Subaperture Stitching InterferometerThe subaperture stitching interferometer is a six-axis, computer-controlled workstation that enables affordable, automated, high-precision characterization of large-clear-aperture and high-numerical-aperture parts. Combining advanced software algorithms and process automation in a robust hardware package, the tool captures precise metrology data for parts that are up to 200 mm in diameter as well as for those that are strongly concave or convex. Developed by Rochester, N.Y.-based QED Technologies Inc. for precision optics manufacturing as an affordable alternative to full-aperture metrology, the interferometer uses a mathematical procedure to construct a full-aperture map of a surface from a collection of subaperture maps. The stitching algorithms employ an optimization method to minimize the discrepancies between overlapping regions caused by systematic and random measurement error. The company says that this device, with its integrated calibration capability, is more accurate than a standard full-aperture test and performs deterministic and repeatable measurement. The workstation comprises a Zygo Fizeau interferometer, a six-axis motion system engineered in cooperation with Schneider Optical Machinery, and stitching algorithms and software (patents pending). Applications that can benefit from this system include those that rely on high-numerical-aperture optics, such as wide-field-of-view imaging and illumination systems used in medicine, projection and inspection. Applications for clear aperture optics include large-aperture imaging systems, such as those used in lithography.