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Blackbody Radiation and Light
Published in Juan Bisquert, The Physics of Solar Cells, 2017
In geometrical optics étendue is a convenient concept to describe the propagation of light through an optical system. Consider a beam of radiation in a direction s in a medium of refractive index nr shown in Figure 1.3b. dA is a cross-sectional element of the beam, and n is the normal to dA. The étendue ε is the product of the solid angle of the radiation and the projected area (Markvart, 2008). dε=nr2cosθdAdΩ
Fundamentals of Optical Concentration
Published in Roberto Ramirez-Iniguez, Sevia M. Idrus, Ziran Sun, Optical Wireless Communications, 2008
Roberto Ramirez-Iniguez, Sevia M. Idrus, Ziran Sun
When applied to an optical source, the étendue is defined as the product of the source’s area and the solid angle subtended by the optical system as seen from the source of light; and when applied to an optical concentrator, it is defined as the product of the angle subtended by an object at infinity and the diameter of a lens. This is illustrated in Figure 4.5, where a set of rays coming from an object of a specific size at a great distance is shown impinging on a thin converging lens (a lens whose thickness can be considered negligible). The lens brings each one of the rays from the object to a separate focal point forming an image of size 2fθ, where f is the focal length, 2θ is the angular extent and 2r is the diameter of the optical system. This leads to the product shown in Equation (4.9) — the étendue in a two-dimensional (2D) system-, where the factor 4 has been removed [84]. () étendue2D=θ r
Blackbody Radiation and Light
Published in Juan Bisquert, The Physics of Solar Energy Conversion, 2020
In geometrical optics étendue is a convenient concept to describe the propagation of light through an optical system. Consider a beam of radiation in a direction s in a medium of refractive index nr shown in Figure 17.3b. dA is a cross-sectional element of the beam, and n is the normal to dA. The étendue ε is the product of the solid angle of the radiation and the projected area (Markvart, 2008). dε=nr2cosθdAdΩ
Progress of display performances: AR, VR, QLED, OLED, and TFT
Published in Journal of Information Display, 2019
Ho Jin Jang, Jun Yeob Lee, Jeonghun Kwak, Dukho Lee, Jae-Hyeung Park, Byoungho Lee, Yong Young Noh
The eye box is a spatial range where an eye can be located while seeing the entire FOV of a NED. Although a large eye box is desirable for a comfortable viewing experience, the eye box of the AR and VR NEDs is limited by an etendue conservation law, which defines the trade-off relation between the eye box and the FOV, as shown in Figure 1 [10]. To obtain a large eye box and the FOV simultaneously, the etendue of the optical system should be increased either by increasing the display panel size or by increasing the NA of the optics. Since recently, however, novel techniques that overcome the etendue conservation law by using exit pupil expansion or eye tracking have been actively studied [7,15,16].