Automatic wipers are ubiquitous in vehicles and today have advanced across most car segments. Rain sensors to control the speed and frequency of the wipers are not only a comfort feature but are also considered to make driving safer. The correct wiper speed ensures good visibility in all weather conditions. Car manufacturers also view the rain sensor’s location behind the rear-view mirror as ideal for a cluster of sensors, such as a camera, sun sensor and ambient light sensor.
The rain light tunnel sensor is an opto-electronic system that generally consists of LEDs, photodiodes, ambient light sensors and a microcontroller. A near infrared (NIR) light emitting diode located just behind the rear-view mirror sends an infrared light pulse onto the back side of the windscreen. If there’s no rain on the glass, the windscreen reflects 100% of this NIR light back into a receiving photodiode, but when rain falls on the glass, light can escape the windscreen into the outside and the photodiode signal is reduced to the extent of the density of raindrops. So, the difference in the amount of reflected light allows the rain intensity to be calculated and the wiper frequency to be activated and adjusted. Beside this, ambient light sensors are another part of the system, which are used to observe the ambient light brightness and switch on the headlight automatically when dusk breaks or when the car enters a tunnel.
ams OSRAM offers a complete portfolio of tailor-made opto-electronic components for rain light tunnel sensors, such as a variety of photodiodes, ambient light photodiodes and ICs as well as IR-LEDs. Different package sizes and configurations enable highest possible flexibility for optical designs of the rain light tunnel sensor system.
ams OSRAM’s offering
ams OSRAM delivers high reliability photodiodes in various packages (DIL, SmartDIL, ChipLED), ambient light sensor photodiodes, phototransistors and photo ICs, IR-LEDs, all of them also in through-hole technology packages.