Abstract: An optical measuring instrument for measuring aspheric surfaces includes an optical measuring arm and a multi-axis drive platform. The optical measuring arm provides for illuminating and imaging the aspheric surfaces. The multi-axis drive platform relatively moves the optical measuring arm with respect to the aspheric surfaces through a plurality of subaperture measurement positions. A focus of adjustable focusing optic is maintained at a nominal center of curvature of the aspheric surfaces. A variable optical aberrator adds aberration to an illumination wavefront to match the illumination wavefront to the intended local shape of the aspheric surface. Fitted low-frequency shape information is distinguished from a remainder of the local shape information yielding mid-frequency topographic measurements of the subapertures, which can be assembled to construct a profile measurement of the aspheric surface.

Abstract: An optical measuring instrument for measuring aspheric surfaces includes an optical measuring arm and a multi-axis drive platform. The optical measuring arm provides for illuminating and imaging the aspheric surfaces. The multi-axis drive platform relatively moves the optical measuring arm with respect to the aspheric surfaces through a plurality of subaperture measurement positions. A focus of adjustable focusing optic is maintained at a nominal center of curvature of the aspheric surfaces. A variable optical aberrator adds aberration to an illumination wavefront to match the illumination wavefront to the intended local shape of the aspheric surface. Fitted low-frequency shape information is distinguished from a remainder of the local shape information yielding mid-frequency topographic measurements of the subapertures, which can be assembled to construct a profile measurement of the aspheric surface.

Abstract: An imaging system for obtaining interferometric measurements from a sample spherical surface has a light source for providing an incident light beam, a beamsplitter disposed to direct the incident light beam toward the sample spherical surface and to direct a test light reflected from the sample spherical surface and a reference light reflected from a reference spherical surface toward an interferometric imaging apparatus. There is a lens assembly in the path of the incident light beam, with at least one lens element, wherein one of the at least one lens elements has an aspheric surface and wherein one of the at least one lens elements further provides the reference spherical surface facing the sample spherical surface. A reference plate is temporarily disposed in the path of the incident light beam for measuring the aspheric surface itself and is removable from the path of the incident light beam for obtaining interferometric measurements from the sample spherical surface.

Abstract: An imaging system for obtaining interferometric measurements from a sample spherical surface has a light source for providing an incident light beam, a beamsplitter disposed to direct the incident light beam toward the sample spherical surface and to direct a test light reflected from the sample spherical surface and a reference light reflected from a reference spherical surface toward an interferometric imaging apparatus. There is a lens assembly in the path of the incident light beam, with at least one lens element, wherein one of the at least one lens elements has an aspheric surface and wherein one of the at least one lens elements further provides the reference spherical surface facing the sample spherical surface. A reference plate is temporarily disposed in the path of the incident light beam for measuring the aspheric surface itself and is removable from the path of the incident light beam for obtaining interferometric measurements from the sample spherical surface.

Abstract: A catadioptric imaging system for an interferometer includes a beamsplitter plate for reflecting a beam of light to a concave mirror for transmitting reflected light from the mirror. The beamsplitter reflections and transmissions produce opposite sign spherical aberrations. A refractive optic is located between the beamsplitter plate and a convex test surface for removing residual spherical aberrations and for permitting more variability in the positioning of the beamsplitter plate. Design variables for both the refractive optic and the position of the beamsplitter plate can be used to adjust a numerical aperture of the beam approaching the test surface. The refractive optic can also be used as a Fizeau objective to further reduce errors in the imaging system.

Abstract: A catadioptric imaging system is used to form a converging test beam for measuring large aperture optical elements having convex spherical surfaces. A beamsplitter block divides a collimated beam of coherent monochromatic light from a laser source into a test beam and a reference beam. A focusing system receives the test beam and transforms the beam into a spherically diverging beam emanating from a point source. A beamsplitter plate partially reflects the diverging beam into a further diverging beam that impinges against a concave spherical mirror at a small angle from normal incidence. The mirror reflects the further diverging beam in the form of a converging beam having a numerical aperture at least nearly equal to numerical apertures of the test surfaces. The converging beam is also interrupted by the beamsplitter plate; but on this occasion, the beamsplitter plate partially transmits the converging beam toward a focal point coinciding with a center of curvature of the test surface.