Study On Parallel Chromatic Confocal Topography Measurement System Based On Digital Micromirror Device

With the rapid development of science and technology,especially with the development of precision machining technology,the measurement requirements for the micro surface morphology of parts are developing towards higher vertical and horizontal resolution,better stability,and faster speed.The chromatic confocal measurement method derived from confocal measurement technology has become the hot spot of experts and scholars at home and abroad in recent years because of its accuracy,rapid measurement and high resolution.The chromatic confocal measurement method does not rely on the axial tomography technology,but only relies on the 2D transverse scanning perpendicular to the optical axis direction,can obtain the 3D morphological characteristics of the material surface,greatly shortening the detection time,improving the measurement efficiency,has become a hot spot of experts and scholars at home and abroad.This paper presents a Digital Micromirror Device(DMD)based full-field confocal microscope measurement system.The system is mainly composed of DMD,polychromatic light source,dispersive tube mirror and color array camera.Building through the DMD multicast parallel light source,using color camera to contain multiple points of data gathered image decoding,using color conversion algorithm optimization,establishing goals of each point on the surface of height and color camera detects the color information of each pixel point on the link between the mathematical model,and the corresponding 3D reconstruction of morphology,implements the whole parallel chromatic confocal measurement,to promote the development of chromatic confocal measurement technology has practical significance.The main research contents of this paper are as follows:(1)The principle of chromatic confocal measurement is analyzed theoretically.On the basis of theoretical analysis of laser confocal technology,the point spread function of parallel chromatic confocal technology is deduced.Combined with the structure principle of DMD,the parallel chromatic confocal measurement model based on DMD is studied and established.(2)Through theoretical analysis and reasonable selection of system components,a parallel chromatic confocal measurement system was built;Aiming at the problem of color camera data processing,the multi-point parallel processing of color conversion algorithm is studied.(3)The experimental study was carried out in the system.Through the system calibration experiment,the measurement feasibility of the system is verified,and the effective measurement range of the system is obtained.The measurement range of the system is 300μm under the condition of 4 times objective lens.Error analysis and compensation are made to the system to improve the measurement accuracy of the system.The axial resolution and parallel measurement ability of the system are verified by single point measurement and multi-point measurement experiments on the steps constructed by standard measuring blocks.The measurement experiment was carried out on the coin surface,and the 3D morphology of the coin surface was recovered,which verified the 3D measurement ability of the system.