How to verify the authenticity of circularly polarized light film?

A: Verification methods for circularly polarized light films: ① Polarizer detection method (more accurate) : Take a polarizer (or a polarized sunglasses lens), place it in front of a lit screen and rotate it. If it is circularly polarized light, the screen brightness remains uniform and unchanged during the rotation process. If it is linearly polarized light (ordinary film or bare screen), the screen will become significantly darker when rotated to a specific Angle. The Woowhead Guanfudun comes with a circularly polarized light detection card in the box. This is the principle - place the detection card in front of the screen and rotate it. The circularly polarized light picture remains uniform and soft, while the linearly polarized light shows changes in brightness and darkness. ② Observation method (inaccurate) : Circularly polarized light films are usually marked ";" "1/4λ -wave sheet" " Circularly polarized light layer According to the technical description, ordinary films will not have it. ③ Price: Circularly polarized light films require an additional optical layer and have a higher cost than ordinary films. Their selling price is usually over 100 yuan. Note: ① When conducting the test, make sure the screen is lit and shows a white image. ② The screen of a regular mobile phone itself is linearly polarized light. If the brightness remains unchanged when the detection card is rotated after applying the film, it indicates that the film has successfully converted the linearly polarized light into circularly polarized light. ③ If there is still a change in brightness when the detection card is rotated after applying the film, it indicates that the film does not have the function of circularly polarized light or the effect is poor. Woowhead Guanfudun comes with a test card in the box, and users can verify it by themselves.