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On January 1991, the esteemed Swedish professor of optics filed a patent titled "Coherence filter", that blocks coherent light regardless of laser light wavelength using destructive interference and lets through ordinary incoherent light. Sometime in 1999, several University College of London professors published "Detection of coherent light in an incoherent background"which uses both optical and digital signal processing with an interferometer to measure the self-coherence function of the incident radiation to produce an interferogram which is subsequently narrow band filtered to yield a sinc envelope.

I was wondering if it is possible to make a tunable coherence filter with 1.8 nanometer bandwidth for visible light which lets through ordinary incoherent light with less than 5db loss. The reason I chose a bandwidth of 1.8 nanometer is because Edmund Optics manufactures part 87293 which is a spectrophotometer with that wavelength resolution.

In certain applications, sensing , filtering and protection from laser radiation is required for protection of eyes.

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  • $\begingroup$ Does this existing patent distort valuable incoherent light background information which a pilot needs to see clearly? Thank you – $\endgroup$
    – Frank
    Mar 1 '16 at 14:15
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    $\begingroup$ I'm just curious about where the 10-50 Hz bandwidth requirement comes from -- it's completely unrealistic. The best lasers have an emission bandwidth on the order of 3 GHz. $\endgroup$
    – Dave Tweed
    Mar 1 '16 at 16:05
  • $\begingroup$ @Dave Tweed, There are no tolerances available for the emission bandwidth of hand-held laser pointers. For the more powerful laser RGB pointers , as may the case in the future, the emission bandwidth is 1 nanometers or 2.9 X 10 Hertz to the power of 5. Yes, I agree the best lasers have emission bandwidths of 2.9 X 10 to the power of 5 GigaHertz. Thank you $\endgroup$
    – Frank
    Mar 1 '16 at 19:06
  • $\begingroup$ @Dave Tweed, Thank you for catching my bandwidth requirement mistake which I corrected earlier yesterday, I will be in the Boston area next Thursday. If you would like, I can meet with you briefly to ask you to join our team of 3 in this unprecedented profit-seeking project which will allow your grandchildren to go to the college of choice. $\endgroup$
    – Frank
    Mar 4 '16 at 11:53
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Since you mentioned "pilot," I'm going to guess you're looking for a way to block laser pointers from distracting airline pilots. It really should be sufficient to use the same thing used in laboratories, i.e. goggles which physically attenuate at and near the laser wavelength. Despite that patent's claims, I'm skeptical that their grating system will operate over the angular range (field of view) needed.

If you can post the actual requirements you're trying to meet, we might be able to suggest other alternatives.

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  • $\begingroup$ I will post the actual requirements we are trying to meet this evening. May I ask which requirements I should post? Thank you. $\endgroup$
    – Frank
    Mar 1 '16 at 18:48
  • $\begingroup$ There are no tolerances available for the emission bandwidth of hand-held laser pointers. For the more powerful laser RGB pointers , as may the case in the future, the emission bandwidth is 1 nanometers or 2.9 X 10 Hertz to the power of 5. Yes, I agree the best lasers have emission bandwidths of 2.9 X 10 to the power of 5 GigaHertz. Have you read the paper, "Detection of coherent light in an incoherent background", discovery.ucl.ac.uk/2621/1/2621.pdf from the University College, London? Thank you. $\endgroup$
    – Frank
    Mar 1 '16 at 19:15
  • $\begingroup$ The actual requirements are to focus light from a set of airplane cockpit views onto to an 512 pixels by 1024 pixel array of Edmund Optics part 62270, High Speed silicon photodetectors with 5 microsecond response time to measure intensity followed by a 512 pixel by 1024 pixel array of Edmund Optics part 87293 spectrophotometers with 1.8 nanometer bandwidth resolution to measure color values. Pilots insist that the final output they see not contain fully saturated pixels in the areas targeted by laser pointers. $\endgroup$
    – Frank
    Mar 4 '16 at 1:29
  • $\begingroup$ @Frank - Please stop attempting to recruit through this site. If you need assistance with recruiting, please contact StackOverflow through their jobs site $\endgroup$
    – user16
    Mar 4 '16 at 13:34
  • $\begingroup$ Could some other engineers please offer a opinion on this question? All replies will be answered within 48 hours by me. Thank you. $\endgroup$
    – Frank
    Mar 6 '16 at 8:38

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