Transmissive Measurement Procedure Using a ColorimeterĪ colorimeter can be used to establish X, Y and Z values for transmittance based on the required test setup. Overview of transmissive measurement procedure using a Hera spectrometer and halogen light source. However, when measuring VIS and NIR, a halogen tungsten light source is ideal.įigure 3. For example, a halogen tungsten light source is not appropriate for measuring UV transmittance as the output in this region is very limited, thereby resulting in a poor signal noise-ratio. A spectrometer is capable of accurate measurement of transmittance for each wavelength.Ī different light source may be needed depending on the type of object to be measured. As not all wavelengths are transmitted through an object equally, it is essential to measure these properties, such as when measuring a material’s UV blocking properties. Transmissive Measurement Procedure Using a SpectrometerĪn object’s features can be clearly measured using a spectrometer and a broadband reference standard. A halogen source would be more suitable for this application. a high pass filter for wavelengths 700 nm. Various light sources can be used to match spectral properties of the object to measure - e.g. A colorimeter, spectrometer or light meter is used for X, Y, Z measurements, complete spectral measurements, or Y (luminance) measurements, respectively. ![]() Emitted light is split into absorption, transmission and reflection.īased on the object’s spectral properties, various transmissive measurement setups can be used. It is not possible to measure absorption and reflection using setups and tehniques illustrated in this article - these can only be derived as a sum from the collected data using equation 1.įigure 2. The detector can only measure the object’s transmission. The deviation between these three variables is defined by the characteristics of the object.īased on the conservation of energy, it can be established that the total amount of light emitted by a light source directed towards an object is equal to the sum of absorption α, transmission τ, and reflection ρ of a particular object (equation 1). Transmissive measurement setup with halogen light source and spectrometer to measure an object’s transmission.įor all translucent objects, some of the light is absorbed, some is reflected, and some is transmitted. The spectral transmittance, τ(λ), of an object is expressed as the ratio of transmitted spectral flux, Φ λt, emitted by a light source and an incident flux, Φ λi, which can be measured with a detector.įigure 1. Figure 1 illustrates a sample setup for transmissive measurements of an object (e.g. When precise transmissive measurements are required, a detector and reference standard light source are used to measure transmittance of an object. ![]() Finally, some basic recommendations are given to ensure precise measurement results. This article details transmissive measurements, before discussing several applications of transmissive measurements. The deviation between these measurements defines the properties of the translucent object. There are generally two steps to transmissive measurements - measuring the reference standard light source with and without a translucent object to collect a baseline.
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