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B Optics of mobile phone camera

  1. May 31, 2016 #1
    Hey guys im a first timer on PF, and im very new to the whole physics area but im starting to find it very intresting :smile:
    Ive got a question about the optics of a normal camera lins of a mobile phone that perhaps someone can give me answares about of even point me in a direction.

    Question: Im trying to figure out if the camera lins of a mobile phone can pick up specific colors/unique reflections in liquids that are transperant/invisible to the naked eye.
    For example 1: if there is a transperant liquid that could be used to make barcode and scanned with a mobile phone. (Not very practical but all i could think of :sorry:)
    Example 2: A transperant liquid with a specific color/unique tranperant reflection that is unseen by the naked eye but will still be seen by a normal mobile phone camera.
    Just like how a camera phone can pick up IR waves but instead pick up unique tranperant colors or pick up reflections from example a invisible barcode.
    Ive tryd using my buddy google about the optic spectrum of a cellphone camera lins but no success :(
    Im most likley mixing up the concepts of optics and spectrum or something so try not to be to harsh :frown:
  2. jcsd
  3. May 31, 2016 #2


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    Staff: Mentor

    Welcome to the PF.

    It sounds like you already know that many phone cameras can pick up IR that our eyes do not see.

    Another thing you can use is the sampling frequency of the camera circuitry. If you point it at some monitors, you will see lines rolling through the image -- that is related to beats between the refresh frequency of the display and the sample rate of the camera. As long as you keep the refresh rate of your "invisible" display above the flicker fusion frequency of the human eye, you can pass information to your phone camera by varying the refresh frequency in some way... :smile:
  4. May 31, 2016 #3


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    Sure, cameras can be made to look in parts of the spectrum not visible to us. CCD arrays are normally sensitive to infra-red. Cameras need to include a filter if they want to block this part out.
    Also, computers can also pick out special patterns that we wouldn't necessarily notice, even if they are in our visual range. The image may contain special "watermarks" that have encoded information. The watermarks can be very difficult or impossible to see with the naked eye.
  5. May 31, 2016 #4


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    The lens itself will either block or transmit a particular part of the spectrum, it's the sensor that does all the seeing. I believe cell phone cameras can pick up light that is a little higher and a little lower than the human eye, but only just barely. The difference is relatively small. At the higher end of the spectrum, visible light tuns into UV radiation, which is mostly absorbed by the lens itself. At the lower end, visible light turns into infrared radiation, which is barely picked up by the sensor itself. You typically need specialized equipment to image anything well outside of the visual range.
  6. May 31, 2016 #5
    Thanks for the answares guys, its clearing up my head a lil bit :D
    So im starting to move away from the idea about a UV marker that a camera can detect after reading comments.
    Only raised more questions tho :D

    Seens i got these awesome answares im gona try to shot a follow up question to get some clearity:
    *Question 2.0: If i were to use a liquid that contains molecules of reflective material of different colors would a camera lins be able to pick the reflection up without using the flash?.

    Kinda like when the flash from a camera flash hits the photosensitive cells in the retina and causes red eyes when the light bounces of the blood vessels.
    (Not 100% about that red eye theory tho :P )

    Edit* Found a video about reflective spray paint
    but i guess that paints needs the flash from a camera to scan it.
    Last edited: May 31, 2016
  7. May 31, 2016 #6


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    BTW it's lens, not lins

    as long as there is enough ambient light, why not ? .... it picks up colours of all other things, doesn't it

  8. Jun 1, 2016 #7
    ''BTW it's lens, not lins'' Sorry its just bad translation from Swedish, which is actually spelled ''lins'' in swedish :D
    Thanks for the answer :)
  9. Jun 1, 2016 #8
    Thanks for the answers guys, really helpful answers that sets my thoughts to ease :)
  10. Jun 1, 2016 #9


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    well there ya go, so it is, I learnt something new :)
  11. Jun 2, 2016 #10
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