Circular Truncated Conical Mirror with Cavity Shape and Inner Reflection for Concentrating Diffused Light to Collector Mouth from a Half Celestial Sphere

  • Mitsuhiro Matsumoto


In this study, we designed a circular truncated conical mirror to concentrate diffused light to the collector mouth from a half celestial sphere and evaluated its performance. The conical mirror has a circular truncated cone-shaped cavity, which reflects light on the cavity’s inner surface. The top of the truncated cone shape is the incident mouth, the bottom is the collector mouth, and the sides are the mirror surfaces. The incident mouth size is smaller than the collector mouth size. All light incident on the incident mouth is either reflected or not reflected on the mirror surface to reach the collector mouth. Light incident at a shallow angle to the central axis of the conical mirror is not reflected on the mirror surface, while light incident at a deep angle is reflected on the mirror surface. The conical mirror can concentrate all diffused light incident at the incident mouth from a half celestial sphere of 360◦ in the horizontal direction and 180◦ in the vertical direction to the collector mouth. A coordinate system is established for the conical mirror, and a design method is proposed. Using our design method, the conical mirror is manufactured from the determined design values. A plane mirror, concave mirror, compound parabolic mirror, and Fresnel lens, comprising the conical mirror, are used as the measured objects to compare the manufactured conical mirror performance. An experimental setup is constructed to evaluate the performance of the measured objects. Using the constructed experimental setup, diffused light is irradiated to the measured objects as scattered light. The illuminance of the light concentrated in the collector mouth of the measured objects is measured for the irradiated diffused light. The measured illuminance is then used to compare and evaluate the light-concentrating efficiency of the measured objects.


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How to Cite
Matsumoto, M. (2021). Circular Truncated Conical Mirror with Cavity Shape and Inner Reflection for Concentrating Diffused Light to Collector Mouth from a Half Celestial Sphere. Journal of the Institute of Industrial Applications Engineers, 9(2), 40.