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US 4,772,786 AGranted
Photothermal oscillator force sensor
AssigneeGeneral Electric Company
InventorRoger M. Langdon
Life of this patent
Estimating the term…
Abstract
A sensor comprises a beam, e.g. of silicon, which resonates at a frequency dependent on the force imposed on the beam. Light on a line induces resonance of the beam by means of the photothermal effect. The light reflected from the beam is amplitude modulated at the resonance frequency, and returns along the line. It is reflected by a semi-reflecting plane mirror onto a lens which focusses it onto a photodetector. The photodetector produces an output voltage modulated at the oscillation frequency, and is thus representative of the force imposed on beam 1.
Claims16
A sensor including:
- a body having a vibratory resonance frequency which is dependent on the nature of an applied force;
- a light source means for providing a continuous illumination;
- a Fabry-Perot interferometer having means for transmitting the illumination to said body so as to illuminate said body such that some of the transmitted illumination is absorbed by the body, said interferometer having two partially reflective surfaces and light transmissive properties which are dependent on a distance between said two surfaces, one of said two surfaces moving with said body such that said distance varies as said body vibrates, the transmitted illumination absorbed by said body causing said body to oscillate at the resonance frequency;
- and
- means for determining the resonance fequency.
2 more elements
A sensor including:
- a body having a vibratory resonance frequency which is dependent upon the nature of an applied force;
- a light source means for providing a continuous illumination;
- a Fabry-Perot interferometer having means for transmitting the illumination to said body so as to illuminate said body such that some of the transmitted illumination is absorbed by the body, said interferometer having two partially reflective surfaces and light transmissive properties which are dependent on a distance between said two surfaces, one of said two surfaces moving with said body such that said distance varies as the body vibrates, the transmitted illumination causing said body to vibrate at the resonance frequency due to a photothermal effect in which a portion of said body alternately expands and contracts resulting from a variation in the intensity of the transmitted illumination;
- and
- means for determining the resonance fequency.
2 more elements
A sensor including:
- a body having a vibratory resonance frequency which is dependent on the nature of an applied force;
- a light source means for providing a continuous illumination to said body;
- a mask interposed between said light source means and said body to transmit to said body only a fraction of the intensity of the illumination, the fraction being dependent on the position of said body, the transmitted illumination causing said body to vibrate at the resonance frequency due to a photothermal effect in which a portion of said body alternately expands and contracts resulting from corresponding variations in the fraction;
- and
- means for determining the resonance frequency.
2 more elements
Dependencies are inferred from the claim text.