International Business Machines Corporation

Larry A Blue

Alexander G MacInnis

David E Conner

Jose F Gonzalez-Heres

Bruce T Freedman

A method and apparatus that distinguish a valid touch from an optical aberration caused by unwanted objects and/or scratches in the light plane of an optical touch panel device is disclosed. During a training mode the device learns the relative position of 'aberration dropouts' caused by the unwanted objects. During normal operating mode the relative positions of 'touch and aberration dropouts' are generated and compared with the relative position of aberration dropouts to distinguish between aberration dropout signals and touch dropout signals. The touch dropout signals are subjected to further processing to determine the precise location of a touch while the aberration dropout signals are discarded.

Laser touch panel reflective surface aberration cancelling

A switching regulator causes a supply voltage to be intermittently chopped to provide energy pulses in a lowpass filter circuit. The lowpass filter circuit includes a capacitor which is being charged by the chopped energy pulses and whose output is used to drive a low voltage stepper motor. The duty cycle of the energy pulses is a function of the average value of the stepper motor coil current. By correlating the duty cycle of the energy pulses with the average current in the motor coil a relatively high torque is provided to drive the motor during a startup phase and is automatically adjusted to meet the running requirements of the particular stepper motor.

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Durham, NC, United States of America

Larry A Blue