Anamorphic prism pair on rgb?

[jors]

Hi All!
PLease, just a question:
What do you think about correcting rgb white at once?
I suppose ideal way is to correct each color before, then “stack” all beams together (3x “2 pair prisms”) for “white light", BUT anyway, should this setup work?? (just one pair prism on “white light”).

I suppose each color requires ideally particular setup as I said, BUT, I should align prism to obtain an "average" correction for the all.

The idea on setup is:

1st stack the beams
2nd add prism pair
3rd readjust dichros to stack the beams together again before reach galvos.

Don’t need perfect-beam white light, just improve beam much as possible.

Many thanks!!

[planters]

My first thought was this can't work and then I thought about it a little longer and think this might work. The beam expansion ratio will be different for each color with blue>green>red. The deviation as you noted will almost certainly require correction, but will you be able to correct this with the dichroics alone? Maybe you can. Be careful, if you introduce substantial deviation with the prisms then with the wavelength shift with temperature variations the beams will deviate further and the far field will suffer. I would try this first with two colors and see if you have enough adjustment range.

Another interesting idea is that the common prisms might allow you to avoid the dichroics altogether. This might be worth exploring.

[kecked]

I wonder if a special glass could be designed with coatings to compensate the wavelength differences deviations enough to make the prism not spread the wavelengths at all. Sort of like an APO lens for a telescope. This would need to be a stack of high or low pass filters such that only one layer affects each wavelength. Could be done for two wavelengths for sure. Each wavelength would see a different density material on entry that changes group velocity to make it match the other wavelength. The idea is to change the entry velocity and or exit velocity to make them match as they pass through the glass. Sounds expensive but possible. Would need very low expansion glass to keep thermal issues down.

The other idea is to use the difference to allow you to combine the beams by entering at slightly different angles. Problem is the beam entry angle would need to very precise.

Third idea is to change the surface of the prism to a slight lens to compensate. I've never seen a compound lens prism so I have no idea what that looks like.

[planters]

The other idea is to use the difference to allow you to combine the beams by entering at slightly different angles. Problem is the beam entry angle would need to very precise.

This is the idea that intrigues me. Because the angle would be wavelength dependent, you could experimentally adjust the angle by translating the knife edge that first intercepts the output from the collimator. Once established, this might allow the elimination of the dichroics and allow the addition of any arbitrary wavelength you desire to the output from the prism. I think a standard anamorphic pair would work as long as it is broad band anti-reflection coated.