Appeal No. 1997-1899
Application No. 08/407,145
As indicated above, present polarizers as commercially available, do
not transmit the infrared components of light in a linear manner as compared
to other frequency components contained in the light beam. Hence, the
blue-green filter serves to attenuate transmitted light components about the
near infra-red spectrum which are for example, emitted by foilage such as
grass, trees and so on. In this manner, the output light from the entire
arrangement depicted is indicative of nighttime conditions. By rotating the
plate 21 with respect to plates 20 and 22, one can thereby achieve a
variation in the light directed to the night vision device and hence, by such
rotation one can simulate various nighttime conditions as starlight, overcast
moonlight, or direct moonlight and one can do so in any particular daylight
condition as from early dusk to noon day sunlight.
(See Burbo at column 3, line 57 to column 4, line 13.) Burbo clearly compensates for the
variations in light for the entire day from dawn to dusk without the need for a variable filter
as the examiner maintains on page 6 of the answer. Burbo states that the blue-green filter
is to compensate for inherent problems induced by the use of the polarizers, therefore, in
our view, there would have been no motivation to vary this filter since this would negate the
needed compensation.
The examiner argues that the “combination of the static blue-green filter in addition
to the polarization plates makes a mechanically alterable (through attenuation by the
polarization plates) frequency filter (through the blue-green filter).”
(See supplemental answer at page 2.) We disagree with the examiner as discussed
above. The examiner relies upon the Burbo at column 3, lines 14-27 which states:
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