Negative CTE, Positive Results: Exploring Athermalization Solutions for Defense Optics

Negative Thermal Expansion for Defense Solutions

By: Amy Zelazny

Antiquated Athermalization in Defense Optics

As an Optical or Mechanical designer or engineer, you understand that the storage and operational temperature extremes imposed upon defense optics and  imaging systems well exceed those required of most commercially available opto-mechanical assemblies. Designing for these demanding environments presents many challenges associated with image quality, mechanical operation, mechanical performance, and maintaining consistent user functionalityThese challenges exist in varying degrees when considering the design of night vision objectives and eyepieces, riflescopes, surveillance and aerial optical systems, and AR/VR optical systems. 


Today, successful designs are optimized for optical and mechanical performance using traditional materials with well-known and accepted thermal properties. You choose Aluminum, because of its light weight and low price-point, and use it for many housings, barrels, spacers, mounting components, etc. Although you want radial expansion with increasing temperature when mounting optical elementsthe longitudinal increase associated with this expansion leads to compromise in other areas of performance, especially as it pertains to changing air spaces between optical elements. In addition to considerations around optical design parameters and performanceyou need to be concerned with optimizing mechanical connection points, weapons mounting features, focusing mechanisms, and focal plane mounts, to name a few. 

The Negative CTE Revolution for Defense Optics

What if tomorrow you had a new design tool in your toolbox? How would your systems benefit if you could optimize optical performance across temperature extremes as part of your design process by controlling or eliminating longitudinal air space changes? What if you could customize the expansion and contraction of your focal plane stand-offs, utilize constant force washers or fasteners to ensure mechanical robustness, and create mounts and focusing mechanisms that were not affected by temperature? 

Enter ALLVAR Alloys! ALLVAR Alloys are the only metals in the world that have a negative coefficient of thermal expansion (Negative CTE)allowing you to:  


  • Create ultra-stable imaging systems by maintaining mechanical alignment and stability over thermal extremes 
  • Shorten barrel lengths and reduce component count due to less complex optical and mechanical athermalization configurations 
  • Offer a passive solution to athermalization through tunable thermal expansion profiles 

Using this alloy’s unique negative CTE property as one of your design variables will allow you to dial-in a specific thermal expansion value or achieve a zero thermal expansion profile by compensating for the natural expansion of other components in your opto-mechanical assemblies. Based on Titanium, ALLVAR Alloys are highly machinable, have a density similar to Titanium, and a CTE value which is opposite and almost equivalent to Aluminum at -30 ppm/ °C. 

Athermalization Enabled

These are just some of the ways that incorporating ALLVAR Alloys can improveyour opto-mechanical design! Don’t compromise your customer’s requirements – use ALLVAR Alloys and step into the future of  athermalization technology!  


If you’re interested in discussing the many ways that negative CTE ALLVAR Alloys can revolutionize the defense industry, ALLVAR will be attending the upcoming SPIE Defense + Commercial Sensing Conference in Orlando, Florida from April 5th-7th, 2022. We invite you to stop by Booth 518, request a meeting with us here , and register for the tradeshow on the AUSA website, if you would like to learn more about ALLVAR Alloys. 


Don’t forget to follow ALLVAR on our LinkedIn page, check out our Youtube page, and subscribe to our newsletter to stay up to date with our latest news and events! As a team of passionate material scientists and engineers, we would love to connect and answer any questions you may have about our revolutionary material.

Contact Us Today to Revolutionize Your Thermal Performance

Have an application in mind? Please let us know if you have any questions.


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