- Guide

What Are Optical Bandpass Filters?

We know optical bandpass filters as merely a wavelength range. Sometimes, we even call it pass band. This device was created to pass one or more specific wavelengths while blocking the rest. Optical band pass filters are quite common in everyday life but a lot of people aren’t always aware of them due to the technicality of its nature. This is an instrument that is commonly used for optical applications that we often colorimetry, environmental testing, fluorescence spectrometry, laser line separation, and flame photometry. 

Bandpass Filter In The Broad Sense

Bandpass filters can pertain to an entire family of bandpass filters that people can use to transmit a select group of wavelengths. Hot and cold mirrors, color filters, as well as short and long filters. Bandpass filters in the broad sense are often used in technical and scientific discussions. 

Bandpass Filter In The Narrow Sense

Bandpass filters can also represent a much more specific entity. These are specifically a precision interference whose job is to filter whatever it is that passes through a well-defined band of light. 

Wavelength Classification

Now that we have clearly defined what an optical bandpass filter is, we can now talk about the wavelength classifications. 

One of the things that can broadly classify optical bandpass filters are the electromagnetic radiation (which is what these things were designed to filter). Electromagnetic radiation can be classified as infrared light, ultraviolet, and visible light. The slight differences in each electromagnetic radiation is indicated in the following:

  • Optical bandpass filters that were designed to pass through visible light has a wavelength of ~380 to 750 nm
  • Meanwhile, the ones that were created for infrared filtering operate on wavelengths of ~750 to 2500 nm
  • There are also ones that were designed to operate ultraviolet spectrum filter light works with wavelengths of ~4 to 380 nm

Pass Band Specs

Pass band specs pertain to the quality and range of the interaction of three important filter specifications such as center wavelength, full width at half maximum and peak transmittance. Let’s take a look at what these terms mean:

  • Peak transmittance pertains to the transmitted light’s maximum percentage within the passband. But when you discuss a filter’s pass band, you might hear people talking about the half maximum. When you hear this, know that they are actually referring to the one half of the peak transmittance value. 
  • Full width at half maximum is called filter’s bandwidth most of the time. Full width at half maximum is the range of wavelengths that are able to pass through the filter once the transmission reaches 50% in comparison to the specified minimum peak. 

  • Center wavelength, on the other hand, is the bandwidth’s midpoint.

Optical bandpass filters are available almost anywhere these days but it is still important to know where you can purchase the ones with the best quality. In that case, you might want to check out https://www.evaporatedcoatings.com/optical-band-pass-filters/. Not will you only learn a whole lot more about the subject but you can also contact customer support to be guided on which type of bandpass filter will suit your projects best. 


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Allen Grey is the founder of scrambl3.com. He is also a blogger, editor, content manager and the website coordinator of scramble.com. Allen loves to play football on his free time.
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