How do naked-eye 3D LED screens trick your eyes?
Since 2020, naked-eye 3D screens have gradually entered the public eye. From the wave tank in Seoul, South Korea, to the spaceship in Chengdu Taikoo Li, and the tricolor cat in Tokyo Shinjuku, naked-eye 3D screens have attracted countless people from all over the world. Compared with traditional 3D displays that require glasses or helmets, naked-eye 3D screens, which can be viewed without any equipment, seem to have a natural advantage. However, behind the naked-eye 3D screen, is it technological advancement or a visual trick?
Human eye parallax/How to deceive the eyes to produce a 3D effect?
As early as 1839, British scientist Wheatstone was pondering a question - "Why is the world we observe three-dimensional?" After research, he found that because there is a distance of about 6.5 cm between human eyes, when observing three-dimensional objects, the perspectives are slightly different, which produces binocular parallax.
The left eye sees the left side, and the right eye sees the right side. There is a slight difference in the images seen. The object is imaged on the retina at the same time. The brain compares the two different "images" to distinguish the distance of the object, thus producing a three-dimensional effect.
The effect that causes this three-dimensional sensation is called "visual displacement." It is this visual displacement that allows us to distinguish the distance of objects and obtain a three-dimensional sense of depth.
When observing an object with both eyes simultaneously, each point on the object has an angle to both eyes. The closer the object is to the eyes, the larger the angle of each point on the object to the eyes, and the greater the visual displacement. The farther the object is from the eyes, the closer the lines of sight of the two eyes are to parallel, and the visual displacement is close to zero. It is difficult for us to judge the distance of the object, and we will not have a three-dimensional sense of it.
Looking at the stars at night, it feels like all the stars are on the same spherical surface, and it is difficult to distinguish the distance. This is the result of zero visual displacement.
Visual displacement is the basic principle of 3D movies producing a three-dimensional effect: during shooting, two cameras are used to shoot simultaneously, obtaining two synchronized images with differences. Then, polarized glasses are used to separate the content for the viewer's left and right eyes, so that the two eyes obtain different images for the left and right eyes respectively. In this way, there is a three-dimensional effect, and what is presented in the brain is the feeling of a 3D image.
Naked-eye 3D screens also utilize the characteristics of human eye parallax, projecting the pixels corresponding to the left and right eyes to the left and right eyes respectively, thus producing a three-dimensional image, allowing viewers to feel the three-dimensional effect at a specific angle.
How does "visual illusion" deceive the brain to produce a three-dimensional effect?
The three-dimensional effect of a plane image is caused by the "visual illusion" processed by the brain, or the brain supplements the three-dimensional effect. When the brain processes plane images, it will calculate the distance and spatial sense. If the image does not provide enough information, the brain will actively supplement the depth when trying to judge the spatial depth of the image.
Just as painters use the distance, size, shadow effects, and perspective relationships of objects in a two-dimensional image to construct a three-dimensional effect, making the brain misjudge the spatial sense and depth of the image, 3D video sources also use perspective and shadow relationships to expand and confuse spatial perception, causing visual illusions in the human eye, thus producing a realistic three-dimensional effect.
Most plane naked-eye 3D screen video sources use the visual illusion of significant frames. When the brain selects obvious frames as distance reference objects, the dynamic image suddenly blocks the "front" and "back" of the frames, or the contrast between far and near is highlighted, forming an illusion of brain distance judgment, thus producing a three-dimensional effect.
Most of the current popular naked-eye 3D screens are corner screens, which use two adjacent plane screens to present different sides of a three-dimensional object. They use spatial perspective and the imaging properties of two adjacent sides of a corner screen to create visual illusions of light and shadow, brightness and darkness, and reality and virtualness for the human eye, making the screen content appear three-dimensional.
Each 3D video source needs to be customized according to parameters such as screen shape, size, and viewing angle. First, the optimal viewing angle is determined, then video content conforming to the perspective principle is created according to the viewing angle, then the box layout diagram of the display screen is used for corner positioning, and finally, a video source that presents a three-dimensional effect at a specific angle is output.
Because the video source is created based on a specific angle to simulate the 3D effect, only by standing at a specific angle can you obtain the optimal viewing angle of the three-dimensional effect. If you are not standing at the optimal angle, the screen content will be deformed. This is why the shooting angles of most naked-eye 3D corner screens are the same, because only at a specific angle can you see the best 3D effect.
In order to achieve perfect integration of creative content and the real environment and create an immersive 3D experience, designers need to customize video sources that conform to the perspective principle according to the on-site installation scene of the display screen. The closer the boundaries of the video content are to the real scene, the more realistic the three-dimensional effect will be for the audience.
Hardware requirements and display effects of naked-eye 3D screens depend on screen hardware conditions
From the perspective of hardware devices, not all outdoor LED screens are suitable for naked-eye 3D effects. The display effect of naked-eye 3D screens has high requirements for screen quality, installation precision, and creative reality materials. To present better 3D video effects, LED screens must meet at least the following three requirements.
Seamless transition: The mainstream 3D large screens on the market are mainly corner screens and curved screens, and true seamless corner screens are preferred. Seamless transitions can better integrate two adjacent plane large screens, bringing a visual experience with stronger spatial sense and three-dimensionality.
High-definition images: Outdoor high-definition large screens have become the direction of development, and 8K resolution and small spacing are becoming mainstream, with spacing developing from the original P16, P10, P8 to P6, P3.9, and even P2.5. The smaller the spacing, the more delicate the screen display effect, and the more realistic the 3D effect.
Immersive effect: Compared with ordinary outdoor advertising screens, naked-eye 3D displays pursue more stable images and realistic colors. Excellent screen quality can present more image details and bring a more immersive visual experience. Impressive naked-eye 3D screens often have "three high" characteristics.
High refresh rate: 3840Hz and higher refresh rates ensure higher image stability;
High grayscale: 16bit (i.e., 65536 color changes) ensures more delicate color changes, avoiding color difference or discontinuity;
High contrast: The maximum brightness of 10000nits ensures that the image remains visible under direct sunlight and presents more details and purer colors.
Naked-eye 3D screen trends, domestic and foreign layout
At present, naked-eye 3D is mainly distributed in the CBD business districts of some large and medium-sized cities, achieving the purpose of attracting customers for commercial entities and creating city landmarks.
For cities, successfully integrating 3D content with local culture will bring huge traffic and exposure to the city, creating a popular check-in location.
With the popularity of naked-eye 3D screens worldwide, overseas markets also favor naked-eye 3D outdoor large screens. Naked-eye 3D large screens can be seen in countries such as the United States, the Netherlands, the Philippines, and Thailand. Compared with traditional LED screens, naked-eye 3D screens, which have built-in hotspots and traffic, are obviously more popular with customers and advertisers.
However, as more and more naked-eye 3D outdoor advertising cases appear and the screen content becomes homogenized, high-quality displays are the key to maintaining the popularity of naked-eye 3D screens, thus bringing continuous advertising benefits.