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Radiometric and Photometric Measurements
Published in Lazo M. Manojlović, Fiber-Optic-Based Sensing Systems, 2022
To measure the radiant intensity of a source, the radiant flux angular distribution must be determined. Typically, in the case of a point source, radiant intensity can be measured by measuring the optical flux that impinges on the detector and certain geometrical parameters of the measurement setup. First of all, the distance between the source and the detector must be much larger than the source dimensions thus “forcing” the source to be a point-like source. If the distance is large enough, as it is presented in Figure 2.10, the radiation emitted in the solid angle Ω defined by the detector aperture area A and the distance d as Ω = A/d2 will be captured by the detector D and amplified by the signal amplifier A, so the measured flux will be Φ. According to the presented geometry of the measurement setup, the measured radiant intensity will be: I=ΦΩ=d2AΦ
Radiometry and Photometry
Published in Vasudevan Lakshminarayanan, Hassen Ghalila, Ahmed Ammar, L. Srinivasa Varadharajan, Understanding Optics with Python, 2018
Vasudevan Lakshminarayanan, Hassen Ghalila, Ahmed Ammar, L. Srinivasa Varadharajan
Radiant intensity, denoted by the symbol Ie, is the power emitted in a particular direction along the axis of a cone subtending a solid angle of 1 steradian. The unit of the radiant intensity is, therefore, W Sr−1 (Watts per steradian). Similarly, the power emitted by unit area of the surface is called the radiant emittance (or radiant exitance) and is denoted by the symbol Me. The unit of radiant emittance is Wm−2. Radiant intensity and radiant emittance can be combined to define another unit of radiometry, namely, radiance. Radiance is the power emitted by the unit area of the radiating surface in unit solid angle. The unit of radiance is Wm−2Sr−1. Radiance is denoted by the symbol Le.
Introductory Theory
Published in Robert P. Bukata, John H. Jerome, Kirill Ya. Kondratyev, Dimitry V. Pozdnyakov, of Inland and Coastal Waters, 2018
Robert P. Bukata, John H. Jerome, Kirill Ya. Kondratyev, Dimitry V. Pozdnyakov
Light that originates from a point source (the fixed stars would qualify as such point sources when viewed from a great distance) is observed to propagate radially outward in all directions. Radiant intensity, I, is a measure of the radiant flux Φ per unit solid angle in a particular direction. Imagine a sphere of radius r with the point source of light at its center. Further imagine an infinitesimal cone, its apex at the point source, extending from the center to intersect the surface of the sphere. This infinitesimal cone subtends an infinitesimal solid angle dΩ (in steradians, sr). The intersection of the cone with the spherical surface defines a surface area dA. The radiant intensity, I, of light emanating from the point source of light as contained by and measured within the direction defined by the infinitesimal cone is then given by:
Evolution of arbitrary moments of radiant intensity distribution for partially coherent general beams in atmospheric turbulence
Published in Journal of Modern Optics, 2018
It is well known that the intensity moments in space-domain and spatial frequency-domain can be used for characterizing partially coherent beams, and average intensity distribution of the beams can be completely determined by all of intensity moments (1–6). The intensity in spatial frequency domain, which is proportion to the radiant intensity of the field, remains invariant during the free space propagation (2–4,6), implying that the moments of radiant intensity distribution (RID) have nothing to do with the diffraction in free space. In many of practical applications (e.g. lidar and free-space optical communications), some important beam parameters such as the beam direction angle, the angular spread and the quantities related to receiver optics systems (e.g. the spot size, skewness and kurtosis parameter at the focal plane of converging lens), can be derived from moments of RID (1–4,6). The kurtosis parameter in space-domain, which describes the degree of flatness (or sharpness) of intensity distribution for beams, have been extensively studied (7–14), however, for our best knowledge, the kurtosis parameter of RID has not been investigated.
Theoretical basics of radiant heat transfer – practical examples of calculation for the infrared (IR) used in infrared thermography measurements
Published in Quantitative InfraRed Thermography Journal, 2021
In this chapter, no strict differentiation is made between radiant exitance (emittance) and radiant intensity. The author, as an electrician, came closer to the term radiant intensity, which meant that it was used throughout the chapter also in the sense of radiant exitance (emittance).