Human machine interface

Headlight control

Our optical sensors and light sources are used for optical switches, jog dials, optical touch screens and gesture recognition, in order to support the human machine interface (HMI).

As more and more comfort, multimedia and safety functions are installed in vehicles and mobile devices integrated, the interaction with these devices via HMI also presents the threat to distract the driver from the actual driving task.

To eliminate this threat, the HMI must be very easy and intuitive to for the driver to operate, to avoid turning the main focus off the road. Gesture recognition, optical touch screens, proximity switches, or jog dials are such helpful interfaces.

For gesture recognition, several techniques can be used. Simple gestures, such as wiping from one side to the other, can easily be detected with two reflection light barriers, also called proximity sensors. These consist of an LED and sensor, for example a Silicon Photo IC or Phototransistor, which recognizes when a bigger amount of infrared light from the LED is reflected back to the sensor by an approaching hand.

Optical touch screens and proximity switches of the HMI use the same principle. For optical touch screens, the sensors are placed at the edges or along the sides of the screen, in order to detect the position of a fingertip. For proximity switches, our smart sensor P12347-01CT is ideally suited, as it integrates 3 coloured LEDs, a colour sensor and a small IC chip with I2C interface, inside one tiny package. Therefore our smart sensor is a proximity sensor and it can also illuminate an optical switch in the desired colour with the integrated LEDs.

More complex gesture recognition for the HMI is possible using our TOF CMOS sensor, which works with an indirect time of flight (TOF) measurement as a 3D sensor. An infrared laser diode or LED, or an array of these, is used as active illumination and sends out short light pulses. The CMOS sensor determines the time of flight of the reflected, incident light with each of its pixels, creating a 3D picture. This CMOS is a special, high-speed charge transfer device. That is necessary, as the speed of light is with 3*108m/s very fast, so that a distance of 4,5m (the light travels 9m to the object and back) meaning only 30ns time of flight, which must be measured.

Jog dials work with an optical encoder module, which consist of an LED and Photodiode Array, or a CMOS line sensor. A rotating encoder wheel is placed in the light spot. It has a special coding with holes and no holes, so that each photodiode measures “light” or “no light”, which are read as digital “high” and “low” signals. In this way, the sensor can count up and down from position zero to the angle α with a certain resolution, depending on the amount of photodiodes (4 photodiodes → 4 bit coding, 10 photodiodes → 10 bit coding) and the dimensions of photodiodes and wheel.

Customization possible, please contact us for further information
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