A digitally controlled light source system. The light source produces an output which is sensed by a photoreceptor within the feedback loop of an operational amplifier. This maintains the output of the light source constant. The feedback loop can also have a digital control system, to enable digital...http://www.google.de/patents/US6720544?utm_source=gb-gplus-sharePatent US6720544 - Feedback stabilized light source with rail control
