Objective lens calibration

So I managed to get the microscope running, within Windows boot camped within Mac OS, and the motors seem to be running.

I think my problem from the last thread I started (Running Openflexure on Mac or Manjaro) was because I had accidently installed a default Raspian image onto the microSD, rather than the Openflexure Raspbian. That was probably why the host name “microscope.local” never popped up - because it was just plain old raspberry pi.

But now, having gone the high-quality RPi camera, with a 40x, 0.65 objective lens, I’m having trouble getting a clear image. I think I may have found the proper measuring distance for this lens (36mm), but I could be mistaken.

I’m able to see blurry shadows when I put slide samples above the lens, but I don’t know how to focus it. I just tried calibrating the camera again, and the screen went bright green, with shadows still visible when I put slides above it.

Anyone have any advice here?

Also, I couldn’t get the LED working, so for the time being I have a small flashlight electrical-taped to the illumination dovetail piece, and that seems to be working.

There is a thread here on modifications for the new Pi High Quality camera. There is not yet a good solution for filling the bigger sensor of the new camera, while keeping the module compact. If you leave the tube lens as it is for the RPi V2 camera, then you will need to be careful with planning the camera mount to put the new image sensor in exactly the same place as the old one. That should give a focused image, but it will not fill the sensor area.

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Thanks, so until a solution comes around, would you say I’m better off getting the V2 camera? And would the V2 only work without the objective lens?

The microscope version using the V2 camera and an objective lens has the ‘high resolution optics module’. You will need a tube lens as well when using a microscope objective, preferably an achromatic doublet version. STLs on the openflexure web site are built for f=50mm, diameter 13mm.

…My mistake, I actually am using the V2 camera. Not sure what made me think it was the HQ camera.

Does that make a solution more manageable? You mention a tube lens, which I believe I already have. A flat lens that fits into the “optics_picamera_2_rms_f50d13” STL file, right below where the microscope objective screws in.


In that case I don’t see where your focus problem is coming from. What is the stated working distance of your objective? It is likely to be around a mm. Are you getting the lens close to the slide, or is it even touching the slide before it focuses?

Should the lens be touching the slide as it begins to focus?

No. If it does then that is an indication of a problem.