The filters are separated by energetic sputtering, which ensures a hard, durable and environmentally stable coating. The resulting filters have exceptionally high transmission values and a blocking effect from the visible range to MWIR (300 nm to 10 μm). A dichroitic filter is generally used at a 45° angle of incidence to reflect (let through) the excitation light to the probe and transmit (reflect) the emitted signal to the detector.