The surface roughness of a workpiece is an important indicator for evaluating the surface quality of the workpiece. It is an important parameter that determines the performance and quality of the workpiece. The rapid development of science and technology, the continuous improvement of processing accuracy, and the emergence of new technologies, new materials, and new processes have put forward higher and higher requirements for the detection of workpiece surface roughness. At the same time, the research on friction and wear processes, the analysis of process processes, and the discussion of surface contact states all require a quantitative description of the surface micro-geometry. The traditional contact measurement method is easy to scratch the surface of the workpiece, the measurement speed is low, and the measurement range is affected by the radius of the probe, which is not suitable for online detection.
The use of optical non-contact measurement methods can make up for the shortcomings of stylus measuring instruments. Common optical measurement methods include light scattering method, optical speckle method, focusing method, interferometry method, etc. The optical method for measuring surface roughness is based on the optical effect of the measured surface. The light waves emitted by the light source are incident on the surface of the measured object in parallel, divergent or convergent manner through the optical system. The reflected light waves on the surface of the measured object reflect the surface shape of the measured object. The optical information of the reflected light waves is received, converted, calculated, displayed, and recorded by various types of photoelectric sensors and post-processing circuits. This paper adopts a surface roughness measurement method based on the principle of laser scattering, which can realize non-destructive testing and non-contact online rapid testing of the surface roughness of high-precision parts, and has high economic value.
Scattering phenomenon of light on rough surfaces
When a beam of light is incident on the surface of a rough object at a certain angle, according to the geometric principle of light, the light will be scattered and reflected by the object, and the intensity of the scattered light and reflected light is related to the surface roughness of the object. The reflected light is concentrated on a very small area to form a light spot: the scattered light is distributed around the reflected light spot to form a light band composed of many light spots. If the surface of an object is relatively smooth, the light energy of the reflected light spot is relatively strong and the scattered light band is relatively narrow; on the contrary, if the surface of an object is relatively rough, the light energy of the reflected light spot is relatively weak and the scattered light band is relatively wide. This phenomenon qualitatively shows that the intensity of scattered light energy is related to the roughness of the surface of the object. This paper quantitatively obtains information on the surface roughness of an object by studying the light energy distribution of scattered light.
