Apparatus for determining pen acceleration
First Claim
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1. An apparatus for measuring pen acceleration for use in a signature verification system, comprising:
- a pen having capacitive transducer means mounted therein for changing capacitance responsive to acceleration of said pen,a Blumlein bridge circuit having an input and an output and having one arm thereof comprised of the capacitance of said capacitive transducer means,amplifier means having an input connected to the output of said Blumlein bridge circuit, and having an output for providing an amplified signal, andA.M. detector means for detecting the modulation on said amplified signal, which corresponds to said acceleration.
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Abstract
An apparatus for determining pen acceleration for use in a signature vertification system. Capacitive transducer means are mounted in a pen, and change capacitance by an amount which is proportional to pen acceleration. A Blumlein bridge circuit is utilized to measure changes in the capacitance of the transducer means, and the output of the bridge is amplified and demodulated to result in a signal which is proportional to acceleration.
31 Citations
5 Claims
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1. An apparatus for measuring pen acceleration for use in a signature verification system, comprising:
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a pen having capacitive transducer means mounted therein for changing capacitance responsive to acceleration of said pen, a Blumlein bridge circuit having an input and an output and having one arm thereof comprised of the capacitance of said capacitive transducer means, amplifier means having an input connected to the output of said Blumlein bridge circuit, and having an output for providing an amplified signal, and A.M. detector means for detecting the modulation on said amplified signal, which corresponds to said acceleration. - View Dependent Claims (2, 3)
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- 4. The apparatus of claim 4, wherein said signature verification system defines x and y directions, and wherein said capacitive transducer means includes two of said capacitance-changing elements, one of which is mounted with its charge storing surfaces perpendicular to said x direction and the other of which is mounted with its charge storing surfaces perpendicular to said y direction.
Specification