Abstract: A stereoscopic objective lens system for video endoscopes and borescopes includes a full diameter collimator lens systems and a pair of half-diameter stereo lens systems. The lens systems can be formed of doublet lenses or a combination of singlet and doublet lenses, or of gradient index lenses, or of a mixture of such lenses. The full-diameter lens system collimates object points, imaging object points to infinity to present equal-angle pairs from symmetrically disposed object points to the small stereo pair. This equal-angle property enables accurate object/image mapping onto the final stereo image pair, such that all parts of each left/right image can be mapped to within a fraction of a video pixel to each other.