Can I modify a Logitech C615 webcam for infinity focus?

I had the same issue/idea as you and decided to see if I could alter the camera to focus father away. After taking it apart, the four spokes don't appear to allow adjustment of the focus. They don't turn. As the camera focuses the lens assembly (including this 4 spoke thing) moves closer to the sensor (for far away focus) and farther from the sensor (for close up focus). I verified by watching it work as it focused close up and far away.

I did, however, desolder the focus assembly's leads and removed the assembly. Underneath there was a clear plastic sticky pad which I removed. That moved the lenses very slightly closer to the sensor which changes the focal range to allow it to focus slightly farther away. If you do this, make sure the top part of the focus assembly doesn't separate from the bottom increasing the distance or causing it to be slanted... mine did this and I had to super glue it together after I was done working on it.

It still won't focus very far out, but it's significantly better. If you can figure out a way to shave some more distance (being literal) you should be able to extend the focus farther. I couldn't think of a way to do it without designing a new bracket, and only needed it to focus better at about 6-10 feet. It may be possible to 'lap' the bracket down if you're very careful to keep it flat.

It's still not as focused at 6' compared to 4" so even for my use I would benefit from less distance between the lens assembly and the sensor. The impact to the 'macro' performance of the camera appears minimal... I think this thing was designed to focus too close - even as a webcam...