OP check in. The focus tool arrived - its very simple, easy to use and ... works.

Quite effective. Before focus on left, after on right. The only other change was a quick clean-up of the DVD grating with isopropyl alcohol. The improvement is actually better than the reduced size image suggests. Recommended.

Awesome 🎉 did you find that the lego piece also worked? Obviously we have legos in the kits already 😛

But if not, we can run off a large # of the adapters and put one in each. Thanks so much! Would you be willing to post a new note with a few more photos illustrating the lens focusing steps? The comparison is very encouraging!

HI @warren I did not try the Lego hack, as I had no details of what to do and I had the key on order. No pics as I had my hands fully occupied.

I adjusted the lens in situ, just removing the top and a few blocks for access. You have to remove the DVD grating too, of course. Getting the key on the lens surround is a bit fiddly but once the lugs are aligned the adjustment is easy.

I left the cam connected and the camera image up in the RPiCam web page so I could see the effect of changes. I adjusted about a quarter turn at a time, because there's a slight lag getting to the web image.

I held a pen at about 80 mm from the lens (that's the approx distance to the collimation slit) and once it looked in focus, I cleaned the grating and rebuilt. As you can see, quite an improvement.