We’re looking at making a bunch of OpenFlexure microscopes for our microscopy students to take home with them so they can do lab activities during Covid-19. We found an amazing deal on 13mm diameter x 49mm focal length achromatic lenses and we’d like to incorporate these into the design instead of the 12.7mm dia x 50mm fl lenses specified in the assembly instructions for the optics module for the high resolution microscope version. I mentioned the source of these lenses in the “sourcing non-printed parts” thread.
In this thread, I’d like to open up a discussion about how to modify the optics module to accommodate different lenses. Maybe the 1mm difference in focal length in our example will not degrade image quality significantly enough to warrant a modification, but maybe it will. How can one determine how big of a modification to make in the physical positions of the components in the optics module?
When I put this question in the chat, @j.stirling made this comment: “It would be best to modify the lens optics module slightly but it wouldn’t just be a 1mm move. However there is in the OpenSCAD code a module called “optics_module_rms”. This takes in the lens radius, lens nominal focal distance, and lens front focal distance and uses them to make the correct optics module. Assuming a high quality achromatic lens you will notice very little change in imaging performance, and a very slight change in field of view. As the move is sub-mm you could probably get away with not adjusting the optics module with only limited performance reduction, but here I am less sure.”
Does anyone have more thoughts on this? How about @r.w.bowman ? Can we put together instructions for modifying the optics module in OpenSCAD?