  Most commercially available optical see-through head-mounted displays
(OST-HMDs) utilize optical combiners to simultaneously visualize the physical
background and virtual objects. The displayed images perceived by users are a
blend of rendered pixels and background colors. Enabling high fidelity color
perception in mixed reality (MR) scenarios using OST-HMDs is an important but
challenging task. We propose a real-time rendering scheme to enhance the color
contrast between virtual objects and the surrounding background for OST-HMDs.
Inspired by the discovery of color perception in psychophysics, we first
formulate the color contrast enhancement as a constrained optimization problem.
We then design an end-to-end algorithm to search the optimal complementary
shift in both chromaticity and luminance of the displayed color. This aims at
enhancing the contrast between virtual objects and the real background as well
as keeping the consistency with the original color. We assess the performance
of our approach using a simulated OST-HMD environment and an off-the-shelf
OST-HMD. Experimental results from objective evaluations and subjective user
studies demonstrate that the proposed approach makes rendered virtual objects
more distinguishable from the surrounding background, thereby bringing a better
visual experience.
