Fig. 1. (a) Experiment setup: 4f optical system. (b) The orientation of liquid crystal molecules in the grating films and their modulation of light. (c) Illustration of polarization dependency of PG.

Fig. 2. (a) Physical picture of the object and the PG. (b) Visual effect of PG under natural light and linearly polarized light. (c) Image of PG under polarization microscope.

Fig. 3. (a)–(d) The effect of two liquid crystal PGs superimposed on each other. (e)–(h) Pictures of a light beam without an analyzer. (i)–(l) The edge information patterns after the filter.

Fig. 4. (a), (c), and (e) The complete pattern of “HNU” that carries edge information without the polarizer after lens 2. (b), (d), and (f) The final edge pattern of “HNU” filtered by the polarizer and captured by CCD.