Technologies behind 3D projection
Currently, there are three different basic technologies for producing stereoscopic 3D images with projection systems.
The categories are “Active Systems” employing liquid crystal shutter glasses, “Passive Infitec Systems” utilizing color combing
filters and glasses, and “Passive Polarization” employing either linear or circular polarization filters and glasses.
All three of the above systems will require more projector light output power because the filters and eyewear can reduce the screen image brightness by up to eighty percent compared with the same projection system producing 2D images.
(No special type of projection screen required)
Active systems require a power source for both the projector lens shutters and the eyewear. The LCD shutter glasses are synchronized with the lens shutter which alternates between left and right eye discrete images creating the 3D illusion for the viewer. No special type of projection screen required.
Passive Infitec or SuperAnaglyph
Infitec stands for interference filter technology. Special interference filters in the glasses and in the projector form
the main item of technology and have given it this name.
The filters divide the visible color spectrum into six narrow bands - two in the red region, two in the green region, and
two in the blue region (called R1, R2, G1, G2, B1 and B2 for the purposes of this description). The R1, G1 and B1
bands are used for one eye image, and R2, G2, B2 for the other eye.
The human eye is largely insensitive to such fine spectral differences so this technique is able to generate full-color 3D images with only slight color differences between the two eyes. No special type of projection screen required.
Stewart Filmscreen front or rear projection material for 3D
Passive polarisation system
(Special projection screens required)
Linear and circular polarisation systems
Two images, left eye and right eye, are projected superimposed onto the screen through a set of polarized filters. The left
and right eyes are polarized in opposite directions.
The viewer wears eyeglasses which also contain a pair of polarizing filters. As each filter only passes the light which is
similarly polarized and at the same time, blocks the opposite polarized light, each eye only sees one of the
superimposed images and the 3D effect is achieved.
Linearly polarized glasses require the viewer to keep his head level, as tilting of the viewing filters will cause the images of the left and right channels to bleed over to the opposite channel. Circular Polarizing Systems allows the viewer to tilt their head without any image bleed from the opposite eye. For front projection, a Silver Screen is required so that polarization is preserved. For rear projection, only certain screen models allow for preservation of the polarization.
For front projection, a Silver Screen is required so that polarisation is preserved. For rear projection, only certain screen models allow for preservation of the polarisation.
Listed to the right are the Stewart Filmscreen materials that are ideal for passive
Front Projection Flexible:
Silver 3D (download product sheet)
Silver 5D (download product sheet)
- Reflections Active 170 3D (download product sheet)
Rear Projection Flexible:
Stewart Filmscreen has created the "4k+" symbol to represent a screen as being “4k (and more) ready”. Stewart screens have been used in in applications dealing in line pair resolution well in advance of 4k.
All current Stewart Filmscreens are capable of handling this resolution. However, not all screens are optimal for applications for which you would consider a 4k projector.