photosensor; light-sensitive element
Technical term in computing and electronics for a device that detects light.
The photosensor in a digital camera converts light into electrical signals.
光センサー is a more general term for any light sensor, while 感光素子 often refers specifically to the light-sensitive element in imaging devices.
Compound of 感光 (kankō, 'photosensitivity') and 素子 (soshi, 'element, device').