Has anyone used any F-Theta lenses ?

[RedCowboy]

These look interesting and from what I understand can be used after beam directing mirrors to reduce divergence.

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=F-Theta+Scan+Lens&_sacat=0

 

[kecked]

Very expensive used for printing text with laser. This is not the lens your looking for. To get one that large would be a lot like over a grand. Much better to fix before scanners. Going this route buy OPSL. Might be cheaper. Steve knows a bit about these. Is he mixedgas over here?

 

[RedCowboy]

Thanks, I am reading more about them and really should have read more 1st, it's more made to work at a specific distance than variable isn't it.

I have some optics like this salvaged from projection TV's, not the RGB CRT type but the DLP sets we don't see anymore.

 

[diachi]

These look interesting and from what I understand can be used after beam directing mirrors to reduce divergence.

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=F-Theta+Scan+Lens&_sacat=0

They are used for keeping the focal point of a scanning beam on a 2D plane. Generally used in laser engravers so that you don't have to adjust the focus on the fly. A normal lens has a constant focal length and as such as the beam scans away from the center the focal point moves away from the engraving surface.

Very expensive used for printing text with laser. This is not the lens your looking for. To get one that large would be a lot like over a grand. Much better to fix before scanners. Going this route buy OPSL. Might be cheaper. Steve knows a bit about these. Is he mixedgas over here?

If he's trying to engrave a flat surface using a set of scanners to direct the beam this is exactly what he wants. For projection you're better off just fixing the beams before the scanners.

Mixedgas goes by LSRFAQ here.

 

[RedCowboy]

Ok, that makes sense.

 

[paul1598419]

You've piqued my curiosity here. What are you trying to scan in a planar field? Are you trying to print or do something else? Kecked is right that depending on the wavelength of your laser the Theta lens could be very expensive.

 

[Benm]

They would be good for focusing on a plane instead of a part-sphere indeed.

I think they were designed to work the other way around actually: to take microscopic scans without having to adjust focus, or to take images where a whole flat slide is in focus.

 

[RedCowboy]

Huh, I wonder if it would work backwards like a meniscus lens with a ring of laser beams shown into it around it's outer perimeter from a ring close to it's diameter ?

If so an F-theta with a long FL could be used that way with another long FL lens, possibly a Plano convex ( sliding ) to control the convergence point.

If so it could aid in limiting spherical aberrations far field.

 

[paul1598419]

Oh, I don't know if you can use them to try to converge a bunch of beams together if that is your thought. I can't think of anyone who has done that before as it was not what these lenses were made for.