LASER BEAM NOISE DETECTION
Original Publication Date: 1978-Dec-31
Included in the Prior Art Database: 2004-Mar-31
Xerox Disclosure Journal
A circuit for detecting and quantifying random, wide frequency band optical power variations from low power CW lasers, Quantifying the power variations is achieved by causing the CW laser light energy to fall on a light detector 2, amplifying the output of detector 2 by amplifier 4 which produces an output voltage that is proportional to the light energy over a range of DC to 2 megahertz, supplying the amplified signal to a low pass filter 6 which attenuates voltage signals con-taming frequencies above 0,5 Hz to establish a long-termDC voltage level proportional to the average laser beam energy, supplying the DC voltage level to a scaling operational amplifier 8 which has exemplary selectable voltage gains of 1.3, 1.2, 1.1, 1.0, 0.9, 0.8 and 0.7, and comparing via comparator 10 the output of scaling amplifier 8 and the unfiltered voltage produced at the output of amplifier 4.