Longpass filters provide a sharp cut-off below a particular wavelength. Often used for order sorting, they isolate broad regions of the spectrum, simultaneously providing high transmission of desired energy, and deep rejection of unwanted energy. Constructed of hard, durable first-surface dielectric coatings on optical-quality IR-transmitting substrates, these Infrared (IR) Longpass Filters will withstand normal cleaning and handling associated with any high-quality optical component. These filters are particularly useful for FTIR spectroscopy and Thermal Imaging Applications. For custom sizes and coating requirements, please contact our Sales Department.