An apparatus for filtering an electromagnetic radiation, comprises at least one spectral separating arrangement (4, 16； 4') configured to angularly separate one or more components of the electromagnetic radiation based on a frequency of the electromagnetic radiation. The apparatus further comprises at least one angularly deflecting optical arrangement (24) that includes a pivot point, and configured to receive the one or more components of the electromagnetic radiation to generate at least one signal associated with the one or more components. The apparatus further comprises at least one optical imaging arrangement (20, 22) configured to receive the one or more components of the electromagnetic radiation, and generate an image of one or more dispersive elements in communication with the one or more components. The apparatus further comprises at least one beam selecting arrangement (10) adapted to receive the at least one signal, and selectively generate at least one selected signal. A position of the pivot point is provided in a proximity of a real image of at least one of the dispersive elements.
