I recently purchased one of the many inexpensive "improved" Google Cardboard headsets. On eBay these devices are priced in the same range as the real Google Cardboard but offer a more robust build quality and better optical adjustments. The largest drawback is the lack of setup and use instructions, therefore I have included my setup process and what I have found to work with the headset.
Step 1: Parts
- 1X Smartphone virtual reality headset ($20)
There are an extraordinary amount of devices on the market considering how little time has passed from the release of Google Cardboard. They can be found on eBay, Amazon, DealeXtreme, ... The device should offer adjustable focus and interpupillary distance (IPD or PD). Larger lenses are normally better because they offer a larger field of view. It should also be comfortable to wear, but that is a little hard to tell before purchasing.
I ended up with a Davyci from eBay mainly because of the large coated glass lenses and the $15 price with shipping.
- 1X Super new fancy smartphone ($$$$)
The VR headsets uses a smartphone in split screen mode to produce an image for the left and right eye. This process works reasonably well if the screen resolution is large enough (1080 works, 1440 is better, ...) and the phone is fast enough. If you are not sure, install the Cardboard demo and check its performance before purchasing a headset.
I used an Android Nexus 5.
Step 2: Focusing the Lenses
Install the Google Cardboard demo and scan the QR code (two-dimensional barcode) for your headset during setup. A later step will cover the generation of a custom QR code for your device. If you do not have one, leave it as default for now. The QR codes reference lens profiles for the headsets that correct for barrel distortion, field of view, and interpupillary distance (IPD).
Turn on the google cardboard demo and place the smartphone in the headset so the center line is under the vertical dividing plate in the headset and the image is centered top to bottom in the viewer. locate the lens focusing mechanism and figure out how to operate it. My set had four screws that needed to be loosened and then the lens tray slid. Look into the headset making sure the lenses are horizontally aligned with your eyes. Now focus the lenses in and out until the the sharpest image with a good field of view is achieved. If your unit is like mine, tighten the four screws making sure not to change the focus. I obtained the best result with the lenses closest to my eyes.
Step 3: Adjusting the Interpupillary Distance
The interpupillary distance (distance between your eyeballs) setup is critical for creating a convincing 3D image and preventing double vision. There are several ways of measuring your unique distance. The fastest way is if you already have the measurement from an eyeglass prescription. It will probably be in the range of 65mm and is normally abbreviated IPD or PD. You can measure it several ways, these are good instructions using a ruler and a mirror. What worked best for me was using a pair of binoculars with adjustable IPD distance. Use the binoculars to focus on an object in the distance. Adjust the IPD spacing until a good three dimensional image without double vision is obtained. Now measure the distance between the lenses on the end you looked through. This is your IPD and will be used throughout the rest of the setup.
Set the lenses in the headset to your IPD. If they can be independently moved, measure from the center vertical dividing plate out one half of your IPD to each lens. If not, set the distance between the lenses to your IPD. The idea is to obtain the same lens spacing that was comfortable when using the binoculars.
Step 4: Lens Correction (Generating a QR Code for Google Cardboard)
Create a custom correction profile for your lens, headset, IPD combination. On a computer go to the Google Cardboard viewer profile generator site and follow the instructions to create a custom QR code for your headset. The inter-lens distance is your IPD. Scan the new QR code using the Cardboard app to set your viewer to the new settings.
The Cardboard demo app should now look 3D without double vision. It is critical that the phone be centered correctly in the viewer! Place the smartphone in the headset so the vertical center line is under the vertical dividing plate in the headset and the horizontal center of the image, on the smartphone screen, is lined up with the horizontal center of the lenses. Also adjust the viewer on your face to center your eyes with the lenses. You will notice more chromatic aberration (fringes of color) as your eyes become off-center from the lenses.
Step 5: Other Modifications and Uses
When my headset first arrived it fit quite poorly and needed some modification. The area around the nose was enlarged and more foam around the sides of the headset was added. Washers were also added to the screws holding the lens focusing mechanism to allow for easier adjustment and securing. Tape was added between the lenses and support to fill a gap that was letting light from the screen through.
I have been experimenting with the headset as a 3D screen for my desktop computer. This is possible using Trinus VR, a program that runs on the computer and streams content to the smartphone. There is a trial version that I'm currently testing, or the full version can be purchased for $6.49. Follow the setup instructions on the website. You will need to generate a lens/headset profile with the computer program.
At this point I have been able to stream movie content from YouTube and Netflix and play games that support 3D rendering using the headset and Trinus VR.