It has been a very long time since I did the original optical measurement of then-current VR headsets. I have owned a PlayStation VR headset (PSVR from now on) for almost a year now, and I finally got around to measuring its optical properties in the same way. I also developed a new camera calibration algorithm (that’s a topic for another post), meaning I am even more confident in my measurements now than I was then.
One approach to measuring the optical properties of a VR headset, which includes measuring its field of view, its resolution in pixels/°, and its lens distortion correction profile, is to take a series of pictures of the headset’s screen(s) through its lenses using a calibrated wide-angle camera. In this context, a calibrated camera is one where each image pixel’s horizontal and vertical angles away from the optical axis are precisely known.
If one then displays a test pattern that lets one identify a particular pixel on the screen, one can measure the viewer-relative angular position of that pixel in the camera image, which is all the information needed to generate the projection matrices and lens distortion correction formulas that are essential to high-quality VR rendering.
Without further ado, here is a series of 7 images taken with the camera lens at increasing distances from the headset’s right lens (Figures 1-7, and yes, I forgot to clean my PSVR’s lens). The camera was carefully positioned and aligned such that it was sliding back along the lens’s optical axis, and looking straight ahead. The first image was captured with an eye relief value of 0mm, meaning that the camera lens was touching the headset’s lens. The rest of the images were captured with increasing eye relief values, or lens-lens distances, of 5mm, 10mm, 15mm, 20mm, 25mm, and 30mm: Continue reading