Phase measuring deflectometry based on calibration of the entrance pupil center of the camera lens

Abstract

A camera calibration method for phase measuring deflectometry (PMD) based on the entrance pupil center (EPC) of the camera lens is proposed. In our method, the position of the entrance pupil of the camera lens is first measured; next the absolute coordinates of the EPC are calibrated by using a reference flat and an external stop that is mounted in front of the camera lens; then the EPC as the camera coordinates is used for PMD. The feasibility of the proposed method is verified by simulation. The surface shapes of a planar optical element and a planar window glass are separately measured in our experiments, and a subwavelength accuracy level is achieved. Meanwhile, the effects of the camera lens with different aperture settings on captured images are investigated (including exposure time, image contrast, and measurement accuracy). The experimental results show that the exposure time required declines with the decrease in the f-number, and the measurement accuracy is higher than others when the f-numbers are changed from f/5.6 to f/11.

Supplementary document for Superposition Fabry-Perot filter array for computational hyperspectral camera - 6273458.pdf

“…The SFP hyperspectral camera can work on a larger angle, such as 10 • . However, we choose a maximum 5 • working angle (system f-number is 5.71), because we have investigated the f-number of commonly used optical systems [3][4][5] and believe that this angle is suitable for most systems.…”

3D reconstruction method of defocused images based on optical system analysis

“…In order to increase the imaging depth of field, we usually use some techniques, including reducing the internal stop size of the lens [6] , wavefront coding [7] , using a telecentric lens, and deconvolution [8] . All of these techniques can be equivalent to reducing PSF.…”