Human-Machine Interaction in Automobiles

In automobiles, there is a need to realize sensing of force, proximity, ambient light dimming, and gesture control with digital optoelectronics components. Optoelectronics sensor devices enable HMI or Human-Machine Interaction. This requires sensing user inputs and lighting conditions, allowing drivers to keep their eyes on the road. It is possible to connect most optical sensors nowadays to the central controller via the I2C interface.

By setting the internal settings of ASICs or Application Specific Integrated Circuits, it is possible to adjust and fine-tune sensitivity, driving currents, measurement speed, and other parameters to the specifications of the application. This allows force measurement on a given surface for detection or inputs, proximity, and gesture control on the central console, and contrast regulation for adjusting the screen backlight.

Force sensing is necessary to detect an input or control function requiring a force or pressure, adequately strong, to trigger a function. Force sensing in automobiles can also detect false forces, such as from an accidental brush over a touch screen or button. Proper sensing of force allows expanding on input possibilities, like coupling it with menu selections. Low-profile, AEC-Q101-qualified proximity sensors with high sensitivity can have programmable driver current, adjustable in 10 mA steps, flowing through the internal infrared emitter.

Such sensors are popular in force sensing applications. Such applications typically require fine-tuning of sensor performance depending on the given mechanical setup. Implementation of this function requires placing the sensor underneath a surface where the application of force is likely. The high sensitivity of the sensor within a region of 3-10 mm allows the detection of small changes in the displacement of the surface.

Center displays in vehicles use AEC-Q101-qualified proximity sensors. This allows for both gesture and proximity control. Rather than use an internal emitter, the proximity sensor has three current drivers, each with a designated pin. These can directly drive external infrared emitters without needing additional circuitry. This results in a highly flexible solution, where it is possible to choose a specific external infrared emitter to use and their placement with reference to the sensor.

For detecting gestures, it is typical to use narrow-angle emitters. This allows properly defining the area wherein it is necessary to detect motion. For wide areas, it is customary to use wide-angle emitters, such that the sensor solution can cover a wide area. This allows the sensor to cover a wide area, and allows detection of user input, regardless of the direction of the user’s hand entering the sensor’s field of view.

Furthermore, it is possible to have individual ADCs on each channel to allow differentiation of the direction of detection. For instance, this allows detecting user inputs from the passenger side, without distracting the driver.

While proximity sensors gather information about happenings in front of the display, ambient light sensors help with the dimming of the display. The main challenge in such applications is the increasing use of dark cover material used in the interiors of vehicles. At times, these cover materials allow the passing of less than 1% of visible light. Therefore, it is necessary to use a sensor with high sensitivity.