Abstract
Given that light is known to function as a zeitgeber, having the greatest influence on the human circadian rhythm, it is necessary to assess the effects of light on humans with the goal of maintaining the circadian rhythm. Herein, we fabricated a simple circadian light meter that directly measures the non-visual effects of light using optical filters that mimic the non-visual action spectrum. The fabricated light meter was calibrated and verified through the values obtained from a conventional illuminance spectrophotometer. Furthermore, during 24 h of everyday life, 11 participants wore hats equipped with the developed light meter so that we could investigate the effects of the light environment to which they were exposed to, both indoors and outdoors. For comparison, natural outdoor illumination was also measured with the same light meter. Based on the considerable difference between the light exposure levels during the daytime and nighttime, it is possible that the participant’s melatonin levels would be impacted by the light exposure measured by the light meter. Consequently, based on the light exposure measurements made in this study, the proposed circadian light meter would be a valuable tool for real world circadian lighting studies that require actual light dose to the eyes of the test subjects.
Highlights
It can be considered that the wavelength range of sunlight detectable by the human eye has been evolutionarily adapted to distinguish objects from backgrounds, the see sights, to perceive the colors of objects, and intentionally or unintentionally to recognize day and night, thereby allowing humans to survive on Earth
We developed a facile circadian light meter by combining an optical filter, a photodiode sensor, and an analysis circuit similar to the previously developed hardware
A high transmittance level (>84%) of the action spectra was observed at the peak wavelengths
Summary
It can be considered that the wavelength range of sunlight detectable by the human eye has been evolutionarily adapted to distinguish objects from backgrounds, the see sights, to perceive the colors of objects, and intentionally or unintentionally to recognize day and night, thereby allowing humans to survive on Earth. Because human sight has evolved to operate under sunlight, people have attempted to generate light for many millennia to maintain conscious awareness of their surroundings in a dark environment [1,2]. To improve the energy performance and for greater convenience in everyday life, white light-emitting diodes (LEDs) were recently developed as efficient, stable, long-life solid-state lamps [3,4]. It is necessary to check and track whether the circadian rhythm is disturbed or is likely to be disturbed
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