Design of dual-channel common optical path dispersive objective lens

The Chromatic Confocal Displacement Sensor, with its capacity to avoid damage to the measured surface and achieve high measurement accuracy, has been widely used in many fields such as advanced manufacturing, biomedical, aerospace, and more. The dispersive objective lens is a core component of the chromatic confocal sensor, with its optical properties directly determining the system's measurement performance. To achieve real-time dynamic error separation in dynamic measurement scenarios and ensure high-precision measurement, a dual-channel common optical path structure is proposed. In dual-channel mode, the paths of the two measurement points are the same, and the information obtained about the object is consistent, with only the relative phase delay related to the distance from the two measurement points. By subtracting the two sets of data and fitting the error, real-time dynamic error can be obtained. Using ZEMAX optical design software, a linear dispersive objective lens composed of eight full-sphere lenses was designed. The design results indicate that the system operates in the wavelength range of 500-800nm, with the image numerical aperture greater than 0.68, a working distance greater than 7mm, and axial dispersion exceeding 100μm. Using the least squares method, linear regression calculations were performed on the dispersion-wavelength linearity, yielding a linear determination coefficient R2=0.9989, indicating an excellent linear relationship.