A method for testing a rotationally variant optical surface relative to a design specification for the optical surface, comprising: providing a sample beam from an interferometer in the form of a collimated beam from electromagnetic radiation; diffracting the sample beam with a phase-only liquid crystal spatial light modulator, wherein the phase-only liquid crystal spatial light modulator is controlled to form a shaped wavefront for a diffraction order +1 designed to null the departure of the optical surface under test, from a sphere or a flat, based on the design specifications of the optical surface; spatially filtering to remove other diffraction orders and imaging the +1 order diffracted beam shaped wavefront onto the optical surface being tested; conditioning the shaped wavefront with the optical surface being tested; producing a fringe pattern based on optical path differences and resulting interference between the shaped wavefront conditioned by the optical surface being tested and a reference beam of electromagnetic radiation provided from the interferometer; and analyzing the shape of the optical surface based on the fringe pattern; wherein a nulling phase function designed for the +1st order at the wavelength of the interferometer and matching an optical path difference based on the design specifications for the surface being tested is phase wrapped and encoded on the phase only liquid crystal spatial light modulator; and wherein a tilt carrier phase function is added to the nulling phase function to form a composite phase function encoded on the phase only liquid crystal spatial light modulator to increase spatial separation of the +1 order diffracted beam from other orders of diffraction. providing a sample beam from an interferometer in the form of a collimated beam from electromagnetic radiation; diffracting the sample beam with a phase-only liquid crystal spatial light modulator, wherein the phase-only liquid crystal spatial light modulator is controlled to form a shaped wavefront for a diffraction order +1 designed to null the departure of the optical surface under test, from a sphere or a flat, based on the design specifications of the optical surface; spatially filtering to remove other diffraction orders and imaging the +1 order diffracted beam shaped wavefront onto the optical surface being tested; conditioning the shaped wavefront with the optical surface being tested; producing a fringe pattern based on optical path differences and resulting interference between the shaped wavefront conditioned by the optical surface being tested and a reference beam of electromagnetic radiation provided from the interferometer; and analyzing the shape of the optical surface based on the fringe pattern; wherein a nulling phase function designed for the +1st order at the wavelength of the interferometer and matching an optical path difference based on the design specifications for the surface being tested is phase wrapped and encoded on the phase only liquid crystal spatial light modulator; and wherein a tilt carrier phase function is added to the nulling phase function to form a composite phase function encoded on the phase only liquid crystal spatial light modulator to increase spatial separation of the +1 order diffracted beam from other orders of diffraction.