in the geometric correction process of the setup step. Including; a measuring step of measuring the deformed structured light pattern reflected from the,
In the setup step, the projector is arranged so that the structured light pattern can be illuminated on the large screen, the flat mirror is arranged so that the structured light pattern displayed on the large screen appears on the flat mirror, and the flat mirror is arranged so that the camera can photograph the structured light pattern. Build the environment,
In the measuring step, the input light emitted from the coordinates (S) of the large screen is reflected from the coordinates (M) of the flat mirror, and the reflected light passes through the camera origin and is imaged to the camera coordinates (C). By obtaining the normal vector of the reflector at the coordinates (M) of the planar mirror, measuring the horizontal and vertical slope of the surface of the large reflector to measure the three-dimensional surface shape of the large reflector,
In the process of recording the reference address of the structured light pattern, an image projected on the flat mirror on which the structured light pattern of the large screen is corrected is photographed by a camera, and a three-dimensional coordinate value of the large screen corresponding to the structured pattern value is registered,
In the measuring step, the structured light pattern appearing on the large reflector to be measured is photographed with a camera and measured using a difference value from the reference address, but the structured light pattern appearing on the large reflector at plane mirror coordinates (Xm, Ym) Calculate the three-dimensional screen coordinates (Xs, Ys) and the mirror-large screen distance (dm2s) corresponding to the value, and apply the height of the flat mirror (Zm) as an initial value to the height of the large reflector surface (z=z A method for measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technique, characterized in that (Xm,Ym)) is calculated. The method of claim 1,
In the setup step, the projector is arranged so that the structured light pattern can be illuminated on the screen, the flat mirror is placed so that the structured light pattern displayed on the screen appears on the flat mirror, and the environment is constructed so that the camera can photograph the flat mirror. After the camera calibration process, the geometric correction process for the flat mirror and the screen, and the structured light pattern appearing on the flat mirror, the camera photographs the three-dimensional position coordinates of the screen corresponding to the position coordinates of each pixel of the structured light pattern image as a reference address. A method of measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technology, characterized in that performing a process of registering as. The method of claim 1,
In the measuring step, a large reflector to be measured is placed instead of a flat mirror, and reflected from the reflector based on the reference address of the screen corresponding to the plane mirror and external variable matrices of the screen and the structured light pattern obtained in the geometric correction process of the setup step. A method for measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technology, characterized in that measuring a modified structured light pattern to measure a three-dimensional surface shape of a large reflector that calculates a local inclination of the reflector. The method of claim 1,
The setup step includes: a camera correction step of obtaining a relationship between the distortion correction that may appear in the camera and the image coordinates obtained from the camera and the three-dimensional camera coordinates based on the camera focus;
A geometric correction step of obtaining an external variable matrix (rotation matrix and movement vector) capable of obtaining the three-dimensional coordinates of the plane mirror and the three-dimensional coordinates of the screen corresponding to the pixel coordinates of the image acquired from the camera; And
The structured light pattern projected on the screen by the projector is projected onto a flat mirror, and then photographed by the camera, and the three-dimensional position coordinates of the screen corresponding to the position coordinates of each pixel of the structured light pattern image are registered as a reference address. A method for measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technology, comprising the step of setting up a three-dimensional surface shape measurement of a reflector. The method of claim 1,
In the geometric correction process, during the setup step of measuring the three-dimensional surface shape of a large reflector, a screen with a specific pattern, such as a checkerboard with a predetermined standard, is projected from the projector to the screen, and the camera photographs the checkerboard reflected from the flat mirror, and A method for measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technique, characterized in that the external variable matrix (rotation matrix and motion vector) for) is obtained using Equation 4.
(Equation 4)

Where n is the normal vector of the plane mirror, d is the distance from the camera origin to the mirror, and I is the unit matrix,

Wow

Is an external variable to the virtual screen,

Is the rotation matrix,

Means a motion vector. The method of claim 1,
The process of recording the reference address of the structured light pattern is the decoded horizontal/vertical structure obtained from the camera in a three-dimensional coordinate system with the camera as the origin for the decoded horizontal/vertical structured light pattern after geometric correction for the camera-plane mirror-screen. A method of measuring a three-dimensional surface shape of a large reflector using a structured light pattern reflection technology, characterized in that a reference address is registered for a three-dimensional position coordinate value of a screen corresponding to the position coordinate of each pixel of the light pattern image. The method of claim 1,
The measuring step is the structured light using the reference address of the screen corresponding to each pixel value of the deformed structured light pattern image obtained by photographing the reflector with a camera and the external variable matrices of the screen and plane mirror obtained in the geometric correction process of the setup step. A structured light pattern, characterized in that the input light vector i and the output light vector r corresponding to each pixel value of the pattern image are obtained, the normal vector is calculated according to Equation 5, and the local slope of the reflector is calculated using Equation 7 Large reflector 3D surface shape measurement method using reflection technology.
(Equation 5)

(Equation 7)

i : input light vector in planar mirror coordinate M, r : output light vector in planar mirror coordinate M, n : normal vector in planar mirror coordinate M,

: Plane mirror coordinates,

: Height of reflector surface,

: Screen coordinates,

: Image coordinates,

: Distance between the flat mirror and the camera,

: Distance between mirror and screen

Images