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Chromatic confocal measurement is a type of non-contact measurement technology, which can be used to detect three-dimensional profile of surfaces without axial scanning. It has the characteristics of high precision and high efficiency. Line scanning chromatic confocal measurement system can obtain the depth information in the linear field of view, which can get the three-dimensional information by one-dimensional scanning, having higher efficiency compared with the point scanning type. There are two different types of design in the chromatic confocal measurement system: single- axis design and dual-axis design. The dual-axis design has several advantages over the single-axis design such as smaller effective axial spot size and higher axial resolution, and the separation of illumination system and detection system can decrease the stray light and the energy loss. In this paper, we analyze the parameters of optical system according to the practical requirements and design the optical system for a dual axis scanning confocal measurement system. Its system optical magnification is 1 and the F number is 2.5, waveband covers 450-700nm. The system uses linear variable filter to generate the spectrum, which is helpful to get the simpler system structure, the lower cost and the larger axial measurement range, compared with the traditional method using grating or prism to split the light. The visible light emitted from the light source permeates through the filter and the lens group, then the light with different wavelengths is focused on different positions on the focal plane of the measured surface. The results show that the measurement range of the system is up to 3 mm, the length of the scanning contour is up to 12 mm, and the average axial resolution is up to 1.6μm, meeting the designated measurement requirements.
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