The difference between 2D and 3D is that the former is a flat display, while the latter is a three-dimensional display. From 2D to 3D with glasses, and then to naked-eye 3D technology, all of these indicate the progress of technology. As naked-eye 3D technology becomes more and more mature, there are more and more cases where LED display manufacturers use 3D technology on the basis of LED large screens. So, how is the 3D special effect of LED large screens achieved? What are its four principles?
Four principles of LED large screen 3D special effects: LED large screen naked eye 3D technology uses the principle of parallax. When the audience watches the picture, they only need to provide two sets of images with slightly staggered shooting positions, one for the left eye and the other for the right eye, and they can see a set of three-dimensional pictures. The four principles of 3D special effects LED electronic large screen are light separation, color separation, time division and grating.
Beam Splitting Method
The beam splitting method of naked eye 3D special effect LED large screen technology is to use the directionality of light to wear polarizing filters on the left and right eyes, or polarizers to filter out all light except the polarized light at a certain angle, so that part of the image light enters only the left eye, and part of the image light enters only the right eye. Two sets of images are output respectively through the polarized light in two directions on the LED large screen, so as to achieve 3D effect display. Viewers need to wear polarized glasses to watch. The left and right lenses of the glasses can respectively let the polarized light in the directions perpendicular to each other pass through, so that the left and right eyes can see the three-dimensional effect and form a 3D special effect.
Spectroscopic technology is used on large LED screens to solve the problem of polarized light. Only by viewing two different polarized images through the left and right eyes and letting the polarized light pass through the left and right lenses can the two different images enter the left and right eyes respectively, and then synthesize an image with a three-dimensional effect through the visual system in the human brain.
Spectroscopic technology has certain disadvantages when applied to large LED screens, because large LED screens are self-luminous technology of LED diodes, so it is difficult to output two sets of images in two directions of polarization. In addition, the images displayed on large LED screens are superimposed on each other, making it difficult to separate the images. Therefore, polarization technology is generally not used on large LED screens.
Color Separation Method
Color separation technology is to use the principle of chromatic aberration 3D display technology to make three kinds of color separation glasses (complementary color glasses) of red and blue, red and green, and brown and blue realize the alternation and superposition of images viewed by both eyes, and realize stereoscopic imaging by viewing different images with both eyes. It uses the principle that the two lenses of color separation glasses are different, and the film source requirements are the same as the requirements for glasses.
For example, red and blue glasses require red and blue film sources, red and green glasses require red and green film sources, and brown and blue glasses require brown and blue film sources, among which red and blue film sources are dominant.
Although the color separation method is relatively simple, low-cost, and can easily convert 2D into 3D images, this color separation technology is obviously not suitable for large LED electronic screens, because large LED electronic screens are packaged with three primary color LED lamp beads. If this technology is used, the image brightness and color reproduction of the viewer’s eyes will be reduced.
If the input information received by the left and right eyes cannot be stable and consistent during viewing, although the brain can reassemble the information viewed by both eyes in the later stage, it will cause fatigue of the optic nerve, so the color separation glasses cannot be used for a long time. In addition, the large LED screen has an advantage in brightness, so this method is the simpler 3D special effect LED display among the four principles.
Time-Sharing Method
The time-sharing method is a 3D special effect principle developed based on the characteristics of LED large screens. It plays two sets of images alternately in a very short time. That is, when the LED large screen is refreshed for the first time, the image that enters the viewer’s left eye is played, and the viewer’s right eye is covered by the glasses worn by the viewer. The left and right directions are swapped at the next refresh. These two actions are exchanged continuously, that is, the two sets of shutter images are switched at high speed, and a continuous 3D image is finally formed by using the visual persistence characteristics of the human eye and the synthesis function of the brain.
At present, the widely used glasses are liquid crystal shutter glasses that can continuously block the left and right eyes at high speed. This method has high requirements for the synchronization of the LED large screen and the liquid crystal shutter glasses, and requires the addition of dedicated wireless transmission equipment to synchronize the LED display screen and the liquid crystal shutter glasses at the same time.
Due to the visual persistence characteristics of the human eye, the time-sharing technology does not lose brightness. At the same time, it relies on the high refresh rate capability of the LED large screen and does not require major changes to the original LED display system. Only the signal synchronization equipment needs to be added to achieve 3D special effects. Its equipment purchase and maintenance costs are low, and it is currently the most commonly used solution among the four principles of 3D special effects.
Grating Method
Grating technology is based on the principle of parallax barrier to arrange images alternately. They first pass through a long and narrow vertical grating and then are viewed by both eyes. Since the vertical images entering the left and right eyes are separated by the parallax barrier, the images captured by the left and right eyes have a slight deviation, and finally a three-dimensional image is formed in the brain.
The specific operation method is to achieve a 3D display effect by installing parallel grids on the large LED screen to divide the screen longitudinally into vertical bars. The bars are staggered to display the left and right eye images, such as odd-numbered bars are displayed on the left eye image, and even-numbered bars are displayed on the right eye image. Then, a parallax barrier composed of vertical bars is set between the screen and the audience. By blocking the line of sight other than the intersection of the two eyes’ line of sight, the left and right eyes see different images, thereby achieving a three-dimensional display effect.
However, the grating method also has limitations in achieving stereoscopic display. If the viewer’s position changes, the position of the parallax barrier must also change. To solve this problem, multi-viewpoint technology is generally used. This method does not affect the viewing effect and is relatively simple to implement. This grating method uses TN glass to cover the LED display screen, and controls whether to generate grating by powering on, so that both 2D and 3D images can be displayed on one display screen.
The disadvantage of grating technology is that if dual-viewpoint technology is used, the horizontal pixels of the display screen corresponding to the viewer will be halved. If multi-viewpoint technology is used, the horizontal pixels will become 1/N. Therefore, using this method, in order to achieve better image display quality, the display horizontal pixels must be doubled, and the cost will also increase.
The above is a brief introduction to the four principles of LED large-screen 3D special effects, namely color separation, light separation, time sharing and grating. Among them, color separation and light separation cannot meet the display effect requirements of 3D special effect LED display screens. Although grating can eliminate the need to wear glasses, it has certain requirements on the position of the viewer. Time sharing technology is more suitable for the requirements of LED large-screen 3D special effects in terms of display effect and cost performance.
