Photon flux calibration of LED in horticulture lighting

The LED market in horticultural lighting is growing rapidly, and there is an increasing demand for horticultural LED calibration. The evaluation of LED lighting for plant growth needs to be based on photon systems, such as photon flux (PF) rather than a photometry system which is used to evaluate how bright a LED is for human eyes. The integrating sphere and spectroradiometer are selected as the key instrument of the test system for LED photon flux calibration. Standard and improved calibration methods are presented. The standard method includes calibration of the test system, verification, spectral absorption correction, and measurement of the test LED lamp. The improved method simplifies the absorption correction in the calculation. Three LED lamps for plant growth are calibrated by the two methods, and the photon flux scale is traced to total spectral radiant flux (TSRF) standard lamps with the relative uncertainty Urel = 2.5% (k = 2).