Polarized light mode
Light polarization systems are used in commercial theaters and other high-end applications. These methods provide high quality 3D experience in commercial cinema, while the popularity of digital projectors makes the 3D effect even better. In a polarized light system, light from one or more projections passes through a polarization filter so that all the light waves oscillate in the same direction.
Special filters on the glasses worn by the audience allow only light passing through one of the glasses. If you've ever seen a shutter, you've got the idea that you can clearly see the window from a certain angle, and from another angle your vision will be obscured. Using different polarization directions for both eyes, two separate images can be projected, one image being used for one eye, resulting in a sense of depth.
At present, there are two different polarized light systems in the commercial 3D projection field. One version uses two projectors, each with its own polarization filter, projecting the left eye and the right eye image, respectively. The system is used for IMAX 3D playback. Another system, known as RealD, uses a projector and a fast switching single polarizer to accomplish the same thing. The system switches very quickly between the left eye image and the right eye image, and the polarization filter also switches with the left and right eye images in the clockwise and counterclockwise polarization directions. Again, the polarizing glasses allow the viewer's eyes to see only the information that belongs to each eye.
Advantages of polarized light 3D
Colour. Compared with the stereo photograph system, the color is more accurate when using polarized light system. Although there are some light losses from the lenses, the colors are closer to their original values. In view of the fact that the lenses of the lenses are virtually without any color, color correction is easier for programs used for polarized light systems. Especially the color of the skin, in a polarized light system, looks more authentic.
Passive glasses. Like the stereo photo 3D, polarized light 3D uses passive glasses, inexpensive and contains no electrical components. Unlike the stereoscopic 3D, the frames of polarized glasses are usually made of plastic, making them more durable and reusable than the 3D frames of paper frames.
String. Compared with stereoscopic 3D systems, polarized 3D systems have lower line incidence. Due to polarized light, the left eye image can hardly be seen by the right eye (and vice versa). If you head to the two direction too badly, then use the left and right polarized system such as IMAX will lose the 3D effect, but unless you sleep to her shoulder, it will not be a problem.
The disadvantage of polarized light 3D
Brightness loss. Compared with a 2D system, all single projector 3D systems have significant brightness reduction. Not for physicist ProjectorCentral readers, refers to the brightness from a surface (in this example, the screen) at a specified angle (i.e., toward the audience perspective glasses) reflected light. This is different from illumination, which is the measurement of light in a unit area of a surface, usually in lumen per square meter, usually published in our projector evaluation.
In all 3D systems except for stereoscopic 3D, this loss is due to the rapid switching necessary for displaying different images in the left eye and the right eye. At any given moment of watching a 3D movie, one eye sees a projected image, and the other does not see anything. In this way, each eye sees only half the light reflected by the screen, which immediately causes at least 50% of the brightness to be reduced. I say "at least" because the polarizer and 3D glasses do not have the perfect light efficiency. Polarizers essentially allow only a portion of the total amount of light of the projector to reach the screen. 3D glasses also have some further brightness loss. The end result is that the brightness of the picture is much lower than that of the 2D movie from the same projector.
This is actually one of the major advantages of using dual projector systems. Each eye benefits from the full brightness output of a projector, although the brightness loss of the polarizer and 3D glasses still exists. The end result is a much brighter picture, and all the others are the same. Finally, this sentence is important because it is difficult to achieve the same in all other aspects. The most common commercial implementation of the dual projector system is IMAX, which uses a much larger screen than most RealD theaters. The projector used varies greatly in lumen output range. Polarizer and 3D glasses are also very different in efficiency. There are too many variables in determining which system is better, but each of the two systems has its advantages.
Costly. Although the 3D glasses are not expensive, other parts of the system are not. Requires at least one high-end digital projector and matched with the special processing equipment to manage synchronization, at least one polarized light filter, and a silver screen (the traditional white curtain can not keep the polarization of light). The dual projector system, of course, requires two projectors and two sets of polarizers.
Interference filter 3D
Another 3D implementation for commercial cinema uses a technology called interference filter, which is manufactured by a German company, Infitec. The system uses a projector and does not require a silver screen. The projector Infitec 3D compatible with a special color wheel is inserted between the bulb and the imaging device, the main color is separated into different segments. Imagine: red, green, blue, and now red, 1, red, 2, green, 1, green, 2, blue, 1, blue, 2. Special interference filter glasses allow the left eye to see only clips labeled "1", while the right eye only sees clips labeled "2". The 3D glasses use additional filters to correct the perception of color, so the eye sees as close to the original film as possible. You may have seen the technology: it's called Dolby 3D (Dolby 3D) in a commercial theater.
The advantage of interference filter 3D
Passive glasses. Passive glasses are a common element of 3D systems designed for commercial theaters and other large venues because of their ease of use and relatively low cost. Interference filter 3D glasses are more difficult to manufacture than polarized glasses. As a result, they are manufactured with high durability. The lens is made of glass, and even has a strong frame for lanyard hole anti-theft device. They are more resistant to scratches and wear than the fragile polarized lenses.
No silver screen is required. Decades ago, silver plated screens were used in all movies, but they fell out of favor. Compared to the silver screen, the white screen has a larger viewing angle than the silver screen, so when the projector becomes bright enough to fully brighten a white screen, the silver screen is out of the stage.
The disadvantages of the silver plated screen still exist: brightness falls significantly for spectators sitting off the center. In a commercial theater, this includes a considerable audience. Since the interference filter 3D does not require the use of polarized light, the silver screen is not needed, thereby improving the viewing experience of each viewer. People sitting on both sides of the cinema can get more consistent screen illumination, and all viewers can get the same color fidelity as non 3D movies.
The disadvantage of interference filter 3D
Brightness loss. Compared to any single projector 3D display mode, the 2D display on the same projector will suffer significant brightness loss. This does not mean that single projector interference filters, 3D and polarized 3D systems always have the same brightness, or that a dual projector is always brighter than a single projector system. Single projector polarized light systems, interference filter systems, and shutter glasses systems share this common limitation.
Specialized equipment. It is possible to install a single projector polarized light system like RealD on a DLP cinema projector already used in many commercial theaters. This change does not require modifications to the projector itself. In view of the mechanism of Infitec 3D in the projector inside the theater or need to buy pre installed Infitec color wheel theater projector, or need to make a trained engineer will be installed to their existing internal color wheel DLP cinema projector.
Expensive glasses. The biggest advantage of passive glasses is that they don't cost much, so people might expect Infitec 3D glasses to be too expensive. Wrong. Much of the manufacturing cost of Infitec glasses lies in the lens itself - the glass must be coated many times to distinguish between different wavelengths. Dolby recently released a press conference on 3D glasses, announcing a wholesale price of $27.50 for each pair of glasses. This is obviously a huge expense for the cinema, so many procedures have been used to ensure that the cinema audience returns the 3D glasses. I've been to a Dolby 3D theater and asked for a photo ID in exchange for glasses.
LCD shutter glasses
LCD shutter glasses are the first high quality 3D implementation for home use. In systems using such glasses, video displays alternately display images of the right and left eye at very fast speeds up to 120 frames per second. The viewer wears an active LCD shutter lens that alternately blocks the left eye and the right eye. Just like the effect of the DLP color wheel, around the turn happened so fast that your brain will be two images together, resulting in a single image of the sense of depth 3D.
The advantages of shutter glasses
Colour. Although the shutter 3D glasses are various, most of them have lenses without obvious staining, which makes them have the same color accuracy as polarized light. We have been using the shutter 3D glasses to have green staining, but other brands of glasses we have seen are not dyed.
String. As far as the line is concerned, the LCD glasses may be the best of all 3D methods, because the eye that is not used is actively shielded by the shutter mechanism. Earlier versions have the problem of ghosting, that is, a part of the previous image will remain on the screen after the new image appears. Newer, faster display technologies have completely eliminated this image error.
Relatively cheap. The price of 3D projectors and TV sets is already very low. Today, a projector that can display 3D is available for only $800. Although there are other costs, such as computers equipped with high-end graphics cards and 3D glasses per viewer, they are still affordable for home applications with only a small audience.
The disadvantage of shutter glasses
Active glasses. This is the most important difference between LCD shutter glasses and other types of systems: the mechanism that controls which eye sees what is embedded in the glasses is not determined by the program content or projector. LCD shutter glasses are good for a small, reliable adult audience, but it has several weaknesses. Compared to other technologies, the glasses are expensive (at $100 to $150 per pair). The glasses are complex in structure, with batteries, electrical components, and fragile LCD lenses. If you hit the ground, be trampled, or run out of batteries, you'll ruin the viewer's 3D experience. And, if you have a bunch of friends want to enjoy your home 3D Super Bowl (Note: the United States occupation Football League finals), to provide everyone a pair of 3D glasses are too expensive.
Synchronization. The active shutter system needs a way to synchronize the shutter action of the 3D glasses with the contents displayed on the screen. Some systems use infrared emitters. TI's system for projectors and televisions is called DLP Link, which uses sync pulses that are included in the projected image. Although the two implementations use different pulse information sources, the pulse itself is the same.
The left eye pulse is different from the right eye pulse, which is why all 3D glasses synchronized to one particular TV set are synchronized with one another. But the projector doesn't know which frame belongs to that eye, which poses an interesting problem. These pulses may turn over so that one eye sees the picture belonging to the other. In other words, the left eye pulse is associated with the right eye image. This is called "pseudo stereoscopic effect" and this phenomenon makes you feel quite uneasy when you first experience it. The effect is a strange scene inside and outside the image, as if you were looking at a sunken 3D image from the wrong side. This phenomenon often occurs, so manufacturers have corresponding countermeasures that can be remedied by switching the monitor, the computer graphics card, or an option of the software itself. Still, it's not as simple and reliable as any other type of system.
Twinkle。 Some people reported blinking when using shutter glasses. Blinking is the effect of an action that occurs when the refresh rate is insufficient. Indeed, in view of only half the refresh rate per eye, the shutter glasses used by projectors must be very fast. For this purpose, the current implementation uses a refresh rate of at least 120Hz to render images of 60 frames per second for each eye. We haven't encountered any blinking in the ProjectorCentral test, so we can't comment on the popularity or severity of the phenomenon.
Brightness loss. The shutter glasses system uses a single projector that switches quickly to display different left and right eye images, so, as with other single projector systems, there is a reduction of at least 50% of the brightness output compared to the 2D. Glasses also reduce visual brightness. Although not all glasses are the same, the model we have tested reduces visual brightness by about 60%, regardless of the display or the program itself. The advantage is that the glasses also reduce the black level, thus dramatically increasing the contrast.
