Application of two models of non-ideality of sources to increase the accuracy of luminous intensity measurements

On the example of experimental studies of the luminous intensity of several light sources, it is shown that there are significant deviations of the luminous intensity dependence from the inverse-square law. Two models for estimating the luminous intensity for non-point light sources are proposed, theoretically studied and experimentally verified: the model of distance refinement and the model of additional sources. In the first model, a constant correction is added to the distance measurement result. It can be determined provided that there is a maximum possible constancy of the estimate of the luminous intensity as the product of the measured illuminance and the square of the measured distance for different distances between the receiver and the source. In this case, the correction is constant, and the estimate of the luminous intensity depends on the distance between the source and the receiver. Alternatively, the luminous intensity and the correction to the measured distance can be determined by minimising the deviations of experimentally measured illuminances at different distances from the calculated ones. In this case, a constant luminous intensity and a constant distance correction are determined. The second model is based on the assumption that deviations from the inverse-square law arise because of additional sources, such as reflections from screens, radiation traps, lamp glass, and others. In this model, the distances between the lamp filament and all additional elements are assumed to be known, and the luminous intensity estimates of additional sources are calculated provided that the deviation between the calculated and measured illuminances at different distances is minimised. The considered models have been experimentally verified. The advantages and disadvantages of the models have been analysed, and recommendations for assessing the quality of the procedure for luminous intensity measurements have been given. Based on these models, it is proposed to develop a procedure that would allow assessing the quality of the installation for luminous intensity measurements.