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The Biological Bases of Photoreception in the Process of Image Vision
Published in Agnieszka Wolska, Dariusz Sawicki, Małgorzata Tafil-Klawe, Visual and Non-Visual Effects of Light, 2020
Agnieszka Wolska, Dariusz Sawicki, Małgorzata Tafil-Klawe
In low light levels (luminance <0.001 cd/m2), below the cone threshold, vision is scotopic: visual response relies entirely on rod signals (luminance is a photometric measure of the luminous intensity per unit area of light traveling in a given direction). Scotopic vision is characterized by poor visual acuity and lack of color discrimination. In high light levels (luminance ≥3 cd/m2), above rod saturation, vision is photopic: visual response relies entirely on cones. Photopic vision is characterized by good visual acuity and color discrimination. In the intermediate light levels (luminance between 0.001 and 3 cd/m2) between cone threshold and rod saturation, both rods and cones contribute to visual response. This kind of vision, when both rods and cones provide signals to the retinal ganglion cells, is defined as mesopic vision.
Bat Algorithm
Published in A Vasuki, Nature-Inspired Optimization Algorithms, 2020
Microbats have small eyes with mesopic vision that allow detection at low light levels. Mesopic vision is a combination of photopic and scotopic vision. Megabats have good eyesight with photopic vision that can also detect color in good lighting conditions and is as good as humans’. Microbats have large ears with a tragus that is important for echolocation, whereas megabats have comparatively smaller ears with no tragus. Bats are sensitive to earth’s magnetic field and avoid flying in the sun to prevent overheating. They mostly roost during the hottest part of the day. Some bats are solitary, but most of them live in colonies of hundreds of thousands. The bat optimization algorithm has been developed based on the study of the echolocation characteristics and behavior of bats in nature that is described in the following sections.
Lighting and Communications: Devices and Systems
Published in Zabih Ghassemlooy, Luis Nero Alves, Stanislav Zvánovec, Mohammad-Ali Khalighi, Visible Light Communications, 2017
Luis Nero Alves, Luis Rodrigues, José Luis Cura
Scotopic vision takes place under low light conditions, when only the rod cells inside the retina are active. Their spectral sensitivity is similar in form to the V(λ) curve, for photopic vision. In 1951, the CIE adopted the standard scotopic luminosity function, also available in either tabulated or graphical forms. Scotopic vision sensitivity is expressed by the V′(λ) curve; Figure 2.4 depicts both the curves for comparison. It is readily apparent that the major difference is the peak wavelengths. There is also mesopic vision, which relates to intermediate lighting situations. Under these conditions, both the rod and cone cells inside the retina are active. The sensitivity exhibits intermediate values between V(λ) and V′(λ). Mesopic vision is important for traffic lighting systems, where the road surface luminance stays above the scotopic limit and falls below the photopic limit. Current trends in outdoor lighting are considering mesopic vision for light optimization, due to the fact that photopic vision is a poor predictor of how well humans see at night. The mesopic sensitivity curve is commonly expressed as a linear combination of V(λ) and V′(λ), which is given as:
Calculation of Mesopic Luminance Using per Pixel S/P Ratios Measured with Digital Imaging
Published in LEUKOS, 2019
Mikko Maksimainen, Matti Kurkela, Pramod Bhusal, Hannu Hyyppä
The human retina consists of cone cells used for accurate day and color vision and rod cells applied for dark vision. Day vision is also called “photopic vision,” and dark vision is called “scotopic vision.” The sensitivity peaks for photopic and scotopic visions are 555 nm and 507 nm, respectively (CIE 1990; Crawford 1949). Thus, scotopic vision is more sensitive to shorter wavelength (bluish) light, and photopic vision is more sensitive to longer wavelength (reddish) light. However, in the luminance range of 0.005–5.0 cd/m2, partly scotopic and partly photopic vision applies (CIE 2010). This region is known as the “mesopic region,” and the vision for this region is mesopic vision. In the CIE 191 system for mesopic photometry, the mesopic sensitivity curve is calculated as follows:
Quantification of Trichromatic Light Sources to Achieve Tunable Photopic and Mesopic Luminous Efficacy of Radiation
Published in LEUKOS, 2019
Qi Yao, Lintao Zhang, Qi Dai, Jim Uttley
There are three vision states for human beings, which are determined by luminance levels (Stockman and Sharpe 2006): scotopic vision (<0.005 cd/m2), mesopic vision (>0.005 cd/m2, <5 cd/m2), and photopic vision (>5 cd/m2; CIE 2010). The spectral sensitivity curves V(λ) and V'(λ) that peak at 555 and 507 nm for photopic vision (Guild 1932) and scotopic vision (Crawford 1949), respectively, are the two standard functions established by CIE to describe sensitivities of these two vision states (Hsia and Graham 1952; Sagawa and Takeichi 1986; Stockman and Sharpe 2000). The spectral sensitivity curve Vmes(λ) in mesopic vision is a linear combination of V(λ) and V'(λ) (Stockman and Sharpe 2006) and varies at different mesopic luminance states. Luminous efficacy of radiation (LER), in lumens per watt, is an important parameter to measure the efficiency of light sources in different vision states. In this work, to differentiate LER in photopic, scotopic, and mesopic vision, we denote them as photopic luminous efficacy of radiation (PLER), scotopic luminous efficacy of radiation (SLER), and mesopic luminous efficacy of radiation (MLER), respectively. Due to the complexity of Vmes(λ), the scotopic/photopic (S/P) ratio (CIE 2010), which is defined as the ratio of LER in scotopic and photopic vision, is proposed to evaluate light source performance in mesopic vision.
Optimizing Lighting of Rural Roads and Protected Areas with White Light: A Compromise among Light Pollution, Energy Savings, and Visibility
Published in LEUKOS, 2020
Antonio Peña-García, Adam Sędziwy
When dealing with urban and road lighting, the use of the photopic spectral sensitivity V() to measure luminance and illuminance has led to confusion and wrong estimations (i.e., overestimation of installed power required) because the ranges of luminance involved belong neither to the photopic nor scotopic region but to the wide region called “mesopic.” In mesopic vision, both cones and rods participate in one proportion depending on the concrete luminance levels (CIE 2010b). These errors are even higher in zones where luminance levels are restricted due to environmental constraints (e.g., in national parks).