BMW K 1600 TFT display

Kevin Ash

Yet another innovation on the BMW K 1600 machines is very obvious from the saddle - the TFT display screen. TFT stands for Thin Film Technology, and while it`s a form of liquid crystal display, it differs in an important aspect.

The term liquid crystal itself sounds like something of a contradiction, but that`s because it`s an unusual substance that exists in a state which is half liquid, half solid. The molecules tend to orient themselves as they do in a solid, but they can still move as in liquids, and in the case of liquid crystal displays, the movement is controlled by electric fields.

The display comprises two polarised panels, one of which also has microscopic grooves running across it in the same direction as the polarisation. The liquid crystal is sandwiched between the polarised panels which are oriented at 90 degrees to each other, and the molecules in it gradually twist from one side to the other, guiding light across through the twist.

When an electric field is applied, all the molecules align in one direction and this twist is lost, meaning the polarised light then meets the grooved panels at right angles, and it`s blocked out, resulting in a black pixel. In the case of coloured LCDs, different coloured backgrounds are allowed to pass through each pixel, all so small you can`t see them individually, but together making up a whole full colour image.

The simplest way to activate each pixel is using glass layers called substrates. One is made up of columns across the display, the other of rows, all made from a transparent conductive material (most commonly indium-tin iodide). To reach a particular crystal a charge is sent along one column and one row, and where they cross it`s stronger and activates the pixel. This is called a passive matrix system.

This works well enough for many circumstances, but the response time is quite slow and the rest of the pixels in each row or column are slightly affected by the electric field too, so the definition isn`t especially good.

TFT is an active matrix system, where each pixel is controlled by a tiny transistor and capacitor. The row and column system is still used, but other pixels other than the one aimed at remain fully switched off, and the capacitor holds its charge fully until the next screen refresh. TFT can also control the amount of charge affecting a crystal and therefore the amount of light it passes, meaning brightness can vary as well (known as the grey scale).

The result is much brighter, sharper displays, but they are a lot more expensive. The reason BMW can fit one to the K1600 is because it already uses hundreds of thousands of them for its car division. Ordering unique ones for relatively low level motorcycle production would not be cost effective, but adding a few thousand to a large car order is much cheaper.