Appeal No. 96-3969
Application No. 08/271,311
monitor. A laser beam is passed through a monitoring region
and a lens is positioned to collect scattered light.
Appellants state at page 4 of the specification that the lens
is positioned so that the lens focus is centered on the laser
beam permitting light to emerge from the lens as parallel
rays. A filter is positioned at a preferential angle of
incidence to produce maximum transmission of a selected laser
beam wavelength at the preferred angle of incidence as
illustrated in Figures 2 and 3 of the drawings.
Claim 1 is illustrative of the invention and reads as
follows:
1. A method for reducing errors due to stray light in a
particle monitor, said particle monitor detecting light
scattered from a laser beam by particles, said method
comprising:
positioning a lens in said particle monitor to collect
said light scattered from said laser beam, said lens
positioned such that a focus of said lens lies on said laser
beam, so that said light scattered from said laser beam
emerges from said lens as parallel rays;
positioning a filter to filter said parallel rays, said
filter having a preferential angle of incidence, wherein said
filter provides maximum transmission of a selected wavelength
of said laser beam at said angle of incidence; and
positioning a detector to receive said filtered parallel
rays.
2
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Last modified: November 3, 2007