What is the function of polarization setting lenses L1 and L2?

Focus the large-angle diffracted beam to a small aperture and convert the condensed light into parallel plane polarized light.

1. The main function of the polarized light setting lens L1 is to focus the large-angle diffracted beam to a small aperture, which can be clearer.

2. The main function of the polarized light setting lens L2 is to change the condensed light into parallel plane polarized light, making judgment easier.