3D Glasses

 

A polarized 3D system utilizes polarization glasses to create the effect of three-dimensional images by controlling the light that reaches each eye, a technique known as stereoscopy.

To display stereoscopic images and films, two images are superimposed on the same screen or display using different polarizing filters. Viewers wear inexpensive 3D glasses, each equipped with a polarizing filter for the left and right eye. These filters are set to different polarizations, ensuring that each eye receives only the corresponding image. This method generates a three-dimensional experience by showing the same scene from slightly different angles, each with its unique polarization. This system allows multiple viewers to enjoy the stereoscopic images simultaneously.

However, polarized 3D systems, along with other stereoscopic systems, often face the issue known as the Vergence-Accommodation Conflict.

Linearly polarised glasses

To create a stereoscopic motion picture, two images are superimposed on the same screen using orthogonal polarizing filters, typically set at 45 and 135 degrees. The viewer then dons linear polarized glasses, which contain corresponding orthogonal filters aligned with those of the projector. Each filter allows only light that matches its polarization to pass through while blocking light with perpendicular polarization. This setup ensures that each eye perceives only one of the projected images, thus creating the illusion of depth. However, linear polarized glasses require the viewer to keep their head level; any tilting of the glasses can cause the visual channels to overlap, resulting in a loss of the 3D effect. This restriction can make long viewing sessions uncomfortable, as head movement must be minimized to preserve the immersive experience.

Circularly polarized glasses

To create a stereoscopic motion picture, two images are superimposed on a single screen using circular polarizing filters of opposite handedness. The viewer then wears glasses equipped with analyzing filters—essentially reversed circular polarizers—also of opposite handedness. In this configuration, left-circularly polarized light is blocked by the right-handed analyzer, while right-circularly polarized light is obstructed by the left-handed analyzer. This approach achieves a visual experience akin to that of traditional stereoscopic viewing with linear polarized glasses, but with the added advantage that viewers can tilt their heads without losing left/right separation. However, this flexibility comes with a drawback: the fusion of stereoscopic images may be compromised due to the discrepancy between the alignment of the viewer's eye plane and the original camera angles.

As illustrated in the figure, the analyzing filters consist of a quarter-wave plate (QWP) and a linearly polarized filter (LPF). The QWP converts circularly polarized light into linearly polarized light, with the angle of polarization of the resulting light dependent on the handedness of the incoming circularly polarized light. In this example, left-handed circularly polarized light entering the analyzing filter is converted by the QWP into linearly polarized light aligned with the transmission axis of the LPF, allowing it to pass through. On the other hand, right-handed circularly polarized light would be transformed into linearly polarized light oriented along the LPF’s absorbing axis, which is perpendicular to the transmission axis, resulting in it being blocked.

By rotating either the QWP or the LPF by 90 degrees around an axis perpendicular to their surfaces (parallel to the light wave's direction of propagation), an analyzing filter can be created that blocks left-handed circularly polarized light instead of right-handed light. Importantly, rotating both the QWP and the LPF by the same angle does not alter the functionality of the analyzing filter.