why use telescopic lenses when you can use another pair of cylindrical lenses?

[Maltes]

This question is to all who use cylindrical lenses to expand the irregular beams from multimode diodes, then use telescopic lenses to shrink the beam down in both axis so it can fit into scanners.

Why not expand the beam as much in the first place, and use another pair of flipped cylindrical lenses for resizing the other axis only? Won't adjusting cylindrical lens pair for one axis be easier than a telescopic lens pair which shapes both axis?

[catalanjo]

I think you might have got the wrong end of the stick from my post on the other thread !

@ "This question is to all who use cylindrical lenses to expand the irregular beams from multimode diodes, then use telescopic lenses to shrink the beam down in both axis so it can fit into scanners."

I don't think anyone does this "so it (beam) can fit into scanners". As I tried to explain this is a "filtering" thing to clean up the beam, and it is not easy to "adjust" the Cyl lens in a vertical axis with precision let alone making the "slit" adjustable and positionable with the required accuracy and stability ....which is why for me this is still "work in progress".

Just to fit scanners, it is best to collimate, then expand over corrected slow axis beam, exactly to required size, since this is cheaper, easier and only done by people who are prepared to accept the greater divergence in return for the extra power without having to get bigger scanner mirrors or perhaps different scanners. In these cases most people use the small scanner mirrors themselves to do any "beam cleaning", since beam usually will be arranged to be slightly bigger than scanner mirrors.

Cheers

[planters]

Assuming that you will use an initial aspherical collimnating lens, as this is the most common approach, then the easiest way to proceed is how I demonstrate in my video on spatial filtering and as described here by catalanjo. Orient the stripes so that they are vertical. Use a cylinder pair to expand the narrow (high divergence) vertical stripes to a more rectangular or even square SHAPE that fits your scanner aperture. Use the next lens pair (PCX/PCV) to produce the correct SIZE that fits your scanner mirrors. If this resizing pair achieves a focus between them then you can choose to add a spatial filter at this point.

Avoid using the scanner edges as a filter. It is non selective and if there is a chamfer at this edge then light striking at that point can actually increase unwanted light spill.

Don't use cylinder lenses where you have to adjust them vertically. This can be done, but it is much harder and no more effective. It will probably work less well because adjustment will be much harder.