Night vision goggles have a number of applications, from military use to farming; from scouts to hobbyists. While the images produced have improved over the years, what is seen is still far from perfect and a long way from what could be seen under artificial light.
Improvements to the image may be in the cards following some studies carried out at the University of Sydney. Here the use of infrared has led to an increase in the absorption efficiency of light in a layer of semiconductor. Infrared refers to light (or, more accurately, the electromagnetic spectrum) having a wavelength just greater than that of the red end of the visible light spectrum.
The researchers are claiming that they have achieved 99 percent light absorption efficiency, which compared with the average performance of commercial night vision technology which stands at just 8 percent.
The process contrasts to night vision technology based on thermal imaging. Infrared technology uses image enhancement processes to collect all the available light (which requires the combination of a photocathode and a photomultiplier.) This includes light not visible to the human eye. This is amplified so that the wearer of the goggles can visualize images that would ordinarily be hidden in the dark.
The basis of the method is the use of infrared and thin film light absorbers, created through laser etching. Lead researcher Professor Martijn de Sterke explaisn more in a research note: “Conventional absorbers add bulk and cost to the infrared detector as well as the need for continuous power to keep the temperature down. The ultrathin absorbers can reduce these drawbacks.”
The academic explains further that the etching process allows light to be directed sideways so that almost all of it is absorbed. The other key factor is the thinness of the absorbers, taking the material down to the nanoscale. What is effective about the process is that almost any material can be used, which actually leads to costs reducing when compared with current (and less efficient) night vision technology.
A further advantage is that the technology can be operated at a low temperature. Current thermal imaging devices need to cool down, in order to prevent “ghosting” (that is having an object in the thermal device’s view leave a trail of heat when it moves).
The findings are published in the journal Optica. The research is titled “Total absorption of visible light in ultrathin weakly absorbing semiconductor gratings.”
