Active shutter 3D system

A shutter 3D system requires for viewing 3D images, shutter glasses (also LCD shutter glasses ). These special glasses have lenses that consist of two liquid crystal faces ( one each for the left and right eye ), which can be switched electronically between permeable and impermeable. This can be either the left or the right eye darken. For this, the left and right images on a monitor, television or on a screen is displayed alternately. From the glasses while only the appropriate image to the appropriate eye is synchronously transmitted. This enables stereoscopic vision, for example, for playing 3D movies.

History

The principle of operation of the shutter system goes back to the American engineer and inventor Laurens Hammond (1895-1973, known by his namesake electromagnetic organ), who had patented an electromechanical prototypes "Message View" in 1922 for the first time.

The present " electro- stereoscopic " LCD shutter glass system was patented in 1985 by Lenny Lipton and marketed by his company " Stereo Graphics" under the name " Crystal Eyes" initially in the commercial sector ( medical technology). In the cinema the same system works as " RealD " 3D projection with the " ZScreen " suffix before DLP projectors.

3D shutter glasses were offered in the 90's in the package with graphics cards, a well-known example is " ELSA ". On German television, the process was once used as a test in the ( long set ) BR- broadcast computers fail. For this purpose, a video was shot with two TV cameras in the studio. Over a vision mixer half image for the left and the other field was then used for the right eye. This home, the two images, the viewer could look in sync again, he needed a simple circuit with a photocell, which carried out the synchronous switching of the shutter glasses. In one field a white spot was to be displayed, the other field had a black spot. Without glasses, this area flickered then accordingly. A kit was available to corresponding with glasses on the market. A few dozen spectators took part at that time in the 1980s in the experiment. With a normal CRT television however you achieved with this method per eye only 25 frames per second (25 Hz), and thus it creates a flickering image. Even modern 3D shutter glasses have a larger LCD screen - the first glasses showed only a very limited image.

Technology

Projection

With this method, both images are sequentially projected onto the white canvas. So 48 images need to be brought to the big screen for a movie at 24 frames per second at the same time, which is no problem for modern projectors. To avoid flicker, higher frequencies are usually selected, each individual image is displayed several times. Advantages are the high color fidelity and usability of a normal screen and the independence of the head tilt of the beholder. In addition, such a system despite the higher cost of shutter glasses to a certain audience size more cost-effective because, unlike the polarization method is omitted neither a projector nor a second polarizing filter for the projectors a metallized screen are still required and the synchronization overhead.

In 3D -ready home theater projector (most DLP projectors ) is the HDMI 1.3 connection is generally supplied with a 120 Hz 3D video signal from a 3D -compatible PC graphics card and projected as 2x60 Hz 3D video sequentially in time. In addition to matching 3D shutter (eg NVIDIA 3D Vision with its own USB infrared transmitter ) you can possibly use inexpensive so-called "DLP -Link" shutter glasses. Only 3D projectors with HDMI 1.4a connector can be fed directly with 3D HD signals from a 3D Blu -ray players, HD broadcasts.

Compatible Monitors

Flat screens that operate at a frequency of 60 Hz, are not suitable for use with shutter glasses. For shutter glasses a monitor frequency of 100 Hz is regarded as minimum as effectively halved by the method of the frequency, so each eye gets only 50 frames per second are shown. This is for static images, in particular texts, strong flickering in motion pictures such as games or videos but this does not fall more heavily on. In both cases, however, occurs in a short time, a fatigue of the eyes is a, the lower the frequency, the stronger the eyes are charged. Therefore, usually a frequency of 120 to 160 Hz is recommended, depending on the available hardware and screen resolution. This corresponds to 60 to almost eyesafe 80 Hz per eye. CRT screens reach 120-160 Hz, but they shine always for something that is noticeable at high frequencies at stronger streaks, which in turn tarnish the image quality. But Kurznachleuchtende CRT monitors could already be used in conjunction with LCD shutter glasses for 3D images and video or PC games before suitable flat screens were available.

Current 3D flat panel displays and DLP projectors for 3D HDTV ( 3D ready) work with 120 Hz or 96 Hz frame rate and short pixel dwell times, resulting in 60 Hz frame rate per eye for the synchronously connected to LCD shutter glasses.

Since the lenses of most LC shutter glasses are polarized, this function only when the direction of polarization is the same at LCD monitors with TFT Monitor. This is not the case, the lenses of the spectacles to be rotated by 90 °. Furthermore, need shutter glasses in conjunction with a TFT or plasma monitor a slightly different timing than on a CRT monitor, so that they function properly. The problem of " ghosting " (ie, optical crosstalk from the left to the right image channel uu ) arises mainly when the response time of the monitor is greater than 10 ms. That is true of modern 3D monitors and projectors hardly the case. The shortest response time, that is, almost no " ghosting ", offering DLP projectors and TVs.

Glasses synchronization

Earlier shutter glasses were cable operated (newer low-cost models, there are still ), modern shutter glasses work via infrared controller (eg Nvidia " 3D Vision" ). An infrared transmitter on the monitor or in addition to the movie screen then radiates from the sync signals. Since the shutter require relatively little power, the glasses together with IR receiver can be powered by a button cell. An operating with Bluetooth wireless technology synchronization method was introduced in 2011 by Samsung and should be undertaken in addition to infrared in a planned for 2012, device- independent standard for shutter glass control because previous systems were often not compatible with each other.

DLP -Link

Another method of synchronization, the White pulse method "DLP -Link" dar. between the individual images, a white flash is projected that man does not perceive by the compatible DLP Link glasses. DLP -Link shutter glasses can use them to synchronize with the projector. In 3D shutter technology in conjunction with DLP projectors come ghosting ( in a good synchronization) almost no longer on. Unlike solutions that require an IR emitter, DLP -Link has the advantage that it is directly synchronized with the screen image and not on the playback device. Disadvantage: Some glasses but have a very bright scenes, perceptual disturbances of the white flash, thereby catching due to flicker. Remedy, however, can create a reduction in the brightness of the playback device. There are also very cheap shutter glasses from the Far East that does not suppress the white flash and therefore can not be a true black.