Bandpass filters are optical elements, used in any application area requiring the isolation of a narrow spectral bandwidth and a high signal-to-noise ratio. These filters reject all unwanted energy outside that region by either absorption or reflection.

The characteristics of the bandpass are controlled by multilayer dielectric coatings. Blocking is achieved with a combination of color filter glass and metallic films, specially designed in Esco's facility. Highly-trained opticians laminate the bandpass and blocking elements together to form a single unit, and then seal the edges to prevent degradation due to moisture.

Esco provides standard bandpass filters that are designed for use at several common wavelengths. All models provide out of band blocking of better than 10-4. Two sizes are available: 0.5" and 1.0" diameter. Bandpass filters are shipped as ring-mounted unless unmounted filters are requested at the time of the order. Esco seals each filter with an aluminum ring for additional protection against degradation from water absorption, as well as a more accurate edge.