Appeal No. 98-1287
Application 08/359,706
instruments is to provide an optical filter in the system, rather than flashing an emitter and calculating
differences in images.
There is no suggestion in the references to make the replacement or modification of the light
beam apparatus in a survey instrument. Nor has the examiner provided reasons why the ordinary
artisan would have expected advantages in replacing or modifying a light beam apparatus in a survey
instrument, based on the disclosed scheme in the environment of vehicle wheel alignment. Appellants
argue, “None of the cited references suggest that background noise is a problem in the surveying art.”
(Brief at 9.) We find no evidence in the record that the artisan recognized a need to cancel
“background noise”, such as that disclosed by McClenahan, when aligning a survey instrument with a
target, such as when using the survey instrument disclosed by Wiklund or Wells.2
We might speculate that the signal to noise ratio (i.e., the ratio of light transmitted and reflected
from the target to ambient light) would be increased if Wells’ system were to calculate the difference in
received images between “on” and “off” cycles of transmission. However, on the basis of the applied
references, the examiner has not shown that the artisan would have been motivated to flash the emitter
in a surveying instrument, and calculate image differences between
2 We do not read appellants’ statement on page 11 of the Brief, regarding “the conventional elimination
of background noise,” as an admission that the technique disclosed by McClenahan is conventional with respect
to surveying instrument apparatus.
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