Appeal No. 1998-1814 Page 12
Application No. 08/347,814
lines 1-4, and col. 5, lines 13-16). Demodulator 48 mixes the
detector signal with a signal at the second harmonic of the
laser modulation frequency, which is selected to be “between
500 Hz and ten kilohertz, 6.6 kilohertz being presently
preferred” (col. 2, lines 5-9 and col. 4, line 68 through col.
5, line 1). Mantz (‘273) similarly discloses (figure 1)
parallel demodulation. Amplifier 40 is used as a phase
sensitive detector (col. 6, lines 55-68) for “locking the mid-
frequency of the cyclical laser scan to the absorption
maximum.” Mantz (‘273)further discloses (col. 4, lines 47-51)
that amplifier 40 is tuned to the frequency of laser 20, and
that amplifier 42, is preferably a tuned amplifier that is
tuned to twice the frequency of amplifier 40. Mantz (‘273)
additionally discloses (col. 7, lines 12-15) that if amplifier
42 is a tuned phase-locked amplifier, the advantages of
synchronous detection (i.e., noise and background suppression)
may be realized.
From these teachings, we conclude that Mantz (‘448) and
Mantz (‘273) teach the limitations of claim 121. Claim 155
contains language similar to claim 121. We therefore affirm
the
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