Patent ID: 6934036

Claim:
A configuration measuring apparatus comprising: a light source for emitting light having a wavelength λ; a first lens for focusing light emitted from said light source onto a portion of a surface of an object to be measured by having this light pass through said first lens at a position shifted from a center of said first lens; a polarization beam splitter for branching light emitted from said light source into first and second branches after this light has passed through said first lens, and for emitting light of the first branch onto the portion of the surface of the object so as to focus this light onto the portion of the surface of the object; a first λ/4 wavelength plate to be arranged between said polarization beam splitter and the surface of the object; a second lens for collimating light of the first branch by having this light pass through said second lens at a position shifted from a center of said second lens after this light has been reflected from the portion of the surface of the object and passed through said first λ/4 wavelength plate and said polarization beam splitter; a first mirror for reflecting light of the first branch that has passed through said second lens; a second λ/4 wavelength plate arranged between said first mirror and said polarization beam splitter; a second mirror for (i) reflecting, at a focal point of said second lens, light of the first branch that has been reflected from said first mirror and has passed through said second λ/4 wavelength plate, said second lens and said polarization beam splitter such that this light, after being so reflected by said second mirror, is passed through said polarization beam splitter, said second lens and said second λ/4 wavelength plate and reflected from said first mirror so as to pass through said second λ/4 wavelength plate, said second lens, said polarization beam splitter and said first λ/4 wavelength plate, and be again focused onto the portion of the surface of the object, and (ii) reflecting light of the second branch to said polarization beam splitter; a light receiving section for (i) receiving light of the first branch, that has been again focused onto the portion of the surface of object, after this light is reflected from the portion of the surface of the object and passed through said first λ/4 wavelength plate and said polarization beam splitter, and (ii) receiving light of the second branch that has been reflected by said second mirror and passed through said polarization beam splitter; and a computing section for measuring a configuration of the surface of the object based on an interference signal generated by light of the first and second branches after being received by said light receiving section.