Various uses of visible light interference patterns are provided. Suitable interference patterns are those formed by diffraction from patterns of apertures. Typical uses disclosed herein relate to spatial metrology, such as a translational and/or angular position determination system. Further uses include the analysis of properties of the light itself (such as the determination of the wavelength of the electromagnetic radiation). Still further uses include the analysis of one or more properties (e.g. refractive index) of the matter through which the light passes. Part of the interference pattern is captured at a pixellated detector, such as a CCD chip, and the captured pattern compared with a calculated pattern. Very precise measurements of the spacing between maxima is possible, thus allowing very precise measurements of position of the detector in the interference pattern.

Methods, systems and devices are described that improve optical spectroscopic techniques and particularly those that involve externally dispersed interferometer (EDI) techniques that result in an output spectrum having improved stability characteristics. The output spectrum minimizes the unwanted shifts in wavelength when the spectrograph component of the EDI instrument is under stresses that would otherwise shift or distort the wavelength positions of the spectrum.

Systems and methods for a non-invasive determination of the characteristics of a light source include placing a non-redundant aperture mask in a path of light emanating from the light source, capturing an image of the interference pattern caused by the light passing through the non-redundant aperture mask, generating visibilities of the light distribution from the image, and determining the characteristics of the light source based on the visibilities of the light distribution, including a process of self-calibration in which the phase-solutions provide a sub-nanometer precision wavefront sensor, and through the use of closure amplitudes without requiring the process of self-calibration.