Humans use light for many functions, including illumination, security, indicators, and so forth. An esoteric but interesting aspect of light is to attract (positive phototaxis) or repel (negative phototaxis) other organisms. Fishermen make use of light attraction to lure fish into a capture area. However, after fish are initially attracted to the presented light, they soon move to the edge of the lit zone waiting for plankton to become available due to the photosynthesis from the presence of light. The fish tend to form a shoal, which is a fairly tight grouping of fish that are not necessarily doing the same activity (i.e., one fish may be moving while another is eating). Because of this noted behavior in fish due to the introduction and continued presence of light, specific task lighting could provide a well-lit region contained within a poorly lit region. In fact this structure can be replicated to create a periodic illumination distribution, such as concentric rings in angular space. In time the fish will form a shoal in interior dark rings, thus fishermen can take advantage of this knowledge.

Two types of lighting are proposed: Type I – the central region is dark and Type II – a bright central region, with each type having two concentric bright rings and the requisite dark regions. High-brightness, white-light LEDs currently available from manufacturers were used in simulation studies in which the desired intensity pattern (i.e., angular distribution, measured in cd = lm/sr) was described with a Fourier series formulation. This parameterization provided the ability to tailor an optic to change the light intensity distribution curve (LIDC) of the LED into that desired at the output from the optic. This step is accomplished with a process called energy mapping, which determines the required normal of the output surface based on the inputs of the incident ray, the refracted ray, and the index of refraction of the optic. An iterative process constructs the whole optic by stepping the input ray through the angular emission extent of the LED by approximating it as a point source emitting into a pseudo-Lambertian distribution. Enforcing conservation of energy provides a realizable optic that is efficient in the transfer of the light to the target. Experimental verification showed that 25 poecilia reticulata (guppy) would form a shoal in an internal dark ring for both optic types with increased duration under the angularly periodic illumination conditions.

Significant research has been conducted in the illumination optics area, but the bulk of this work has been for the uniformity of illumination over a specified region. This work shows that the desired illumination pattern can be tailored to the specifics of the situation, even the attraction and “trapping” of fish to a desired region. This study is an example of the power of the design of illumination systems to not only simply provide a high level of optical transfer efficiency, but to also increase the efficacy of the activity being explored. There are a large potential number of task-specific tailored lighting applications, including, but not limited to, optical pumping of lasers, illumination in retail spaces, and residential lighting that could benefit from this method.

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