6 - Applications

Rain and fogging sensing are based on capacity measurements, by which rainfall can be reliably calculated even in the case of a heavily soiled windshield. This principle gives the sensor a leading advantage when compared to the more common optical measuring systems available on the market.

The sensor consists of an arrangement of photo diodes underneath a shadow mask. The distance between two neighboring diode pairs differs slightly from the distance between neighboring apertures in the shadow mask. The two diodes of each diode pair are series-connected in reverse bias and connected to a supply voltage. The diode exposed to higher light incidence "draws" the potential at the mutual joint in its direction. All voltages on all diode pairs considered one after another, the consequence of the offset towards the shadow mask is first a sequence of low voltages and then, from a certain diode pair on, a sequence of high voltages. The point at which the electric potential changes abruptly determines the measure for the angle of light incidence.

Using a DMA (Digital Micromirror Array) and light sensors, the intelligent car reflector can be adapted to the external illumination facilities. E.g. the light beam can be adjusted to avoid blanking the driver sitting in an opposite car, while the bright illumination of the road in front of the reflector remains intact.