Patent ID: 8269975

Claim:
A device for calibrating a wavefront measuring system (WMS) comprising a WMS for transmitting and receiving an optical wavefront, a computer generated hologram (CGH) disposed in an axial path of light traveling to or from the WMS, the CGH including grating rings having a predetermined density, an imaging lens disposed in the axial path between the WMS and the CGH, the optical wavefront transmitted from the WMS, through the imaging lens, toward the CGH, the optical wavefront returned from the CGH, through the imaging lens, and received by the WMS, and the imaging lens forms a less aspheric optical wavefront when disposed in the axial path, than an optical wavefront formed when the imaging lens is not disposed in the axial path, an entrance port of the WMS is configured to form a pupil image of a device under test, a center of curvature (CoC) of the device under test is located along the axial path between the pupil image and the device under test, and the CGH is located along the axial path, adjacent the CoC, when the imaging lens is disposed in the axial path between the WMS and the CGH.