Patent ID: 6914680

Claim:
An optical system for measurement of an optical constant, comprising: an incoming side beam switching mirror configured to receive a light from a light source; first and second converged light reflecting means for forming first and second optical paths by projecting light from the incoming side beam switching mirror so as to be converged at an intersection of the first and second optical paths, the incoming side beam switching mirror being further configured to selectively switch a direction of the light received from the light source to the first or the second converged light reflecting means; a sample holder, said sample holder including a sample fitting hole and a through hole that are selectively advanced/retracted to/from the intersection of the first an second optical paths; and first and second received light reflecting means for projecting light to a single exiting side beam switching mirror, the first and second received light reflecting means being disposed on the optical path of the light reflected by or transmitted through a sample set in the sample fitting hole of the sample holder via said first or second optical path, or the through hole, and said exiting side beam switching mirror is configured to switch a direction of the light projected via said received light reflecting means so that the light is projected toward a single detector, wherein the absolute reflectance and the absolute transmittance for the face side incidence and the back side incidence of the sample can be measured therein.