Abstract: A trichroic mirror comprising an optical wedge having two multilayer dielectric interference filters, one disposed on a front surface of the wedge and the other disposed on a back surface of the wedge with the back surface being tilted in a given direction and at a given wedge angle with respect to the front surface, and a reflecting element spaced from the back surface and tilted in a direction opposite to the given direction and at an angle equal to the given wedge angle with respect to the front surface. This mirror separates incident radiation into three spectral bands, all of which may be detected by a single detector in time sequence.