Advantages and disadvantages of LED spherical display
Types of ball screens
1. Watermelon peel ball screen: The earliest ball screen on the market, commonly known as watermelon peel ball screen, is composed of watermelon peel-shaped PCB. The disadvantage is that the north and south poles (or north of 45° north latitude and south of 45° south latitude) cannot play images, so the picture utilization rate is too low.
2. Triangular spherical screen: The spherical screen composed of flat triangle PCB, commonly known as football screen, overcomes the shortcomings of the north and south poles of the watermelon peel ball screen that cannot play images, and the screen utilization rate is greatly improved. The disadvantage is that there are many types of PCBs, and the pixel point is limited by the honeycomb arrangement, and the point spacing cannot be less than 8.5mm. Therefore, software writing is also more troublesome, and the entry technology threshold is too high.
3. Six-sided panoramic spherical screen: It is a spherical screen composed of quadrilateral PCBs that has appeared recently, and is known as a six-sided spherical screen. It also has fewer types of PCB boards than football screens. The entry threshold is relatively low, the layout points are closer to the flat LED display, and the minimum point spacing is similar to that of the flat LED display, with little or no restrictions, so the effect is much better than the spherical screen composed of triangular PCBs. In terms of physical size, the entire spherical screen consists of 24 spherical surfaces of the same size. It can be put into the air box, and it is very convenient to disassemble and assemble, which is convenient for renters to use. In playback, it divides a ball screen into 6 identical pictures, namely up, down, left, right, front and back. Of course, different video sources can also be played individually or in combination through software. Therefore, its playback effect is far better than that of watermelon ball screen and football screen.
Several characteristics of LED ball screen
1. The appearance of LED ball screen is a product that appears in response to people’s demand for new and strange things. Early on, if a flat LED display appeared on the square, people would be surprised: such a big TV! , Now these “big TVs” can no longer satisfy people’s curiosity. If one day, a large outdoor ball screen with a diameter of 5 meters appears in the square, it will be a very popular product. Therefore, it is an unconventional and popular product.
2. Image playback and segmentation of the ball screen
The playing principle of the LED display is as follows: the system of the LED display (controller + computer) copies the image source played on the screen of the computer to the flat LED display.
And all the image sources in the world are flat. If you want to send the flat image source to the three-dimensional LED ball screen for display without processing, it is almost impossible. Fortunately, the ball is round, any one It is impossible for a single spectator to look at every corner of the LED spherical screen at the same time. He can only see a small part of the spherical surface, which is also related to the diameter of the spherical screen. The effective effect is only about one-sixth of the spherical surface area ( Due to the angle of view), five-sixths of them are invisible, because these five-sixths are on the back, left, right, above, and below the ball respectively. So it makes no sense to ask for a flat image source to be played on a spherical surface. The most suitable method is: 1. Play six different image sources in six areas of the sphere. 2. Play three different image sources in three areas of the sphere. 3. Play 2 image sources in 2 areas.
Resolution Design of Outdoor Ball Screen
Its design is the same as that of the flat LED display, that is, it is closely related to the viewing distance of the LED display. The general experience is that the viewing distance is P2.5, 2.5m away, and P6 is 6m away. If it is a P20 outdoor screen, then the viewing distance is 20m. Looking at it from the outside, it is also the same in actual use. This is a relatively vague concept, which is qualitative rather than quantitative. Its basis is expressed as follows:
The LED display screen is the same as the display screen of the computer. The images they display are composed of pixel points, and each pixel point is composed of red, green and blue color elements. There is a certain distance between pixels, which we call the point pitch PH. Assuming that the resolution of the computer display screen is 1024×768, the computer display screen has 1024 pixels in the horizontal direction and 768 pixels in the vertical direction, for a total of 786432 pixels. It is enough to express a very delicate image.
If the size of the computer display screen is 300mm in the vertical direction, then the pixel pitch on the computer display screen is PH=300/768=0.39mm.
PH is an important parameter for any digital display.
We have measured: the distance from the human eye to the computer display screen is D=450mm, then the angle between the two adjacent pixels and the human eye is θ,
Then there is the equation θ=Arctg0.29/450
If we put the computer screen 30,000mm away from the operator, and replace the computer screen with a spherical screen, the distance from the human eye to the spherical screen is 30,000mm. It can be seen that, in order to ensure that the perceptual amount of the image pixels remains unchanged (or the resolution remains unchanged), the included angle of θ should also remain unchanged. The only thing that needs to be changed is that the Ph has changed.
According to this equation: 0.29/450=Ph/30,000, from which Ph=26.04mm is obtained, that is, we will design the pixel pitch of the LED spherical screen to 25mm, at this time, the clarity of the spherical screen is sufficient, and is reasonable. At this time, the image clarity of the LED spherical screen we saw from 30 meters away was the same as what we saw in front of the computer.