Hi all!!
After reading LOTS of posts about spatial filtering I decided to buy some achromatics and 100µm pinhole to play with.
The purpose: Filtering RGB alltogether…yes, I know it is not the best way to go, but anyway wanna try.
I disposed the lens and started to positioning pinhole… but because my RGB was delivering to much power (3w), my RGB beam drilled a new hole near the 100µm!! by error, I ended with a good customised pinhole!
So, in order to establish a best-affordable method (not buying 100µm pinhole), I removed it and started with a “new” razor-blade method for RGB (Thanks Mr Planters!!!)
The method:
I extracted razor blades from ordinary gillette-machine. These are really thin blades, so easy to drill by focused laser beam (just 2,5sec @4W). I suppose these are stainless-steel, sorry, but I don’t have tried any other material yet, have to try.
So, when beams are perfectly FF aligned, I put the achromat telescope and focused to infinite.
Low Down RGB power (to avoid drills when adjusting blade). Then disposed the blade on diagonal (could be vertical too), and started to find the blade-edge-on-focus far-field.
Far-field: When the blade edge is near focus and near beam core it appears as a shadow. So the trick, is to adjust to have the blade-edge shadow as focused as possible (sharper blade-edge image)
Then…move the blade until it covers the beam core, and re-adjust holder until it is also focused on the other side.
This is important because, if not perfectly perpendicular (so focused along all focal plane), we obtain interference circles and so on when the blade is drilled by the beam.
The idea is to have the blade-edge focused along the focal plane, that is, the blade-plane is perfectly perpendicular to the lens beam axis.
So gently moving blade along the focal plane to ensure the blade-edge is focused on the left (beam core at right) and to the right (beam core covered by blade).
Then, fix the holder and test the above again, to check if blade is still well on focus.
Move the blade covering the beam-core, glue it with thermal bi component adhesive and let it cure. Put the power to the max!! After 2-3 seconds the beam drills de blade, making a customized pinhole!
no filtering:
FILTEREDthe wing is due the objective cam, the spot is really nice)
Yes, this is a ‘dirty’ system, but the results are astonishing and we get a quasi-round-gaussian pinhole perfectly matched to the our beam core geometry, cause only the core have the power to drill the blade.
However, the cost is -20% power, but I think it worths cause we have a near-perfect gaussian RGB beam, an all three beams inside same geometry.
POWER WIHOUT SPATIAL:
POWER WITH SPATIAL:
Jordi (SORRY MY ENGLISH)