tailieunhanh - Nonimaging Optics Winston Episode 3

Tham khảo tài liệu 'nonimaging optics winston episode 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Light Cones 49 Figure The cone concentrator. LIGHT CONES A primitive form of nonimaging concentrator the light cone has been used for many years see . Holter et al. 1962 . Figure shows the principle. If the cone has semiangle g and if di is the extreme input angle then the ray indicated will just pass after one reflection if 2g p 2 - di. It is easy to arrive at an expression for the length of the cone for a given entry aperture diameter. Also it is easy to see that some other rays incident at angle di such as that indicated by the double arrow will be turned back by the cone. If we use a longer cone with more reflections we still find some rays at angle di being turned back. Clearly the cone is far from being an ideal concentrator. Williamson 1952 and Witte 1965 attempted some analysis of the cone concentrator but both restricted this treat 50 Chapter 4 Nonimaging Optical Systems ment to meridian rays. This unfortunately gives a very optimistic estimate of the concentration. Nevertheless the cone is very simple compared to the imageforming concentrators described in Chapter 3 and its general form suggests a new direction in which to look for better concentrators. THE COMPOUND PARABOLIC CONCENTRATOR The flat absorber case occupies a special place because of its simplicity. Historically it was the first to be discovered. For these reasons its description and properties merit a separate discussion. If we attempt to improve on the cone concentrator by applying the edge-ray principle we arrive at the compound parabolic concentrator CPC the prototype of a series of nonimaging concentrators that approach very close to being ideal and having the maximum theoretical concentration ratio. Descriptions of the CPC appeared in the literature in the mid-1960s in widely different contexts. The CPC was described as a collector for light from Cerenkov counters by Hinterberger and Winston 1976a b . Almost simultaneously Baranov 1965a and Baranov and Mel nikov .

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