SILICON LABS 非接触式手势为电子产品设计带来新的创新




475 KB


Silicon Laboratories, Inc. Rev 0.1 1
Touchless Gesturing Brings New Innovation to Electronic Product Designs
Multi-Axis Infrared Proximity Sensing Ushers in the Next Generation of User Interfaces
Human-machine interaction has evolved significantly over the past decade through
enhancements in user interfaces and smart design. Many of these changes have
focused around touchscreen interfaces with high-precision, low-power capacitive
touchscreens at the forefront particularly in the handset market. Now, through
advancements in human interface (HI) technology and design, infrared proximity sensors
are poised to usher in the next user interface innovations centered on touchless
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. More advanced active proximity sensors offer
exciting features and promise enhancements to consumer electronics and industrial
products. Next-generation infrared sensor offerings, such as Silicon Labs Si114x
touchless sensor IC family, are not only smaller and lower power than previous offerings,
but also have the ability to drive multiple infrared light emitting diodes (LEDs), thereby
enabling advanced gesture inputs in multiple dimensions.
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. For example, although proximity sensors are used to deactivate
handset touchscreens during calls to eliminate errant touches by the cheek, a quick web
search reveals that many end users are unhappy with proximity sensor performance in
their handsets. Accidentally muting calls, initiating conference calls and hanging up on
callers are frequent mishaps caused by erroneous proximity sensor operation.
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 sensors do not have any onboard
smarts to aid in distinguishing system noise from an actual signal, and they have trouble
operating in environments with high ambient infrared content such as full sunlight or
rooms lit by incandescent light bulbs for example. Furthermore, with industrial design
taking an increasingly important role in the appeal of modern electronic systems, these
proximity sensors are ill-suited to operate behind very dark overlays that limit the amount
of visible and infrared light reaching the sensor.
Silicon Laboratories, Inc. Rev 0.1 2
The latest generation of proximity sensors, such as Silicon LabsSi114x family,
addresses the shortcomings associated with poor proximity sensor operation. The
advanced architecture of the Si114x sensors as shown in Figure 1, 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 (25.6 microseconds) of other less advanced sensor offerings. This short LED on-
time enables the sensor to determine and compensate for ambient infrared levels in the
environment and to better distinguish them from the actual proximity measurement.
Faster measurements also have the benefit of reducing overall system power. The
infrared LED is the biggest contributor to a proximity systems 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. The LED no longer must be set at a power-hungry
maximum setting. Highly sensitive photodiodes also enable the sensor to operate behind
very dark glass so that the electronics can remain hidden to the human eye, resulting in
cleaner, sleeker industrial designs.
Figure 1. Si114x Proximity Sensor Enables Multi-Dimensional
Touchless Gesture Interfaces