Proximity Detection
Proximity detection senses the presence of an object within a specified
distance from the sensor. A fast-growing application is in smartphones where it
is used to disable the touchscreen when a call is answered. This prevents inadvertent
screen interaction and conserves battery life.
TAOS Solutions
TAOS is an industry pioneer and leader in digital ambient light sensing technology
and our solutions include those which combine ambient light sensing and proximity
detection functions in a single device.
TAOS’s product portfolio targets a wide range of products, including mobile phones,
computers, consumer electronics and industrial displays and controls.
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Proximity Detection Fundamentals
There are several methods for detecting the proximity of an object, but
they all operate on the same common principal that energy, when emitted from a source,
will reflect off an object. A sensor detects and gathers the reflected energy and
then passes it to a system which makes a proximity decision. The specified range
that determines a proximity event varies depending upon the application. Optical
proximity detectors sense s reflected light energy, of a particular wavelength,
from a light source. Infrared proximity detection is implemented with an infrared
radiation (IR ) emitter, typically a light-emitting diode (LED), and an IR proximity
detector.
IR Proximity Detection
- The IR LED emits light towards object
- If target object is present, IR light will be reflected towards sensor
- Sensor gathers energy and determines if amount received is sufficient to declare
a proximity event
Proximity Detection Solution IR LED
- Light frequency chosen to match sensor sensitivity
- Activation is controlled by proximity detector
Proximity Detector
- Internal photodiode creates current in response to sensing IR light energy
- Collects IR light energy and converts it to a digital format for processing
- Interrupts (notifies) the MCU/microprocessor when specified energy levels have been
detected
MCU/Microprocessor
- Controls the setup and configuration of the proximity detector via standard I2C
bus
- Communicates with proximity detector and executes the appropriate detection algorithm
Infrared Radiation (IR)
IR is electromagnetic radiation in the frequency range above microwaves, but below
visible light, and therefore not visible by humans. A very beneficial property of
IR is that it can be transmitted through darkened glass or translucent materials,
making it a very attractive technology for consumer electronics and display-centric
devices.
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- Product designers are continually challenged with the trade-offs between adoption
of new complex technologies and achieving the best overall user experience.
- The worldwide “Green” initiative has increased awareness and support for environmental
friendly and energy conscious products.
- The rapid growth of portable, battery-powered products, and their use of power-demanding
displays, has created further emphasis on managing display power consumption.
- To address these market dynamics, product designs are incorporating a wide range
of sensors (i.e. rotation, acceleration, ambient light, proximity detection, etc.)
enabling them to automatically adapt to their environment, thereby optimizing the
user experience and energy conservation.
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