| 摘要 |
PROBLEM TO BE SOLVED: To enable contact (proximity) of a detection object with a coordinate input plane to be exactly detected with high accuracy regardless of distance from the detection object to light receiving means.SOLUTION: A sensor unit (4) projects at least two projection light beams, each being roughly parallel to the other relative to a coordinate input plane and being different from the other in the height from the coordinate input plane. The projection light drive unit (12) of a coordinate control unit (5) switches the projection light beams and causes the sensor unit (4) to project the projection light beams. The sensor unit (4) then receives each reflected light beam, which is a projection light beam reflected by a pointing tool after being projected from the sensor unit. The coordinate calculation unit (11) of a calculation control unit (5) determines whether or not the pointing tool is substantially brought into contact with the coordinate input plane, based on a comparison of the ratio between the received light levels of the reflected light beams received by the sensor unit (4), with a predetermined threshold value.SELECTED DRAWING: Figure 3 |
