The Xiaomi Mi Transparent TV was released on August 11. It comes with a 55-inch OLED screen, which supports a 120Hz refresh rate, and costs 49,999 yuan ($7226).
Immediately after the launch, Xiaomi officially issued a document to sort out the technical ideas and principles of this transparent TV.
Take away everything that is not necessary, and make sure what you leave behind must be transparent
The shape of the TV looks like a ‘black box’. There are many internal parts that hinder transparency. So the idea of making the TV transparent is simply ‘remove all non-essentials, and leave everything transparent’.
The first is the back panel of the TV. The back panel of the TV is almost black. There are various components inside: T-CON board, power supply board, main board, etc…. These are non-essential items that prevent the TV from becoming transparent. Remove all!
But ‘removing’ does not mean ‘throwing away’. These components need to be taken out of the backplane and reintegrated to form an external host, and then establish a connection with the screen through a cable to make it work normally.
Have other products used it?
Such an option has actually been partially adopted on the Mi Mural TV, that is, remove the heavy and redundant ‘baggage’ on the TV back panel, and externally install the host part on the original back panel. The placement plan provides a prerequisite for TV transparency.
The option of separating the host and the screen of the Xiaomi Mi Transparent TV is similar to this, but more complicated.
After eliminating the redundant physical components, you can now focus your attention on the screen itself. At present, the screen display options widely used in TVs are LCD (liquid crystal) and OLED. Both of them can be made transparent. But OLED is self-luminous. So it has the inherent advantages of making transparent TV.
Because LCD needs backlight to display the image, this also determines that even if LCD is made into a transparent TV, it will appear as a box. This is obviously contrary to the aesthetic pursuit of modern TVs.
In addition, due to the existence of the polarizer, its transparency cannot be made higher. So no matter it’s the appearance or the display effect, the LCD (liquid crystal) transparent solution can only be passed off.
2 million transparent sub-pixels, such as louvered ‘magic modified’ OLED screen
How to make the OLED screen achieve transparent display? Here is the introduction of common ‘blinds’ in life to facilitate everyone’s understanding.
A blind with a pattern: if the leaves are completely closed, you can see the complete picture. But at the same time, the scenery behind is completely blocked by the closed blinds.
But if you unscrew the blinds at an angle, you will find that although the picture on the blades is split, it does not affect the overall look and feel. And you can still clearly identify the pattern content on the blinds. Moreover, the unscrewed shutters make the outdoor scenery show through. So the picture and the scenery coexist.
And this is almost the same as the principle of the Xiaomi Mi Transparent TV.
In analogy, blinds and windows form a whole transparent screen. The display area is the ‘blade’ of the blinds, and the transparent area is the ‘gap between the blades’ after unscrewing.
How this helps?
Although the image cannot be displayed in the transparent area, if the ‘gap between the blades’ is properly controlled and made small enough that the human eye cannot detect it, the display area composed of each blade can show a clear and complete pattern. And the ‘gap between the leaves’ also reveals the scenery behind, achieving a visually magical transparent effect.
As we can see from the pixel composition of the transparent OLED screen in the figure below, in addition to the WRGB 4 sub-pixels in the conventional OLED screen, nearly 50% of the ‘transparent sub-pixels’ have been added to the transparent OLED pixels. So the ‘transparent sub-pixel + WRGB sub-pixel’ make up a single pixel of the transparent OLED screen. The pixels of this structure have 1920X1080=2073600 on this 55-inch transparent screen.
These sufficient WRGB sub-pixels form the ‘leaf’ in the blind principle and are responsible for displaying images. In addition, sufficient transparent sub-pixels form the ‘gap between the blades’ in the blind theory and are responsible for transparency.
Because nearly half of the total number of pixels is completely transparent as a whole, such a transparent area is large enough and evenly distributed. So it achieves an extremely high transparency from the visual effect, and the other half of the display area composed of WRGB. It has more than half the number of pixels to display images. So the display level is also high.
In summary, the entire OLED screen has completely become a piece of ‘glass’ with high transparency. It constitutes the most important part of the entire transparent TV. And because of the advantages of high resolution and self-luminous OLED, it also maintains a very high display level.
The principle is clear, but it is only a small step away from mass production
Based on the above realization of the transparency of the OLED screen, it is theoretically possible to manufacture a concept phone based on a transparent TV. But Xiaomi wants to do more crazy things, to mass-produce this extremely futuristic product.
If a TV wants to be mass-produced, it needs to go through a series of tests and certifications. This is tantamount to weighting the index on the difficulty of manufacturing a concept machine.
How to give life to a piece of ‘transparent glass’? This needs to test the manufacturer’s OBM capabilities. OBM is called OLED Basic Module. It refers to the entire process of R&D, system testing, and manufacturing of OLED modules by TV manufacturers. It is the ‘entry for judging whether a company can independently develop OLED. In the field of transparent OLED TV, Xiaomi is the only one in China.’
OBM includes many aspects, such as the surface tempering of the screen. The Xiaomi Mi Transparent TV adopts physical tempering, that is, a whole piece of tempered glass is bonded to the screen. This improves the resistance to pressure of the screen and eliminates the potential safety hazard of broken screen.
In addition, the Xiaomi TV uses UV glue for bonding. This further reduces the thickness of the screen, while also improving the bonding accuracy. And the overall look and feel of the screen is further improved.
The host part
The external host mentioned above is different from the ordinary split TV. In order to ensure the overall look and feel, the Xiaomi Mi Transparent TV creatively integrates the host and the screen, and has passed the extremely high structural strength test.
In the host part, Xiaomi engineers have also done challenging technical research around heat dissipation and EMI.
Since the mainframe of Xiaomi’s transparent OLED TV is designed to be stacked up and down, the power supply as a ‘big heat generator’ is equivalent to directly baking the motherboard. In order to radiate this part of the heat, Xiaomi’s engineers have done a lot of effort.
While adding a heat shield between the two, the internal heat dissipation system has also been re-customized. Many tiny heat dissipation holes are designed around the host. Through the delicate layout and specially designed internal heat dissipation system, every inch of the internal space is used to the extreme. The heat becomes uniform convection in the shape of the host, which overcomes the heat dissipation problem in a small space.
In addition, a step is specially designed on the radiator of the motherboard chip. It is extended and bridged to the shell beam. So the shell can be used cleverly to help the motherboard heat dissipation. In addition, high temperature resistant components are also adopted in the selection of components. The components further ensure the efficient and stable operation of the motherboard.
The screen structure of the transparent glass of the Xiaomi Mi Transparent TV combined with the ultra-narrow metal frame, the signal line runs through the structure of the metal closed base. So the tightly stacked structure inside will have its special EMI. Thus, the work of electronic products will cause interference to other electronic products around.
The Xiaomi Mi Transparent TV took corresponding measures to solve targeted solutions at the early stage of design. Also, its experiments were conducted in the later stage of trial mass production. This proved that these measures effectively suppressed the radiation spillage formed by most of the product structure.
Mass production of the Xiaomi Mi Transparent TV seems to be an impossible task. But based on years of accumulation in TV technology, Xiaomi finally presented such a magical product to the world. Also, Xiaomi has also become ‘the world’s first company to produce transparent OLED.