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Video projector colour wheels query

Discussion in 'Electronic Repair' started by N_Cook, Mar 18, 2013.

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  1. N_Cook

    N_Cook Guest

    Why is the red sector a denser colour than the blue or green sectors, or at
    least on 2 makes I've looked at, or would more objective/scientific analysis
    show the same colour density?
    It seems to mean that if the lamp becomes under-powered or dirty integrator/
    light tunnel etc then the reds become brown or plum , unless projected onto
    a small screen area
  2. "N_Cook" wrote in message
    Why should they be identical to the eye? The eye is less sensitive to red and
    blue than green. And red and blue wavelengths cover a narrower part of the
    spectrum than green, so less visible light gets through.
  3. N_Cook

    N_Cook Guest

    For both makes, completely different sizes etc, the transmissivity , by eye,
    of the blue sector matches the green sector .
    This projector is used for graphical displays and red indistinguishable from
    black at the usual diagonal is a problem. Cleaning the UV filter at the C/W
    and cleaning the surfaces of the integrator tunnel has improved things a bit
    but not enough. Orange or pink would probably be alright for this use
    instead of red but dark brown or dark plum is not.
    I just tried a scrapped dichroic C/W and it is quite easy to scrape lines in
    the coating , say 10 percent , to pass something more like an orange colour.
    Anyone ever done this to get round underpowered lamp problem and red/brown
    issue? Would heat build up from the multiple scratches compared to just the
    3 butt joins of the glass sectors , as made
    Why dichroic for primary colours transmission and reflection of the
    complement. In dichroic lamp reflectiors I can see a point in that it
    reflects the visible light and transmits the heat through the glass to be
    delt with by fans.
    I cannot see that reflecting the complement is a by-product of reflecting IR
    or UV back to the lamp.
  4. N_Cook

    N_Cook Guest

    Instead of destroying NASA tech, I decided to open up the hole in the mask
    between lamp and C/W, to see if getting more light will help, even if off
    principal axis. At least I can put a mask back if there is too much colour
    spill over from adjascent sectors, a more extreme version of adjusting the
    C/W delay . That did not work because if red is brown then brown does not
    become pinker by losing some red and gaining some blue from the sector on
    that side or going orange by losing some red and gaining some green from
    the other adjascent sector
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