Imaging in high-radiation environments with specialised optics
Interview published in
IMAGING & MACHINE VISION EUROPE
With Rob Watkinson, Purchasing and Customer Support, Resolve Optics
In an exclusive interview, Rob Watkinson, a key figure at Resolve Optics, sheds light on the complexities and advancements in optics and imaging systems designed for high-radiation environments.
With a focus on the nuclear and space industries, Watkinson emphasises the importance of using specialised materials to ensure the longevity and reliability of optical systems exposed to radiation. Meanwhile, as the demand for advanced imaging technologies grows, he outlines how radiation-hardened optics are essential for safety and efficiency, as well as the exciting developments in CMOS sensors that promise higher resolutions for future applications.
IMVE: What are the primary challenges of deploying optics and imaging systems for high-radiation environments?
Rob Watkinson: The main challenge for deploying lenses in high-radiation environments are suitable materials for the optical elements. Standard glasses will turn brown when they are exposed to radiation, quickly rendering the optical system unusable.
“Specialist ‘non-browning’ glasses doped with cerium are used to resist the browning effect of radiation”
To avoid this, specialist “non-browning” glasses doped with cerium are used. These glass types can resist the browning effect of radiation for significant lengths of time. Typically, non-browning glasses will maintain good transmission up to a total accumulative dose of 10-8 rad.
IMVE: What other materials and technologies are used to protect imaging equipment from radiation damage? Could you explain the concept of radiation-hardened optics? How do they differ from standard optics?
Rob Watkinson: While the glass elements are the prime concern when building a radiation-resistant lens, other materials should also be considered to ensure they are suitable for use in high radiation environments.
“Very few plastics are radiation hard and should be avoided in a rad hard system”
Some materials become very brittle after being irradiated. For example, very few plastics are radiation hard and should be avoided in a rad hard system. Lubricating greases should also be carefully chosen to ensure that they will not deteriorate. Failure in this instance can cause the moving parts in a lens to seize up.
IMVE: What are some of the key applications of imaging and machine vision in high-radiation environments?
Rob Watkinson: The largest market for radiation tolerant lenses is within the nuclear industry, here they are used for surveillance and the inspection of power plants and waste reprocessing facilities. Another important area where radiation-resistant lenses are required for imaging applications is the space industry.
“Lenses in space are constantly exposed to radiation”
Although the levels of radiation are lower than you would see from a nuclear inspection application, lenses in space are still constantly exposed to radiation. Consequently, to get the longest life and best performance possible from your spaceborne vision system, many companies are looking to use radiation tolerant lenses for their space applications. Other industries with a need for radiation tolerant lenses include medical, electron beam welding and industrial non-destructive testing.
IMVE: How can imaging systems contribute to the safety and/or efficiency of nuclear facilities or space missions?
Rob Watkinson: In space missions, radiation-tolerant lenses are used to provide high-resolution images of the Earth or to enable observation on a space station or satellite such as remote refuelling, docking or damage inspection. In Nuclear power stations, tolerant lenses are used to carry out critical safety inspections around the reactor as well as general surveillance of areas that may be subject to high radiation in the event of a radiation leak. These rad hard cameras provide critical information to responders and avoid the need for humans to enter hot zones.
IMVE: How can the performance of these systems under radiation exposure be tested and validated?
Rob Watkinson: We have decades of experience designing and supplying radiation tolerant lenses to the nuclear and space industries. Our accumulated years of experience working closely with our customers backs up that all our lenses have been qualified to survive accumulated exposure up to 108 rad. As our lenses are just one part of a larger vision system, radiation testing will inevitably also be carried out on the entire system.
IMVE: What trends and emerging technologies do you think will become most prominent in the future for imaging and machine vision in high-radiation environments?
Rob Watkinson: Traditionally vision applications in high radiation areas have used tube cameras. In recent years, technological developments have resulted in a new generation of radiation tolerant CMOS sensors which are now a viable option for many applications in radioactive environments. The use of these sensors in place of tube cameras has given camera manufacturers the ability to offer much higher resolution cameras than would have ever been possible before.