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Browse Prior Art Database

LASER BEAM NOISE DETECTION

IP.com Disclosure Number: IPCOM000023717D
Original Publication Date: 1978-Dec-31
Included in the Prior Art Database: 2004-Mar-31
Document File: 2 page(s) / 365K

Publishing Venue

Xerox Disclosure Journal

Abstract

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.

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XEROX DISCLOSURE JOURNAL

LASER BEAM NOISE DETECTION Proposed Classification
Thomas Reitze U.S. Cl. 331/94.5S
Lyle Ross mt. Cl, H03f 1/22

  Cw LASER

LIGHT

EXTERNAL DC LEVEL

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.

When a scaling amplifier gain of 1,1 is selected, the corn~
parator will provide a change in its output state when varia~
tions in the laser beam energy are in excess of 110% of the DC
component. The output of the comparator will remain in this
output state until the laser beam energy falls below 110% of
the DC (average) laser beam energy. Selecting the 1.2 or 1.3
gains of the scaling amplifier will cause the comparator to
change its output state...