Optical Filters for Raspberry Pi/Nvidia Jetson/Microcontroller Based Embedded Vision Systems & Mono/Multi/Hyper-Spectral Imaging Applications

Published by Lee Jackson on

What Optical Filters Are, How They Work, and Why You Need Them

An optical filter controls how a camera module captures light at the spectral level.

If you try to tear a camera module down to see what it’s made with, you will likely find that, together with an image sensor, a lens, and a PCB board, there’s also an optical filter in it. Camera modules in many consumer products, like camcorders, action cameras, webcams, and cellphones, usually have an infrared-blocking filter in front of the image sensor to deal with sensitivity issues, this is one of the most common types of optical filters used in modern-day digital cameras.

However, when it comes to industrial, medical, or other imaging applications (embedded or not), where camera systems are built for inspection purposes,  where only certain bands of the spectrum are required, where light beams need to be segmented before they can reach the image sensor, things become more complex, and that’s why we need optical filters.

The Spectrum: Light in Different Wavelengths and Their Utilization in Imaging Applications

light in the electromagnetic spectrum and their wavelength frequency range

As a form of electromagnetic wave, all types of light, including those invisible to the human eye, also come in different wavelengths and frequencies; many real-world applications rely on visual systems that are designed for capturing particular spectral ranges.

Cameras equipped with the appropriate image sensor and optical filter can utilize a big portion of the electromagnetic spectrum to create imaging solutions for many industries and scientific fields.

Below is a list of typical wavelengths and their respective applications.

Infrared Light: 700 nm ~ 1 mm

5 types of the inrared light and their wavelengths 1

Infrared light has the widest range of all EM waves and comes in 5 spectrums, the Near-Infrared (NIR) covers wavelengths between 750 nm ~ 1400 nm; the short-wavelength infrared (SWIR) sits between 1400 nm ~ 3000 nm; the mid-wavelength infrared (MWIR) has the range from 3000 nm to 8000 nm; the long-wavelength infrared (LWIR) features the range of 8000 nm ~ 15 μm, while the far-infrared (FIR) begins at 15 μm and goes all the way up to 1000 μm.

Infrared is mostly used for thermal imaging systems, night vision-based surveillance, water absorption detection/visualization, and telecommunication systems, etc.

Visible Light: 400 nm ~ 700 nm

wavelengths of the visible light spectrum

Visible light, AKA “ROYGBIV”,  also called natural light, is what human eyes can see, it has a spectral range between 400 nm to 700 nm, and is ideal for digital photography, VIS microscopy, VIS spectroscopy, etc.

Ultraviolet: 10 nm ~ 400 nm

wavelengths of the ultraviolet spectrum

UV light has a wavelength range between 10 nm ~ 400nm, it’s commonly used in fluorescence microscopy, UV spectroscopy, UV photolithography, drug detection and analysis, etc.

X-Ray: 0.01 nm ~ 10 nm

wavelengths of soft and hard X rays

X-Ray has shorter wavelengths than UV, its spectral range is between 0.01 nm ~ 10 nm, it’s vastly used for applications like medical imaging, astronomy, fluoroscopy, radiotherapy, etc.

Arducam Optical Filters for Monochromatic, Multispectral, and Hyperspectral Camera Systems

Whether it’s about application-focused camera system designs, or project-led imaging science studies, optical filters are usually manufactured to block a specified bandwidth of wavelengths while transmitting other wavelengths.

By selectively utilizing or combining different kinds of optical filters with our embedded camera solutions, you can create cost-efficient imaging systems that are capable of leveraging machine vision for many monochromatic, multispectral, or hyperspectral applications.

Here are the types of optical filters we offer.

Different Types of Optical Filters

how longpass optical filters work 1

Longpass (LP) Filters

how shortpass optical filters work

Shortpass (SP) filters

how bandpass optical filters work

Bandpass Filters

how notch optical filters work

Notch Filters

how neutral density ND filters work

Neutral Density (ND) Filters

how Polarization optical Filters work

Polarization Filters

Need an embedded machine vision system with customized optical filters for specific wavelength ranges?  Talk to one of our imaging scientists now.

Global Shutter Cameras for Multispectral Agricultural Imaging and Mapping

Why you should choose global shutter cameras for multispectral applications:

  • In practice, camera sensors with rolling shutters being mounted on drones or UAVs tend to result in distorted or warped images and videos, the “jello effect” is caused by vibration from the drones and other disturbances in outdoor environments. For agricultural imaging, global shutter sensors are generally better.
  • With the right optical filters, a monochrome global shutter sensor can be aligned with or detect any single/multiple spectral band(s).


1 Comment

Ronian Siew · July 1, 2021 at 7:55 pm

Nice article with great graphics!

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