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Inter-reflection Compensation by Screen Reflectance Modulation

We propose a novel inter-reflection compensation technique for immersive projection displays wherein we spatially modulate the reflectance pattern on the screen to improve the compensation performance of conventional methods. As the luminance of light reflected on a projection surface is mathematically represented as the multiplication of the illuminance of incident light and the surface reflectance, we can reduce undesirable intensity elevation because of inter-reflections by decreasing surface reflectance. Based on this principle, we improve conventional inter-reflection compensation techniques by applying reflectance pattern modulation. We realize spatial reflectance modulation of a projection screen by painting it with a photochromic compound, which changes its color (i.e., the reflectance of the screen) when ultraviolet (UV) light is applied and by controlling UV irradiation with a UV LED array placed behind the screen. The main contribution of this paper is a computational model to optimize a reflectance pattern for the accurate reproduction of a target appearance by decreasing the intensity elevation caused by inter-reflection while maintaining the maximum intensity of the target appearance. Through simulation and physical experiments, we demonstrate the feasibility of the proposed model and confirm its advantage over conventional methods.

Proposed technique compensates for the inter-reflections of a projected image onto a concave immersive projection screen: (left) prototype system comprising a projector, an RGB camera, a screen painted with a photochromic compound, and UV LED arrays that control the reflectance pattern of the screen; (middle-top) projected result of the dog image obtained using the proposed method; (middle-bottom) reflectance pattern displayed on the screen (rectified using homography); (right) close-ups of projected results and the pseudo-color visualizations of their intensity values. There are two areas in the direct method's result where undesirable intensity elevation is found, i.e., around the nose of the dog and around the left eye. While the projection only (conventional) method can compensate for the elevated intensity in the nose area, the proposed method can compensate for the elevated intensity in both areas.

Publications

  • Shoichi Takeda, Daisuke Iwai, and Kosuke Sato, "Inter-reflection Compensation of Immersive Projection Display by Spatio-Temporal Screen Reflectance Modulation," IEEE Transactions on Visualization and Computer Graphics (Proceedings of IEEE Virtual Reality 2016), Vol. 22, No. 4, pp. 1424-1431, 2016. [suprementaly material]
  • Shoichi Takeda, Daisuke Iwai, and Kosuke Sato, "An Immersive Projection Display with Dynamic Reflectance Control Using Photochromism," In Proceedings of IEEE Global Conference on Consumer Electronics (GCCE), pp. 57-58, 2014.