CN107036559A - A kind of measuring method of curved surface slope - Google Patents

Abstract

The invention discloses a method for measuring the slope of a curved surface. The optical measuring head is used for measurement. The optical measuring head includes a laser, an aperture stop, a reflector, a beam splitting prism, an imaging lens and a CCD camera. The collimated light beam emitted by the laser passes through the The aperture diaphragm shrinks into a thin straight beam, which enters the beam splitter after passing through the reflector, and the reflected beam with 1/2 energy is projected to any point on the curved surface. The lens is imaged on the CCD camera, and the data processing module calculates the slope information of the point on the surface according to the position of the light spot in the CCD camera. The present invention utilizes the principle of the autocollimator to measure the slope of the tangent line at any point on the curved surface including the plane, and has a large application space for the detection of the shape of the optical free-form surface and the measurement of various angles, and High precision, accurate and reliable data.

Description

A Measuring Method of Surface Slope

technical field

The invention relates to a method for measuring the slope of a curved surface.

Background technique

In the field of machine tool error detection, widely used machine tool error detection instruments include laser interferometers and ballbars. Due to their own detection principles, these instruments have their own shortcomings in the error detection of multi-axis CNC machine tools: For example, the adjustment of the laser interferometer is complicated, and only one parameter can be obtained for one measurement. The operation requirements are high, it is difficult to realize automation and speed, and the price is expensive, which is not available in general enterprises; The design of measurement steps and the study of theoretical decoupling algorithms have increased the difficulty, and the ballbar uses a magnetic base and a precision ball for contact measurement, which needs to be moved at a low speed to ensure measurement accuracy, and it is difficult to adapt to the trend of rapidity. The one-dimensional spherical column is suitable for the linear calibration of each axis, but it has no advantage in the detection of angular errors, and the relative error between the axes of the multi-axis machine tool has a great influence on the machining accuracy.

For the processing of complex special-shaped parts, multi-axis CNC machining technology has been widely used and promoted due to its characteristics of flexibility, high efficiency and high precision. In order to meet the needs of regular precision calibration, efficient machine tool error detection and identification methods have become an urgent problem to be solved. question.

The geometric error detection items of multi-axis CNC machine tools mainly include the angular error, positioning error, straightness error, and verticality error of the motion axis. In order to detect the above-mentioned errors of the motion axis, an error detection method based on a curved surface reference piece , using this method needs to detect the slope of each point on different surface-shaped reference parts. Although the collimator system can measure the angle, the diameter of its own beam spot is very large. For measuring the tangent slope of any point on the surface, the spot The smaller the diameter, the closer the measured result is to the actual measurement point. Therefore, it is necessary to develop a method for measuring the slope of the surface for the detection of the tangent slope of each point on the surface.

Contents of the invention

The invention provides a method for measuring the slope of a curved surface in order to solve the technical problems in the known technology. The slope of the tangent line at each point on the curved surface can be measured by using the method.

The technical solution adopted by the present invention to solve the technical problems existing in the known technology is: a method for measuring the slope of a curved surface, using an optical measuring head for measurement, and the optical measuring head includes a laser, an aperture diaphragm, a reflector, and a beam splitting prism , an imaging lens and a CCD camera, the collimated beam emitted by the laser is narrowed into a thin straight beam through the aperture stop, the thin straight beam is incident on the beam splitting prism after passing through the reflector, and the reflection of 1/2 energy The light beam is projected onto any point on the curved surface, and the light beam reflected by the point is transmitted through the dichroic prism and then imaged on the CCD camera through the imaging lens; the method of using the optical measuring head for measurement is: according to the The position of the light spot in the CCD camera, calculate the slope information of the point on the surface: ξ _x = arctan(s _ox /f)/2, ξ _y = arctan(s _ox /f)/2, where: ξ _x represents the measurement point A The angle between the tangent line in the XOZ plane and the X-axis direction; ξ _y represents the angle between the tangent line of the measurement point A in the YOZ plane and the Y-axis direction; S _0x represents the distance between the center of the imaging spot A' in the X-axis direction Axis distance; S _0y represents the distance between the center of the imaging spot A' and the optical axis of the system in the Y-axis direction, and f represents the focal length of the imaging lens.

The advantages and positive effects of the present invention are: using the principle of the autocollimator, for curved surfaces including planes, the slope of the tangent line at any point on the curved surface can be measured, the detection of the shape of the optical free-form surface and the measurement of various angles There is a large application space, and the precision is high, and the data is accurate and reliable.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is a schematic diagram of the optical path of the present invention.

In the figure: 1. Laser; 2. Aperture stop; 3. Mirror; 4. Beam splitting prism; 5. Imaging lens; 6. CCD camera.

detailed description

In order to further understand the invention content, characteristics and effects of the present invention, the following examples are given, and detailed descriptions are as follows in conjunction with the accompanying drawings:

Please refer to FIG. 1 , a method for measuring the slope of a curved surface, using an optical probe for measurement, and the optical probe includes a laser 1 , an aperture stop 2 , a mirror 3 , a beam splitting prism 4 , an imaging lens 5 and a CCD camera 6 . The collimated beam emitted by the laser 1 is narrowed into a thin straight beam by the aperture stop 2, and the thin straight beam is incident on the beam splitting prism 4 after passing through the reflector 3, and the reflected beam of 1/2 energy is projected to At any point on the curved surface, the beam reflected by the point is transmitted through the dichroic prism 4 and then imaged on the CCD camera 6 through the imaging lens 5 .

The method for measuring with the optical measuring head is: according to the position of the imaging spot in the CCD camera 6, calculate the slope information of the point on the curved surface: ξ _x = arctan(s _ox /f)/2, ξ _y =arctan (so y /f)/2, where: _{ξ x} represents the angle between the tangent of measuring point A in the XOZ plane and the X-axis direction; ξ _y represents the angle between the tangent of measuring point A in the YOZ plane and the Y-axis direction ; S _0x represents the distance of the center of the imaging spot A' from the optical axis of the system in the X-axis direction, and the pixel coordinates of the optical axis and the imaging spot in the CCD camera can be obtained by measuring the data processing module, and by the corresponding size of the pixel in the CCD camera, Furthermore, the pixel coordinates in the X-axis direction can be converted into displacement S _0x ; S _0y represents the distance between the center of the imaging spot A' and the optical axis of the system in the Y-axis direction, and the pixel coordinates of the optical axis and the imaging spot in the CCD camera can be obtained by The data processing module measures and obtains, and through the size corresponding to the pixel in the CCD camera, the pixel coordinates in the Y-axis direction can be converted into a displacement S _0y ; f represents the focal length of the imaging lens.

Working principle of the present invention is:

Please refer to Figure 2. When the light beam is projected onto any point on the curved surface, due to the different curvatures of each point, the imaging spot positions of different measurement points in the CCD camera are different, that is, the slope of the tangent line at each point on the curved surface is different from the imaging spot in the CCD camera. The position has a one-to-one correspondence, and the slope of any point on the surface can be obtained according to the position of the imaging spot in the CCD camera.

Take the XOZ plane as an example to illustrate:

Among them: ξ _x represents the angle between the tangent of the measuring point A in the XOZ plane and the X-axis direction;

S _0x represents the distance from the center of the imaging spot A' to the optical axis of the system in the X-axis direction;

f represents the focal length of the imaging lens.

Through formula (1) can get:

ξ _x =arctan(s _ox /f)/2

In the same way:

ξ _y =arctan(s _y /f)/2

Therefore, the slope information of any point on the surface in the XOZ and YOZ planes can be obtained.

Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments. The above-mentioned specific embodiments are only illustrative and not restrictive. Those of ordinary skill in the art Under the enlightenment of the present invention, people can also make many forms without departing from the purpose of the present invention and the scope of protection of the claims, and these all belong to the protection scope of the present invention.

Claims (1)

1. a method for measuring the slope of a curved surface, characterized in that, an optical probe is used to measure, and the optical probe includes a laser, an aperture stop, a mirror, a beam splitting prism, an imaging lens and a CCD camera, and the laser sends The collimated beam is narrowed into a thin straight beam by the aperture stop, and the thin straight beam is incident on the beam splitting prism after passing through the reflector, and the reflected beam of 1/2 energy is projected onto any point on the curved surface, and the point reflects After the light beam is transmitted through the dichroic prism, it is imaged on the CCD camera through the imaging lens; The method for measuring with the optical measuring head is: according to the position of the light spot in the CCD camera, calculate the slope information of the point on the curved surface: ξ _x = arctan(s _ox /f)/2, ξ _y =arctan(s _oy /f)/2, Among them: ξ _x represents the angle between the tangent of the measuring point in the XOZ plane and the X-axis direction; ξ _y represents the angle between the tangent of the measurement point in the YOZ plane and the Y-axis direction; S _0x represents the distance from the center of the imaging spot to the optical axis of the system in the X-axis direction; S _0y represents the distance from the center of the imaging spot to the optical axis of the system in the Y-axis direction; f represents the focal length of the imaging lens.