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Seeing In The Dark and Other Unique Infrared Applications

Like many topics in the optics field, much of the current technology is merely a seed of a much higher potential whose breadth of applications hasn’t yet been fully realized. Infrared Optics is one of those topics, and its popularity and scientific investment has grown in recent years. Remember, while the IR Band is its own grouping, it is vast in its own right, spanning 0.7-1000 microns (1000 microns=1mm). It follows that different subsets within it suit different applications. Let’s explore. 

IR Band Name Wavelength Range (microns)
Near IR (NIR) 0.7 - 1.4
Short Wave IR (SWIR) 1.4 - 3
Mid Wavelength IR (MWIR) 3 - 8
Long Wavelength IR (LWIR) 8 - 15
Far IR (FIR) 15 - 1000

electromagnetic-spec...

Figure 1: Electromagnetic Spectrum showing expanded IR Band. The visible spectrum, which spans 0.4-0.7 microns, makes up only a small part of the entire spectrum.

The wavelengths of red light in the visible spectrum increase and approach 0.7 microns at which point they enter with Near Infrared (NIR), the first of the 5 common groups in the IR Band. It concerns night vision, not to be confused with thermal imaging. Night vision has been limited by resolution quality and overall graininess. However, it has seen a surge in resolution improvements in recent years due in part to an improvement in the quality of films used to filter Infrared light into visible light. This is a key function of customized Intlvac systems

Short Wave Infrared (SWIR) currently is most concerned with long range telecommunications and derived applications such as autonomous vehicles. Two main approaches arise: Light Detection and Ranging commonly referred to as LIDAR, and Camera, and each have their own strengths and weaknesses which is why they are best utilized in combination. LIDAR operates via infrared pulses to generate snapshots of the environment in question, which allows it to make decisions by comparing successive shots. Camera’s are more traditional, however the weakness is that laws and regulations prevent certain ranges and fields of view, an issue LIDAR doesn't have. The human eye does not protect itself from harsh infrared light as it does with visible light, which is why the collaboration of technologies is preferred, at least currently.  In contrast, Mid Wavelength Infrared (MWIR) is manipulated in the usage of sensing optics and homing technology. One of the struggles within such technologies is their travel inefficiency. The move has been made to begin introducing gimbaled infrared sensors, a key means of helping the payload anticipate where targets will be as opposed to where they are currently.

This branch of Infrared bleeds into Long Wavelength Infrared (LWIR), which is where thermal imaging is most used, though it is applied in MWIR ranges as well. IR Optics is also seeing use as a fever tracker as the Covid-19 pandemic progresses. Officers in China have been wearing glasses with such abilities, which may seem like something out of a dystopian novel, but each step makes a difference and finding new applications like this motivates new niches for further innovation.

The final group is Far Infrared (FIR) whose applications have not been explored much beyond terahertz imaging commonly used for materials analysis. Far IR spans the longest range within the IR spectrum, from 15 microns all the way to 1000 microns at which point it turns into microwaves. These are just some of the most common applications, but novel ones find use as well, such as IR reflectometry used in non-intrusive artwork analysis. In each of them, however, one thing remains constant: a higher quality lens can solve many of the technical obstacles/limitations that arise.

The materials side has seen a shift as well, as even such staples like Germanium are being bypassed for certain applications. Traditionally, Germanium was favored for its high index of refraction, a key metric in the design of optics. The higher the refractive index, the better light is refracted as it passes through the lens, and therefore less material is required. It is also a comparatively heavy material; an undesirable trait especially in handheld applications. It’s weight only adds to manufacturing cost, a compounding drawback of its already high base cost. Chalcogenides have emerged as a hot new alternative to Germanium, such as BD6. It is currently a leading choice that addresses many of the drawbacks Germanium has, along with a variety of other noteworthy features such as: high transmission and ease of fabrication.

Like the breadth of applications within the IR span, the specific materials add another layer of complexity in the creation of effective high-quality optics. It's important to remember the scale of the entire Electromagnetic Spectrum. A great deal of technology takes place within the visible band, yet its range is so small in comparison to others, which hints at the opportunity beyond. If science has taught us anything, it's that many times we are simply limited by our instrumentation. Intlvac's Nanochrome IV PARMS infrared system and Diamond-Like Carbon system are workhorses in this context, granting the user the ability to explore and innovate the furthest reaches of these bands as they see fit. The power to create and push the boundary is in your hands.

To learn more about how Intlvac’s team of scientists can execute on your infrared optics vision, contact sales@intlvac.com

Photo source: Concordia University

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