Operation of circular polarizing film
A circular polarizing film is a film whose active layer consists of a polarizer. The circular polarizer only transmits a light wave whose plane of polarization rotates. Depending on the direction of rotation, we distinguish between right-handed circular polarization or left-handed circular polarization.
The most important property of the circular polarizing film is its ability to block light polarized during the formation of light reflections. A reflection is a linearly polarized light wave; the circular polarizing film only transmits light with a rotating plane of polarization, so it does not transmit reflected light. It can be said that the circular polarizer is always “perpendicular” to linearly polarized light, regardless of the film’s orientation.
Here we see a huge advantage of circular polarizing film over linear polarization. A linear polarizer must be precisely set perpendicular to the wave’s polarization to attenuate it. The circular polarizer works in any position.
If you want to remove really large light reflections, only a circular polarizing film is able to handle them.
Film illustrating the behavior of circular polarizing film.
In the film, we see how the circular polarizing film can completely suppress a strong light reflection coming from a lamp shining from a short distance directly onto a flat surface. Without the film, it is impossible to see the background; the circular polarizing film allows viewing the correct image.
The film also shows that with circular polarizing film, the direction of polarization does not matter when we want to remove light reflections. The operation of the film with right-handed circular polarization is the same as with left-handed circular polarization.