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US 4,054,385 AGranted
Apparatus for determining the position of a spot of light on a plane surface
AssigneeBell & Howell Company
InventorDesmond Wheable
Life of this patent
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AssigneeBell & Howell Company
InventorDesmond Wheable
Estimating the term…
Apparatus for determining the position on a plane surface where a beam of light strikes the surface in relation to a datum position. In one embodiment the apparatus comprises a liquid crystal device having a common, transparent electrode on one surface and a plurality of spaced, parallel, segmental, transparent electrodes on the other surface to define a corresponding plurality of liquid crystal cells. Means is provided for changing the light-transmission characteristics of the liquid-crystal cells in a predetermined sequence from a datum position. Means is provided for directing a beam of light towards the liquid-crystal device from one side of the device and a detector positioned on the other side of the device is arranged to detect a change in the light-level of the beam transmitted through the liquid-crystal device when the light-transmitting characteristic of a cell receiving the beam is changed to provide a detector output signal and an indicator responsive to the detector output signal provides an indication of the cell receiving the beam, thereby providing an indication of the position on the surface of the liquid-crystal device struck by the beam.
Apparatus for determining the position on a substantially plane surface where a beam of light strikes the surface in relation to a datum position, comprising an electrooptic device having a common electrode on one surface and a plurality of spaced, segmental, electrodes in a predetermined pattern on the other surface to define a corresponding plurality of electrooptic cells of which at least one of the common electrode and the plurality of segmental electrodes is transparent, means for changing the light-transmission characteristics of the electrooptic cells in a predetermined sequence from a datum position, means for directing a beam of light towards the electrooptic device and detector means positioned in relation to the device and the light-directing means for detecting a change in the light-level of the beam transmitted through the electrooptic device when the light-transmitting characteristic of a cell receiving the beam is changed to provide a detector output signal and means responsive to the detector output signal for providing an indication of the cell receiving the beam, thereby to provide an indication of the position on the surface of the electrooptic device struck by the beam.
Dependencies are inferred from the claim text.