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Abstract

A force sensor particularly suited for use in an electronic stylus that senses the contact force on its nib for recording pen strokes and handwriting recognition. The sensor has a housing for a load bearing member for receiving an input force to be sensed and associated circuitry for converting the input force into an output signal indicative of the input force. The bearing member is movably mounted within the elongate body (up to 100 microns). The input force acting on the load bearing member is caused by contact on the nib. The load bearing member is biased against the direction of the input force.The force sensor also has a light source and photo-detector for sensing levels of illumination from the light source. Associated circuitry converts a range of illumination levels sensed by the photo-detector into a range of output signals, so that the illumination level sensed by the photo-detector varies with movement of the load bearing member within the elongate body such that the output signal from the circuitry is indicative of the input force. Using an optical sensor avoids the need to use a delicate piezo-resistive sensor that requires careful tolerancing during production.

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First Claim