MTF Analysis of Augmented-Reality Waveguide Devices

Grating-based waveguides have come to dominate the field of Augmented & Mixed Reality (AR & MR). The ultimate test of these devices is to obtain a good reconstruction of the digitally generated image at the retina of the user of the device. This aspect of the performance is typically characterized through the modulation transfer function (MTF), which quantifies the resolution capabilities of an imaging system. Unlike eye-box uniformity (another vital measure of the quality of an augmented reality gadget, since low uniformity can cause extremely uncomfortably strobing and flickering effects), the MTF is extremely sensitive to the temporal coherence properties of the source as well as any diffraction which may evolve, not just in the last propagation step to the retina (a given, since we are propagating into a focus), but also, crucially, also diffraction that evolves upon propagation inside the waveguide (typically caused by truncations at the boundaries of grating regions).

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