This Instructable shows you how to make a VR viewer like Google's Cardboard but optimized for tablets. Apart from the tablet, the cost is very low. It uses two pairs of reading glasses from a dollar store (Dollar Tree), a plastic shoe box, and a pair of inexpensive prism lenses costing about 7 dollars. The result is a very effective device due to the higher resolution and larger field of view of a smartphone.
Step 1: Some Background Information
I created this device in order to get students in and out of the classroom to use VR technology for their education. Since I am a teacher in Salinas, CA, I am naming this the Salinas VR viewer.
Google’s Cardboard inspired this viewer, but it was made to address several major shortcomings of trying to make a viewer with a larger display then that of a smartphone. One would think that all that is needed is to scale up the size of the viewer, but there are several problems with this approach.
One major problem is that, like Cardboard, such a viewer would use only a simple pair of convex lenses to view the display. However, this cannot be effective because the large display size means that the images cannot be placed (optically) directly in front of each eye. If this were not corrected, then a person would have to be able to shift each eye away towards the directions of one’s ears. My viewer solves this problem with the use of inexpensive prism lenses that shift the image so that it is optically directly in front of the viewer’s eyes.
Another issue with using simple round convex lenses is that they are just too primitive to allow for a VR experience. Such lenses have a very constrained viewing area in that the eye must be placed very close to the lens and thus limit any motion of the eye. Such a limitation on how we move our eyes is not natural. Its hard to see how much fidelity a VR system can have if it makes a person keep his eye rigidly looking straight ahead in an effort to maintain the image in focus. Humans must be allowed to move their eyes and still see the VR image. Luckily, some lenses have evolved to be as optimal as possible for humans to use; i.e. reading glasses. These glasses allow for a wide FOV, and with a very large viewing area. These glasses are also extremely inexpensive.
Step 2: Equipment:
1 Scribe: Made by you.
Made with a #90 wire nail, and some plastic folded over and stapled. It allows you to scribe, which marks and very nicely allows for cutting with either a box cutter or a sharp pair of scissors.
2 Pairs of 3.25 magnification Wide Frame Reading Glasses: Dollar Tree
Price: 2.00 Dollars. This is quite a bargain. At other stores, such as pharmacies, they are hard to find, and sell for much more (+ 10.00 per pair).
1 pair of 1.5 Prism Wedge lens Pair: Berezin Stereo Photography Products http://www.berezin.com/3d
Price 7.95 Dollars for the pair.
1 Plastic Shoebox: Amazon: Whitmor 6362-2691-4 Clear Vue Collection Women's Shoe Box by Whitmor
Price: $11.99 You need 1 box, but you get a set of 4. You can make at least 6 viewers using 3 boxes, and use the other box for the other plastic parts apart from the Casing (the plastic shell)
1 roll of Glue Dots (Advanced Strength):
Price: about 5 dollars. Without this amazing glue, the viewer would not be possible. Please note you do not use it with the roller. You use a scribe (see above) to pick up the dot and place it where it is needed.
3 Templates: PDF files that you print out.
Cut and taped onto the plastic, you can then easily scribe the needed part. They are in color, but you can use the color code on the screen and still printed them in black and white.
Step 3: Cut and Join Reading Glasses.
Use a Dremel with a cutting blade (diamond works nicely), cut the handles and the nose bride off both pair of glasses. Then put Glue Dots on the edge of the glasses and on the nose bridge and stick together. Done!
Step 4: Scribe, Cut, Then Staple Side Supports.
Tape plastic over the template of the supports, and scribe using a ruler. Then cut out a support and staple it on the line indicated, then fold as shown in the picture. Repeat for the second support.
Step 5: Cut Out Prism Supports, Place in Metal Slide, Attach to Side Supports.
Cut out the prism supports, staple them on the marked line, then slide two of them them onto the metal strip, and bend the sides down on both end so that it fits into the support for the glasses. The metal strip is from a sliding file folder.
Step 6: Pour Hot Glue Into the Side Supports to Make Them Rigid.
Put Glue Dots on the corners of the glasses on both sides and place the glasses into the side supports. Then fill in the side supports with hot glue to make them rigid.
Step 7: Make the Casing. Cut and Scribe Plastic Shoe Box.
Cut the shoe box using the template. The shoe box is long enough to cut each end to get two casings.
Step 8: Cut and Bend Metal Strip, Place in Casing and Staple Sides.
Again using file folder metal strips, cut them to size using the template, bend them, and place inside the bottom of the casing. Fold the casing and staple the metal strips in place.
Step 9: Put Snaps on Top of Casing.
You can use any kind of snaps or even staples to finish the frame. The ones I used are plastic snaps which are about 4 dollars for 60 snaps, but you do need a special pliers that sells for about 20.00 dollars (Walmart). Metal snaps work well, and do not need an expensive tool to use them.
Step 10: Attach Prism Lenses to Prism Supports.
Take off the metal strip from the glasses and put glue dots on the prism supports. Make sure the prism lenses are position with the skinny side towards the nose, Hold the two prism lenses together and push them onto the supports. Put back the metal strip onto the glasses.
Step 11: Make Back Support, and Staple and Glue to Casing.
Step 12: Slip Optics Into Casing. Done!
To adjust the focus, move the plastic supports up or down, but be sure to put a piece of tape inside where the support passes through the case. This makes sure that it stays in position and does not slip. Try running the app "VR Fly" or "Tuscany." Make sure that your tablet has a gyroscopic sensor!