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Abstract

A control device suitable for controlling the position of a cursor on a computer display. The device includes at least a pair of optical radiation sources irradiating a spaced away pair of optical radiation detectors. Interposed between the sources and detectors is an elongate member moveable transverse to the paths of radiation between sources and detectors. The member is opaque to the radiation and it obscures radiation detected by the detectors dependant upon its position. Thus the outputs of the detectors vary with the position of the member. By comparing the outputs of the detectors, typically subtracting one form the other, the sign of the result indicates the direction the member has been moved and the magnitude can give an indication of the extent of the movement. In a further form, a second pair of sources and a second pair of detectors are provide in similar manner to the first except that the radiation paths are co-planar but at ninety degrees to each other. Then one set of detectors can indicate X axis movement and the other Y axis movement. In one form the member is axially moveable and by comparing changes in outputs of respective detectors this axial movement can be detected and used to indicate Z axis movement or control button clicks. The device can be manufactured to be suitable for use in industrial environments where some previously known control devices could not be used.

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First Claim