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Thread: rgb color order and dichro's needed

  1. #1
    Join Date
    Sep 2010
    Location
    Utrecht The Netherlands
    Posts
    717

    Default rgb color order and dichro's needed

    Hello, if i want to add red and blue to my existing setup, currently green, what is the best way to do.

    I have green in place, 250mw 532nm
    I also have a red laser diode for which i don't know the exact wavelength

    Is it possible to start with these two by putting the red first and then add green to it, how can you make a different color by mixing them? what power would i need for red to make it work with the 250mw green, the red is currently 150 mw and doesn't change the color but just adds red to the frames.
    So if i need more red power which wavelength would be preferable, read affordable, and how much power is needed to go with the green?

    when my budget allows it i like to add blue, can i put this after the green?
    what wavelength and power should i think of?

    Michel

  2. #2
    Join Date
    Mar 2007
    Location
    Eindhoven, Netherlands
    Posts
    51

    Default

    Hi Michel,

    For combining colors you need dichroic mirrors. These are special mirrors that pass some colors and reflect other colors. My typical setup to combine red and green is using a 'pass green, reflect red' dichro. The color you will get is yellow, then with another dichro 'pass red/green, reflect blue' I put in the blue. Then you will get white, see the attached photo.

    For the power of your red, the wavelength you're using will be a deciding factor, a 640nm beam is 'brighter' then a 660 nm beam. So for 640 nm you will need less power then 660 nm.

    I usually use these values:

    R:G:B -> 640:532:473 -> 2:1:1
    R:G:B -> 660:532:473 -> 4:1:1

    Search the forum for a program called chroma, this gives a great idea on how 'white' your beam will be with different power setups.

    - Floris

    Click image for larger version. 

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  3. #3
    Join Date
    Sep 2010
    Location
    Utrecht The Netherlands
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    717

    Default

    i only see for red wavelengths like 635 650 655 671 in the shop

  4. #4
    Join Date
    Sep 2010
    Location
    Utrecht The Netherlands
    Posts
    717

    Default

    does a dichroic mirror work both ways the same or do i have to turn it for different behaviour, like side a reflects red and b passes green.

  5. #5
    Join Date
    Feb 2008
    Location
    East Sussex, England
    Posts
    5,205

    Default

    The glass will be coated on one side. If you press something onto the coated side (like your finger) you will see it touches the reflection. If it is the non coated side the object will look like its got a gap between the reflection and the object.

    You need the coated side to be on the reflect side

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