3D glasses
A 3D glasses is a special glasses , which in some stereoscopic method ( 3D photo , 3D film ) is required to the spatial depth effect to make them visible.
When projecting 3D films or printing 3D images, the human brain absolutely needs two images to create a spatial impression, one for the left and one for the right eye, which were recorded from two different perspectives or positions. These images must arrive in the brain for evaluation at the same time, but separately for each eye, so that the spatial impression can arise from them. The primary function of the 3D glasses is based on filtering, so that each eye only perceives the corresponding stereoscopic half-image for the left or right eye.
Color filter glasses (anaglyph glasses)
In the anaglyph process, the image is separated using color filters. The right and left fields are colored in complementary colors. The 3D cinema films of the 1950s were very often projected with the polarization technique, but later copied using the cheaper red-green process. At that time, the 3D glasses still contained the red filter in front of the left eye, the green in front of the right. This traditional arrangement of the filter colors is still considered standard for some.
In the late 1970s, Stephen Gibson significantly improved color anaglyph technology with his patented "Deep Vision" system that uses different filter colors: red in front of the right eye and cyan in front of the left eye. With these glasses, the perception of brightness (thanks to the new cyan color) is more even and less tiring for the eyes. The cyan-red combination is also optically superior to the red-green combination, since a colored image impression is partially preserved.
The Danish company "ColorCode 3-D" offers its own color filter glasses system with the filter colors yellow / orange (left) and blue (right). This system allows the color red to be included in the design of the 3D image.
Since 2007 the Californian company "TrioScopics" has been supplementing the range of inexpensive color filter techniques with the filter colors green (left) and magenta (right). This color filter technique is particularly suitable for screen display and is used for some 3D films that have appeared on DVDs and BDs .
Interference filter glasses
The process developed by the German company “Infitec” (“interference filter technology”), which is used in some digital 3D cinemas as “Dolby 3D”, works in an apparently color-neutral manner. Here, the basic colors of the images for the left and right eyes are reduced to different, overlap-free wavelength ranges. This method is only suitable for projections, but not for printing 3D images. It also requires a video processor that changes the color components of the left and right view in order to compensate for the color falsifications that are inherent in this process. This video processor is built into most projectors.
Pulfrich glasses
So-called "Pulfrich glasses" with light / dark filters (e.g. "Nuoptix"), use the "Pulfrich effect" for a 3D impression when tracking shots from the side. For example, the RTL television program Tutti Frutti made it very popular in the early 1990s. The Pulfrich method is not a real stereoscopic representation, as the image is only recorded with a single camera. The two perspectives for the left and right eye come about through the darkened spectacle lens, which triggers the Pulfrich effect. The darkened view is passed on to the brain with a time delay through slow processing, so that two views from different perspectives (but also at different times) form the impression of the room in moving recordings. This process can only be used to a very limited extent, because some requirements must be met for it to work as a 3D process at all. The camera or the objects must always (fundamentally and continuously) carry out a constant, slow, exclusively horizontal movement. If only one of these conditions is broken, no more 3D effect occurs.
ChromaDepth glasses
American Paper Optics' ChromaDepth process is based on the fact that colors are refracted to different degrees in a prism . The ChromaDepth glasses contain special viewing foils, which consist of microscopic prisms. As a result, light rays are deflected differently depending on the color. The light rays hit the eye in different places. However, since the brain assumes straight rays of light, the impression arises that the different colors come from different points of view. The brain thus creates the spatial impression (3D effect) from this difference. The main advantage of this technology is that you can view ChromaDepth images without glasses (i.e. two-dimensionally) without any problems - there are no annoying double images. In addition, ChromaDepth images can be rotated as desired without losing the 3D effect. However, the colors can only be selected to a limited extent because they contain the depth information of the image. If you change the color of an object, then its perceived distance also changes. This means that a red object always comes before z. B. green or blue objects.
Polarizing glasses
With the colored spatial image projection , the two separate images are emitted using polarized light . If a front projection is used, i.e. the viewer and the projector are on the same side of the screen, then the projections are made onto a metalized screen that is able to reflect the polarized light back. With a rear projection, the screen stands between the viewer and the projector and has to let the polarized light through. The different images reach the screen through two different projectors or lenses. It is also possible to use only one projector if the images are projected alternately through a filter with changing polarization (called Z-screen in RealD projections). In the case of 4K projectors, both partial images (in 2K ) can be separated again in one image by a beam splitter lying one above the other (Sony 4k 3D projections). Current 3D cinema projections also use polarization technology in most cases. For details of the technology used in IMAX cinemas, see IMAX 3D .
The glasses required also consist of two polarization filters which, depending on the polarization method, only allow the “appropriately” polarized light of the corresponding view to pass through, so that each eye only receives “its” image. In the first heyday of 3D film in the 1950s, most 3D cinema films were projected in black and white and color using this method. Many films were later copied to the more cost-effective red-green process.
With polarization processes, a distinction must be made between different processes and their orientations. There are two groups of polarization methods: linear and circular. The two methods are not compatible with each other. Another decisive factor within the process is how the polarizing filters are aligned.
LCD shutter glasses
So-called 3D shutter glasses with two controllable LCD glasses are used for use on a computer monitor , in many 3D TV sets and in some 3D cinemas . The screen alternates between the left and right fields. The liquid crystals of the glasses are now synchronously switched to transparent and opaque alternately with the rhythm of the 3D image and thus enable the three-dimensional effect of the healthy viewer due to the perspective shift of the two stereo 3D partial images.
Prismatic glasses
A number of methods also use the effect that prisms deflect the beam path. For example, B. the stereo viewing device SSG1b, also known under the name KMQ since the 1980s, this effect. Primarily for books and posters where color accuracy and simplicity are important. But it could be used earlier on the screen or for projection with a few viewers. However, the user must maintain the appropriate distance to the picture and keep his head permanently horizontal. Otherwise the lines of sight of both eyes will not coincide with the two partial images which are arranged one below the other. Hence the English name of the process: Over-Under . These restrictions are to be lifted in the future by an OpenHardware or OpenSource project called openKMQ for working on computers.
3D video glasses
In order to present different images to the two eyes and thus to be able to create a spatial perception, so-called 3D video glasses have been used in the recent past. Two individual displays in special glasses deliver the images. Carl Zeiss AG was a pioneer with its cinemizer. Advantages of these systems: The image is displayed sharply and is not changed in color. The technology is simple, so that many people can use the necessary software. Disadvantages of these systems: Usually the glasses are quite difficult to wear and have to be supplied with electricity.
Overview of 3D cinema projections and 3D glasses used
| Procedure | Dolby 3D | XpanD 3D (formerly: nuVision) | Sony RealD | Master Image | 3D in the 80s / IMAX | Anaglyph method (1950s-1970s) |
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| Glasses technology | Passive: interference filter | Active: shutter glasses | Passive: polarizing filter (0 ° / 0 ° circular) | Passive: polarizing filter (0 ° / 0 ° circular) | Passive: polarizing filter (linear - / + 45 ° occasionally: 0 ° / 90 °) |
Passive: color filter |
| glasses | Rental glasses | Rental glasses | reusable | reusable | Rental glasses | Disposable glasses |
| Weight of the glasses | 42 grams (old model) ?? Grams (model from 2011) |
71 grams (old model) 56 grams (X103 Infinity) |
22 grams 17 grams (new model) 16 grams (children) 7 grams (clip for glasses wearers) |
30 grams (old model) 25 grams (new model) 27 grams (washable) 13 grams (2015 model) |
5 grams | 5 grams |
| canvas | normal | normal | silver | silver | silver | normal |
| Projector (s) | 1 | 1 | 1/2 | 1 | 1/2 | 1 |
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See also
- Autostereoscopy
- Binocular
- View master
- Head-Mounted Display (video glasses)
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- ↑ Helmut Jorke, Markus Fritz: "INFITEC - A NEW STEREOSCOPIC VISUALIZATION TOOL BY WAVELENGTH MULTIPLEX IMAGING" ( Memento from February 25, 2011 in the Internet Archive ) (PDF; 966 kB)
