The world of optics and lens manufacturing has traditionally been closed off to non-experts. Modeling clay for kids 7 years doesn’t have to be that way. Using rapid prototyping tools like 3D printers and CNC routers, making a lens is easier than you might think. You can use the technique outlined in this Instructable to make very large lenses, lenses that produce special effects, and sculptural lenses with freeform shapes.
I made my first lens while building a projector for a robotic sculpture. I built the sculpture’s projector assembly myself and was unable to find a projection lens that fit my requirements. Every commercially available lens was either too small or too expensive. Since then I’ve become obsessed with perfecting this technique. I developed best practices for cutting lenses on CNC routers, learned how to print optics on 3D printers, and created a polishing technique to increase optical clarity. Most recently, I used the facilities at Autodesk’s Pier 9 Workshop to fabricate a series of face-distorting lenses for a public art festival. Designing good lenses is hard, but designing fun lenses is easy!
It helps to see how a lens design performs before getting your hands dirty with real objects. Luckily, computers are good at simulating lenses. You can use any 3D modeling package with a ray tracing mode to test out your lens before you fabricate it. There are many software packages out there that do ray tracing, including some free ones. It costs money, but its T-Splines plugin makes it dead simple to design smooth lens geometries. The 90-day trial is enough for most projects.
Any modeling software with ray tracing will do. You could use Fusion 360, Blender, Maya or whatever else the kids are using these days. Read a tutorial for setting up a ray-traced glass material in your program. The steps may vary depending on what software you use. I found a Rhino blog post and used that. The setup for your lenses will be the same as for glass except for one thing: the index of refraction.
It turns out that plastic bends light differently than glass so you need to tweak this value. You’ll need to change the index of refraction on your material from 1. If you’re following my milling tutorial, use 1. If you’re 3D printing with Vero Clear, use 1. Now that you’re set up, start applying the material to different geometries and see the results.