Light Guide Design Principles

A general theory of optical transport systems has been developed that can be used to determine preliminary designsspecifications for light guide systems. Several generic light guide types are analyzed, including hollow reflective lightsguides, prism light guides, solid dielectric and fluid-filled light guides, lens guides, and open light wells. Minimumstheoretical aperture requirements are determined for each type as a function of the specified optical transport efficiency andsdesign parameters (light guide length, transmitted luminous flux, etc.). Generally, a systems aperture requirement wouldsbe inversely related to its cost. Solid dielectric (e.g., optical fiber) light guides would be very compact and practical forsretrofit applications, but their high cost would preclude their use for long-distance optical transport. Open light wellsswould be the simplest and least costly option, but would require the greatest aperture area. Hollow reflective light guides,sprism light guides, or lens guides may offer the best compromise between cost and space requirements. But in order tosachieve optical concentrations and efficiencies near the theoretical limit, the collector system would need to maintainsoptical and tracking tolerances exceeding the capabilities of existing systems, so further advances in core daylighting willsrequire improvements in collector technology.