CN112082477A - Universal tool microscope three-dimensional measuring device and method based on structured light - Google Patents

Abstract

The invention discloses a three-dimensional measuring device for a universal tool microscope based on structured light, comprising a universal tool microscope body, an image acquisition device, a structured light projection device, a synchronous drive device and a computer control and processing device. The structured light projection device projects structured light to The calibration surface and the workpiece surface to be tested, the structured light projection device and the image acquisition device are moved synchronously in the Z direction through the synchronous drive device, and the image acquisition device is controlled by the computer control and processing device to obtain the calibration and a series of images of the workpiece to be tested, and pass the pre- The algorithm is designed to process the collected images to realize 3D non-contact measurement; combined with digital photogrammetry and image processing technology, the universal tool microscope is simply transformed based on the principle of structured light measurement, which expands the application range of the original universal tool microscope, not only can achieve 3D Non-contact measurement of geometric dimension information can also detect information such as Z-axis shape errors and surface defects.

Description

Three-dimensional measurement device and method for universal tool microscope based on structured light

technical field

The invention relates to the field of photogrammetry, in particular to a three-dimensional measurement device and method for a universal tool microscope based on structured light.

Background technique

Universal tool microscope is a high-efficiency metrology optical instrument using grating subdivision and digital technology. It is easy to operate, intuitive to read, has high accuracy, and has stable performance. It is widely used in metrology and inspection work (see Duan Weifei, Mu Yajuan. Universal tool Basic principles and measurement methods of microscopes [J]. Value Engineering, 2018, 37(17): 239-240. And Shanghai Optical Instrument No. 5 Factory, 19JC Digital Universal Tool Microscope Instruction Manual.).

Using a universal tool microscope can easily measure the X-axis and Y-axis dimensions of the workpiece to be tested, but the Z-axis dimension cannot be measured. However, the research on the transformation of the universal tool microscope is still relatively lacking. Patent (Che Hong, Xu Qin, Zhu Lin, Li Shudong. Universal tool microscope measuring instrument [P]. CN203672316U, 2014-06-25.) In order to solve this problem, the main microscope is replaced with a dial indicator and the main microscope body is fixedly connected , perform contact measurement on the measured workpiece, but this method cannot perform 3D measurement at the same time, the main microscope needs to be replaced during the measurement process, the operation process is cumbersome, and the contact measurement range is limited, the probe is often worn, and the measurement accuracy is low.

Therefore, we modified the universal tool microscope based on the principle of structured light measurement, so that it can perform non-contact measurement of the geometric dimensions of the Z-axis on the basis of retaining the original non-contact measurement of the geometric dimensions of the X-axis and Y-axis, and Detection of information such as form errors and surface defects.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a three-dimensional measurement device and method for a universal tool microscope based on structured light, aiming at the deficiencies of the prior art. Combined with digital photogrammetry and image processing technology, the universal tool microscope is transformed based on structured light, so that it can simply and conveniently perform non-contact three-dimensional measurement and Z-axis shape error and surface defect detection. The method is simple to implement and easy to transform.

The technical scheme adopted in the present invention is as follows: a three-dimensional measuring device for a universal tool microscope based on structured light, comprising a universal tool microscope body, and the universal tool microscope body includes a base, a worktable, vertical and horizontal guide rails, an aiming microscope system and illumination system; the aiming microscope system includes an optical lens imaging system and a grating reading system; the measuring device also includes an image acquisition device, a structured light projection device, a synchronous drive device and a computer control and processing device, wherein:

The image acquisition device retains the optical lens imaging system and the grating reading system in the aiming microscope system of the universal tool microscope, and uses a CCD camera instead of the original eyepiece to collect the calibration image and the image information of the measured workpiece;

The structured light projection device includes a fiber laser and a conical refractor. The host LED illumination source in the universal tool microscope illumination system is transformed into a structured light projection device, and the original and the eyepiece of the aiming microscope system are kept synchronously moving in the X and Y directions. The structure of the structured light projection device, the laser beam emitted by the fiber laser in the structured light projection device is refracted by the conical refractor to form a conical structured light and projected to the blank light-transmitting plate. the device acquires the image;

The synchronous drive device includes a displacement sensor, a single-chip microcomputer, a driver, a stepping motor and a secondary gear. The displacement sensor is fixed on the Z-axis lifting arm to detect the moving distance of the CCD camera of the image acquisition device in the Z direction, and sends the information to the driver through the single-chip microcomputer. The pulse generator signal drives the stepping motor, and then drives the secondary gear to move the structured light projection device and the CCD camera of the image acquisition device synchronously in the Z direction;

The computer control and processing device controls the image acquisition device to acquire the calibration and the image of the workpiece to be tested, and processes the acquired images through a preset algorithm.

A three-dimensional measurement method of a universal tool microscope based on structured light, comprising:

Step 1. When using the modified universal tool microscope for the first time, it is necessary to calibrate the internal and external parameters of the camera and the parameters of the conical structured light.

Provide a blank transparent plate and a CCD camera for calibration only;

The angle between the optical axis of the calibration CCD camera and the CCD camera of the image acquisition device is less than 90°;

1) Calibration of camera internal and external parameters

The computer control and processing device controls the CCD camera of the image acquisition device and the calibration CCD camera to simultaneously shoot the calibration plate plane with uniform marking points;

Use the Zhang Zhengyou plane template calibration method to process the collected images, calibrate the CCD camera of the image acquisition device and the internal and external parameters of the CCD camera, and unify the external parameters of the two cameras into the same world coordinate system;

2) Calibration of conical structured light

Control the structured light projection device to project the conical structured light to the blank light-transmitting plate, and move the Z-axis lifting arm to focus the projected structured light on the blank light-transmitting plate;

The computer control and processing device controls the image acquisition device and the calibration CCD camera to obtain the corresponding halo calibration image projected by the structured light to the blank light-transmitting plate;

Detect and fit the halo inner edge of the halo calibration image to an elliptical halo image;

The fitted elliptical halo and the optical center of the CCD camera of the image acquisition device construct the oblique elliptical cone expression;

Any point on the fitted elliptical halo and the optical center of the calibrated CCD camera form an imaging straight line expression;

The three-dimensional coordinates of a pair of points on the conical structured light surface to be calibrated are obtained by jointly solving the oblique elliptical cone surface equation and the imaging line equation;

By selecting a series of points on the elliptical halo, a series of corresponding three-dimensional coordinates can be obtained, but these points are coplanar, and the fitting of the conical surface cannot be achieved, so it is necessary to arbitrarily change the position and attitude of the blank light-transmitting plate to obtain For non-coplanar halo calibration images, it is generally necessary to shoot 6 different positions and attitudes;

Least square fitting is performed on the center of the fitted elliptical halo to determine the axis of the conical surface of the structured light, the surface equation of the conical structured light is obtained, the conical surface of the structured light is reconstructed, and the calibration of the conical structured light is completed.

Step 2. Obtaining the three-dimensional geometric size information of the inner hole of the tested workpiece:

First, the structured light projection device is controlled to project the calibrated structured light to the inner hole of the workpiece to be tested, and the synchronous drive device drives the structured light projection device and the CCD camera of the image acquisition device to move synchronously in the Z direction to complete the scanning of the inner hole of the workpiece to be tested. A series of corresponding halo images projected by the structured light to the inner hole of the workpiece under test are acquired by the image acquisition device;

Pass a series of corresponding halo images to the computer control and processing device, fit the halo images captured by the image acquisition device, and substitute the conical structured light surface equation to obtain the three-dimensional coordinates of the scanning point in the world coordinate system, and obtain the measured workpiece Inner hole 3D geometry, shape error and surface defect information.

The advantages and positive effects of the present invention are:

Combined with digital photogrammetry and image processing technology, the universal tool microscope is simply transformed based on the principle of structured light measurement, which expands the application range of the original universal tool microscope, and quickly and accurately obtains the Z axis on the basis of obtaining the X and Y axis size information. Dimension information realizes non-contact measurement of three-dimensional geometric dimension information, and can also detect information such as shape errors and surface defects in the Z-axis direction, while maintaining the original accuracy while improving efficiency, the transformation structure is simple, low cost, and easy to manufacture. , easy to operate, intuitive and reliable detection results, to meet the needs of automated measurement, has broad application prospects in the field of measurement.

Description of drawings

1 is a schematic diagram of a three-dimensional measurement device for a universal tool microscope based on structured light provided by an embodiment of the present invention;

2 is a schematic diagram of system calibration provided by an embodiment of the present invention;

3 is a schematic diagram of a halo calibration image provided by an embodiment of the present invention;

FIG. 4 is a schematic diagram of a conical structured light provided by an embodiment of the present invention.

Among them: universal tool display body 1, image acquisition device 2, structured light projection device 3, synchronous drive device 4, computer control and processing device 5, CCD camera 6, calibration plate plane 7, light-transmitting plate 8, base 11, work Stage 12 , lateral guide rail 13 , vertical guide rail 14 , CCD camera 21 , including fiber laser 31 , conical refractor 32 , and displacement sensor 41 .

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

As shown in FIG. 1 , the three-dimensional measurement device for a universal tool microscope based on structured light designed by the present invention includes a universal tool display body 1, an image acquisition device 2, a structured light projection device 3, a synchronous drive device 4 and a computer control and processing device. 5.

The universal tool microscope body 1 is mainly composed of a base 11, a worktable 12, a lateral guide rail 13, a longitudinal guide rail 14, an aiming microscope system, a grating reading system, an illumination system and other accessories;

Image acquisition device 2, retains the optical lens imaging system and grating reading system in the aiming microscope system of the universal tool microscope, and uses the CCD camera 21 instead of the original eyepiece to collect the calibration image and the image information of the measured workpiece;

The structured light projection device 3 includes a fiber laser 31 and a conical refracting mirror 32. The laser beam emitted by the fiber laser 31 is refracted by the conical refracting mirror 32 to form a conical structured light, which is projected onto the blank light-transmitting plate 8 and the surface of the workpiece to be measured. The acquisition device obtains the calibration and the image of the measured workpiece;

The synchronous drive device 4 includes a displacement sensor 41, a single-chip microcomputer, a driver, a stepping motor and a secondary gear. The displacement sensor 41 is fixed on the Z-axis lifting arm to detect the moving distance of the CCD camera of the image acquisition device in the Z direction, and feeds the driver through the single-chip microcomputer. The pulse generator signal in the device drives the stepping motor, and then drives the secondary gear to make the structured light projection device and the CCD camera of the image acquisition device move synchronously in the Z direction;

The computer control and processing device 5 controls the image acquisition device 2 to obtain the calibration and the image of the workpiece to be measured, and processes the collected images through a preset algorithm.

The first time to use the modified universal tool microscope, it is necessary to calibrate the internal and external parameters of the camera and the parameters of the conical structured light, as shown in Figure 2, and then use it under the premise that the relative positions of the image acquisition device 2 and the structured light projection device 3 remain unchanged. No need to calibrate again.

First, the calibration of the internal and external parameters of the camera is carried out. Another CCD camera 6 for calibration is fixed, and the included angle between its optical axis and the optical axis of the CCD camera 21 of the image acquisition device 2 is less than 90°. The computer control and processing device 5 controls the CCD camera 21 of the image acquisition device 2 and the calibration CCD camera 6 to simultaneously shoot the calibration plate plane 7 with uniform marking points, and uses the Zhang Zhengyou plane template calibration method to process the collected images, and calibrate the image acquisition. The internal and external parameters of the CCD camera 21 of the device 2 and the calibration CCD camera 6 are unified into the same world coordinate system.

Next, the calibration of the conical structured light is performed. Control the structured light projection device 3 to project the conical structured light to the blank light-transmitting plate 8, move the Z-axis lifting arm to focus the projected structured light on the blank light-transmitting plate 8, and connect the light-transmitting plate 8 and the projected structured light in any direction Intersection with the position (usually 6 different poses), the intersection line (halo) is a space ellipse E _i , the expression is:

γ是结构光圆锥面的俯仰角和偏航角，x、y、z是世界坐标，本发明将标定图像采集装置2的CCD摄像头21的相机坐标选为世界坐标。In the formula, Δ _x , Δ _y , Δ _z are the offsets of the three axis directions of the structured light cone, α is the cone apex angle of the structured light cone,

γ is the pitch angle and yaw angle of the structured light conical surface, and x, y, and z are world coordinates. The present invention selects the camera coordinates of the CCD camera 21 of the calibration image acquisition device 2 as the world coordinates.

The computer control and processing device 5 controls the image acquisition device 2 and the calibration CCD camera 6 to obtain the calibration image of the non-coplanar corresponding halo of the structured light projected onto the blank light-transmitting plate 8, that is, the above-mentioned elliptical halo E _i is simultaneously captured by the two cameras. The corresponding halo calibration image is shown in Figure 3. According to the geometric projection, the images captured by the two cameras are also elliptical. Therefore, the inner edge of the halo calibration image is fitted as an elliptical halo, and the halo calibration image captured by the image acquisition device 2 is fitted with an ellipse. The halo is e _i1 , the elliptical halo fitted to the halo calibration image captured by the calibration CCD camera 6 is e _i2 , and the expression is:

After the camera parameters are calibrated, the focal length f ₁ of the CCD camera 21 of the image acquisition device 2 can be known, then the expression of e _i1 in the world coordinate system is:

The spatial elliptical halo E _i and the optical center of the CCD camera 21 of the image acquisition device construct an oblique elliptical cone A _i , and any point on the fitted spatial elliptical halo E _i and the optical center of the calibration CCD camera 6 form an imaging light L _p , as shown in the figure 4 shown. The expression of oblique elliptical cone A _i is:

The expression of imaging ray L _p is:

Among them, (RT) is the coordinate transformation between the calibration camera and the detection camera.

和γ。再通过最小二乘法搜索剩下四个参数(Δ_x，Δ_y，Δ_z，α)的最优值：The least squares fitting is performed on the center of the fitted elliptical halo after the images obtained under different poses to determine the axis of the structured light cone, that is, the two parameters in formula (1).

and γ. Then search the optimal value of the remaining four parameters (Δ _x , Δ _y , Δ _z , α) by the least square method:

where d _ik is the distance from the point to the axis, and r _ik is the radius of the corresponding section.

The joint solution of the oblique elliptical cone A _i equation (4) and the imaging ray L _p equation (5) can determine the surface point of the cone. A set of surface points constructs a spatial ellipse, and different sets of surface points are generated by moving the blank light-transmitting plate 8 to obtain different spatial ellipses, and then the structured light conical surface can be reconstructed to complete the calibration of the conical structured light.

After the calibration is completed, the three-dimensional geometric size, shape error and surface defect information of the inner hole of the tested workpiece can be obtained.

First, the workpiece to be tested is fixed on the workbench 12, and the structured light projection device 3 is controlled to project the calibrated structured light to the inner hole of the workpiece to be tested;

Next, the synchronous drive device 4 drives the structured light projection device 3 and the CCD camera 21 of the image acquisition device 2 to move synchronously in the Z direction to complete the scanning of the inner hole of the workpiece to be tested, and the computer control and processing device 5 controls the image acquisition device 2 to obtain the acquisition. A series of corresponding halo images projecting the structured light to the inner hole of the workpiece under test;

Finally, a series of corresponding halo images are transmitted to the computer control and processing device 5, the halo images captured by the image acquisition device 2 are fitted, and the previously calibrated conical structured light surface equation is substituted to obtain the scanning point in the world coordinate system. The three-dimensional coordinates are obtained to obtain the three-dimensional point cloud data of the inner hole of the tested workpiece, and then the geometric size, shape error and surface defect information in the Z-axis direction are obtained.

Claims (2)

1. A universal tool microscope three-dimensional measuring device based on structured light comprises a universal tool microscope body, wherein the universal tool microscope body comprises a base, a workbench, longitudinal and transverse guide rails, an aiming microscope system and an illuminating system; the sighting microscope system comprises an optical lens imaging system and a grating reading system; the method is characterized in that: the measuring device also comprises an image acquisition device, a structured light projection device, a synchronous driving device and a computer control and processing device, wherein:

the image acquisition device reserves an optical lens imaging system and a grating reading system in a universal tool microscope aiming microscope system, and adopts a CCD camera to replace an original eyepiece to acquire calibration images and image information of a workpiece to be detected;

the structured light projection device comprises a fiber laser and a conical refractor, a host LED (light emitting diode) lighting source in the universal tool microscope lighting system is transformed into the structured light projection device, the original structure which synchronously moves in the direction X, Y with an eyepiece of a sighting microscope system is reserved, a laser beam emitted by the fiber laser in the structured light projection device is refracted by the conical refractor to form conical structured light to be projected to a blank light-transmitting flat plate, the structured light is projected to the surface of a workpiece to be measured after a corresponding halo image is calibrated, and the image is acquired by an image acquisition device;

the synchronous driving device comprises a displacement sensor, a single chip microcomputer, a driver, a stepping motor and a secondary gear, wherein the displacement sensor is fixed on a Z-axis lifting arm to detect the moving distance of a CCD camera of the image acquisition device in the Z direction, and the pulse generator signal in the driver is sent to drive the stepping motor through the single chip microcomputer so as to drive the secondary gear to enable the structured light projection device and the CCD camera of the image acquisition device to synchronously move in the Z direction;

and the computer control and processing device is used for controlling the image acquisition device to acquire images of the calibrated and detected workpiece and processing the acquired images through a preset algorithm.

2. A three-dimensional measurement method of a universal tool microscope based on structured light is characterized in that: the method comprises the following steps:

step 1, using the transformed universal tool microscope for the first time, obtaining the internal and external parameters of the camera and the conical structured light parameters by calibration, and then using the universal tool microscope without calibration again on the premise of ensuring that the relative positions of the image acquisition device and the structured light projection device are not changed;

providing a blank light-transmitting flat plate and a CCD camera only used for calibration;

calibrating the included angle between the CCD camera and the CCD camera optical axis of the image acquisition device to be less than 90 degrees;

1) calibration of internal and external parameters of camera

The computer control and processing device controls a CCD camera and a calibration CCD camera of the image acquisition device to shoot a calibration plate plane with uniform marking points;

processing the acquired image by using a Zhangyingyou plane template calibration method, calibrating a CCD camera of the image acquisition device and calibrating internal and external parameters of the CCD camera, and unifying external parameters of the two cameras under the same world coordinate system;

2) calibration of conical structured light

Controlling the structured light projection device to project conical structured light to the blank light-transmitting flat plate, and moving the Z-axis lifting arm to focus the projected structured light on the blank light-transmitting flat plate;

the computer control and processing device controls the image acquisition device and the calibration CCD camera to acquire a corresponding halo calibration image of the structured light projected to the blank light-transmitting flat plate;

detecting the inner edge of the halo calibration image and fitting the inner edge of the halo into an elliptical halo image;

constructing an oblique elliptic cone expression by the fitted elliptic light ring and the light center of a CCD camera of the image acquisition device;

any point on the fitted elliptical halo forms an imaging straight line expression with the optical center of the calibrated CCD camera;

the surface equation of the oblique elliptic cone and the imaging linear equation are jointly solved to obtain the three-dimensional coordinates of a point on the smooth surface of the conical structure to be calibrated;

a series of corresponding three-dimensional coordinates can be obtained by selecting points on a series of elliptical light rings, but the points are coplanar and cannot realize fitting of a conical surface, so that the position and the posture of a blank light-transmitting flat plate need to be changed randomly to obtain a non-coplanar light ring calibration image, and generally 6 different positions and postures need to be shot;

performing least square fitting on the fitted elliptic light ring center to determine the axis of the conical surface of the structured light, obtaining the surface equation of the conical structured light, reconstructing the conical surface of the structured light, and completing calibration of the conical structured light;

step 2, obtaining three-dimensional geometric dimension information of an inner hole of the workpiece to be measured:

firstly, controlling a structured light projection device to project calibrated structured light to an inner hole of a workpiece to be measured, driving a CCD (charge coupled device) camera of the structured light projection device and an image acquisition device to synchronously move in a Z direction to complete scanning of the inner hole of the workpiece to be measured by a synchronous driving device, and acquiring a series of corresponding halo images of the structured light projected to the inner hole of the workpiece to be measured by the image acquisition device;

and transferring a series of corresponding halo images to a computer control and processing device, fitting the halo images captured by the image acquisition device, substituting the halo images into a conical structured light surface equation to obtain the three-dimensional coordinates of the scanning points in a world coordinate system, and obtaining the three-dimensional geometric dimension, the shape error and the surface defect information of the inner hole of the workpiece to be measured.

Images