Sharpness and contrast of AR/VR near-eye displays: goniometric vs. advanced 2D imaging light measurements of the modulation transfer function (MTF)

Light measurement devices (LMD) are essential tools for developing novel display technologies as well as for quality assurance in display mass production. More complex displays, e.g. near-eye displays (NEDs), might require various LMDs in different development and production phases. Here we examine the comparability of complementary measurement principles and LMDs with respect to sharpness measurements of NEDs. Scanning goniometric MTF analysis with narrow field of view (FOV) and high angular resolution (300 pixel per degree) are compared to one-shot MTF analyses with wide FOV and moderate angular resolution (30 pixel per degree). The two different measurement principles can provide identical or complementary MTF results, depending on the sharpness of the device under test (DUT). Every component within each measurement system has an associated modulation transfer function and, as a result, contributes to the overall MTF of the system. Here, we examine the possibilities to remove the MTF contribution of the measurement devices to achieve fast and accurate sharpness measurements of the DUT. Experimental data from these measurement principles are compared, emphasizing sharpness measurements on LCD and OLED displays of Virtual Reality (VR) headsets. Different sharpness regimes are discussed with respect to comparability and sharpness characterization of DUTs using measurement devices with high and moderate angular resolution.