Appeal No. 98-1287
Application 08/359,706
The Wiklund reference refers, in column 6, lines 18-20, to U.S. Patent No. 4,712,915 for
details of the "rotational modulation" system. We are attaching a copy of the '915 patent (Kosakowski
et al.) to this decision. As shown in Fig. 2 of the '915 patent, light from laser transmitter 1 is modulated
in two ways: by a high frequency modulator 15; and by a low frequency "rotational modulation,"
created by means of motor 9 rotating aperture system 8. Details of the aperture system are shown in
Fig. 3. The central portion of the beam from the laser (11) remains unblocked, while the periphery of
the beam is swept at the low frequency, resulting in a light distribution as shown in Figs. 1a and 1b of
the patent. As shown in Fig. 2 of the '915 patent, the beam is transmitted to target prism 2, and returns
coaxially to receiver 3. Distance detector 14 uses the high frequency portion of the returned signal (a )
1
to determine distance from difference in phase. The low frequency portion of the signal (a ) is
2
processed by circuitry for adjusting alignment of the instrument, by means of a servomechanism
including servomotors 24 and 27.
The '915 patent does not provide details of receiver 3. However, the survey instrument is not
aligned by sensing and centering the image of target 2 on receiver 3, but by detection of a low
frequency modulated signal. It is not apparent that flashing transmitter 1 for calculating differences in
image signals would be an improvement of, or even compatible with, the disclosed servomechanism. If
the disclosed alignment system of Wiklund is to be modified based on the teachings of McClenahan, the
examiner has not explained what the artisan would have been motivated to do.
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