Sub-Pixel Spatial Resolution Interferometry (SSRI)

The Sub-Pixel Spatial Resolution Interferometry (SSRI) system increases the spatial resolution of the interferometric measurements by performing multiple measurements of an optical surface with sub-pixel shifts between a charged coupled device (CCD) detector and the optic under test between measurements. The measurements are then combined to create a single measurement with higher spatial resolution. The measurements are combined using a stitching algorithm. This method relieves the spatial resolution constraint defined by the pixel size and spacing. It is assumed that the optical system has been designed to allow the higher spatial frequency features to pass. The SSRI system enables the ability to obtain interferometric measurements of precision optics which have a spatial resolution higher than that defined by the interferometers fundamental limit. This new technique will enable precision optics to be accurately qualified against the specifications and allow fabricators to deterministically correct the higher spatial frequency errors. The SSRI system can be integrated, with slight modifications, into existing commercially available interferometers and interferometric profilers to increase the obtainable spatial resolution.