The frequency of a flickering light of 0.1–7 Hz is known to induce greater pupil constriction compared to a non-flickering light. The pupillary light reflex (PLR) is mediated not only by rod and cone photoreceptors but also by intrinsically photosensitive retinal ganglion cells (ipRGCs). However, to the best of our knowledge, the PLR has not been studied under light conditions with a high frequency of >7 Hz and with a color other than blue light. In this study, 26 women aged 20–22 years were subjected to the 5-min dark/5-min light protocol (5 min of dark adaptation followed by 5 min of light stimulation). The PLR was measured as the mean pupil diameter during the last minute of light stimulation. The light stimulus conditions were non-flickering or flickering at 7, 100, and 500 Hz. The duty cycle was 10%. Although no significant difference was noted in the PLR between the red 100-Hz flickering light and the red non-flickering light, the blue 100-Hz flickering light induced a greater PLR when compared to the blue non-flickering light. These results imply that ipRGCs can recover their sensitivity to light during the dark period in a flickering light of up to a frequency of 100 Hz.

A white light-emitting diode (LED) element was fabricated with a zeolite-based inorganic phosphor without any rare earth element. This single-chip LED featured a 385 nm LED coated with the white phosphor made from pyrolyzed zeolite. A regulated power source created the LED emission of white light with the color temperature of 12000 K. The LED maintained brightness above 90% compared to the initial one even after 100 h operation. Although its luminance was lower than commercially available LED, the phosphor is easier and less expensive to produce. This makes it a potential replacement for current white LED with prospects for further improvement in zeolite phosphor and LED constructional design.

Despite advancements in miniaturizing spectrometers, inexpensive miniature spectrometers are not yet commercially available. Nevertheless, high-quality lighting systems that generate a programmable spectrum by combining several spectrally different channels require inexpensive spectrometers to control the spectrum. Inexpensive color sensors offer a solution to this but lack the necessary spectral resolution. Fusing data from multiple inexpensive color sensors can significantly enhance spectral resolution, potentially making them a cost-effective alternative to miniature spectrometers. In this article, a method for reconstructing spectra is evaluated by using commercially available spectral sensors.