Stereoscopic display systems features , advantages and disadvantages

Stereoscopic display exhibits multi-angle to the audience & it is more intuitive , The stereoscope is the device for viewing stereo-graphic cards that contain two separate images which are printed side by side to create the illusion of a three-dimensional image , Stereo display ( also 3D display ) is the display device capable of conveying the depth perception to the viewer .

Stereoscopic display systems

The real 3D displays display the image in three full dimensions , The most notable difference from the stereoscopic displays with only two 2D offset images is that the observer’s head & eyes movement will increase the information about the 3-dimensional objects being displayed .

Stereoscopic display can create the illusion of 3-D when displayed , Volumetric displays can create the 3-D computer graphics image , but fail to offer many visual depth cues of overlap , Discrete parallax can create 3-D images with all of the depth cues , but they are limited by achievable resolution .

Stereo displays present the offset images that are displayed separately to the left & right eye , Both of these 2D offset images are combined in the brain to give the perception of 3D depth , The presentation of dual 2D images is different from displaying an image in three full dimensions .

The accurate term “stereoscopic” is more cumbersome than the common misnomer “3D”, Although most stereoscopic displays do not qualify as real 3D displays , all real 3D display are also stereoscopic displays because they meet a lower criteria as well , Stereoscopic technology offers a different image to the viewer’s left & right eyes .

The following are some of the technical details in some of stereoscopic systems that have been developed , Each of these display technologies can be seen to have limitations , whether the location of the viewer , cumbersome or unsightly equipment or great cost , The display of artifact-free 3D images remains difficult .

Side-by-side images

The traditional stereoscopic photography consists of creating a 3D illusion starting from a pair of 2D images ,  The easiest way to enhance depth perception in the brain is to offer the eyes of the viewer with two different images , representing two perspectives of the same object , with a minor deviation exactly equal to the perspectives that both eyes naturally receive in the binocular vision .

The eyestrain & distortion are to be avoided , When the picture contains no object at infinite distance , such as the horizon or the cloud , the pictures should be spaced correspondingly closer together , The side-by-side method is simple to create , but it can be difficult or uncomfortable to view without optical aids .

Transparency viewers

Pairs of stereo views printed on the transparent base are viewed by transmitted light , One advantage of transparency viewing is the opportunity for a wider , more realistic dynamic range than is practical with the prints on an opaque base , another is that a wider field of view may be presented since the images , being illuminated from the rear , may be placed much closer to the lenses .

The user wears the helmet or the glasses with two small LCD or OLED displays with magnifying lenses , one for each eye , The technology can be used to show stereo films , images or games , Head-mounted displays may be coupled with head-tracking devices , allowing the user to look around the virtual world by moving their head , that eliminate the need for a separate controller .

Owing to rapid advancements in the computer graphics & the continuing miniaturization of video and other equipment  , these devices are beginning to become available at more reasonable cost , Head-mounted or wearable glasses are used to view a see-through image imposed upon the real world view , to create what is called an augmented reality .

This is done by reflecting the video images via the reflective mirrors , The recent development in holographic-waveguide or waveguide-based optics allows the stereoscopic images to be superimposed on real world without the uses of bulky reflective mirror .

Head-mounted projection displays

Head-mounted projection displays (HMPD) is similar to head-mounted displays but with the images projected to & displayed on the retro-reflective screen , The advantage of this technology over head-mounted display is that the focusing & vergence issues didn’t require fixing with the corrective eye lenses , For the image generation , Pico-projectors is used instead of LCD or OLED screen .

Anaglyph 3D

Anaglyph 3D is the archetypal 3D glasses , It is similar to the red/green & red/blue lenses that are used to view early anaglyph films ,  The two images are superimposed in the additive light setting through two filters , one red & one cyan , In a subtractive light setting , the two images are printed in the same complementary colors on the white paper .

The glasses with colored filters in each eye separate the appropriate images by canceling the filter color out & rendering the complementary color black , compensating technique , It is commonly known as Anachrome , It uses a slightly more transparent cyan filter in the patented glasses associated with the technique , The process reconfigures the typical anaglyph image to have less parallax .

Color-code 3-D is an alternative to the usual red & cyan filter system of anaglyph  , The patented anaglyph system that was invented to present an anaglyph image in conjunction with the NTSC television standard , in which the red channel is compromised , Color-code uses the complementary colors of yellow & dark blue on screen ,The colors of the glasses’ lenses are amber & dark blue .

Polarization 3D systems

Polarization systems resemble the sunglasses , RealD circular polarized glasses are the standard for theatrical releases & theme park attractions , To present the stereoscopic picture , two images are projected superimposed onto the same screen through different polarizing filters , The viewer wears the eyeglasses that contain a pair of polarizing filters oriented differently .

As each filter passes only that the light that is polarized & blocks the light polarized differently , each eye sees a different image , This is used to produce a three-dimensional effect by projecting the same scene into both eyes , but depicted from slightly different perspectives .

The circular polarization offers a benefit over the linear polarization , The viewer does not need to have his head upright & aligned with the screen for the polarization to work properly , With the linear polarization , turning glasses sideways causes the filters to go out of alignment with the screen filters causing the image to fade & for every eye to see the opposite frame easily .

For the circular polarization , The polarizing effect works regardless of how the viewer’s head is aligned with the screen such as tilted sideways or even upside down , The left eye will still only see the image intended for it , and vice versa , without fading or cross-talk .

Polarized light reflected from the ordinary motion picture screen loses most of its polarization , So , an expensive silver screen or aluminized screen with negligible polarization loss has to be used , All types of polarization will result in a darkening of displayed image & poorer contrast compared to non-3D images .

The light from the lamps is emitted as a random collection of polarizations , while the polarization filter only passes the fraction of light , So , the screen image is darker , This darkening can be compensated by increasing the brightness of the projector light source .

When the initial polarization filter is inserted between the lamp & the image generation element , the light intensity striking the image element is not any higher than normal without the polarizing filter , and the overall image contrast transmitted to the screen is not affected .

Active shutter 3D system

In the eclipse method , Pair of LCD shutter glasses used to view XpanD 3D films , The thick frames conceal the electronics & batteries , The shutter blocks the light from each eye when the converse eye’s image is projected on the screen , The display alternates between left & right images , and opens & closes the shutters in the glasses or viewer in synchronization with the images on the screen , This was the basis of the Teleview system .

The variation on the eclipse method is used in LCD shutter glasses , The glasses containing the liquid crystal that will let the light through in synchronization with the images on the cinema , television or the computer screen , by using the concept of alternate-frame sequencing .

It is used by nVidia , XpanD 3D & earlier IMAX systems , The drawback of this method is the need for each person viewing to wear expensive , electronic glasses which must be synchronized with the display system using the wireless signal or attached wire .

However these systems do not require a silver screen for the projected images , Shutter-glasses are heavier than most polarized glasses , though lighter models are no heavier than some sunglasses or deluxe polarized glasses .

Liquid crystal light valves work by rotating the light between two polarizing filters , Due to these internal polarizers , LCD shutter-glasses darken the display image of any LCD , plasma , or projector image source , So , The images appear dimmer & contrast is lower than for normal non-3D viewing , for some types of displays which are very bright with poor grayish black levels , LCD shutter glasses may improve the image quality .

Interference filter technology

Dolby 3D uses specific wavelengths of red , green & blue for the right eye , and different wavelengths of red , green & blue for the left eye , The eyeglasses that filter out very specific wavelengths allow the wearer to see the 3D image .

Interference filter technology eliminates the expensive silver screens required for polarized systems such as RealD , which is the most common 3D display system in the theaters , It requires much more expensive glasses than the polarized systems , It is known as spectral comb filtering or wavelength multiplex visualization .

The recently introduced Omega 3D/Panavision 3D system also uses this technology , The use of more spectral bands per eye eliminates the need to color process image , required by the Dolby system , Dividing the visible spectrum between the eyes gives the viewer a more relaxed feel as the light energy & color balance is nearly 50-50 .

Like the Dolby system , the Omega system can be used with white or silver screens , But it can be used with either film or digital projectors , unlike the Dolby filters that are only used on the digital system with a color correcting processor , Omega/Panavision system also claims that their glasses are cheaper to manufacture than those used by Dolby .

Autostereoscopy

The glasses are not necessary to see the stereoscopic image , Lenticular lens & parallax barrier technologies involve imposing two (or more) images on the same sheet , in narrow , alternating strips & using the screen that either blocks one of the two images’ strips ( parallax barriers) or uses equally narrow lenses to bend the strips of image & make it appear to fill the entire image (lenticular prints) .

To produce the stereoscopic effect , the person should be positioned so that one eye sees one of the two images & the other sees the other , Both images are projected onto a high-gain , corrugated screen that reflects the light at acute angles , To see the stereoscopic image , the viewer should sit within a very narrow angle that is perpendicular to the screen .

While its use in the theatrical presentations has been rather limited , lenticular has been widely used for a variety of novelty items & has been used in the amateur 3D photography , Recent use contains the Fujifilm FinePix Real 3D with an autostereoscopic display , The other examples for this technology contain the autostereoscopic LCD displays on the monitors , the notebooks , TVs , mobile phones & gaming devices , such as the Nintendo 3DS .

Stereoscopy

The random dot autostereogram encodes a 3D scene which can be seen with proper viewing technique , The autostereogram is a single-image stereogram (SIS) , designed to create the visual illusion of a three-dimensional (3D) scene from a two-dimensional image in the human brain , In order to perceive 3D shapes in these autostereograms .

Prismatic glasses make cross-viewing easier as well as over/under-viewing possible, examples include the KMQ viewer , Wiggle stereoscopy is an image display technique achieved by quickly alternating display of left & right sides of a stereogram , Found in animated GIF format on the web .

Volumetric 3D display

Volumetric displays use some physical mechanism to display the points of light within a volume , Such displays use voxels instead of pixels , Volumetric displays include multiplanar displays , which have multiple display planes stacked up & rotating panel displays , where a rotating panel sweeps out a volume .

Holographic displays

The holographic display is the display technology that has the ability to offer all four eye mechanism , the binocular disparity , the motion parallax , the accommodation and the convergence , The 3D objects can be viewed without wearing any special glasses and no visual fatigue will be caused to the human eyes .

Integral imaging

The integral imaging is the autostereoscopic or multiscopic 3D display , So , it displays the 3D image without the use of special glasses on the part of the viewer , It achieves this by placing an array of micro-lenses (similar to a lenticular lens) in front of the image .

Each lens looks different depending on viewing angle , So , rather than displaying a 2D image that looks the same from every direction , it reproduces the 4D light field , creating stereo images that exhibit parallax when the viewer moves .

Compressive Light Field Displays

The new display technology called compressive light field is being developed , These prototype displays use layered LCD panels & compression algorithms at the time of display , The designs contain dual & multilayer devices that are driven by algorithms such as computed tomography & Non-negative matrix factorization and non-negative tensor factorization .

Stereoscopic display disadvantages

In Stereoscopic display systems that use a stereo input image pair to display 3D images , The images to be observed by left & right eyes are separately projected onto eyes , Viewer is required to wear special glasses such as anaglyphs , polarized or shutter glasses for separated reception of the left & right images on the eyes , Only the observer can see the display target object three-dimensionally .

It causes distortion in the scale of an image with the changes in viewing distance , Binocular parallax produces eye strain , binocular parallax & the focus adjustment cannot be realized exactly , If you use a series of fine vertical bars or lenses to direct the two images correctly to each eye , It causes Eye fatigue & Dizziness .

In the auto-stereoscopic three-dimensional display technology , The optical elements such as lenticular sheets or parallax barriers are attached to display the panels and they collect the left & right images displayed on the panel .