Types of Stereoscopy
Different methods are used to produce stereoscopic effect. They can be classified into aided viewing or free viewing. Aided viewing is further divided into active and passive. Passive includes anaglyph and polarized glasses while active includes liquid crystal display (LCD) shutter glasses. Auto stereoscopic display, which does not require any filtering lenses, is known for free viewing.
- • Anaglyph: These are also called color-multiplexed displays. In anaglyphs, the two right and left images are filtered with colors like red and green, red and cyan, and green and magenta. The viewers have to wear the same filter lenses, which produce the effect of 3D depth in the images.
- • Polarized glasses: In polarized glasses, each lens is perpendicularly polarized. Therefore, the eyes see the image based on horizontal and vertical polarized light. The effect of 3D in polarized glasses is better than in anaglyphs.
- • LCD shutter glasses: Shutter glasses are electronically powered and one lens of the glass is active at a time. They are synchronized with the refresh rate of the screen. The display device displays only one image and this gets synced with the lens; therefore, the eyes are intended to see only particular frames that create the depth effect.
- • Auto stereoscopic displays: Auto stereo displays are a more advanced form of stereoscopy. In auto stereo, multiple views of an object are created from multiple cameras. Frames are presented on the screen with left and right views parallel to each other. The views are set in a way that left and right eyes can see their respective frames only. Parallax barrier and lenticular lens are two different modes of producing auto stereoscopic images.
From the aspects of entertainment and enjoyment, viewers find stereoscopic displays to be the best viewing device to give themselves a feeling of immersion. Viewers enjoy being a part of the movies they are watching as the things fly by them and motion looks more realistic. Even 3D stereoscopy has provided much entertainment to viewers but some viewers suffer from side effects of this technology. Viewers have reported that after watching 3D stereoscopic films they feel strain in their eyes and it gives them a headache. Based on the interviews of viewers, an article reports that 3D might be the cause of altered vision, confusion, and dizziness.3 It is also reported from an ophthalmologist that people with minor imbalance in their eyes can have a headache while watching 3D movies.4 These symptoms are derived from motion sickness, and the type of motion sickness that is caused by viewing is known as visually induced motion sickness (VIMS).