Abstract: A Tilted Filter Imaging Spectrometer (TFIS) is designed to be a very small optical spectrometer having very high sensitivity and spectral resolution. These properties suggest the use of the device as a Fraunhofer Line discriminator (FLD) to detect objects that fluoresce in sunlight. According to at least one embodiment of the present invention, the tilted filter imaging spectrometer incorporates at least one dielectric filter, at least one imaging lens structure; and an imaging detector operatively positioned at a focal length of the imaging lens structure, wherein the dielectric filter is operatively positioned at an angle relative to an optical axis of the imaging lens structure. In at least a second embodiment, the tilted filter imaging spectrometer further incorporates at least one Fabry-Perot Etalon, wherein the Fabry Perot Etalon and the dielectric filter are operatively positioned at angles relative to an optical axis of the imaging lens structure.