STABLIZED LIGHT SOURCE HAVING LUMINANCE FEEDBACK CONTROL

摘要

An optical lighting apparatus having a constant luminance with a drive current controlled by a controller unit. A temperature controlled photodetector indirectly monitors the luminance and informs the controller when a change in luminance has occurred so that the controller can make appropriate adjustments to the drive current. Also disclosed is a method of regulating the drive current to a light source to enable the luminance to remain fixed and independent of fluctuations in ambient temperature. A temperature compensated photodetector senses the amount of light reflected off a diffuser lens and feeds back the output to a controller circuit which regulates the drive current to the light source. The lighting apparatus has application in calibrating imaging systems, such as digital cameras, and for scanning devices.