Optical system for measuring a surface profile of an object using a converged, inclined light beam and movable converging lens

An optical system for measuring a surface profile of an object in relation to a reference surface, comprising:

• first light source means for generating a first measuring coherent light beam;
• converging means having an optical axis, for converging said first measuring coherent light beam onto a measuring point on a surface of said object, and for relaying a light beam reflected from said surface of said object;
• said detector means having a detecting surface on which a reference position is defined, for receiving the reflected first light beam which is reflected from said surface of said object and emerged from said converging means such that a beam spot is formed on said detecting surface, and for generating a position signal according to positions of the beam spot on said detecting surface;
• means for directing said first measuring coherent light beam generated from said light beam generating means to said converging means and for directing the reflected light beam emerged from said converging means to said detecting means, said first measuring coherent light beam generated from said light beam generating means being guided so as to diverge from said optical axis of said converging means so that the first light beam emerged from said converging means is incident on said object at a predetermined inclined, non-perpendicular incident angle, said beam spot on said detecting surface being formed in said reference position when said measuring point is positioned in said reference surface and said beam spot on said detecting surface being deviated from said reference position when the measuring point is shifted from said reference surface;
• first moving means for supporting said converging means and for moving it along said optical axis;
• second detector means for detecting a movement of said converging means which is moved by said first moving means, and for generating a first distance signal according to a movement distance of said converging means;
• second moving means for moving said object relative to said converging means in a direction substantially perpendicular to said optical axis;
• energizing means for generating an actuating signal responsive to said position signal supplied from said first detector means and in accordance with a deviation of said beam spot on said detecting surface, and for energizing said first moving means to move said converging means so as to move said beam spot to said reference position on said detecting surface of said detector means;
• and
• signal processing means for processing said position signal and said first distance signal supplied from said first and second detector means, respectively, for computing the surface profile of said object in relation to said reference surface thereof.