CN1570547A - Light pen type portable three dimensional coordinates measuring system - Google Patents

Abstract

This invention relates to an optical measuring technique of three-dimensional coordinates. The measuring system of optical pen-style portable three-dimensional coordinates comprises CCD camera, computer and optical pen used as measurement sensing part. There install three optical targets in the pen and a ball probe on the pen point. The centers of the three optical targets and the ball probe lie in the same line. The optical targets are obtained by the camera, which sends the image to computer, thus realizes the three-dimensional coordinates measuring of contact points through computer. The advantage of this invention lies in that it can flexibly adjust the camera position according to the traits of the object to be measured and facilitate the application on spot and increase the flexibility of the system.

Description

The portable three-dimensional coordinate measurement of light pen system

Technical field

The invention belongs to Measuring and Testing Technologies and Instruments, be specifically related to adopt method of optics to carry out the measuring technique of three-dimensional coordinate.

Technical background

The three-dimensional coordinate measurement device is widely used in multiple fields such as machinery, electronics, mould and Aero-Space as a kind of fine measuring instrument of practicality.Yet the present three-dimensional coordinate measurement device overwhelming majority all be with Cartesian coordinate be the basis, it has fixing work top, and three mutually perpendicular kinematic axiss and scale thereof etc. are set.For being used for the three-dimensional coordinate machine in workpiece processing field, the making more complicated of its line slideway and long scale, its base, worktable, column and guide rail are made by metal, granite or pottery usually, the general assembly (TW) of a three coordinate measuring machine reaches several tons and even tens of ton, so the manufacturing cost of coordinate measuring machine will rise with the increasing of range.Present in addition three coordinate measuring machine is all very heavy, the needs of incompatibility large-scale workpiece on-site rapid measurement.In recent years along with the progress of electronics and optical technology, the research that with the ccd video camera is the 3D vision detection system that constitutes of core component has obtained development faster, because optical detection is non-cpntact measurement, so be applicable to flexible and yielding workpiece are detected.But this type of pick-up unit installing and locating and demarcate comparatively complicatedly be mounted the batch detection that is suitable for behind the location same workpiece, but the occasion of measuring for the working-yard single-piece is unfavorable.For example, need measure the relative position of aircraft wing, at this moment the wing of huge heaviness can't be moved on the three coordinate measuring machine and be detected, the method that adopts can only have been constructed special-purpose coordinate system at engineering site at present.So in actual production and scientific research, more conditions need provide that a kind of installation is simple, easy operating, wide range, portable three-dimensional coordinate measurement device.Proposition of the present invention can make the problems referred to above obtain satisfactory solution.

Summary of the invention

In view of the above problems, the purpose of this invention is to provide a kind of portable three-dimensional coordinate measurement of light pen system for on-the-spot quick establishment.

The present invention realizes by following technology and computing method.The portable three-dimensional coordinate measurement of light pen system mainly comprises ccd video camera 1 and computing machine 2, and measuring sensing element is light pen 3.Several light target marks are housed on light pen 3, spheric probe 4 are housed at the nib place of light pen.Light target mark on the light pen has at least three to be positioned at same straight line, and the center of spheric probe 4 is in this straight line, if also there are two above light target timestamps outside this straight line, the position of spheric probe 4 then can be determined arbitrarily.When all light target marks were all on a line, the center nature of gauge head 4 was on this straight line.Power supply 5 for light target mark usefulness is housed in light pen.Form image capturing system by the image pick-up card in ccd video camera 1, computing machine 2 and the computing machine, known control point (light target mark) in the system on the employing light pen 3 is as imageable target, contact with measured surface by nib gauge head 4, the image that is absorbed light pen glazing target by ccd video camera 1 reaches computing machine 2.The present invention utilizes space coordinate transformation and collinear three points perspective imaging principle to set up the nonlinear measurement equation of vision measurement system, by gauge head 4 and light pen 3 glazing targets the achieve a butt joint three-dimensional coordinate measurement of contact of allocation really.

Measure and calculate principle as shown in Figure 2: the centre of perspectivity with single camera is true origin O, and the imaging system optical axis direction is the Z axle, and the direction in length and breadth that is parallel to the CCD pixel is respectively Y-axis and X-axis, sets up unique coordinate system-camera coordinate system of measuring system.The A point is the center of light pen gauge head 4 among Fig. 2, and B, C, D are three light target marks on the light pen 3, replace with point in model.A, B, C, D are located on the same line, and its distance each other is known.B, C, D are b, c, d by desirable perspective transform imaging in image coordinate system.θ ₁, θ ₂Can try to achieve by the image coordinates of b, c, d.

By perspective projection transformation and parsing geometric theory, can get:

B, C, the D coordinates value that D is 3 can be obtained by following formula:

Utilize collinear condition can try to achieve the three-dimensional coordinate (x that A is ordered _A, y _A, z _A), be the 3 d space coordinate of measured point.

$\left[\begin{array}{c}{x}_A\\ y_A\\ z_A\end{array}\right]=\frac{1}{3}(\left[\begin{array}{c}{x}_B+x_C+x_D\\ y_B+y_C+y_D\\ z_B+z_C+z_D\end{array}\right]+\left[\begin{array}{ccc}{x}_C-x_D& x_B-x_D& x_B-x_C\\ y_C-y_D& y_B-y_D& y_B-y_C\\ z_C-z_D& z_B-z_D& z_B-z_C\end{array}\right]\·\left[\begin{array}{c}\mathrm{AB}/\mathrm{CD}\\ \mathrm{AC}/\mathrm{BD}\\ \mathrm{AD}/\mathrm{BC}\end{array}\right])$

Beneficial effect of the present invention and advantage are: (1) can dynamically provide the xyz three-dimensional coordinate of any measuring point in space in the measurement range, can finish the measurement of size and shape error of single geometric element and the multiple functions such as measured position error of correlating factor.(2) quality of whole measuring system is about 20kg, is convenient to carry outside outdoor or carries out in-site measurement in the location of certain large-scale workpiece.(3) the measurement space scope reaches meter level, and measuring accuracy reaches the 0.1mm level.Therefore also can be used as the measurement of large-scale three dimensional curved surfaces such as body of a motor car, spacecraft housing.(4) do not need strict accurate installing and locating between light pen, video camera and the testee three, therefore can adjust the position of video camera flexibly, greatly facilitate on-the-spot the use, strengthened the flexibility of system according to the measured object characteristics.

Description of drawings

Accompanying drawing 1 is the portable three-dimensional coordinates measurement of a light pen system composition diagram.

Accompanying drawing 2 is the computation model figure of the portable three-dimensional coordinates measurement of light pen system.

Accompanying drawing 3 (a) (b) is respectively the front view and the side view of light pen.

Embodiment

Form portable three-dimensional coordinate measurement system by ccd video camera 1, computing machine 2 and light pen 3.For present embodiment, light pen 3 employing carbon fiber materials are done the right cylinder into about 500mm length, and there is a battery case 5 its inside, adopts three light targets marks on light pen, and presses the position shown in Fig. 3 and install, be i.e. B as shown in Figure 2, C, D point.Present embodiment adopts light emitting diode to mark as light target, and diode series connection back is by power supply 5 power supplies.Light pen gauge head 4 is adjusted light target mark center and gauge head in installation process center point-blank.Ccd video camera 1, computing machine 2 and the image pick-up card that is inserted in the computing machine are formed image capturing system, measure preceding to the disposable in advance accurate demarcation of this image capturing system.During measurement, the tested point on the gauge head 4 contact objects at light pen nib place, the light target mark on the light pen 3 is luminous, make its light-emitting area front towards video camera, by the video camera transmission, when three light targets of computer screen appearance are marked complete picture, the ccd video camera lock image.B, C, 3 of D are b, c, d by desirable perspective transform imaging in image coordinate system.θ ₁, θ ₂Can try to achieve by the image coordinates of b, c, d.

By perspective projection transformation and parsing geometric theory, can get:

B, C, the D coordinates value that D is 3 can be obtained by following formula:

Utilize collinear condition can try to achieve the three-dimensional coordinate (x that A is ordered _A, y _A, z _A), be the 3 d space coordinate of measured point.

$\left[\begin{array}{c}{x}_A\\ y_A\\ z_A\end{array}\right]=\frac{1}{3}(\left[\begin{array}{c}{x}_B+x_C+x_D\\ y_B+y_C+y_D\\ z_B+z_C+z_D\end{array}\right]\left[\begin{array}{ccc}{x}_C-x_D& x_B-x_D& x_B-x_C\\ y_C-y_D& y_B-y_D& y_B-y_C\\ z_C-z_D& z_B-z_D& z_B-z_C\end{array}\right]\·\left[\begin{array}{c}\mathrm{AB}/\mathrm{CD}\\ \mathrm{AC}/\mathrm{BD}\\ \mathrm{AD}/\mathrm{BC}\end{array}\right])$

Obtain the three-dimensional coordinate of gauge head center in camera coordinate system, the i.e. three-dimensional coordinate of tested point by above-mentioned Flame Image Process and calculated with mathematical model.Behind the three-dimensional coordinate that collects some measuring points on the testee, obtain size, shape and the site error etc. of testee by the three-dimensional coordinates measurement software evaluation.

Claims (2)

1. the portable three-dimensional coordinate measurement of light pen system, mainly comprise ccd video camera (1) and computing machine (2), it is characterized in that measuring sensing element is light pen (3), several light target marks are housed on light pen (3), at the nib place of light pen spheric probe (4) is housed, light target mark on the light pen has at least three to be positioned at same straight line, the center of spheric probe (4) is in this straight line, outside this straight line, there are two above light target timestamps, the position of spheric probe (4) can be determined arbitrarily, reaches computing machine (2) by ccd video camera (1) picked-up light pen (3) light target target image.

2. according to the portable three-dimensional coordinate measurement of the described light pen of claim 1 system, it is characterized in that in described light pen (3), being equipped with power supply (5) for light target mark usefulness.

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