An ambient light sensor is a component in
smartphones,
notebooks, other
mobile devices, automotive displays and
LCD TVs. It is a
photodetector that is used to sense the amount of
ambient light present, and appropriately dim the device's
screen to match it. This avoids having the screen be too bright when the user's
pupils are adapted for vision in a dark room, or too dim when the device is used outdoors in the daytime. Dimming the screen on a mobile device also prolongs the lifetime of the
battery.
The standard international unit for the
illuminance of ambient light is the
lux
The lux (symbol: lx) is the unit of illuminance, or luminous flux per unit area, in the International System of Units (SI). It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the ...
. The typical performance of an ambient light sensor is from less than 50 lux in dim light to over 10,000 lux at noon.
There are three common types of ambient light sensor:
phototransistors,
photodiode
A photodiode is a light-sensitive semiconductor diode. It produces current when it absorbs photons.
The package of a photodiode allows light (or infrared or ultraviolet radiation, or X-rays) to reach the sensitive part of the device. The packag ...
s, and
photonic integrated circuit
A photonic integrated circuit (PIC) or integrated optical circuit is a microchip containing two or more photonic components which form a functioning circuit. This technology detects, generates, transports, and processes light. Photonic integrated c ...
s, which integrate a photodetector and an
amplifier in one device.
By the end of 2004, about 30% of phones sold in
Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located enti ...
had ambient light sensors,
while in 2016, 85% had a built-in ambient light sensor.
References
{{reflist
Photodetectors