Infrared visibility and infrared visibility range: the practical signif cance and method for measuring

Abstract

New physical quantities are presented – infrared visibility and infrared visibility range. The relevance and demand for measurements of these quantities is shown. Their physical meaning is revealed, formula ratios for the calculation are given, and the practical signifi cance. The presented calculation ratios are obtained on the basis of the transformation of the real thermal portrait of the object into an equivalent thermal geometric model. It is shown that the numerical values of the infrared visibility index for various real objects can vary over a wide range: from zero for absolutely non-thermal contrast objects to values of several units for high-contrast objects, i.e. within 0.5–2.5. The ratio for the infrared visibility range is obtained in based on the Lambert-Bouguer-Beer law and Fechner's law, used in the theory of sensory sensitivity. A detailed description and procedure for measuring the indicated physical quantities is presented, examples are given, and the measurement uncertainty is estimated. The introduced values are aimed at ensuring the unity of the assessment of thermal protection of various man-made and biological objects and allow developing preventive measures for their thermal protection at the stage of commissioning.