Elmos Semiconductor has released a sun angle sensor with a planar set-up (E910.86) for the precise angle measurement of incidence of light.
The new Elmos sensor needs no optics and is assembled in a small package of just 4x4mm2. If this sensor is placed sufficiently close to the dashboard surface, a planar transition between sensor and environment is possible.
Systems for measuring the angle of incident light are required for many applications in vehicles. Certainly the most well-known among them is the control of air-conditioning systems. For this application, sensors are placed e.g. on top of the dashboard behind the windshield to detect the energy and the angle of incident sunlight for an optimized control of air conditioning.
The light reaches the surface of the sensor directly, without optical focusing or other manipulations. The sensor principle is based on measuring the difference of the photocurrents of two adjacent photo diodes. A shadow mask placed on top of the diodes adequately covers these photo diodes or leaves them exposed. As shadow mask, one of the metallisation levels resulting from the IC manufacturing process is used.
Apart from the angle sensor, the IC contains two photo diodes with a programmable linear amplifier. The photo diodes have two different spectral sensitivities (red and blue sensitive). The amplification is programmed via the SPI interface for both spectral sensitivities. The intensity signal is released through an analog output. The photo current is converted through the feedback resistor into a voltage and then converted back into a current by a second resistor. The resistance relation thus determines the degree of amplification.