Lensless smart sensor (LSS) technology is designed to capture data rich images using a low-cost phase grating. Although the raw ‘snap’ is indecipherable to the naked human eye, the sensor, which is approximately the size of pinhead, is capable of capturing all of the information in the visual world up to a certain resolution.
LSS technology can be used in a wide range of diverse applications and scenarios, including satellites, mini radios, robots, ‘copters as well as the rapidly evolving Internet of Things (IoT). LSS inventor Dr. Patrick R. Gill recently told Rambus Press he also sees the potential for the integration of LSS tech in next-gen thermal sensing equipment.
“All objects actually glow in the visible range when they’re hot enough, although when cooled down, their peak radiated wavelengths are too red for human eyes to see,” Gill explained.
“If you could see these wavelengths, you would be able to see in total darkness. You would also be able to know where other warm-blooded creatures are or recently have been. You might wonder then, why the animal kingdom isn’t full of thermal eyes. Unfortunately, it’s not all that easy to build eyes – or any optics, for that matter – capable of focusing infrared light.”
As Gill notes, a focusing camera designed to operate within the 10-micron band of the EM spectrum requires a specialized lens made of a material that effectively bends thermal radiation (heat) without absorbing it.
“You can find analogous thermal pinhole cameras in nature (the thermal sensors of a pit viper being one example), yet true focusing optics are rare, in part since it’s so difficult to precisely manufacture the right kind of optics. Although thermal cameras and sensors do exist today, mainstream adoption has been limited due to a high price tag and relatively low resolution,” he said.
“Nevertheless, all thermal sensing systems are equipped with some form of optics (or heat collecting device) and a transducer such as a microbolometer or thermopile array that translates heat into an electrical signal. We can expect transducers to decrease in cost, similar to early MEMS technologies, although optics are likely a different story. “
Indeed, while the cost of thermally refractive lenses has dropped dramatically over the past few years, thermal lenses are still priced higher than visible-light lenses. In addition, silicon optics typically need to be thinner than 5 mm, as silicon readily absorbs heat in the 10-micron band.
“Molded chalcogenides and germanium are more transparent to heat, yet they can be more expensive and difficult to work with,” Gill continued.
“Perhaps most importantly, all of these materials are somewhat hobbled by the fact that the number of lens elements are deliberately limited. This is because a significant amount of heat reflects off of each optical surface – especially in wide-angle applications where the antireflective coating can’t be tuned for every incident angle and wavelength in the black body distribution.”
As Gill points out, humans have a 180-degree field of view, making a sensor with a comparable resolution a natural fit for thermal applications.
“Unfortunately, using traditional methods, wide-angle lens system designs require multiple elements, which mean they won’t work well for thermal sensing. Practically, very few affordable focusing thermal systems offer more than about a 50-degree field of view,” he added.
“However, a lensless smart sensor (LSS) manufactured from a single thermal diffraction grating could capture intelligible signals from a larger range of incident angles – perhaps greater than 100 degrees. In fact, a large field of view combined with the higher selling price of thermal imaging systems (compared to their visible-light counterparts) could mean that wide-angle thermal sensing will be one of the first commercially advantageous applications of LSS technology.”
Interested in learning more? Be sure to check out some of our recent blog articles on the subject, including “From lensless sensors to artificial intelligence” here, “Lensless smart sensors eye the final frontier” here and “What do robots and ‘copters have in common?” here.