Abstract
The discovery of melanopsin as a third type of retinal photoreceptor, contributing to both perceptual vision and reflex light responses, represents a new opportunity to optimise the design of artificial light sources for practical applications and to generate experimental stimuli. In the case of emissive displays, multiprimary designs incorporating a cyan primary could be used to allow melanopic radiance to be controlled independent of colour and luminance. Here we explore the performance a five-primary (violet, cyan, green, yellow, red) display device and find an anomaly in colour appearance when the cyan primary is employed. The anomaly took the form of a reddish/pinkish tinge in the central visual field, consistent with descriptions of Maxwell’s spot. This effect was apparent in some full colour images and in uniform discs over a range of chromaticities. Its appearance in coloured discs correlated with differences in calculated colour coordinate between central and peripheral vision. A simulation indicated that inclusion of any primary with predominant output in the 470–500 nm range has the potential to produce such a discrepancy in central vs peripheral appearance. Applying an additional constraint in colour processing to reproduce naturally occurring differences in central vs peripheral colour coordinate eliminated appearance of the spot and produced acceptable colour images.
Highlights
Multi-primary displays that render images in more than the standard 3 distinct colour emitting elements can offer advantages in terms of energy efficiency and colour gamut (Teragawa, 2012)
We find that a uniform colour appearance can be achieved by changing the colour mapping used to render images, including a parameter that accounts for differences in colour coordinate between central and peripheral vision
We report here the appearance of a colour anomaly when rendering colours using a multiprimary display that includes a cyan primary
Summary
Multi-primary displays that render images in more than the standard 3 distinct colour emitting elements (red, green, blue; RGB) can offer advantages in terms of energy efficiency and colour gamut (Teragawa, 2012). They can provide an opportunity to control the activity of the inner retinal photoreceptor melanopsin. Melanopsin renders certain retinal ganglion cells photosensitive (Provencio, 2000; Berson, Dunn, & Takao, 2002; Lucas, 2003) These photosensitive retinal ganglion cells have been appreciated as the main input into the circadian clock, providing a signal of ambient irradiance that synchronises the clock’s phase with the solar day (Berson et al, 2002; Do & Yau, 2010; Schmidt, 2011). Melanopsin has been shown to have a behavioural significance in brightness discrimination and pattern detection (Allen, Martial, & Lucas, 2019; Brown, 2012; Spitschan, 2017; Yamakawa, Tsujimura, & Okajima, 2019; Zele et al, 2018b)
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