Eye accommodation vs projected image distance

PCO team elaborated test methodology of the display, designed in a manner to examine parameters of projected image. Most important parameter to verify is projected image virtual distance as perceived by human observer, as it guarantees the lack of eye accommodation while switching between virtual and real image. For this purpose a distance assessment device utilizing a Raspberry Pi camera with motorized focus was built. The principle of operation is sweeping across the full range of the focus and searching for the best focus plane. The focus itself is quantified by calculating Laplacian of the image, which is sensitive to rapid intensity jumps, as it represents second derivative. After preliminary calibration of the system which finds the relation of control signal values with known actual distance of test target, the system is capable of determining the distance of any target which contains visible edges with some precision.