Review Paper: The Helmholtz‐Kohlrausch effect

Abstract

Abstract— The Helmholtz‐Kohlrausch (H‐K) effect is the influence of color purity on the perceived brightness of a color object (or source). In addition to a review of the effect, a survey of color and brightness‐perception studies from 1825 to the present (including our own studies on disabling glare) is presented. Disabling glare is the blinding experience which results from a bright source in our field of view. There has been a great deal of work on the H‐K effect, and this paper is our personal view of the subject. The H‐K effect has lead to new color‐appearance models which help to describe the brightness/luminance discrepancies, and we will only touch on this subject. It will be shown how the H‐K effect affects many of the displays, mobile devices, and phones. Additionally, how the H‐K effect is involved with our perception at mesopic light levels encountered during night driving will be discussed.

High efficiency and ultra-wide color gamut quantum dot LEDs for next generation displays

“…By effectively tuning the composition and size of the dots, a wide color gamut can be achieved, which creates a better viewing experience for the user of a device with QLEDs versus a device with a broadband emission source. Additionally, a narrow emission spectrum creates a perceived enhancement in brightness relative to a broad emission source according to the Helmholtz–Kohlrausch effect . Thus, light sources like QLEDs can be driven at lower luminance and achieve the same perceived brightness as a broader emission source; this allows for longer operational lifetime as well as improved color quality in a real display.…”

“…Additionally, a narrow emission spectrum creates a perceived enhancement in brightness relative to a broad emission source according to the Helmholtz-Kohlrausch effect. 10 Thus, light sources like QLEDs can be driven at lower luminance and achieve the same perceived brightness as a broader emission source; this allows for longer operational lifetime as well as improved color quality in a real display. The color tunability and purity of our QLEDs are exceptional.…”

Projection displays: New technologies, challenges, and applications

“…Projectors based on light sources with a small spectral bandwidth, for example, red, green, and blue LEDs (FWHM ≈ 18–27 nm) and lasers (FWHM < 2 nm), can have more saturated primary colors compared with projectors based on broadband light sources. This has implications on the perceived brightness, because the perceived brightness of a stimulus depends not only on its luminance but also on its chrominance, this is known for many years as the Helmholtz–Kohlrausch effect . The impact of this effect is sometimes misinterpreted in the display industry and, in some cases, wrongly promoted as a free white luminance boost.…”

Review Paper: Diffractive backlight technologies for mobile applications

“…Commonly, in LGP design, the desired state is to direct the outcoupled light toward the normal of the surface (θ m = 90°) in order to obtain the best efficiency of the display system and also the best user experience. The first approximation to start the design is to only use the classical grating equation, (4) and to limit the diffracted orders to m = 1 and m = -1. The remaining design question is to select the optimum wavelength, which obviously is in the visible range (400 < λ < 700 nm).…”

“…There is room for improvement, especially in reflective mobile designs, to be acceptable to the general public. 2 In another study it was found that test subjects preferred higher color gamuts to increased luminance in images rendered on mobile displays 3 (in general, light sources and displays with higher chroma, i.e., colorfulness, appear brighter due to the Helmholtz-Kohlrausch effect 4 ). These results clearly indicate that the image-quality issues in mobile devices are important to consumers.…”