do you want 0 mrad???use binoculars...!work for me.

[Benm]

Monoculars, telescopes and beam extenders are basically the same optical setups, binoculars are two of them as a pair.

If you were to use a 10x50 bi/monocular, you'd get 10 times the beam width, and 1/10th the divergence... with a maximum input beam width of 5 mm, exiting as a beam 5 cm diameter.

They work in reverse too - if you were to shine a laser into the larger end, an thin beam with bigger divergence comes out of the ocular end.

 

[Bluefan]

The beam diverges pure by diffraction. The larger the aperture, the lower the divergence. Throwing two lenses together or buying a cheap binocular may increase the divergence because of lens abberations. Beam expanders probably use asperical lenses as the incoming beam is pretty much the same under all circumstances, nicely collimated at a fixed angle.

 

[Deleted member 8382]

The beam diverges pure by diffraction. The larger the aperture, the lower the divergence. Throwing two lenses together or buying a cheap binocular may increase the divergence because of lens abberations. Beam expanders probably use asperical lenses as the incoming beam is pretty much the same under all circumstances, nicely collimated at a fixed angle.

Two months later...