So I got a 12" (305mm) ruler to try and imagine the kind of size this helmet would be like. It feels like I could really use an AR headset to help design this HUD helmet that might become an AR headset in the future as a sort of stretch goal. Suprisingly, the UK going rate of the Magic Leap 1 has plummeted to like 10-13% of it's MSRP.

To be honest, the price anchor of £2000+ MSRP wore off after about 5 minutes, and the single reason is due to the low resolution. If I'd never heard of Magic Leap or this was some AliExpress manufacturer, I'd be like "expectable price". I mean, it also includes the computing power too so that's why it's still in my mind.

Moving on, it does seem that, if I'm to use the 300mm tube visor, it can't extend much past my bottom lip or else my natural neck angles will be compromised. It seems that 150mm or so would be ideal, but that length isn't available. Since I need to cut it anyway, I'm thinking of getting a 305mm length (that costs £107) and cutting it in half.

I'm also considering using a perforated metal instead of acrylic. I'd have to make a jig to bend it into a tube and it would let in less light than acrylic, but due to diffraction it might be possible to see decently well though. The PLDC will be adhered onto the inside of the bent metal so that I could actually use the metal as a face shield in the event of a trip+fall.

I'm looking into circular beamsplitter elements and-- actually it'll be easier to explain if I just modelled it.

[about 20 minutes later...]

Wow... I uh didn't expect that modelling to go perfectly straightforward. I was expecting that the 40mm reflectors I had in my mind would still conflict with the door or the face but I've just fit a 60mm set in there super easily without any inconvinience. And angry-eyebrows aside, it actually looks organinc like a Spiderman mask. 

The idea is simple.

First create the beamsplitter and fresnel lens. The lens here is 40mm so maybe it's possible to find a non-fresnel alternative for higher image quality.

Next rotate the front face 45 degrees and move the assembly forward until the lens misses the forehead:

Mirror for the other side. The idea is that the right display is responsible for the left eye and vice versa. I might try and see if 50mm is posible since the edges of glasses might get in the way.

For 4:3 / 3:4 monitors and a 10mm eye box, I expect that the ray volume from the eye to the reflector combiner looks like this:

Unfortunately, geometry is often dissapointing and the rays conflict after the reflection:

It also misses part of the lenses (highlighted in blue). I'll see what I can do after writing this log.

Lastly, I also wanted to mention that I want to add a 10x optical zoom camera and a thermal camera to TyMist if possible.