There are various types of 3D glasses on the market. On the one hand, the typical two-color glasses, known as anaglyphic and, on the other, passive and active glasses.

3D movies, such as Avatar, that viewers have been able to enjoy in theaters are generally viewed with passive glasses, while the new 3D television requires active glasses. What differences are there between one and the other?

The first glasses to be able to see in 3D were the anaglyphic glasses, the typical glasses with lenses of two different colors. This difference in the coloration of the glasses serves to filter the colors that the eyes receive differently. As a Sony technician explains during the presentation of 3D television, "they should not always be red and green, because what is really important is that the colors are completely opposite within the color wheel." Thus, it could be that one lens was yellow and the other purple, or one blue and one orange.

The evolution of technology and the improvement of the quality of three-dimensional images have led to the development of new display systems. This is the case of polarized glasses. In the cinema, two projectors polarize the light from a different angle for each eye, so that the glasses decode these images to provide more quality.

The problem is that this system cannot be applied to televisions, since the filter built into the screen only allows the reproduction of half the content and the brightness. Also, as pointed out by Panasonic, "another of the disadvantages of this format is the limited viewing angle, since users must keep their heads up to avoid visual fatigue caused by double contouring."

Active 3D glasses

It is for them that experts and researchers have had to resort to other techniques to make 3D reach conventional televisions.

Active glasses are the solution. This type of glasses incorporates an infrared sensor that synchronizes the images that alternate on the screen so that the left eye only sees the left perspective and the right only, you guessed, the right. Actually, the infrared sensor simply synchronizes the image to be displayed for each eye, the true causes of the image being displayed or not being are the LCD crystals that contain the glasses and the active shutter that rapidly alternates the images on the screen. The blinking and image change from one eye to the other occurs at such a speed that the brain is unable to notice the change and interprets it as a single three-dimensional image.