Patent ID: 8493570

Claim:
A three-dimensional shape measuring apparatus, comprising: a light source; a beam splitter to split illumination light from the light source into beams; a target object to be measured, on which one beam emitted from the beam splitter is irradiated, having a height difference between the highest point and the lowest point; a reference mirror, on which another beam emitted from the beam splitter is irradiated; a light detecting element to detect an interference pattern generated by the interference of an object beam reflected by the surface of the target object and a reference beam reflected by the surface of the reference mirror; and a control computer to process an image detected by the light detecting element, wherein a subsidiary reference beam generating unit to change the optical path of the beam from the beam splitter to generate a subsidiary reference beam is provided between the beam splitter and the reference mirror, wherein the subsidiary reference beam generating unit includes: a subsidiary beam splitter provided between the beam splitter and the reference mirror; and a subsidiary reference mirror provided at one side of the subsidiary beam splitter neighboring with the reference mirror, wherein the subsidiary beam splitter includes a plate beam splitter provided with a fiat front surface, onto which the beam from the beam splitter is irradiated, and a rear surface being parallel with the front surface, wherein the subsidiary beam splitter further includes a compensation plate contacting the rear surface of the plate beam splitter to adjust optical paths toward the reference mirror and the subsidiary reference mirror.