This is my take on the Google Cardboard idea – a frame with lenses that very inexpensively turns your phone into a pair of VR goggles, like a very low budget Oculus Rift. Google Cardboard is very bulky though, and makes it hard to use the touchscreen while the phone is inside. It's also impractical to transport. So I made this.

Features:

• collapsible – it's only slightly larger than a Galaxy Note 2 when collapsed
• add a magnet (diameter 20mm or less) and a washer (diameter 20mm) for a magnetic switch (to interact with apps via the phone's magnetometer) like the one that Google Cardboard offers
• uses inexpensive Google Cardboard lenses (e.g. from eBay, see below)
• lenses can be focused individually
• attachment points for a head strap
• compatible with Google Cardboard apps
• frame can be adjusted to six different phone sizes (1 to 6) – a LG G2 sits at size 3, a Galaxy Note 2 at size 5
• display stays accessible (mostly; i wouldn't type a text on it, but selecting things works fine)

What you need to print:

• the frame (...-scr-mag.stl)
• four arms (...-arm.stl)
• two lens holders (...-ring.stl)
• (optional) one holder for the magnetic switch (...-magnet.stl)

What you need to buy:

• Lenses: Google Cardboard compatible biconvex lenses, diameter 25mm, focal length 45mm (search on e.g. eBay)
• (optional) any flat magnet with a diameter of 20mm or less
• (optional) a washer or flat disc of ferromagnetic material with a diameter of 20mm

Test prints were done using ABS filament. You may have to rescale when printing with PLA to account for shrinking with ABS.

Notes:

• One of the focusing screw threads turns clockwise, the other counter-clockwise. I might make both go the same way in a future revision.