Human-machine interaction has evolved significantly

by:Getian     2020-07-20

Traditionally infrared proximity sensing systems have incorporated legacy photo-detectors and photo-interrupters, which trigger based on motion or interruption respectively. These proximity sensing solutions are used extensively in automatic doors and lavatory dispensing systems, but the applications have been limited due to the sensor size, power and configurability.

Evolution from single- to multi-LED systems

Single-LED driver proximity sensors have been used in touchscreen handsets for many years and represent the highest-volume proximity sensor market, but their use has not been without issues.

Why does a seemingly simple proximity sensing system malfunction so frequently? The answer lies in the sensor design and configurability as well as the mechanical guidelines that accompany them. Many infrared proximity sensors are just that: dumb sensors that output raw data based on the signals received.

The latest generation of proximity sensors, such as Silicon Labs' Si114x family, addresses the shortcomings associated with poor proximity sensor operation. The advanced architecture of the Si114x sensors, for example, features multiple high sensitivity photodiodes coupled with a high-precision analog-to-digital converter (ADC) to enable measurements with the infrared LED on for a fraction of the time of other less advanced sensor offerings.

Faster measurements also have the benefit of reducing overall system power. The infrared LED is the biggest contributor to a proximity system's power budget. Minimizing the time that the LED needs to remain reduces the overall system power consumption. With 15 dynamically adjustable LED drive settings, the LED drive strength can be adjusted based on the ambient infrared conditions, thereby saving power and leading to a more energy-efficient design.

Triple the LEDs, triple the innovation

While single-LED proximity systems are driving today's market, the future is geared toward multi-LED proximity sensor systems enabling unique innovations in user interfaces. Two-LED infrared systems enable slide and select gestures for use in applications such as page turning in e-books, volume selection in home audio equipment, or scrolling in tablet PCs.

Touchless benefits: health, safety and convenience

A valid challenge to touchless interfaces is why they should be implemented at all. Why do away with tactile buttons and touchscreens if they work? Infrared systems are not going to replace existing systems, but instead they are going to augment the user experience. Increased integration and miniaturization are changing the way customers use electronics products.

Coffee shops, restaurants, gyms, bus stops, plane terminals and even lavatories are fair usage environments for this new generation of embedded electronics. In such diverse operating environments, users' hands are sometimes occupied, dirty, sweaty or covered in food -- all conditions not conducive to touchscreen operation.

Being able to control a device without having to look at it has additional benefits. For example, a touchless interface can allow an automobile driver to safely start/end a call or adjust volume with the touchless swipe of a hand without having to navigate through a complicated instrument cluster to find control buttons. Not all devices have or need complex graphical displays with touchscreens either, and for such devices a touchless interface can provide an innovative and differentiated approach for operation.

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