Creation and Improvement of the Primary Standards for Light Measurements at VNIIOF

At the beginning of 2024, the Federal Agency for Technical Regulation and Metrology created a commission to conduct State Tests of the improved State Primary standard of units of luminous intensity and luminous flux of continuous radiation – GET 5–2012. The work of the commission to conduct State Tests of the improved GET 5–2012 took place on February 29, 2024 on the territory of the Federal State Budgetary Institution “VNIIOFI” (Moscow). The functions of creating a reference base for metrological support of light measurements were transferred in the early 80s of the last century from D.I. Mendeleev VNIIM institute to VNIIOFI, where by that time the reference base for optical radiometry of both coherent (laser) and incoherent continuous spectrum radiation, the last is based on models of high-temperature black bodies, had been successfully developed. The reason for this event was the adoption by the BIPM of a new definition of the unit of luminous intensity – the candela, which linked it with energy units by the luminous efficiency coefficient Kcd = 683 lm/W, which today is one of the seven defining constants of the international system of units SI. Over the past almost half a century, since the start of work in the field of light measurements at VNIIOFI, the primary standard of luminous intensity has undergone significant changes and modernizations, and has taken part in international comparisons of luminous quantities (luminous intensity, luminous flux, light sensitivity of photometric heads). The article is devoted to the analysis of the modernization of the primary light standard and the results of its capabilities at the present time.