Support for HQ Pi camera

[jc2450]

Following on from this Twitter thread https://twitter.com/v_saggiomo/status/1303047892953976837?s=21

Vittorio Saggiomo built the option of using a long tube with no tube lens and… well… https://twitter.com/v_saggiomo/status/1303047892953976837?s=21

So there’s two options here we should work one:
First is the long tube as pictured. This might work in the delta stage with a really tall base. Getting the designs for this merged into the main repo would be great.

Option 2 is to add a tube lens in. We need to figure out what lens and in what configuration for the sensor size of the new camera. I’ll look into this but @r.w.bowman is the resident expert so may have some thoughts.

[jc2450]

Specs for the HQ sensor https://www.raspberrypi.org/documentation/hardware/camera/

[Ryan]

That is hilarious. Maybe mount it underneath one of those cheap Ikea tables

LACK high-gloss white, Side table, 55x55 cm - IKEA

[vsaggiomo]

actually that would help
the tube (without tube lens) works with the HQ camera, but it’s 15cm… not really the way to go.
Also, I’ve designed with a CS tread to be screwed on the HQ camera. Also this is probably not ideal.

[WilliamW]

I like the possibility of cs mount. For lab work that opens up the possibility to use all the other cameras. It takes away the nice signal integration to the RPi and the openflexure server, but that is not always needed.
You clearly have proof of principle in your setup. How well does the z-axis cope with the extra size and weight?

[vsaggiomo]

The C/CS mount works without any problem. The problem is the sensors size of the other cameras you want to use (and this is the problem I’m having now with the HQ raspi camera).
The big part of the weight is always on the objective, the extra plastic doesn’t add that much weight, but honestly, this length is impossible to use
We definitely need a new tube lens to bring the total length below 10cm.

[Ryan]

Thought I’d contribute a little to the discussion regarding what I’ve found while playing with the HQ camera for the past couple of days, and from an epi-illumination standpoint. Below is a picture of my setup with an (improved?) illumination arm - it allows for a field aperture to be implemented.

The main issue I’ve found is that without having a significantly long enough tube lens focal length you run into issues with coma aberration.

This image was taken using a lens with a diameter of 20mm and FL of 60mm. (I was trying to avoid vignetting due to the larger image sensor size (useful tool for calculating this for infinity corrected objectives : https://www.edmundoptics.co.uk/knowledge-center/tech-tools/infinite-conjugate-tube-length/).

After some advice, I reduced the tube lens entrance pupil diameter which does help but then you encounter vignetting due to the effect described above. Though the vignetting isn’t the end of the world as I would prefer a fully focused (but not evenly illuminated) field than a poorly focused one, especially as the latter confuses the autofocus algorithms & makes tiling impossible.

Edit: Following image is with 8mm tube lens entrance diameter - can see the improvement but not perfect.

Also demonstration of decently aligned field aperature using my half kohler illumination arm:

[r.w.bowman]

Nice work - that aperture definitely looks better than my initial attempts with short focal length plastic lenses…

It’s worth pointing out that vignetting in this case means you’re effectively cropping the pupil plane, so even if you don’t have coma aberration any more, you are still losing resolution and not just brightness. I guess this is why tube lenses are often more than two elements - you can of course buy better-corrected tube lenses (or pick an air-spaced doublet or cemented triplet) but that’s significantly pricier, so I’d be tempted just to tile multiple images together at that point, and rely only on the sharp part of the image…