Calibration method for dual-tilt-axis tool based on image thresholding of skew tool influence function

Modern subaperture technologies mostly use the five-axis machine to follow the normal of state-of-the-art surfaces, such as aspheric, off-axis surfaces. The dual-tilt-axis tool has been widely used in optical manufacture to change the orientation of the tool. The initial tilt positions of the tool play an important role in the symmetry of tool influence function (TIF). The tilt angle errors may cause a skew TIF. We discussed the self-developed machine and its TIF models with different motion modes. Next, the effect of tilt angle errors, include spinning axis tilt error and revolution axis tilt error, was analyzed based on our self-developed polishing machine. Symmetric TIF will distort and form a skew TIF due to the angle error. There was a linear relationship between the eccentric ratio of the skew TIF and the angle error. In the experimental study, an initial adjustment was performed by utilizing a dial gauge, and then the TIF result showed that there were still some angle errors. We presented an image thresholding calibration method based on skew TIF to solve the tilt angle errors. After the new calibration, the following compared experiment got a fine symmetric, and Gauss-like TIF, and proved the validity of the proposed model and calibration method.