The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Models for Spectral Luminous Efficiency in Peripheral Vision at Mesopic and Low Photopic Luminance Levels

Pasi Orreveteläinen

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Electrical and Communications Engineering for public examination and debate in Auditorium S4 at Helsinki University of Technology (Espoo, Finland) on the 28th of October, 2005, at 12 noon.

Dissertation in PDF format (ISBN 951-22-7857-X)   [1106 KB]
Dissertation is also available in print (ISBN 951-22-7856-1)

Abstract

The aim of this work was to find out how the spectral sensitivity of the human eye varies in peripheral vision at mesopic and low photopic luminance levels. Two different measurement methods were employed for this purpose. Reaction time and contrast threshold measurements were conducted at various mesopic and low photopic luminance levels in foveal and peripheral vision. Luminance levels between 0.1 cd/m2 and 20 cd/m2 and visual target eccentricities of 0°, 10°, 30° and 60° were investigated in the measurements. Both measurement methods revealed the same observations: at low photopic luminance levels, the currently used V(λ) function is not the best descriptive spectral luminous efficiency function for peripheral vision. The short wavelengths were underestimated by the V(λ) function. A new spectral luminous efficiency function Vper(λ) was developed for peripheral vision at photopic light levels. This function is a linear combination of V(λ) and V10(λ) functions and takes into account the higher spectral sensitivity to short wavelengths as compared to the V(λ) function. Both measurement methods show that this function describes the spectral sensitivity of the eye better than V(λ), VM(λ) or V10(λ) functions at low photopic luminance levels (≤ 20 cd/m2). At mesopic luminance levels (≥ 0.1 cd/m2), it was investigated how a linear combination of photopic and scotopic spectral luminous efficiency functions describes the spectral sensitivity of the eye in peripheral vision. A model for the mesopic spectral luminous efficiency function Vmes(λ) was developed for peripheral vision. The results showed that this function describes the peripheral spectral sensitivity with best accuracy at mesopic luminance levels. The new function was compared with the proposed unified system of photometry by Rea, Bullough, Freyssinier-Nova and Bierman (2004). The function developed in this work described the measurement results with much higher accuracy. A sigmoid function was developed to describe the mesopic spectral luminous efficiency function as a combination of photopic and scotopic spectral luminous efficiency functions. This function can be used to calculate the weighting coefficient from 0.1 cd/m2 upwards.

Keywords: peripheral vision, mesopic vision, reaction time, contrast threshold, spectral luminous efficiency function

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© 2005 Helsinki University of Technology

Last update 2011-05-26