Editorial Feature

What is an Absorptive Filter?

Absorptive filters are essentially glass filters that are dyed or pigmented gelatin resins. Like any other filter, absorptive filters allow light of certain wavelengths to pass through. These are mostly used to filter unwanted wavelengths. They are commonly utilized to block a certain band of wavelengths, and are also useful for transmitting long wavelengths and blocking shorter ones.

Some of the advantages that absorptive filters show over the other interference filters are low cost, good blocking, and transmission. Due to the materials used to make absorptive filters, they produce fluorescence. This datasheet will elaborate further on the working, construction, and applications of absorptive filters.

Working Principle

Absorptive filters operate on attenuation of light through the absorption of certain wavelengths. The absorption is a function of the filter’s thickness and the amount of dye present in the glass or gelatin matrix.

Construction and Types of Absorptive Filters

Absorptive filters are made out of colored glass or synthetic gels. They are also available as plastic coated glass, acetate, or gelatin bases impregnated with organic, or inorganic, materials. Rare earth transition metals and colloidal dyes are also used in glass. All the additional materials contribute in enhancing the absorption transition of glass.

Applications

Some of the applications of absorptive filters are given below:

  • Infrared and ultraviolet blocking
  • Fluorescence microscopy
  • Stage lighting, projection devices, and photographic enlargers

References

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