Integrated wavefront sensor and profilometer

A method of measuring aspheric test surfaces comprising steps of:

• generating one or more measurement wavefronts with a wavefront shaper, each of the one or more measurement wavefronts having a curved shape approximating a curved shape of each of one or more areas of the aspheric test surface within a limited region of the aspheric test surface;
• imaging the one or more measurement wavefronts reflected from the one or more areas of the aspheric test surface onto a detector,
• comparing the one or more imaged measurement wavefronts to a datum for obtaining measurements of surface height variations throughout each of the one or more areas of the aspheric test surface;
• focusing light with a single-point profilometer onto each of a succession of points along of one or more traces on the aspheric test surface within an extended region of the aspheric test surface, the extended region including both a portion that overlaps at least a portion of the limited region and a portion that does not overlap any portion of the limited region;
• monitoring signals from the single-point profilometer for obtaining measurements of surface height variations among the succession of points along the one or more traces on the aspheric test surface;
• and
• combining the surface height measurements of the optical wavefront sensor within the limited region with the surface height measurements of the single-point profilometer within the extended region by minimizing differences between the surface height measurements of the optical wavefront sensor and the single-point profilometer within the overlapping portions the limited and extended regions for producing an integrated array of surface height measurements for a combined region of the aspheric test surface that includes both the overlapping portions of the limited and extended regions and the non-overlapping portion of the extended region.

Apparatus for measuring aspheric test surfaces comprising:

• an optical wavefront sensor for measuring surface height variations throughout one or more areas of an aspheric test surface, the surface height measurements throughout each of the one or more areas having a common area spatial frame of reference defined by a set of wavefront sensor compensators, each having an amplitude and a functional form representing the influence of a known variable on the common area spatial frame of reference;
• a single-point profilometer for measuring surface height variations along one or more traces on the aspheric test surface, the surface height measurements along each of the one or more traces having a common trace spatial frame of reference defined by a set of profilometer compensators, each having an amplitude and a functional form representing the influence of a known variable on the common trace spatial frame of reference;
• at least one of the one or more traces overlapping at least one of the one or more areas on the aspheric test surface defining a set of overlapping surface height measurements;
• and
• a processor that combines the surface height measurements of the optical wavefront sensor with the surface height measurements of the single-point profilometer by identifying amplitudes of the wavefront sensor compensators and the profilometer compensators whereby differences between the overlapping surface height measurements of the optical wavefront sensor and the single-point profilometer are minimized.