California Institute of Technology

Howard K Rockstad

William J Kaiser

Thomas W Kenny

Joseph K Reynolds

Thomas R Van Zandt

Erika C Vote

Judith A Podosek

The use of a dual element approach provides high resolution position sensors based on electron tunneling. This approach allows miniaturization while utilizing the position sensitivity of electron tunneling to give high resolution. The dual-element tunneling structure overcomes the narrow bandwidth limitations of a single-element structure. A sensor with an operating range of 5 Hz to 10 kHz, which can have applications as an acoustic sensor, is disclosed. Noise is analyzed for fundamental thermal vibration of the suspended masses and is compared to electronic noise. It is shown that miniature tunnel accelerometers can achieve resolution such that thermal noise in the suspended masses is the dominant cause of the resolution limit. With a proof mass of order 100 mg, noise analysis predicts limiting resolutions approaching 10.sup.-9 g/.sqroot.Hz in a 300 Hz band and 10.sup.-8 g/.sqroot.Hz at 1 kHz.

Dual element electron tunneling accelerometer

An uncooled infrared tunneling sensor in which the only moving part is a diaphragm which is deflected into contact with a micromachined silicon tip electrode prepared by a novel lithographic process. Similarly prepared deflection electrodes employ electrostatic force to control the deflection of a silicon nitride, flat diaphragm membrane. The diaphragm exhibits a high resonant frequency which reduces the sensor's sensitivity to vibration. A high bandwidth feedback circuit controls the tunneling current by adjusting the deflection voltage to maintain a constant deflection of the membrane which would otherwise change deflection depending upon incident infrared radiation. The resulting infrared sensor will meet or exceed the performance of all other broadband, uncooled, infrared sensors and can be miniaturized to pixel dimensions smaller than 100 .mu.m. The technology is readily implemented as a small-format linear array suitable for commercial and spacecraft applications.

Uncooled tunneling infrared sensor

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Thousand Oaks, CA, United States of America

Howard K Rockstad