Appeal No. 95-2948
Application 07/833,664
superposition of two driving signals, one being in a high frequency range, typically about 50-200
Hz, and the other within a low frequency range, typically about 5-100 Hz. The reflector oscillates
at a medium-high frequency, about 50-200 Hz, in the x-z plane (torsional mode) and at a low
frequency, about 20-30 Hz, in the x-y plane (bending mode). The scanner structure in figures 6a
and 6b of Dvorkis is similar to appellant's scanner in figure 1 except that appellant's drive source
is coupled to the end of the deformable shaft opposite the reflector.
Bard discloses a hand held bar code reader which use one or more piezoelectric bimorph
elements in the scanning function of the bar code reader optical system. A piezoelectric bimorph
element comprises two layers bonded together with a conductive medium with conductive material
also on the outside surfaces. When a voltage is applied the device bends and when the voltage is
reversed the device bends in the opposite direction (column 6, lines 26-40). Bard states that
piezoelectric actuators can operate at high frequencies "but have a technical disadvantage of a very
small magnitude of mechanical displacement" (column 2, lines 53-56). "Larger displacements are
also possible when the frequency of the drive signal equals the mechanical resonance frequency
of the piezoelement" (column 2, line 67 to column 3, line 1). "FIG. 8 depicts a bar code scanning
optical system having a pair of sequentially mounted piezoelectric bimorphs, a first bimorph 46
for y deflection and a second bimorph 48, mounted on the first bimorph 46, for x deflection, which
drives a scanning mirror 50 for combined x and y deflections of the scanned beam" (column 7,
lines 45-50).
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Last modified: November 3, 2007