CN101726257A - Multiple large range laser scanning measurement method - Google Patents

Abstract

The invention discloses a multi-eye wide-range laser scanning measurement method. Multi-eye cameras are arranged along the scanning line direction to jointly image a light knife in sections. By increasing the number of cameras, the overall field of view of the cameras is increased, thereby achieving improved scanning. purpose of efficiency. While the field of view of the camera increases, the length of the laser projection line is correspondingly lengthened so that the length of the laser scanning light knife meets the field of view requirements of the multi-eye camera. The method of the invention can double the efficiency of laser scanning without reducing the measurement accuracy.

Description

Multi-eye wide-range laser scanning measurement method

technical field

The invention relates to a method for measuring three-dimensional outline dimensions by laser scanning, in particular to a method for measuring outline dimensions by using multi-purpose large-scale laser scanning.

Background technique

With the in-depth development of extreme manufacturing technology, measurement technology under extreme conditions also emerges as the times require. In the process of manufacturing, assembling and testing large and super-large mechanical equipment, the measurement of its geometric dimensions and shape and position errors is the key factor to ensure the quality of the whole set of equipment. At present, the measurement of large-scale geometric quantities such as aircraft fuselages, ship hulls, and train carriages is mainly based on coordinate measurement technology. Under such measurement conditions, reasonable and effective terminal measurement methods and devices are the key to the system.

The main forms of measurement terminals currently used are trigger type, grating projection type and laser scanning type. Compared with the large and super-sized workpieces with a length of several meters or even tens of meters, the relative accuracy requirements are relatively high, but the absolute accuracy requirements are not too high, so the measurement efficiency is very important. The point trigger type only measures one point at a time, although its accuracy is high, but the efficiency is too low; the grating projection type has relatively high efficiency, but due to the long-distance optical imaging, its measurement accuracy is low due to the influence of the measurement environment, and It is difficult to apply in practice; there are many types of laser scanning methods, such as point scanning, single-light knife scanning, parallel multi-light knife scanning and cross-light knife scanning. The measurement principle adopted by laser scanning is generally the principle of optical triangulation, that is, the terminal coordinate information of each point on the contour surface of the measured workpiece relative to the measurement terminal is determined through the geometric relationship between the exit point, projection point and imaging, and then According to the position and attitude of the measurement terminal relative to the global measurement space, the position information of each point on the contour of the workpiece to be measured relative to the global measurement space is obtained.

In the point scanning method, the laser projection beam is a line beam, which forms a point when it is projected on the contour of the workpiece. This point can only be imaged as a point on the camera, that is, only one point can be measured for each sampling, which is obviously too low in efficiency. In the single-light knife scanning type, the laser projection beam is a plane beam, which is projected on the workpiece to form a straight line or curve, and the imaging on the camera is also a line, so it is called line scanning. Since each imaging is a line, its measurement efficiency is higher than that of The point scanning method is greatly improved. Assuming that the number of sampling points on each line is N, the sampling efficiency is N times higher than that of the point trigger and point scanning methods, but affected by the field of view of the camera, the range of the projection line of the scanning light knife being imaged by the camera is limited. No matter how long the light knife is, only a small section of the light knife can be used for imaging. In order to effectively utilize the field of view of the camera, multiple light knives can be scanned in parallel, or crossed light knives can be scanned. The former uses a group of lasers to project parallel beams onto the workpiece to be measured, forming multiple light knives to image and measure simultaneously. In principle, since there are multiple pieces of laser information in each measurement image, each image can process the cross-sectional profile information of multiple positions, so as to achieve the effect of high-speed measurement. However, due to the small distance between the optical knives, there is uncertainty in the accurate identification of different optical knives under certain conditions, and the efficiency of segmental scanning cannot be increased to a multiple of the number of optical knives. The sweep width of the cross light knife is the same as that of the single light knife, and it is the same as the single light knife in terms of its measurement efficiency.

Contents of the invention

Based on the in-depth study of laser scanning measurement technology, the present invention proposes a method for multi-eye combined large-scale laser scanning measurement in combination with the characteristics of large size and large surface curvature of the measured workpiece in large-size and super-large size measurement. , can increase the efficiency of laser scanning exponentially without reducing the measurement accuracy.

To achieve the above object, the present invention is achieved by taking the following technical solutions:

A multi-purpose wide-range laser scanning measurement method, comprising the following steps:

(1) A measurement terminal is adopted, including a frame, and a laser light knife projector is arranged on one side of the frame, which is used to project a plane beam to the workpiece and form a long projection line on the workpiece; on the other side of the frame, a Multi-eye digital cameras are arranged equidistantly along the direction of the long projection line, and are used for segmented imaging of the projection line; a real-time image processing and communication control center is set in the middle of the frame, which is used for real-time processing of the imaging information of the multi-eye digital cameras , to obtain the coordinate information of the point cloud of the workpiece contour on the projection line relative to the measurement terminal, and perform operation synchronization and information exchange with the global computer; multiple handheld mode positioning and attitude monitoring devices are arranged around the frame, Under the frame, there is an airborne mode fixing thread connected with the coordinate machine;

(2) Terminal scanning measurement calibration and terminal position and attitude calibration, wherein, in the airborne mode, the position T (X _T , Y _T , Z _T ) and attitude R (α, β, γ) of the terminal are calibrated by the three-coordinate measurement In the handheld mode, the positioning and attitude monitoring device on the terminal is only used as the target of the host computer, and its position and attitude information is given by the host computer; the terminal scanning measurement calibration is calibrated using the virtual grid mapping method;

(3) Measure the coordinates of any point P on the smooth knife line of the workpiece surface relative to the measuring terminal.

Let the center of the camera lens be point A, the position of the image sensor of the camera be at point C, the laser projector be at point B, the vertical line of the straight line AB be OD, perpendicular to the surface of the workpiece, so that the intersection point of the laser beam and the optical axis of the camera is located on the vertical line On the OD, therefore, the X-axis of the coordinate system established based on the measurement terminal is the DB direction, the Z-axis is the DO direction, and the Y-axis is the arrangement direction of the multi-eye digital camera. Let the length of AB be c, and the laser beam and the optical axis and The included angle of AB is β, the intersection point of the workpiece surface and the laser beam is P, and the imaging point of point P on the image sensor is P', and the displacement of P' from the optical axis center point O' on the image sensor is s , and the focal length of the lens is f, thus the coordinate position P _C (X _C , Y _C , Z _C ) of point P relative to the measurement terminal can be obtained, and its value is:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.5</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}$

in:

$\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; the\; tan</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; the\; s</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span>$

Assuming that the upper point P of the light-knife line is imaged on the i-th (i=0, 1, 2, 3, ...) camera image sensor, and the distance between the image point P' and the optical axis of the camera is v, then the point P is relative to the measured The Y coordinates of the terminal are:

${\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="ib"\; filenames="H2009102544305E00021.png"\; state="\{\{state\}\}">ib</figure-callout></span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; VC</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}{\sqrt{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="f"\; filenames="H2009102544305E00021.png"\; state="\{\{state\}\}">f</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="v"\; filenames="H2009102544305E00021.png"\; state="\{\{state\}\}">v</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}$

(4) Measure the coordinates of any point P on the light knife line of the workpiece surface in the global measurement space. Let the coordinates of point P in the global measurement space be P _G (X _G , Y _G , Z _G ), and its coordinates in the terminal coordinate system be P _C (X _C , Y _C , Z _C ), and the measurement terminal The coordinates in the global measurement space are T(X _T , Y _T , Z _T ), and the attitude angle is R(α, β, γ), then the coordinates of point P in the global measurement space can be used as its coordinates in the terminal After rotation and translation, _PG can be expressed as:

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}}\\ {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}}\\ {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; R</span>}\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}\\ {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}\\ {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}\end{array}\right]<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}& {\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}& {\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}& {\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}& {\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}\\ {\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}& {\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 7</span>}}& {\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}\end{array}\right]\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}\\ {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}\\ {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}\end{array}\right]<span\; class="notranslate">\; +</span>\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}\\ {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}\\ {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}\end{array}\right]$

Among them, R is the rotation matrix, which is the combination of trigonometric functions of the attitude angle (α, β, γ), T is the translation vector, which is the position of the origin of the terminal coordinate system in the global coordinate system, and the two data information are obtained by the three-coordinate measuring machine give.

In the above scheme, the virtual grid mapping method is to connect the measurement terminal to the three-coordinate automatic measuring machine, project the laser light knife of the terminal onto a standard plane, and use an auxiliary light knife to intersect with the terminal light knife to drive the three-coordinate measurement When the terminal light knife intersects with the auxiliary light knife at different X, Y, Z positions, the intersection points of the two light knives form a plane grid.

The multi-eye digital camera is triggered synchronously by the exposure time. According to the expected scan width b, the image sensitive area width of the image sensor is set to be w, and the length is kw. f, then it should satisfy the relation:

$\frac{\mathrm{<span\; class="notranslate">\; w</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; bCos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; c</span>}}$

Assuming that the number of pixels in the width direction is N, then the number of pixels in the length direction is kN, from which the theoretical resolution can be calculated as:

${\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; z</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; wl</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; wl</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="wc"\; filenames="H2009102544305E00021.png"\; state="\{\{state\}\}">wc</figure-callout></span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; NfCos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; .</span>$

The multi-eye digital camera adopts a fixed aperture and an electronic shutter to adjust the brightness of the laser light knife to ensure the imaging exposure and imaging quality.

The laser light knife properly adjusts the intensity of the laser beam projected by the laser through the real-time image processing and communication control center according to the gray scale change of the obtained image.

In the present invention, multiple cameras are arranged along the scanning line direction to jointly image a light knife, and by increasing the number of cameras, the overall field of view of the cameras is increased, thereby achieving the purpose of improving scanning efficiency. While the field of view of the camera increases, the length of the laser projection line is correspondingly lengthened so that the length of the laser scanning light knife meets the field of view requirements of the multi-eye camera.

Since the length of the scanning light knife of the present invention increases, the field of view of laser scanning increases, and a multi-eye camera is used to perform segmented imaging of the laser light knife. Since the imaging of the laser light knife by each camera in the multi-eye camera is independent, its accuracy is the same as that of the monocular camera. In addition, the field of view of each camera does not become smaller, and the scanning speed does not decrease. Therefore, Compared with the single-camera scanning method, its efficiency has been doubled, which is of great significance for improving the efficiency of large-scale, especially super-large-scale, three-dimensional contour measurement.

Large-scale equipment such as airplanes and ships have relatively simple shapes and slow shape changes, so the light knife curve formed when the laser beam is projected onto the contour has a large curvature and slow curvature change, which means using a longer light knife It is feasible to scan the line and use multi-eye cameras for segmented measurement without forming blind spots.

The invention is applicable in both airborne and handheld modes. In the airborne mode, the terminal can be installed on the coordinate measuring machine through the fixed thread on the terminal. Generally, the distance between the terminal and the computer is relatively short, and the video signal of the multi-camera can be directly connected to the computer for processing. In the handheld mode, the distance between the general terminal and the computer host is relatively long, and the transmission of the video image is seriously distorted. In addition, the movement is not stable in the handheld mode, and many shortcomings of video imaging cannot be compensated by obtaining the motion speed. Therefore, the video signal Real-time processing must be done on the terminal. The processed point cloud data traffic can be greatly reduced, and the point cloud data can be uploaded to the host computer through wireless communication. In the handheld mode, the coordinates of the point cloud data on the measured workpiece are relative to the terminal, and the position and attitude of the terminal change relative to the global measurement space. Therefore, it is necessary to determine the coordinates and attitude of the terminal in the global measurement space. Point cloud data can be converted into point cloud data of global measurement space coordinates through coordinate conversion. Coordinate conversion needs to be determined by configuring a global space positioning system on the terminal, and the method is to use a tracking device to scan the positioning and attitude monitoring device on the terminal to determine.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the measurement terminal of the present invention.

Fig. 2 is a principle diagram of the optical triangulation measurement of the measurement terminal of the present invention.

Fig. 3 is a schematic diagram of field segmentation of multi-eye cameras of the measurement terminal according to the present invention.

Detailed ways

1. Measuring terminal components.

As shown in Figure 1, the multi-eye wide-range laser scanning measurement terminal is mainly composed of five parts: laser light knife projector 5, multi-eye high-precision digital camera 1, real-time image processing and communication control center 3, handheld mode positioning and attitude monitoring device 6. The airborne mode is composed of a fixed thread 7 and a terminal frame.

The function of the laser light knife projector 5 is to project a plane light beam 4 to the workpiece. The projection line 8 formed on the workpiece is very long and the scanning width is very wide. Four-eye (four) digital cameras 1 are equidistantly arranged along the direction of the projection line 8, and image the projection line in segments to ensure that the width of the projection line is fully utilized, thereby improving measurement efficiency. The real-time image processing and communication control center 3 processes the imaging information of the four-eye digital camera 1 in real time to obtain the coordinate information of the point cloud of the workpiece contour on the projection line 8 relative to the measurement terminal, and synchronizes the operation with the global computer and exchange of information. There are two ways to obtain the position and attitude of the measurement terminal relative to the global measurement space: airborne mode and handheld mode. mode, it is obtained through three positioning and attitude monitoring devices 6 .

2. Measuring principle

The basic measurement principle of the invention is the principle of optical triangulation. The purpose of measurement is to obtain the coordinates of each point on the surface of the workpiece relative to the global measurement space. Since the global space coordinates and attitude of the measurement terminal can be obtained by the positioning system, it is only necessary to measure the coordinates of each point on the light knife line on the workpiece surface relative to the measurement terminal. That's it.

As shown in FIG. 2 , assume that the lens center of the camera 1 is at point A, the position of the image sensor is at point C, and the laser projector 5 is at point B. When scanning, it is hoped that the terminal working surface is as parallel as possible to the surface of the workpiece to avoid collisions. Therefore, the vertical line OD of the straight line AB should be perpendicular to the surface of the workpiece as much as possible. When designing, the intersection point of the laser beam and the optical axis of the camera is located on the vertical line OD. Therefore, the X-axis of the coordinate system established based on the measurement terminal is the DB direction, the Z-axis is the DO direction, and the Y-axis is the multi-eye digital Arrangement direction of cameras, the origin is point D. Let the length of AB be c, the angle between the laser beam and the optical axis and AB is β, the intersection point between the workpiece surface and the laser beam is P, and the imaging point of point P on the image sensor CCD is P', and the distance between P' and the image sensor is The displacement of the optical axis center point O' is s, and the focal length of the lens is f, so the coordinate position P _C (X _C , Y _C , Z _C ) of point P relative to the measurement terminal can be obtained, and its value is:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.5</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}$

in:

$\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; the\; tan</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; the\; s</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span>$

Assuming that the upper point P of the light knife line is imaged on the i-th (i=0, 1, 2, 3, ...) camera image sensor, and the distance between the image point P' and the optical axis of the camera is v, then the point P is relative to the measured The Y coordinate of the terminal is:

${\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="4"\; label="ib"\; filenames="H2009102544305E00021.png"\; state="\{\{state\}\}">ib</figure-callout></span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; VC</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}{\sqrt{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="f"\; filenames="H2009102544305E00021.png"\; state="\{\{state\}\}">f</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="v"\; filenames="H2009102544305E00021.png"\; state="\{\{state\}\}">v</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}$

It should be noted that Figures 2 and 3 are central perspective projection models, and the image distance is the same as the focal length, while for the lens imaging model, the image distance is greater than the focal length. In optical triangulation, since the object distance is relatively large, the image distance is relatively small. When the object distance is much larger than the image distance, the image distance can be considered to be equal to the focal length. For the present invention, the object distance range is about 100mm to 300mm, and the image distance is about 10mm. Therefore, it can be considered that the object distance is far greater than the image distance, and the image distance can be used to approximate the focal length in the formula, and the resulting Errors can be compensated for by system calibration.

3. Optical-mechanical design

Since the measurement principle of this device is based on machine vision measurement, its optical and mechanical structure must be precisely designed.

As shown in Figure 2, due to the fluctuation of the working surface and the distance between the measuring terminal and the workpiece during the movement, the distance X _P between the point P and the measuring terminal will change to a certain extent. for 2h. In the handheld mode, because the movement of the human hand is extremely unstable, and different operators have different habits, the depth of field design of the terminal must be large enough to reduce the requirements on the operator.

According to the expected scan width b (Fig. 3), select a suitable image sensor and lens, set the image sensitive area width of the image sensor as w, and the length as kw (commonly used aspect ratio factor k is 4/3), and the focal length of the lens is f, then it should satisfy the relation:

$\frac{\mathrm{<span\; class="notranslate">\; w</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; bCos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; c</span>}}$

Assuming that the number of pixels in the width direction is N, then the number of pixels in the length direction is kN, thus the theoretical resolution of the present invention can be calculated as:

${\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; z</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; wl</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; wl</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="wc"\; filenames="H2009102544305E00021.png"\; state="\{\{state\}\}">wc</figure-callout></span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; NfCos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; .</span>$

The above formula gives the theoretical resolution for design reference, and the accuracy of the actual device has many influences, mainly including the optical integration period of the camera, the lens aperture, and the target illuminance.

Since the scanning measurement is a motion measurement, the camera is constantly moving during the optical integration time of the camera, and the resulting imaging error is called smear, and the longer the optical integration time, the more serious the smear. In the airborne mode, the influence of smear can be reduced or even eliminated by ensuring the smoothness of the machine's moving speed and performing accurate calibration of the speed. However, in the handheld mode, due to the unstable motion speed, the accuracy cannot be compensated by speed calibration. Therefore, reducing the light integration time is an effective means to improve the measurement accuracy. In current camera image sensors, the light integration time of one frame of image is mainly affected by two factors: the illumination of the target to be measured and the aperture aperture of the lens. The higher the illuminance, the larger the aperture of the aperture, and the shorter the light integration time can be. For the acquisition of ordinary video images, since the target illumination is difficult to adjust, and the aperture adjustment is a mechanical adjustment, the speed is slow, so the method of changing the electronic shutter time is often used to adjust the exposure, so the electronic shutter time is the light integration time. However, affected by the number of pixels of the image sensor and the speed of the image processor, the shortest period of the electronic shutter is limited. The method for determining the electronic shutter time in the present invention is: by calculating the size of the field of view and the measurement accuracy, selecting an image sensor with an appropriate amount of pixels, and determining and fixing the electronic shutter time through a processor speed experiment to make it the shortest, so as to reduce image dragging. influence on the measurement accuracy.

The lens aperture adjustment is a mechanical adjustment, which is slow, easy to wear, and difficult to guarantee long-term stability. In addition, the adjustment of the aperture will cause the depth of field of the camera to change, thereby affecting the measurement range and accuracy. Therefore the present invention adopts the mode of fixed aperture. At the same time, try to reduce the aperture of the aperture as much as possible, which can increase the depth of field and improve the clarity of the image.

Since the lens aperture and the electronic shutter are fixed, but the exposure has to be adjusted, the present invention uses a laser with adjustable brightness, and the real-time image processing and communication control center can adjust the intensity of the laser beam projected by the laser according to the brightness change of the obtained image. Make appropriate adjustments.

It must be pointed out that the exposure time of the camera is relatively long, and it is difficult to guarantee the stability of the camera movement. If the exposure time of each camera is not synchronized and the exposure time is not equal, it will inevitably lead to the position and location of the image formed on the image sensor. Inconsistent quality. Assuming that the longest exposure time is the frame period and the camera frame rate is 25, then the exposure time is 40ms, and the scanning speed is 10mm/s, then the maximum error caused by frame asynchrony can reach 0.4mm. Obviously, such an error is unacceptable for precise measurement. For this, the exposure times of the cameras must be synchronized. In the present invention, the exposure time of each camera is the same, and an external trigger is used for synchronous exposure.

4. System Calibration

The coordinates of the intersection point P of the workpiece surface and the laser beam in the global measurement space are P _G (X _G , Y _G , Z _G ), and the coordinates in the terminal coordinate system are P _C (X _C , Y _C , Z _C ), And the coordinates of the measurement terminal in the global measurement space are T(X _T , Y _T , Z _T ), and the attitude angle is R(α, β, γ), then the global coordinates of point P can be used in the terminal The coordinates are obtained by rotation and translation, that is, PG can be expressed as:

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}}\\ {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}}\\ {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; R</span>}\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}\\ {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}\\ {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}\end{array}\right]<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}& {\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}& {\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}& {\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}& {\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}\\ {\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 6</span>}}& {\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 7</span>}}& {\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 8</span>}}\end{array}\right]\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}\\ {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}\\ {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}\end{array}\right]<span\; class="notranslate">\; +</span>\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}\\ {\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}\\ {\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}\end{array}\right]$

where R is the rotation matrix which is a trigonometric combination of attitude angles (α, β, γ). T is the translation vector, which is the position of the origin of the terminal coordinate system in the global coordinate system.

The measurement accuracy of optical camera measurement mainly depends on the imaging accuracy, but due to the principle error of optical imaging of camera measurement, nonlinear quantization error of image digitization, and various errors generated by the optical system during processing and installation, the ideal model and the actual The situation varies greatly. In addition, as the system is used in different environments and time, the state of the system will also change, and its measurement accuracy will also be affected. Therefore, when the measurement accuracy is not high, the ideal model given in the measurement principle can be used directly, but for high-precision measurement, the ideal model can only be used as a design reference, and cannot be directly used to calculate the final result. In this way, the accurate actual mathematical model can only be fitted through the method of system calibration, so as to obtain accurate measurement results. It can be seen that system calibration is the premise and guarantee for the measurement system to achieve high-precision measurement.

System calibration is divided into terminal scanning measurement calibration and terminal position and attitude calibration. In the airborne mode (such as installed on a three-coordinate measuring machine), the position information T (X _T , Y _T , Z _T ) and attitude information R (α, β, γ) of the terminal are determined by the global measuring machine (three-coordinate measuring machine ) acquisition; in the handheld mode, the positioning and attitude monitoring device on the terminal is only used as the target of the host computer, and its position and attitude information is given by the host computer. Therefore, the terminal position and attitude calibration will not be described in detail here. There are many calibration methods for terminal scanning measurement, such as standard block calibration method, inclined plane calibration method, standard ball calibration method and grid calibration method, etc. The present invention uses virtual grid mapping calibration method. The method is to connect the measurement terminal to the three-coordinate automatic measuring machine, project the laser light knife of the terminal onto a standard plane, and use an auxiliary light knife to intersect the terminal light knife to drive the three-coordinate measurement at different X, Y, Z positions If the terminal light knife intersects with the auxiliary light knife, then the intersection points of the two light knives form a plane grid. Since the three-coordinate position is given by the coordinate measuring machine, its accuracy can be well guaranteed, so the accuracy of the plane grid can be guaranteed .

Let the image coordinates of the target surface of the camera be P′(u, v), and the coordinates of the grid points on the standard plane relative to the camera be P _C (X _C , Y _C , Z _C ), the mapping relationship between these two planes can be Represented by a square recursive polynomial of degree n:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}}$

${\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; Y</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}}$

${\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; Z</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; v</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}}$

Among them, each intersection point of the (u, v) coordinate system constitutes an M×N lattice on the CCD target surface. The error functions EX, EY and EZ of X _C , Y _C and Z _C are:

${\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

${\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; Y</span>}}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Y</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; Y</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

${\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; Z</span>}}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; Z</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

a _ij , b _ij and c _ij can be given by the formula $\frac{\&PartialD;{\mathrm{E.}}_x}{\&PartialD;a_{\mathrm{ij}}}=0,$ $\frac{\&PartialD;{\mathrm{E.}}_x}{\&PartialD;a_{\mathrm{ij}}}=0,$ $\frac{\&PartialD;{\mathrm{E.}}_z}{\&PartialD;c_{\mathrm{ij}}}=0$ Get it.

The above calibration is a comprehensive calibration of the camera’s image sensor, lens, laser light knife and depth of field measurement. After the calibration is completed, the coordinates of the point cloud data calculated by using the calibration results relative to the measurement terminal are accurate, and then according to the terminal given by the global computer The coordinates T(X _T , Y _T , Z _T ) and the attitude angle R(α, β, γ) of the coordinate transformation can determine the coordinates of any point on the measured workpiece relative to the global measurement space.

Claims (5)

1. a multiple large range laser scanning measurement method is characterized in that, comprises the steps:

(1) adopt a kind of measuring terminals, comprise framework, a side is provided with a laser light knife projector on this framework, is used for to workpiece projection plane light beam, and forms the long incident line on workpiece; Opposite side is provided with many orders digital camera on this framework, equidistantly arranges along long incident line direction, is used for the incident line is segmented into picture; Be provided with realtime graphic handles and the Communication Control center in this framework midfield, be used for the image-forming information of many orders digital camera is handled in real time, obtaining the coordinate information of the some cloud of workpiece profile on the incident line with respect to measuring terminals, and and the global calculation machine between operate synchronously and information passes mutually; Be provided with a plurality of hand-held mode location and attitude monitoring device around on framework, below framework, be provided with the airborne pattern retaining thread that is connected with the coordinate machine;

(2) terminal scanning is measured and is demarcated and the demarcation of terminal location attitude, wherein, under airborne pattern, the position T (X of terminal _T, Y _T, Z _T) and attitude R (α, beta, gamma) demarcate and to obtain by three coordinate measuring machine; Under hand-held mode, location on the terminal and attitude monitoring device only use as the target of host computer, and its position and attitude information are provided by host computer; Terminal scanning is measured and is demarcated, and then uses the virtual grid reflection method to demarcate;

(3) on the measuring workpieces surface finishing tool line arbitrfary point P with respect to the coordinate of measuring terminals, if the optical center of video camera is the A point, the camera image sensor position is at the C point, laser projecting apparatus is at the B point, the perpendicular bisector of AB straight line is OD, vertical surface of the work, the intersection point of laser beam and camera optical axis is positioned on the perpendicular bisector OD, therefore, be that its X-axis of coordinate system that benchmark is set up is the DB direction with the measuring terminals, the Z axle is the DO direction, Y-axis then is the orientation of many orders digital camera, if AB length is c, the angle of laser beam and optical axis and AB is all β, and the intersection point of surface of the work and laser beam is P, and the imaging point of P point on imageing sensor is P ', the displacement of the optical axis center point O ' point of P ' on the imageing sensor is s, and the focal length of camera lens is f, can get the coordinate position P of P point with respect to measuring terminals thus _C(X _C, Y _C, Z _C), its value is:

$X_C=C\&CenterDot;(\frac{\mathrm{Cos}\left(\mathrm{\&alpha;}\right)\mathrm{Sin}\left(\mathrm{\&beta;}\right)}{\mathrm{Sin}(\mathrm{\&alpha;}+\mathrm{\&beta;})}-0.5)$

$Z_C=C\&CenterDot;\frac{\mathrm{Sin}\left(\mathrm{\&alpha;}\right)\mathrm{Sin}\left(\mathrm{\&beta;}\right)}{\mathrm{Sin}(\mathrm{\&alpha;}+\mathrm{\&beta;})}$

Wherein:

$\mathrm{\&alpha;}=\mathrm{\&beta;}-{\tan }^{-1}\left(\frac{s}{f}\right)$

If the finishing tool line go up a some P image in i (i=0,1,2,3 ...) on the individual camera image sensor, its picture point P ' is v apart from the camera optical axis distance, then the P point with respect to the Y of measuring terminals to coordinate is:

$Y_C=\frac{\mathrm{ib}}{4}+\frac{\mathrm{vcSin}\left(\mathrm{\&beta;}\right)}{\sqrt{f^2+v^2}\mathrm{Sin}(\mathrm{\&alpha;}+\mathrm{\&beta;})};$

(4) coordinate of arbitrfary point P in the global measuring space on the finishing tool line of measuring workpieces surface, establishing the coordinate of this P point in the global measuring space is P _G(X _G, Y _G, Z _G), its coordinate in end coordinates system is P _C(X _C, Y _C, Z _C), and the coordinate of measuring terminals in the global measuring space is T (X _T, Y _T, Z _T), attitude angle is R (α, a beta, gamma), then the coordinate of P point in the global measuring space can obtain through rotation and translation with its coordinate in terminal, i.e. P _GCan be expressed as:

$\left[\begin{array}{c}{X}_G\\ Y_G\\ Z_G\end{array}\right]=R\left[\begin{array}{c}{X}_C\\ Y_C\\ Z_C\end{array}\right]+T=\left[\begin{array}{ccc}{r}_0& r_1& r_2\\ r_3& r_4& r_5\\ r_6& r_7& r_8\end{array}\right]\left[\begin{array}{c}{X}_C\\ Y_C\\ Z_C\end{array}\right]+\left[\begin{array}{c}{X}_T\\ Y_T\\ Z_T\end{array}\right]$

Wherein R is a rotation matrix, and it is the trigonometric function combination of attitude angle (α, beta, gamma), and T is a translation vector, is that end coordinates is the position of initial point in global coordinate system, and two data messages are all provided by three coordinate measuring machine.

2. multiple large range laser scanning measurement method as claimed in claim 1, it is characterized in that, described virtual grid reflection method is that measuring terminals is fixed on the three-dimensional automatic measurement machine, the laser light knife of terminal projects on the standard flat, utilize an auxiliary finishing tool and terminal finishing tool to intersect in addition again, drive three-dimensional coordinates measurement terminal finishing tool and auxiliary finishing tool are intersected, then the joining of two finishing tools constitutes a plane grid.

3. multiple large range laser scanning measurement method as claimed in claim 1, it is characterized in that, described many orders digital camera, the time shutter synchronous triggering reaches sweep length b according to expection, and what establish imageing sensor is w as quick peak width, length is kw, k is that the Aspect Ratio coefficient generally is about 4/3, and lens focus is f, and then it should satisfy relational expression:

$\frac{w}{f}=\frac{\mathrm{bCos}\left(\mathrm{\&beta;}\right)}{2c}$

If pixel quantity is N on the Width, be kN then in length direction pixel quantity, can calculate theoretical resolution thus and be:

${\mathrm{\&Delta;}}_z=\frac{\mathrm{wl}}{\mathrm{kNf}}\mathrm{Sin}\left(\mathrm{\&beta;}\right)$

${\mathrm{\&Delta;}}_x=\frac{\mathrm{wl}}{\mathrm{kNf}}\mathrm{Cos}\left(\mathrm{\&beta;}\right)$

${\mathrm{\&Delta;}}_y=\frac{\mathrm{wc}}{2\mathrm{NfCos}\left(\mathrm{\&beta;}\right)}.$

4. multiple large range laser scanning measurement method as claimed in claim 1 is characterized in that, described many orders digital camera adopts fixed aperture and electronic shutter and the method for regulating laser light knife brightness guarantees the exposure and the image quality of imaging.

5. multiple large range laser scanning measurement method as claimed in claim 1, it is characterized in that, described laser light knife is handled and the grey scale change of Communication Control center according to the image that is obtained by realtime graphic, and the laser beam intensity of laser projections is suitably regulated.

Images