I'm finding it difficult to find cheap ebay AR coated lenses of the correct focal length for use with beam expansion. What is the effect of using a PCX lens 50% too small for the beam diameter at its focal length? Just a waste of power otherwise ok? What about if the lens is 50% too large for the beam diameter? Any plusses for having the lens twice as large as it needs to be? I did notice astigmatism wings from a NUBM44 laser diode were eliminated when using a lens twice as large as the beam diameter, is this a commonly known spherical PCX lens property with the newer high power multimode laser diodes? Any other plusses for using PCX lenses which are have diameters which are twice as large or more than they need to be for the beam diameter?
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