Evidence for human-centric in-vehicle lighting: Part 2—Modeling illumination based on color-opponents

Abstract

Illumination preference models are usually defined in a static scenery, rating common-colored objects by a single scale or semantic differentials. Recently, it was reported that two to three illumination characteristics are necessary to define a high correlation in a bright office-like environment. However, white-light illumination preferences for vehicle-occupants in a dynamic semi- to full automated modern driving context are missing. Here we conducted a global free access online survey using VR engines to create 360° sRGB static in-vehicle sceneries. A total of 164 participants from China and Europe answered three levels in our self-hosted questionnaire by using mobile access devices. First, the absolute perceptional difference should be defined by a variation of CCT for 3,000, 4,500, and 6,000 K or combinations, and light distribution, either in a spot- or spatial way. Second, psychological light attributes should be associated with the same illumination and scenery settings. Finally, we created four driving environments with varying external levels of interest and time of the day. We identified three key results: (1) Four illumination groups could be classified by applying nMDS. (2) Combinations of mixed CCTs and spatial light distributions outperformed compared single light settings (p < 0.05), suggesting that also during daylight conditions artificial light supplements are necessary. (3) By an image transformation in the IPT and CAM16 color appearance space, comparing external and in-vehicle scenery, individual illumination working areas for each driving scenery could be identified, especially in the dimension of chroma-, partially following the Hunt-Effect, and lightness contrast, which synchronizes the internal and external brightness level. We classified our results as a starting point, which we intend to prove in a follow-up-controlled laboratory study with real object arrangements. Also, by applying novel methods to display high fidelity 360° rendered images on mobile access devices, our approach can be used in the future interdisciplinary research since high computational mobile devices with advanced equipped sensory systems are the new standard of our daily life.

Evidence for human-centric in-vehicle lighting: part 3—Illumination preferences based on subjective ratings, eye-tracking behavior, and EEG features

“…This effect was valid for the European group but missing for study participants from China. Part 2 extended these findings to the context of general white light illumination (Weirich et al, 2022b ). By displaying images as a 360° scene, we varied the correlation of color temperature (CCT), light distribution, and brightness settings, which were applied to four different driving scenes.…”

“…To evaluate whether favored or unfavored illumination settings can be decoded via brain activity, we first created adequate visual stimulation images. For that, we used a similar study setting as in our previous research (Weirich et al, 2022b ): We arbitrarily presented four driving scenes to each subject, which were located in (a) a sunny city, (b) a dim forest, (c) a sunny countryside, or (d) the night of Shanghai, separated between a favorable and unfavorable session. Since we presented the impression as a highly immersive 360° image on a 25-inch LED-Lit screen (Dell U2518DR) operated at 60 Hz, the subjects were able to rotate the camera view within the second row of the vehicle.…”

“…We used two different metrics to measure their level of emotions. First, we used the same six fields of semantic differentials rated by a 6-point scale, as described in detail in our previous study (Weirich et al, 2022b ), separated between evaluative and in-vehicle perceptions. For the evaluative domain, we set brightness, spatial, and interest, and for the in-vehicle domain, we set modernity, value, and satisfaction as perceptional dimensions.…”

“…(C, D) An example of a bad lighting setting, labeled L4 and L8. (A–D) Study results from our previous research (Weirich et al, 2022b ).…”

Multimodal in-vehicle lighting system increases daytime light exposure and alertness in truck drivers under Arctic winter conditions

“…Due to its small form factor and controllability, LED technology is widely used in interior car lighting 45 . In-cabin lighting has been primarily used in passenger cars and fulfills visual and aesthetic needs, but it is not often designed to combat safety issues.…”