I purchased a cheap Google Cardboard viewer from ebay, but soon after using it I decided to build my own. It was annoying how I had to keep moving the viewer just to see the whole screen. I realized this was because the distance between the lenses on the Cardboard was about 60 mm, while my eyes were 69 mm apart. The other issue was that the radius of the curve of the mask was too large, so I couldn't get a good fit.
Another reason you should think about building your own is that the standard template might not fit your phone. The Cardboard was the right size for my Samsung Galaxy S5, but it's possible it won't fit all phones. That should be more than enough to start building.
Step 1: Prepare Materials and Tools (Updated).
An old cardboard phone box. The box for my older phone, a Samsung S2 LTE, was almost the same size as my S5. The cover of the box became the phone holder while the container turned into the lens holder and mask. The big advantage of the box was that the cover slides snugly over the container. This allows fine adjustments to be made between the position of the lenses and the phone, and for the phone holder to be removable from the mask.
If you do not have such a box with cover, you can build one. I think foam core board is the best material to use, possibly even better than cardboard, because it's lighter, more rigid, and easy to shape. In fact, I used some for this project and might build the next one out completely out of it. The dimensions of your box just has to be the same as your phone, while its initial depth (which you will shape to conform to your face) should be at least 4 inches. One piece of black foam core board from Dollarama should suffice.
Foam core board. I used a piece that fits tightly inside the box. This will be the lens holder.
A pair of lenses. I used the same lenses that came with the Google Cardboard I bought from ebay. If you are starting from scratch, skip the viewer and just buy the lenses. A pair of 25-mm lenses cost less than US$1; 37- mm lenses cost about twice as much.
Update: Two options I tried that you shouldn't bother with: hands-free binoculars from Dollarama (whose magnification was too weak), and loupes (which are usually only 20mm wide and too small).
Foam padding. This is needed to cushion the edges of the viewer as it sits on your face, preventing a phenomenon that is now known as Cardboard Face. As it happens, the box I used had a small piece that was enough for this purpose. But you can use any material you want.
Plastic container or similar material. This will be used for the visor that holds the viewer on your head. I used an empty bleach container.
Other materials and tools:
- X-acto cutter
- tin snips
- tacky glue or a glue gun
- velcro with sticky backing
- elastic (like the kind used on underwear)
- a pair of 3/16" bolts about 1/2" long with nuts, or brass fasteners (the kind with two legs that you spread out)
- optional: scrap balsa wood, bamboo chopstick, a sheet of black paper
Update:To control the phone while viewing: a mouse (corded or cordless) plus an OTG adapter. The cheapest adapters cost less than a dollar. Hope your phone supports OTG. A bluetooth mouse should also work.
Step 2: Shape the Box Into a Mask.
You might need help from another person to trace the shapes of your forehead and cheeks onto the sides of the box. Make an initial rough trace then cut with the tin snips, then improve it with additional traces and more precise cuts with the cutter. You can also prepare the cross-sections first on paper then transfer them to the box when satisfied.
Remember NOT to cut the arc all the way to the top of the cover. Leave behind about 1/4", or about the thickness of the foam core. This will add rigidity to the box.
If you have no one to help you, here's a good trick you sad person you: take a large piece of aluminum foil, press it against your face until you have molded it to shape. Keep this avatar for other projects.
You will also need to cut out the shape of your nose, although that doesn't need to be as precise as the outline of your cheeks and forehead. In fact, I suggest giving your nose about 1/4" of clearance. Your face sweat and breath will fog up the lenses, so you need good ventilation inside the mask.
Step 3: Measure Your Pupillary Distance (PD).
Again you need another person to help you, but you can also do this yourself. Just take a ruler and measure the distance between your pupils while looking straight ahead in front of a mirror. Once you get the number I suggest reducing it by 1 mm. This is because the distance between the images on your phone is smaller than your PD, so you will be a little cross-eyed when you use the viewer.
Step 4: Build the Lens Holder.
Take the foam core board and cut out a rectangular piece that will fit tightly inside the bottom of the container box where it will go. Then draw the cross forming lines bisecting the long and short sides of the rectangle. The centers of the lenses will fall along the horizontal axis of the cross, and will be equidistant by half your PD from the vertical axis.
Mark the centers of the lenses on both sides of the foam core board. Use a push pin or needle to make sure they line up.Trace the outline of each lens around their center on both sides of the foam core board. A math compass will help. Using the cutter, cut out a circle on each side that is slightly smaller than the lens. One side can be even smaller than the other. Do NOT cut all the way to the other side. You want the holes to be just big enough to let the lens in through one side, but still small enough to hold the lens tightly without glue.
You also need to cut the holes on the mask (bottom of box). The simplest way is to trace the holes on the lens holder onto the mask. Make this trace a little bigger than the lens, then cut out the holes.
There are two reasons I used a separate foam core board to hold the lenses (rather than affixing the lenses on the box itself, as in the original Cardboard). The first is that foam core board holds the lenses well without glue (although that may be needed later on). The second is that if needed, this lets me bring the lenses back to their to their correct position after adding padding to the mask. As with the original Cardboard, the piece holding the lenses is supposed to be in contact with your forehead.
Step 5: Build the Phone Holder.
On the cover of the box, draw a rectangle big enough to fit the screen of your phone as well as any control buttons. Make sure the screen is at the center of the cover. Cut out the hole.
In my case I had to make the hole a lot bigger because the outer cover of the box turned out to be metallic. When I made the hole just big enough to expose the screen but with the touch key buttons covered, the phone behaved unpredictably whenever I placed it on the box. When the phone is installed on the holder, you should be able to have full control of it through the hole.
To hold the phone in place, glue a piece of elastic attached vertically to the holder. I found this to be an easy way to take the phone off and back on the holder. The Cardboard uses a flap secured using velcro, which I found cumbersome. You may have other ideas.
I also added "stops" around the edges of the holder to fix the position of the phone. I made sure to leave gaps for the headphone jack, buttons, and charging port. I started with some cardboard but later I used foam core, which had more bulk. I think the corners or edges of a similar cardboard box would make even better stops but I didn't have any.
Note that the final positions of the stops at the top and bottom are different on the final product. Since you will be changing those positions during testing, glue them on temporarily until you are satisfied with their placement.
Step 6: Build the Visor.
Out of the plastic container, cut two pieces about 1-1/4" wide and about 10" long. Instead of a knife and straight edge, the best way to do this is with tin snips. Tip: Tin snips are faster, easier and safer than a knife for cutting most flat materials, including those nasty clamshell packages.
Attach the plastic straps to the sides of the mask using the bolts or brass fasteners. You'll have to test where they should go best. I chose to put them closer to the top of the mask so that the straps are above my ear when I put the mask on. When I first tried to attach them at the middle, they ended up hurting my ears.
Join the straps to each other using velcro. Tip: although the velcro has sticky backing, it will eventually come off with repeated use and will need a way to reinforce the adhesion. I used office staples, but not the stapler. Instead I marked out where they holes should be, prepunched the holes with the pushpin, pushed in the staples, then bent them in place. You can use a heavy-duty stapler, but you may still have to pre-punch the holes because you can crack the plastic.
Placing the straps closer to the top of the mask means that the bottom will tend to lift away from my face. I corrected this by attaching some elastic at the bottom of the mask to the strap. Even if the elastic covers my ears, they don't bother me as much. I used a narrower white elastic because the wide black one was too bulky.
Why not use an elastic strap instead? Some VR devices use this. I think the disadvantage is that mask plus phone is heavy, so you will need to tighten the elastic by a lot to keep it in place. Other designs solve this by adding a strap over the head, which then causes a problem called GoPro Hair. By contrast, the visor fits around your head like, well, a visor.
Step 7: Find Correct Lens-to-screen Distance.
Place the lens in their holes on the holder. Keep them parallel to each other and to the plane of the holder, then install the holder at the bottom of the container. The Cardboard lenses are bi-convex (meaning one side is rounder than the other), so be sure the flatter side is towards your eyes, rounder side towards the phone.
Place the phone on its holder, turn it on, put on the mask, then slide the phone holder on the mask. Slowly adjust the holder until you get focus. Mark this position by drawing a line along the edge of the holder around the mask. You may have to do this separately for each side, and top and bottom. Glue on temporary cardboard stops at strategic locations on the sides of the box, following the marks you made, then check again. When satisfied, attach the stops permanently.
I my case I put four stops, two on top and two at the bottom, since I wanted to leave the sides clear for the visor and other attachments.
Step 8: Attach Elastic to Fix Phone Holder to Mask.
I chose elastic to do this mainly because I had more of it and it was easy. Just glue the ends of the elastic to the sides of the mask. Warning: do not make the elastic too short because its tension can collapse the mask. This is the reason I used the narrowest elastic I had. Since the cover goes snugly over to the container, the elastic doesn't need much tension. Just set the length of elastic such that the phone doesn't change position with normal head movements.
Step 9: Add Reinforcement.
These are probably unnecessary, but I had to add them to fix my mistakes. They did make the viewer more rigid without adding too much weight.
I first had to reinforce the front of the mask with some scrap balsa wood because all the handling, testing and removal of material was causing the mask to deform. If you don't have balsa, cardboard trimmed from the box will work. Then I also had to glue on a piece of wood (takeaway bamboo chopstick will do) on the inside top of the phone holder after the part got folded when I tried on elastic that was too short.
If you decide to put on reinforcements, just make sure they don't get in the way of anything, like your view of the screen or any trimming that you might have to do to improve the fit.
Step 10: Add Some Padding and Lining.
I took the foam pad from the box, then cut it into two pieces for each side of the mask. I then cut out half-circles for my eyes, then glued them to the mask. I did have to add some foam core first to the sides of the mask so that the foam had more surfaces to attach to.
You can add more padding pretty much out of anything. Just make sure that you don't add too much weight. More important, make sure that after adding any padding you maintain the right distance between your eyes and the lenses.
I also cut out a piece of black paper which I placed inside the phone holder. After I cut out notches for the controls (most of which turned out to be unnecessary), a lot of light leaked in through them. The black paper lining fixed that.
You might notice that the hole on the frame is now closer to the bottom rather than the middle. This is because after a few tests I realized that my eyes' natural gaze is not directly forward but slightly downward. Yours may be different.
Step 11: Install a 3d Viewer App.
To watch a 3d movie, you will need an app. After testing a couple, I chose VaR's VR Video Player, mainly because of its static vertical stereo mode where you can increase the distance between the left and right images while keeping other parameters constant. You may need to adjust this distance because your field of vision is wider than your screen. Unfortunately this will also reduce the size of the image and make the experience less immersive, but it's still like being in a theatre.
Update: The Cardboard comes with a magnet for control, but there is very little you can do with it. I found out that the best way to control the phone while using it on the viewer is with a USB mouse connected to the phone with an OTG adapter. The mouse can be wired or wireless. You can in fact use the mouse with other apps. In my S5 the mouse worked immediately after I connected it to the phone with the adapter.
I also tried a cheap bluetooth controller designed for games. It works, but it is cumbersome. Like using a keyboard, you navigate the screen with four buttons and make a selection with another button. You'll be far better off with a mouse.
If your phone does not support OTG, you can probably use a bluetooth mouse (haven't tested one). But even without controls, you can focus instead on making it possible to quickly set the phone to play/pause, and put on/take off the viewer. You'll miss a few seconds of the video, that's all.
Step 12: Sit Back and Enjoy Your Movies, or Tweak Some More.
As I mentioned earlier, note how phone ended up at a lower position even if lenses are exactly along the middle of the viewer.
The outside is ugly but the view inside is excellent. I've used it to watch a 3D movie all the way without problems, and it is stable enough to enjoy a 360-degree video.
If you're like me, projects like these are never finished. The great thing about building it is that you'll know a lot better about how to go about making the next one.