Ambient light sensor

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 ambient light sensor of a Google Pixel 4a smartphone under a microscope