Evaluating the general V(λ), mismatch spectral quality factor index ƒ₁ and the uncertainty of photometers

Abstract

The general term photometry refers to the measurement of light and its perceived brightness; it can be applied to various purposes, including lighting design, display calibration, and the setting of safety standards. A device used for measuring light is called a light meter or photometer. Ideally, such devices should have a spectral responsivity-that is, they should respond to light in a way which mimics the human eye's sensitivity to different wavelengths. The sensitivity of the human eye is described by the Commission Internationale de l'Éclairage, CIE, luminous efficiency function, V(λ), a plot of the sensitivity of the eye versus wavelength over the visible region, from violet, approximately 380 nm, through red, approximately 780 nm. In practical applications, it is usually preferable to detect light with silicon or selenium photodetectors and measure the electrical current generated. These photodetectors are sensitive to a wide range of wavelengths, including those outside of the visible spectrum: ultraviolet (UV) and infrared (IR). However, due to its nature, the spectral responsivity of silicon and selenium photodetectors is also different from that of the human eye. For example, silicon photodetectors are much more sensitive to infrared radiation, which is imperceptible to human vision. This in turn leads to erroneous light measurements when using the direct raw response of the detector. The spectral quality factor and , indicating the mismatch between the spectral responsivity and the CIE luminous efficiency function V(λ), is the most crucial characteristic of photometers. The general mismatch index , denoted as V(λ), delineates the disparity between a photometer's relative spectral responsivity and the spectral luminous efficiency function for photopic vision, V(λ). It's highly probable that photometers will adopt white light-emitting diode (LED) sources as calibration references going forward. This transition may necessitate refining the general V(λ) mismatch index's definition, possibly through alternative normalization methods for or by introducing a different assessment function for evaluating mismatches . In this research, spectral quality factor for the photometer NIS-2 has been determined with value 3.8%. This percentage value is classified the photometer NIS-2 as medium quality. The uncertainty was determined through a calculation performed using my Microsoft Excel program, and the final value obtained is 0.010.