An active shutter 3D system (a.k.a. alternate frame sequencing, alternate image, AI, alternating field, field sequential or eclipse method) is a technique of displaying stereoscopic 3D images. It works by only presenting the image intended for the left eye while blocking the right eye's view, then presenting the right-eye image while blocking the left eye, and repeating this so rapidly that the interruptions do not interfere with the perceived fusion of the two images into a single 3D image.
Modern active shutter 3D systems generally use liquid crystal shutter glasses (also called "LC shutter glasses" or "active shutter glasses"). Each eye's glass contains a liquid crystal layer which has the property of becoming opaque when voltage is applied, being otherwise transparent. The glasses are controlled by a timing signal that allows the glasses to alternately block one eye, and then the other, in synchronization with the refresh rate of the screen. The timing synchronization to the video equipment may be achieved via a wired signal, or wirelessly by either an infrared or radio frequency (e.g. Bluetooth, DLP link) transmitter. Historic systems also used spinning discs, for example the Teleview system.
Although virtually all ordinary unmodified video and computer systems can be used to display 3D by adding a plug-in interface and active shutter glasses, disturbing levels of flicker or ghosting may be apparent with systems or displays not designed for such use. The rate of alternation required to completely eliminate noticeable flicker depends on image brightness and other factors, but is typically well over 30 image pair cycles per second, the maximum possible with a 60 Hz display. A 120 Hz display, allowing 60 images per second per eye, is widely accepted as flicker-free.
Crosstalk is the leakage of frames between left eye and right eye. LCDs have exhibited this problem more often than plasma and DLP displays, due to slower pixel response time. LCDs that utilize a strobe backlight, such as nVidia's LightBoost, reduce crosstalk. This is done by turning off the backlight between refreshes, while waiting for the shutter glasses to switch eyes, and also for the LCD panel to finish pixel transitions.
In March 2011 Panasonic Corporation, together with XPAND 3D, have formulated the M-3DI Standard, which aims to provide industry-wide compatibility and standardization of LC Shutter Glasses. This movement aims to bring about compatibility among manufacturers of 3D TV, computer, notebook, home projection, and cinema with standardized LC shutter glasses that will work across all 3D hardware seamlessly. The current standard is Full HD 3D Glasses.
Field Sequential has been used in video games, VHS and VHD movies and is often referred to as HQFS for DVDs, these systems use wired or wireless LCS glasses.
The Sensio format was used with DVDs using wireless LCS glasses.
Each different active 3D shutter glasses implementation can operate in their own manufacturer-set frequency to match the refresh rate of the display or projector. Therefore, to achieve compatibility across different brands, certain glasses have been developed to be able to adjust to a broad range of frequencies.
The principle made its public debut remarkably early. In 1922, the Teleview 3-D system was installed in a single theater in New York City. Several short films and one feature-length film were shown by running left-eye and right-eye prints in a pair of interlocked projectors with their shutters operating out of phase. Each seat in the auditorium was equipped with a viewing device containing a rapidly rotating mechanical shutter synchronized with the projector shutters. The system worked, but the expense of the installation and the unwieldiness of the viewers, which had to be supported on adjustable stands, confined its use to this one engagement.
In recent decades, the availability of lightweight optoelectronic shutters has led to an updated revival of this display method. Liquid crystal shutter glasses were first invented by Stephen McAllister of Evans and Sutherland Computer Corporation in the mid-1970s. The prototype had the LCDs mounted to a small cardboard box using duct tape. The glasses were never commercialized due to ghosting, but E&S was a very early adopter of third-party glasses such as the StereoGraphics CrystalEyes in the mid-1980s.
In 1985 3D VHD players became available in Japan from manufacturers such as Victor (JVC), National (Panasonic), and Sharp. Other units were available for field sequential VHS tapes including the Realeyes 3D. A few kits were made available to watch field sequential DVDs. Sensio released their own format which was higher quality than the High Quality Field Sequential (HQFS) DVDs.
The method of alternating frames can be used to render modern 3D games into true 3D, although a similar method involving alternate fields has been used to give a 3D illusion on consoles as old as the Master System and Family Computer. Special software or hardware is used generate two channels of images, offset from each other to create the stereoscopic effect. High frame rates (typically ~100fps) are required to produce seamless graphics, as the perceived frame rate will be half the actual rate (each eye sees only half the total number of frames). Again, LCD shutter glasses synchronized with the graphics chip complete the effect.
In 1982, Sega's arcade video game SubRoc-3D came with a special 3D eyepiece, which was a viewer with spinning discs to alternate left and right images to the player's eye from a single monitor. The game's active shutter 3D system was jointly developed by Sega with Matsushita (now Panasonic).
In 1984, Milton Bradley released the 3D Imager, a primitive form of active shutter glasses that used a motorized rotating disc with transparencies as physical shutters, for the Vectrex. Although bulky and crude, they used the same basic principle of rapidly alternating imagery that modern active shutter glasses still use.
Sega released the SegaScope 3-D for the Master System in 1987, where it was the first known electronic device to use LCD Active Shutter glasses. Only eight 3D compatible games were ever released. Nintendo's Famicom also featured a similar Famicom 3D System, which was an LCD shutter headset, released in 1987 only for Japan.
In 1993 Pioneer released the LaserActive system which had a bay for various "PAC's" such as the Mega LD PAC and LD-ROM² PAC. The unit was 3D capable with the addition of the LaserActive 3D goggles (GOL-1) and the adapter (ADP-1).
While the 3D hardware for these earlier video game systems is almost entirely in the hands of collectors it is still possible to play the games in 3D using emulators, for example using a Sega Dreamcast with a Sega Master System emulator in conjunction with a CRT television and a 3D system like the one found in The Ultimate 3-D Collection.
In 1999–2000, a number of companies created stereoscopic LC shutter glasses kits for the Windows PCs which worked with application and games written for Direct3D and OpenGL 3D graphics APIs. These kits only worked with CRT computer displays and employed either VGA pass-through, VESA Stereo or proprietary interface for left–right synchronization.
The most prominent example was the ELSA Revelator glasses, which worked exclusively in Nvidia cards through a proprietary interface based on VESA Stereo. Nvidia later bought the technology and used it in its stereo driver for Windows.
The glasses kits came with driver software which intercepted API calls and effectively rendering the two views in sequence; this technique required twice the performance from the graphic card, so a high-end device was needed. Visual glitches were common, as many 3D game engines relied on 2D effects which were rendered at the incorrect depth, causing disorientation for the viewer. Very few CRT displays were able to support a 120 Hz refresh rate at common gaming resolutions of the time, so high-end CRT display was required for a flicker-free image; and even with a capable CRT monitor, many users reported flickering and headaches.
These CRT kits were entirely incompatible with common LCD monitors which had very high pixel response times, unlike CRT displays. Moreover, the display market swiftly shifted to LCD monitors and most display makers ceased production of CRT monitors in early 2000s, which meant that PC glasses kits shortly fell into disuse and were reduced to a very niche market, requiring a purchase of a used high-end, big diagonal CRT monitor.
SplitFish EyeFX 3D was a stereo 3D shutter glasses kit for the Sony PlayStation 2 released in 2005; it only supported standard-definition CRT TVs. The accessory included a pass-through cable for the PS2 gamepad; when activated, the attached accessory would issue a sequence of rapidly alternating left–right movement commands to the console, producing a kind of "wiggle stereoscopy" effect additionally aided by the wired LC shutter glasses which worked in sync with these movements. The kit arrived too late in the product cycle of the console when it was effectively replaced by the PlayStation 3, and only a few games were supported, so it was largely ignored by gamers.
The USB-based Nvidia 3D Vision kit released in 2008 supports CRT monitors capable of 100, 110, or 120 Hz refresh rates, as well as 120 Hz LCD monitors.
There are many sources of low-cost 3D glasses. IO glasses are the most common glasses in this category. XpanD 3D is a manufacturer of shutter glasses, with over 1000 cinemas currently using XpanD glasses. With the release of this technology to the home-viewer market as of 2009, many other manufacturers are now developing their own LC shutter glasses, such as Unipolar International Limited, Accupix Co., Ltd, Panasonic, Samsung, and Sony.
Nvidia makes a 3D Vision kit for the PC; it comes with 3D shutter glasses, a transmitter, and special graphics driver software. While regular LCD monitors run at 60 Hz, a 120 Hz monitor is required to use 3D Vision.
Other well known providers of active 3D glasses include EStar America and Optoma. Both companies produce 3D Glasses compatible with a variety of technologies, including RF, DLP Link and Bluetooth.
These solutions utilize the inherent speed advantage of the Digital Micro-mirror Device (DMD) to sequentially generate a high refresh rate for the left and right views required for stereoscopic imaging.
DLP 3D technology uses the SmoothPicture wobulation algorithm and relies on the properties of modern 1080p60 DMD imagers. It effectively compacts two L/R views into a single frame by using a checkerboard pattern, only requiring a standard 1080p60 resolution for stereoscopic transmission to the TV. The claimed advantage of this solution is increased spatial resolution, unlike other methods which cut vertical or horizontal resolution in half.
The micromirrors are organized in a so-called "offset-diamond pixel layout" of 960×1080 micromirrors, rotated 45 degrees, with their center points placed in the center of "black" squares on the checkerboard. The DMD employs full-pixel wobulation to display the complete 1080p image as two half-resolution images in a fast sequence. The DMD operates at twice the refresh rate, i.e. 120 Hz, and the complete 1080p picture is displayed in two steps. On the first cadence, only half of the original 1080p60 image is displayed – the pixels that correspond to the "black" squares of the checkerboard pattern. On the second cadence, the DMD array is mechanically shifted (wobulated) by one pixel, so the micromirrors are now in a position previously occupied by the gaps, and another half of the image is displayed – this time, the pixels that correspond to the "white" squares.
A synchronization signal is then generated to synchronize the screen's refresh with LC shutter glasses worn by the viewer, using Texas Instruments' proprietary mechanism called DLP Link. DLP Link keeps sync by embedding briefly-flashed white frames during the display's blanking interval, which are picked up by the LC shutter glasses.
Plasma display panels are inherently high-speed devices as well, since they use pulse-width modulation to maintain the brightness of individual pixels, making them compatible with sequential method involving shutter glasses. Modern panels feature pixel driving frequency of up to 600 Hz and allow 10-bit to 12-bit color precision with 1024 to 4096 gradations of brightness for each subpixel.
Samsung Electronics launched 3D ready PDP TVs in 2008, a "PAVV Cannes 450" in Korea and PNAx450 in the UK and the US. The sets utilize the same checkerboard pattern compression scheme as their DLP TVs, though only at the native resolution of 1360×768 pixels and not at HDTV standard 720p, making them only usable with a PC.
Matsushita Electric (Panasonic) prototyped the "3D Full-HD Plasma Theater System" on CES 2008. The system is a combination of a 103-inch PDP TV, a Blu-ray Disc player and shutter glasses. The new system transmits 1080i60 interlaced images for both right and left eyes, and the video is stored on 50-gigabyte Blu-ray using the MPEG-4 AVC/H.264 compression Multiview Video Coding extension.
Formerly, LCDs were not very suitable for stereoscopic 3D due to slow pixel response time. Liquid crystal displays have traditionally been slow to change from one polarization state to another. Users of early 1990s laptops are familiar with the smearing and blurring that occurs when something moves too fast for the LCD to keep up.
LCD technology is not usually rated by frames per second but rather the time it takes to transition from one pixel color value to another pixel color value. Normally, a 120 Hz refresh is displayed for a full 1/120 second (8.33 milliseconds) due to sample-and-hold, regardless of how quickly an LCD can complete pixel transitions. Recently, it became possible to hide pixel transitions from being seen, using strobe backlight technology, by turning off the backlight between refreshes, to reduce crosstalk. Newer LCD televisions, including high end Sony and Samsung 3D TVs, now utilize a strobed backlight or scanning backlight to reduce 3D crosstalk during shutter glasses operation.
In vision therapy of amblyopia and of intermittent central suppression, liquid crystal devices have been used for purposes of enhanced occlusion therapy. In this scenario, the amblyopic patient wears electronically programmable liquid crystal glasses or goggles for continuously for several hours during regular everyday activities. Wearing the device encourages or forces the patient to use both eyes alternatingly, similar to eye patching, but rapidly alternating in time. The aim is to circumvent the patient's tendency to suppress the field of view of the weaker eye and to train the patient's capacity for binocular vision. The goggles mostly feature a much slower flicker rate than the more well-known active shutter 3D glasses.
3D television (3DTV) is television that conveys depth perception to the viewer by employing techniques such as stereoscopic display, multi-view display, 2D-plus-depth, or any other form of 3D display. Most modern 3D television sets use an active shutter 3D system or a polarized 3D system, and some are autostereoscopic without the need of glasses. As of 2018, most 3D TV sets and services are no longer available.AMD HD3D
HD3D is AMD's stereoscopic 3D API.HD3D exposes a quad buffer for game and software developers, allowing native 3D.
An open HD3D SDK is available, although, for now, only DirectX 9, 10 and 11 are supported.Support for HDMI-3D-, DisplayPort-3D- and DVI-3D-displays is included in the latest AMD Catalyst.
AMD's Quad-Buffer API is supported by the following GPUs on following AMD products: Radeon HD 5000 Series, Radeon HD 6000 Series, and Radeon HD 7000 Series and A-Series APUs.Bubblegram
A bubblegram (also known as laser crystal, 3D crystal engraving or vitrography) is a solid block of glass or transparent plastic that has been exposed to laser beams to generate three-dimensional designs inside. The image is composed of many small points of fracture or other visible deformations and appears to float inside the block.ChromaDepth
Chromadepth is a patented system from the company Chromatek (a subsidiary of American Paper Optics since 2002) that produces a stereoscopic effect based upon differences in the diffraction of color through a special prism-like holographic film fitted into glasses. Chromadepth glasses purposely exacerbate chromatic aberration and give the illusion of colors taking up different positions in space, with red being in front, and blue being behind. This works particularly well with the sky, sea or grass as a background, and redder objects in the foreground.Correspondence problem
The correspondence problem refers to the problem of ascertaining which parts of one image correspond to which parts of another image, where differences are due to movement of the camera, the elapse of time, and/or movement of objects in the photos.Dolby 3D
Dolby 3D (formerly known as Dolby 3D Digital Cinema) is a marketing name for a system from Dolby Laboratories, Inc. to show three-dimensional motion pictures in a digital cinema.Integral imaging
Integral imaging is an autostereoscopic and multiscopic three-dimensional imaging technique that captures and reproduces a light field by using a two-dimensional array of microlenses, sometimes called a fly's-eye lens, normally without the aid of a larger overall objective or viewing lens. In capture mode, each microlens allows an image of the subject as seen from the viewpoint of that lens's location to be acquired. In reproduction mode, each microlens allows each observing eye to see only the area of the associated micro-image containing the portion of the subject that would have been visible through that space from that eye's location. The optical geometry can perhaps be visualized more easily by substituting pinholes for the microlenses, as has actually been done for some demonstrations and special applications.
The result is a visual reproduction complete with all significant depth cues, including parallax in all directions, perspective that changes with the position and distance of the observer, and, if the lenses are small enough and the images of sufficient quality, the cue of accommodation — the adjustments of eye focus required to clearly see objects at different distances. Unlike the voxels in a true volumetric display, the image points perceived through the microlens array are virtual and have only a subjective location in space, allowing a scene of infinite depth to be displayed without resorting to an auxiliary large magnifying lens or mirror.
Integral imaging was partly inspired by barrier grid autostereograms and in turn partly inspired lenticular printing.MasterImage 3D
MasterImage 3D is a company that develops stereoscopic 3D systems for theaters, and auto-stereoscopic 3D displays for mobile devices.Nvidia 3D Vision
3D Vision (previously GeForce 3D Vision) is a stereoscopic gaming kit from Nvidia which consists of LC shutter glasses and driver software which enables stereoscopic vision for any Direct3D game, with various degrees of compatibility. There have been many examples of shutter glasses. Electrically controlled mechanical shutter glasses date back to the middle of the last century. LCD shutter glasses appeared in the 1980s, one example of which is Sega's SegaScope. This was available for Sega's game console, the Master System. The NVIDIA 3D Vision gaming kit introduced in 2008 made this technology available for mainstream consumers and PC gamers.The kit is specially designed for 120 Hz LCD monitors but is compatible with CRT monitors (some of which may work at 1024×768×120 Hz and even higher refresh rates), DLP-projectors, 3LCD projectors and others. It requires a compatible graphics card from Nvidia (GeForce 200 series or later).Pseudoscope
A pseudoscope is a binocular optical instrument that reverses depth perception. It is used to study human stereoscopic perception. Objects viewed through it appear inside out, for example: a box on a floor would appear as a box shaped hole in the floor.
It typically uses sets of optical prisms, or periscopically arranged mirrors to swap the view of the left eye with that of the right eye.RealD 3D
RealD 3D is a digital stereoscopic projection technology made and sold by RealD. It is currently the most widely used technology for watching 3D films in theaters (cinemas). Worldwide, RealD 3D is installed in more than 26,500 auditoriums by approximately 1,200 exhibitors in 72 countries as of June 2015.Stereoautograph
The Stereoautograph is a complex opto-mechanical measurement instrument for the evaluation of analog or digital photograms. It is based on the stereoscopy effect by using two aero photos or two photograms of the topography or of buildings from different standpoints.
It was invented by Eduard von Orel in 1907.The photograms or photographic plates are oriented by measured passpoints in the field or on the building. This procedure can be carried out digitally (by methods of triangulation and projective geometry or iteratively (repeated angle corrections by congruent rays). The accuracy of modern autographs is about 0.001 mm.
Well known are the instruments of the companies Wild Heerbrugg (Leica), e.g. analog A7, B8 of the 1980s and the digital autographs beginning in the 1990s, or special instruments of Zeiss and Contraves.Stereoblindness
Stereoblindness (also stereo blindness) is the inability to see in 3D using stereopsis, or stereo vision, resulting in an inability to perceive stereoscopic depth by combining and comparing images from the two eyes.
Individuals with only one functioning eye always have this condition; the condition also results when two eyes do not function together properly.
Most stereoblind persons with two healthy eyes do employ binocular vision to some extent, albeit less than persons with normally developed eyesight. This was shown in a study in which stereoblind subjects were posed with the task of judging the direction of rotation of a simulated transparent cylinder: the subjects performed better when using two eyes than when using their preferred eye. They appeared to judge the direction of rotation from the images in each eye separately and then to combine these judgments, rather than relying on differences between the images in the two eyes. Also, purely binocular motion stimuli appear to influence stereoblind persons' sensation of self-motion. Furthermore, in some cases each eye can contribute to peripheral vision for one side of the field of view (see also monofixation syndrome).
However, there is an exception to this: those with a true congenital alternating squint. Those with true congenital alternating squints have two healthy eyes, and the ability to switch (by choice) between seeing with either eye. However, stereoscopic and three dimensional vision can never be achieved in this condition (attempts to train those with true congenital alternating squints into binocular vision results in double vision, which can be irreversible).Stereographer
A stereographer is a professional in the field of stereoscopy and visual effects using the art and techniques of stereo photography, 3D photography, or stereoscopic 3D film to create a visual perception of a 3-dimensional image from a flat surface.Stereoscopic Video Coding
3D video coding is one of the processing stages required to manifest stereoscopic content into a home. There are three techniques which are used to achieve stereoscopic video:
Color shifting (anaglyph)
Pixel subsampling (side-by-side, checkerboard, quincunx)
Enhanced video stream coding (2D+Delta, 2D+Metadata, 2D plus depth)Stereoscopic acuity
Stereoscopic acuity, also stereoacuity, is the smallest detectable depth difference that can be seen in binocular vision.Stereoscopic spectroscopy
Stereoscopic spectroscopy is a type of imaging spectroscopy that can extract a few spectral parameters over a complete image plane simultaneously. A stereoscopic spectrograph is similar to a normal spectrograph except that (A) it has no slit, and (B) multiple spectral orders (often including the non-dispersed zero order) are collected simultaneously. The individual images are blurred by the spectral information present in the original data. The images are recombined using stereoscopic algorithms similar to those used to find ground feature altitudes from parallax in aerial photography.
Stereoscopic spectroscopy is a special case of the more general field of tomographic spectroscopy. Both types of imaging use an analogy between the data space of imaging spectrographs and the conventional 3-space of the physical world. Each spectral order in the instrument produces an image plane analogous to the view from a camera with a particular look angle through the data space, and recombining the views allows recovery of (some aspects of) the spectrum at every location in the image.Stereoscopic video game
A stereoscopic video game (also S-3D video game) is a video game which uses stereoscopic technologies to create depth perception for the player by any form of stereo display. Such games should not to be confused with video games that use 3D game graphics on a mono screen, which give the illusion of depth only by monocular cues but not by binocular depth information.XpanD 3D
XPAND 3D developed active-shutter 3D solutions for multiple purposes. The company was founded by Maria Costeira and Ami Dror in 1995 as X6D Limited. The company deployed over 15,000 cinemas world wide.