Now that I've found out how to use the lens formula correctly, I've been able to achieve this ray path. The respective optical elements are about the same lengths as the previous path, which is nice. Another thing is that all the lenses are off-the-shelf. The factory has a MOQ of 10pcs for custom fresnels.

I have the choice of using a 50x50mm or 55x55mm fresnel, and I'm leaning onto using the 50mm as the output image is 46mm. Coincidentally enough, if the size of the image is unchanged, my eye needs to be 90mm away from the output fresnel.

The current design has it 110mm away, but that's an easy issue to fix:

For the 46.8mm output image, I'd need it to be 80mm away from the eye. If it's 90mm away, 100ppd would be achieved. From trying different values and seeing different screens, I can say that

• 70ppd looks pixelated and annoying. Must avoid.
• 80ppd is on the edge of looking pixelated. I'd like to avoid because I'm always going to be squinting, thinking "can I see pixels?".
• 90ppd is a nice balance of sharpness and Windows GUI at 100% scaling. 

So it seems that 100ppd would be ultrasharp if I extrapolated it, and that increments of 10ppd make a very noticable difference, so I'd rather not imagine what Nreal Air and its 50ppd looks like.

Anyway, the simulation mostly agrees with what I expect, other than the distance between the last two lenses being 20mm instead of 23mm

This results in a square size of 42.8mm. Not great, not terrible. At least the beam size is an easier 8.7mm instead of sub 3mm.

[23:45] I just cleared up a listing conflict with the first seller. The D32mm lens listing is only for 1pcs. I've found a different seller that has the same D40.5 F-30mm lens at a lower price (which is great because I need 6pcs) and a D42 F-40mm lens.

The lenses and beam path are awfully close, but remember that the beam modelled is for the diagonal of the square image and that the main desktop area requires a smaller usable diameter (in other words, won't be cut off).

Another good thing is that the square output image is 46.5mm, which I think is an ideal size for a 50x50mm fresnel lens.