An ambient light sensor is a component in

smartphone A smartphone is a mobile phone with advanced computing capabilities. It typically has a touchscreen interface, allowing users to access a wide range of applications and services, such as web browsing, email, and social media, as well as multi ...

notebooks A notebook is a small book often used for writing. Notebook or The Notebook may also refer to: Computing *Laptop, a type of personal computer **Notebook (laptop), a specific, smaller class of laptop *Google Notebook, a discontinued online appli ...

, other

mobile device A mobile device or handheld device is a computer small enough to hold and operate in hand. Mobile devices are typically battery-powered and possess a flat-panel display and one or more built-in input devices, such as a touchscreen or keypad. ...

s, automotive displays and LCD TVs. It is a

photodetector Photodetectors, also called photosensors, are devices that detect light or other forms of electromagnetic radiation and convert it into an electrical signal. They are essential in a wide range of applications, from digital imaging and optical ...

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

pupil The pupil is a hole located in the center of the iris of the eye that allows light to strike the retina.Cassin, B. and Solomon, S. (1990) ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing Company. It appears black becau ...

s 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. Some ambient light sensors are also capable to detect ambient color. The standard international unit for the

illuminance In photometry (optics), photometry, illuminance is the total luminous flux incident on a surface, per unit area. It is a measure of how much the incident light illuminates the surface, wavelength-weighted by the luminosity function to correlate ...

of ambient light is the lux. 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:

phototransistor A photodiode is a semiconductor diode sensitive to photon radiation, such as visible light, infrared or ultraviolet radiation, X-rays and gamma rays. It produces an electrical current when it absorbs photons. This can be used for detection and me ...

photodiode A photodiode is a semiconductor diode sensitive to photon radiation, such as visible light, infrared or ultraviolet radiation, X-rays and gamma rays. It produces an electrical current when it absorbs photons. This can be used for detection and me ...

s, and

photonic integrated circuit A photonic integrated circuit (PIC) or integrated optical circuit is a microchip containing two or more photonic components that form a functioning circuit. This technology detects, generates, transports, and processes light. Photonic integrated ci ...

s, which integrate a photodetector and an

amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It is a two-port electronic circuit that uses electric power from a power su ...

in one device. By the end of 2004, about 30% of phones sold in

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

had ambient light sensors, while in 2016, 85% had a built-in ambient light sensor.

References

{{reflist Photodetectors