White light Sagnac interferometer for snapshot multispectral imaging

Abstract: The theoretical and experimental demonstration of a multispectral Sagnac interferometer (MSI) is presented. The MSI was created by including two multiple-order blazed diffraction gratings in both arms of a standard polarization Sagnac interferometer (PSI). By introducing these high-order diffractive structures, unique spectral passbands can be amplitude modulated onto coincident carrier frequencies. Extraction of the modulated multispectral images, corresponding to each passband, is accomplished within the Fourier domain. This yields a unique multispectral sensor capable of imaging all the passbands in a single snapshot. First, the theoretical operating principles of a polarization Sagnac interferometer are discussed to provide a context for the MSI. This is followed by the theoretical and experimental development of the MSI, which is an extension of a dispersion-compensated polarization Sagnac interferometer (DCPSI). Indoor and outdoor testing and validation of the MSI is performed by observing vegetation, demonstrating the ability of our experimental setup to detect four distinctive spectral passbands.