Patent ID: 6914721

Claim:
An optical system for use in combination with a stereoscopic microscope of a type including a main objective ( 10 ) having an optical axis ( 12 ) and two stereoscopic observation beam paths ( 11 a , 11 b ) each having a respective lens tube associated therewith, said optical system being used for simultaneous zero-degree and oblique illumination of an observed specimen ( 13 ), said optical system comprising: an illumination beam ( 7 ); and a prism combination ( 3 ) arranged between said main objective ( 10 ) and said lens tubes ( 17 ) to receive said illumination beam, said prism combination splitting said illumination beam into a first illumination sub-beam ( 9 ) and a second illumination sub-beam ( 8 ) and deflecting said first and second sub-beams to said main objective, said first illumination sub-beam being deflected along a path spaced relatively far from said optical axis to obtain said oblique illumination and said second illumination sub-beam being deflected along a path relatively close to said optical axis to obtain said zero-degree illumination; wherein a portion of said prism combination ( 3 ) directed toward said two stereoscopic observation beam paths tapers symmetrically toward said optical axis ( 12 ) of said main objective ( 10 ) in order to achieve optimum and vignetting-free observation, and wherein said prism combination ( 3 ) is radially movable relative to said optical axis ( 12 ) of said main objective ( 10 ).