SpectroFilm has dedicated considerable effort in the development of optical filters that reduce or eliminate the amount of "AUTO-fluorescence" or the fluorescence of the filters themselves. Due to the nature of some fluorescence instruments (primarily the type and intensity of the excitation source), filter elements can be made to fluoresce thereby contaminating the readings obtained or completely obscuring the desired readings.

Each High Discrimination filter is assembled to reduce auto-fluorescence based on information provided by users about the inner workings of the instruments in which they are used.

SpectroFilm has developed High Discrimination filters for a wide variety of applications and our technical staff is available to develop filters for new applications.

Figure 11. Optical filter spectral curves overlaying absorption and emission spectra of a fluorescent dye. Filters are designed to give maximum transmission while providing maximum attenuation at the wavelength of the other filter. Note that the filters are off the maximum absorption and emission spectra to allow maximum attenuation out-of-band.

Durability

Filters and optical coatings can be interpreted as performing in a variety of ways depending upon who is analyzing the filter.The Military Specifications below have become the standard by which all filter users can tell manufacturers how their filters and coatings will perform when tested to a known standard. The key specifications are listed below.

MIL-C-675A – Coating of Optical Elements, discusses durability to salt spray and humidity.

MIL-STD-810C – Military Standard, Environmental Test Methods – standardizes testing methods for determining resistance to environments in military operations. Interference film testing is generally modified to 5 cycles, however SpectroFilm filters will withstand higher testing to 10+ cycles.

MIL-0-13830A – Optical Components for Fire Control Instruments: General Specification Governing the Manufacture, Assembly, and Inspection of – defines surface imperfections (scratch and dig) as well as testing and inspection methods on substrates with a short discussion of imperfections in optical coatings.

MIL-M-13508C – Mirror, Front Surface Aluminized: For Optical Elements - defines typical durability requirements and testing procedures for front surface coating hardness and adherence.

MIL-F-48616 – Filter (Coatings), Infrared Interference, General Specification For defines performance of interference filter coatings for infrared filters.

MIL-1-45208A provides guidance for the development of in-house inspection plans. SpectroFilm is capable of instituting full Military inspection as specified by the customer.

MIL-STD-45662A defines standards for measurement test equipment calibration. These are standards traceable to the National Bureau of Standards and Technology although natural standards are also allowed with sufficient documentary support of the calibration method.

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This Optical Filter Guide is also available as a print quality
downloadable Adobe PDF file (1.8 MB).

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SpectroFilm is the leading supplier of standard and custom OEM laser diode and optical w filters.