ELF/VLF radio is lower frequency/longer wavelength than light. It makes no sense to me that a lens coating can block these frequencies. Nor that it would be useful if it did.
At ELF frequencies the non-ionizing radiation is very penetrating (used for submerged submarine communications) and because of thier long wavelength they are quite non-directional unless you are working with an antenna many times the width of a human eye (orders of magnitude). This sort of radiation, being non-directional in this case, would not be limited to comming from the front; hence through the lens. A long time ago I worked on a transmitter/receiver pair that worked no lower than 300 KHz (that is above [higher frequency, shorter wavelength] the ELF/VLF range - VLF is 3-30 KHz and ELF is 3-30 Hz) and the antenna was a pair of wires (dipole) 150' above terrain, and about 1.5 miles long to get good sensitivity with very high performance receivers. Submarine communications sites had antennas of 14-28 miles long. By far the most prevalent EM exposure is from the 50/60 Hz from electrical power systems. People have been arguing for years whether or not this is harmful. Generally the studies say no. One result that shows up from time to time is attempts to correlate 60 Hz (power in US) to childhood luekemia. Again not an eye issue and certainly not filterable. This stuff is pervasive in any area with a well distributed power grid.
Lenses blocking magnetic or electromagnetic fields of any intensity would be extremely unlikely. There are relatively few things that block magnetic fields and they are generally not particularly transparant. Make them into a coating so thin it is transparent (don't know if it can be done) and they still would not be effective in a lens. Electromagnetic fields can be blocked by shielding properly constructed to isolate the protected area. Generally this involves surrounding the protected item and usually providing a current path for the intercepted radiation.
Cathode ray tubes intrinsically generate some low energy x-rays (way, way above radio frequencies - see footnote). Standards from about the time of very early color televisions require electronic circuits or other techniques (glass has some lead in it) that severly limit even this soft radiation. These soft x-rays could possibly be blocked by a lens coating but you are much more likely to get much more, and very much more energetic, radiation from outer space (cosmic rays, gamma rays, X-rays, etc.). These are non-directional and not stoppable. And they cause damage. Ride in a commercial jet and the dose goes up quite measurably. Same damage from natural and man-made radioactive sources in the environment. Some old orange/red glazed pottery used Uranium for a colorant) and there is the Radon in your basement/house..
Summary - Ah you want an EMI coating. Would you also be interested in a used bridge near Brooklyn, at a very good price.
Other frequencies for comparison (each prefix to Hz is 1000 times higher than the pervious):
VHF television (channel 2-6) FM radio = 54 -120 MHz
Satellite TV > 3 GHz
Visible light = 300 THz/1 micro meter wavelength
Soft X-rays > 300 PHz
Gamma rays = 30-300 EHz
Anti-Radiation coating
Reply With Quote
Originally Posted by coolme
It makes no sense to me that a lens coating can block these frequencies............
Bookmarks