Disclosure of Invention
In view of the above, the present invention aims to provide a contact probe device and a measuring method thereof based on the light reflection principle, which can reduce the cost of a precision probe, and has high measuring precision and good reliability, and can realize the measurement of micro force measurement.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
the contact type measuring head device based on the light reflection principle at least comprises the following components: the device comprises a shell, a fixed lens, a variable lens, an elastic component, a measuring needle matrix, a measuring rod, a measuring ball, two groups of laser light sources and an image sensor, wherein the shell is connected with the elastic component, the measuring needle matrix is connected with the elastic component, the fixed lens is arranged on the shell, the variable lens is arranged on the elastic component, and the laser light sources and the image sensor are arranged on the shell;
the light emitted by the laser light source can be irradiated to the image sensor after being reflected by the fixed lens and the variable lens, and a certain angle is formed between two planes formed by the centers of the two groups of image sensors and the laser light source and the center of the variable lens, and the angle cannot be equal to an integer multiple of 180 degrees.
Further, the laser emitted by the laser light source irradiates the corresponding image sensor receiving area after being reflected by the fixed lens and the variable lens for a plurality of times.
Further, the distance between the image sensor and the variable lens is greater than the distance between the fixed lens and the variable lens.
Further, the gauge head device further comprises a mounting part connected with the shell, and the protruding part of the mounting part is connected with the measuring machine.
Further, the measuring needle matrix, the measuring rod and the measuring ball are of an integrated structure, and form the measuring needle together.
Further, the elastic component is provided with a threaded hole for installing the measuring needle matrix, the bottom end of the elastic component is provided with a boss, and the boss is provided with a flat position.
Alternatively, in one embodiment of the present invention, two image sensors may be combined into one to save costs.
A measuring method of a contact type measuring head device based on a light reflection principle comprises the following steps:
step1: calibrating an origin of a coordinate system of the image sensor;
step 2: calibrating the radius of the measuring ball;
Step 3: the corresponding relation between the center coordinates of the light spot and the center position of the measuring ball under the measuring head coordinate system is calibrated, and the final measured value is obtained by combining the relation between the measuring head coordinate system and the measuring machine coordinate system;
step 4: calculating to obtain the central coordinates of the light spots on the two image sensors according to the method for obtaining the central coordinates of the light spots on the image sensors;
Step 5: and calculating a measured value according to the central coordinate of the light spot and the calibration result.
Further, the method for obtaining the center coordinates of the light spot on the image sensor comprises the following steps:
Step 1: reading the spot image and extracting the spot edge; the laser emitted by the laser source irradiates on the image sensor after being reflected between the variable lens and the fixed lens to form a light spot; the computer reads the spot image and extracts the spot edge.
Step 2: calculating the central coordinates of the light spots; the light spot is subjected to binarization processing, the area of the light spot is calculated, the area center coordinate of the light spot is further calculated, and the center coordinates are used as center coordinates G1 and G2 of the light spot.
The beneficial effects of the invention are as follows:
1. In the device, the measuring needle matrix is connected with the elastic component provided with the variable lens, when the measuring ball touches a measured workpiece, the elastic device deforms, the posture of the variable lens arranged on the elastic device changes, and after light is reflected between the variable lens and the fixed lens for multiple times, the position of a light spot irradiated on the image sensor changes, so that the displacement change quantity of the surface of the measured ball is detected; further, the image sensor is used for receiving light, the computer is used for calculating a measured value according to the pixel points irradiated by the light, and the measuring precision is high, the sensitivity is high, the measuring speed is high, and the cost is low;
2. The laser light sources and the image sensors are correspondingly distributed, the two groups of laser light sources and the image sensors are intersected and distributed at a certain angle, under the condition of not considering torsion, the measuring ball has three degrees of freedom, and the two groups of image sensors can represent four degrees of freedom, so that the distribution mode can ensure the uniqueness of the measured value;
3. The laser light source emits laser, and finally emits the laser into a receiving area of the image sensor after multiple reflections. In the process, the laser is reflected for multiple times, and the variation of the included angle between the reflected light finally injected into the image sensor and the horizontal plane is 2n times of the inclination angle of the mirror surface caused by the deformation of the elastic component during measurement, wherein n is the reflection times of the light on the variable lens, so that the sensitivity and the precision of the measuring head are greatly improved, and the measurement of micro force measurement can be realized;
4. A flat position is designed at a boss below the elastic device and used for bearing the torque of a spanner when the measuring needle is replaced, so that the elastic part is prevented from being damaged, and the efficient needle replacement can be realized;
5. the distance between the image sensor and the variable lens is larger than that between the fixed lens and the variable lens, so that the deformation of the elastic component is amplified, and the measurement resolution can be improved.
Detailed Description
Specific examples are given below to further clarify, complete and detailed description of the technical scheme of the invention. The present embodiment is a preferred embodiment based on the technical solution of the present invention, but the scope of the present invention is not limited to the following embodiments.
Example 1
The contact type measuring head device based on the light reflection principle comprises the following components: the device comprises a mounting component 1, a shell 2, an image sensor 3, a laser light source 4, a fixed lens 5, a variable lens 6, an elastic component 7, a measuring needle matrix 8, a measuring rod 9 and a measuring ball 10, wherein the elastic component 7 is arranged at the bottom end of the shell 2 and is detachably connected with the measuring needle matrix 8, the variable lens 6 is arranged on a boss in the center of the elastic component 7, the fixed lens 5 is arranged right above the variable lens 6 and is fixedly connected with an boss in the shell 2, the laser light source and the image sensor are mounted on the shell and are just opposite to each other, and two groups of laser light sources and the image sensor are intersected and distributed at a certain angle.
Alternatively, in this embodiment, referring to fig. 1, which is a schematic structural diagram of a contact probe device based on the light reflection principle, a housing 2 is connected with an elastic member 7 by threads, a probe base 8 is connected with the elastic member 7 by threads, a fixed lens 4 is mounted on a boss of the housing 2, and a variable lens 6 is mounted on a boss of the elastic member.
Further, in the present embodiment, referring to fig. 3, a schematic distribution diagram of two sets of laser light sources and image sensors is shown. Wherein the laser light source 4 and the image sensor 3 are distributed in opposite directions, and a certain angle is formed between the centers of the two groups of image sensors 4 and the laser light source 3 and two planes formed by the centers of the variable lenses 6. The measuring ball has three degrees of freedom without considering torsion, and the two groups of image sensors can represent four degrees of freedom, so that the distribution mode can ensure the uniqueness of the measured value. Referring to fig. 6, in the light reflection process when there is only one set of the laser light source 4 and the image sensor 3, the position of the variable lens 6 changes, but the light irradiates the same position of the image sensor 3 after being reflected at two different positions of the variable mirror, and the calculated measurement value is inaccurate, so that the displacement of the measuring ball 10 corresponding to the measurement value cannot be guaranteed to be unique by the one set of the laser light source 4 and the image sensor 3, and the uniqueness of the measurement value can be guaranteed by the two sets of the laser light source 4 and the image sensor 3.
Preferably, the optimal scheme of the invention is that the laser light source and the image sensor are distributed in 180 degrees opposite, and the two groups of image sensors and the two planes formed by the center of the laser light source and the center of the variable lens are distributed in a 90-degree intersection way.
Alternatively, in the present embodiment, fig. 4 is a schematic three-dimensional structure of two sensors combined into one sensor, and this structure uses fewer image sensors, which reduces the cost. The combination of two sensors into one sensor can be realized by increasing the area of the sensor, or by adding a reflecting mirror, and enabling two beams of light to enter the same sensor, or by other modes. When the light rays emitted by the two light sources enter the same sensor, the light rays from different light sources can be distinguished by enabling the two light sources to emit light in a time-sharing manner.
Further, the center of the image sensor 3, the center of the laser light source 4 correspondingly matched with the center of the variable lens 6 form planes, and a certain angle is formed between the planes, and the angle cannot be equal to an integer multiple of 180 degrees. Specifically, three points formed by the center of the image sensor 3, the center of the laser light source 4 correspondingly matched with the center of the variable lens 6 are defined as a group to form a plane, two groups of points form two planes, and the angle between the two planes cannot be equal to an integer multiple of 180 degrees, so that the light emitted by the laser light source 4 can be irradiated onto the image sensor 3 after being reflected by the fixed lens 5 and the variable lens 6.
Further, the distance between the image sensor 3 and the variable lens 6 is greater than the distance between the fixed lens 5 and the variable lens 6. The distance is the light path distance, thus having an amplifying effect on the deformation of the elastic member 7, and improving the measurement resolution.
Further, in the present device, the laser light source 4 emits laser light, and fig. 5 shows a schematic diagram of laser reflection of the contact probe device based on the light reflection principle, in which the laser light source 4 emits laser light, and the laser light finally enters the receiving area of the image sensor 3 after multiple reflections between the variable lens 6 and the fixed lens 5. In the process, the variation of the included angle between the reflected light finally injected into the image sensor and the horizontal plane is 2n times of the inclination angle of the mirror surface caused by the deformation of the elastic component during measurement, wherein n is the reflection times of the light on the variable lens 6, the sensitivity and the precision of the measuring head are greatly improved, and the measurement of the micro force measurement can be realized.
Further, referring to fig. 7 to 9, when the ball 10 is stressed along the x-axis, the y-axis and the z-axis, respectively, the light spots on the final image sensor 3 change, the two sets of laser light sources 4 and the image sensor 3 intersect at a certain angle, and the ball 10 has three degrees of freedom without considering torsion, and the two sets of image sensors 3 can represent four degrees of freedom, so that the invention adopts a distribution mode of the two sets of image sensors 3, and can ensure the uniqueness of the measured values.
Further, the gauge head device also comprises a mounting part 1 connected with the shell 2, and the extending part of the mounting part 1 is connected with the measuring machine.
Further, the contact probe is of an integrated structure.
Further, in the component parts of the contact type measuring head device based on the light reflection principle, the measuring needle 8 and the elastic component 7 are in threaded connection, so that the quick replacement of the measuring needle can be realized, and the flat position is designed at the boss of the elastic component 7 for installing the measuring needle, thereby being beneficial to replacing the measuring needle and not easily damaging the elastic component.
Further, the plane of the image sensor 3 mounted in the housing 2 is perpendicular to the optical path of the laser beam reflected by the variable lens 6 when the elastic member 7 is not deformed and then incident into the image sensor 3, and the foot hangs down at the center of the receiving area of the image sensor 3, so that the measuring range of the measuring head is maximized.
Further, the sensor is in signal connection with a computer, and is used for processing data received by the sensor, when the image sensor 3 receives light, the signal is transmitted to the computer, the computer calculates a measured value of the measured object according to the position of the light irradiated on the receiving area of the image sensor 3, and the measured precision is related to the resolution of the image sensor 3. The computer is used for calculating the measured value according to the pixel points irradiated by the light, and the measuring precision is high, the sensitivity is high, the measuring speed is high and the cost is low.
Further, in this embodiment, the elastic member 7 is provided with four elastic pieces, which are circular and have moderate thickness, so that the sensitivity of the elastic member 7 to stress deformation is improved and the stylus can be supported.
In the present embodiment, the image sensor 3 may select a CMOS image sensor 3 or a CCD image sensor 3, and image sensors 3 of different sizes and resolutions may be used to satisfy measurement accuracy.
Example 2
A method for measuring a contact probe device based on the principle of light reflection, based on the device mentioned in example 1, comprising the steps of:
Step 1: calibrating the origin of a coordinate system of the image sensor 3;
When the measuring ball 10 is in a free state, laser emitted by the laser light source 4 irradiates on the image sensor 3 to form a light spot after being reflected by the variable lens 6 and the fixed lens 5, the center coordinates of the light spots on the two image sensors 3 are calculated according to the method for obtaining the center coordinates of the light spots on the image sensors, and the point is used as an origin of a coordinate system of the image sensor 3.
Step 2: the radius of the sphere 10 is calibrated, comprising the following sub-steps:
A. Controlling the measuring head to move so that the measuring ball 10 is close to the standard ball and is approximately equal to the center of the standard ball, and enabling the measuring ball 10 to touch the standard ball for a plurality of times along the direction parallel to the x axis or the y axis; when the measuring ball 10 just touches the standard ball, the position of the light spot on the image sensor 3 can be changed, and the values of the X-axis grating ruler and the y-axis grating ruler of the measuring machine are required to be recorded; after the measuring ball 10 touches the standard ball, the measuring ball 10 is immediately removed;
B. the measuring machine controls the position of the measuring head, and then adjusts the contact position of the measuring ball 10 and the standard ball until the maximum section parallel to the xoy plane on the standard ball is found;
C. the measuring head touches at least three points in one circle of the maximum section of the standard sphere, and records the values of the grating ruler of the x axis and the y axis of the measuring machine when in each touch, so that the radius r of the measuring sphere 10 can be calculated.
Step 3: the corresponding relation between the central coordinate of the light spot under the measuring head coordinate system and the central position of the measuring ball 10 is calibrated, and the final measured value is obtained by combining the relation between the measuring head coordinate system and the measuring machine coordinate system;
The movement of the measuring head is controlled to enable the measuring head to touch the standard ball along the positive direction of the x axis, the negative direction of the x axis, the positive direction of the y axis, the negative direction of the y axis and the negative direction of the z axis respectively, and along with the movement of the measuring head, the measuring force between the measuring ball 10 and the standard ball is gradually increased, and the position of a light spot on the image sensor 3 is also continuously changed;
The distance that the center of the measuring ball 10 moves relative to the measuring head in the touching process can be calculated according to the reading of the grating ruler of the measuring machine, and meanwhile, the center coordinate G1i,G2i of the light spot on the image sensor 3 is recorded. Obtaining the relation between the center coordinate Pa of the measuring ball 10 and the center coordinate G1,G2 of the light spot in the measuring head coordinate system by using a linear interpolation algorithm according to the recorded data, and obtaining the final measured value P by combining the relation between the measuring head coordinate system and the measuring machine coordinate system:
Pa(xa,ya,za)＝f[G1(x1,y1),G2(x2,y2)]
P(x,y,z)＝g[Pa(xa,ya,za)]
Wherein, (xa,ya,za) is the coordinate of the center of the sphere in the coordinate system of the measuring head, (x1,y1) and (x2,y2) are the coordinate of the photoelectric center in the coordinate systems of the two image sensors, and (x, y, z) is the final measured value.
Step 4: acquiring center coordinates of light spots on the two image sensors 3;
the measuring head touches the measured workpiece, the posture of the variable lens 6 is changed, and the center coordinates of the light spots on the two image sensors 3 are calculated according to the method for obtaining the center coordinates of the light spots on the image sensors.
Step 5: knowing the center coordinates of the light spots and the relationship between the center coordinates of the measuring ball 10 and the center coordinates of the light spots in the measuring head coordinate system, the center coordinates Pa(xa,ya,za of the measuring ball 10 in the measuring head coordinate system can be calculated, and the final measured value P (x, y, z) can be obtained by combining the relationship between the measuring head coordinate system and the measuring machine coordinate system.
The method for obtaining the central coordinate of the light spot on the image sensor comprises the following steps:
Step 1: the spot image is read and the spot edge is extracted. The laser light emitted from the laser light source is reflected between the variable mirror 6 and the fixed mirror 5 and then irradiated onto the image sensor to form a light spot. The computer reads the light spot image and extracts the light spot edge;
Step 2: the central coordinates of the spot are calculated. The light spot is subjected to binarization processing, the area of the light spot is calculated, the area center coordinate of the light spot is further calculated, and the center coordinates are used as center coordinates G1 and G2 of the light spot.
The foregoing has outlined and described the features, principles, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiments, and that the above-described embodiments and descriptions are merely illustrative of the principles of the present invention, and that various changes and modifications may be made in the invention without departing from the spirit and scope of the invention, which is defined by the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.