Patent ID: 7034809

Claim:
A coordinate input apparatus for outputting coordinates of a designated position, comprising: a generally rectangular, flat coordinate input area; a set of at least two detectors for detecting at least one of arrival of light and non-arrival of light from an object to be detected present at any position in said coordinate input area; and coordinate calculation means for outputting coordinates indicative of said position based upon outputs from said two detectors; wherein said two detectors of said set are placed at positions where a combined sensitivity in the vicinity of at least one of predetermined points, within said coordinate input area, nearest to the midpoint of a line segment connecting fiducial points of said two detectors is substantially equal to a combined sensitivity in the vicinity of at least one of predetermined points, within said coordinate input area, farthest from said midpoint, said combined sensitivities indicating the effect of placement of the two detectors upon calculated coordinates.