Performance Evaluation of Elliptical and Multi-part Mirrors for Concentrating Diffused Light onto Collector Surface from Half Celestial Sphere

  • Mitsuhiro Matsumoto Kanagawa University


An elliptical mirror has a mirror surface at the first focal point on a plane perpendicular to its central axis, which, in turn, passes through the first and second focal points. It can collect diffused light from a half celestial sphere, which extends 360◦ in the axial rotation direction and 180◦ in the axial direction at the second focal point. An elliptical mirror allows only the light incident on the first focal point to be concentrated on only the second focal point. A single elliptical mirror consists of only one elliptical mirror. A multi-part mirror is composed of multiple elliptical mirrors. In a multi-part elliptical mirror, the first focal point lies on its surface, and the second focal point is so positioned that it is aligned with the top of the multi-part mirror. A multipart mirror can concentrate diffused light from a wider area than a single elliptical mirror because its first focal points are dispersed. Furthermore, in a single elliptical mirror, only the light incident on the first focal point is
concentrated on only the second focal point; therefore, the light-concentrating efficiency is low. In this study, we installed a collector surface on the second focal point of an elliptical mirror to increase its light-concentrating efficiency. Subsequently, we evaluated single elliptical and multi-part mirrors that capture the diffused light from a half celestial sphere not incident on the first focal point and concentrate it on the collector surface as well as the second focal point. We configured a coordinate system for the design of single elliptical and multi-part mirrors and subsequently analyzed the mechanism by which the light will strike these designed mirrors and concentrate on their collector surfaces. Based on the design values, we manufactured actual single elliptical and multi-part mirrors, which were illuminated with diffused light, and measured the illuminance of the light concentrated on their collector surfaces. Finally, we evaluated the light-concentrating performance of these mirrors based on the analysis results and measured illumination.


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How to Cite
Matsumoto, M. (2021). Performance Evaluation of Elliptical and Multi-part Mirrors for Concentrating Diffused Light onto Collector Surface from Half Celestial Sphere. Journal of the Institute of Industrial Applications Engineers, 9(4), 102.