New project of a modified LCD monitor with very low electromagnetic emissions
Our research of solutions for having low electromagnetic emissions at the computer workplace has driven us to new ways of modifying the typical LCD monitors.
The solution under development has a different way to illuminate the LCD panel. Instead of placing small LEDs in place of the thin fluorescent tubes inside the original structure of the LCD module, now we are trying to put the LEDs directly behind the LCD panel. This is called the direct backlight, while the one with the LEDs on the edge is called side backlight.
The direct backlight could provide a higher brightness and a better uniformity of brightness near the edges.
To install the LEDs behind the LCD panel however we need much more space than what is inside the structure of the original LCD monitor so we have abandoned the original enclosure of the monitor and build another enclosure with a greater depth.
The direct backlight allows also to make larger screens. A 19" display can be large enough for most works and for reading, but for watching video we may find that a 22" or 24" is better. There are also some professional uses of the display, like CAD and design, that are easier with a larger display.
Finally this solution has more space on the back of the display to install larger DC filters that could improve the reduction of electromagnetic emissions.
Current status
Currently we have proved the possibility of obtaining a direct backlight with simple hand made circuits.
Of course the industries have already designed many kind of LED backlight, both direct and side type, with very good brightness and uniformity, but they haven't considered the electromagnetic emissions at all, so most of the industrial products can't be used with a low DC voltage as we need.
The following photos show a prototype based on a 19" 16:10 LCD panel, and using a direct back light composed of 32 LEDs distributed on a plane behind the panel. This monitor has a separate power supply like our other modified monitors.
|
|
|
|||
|
|
|
The results for the reduction of the electromagnetic emissions are very good, but the brightness of the display is not enough uniform yet.We have to solve some problems about the uniformity of brightness, the optimal number and power of LEDs, the optimal size of the enclosure and several other details. We think that we are going to adjust these in a short time.