My current project is to make optical inserts from an old pair of glasses.
The Goggles 3 have the best implemented vision correction I’ve seen, but for my old peepers it still isn’t enough.
I started with a load of calculations to determine feasibility.
The DJI frame is made for lenses up to 1.8mm thick.
If the lenses in those glasses were trimmed down to a 25mm diameter, what would be the edge thickness?
They’re currently a staggering 8.3mm, but myopia lenses get thinner towards the middle. The LLM says we’re unlikely to get below 4.5mm.
We’ll cross that bridge when we get to it.
I started off by modelling and printing opaque lens blanks so I don’t have to keep touching the DJI lenses. Despite being little plastic things, they’re optically good and even have proper coatings, so they deserve some respect.
I then extruded the lens blank to make a thick block, which I’ll use in the final shaping stages of the grinding.
I then disappeared down a rabbit hole to determine exactly how I’m going to machine my lenses.
They’re polycarbonate, which has a bad rep for fracturing and melting, but I’ve found the optical grade variety very forgiving. I made my previous lenses with just a handheld multitool with a sanding pad. These lenses are tiny, so I’ll have to step up the precision.
I glued washers to some carriage bolts in the drill press to get them perfectly level.
The next stage will be to add rubber pads to grip the lenses.
The plan is to use the drill press as a vice while I chop away the excess polycarbonate and then spin and gently cool-grind the lens into a round shape with 25mm diameter.
One of the bolts has a skateboard bearing and will be inserted into a block of wood so it can spin with the drill. This all took a couple of days as I only had slow cure epoxy and had to wait for the perfect sized forstner bit to be delivered to drill the bearing mounting.
Meantime, I put on the old glasses and marked the optical centres with an acrylic pen (permanent markers don’t work on coated lenses).
The next tooling stage will be to mount the lens on the lens-shaped block somehow. Opticians use sticky pads that don’t leave a residue on the lens for this.
I’ll have to improvise. I’ll probably use a rubber-padded g-clamp to hold the lens while I grind it with different grades of sanding drum into its final shape.
Bevelling the lens will be tricky but I think I can just 3d print a jig for it. Will think more about that once the lens shaping has progressed.
In the meantime I’ve been working on the final stage - the framing.
I scoured the 3d modelling sites for a model of the plastic DJI eyepiece.
I found two, each of which models some parts of the eyepiece but neither is up to the job.
I then spent a day learning Design X so I could convert the STLs of these models into NURBS because I’m not good with meshes in CAD. That’s time I’ll never get back. Design X didn’t want to cooperate and never explained what I did wrong. Looks like I need to RTFM for Rhino 6 mesh tools which I should have done in the first place. All this was because meshes look very complex in CAD and it’s a headache cutting out geometry for a remix.
Finally, I’ll have to address the problem that the lenses will be much closer to my eyes than the DJI ones, which will lead to eyelash streaks smearing the glass. Fortunately there are off-the-shelf solutions like thicker face and forehead pads which are on order, and meanwhile I can use 3D printed versions. Or I can shave off my eyelashes with the dog trimmer.
That was most of my weekend and I’ve so far only spent £5 on a 22mm forstner bit.
Prescription lens inserts start at $75 but nobody makes them in my prescription.
It’s possible to set the dioptre adjustment on the Goggles to -6 and knock that off the insert prescription. But why do that when you can DIY and learn something along the way?
