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We present the results of the optical design and fabrication of a light-guiding plate (LGP) that utilizes sunlight to be adopted as an illumination system for photobioreactors. A solar daylighting system was employed as the light source for the LGP. We modeled the light sources (optical fiber exit ports of the solar daylighting system), a reflection film, and LGP patterns. An LGP (1000 mm 9 500 mm 9 10 mm) was designed and fabricated using a computerized numerical control machine. It was optimized for the average deviation of the illuminance distribution by varying the maximum pattern spacing, minimum pattern spacing, and spacing constant of the pattern spacing function expressed in the form of an exponential function. Average illuminance and uniformity of the illuminance distribution of the fabricated LGP were measured to be 8174 lx (photon flux density: 122.0 lE m -2 s -1 ) and 90.0 %, respectively.

In this paper, we report the results of a study on the design and fabrication of a light-guiding plate (LGP) using a hybrid light-emitting diode (LED) and sunlight source that can be applied to a photobioreactor.LGP patterns for the LED source were designed and engraved on an LGP, together with previously reported patterns for a sunlight source. A control system for the hybrid LGP was designed to maintain the output photon flux density (PFD) from the LGP at a constant value. When the target value of the output PFD was set to 70 μE/(m 2 ·s), the error range of the output PFD was found to be within ±2%.