Improve 2 PSP dataset

I would introduce the data we uploaded as follows: These data are the experimental fringe images taken by the experimental platform we built. These phase-shifting fringe images are divided into the fringe images required for calibration and the fringe images for measuring the target to be measured. The required images for calibration are the fringe images taken at different heights (different heights are: 15mm, 25mm, 30mm and 40mm). The fringe images of the target to be measured include all the images required by the 16-step phase-shifting method, the complementary Gray code phase unwrapping method, the 2-step phase-shifting method and the '2+1' phase-shifting method.