Two-glass photographic objective color-corrected at four wavelengths

摘要

A photographic objective comprising six lens elements is well- corrected for both monochromatic and chromatic aberrations, and is color- corrected at four wavelengths in a band extending from the visible to the near infrared regions of the electromagnetic spectrum with only negligible secondary and high-order spectra at wavelength between those for which color correction is achieved. The design form for the objective has been optimized for a focal length of 200 mm at an aperture ratio of f/4 and a field of view of 12° without vignetting.