NON-ADDITIVITY ERRORS IN MESOPIC PHOTOMETRY

摘要

At mesopic luminance levels, both the rods and the cones are active. Typical applications are street lighting, solid-state lighting (SSL), car headlamp lighting, emergency lighting and lighting for security purposes. Present day standards are based on the photopic spectral luminous efficiency function V(λ), which describes the luminous spectral responsivity of cone vision under photopic lighting conditions. Under mesopic conditions differences between measured or calculated values and visually observed ones occur.Visual experiments were carried out to observe the human visual detection mechanism. This resulted in a dataset which is the base of the CHC model [1] (from the abbreviation of chromatic conspicuity). The CHC model predicts spectral non-additivity of mesopic detection performance and enables the determination of threshold contrast responsivity which is for certain object chromaticities lower than predicted by the current mesopic models. This is of major importance in street lighting as the current models may underestimate the visibility threshold by several tens of percents. The CHC model (and its variant CHC_q, see the Appendix) can be a step forward to an advanced (chromatic) detection based model of mesopic photometry.