Plate with lens array

Claim 1

A surface position/inclination sensor optical system comprising: a single laser source for emitting a single laser beam, collimating means for collimating said laser beam, a plate with lens array including a substrate and a plurality of lenses, at least two of which have different focal lengths, said plurality of lenses being integrally arranged in said substrate so as to be linearly or two-dimensionally arrayed, the collimated beam from said collimating means being incident at a right angle on said plate and on said plurality of lenses so as to be focused on a surface to be tested, said surface to be tested being movable or inclinable only to a direction of optical axes of said plurality of lenses, a beam splitting means for splitting the beam which is reflected or scattered on said surface to be tested, the reflected beam passing through said plurality of lenses, focusing means for focusing the splitted beam from said splitting means, and photosensing means for sensing a light intensity of the beam focused thereon through said focusing means, wherein said light intensity derived from one of said plurality of lenses is compared with that derived from the other of said plurality of lenses, thereby obtaining an output signal for an information of position or inclination of said surface to be tested.