Here you say to use a plano-convex, but the first image shows shows a biconvex, then the second shows the plano-convex (with the ray trace): https://github.com/OpenLabTools/OpenLabTools/wiki/Optical-Setup But here in the BOM you show a biconvex, which doesn't have the one planar side! https://github.com/OpenLabTools/Microscope/wiki/Microscope-Optical-Components-and-Instructions---Summer-2013 So what's the difference, and which is the better/proper one to use?