Optics module queries

So I’ve completed my assembly,

I’m using the basic optics to start with and was just wondering what the purpose of the whole in one corners of the camera cover was for.

I thought the camera module might need to be completely sealed. If not, then is it a problem that I have this gap?

It seems the self tapping screw heads are a bit of a snug fit and so I can’t clamp it all down.


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The optics module is designed for M2 machine screws rather than self tappers. No2 self-tap are 2.2mm. No 1 are hard to get hold of, and at 1.8mm may be too small to bite in the camera platform.
Two screws should be fine, but all four holes should line up, as in the instructions.
You do want to stop as much stray light as possible. Make sure at least that the sensor is nicely into the recess in the lens extension tube. Light cannot get round corners :slight_smile:.

I played with the 2.2mm self tappers before we put them in the OFI kit, and found they worked better than the M2 screws (which have an annoying tendency to strip the thread). However, we’ve not used them as much, so feedback is very useful!

Do you have a feeling for what it is that’s stopping the top part from sitting neatly on the camera module? It should sit flush even without the screws, so perhaps something has changed on the PCB (or, for example, the foam sticking the sensor down might be thicker than it used to be).

As William says, the four screws should squeeze the camera board between the two plastic parts. You can get away with 2 or 3 of them, but I try to use all four for robustness.

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The parts fit together with no gap without the screws. The head of the screw fouls the extension tube though knocking them off vertical. I can’t tighten them all the way down and the last few turns lift the tube part. I’ll try trimming the bits fouling the screw heads and try again. Can I block the whole in the one corner, I’m more concerned about dust getting in than light?

I’m trimming along the red lines.

The trimming helped but I have also used a full size screwdriver to drive the screws all the way into the pillars on the mount. This has let me screw everything down tightly with just the small screwdriver.

Any idea about the hole into the extension tube?

I agree that those marked areas are in the way of the screws.

My workaround was to insert the screws into the part before setting it in place, which is a bit fiddly, but there was enough room to get an allen wrench in.

They are in the way a little! I looked at this and it is a problem in the way the code creates the part, the bottom of that shape is a convex hull of the top of the mount. It is on my list of things that need fixing, but it is actually more work than it looks. Unfortunately it has not percolated to the top of the list of things I need to do.

If someone wants to think of a solution look at lines 73-77 here:

openscad/lens_spacer.scad · master · OpenFlexure / openflexure-microscope · GitLab.

Part of the issue is that the lens spacer is a general function that is useable for other cameras an lenses, and we would like to maintain that or it will be more work down the line.

I’ve not used OpenSCAD yet so can’t contribute yet. It was an easy fix, to trim the part and pre-drive the support though so perhaps a note in the docs might be handy?

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Good point. Over the next few weeks I should be doing a big run through of the build and the docs to look for things like this. I will make sure this gets done.

I think I have now made a solution to this issue.

lens_spacer_picamera_2_pilens.stl (579.4 KB)

Details in Merge Request !230


This will be a lesson to me.
Always print the optics module in black. Even if it is just to test the shape, my printer clearly knows that it must be black.

The orange one was no brim, and was on a different place on the bed, and printed with another part that also failed, so it may not really have been the colour. I have not done proper test of the same G-code :grinning:

I hoped to minimise print errors by using the recommended colour scheme. This was as close as I could manage but I think my printer appreciated the effort :smile: