RGB Spatial Filter

[laserbiker]

Very interesting idea.. I think that using spherical mirrors instead of a pair of lenses. will eliminate any chromatic aberrations.
With a RGB beam the center of focus for each color would all be at the same plane as the spatial filter.
Each color would have a differing diameter at the pinhole and this effect might allow to optimize, or worsen"?" the beam profile.
I need to do some experiments.

[Stiffler]

Very interesting idea.. I think that using spherical mirrors instead of a pair of lenses. will eliminate any chromatic aberrations.

That was my reasoning behind this, not sure if it will actually work though.

[TechJunkie]

Has a date been set for NELEM yet? I haven't seen any mention in the forum lately.

Not yet. Not many laserists(?) in New England I guess.

[planters]

I think your idea could work, but you will be introducing astigmatism if you use a curved mirror and strike it at an angle (it doesn't matter if the mirror is spherical or aspherical). The degree of astigmatism is proportional to the sin of the angle of incidence. You can visualize this when you think about the foreshortening of the mirror in the plane that it is tipped in while the sagitta (depth of the concavity) remains the same; the mirror becomes more powerful.

You could avoid this by using an achromatic or even better an apochromatic lens pair for the telescope and operating it on axis. Any residual defocus (there would be very little) could be compensated if the individual color's collimator were tweaked. This should allow a common focal point to be achieved and the small differences in the focus diameter will be proportional to the far field beam diameters and so not too bad or worth worrying about.

The major challenge (Swammidog may have confirmed this) is the need to co-align the three beams not only in the far field and at the galvos, but now also at this common focus. Still, this might work.

[whiteg]

I want build spatial filter (rgb light), but I don't know which telescope lens is good choices?
For example wich edmund optics lenses do I need?