Temporal coherence difference has been shown to be very useful in electro-optical remote sensing when it is required to detect coherent emissions automatically in the presence of intense but largely incoherent light. Most coherence dependent sensors to date have relied on the sought-after signal emitting light which is significantly more temporally coherent than that from the interfering background. Such sensors in effect employ high-pass coherence processing. This paper describes a novel technique for rejecting unwanted signals which are either less or more temporally coherent than the required signal. The theory is given and an experiment described which shows that even in the presence of a turbulent transmission path, signals within the coherence length range 0.13-0.17 mm are readily detectable; emissions outside the range can easily be rejected. It is because the technique can be used to detect a range or band of coherence values that it is named bandpass coherence processing. Furthermore, the coherence band quoted does not represent a limit on the technique. Indeed the principle can be applied to almost any range and to any waveband where suitable components can be identified.