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Note that this is also somewhat dispersive, which is actually a plus.
Source needs to be on-axis for spherical reflector, otherwise we get off-axis aberrations (coma, in partticular).
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It's also useful to move solar cell further back so its surface reflections don't bounce back from lens backside.
different reflection orders for 3 inch diameter beam are separated by 0.1*L a distance L from the wedge.
What about using a positive meniscus lens, one side for reflective collimator and other side to focus onto photodiode?
For spherical reflector, focal length is R/2.
For lens of index n, 1/f=(n-1)*(1/R1 + 1/R2)~ 0.5(1/R1+1/R2). So for n=1.5, the transmissive and reflective focal lengths are the same, for plano-convex or plano-concave lens. So if source is at the focus, both reflected and transmitted beams are collimated. Huh.
NBK7 index is 1.5168
Fused Silica index is < 1.5 for lambda > 275 nm. So concave-convex FS lens has 1/f=(0.47)(1/r) and f=2.12 R.
Purchases
Lambda optics 2 inch concave mirror blanks, polished both sides.
Your Lambda Research Optics order has been received.pdf
Bought some 6 inch aperture concave optics on eBay.
References
Large optical wedge vendor, example: https://www.precisionoptical.com/precision-optics/optical-flats/unmounted-reference-flat/
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