|Homemade Cardboard Viewer, rear view phone mount area|
As a device to view 3D photos, the Google Cardboard VR (Virtual Reality) viewer has its limitations. The lenses do not have enough field of view to completely see a side by side (parallel) 3D photo that fills the entire display on a phone. I think the design intention was to have an immersive experience and that the cardboard wearer would move to view an entire image as it shifts corresponding to head movement. Cardboard is foremost a Virtual Reality viewer, not a stereoscope.
Berezin Stereo Photography Products has a rectangular lens (product 3791) with a better field of view for viewing parallel 3D photos on phones. Having used this lens with my phone I found the experience viewing 3D photos much better than with the Cardboard lenses. This lens has very little barrel distortion so software corrections are not needed.
|Berezin 3DVu Lens, before hacksawed in half|
The Berezin 3D viewer lens come in a plastic frame that does not have enough lens separation for Cardboard. I solved this by cutting the frame in half with a hacksaw and mounting each frame half and lens in my Cardboard. I did not try to remove the lens from the plastic frame because I feared destroying the lens. Conveniently, the plastic frame provided a mounting surface to hot glue to the cardboard. I increased the distance from the lens to the phone by 38 mm, adjusting the cardboard viewer layout plans before I cut out my custom version.
I'm very pleased with the resulting stereoscope. My 3D photos look much better when Cardboard is used as a simple stereoscope because I can see the full screen image without moving. I also found my modified viewer better for looking at photo-spheres and other VR Cardboard apps with head movement too. The trade off for my Cardboard viewer with the Berezin lenses is that the screen is not fully immersive for virtual reality, that is, I can see the black walls inside the viewer. But I did not find this to be a distraction.