Abstract: An objective lens is corrected for spherical aberration at both an operating wavelength and a measurement wavelength, such that the amount of spherical aberration to develop at the operating wavelength is substantially equal to the amount of spherical aberration to develop at a measuring wavelength. The method of lens performance measurement then uses a light source emitting at a wavelength different from the operating wavelength.

Abstract: A method and apparatus for lens measurement that provide for a small error of measurement where a light source used for measurement emits a beam of light at a wavelength different from an operating wavelength of a lens to be measured. The spherical aberration of the lens being measured, which occurs at the nonoperating wavelength, is identified and measured. An auxiliary lens is then placed in the path of the light source emitting the beam of light with the nonoperating wavelength to suppress the spherical aberration. This method allows for performance measurements of the lens to be obtained at the nonoperating wavelength without the adverse effects of the spherical aberration which occurred at the nonoperating wavelength.