<title>Metrological control for measuring transmission and reflection light factors of photometring materials</title>

Abstract

The photometric characteristics, especially the transmission and reflecting light factors of the materials are used widely and require accuracy and unity measurements during manufacture, usage and at studying their change under various factors. All the photometric devices and instruments intended for measuring the transmission and reflection light factors of the materials are graduated and checked in the period of operation with the use of sets of light filters and plates with known transmission and reflection factors respectively. Referred to the requirements to be met by these photometric devices and measuring facilities are spectral composition of light source radiation and spectral correction of the radiation flux falling onto the receiver. These requirements should be in compliance with the curve of relative spectral light effectiveness V (A) . That is why, the standard light filters and reflecting plates employed for the metrological control of these types of measurements must possess nonselectivity with respect to the spectral composition of radiation falling on them, as well as chemical and light damage resistance, heat resistance and mechanical strength. The sets of the neutral light filters used in the USSR are principally plane-parallel plates made of neutral homogeneous glass having various thickness and sizes. The filters reveal various transmission factors in a range from 0.0 1 to 0.92 and serve to check the photometric scale of devices and instruments.