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[T] D18 Lens Replacement

A project log for T^2 TyMist [gd0138]

I need some virtual desktop monitors that offer 90PPD at 90Hz.

kelvinakelvinA 11/14/2022 at 16:290 Comments

[16:00]

I've been able to scramble up a replacement set of optics for this rather strong F-9.56 lens.

The replacement (compromised of 3 lenses) is another 2 D40 F-30's and a single D43 with a focal length of -50. Conviniently, the resultant image is about the same size, and the 3 lenses are in contact with each other so they probably could be thought of as 1 single lens assembly.

Using a F40 fresnel instead of F35 isn't an option, as the resulting beam is too large:

[16:45] Wait a second... maybe I don't have a solution, if that's the lens thickness:

I stand corrected. With the available options, I'd need an F40 fresnel lens, along with 2 F-30 lenses and an F-40:

The assembly length would be over 20mm longer. Fine for a test rig but not ideal for a final solution.

The nice thing is that the unique BOM count decreases:

[17:45] Unreal engine. If I swap the collimating lens so that it goes F-30, F-40, F-30, I can get the lenses back-to-back and the output looks to be a perfect 2:1 image!

Actually, it alternates if you think of the absolute value of the focal length: 40, -30, -40, -30, -40 -30, 40.

Shame I'd need a bigger lens though:

Below is what the default 4:3 monitor looks like in the visible area, along with the full 1:1 (dotted lines) and dual QHD (16:18 / 8:9) looks like.

The 4:3 is the only one I truly care about, and it fits so I may be able to use this optical layout. The dual 1440p was just a bonus extra idea, though I'd probably go lower anyway just so that I have some padding between monitors and space for icon pointers to other virtual monitors.

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