I ran across this news today, which could have big implications for the treatment of glass surfaces used in astronomy optics, and may eliminate camera sensor cover glass reflection.
Scientists at the Center for Functional Nanomaterials (CFN) -- a U.S. Department of Energy Office of Science User Facility at Brookhaven National Laboratory -- have demonstrated a method for reducing the surface reflections from glass surfaces to nearly zero by etching tiny nanoscale features into them.
Whenever light encounters an abrupt change in refractive index (how much a ray of light bends as it crosses from one material to another, such as between air and glass), a portion of the light is reflected. The nanoscale features have the effect of making the refractive index change gradually from that of air to that of glass, thereby avoiding reflections. The ultra-transparent nanotextured glass is antireflective over a broad wavelength range (the entire visible and near-infrared spectrum) and across a wide range of viewing angles. Reflections are reduced so much that the glass essentially becomes invisible.
This "invisible glass" could do more than improve the user experience for consumer electronic displays. It could enhance the energy-conversion efficiency of solar cells by minimizing the amount of sunlight lost to refection. It could also be a promising alternative to the damage-prone antireflective coatings conventionally used in lasers that emit powerful pulses of light, such as those applied to the manufacture of medical devices and aerospace components.
"We're excited about the possibilities," said CFN Director Charles Black, corresponding author on the paper published online on October 30 in Applied Physics Letters. "Not only is the performance of these nanostructured materials extremely high, but we're also implementing ideas from nanoscience in a manner that we believe is conducive to large-scale manufacturing."
Related articles postulate the nanotextured glass would repell water and dust. It could in theory replace colour camera sensor microlense overlays.
Interesting - this is what Canon have been doing for some time using a different process.
Its what gave rise to the DragonFly Imaging project allowing astronomers to go many levels of magnitude deeper by reducing the internal optical noise of their system.
Problem was, the process Canon used wasnt scalable in size up to large telescope mirrors and was limited to small lenses and hence the DragonFly array.
This now hopefully means potentially any large mirror can be made antireflective - if so that is going to make things very interesting.
Wavytome - Apparently its self cleaning - the gaps left between the tiny conical structures are all subwavelength in size
I wonder how much of the light energy is absorbed by the coating instead of being reflected? Is the transmission still comparable to or better than normal AR coated glass?
