We evaluated the spectroscopic performance of an otoscope during otoscopic examinations using a headlight with an LED source. We used the mechanisms and the specifications of the objects measured with the otoscope and so on to evaluate the spectroscopic performance. Experimental equipment was built using the existing otoscope and headlight, and we demonstrated methods of measuring the spectral irradiance of the otoscope. We demonstrated methods of evaluating the spectroscopic performance using the spectral irradiance ratio and chromaticity by the measured spectral irradiance. We measured the spectral irradiance of the otoscope using the measuring methods. We found that the spectral irradiance distribution in the otoscope is greatly affected by the spectral distribution in the headlight source. We evaluated the spectroscopic performance of the otoscope using the evaluation methods. The spectroscopic performances of the reflected light onto the surface of, and the direct and reflected lights in, the otoscope differ and are affected by differences in shape, surface condition, length, and the diameter of the wide mouth. The spectroscopic performance of the direct and reflected lights in the otoscope is affected by differences in the diameter of a narrow mouth and the distance and angle between the otoscope and the headlight.
We used a categorical ratio evaluation method to conduct experiments to evaluate the appearance of colors in mesopic vision under light sources with different spectral distributions. The experimental results showed that the appearance of color changed as the illuminance decreased. Also, the appearance of color was slightly different depending on the light source. Analysis of the results showed that transforming the opponent color response function can better explain the appearance of color in mesopic vision.
High-power LED floodlights for sports stadiums such as baseball and soccer stadiums have become increasingly popular and have already been installed in many facilities. LED floodlights consist of many LED chips that each have a small and high luminance light-emitting surface. Therefore, when a ball overlaps with the lighting fixture in a player’s visual field, a temporal vision loss due to the afterimage of an intense light-emitting surface, i.e., disability glare, occurs together with an excessive discomfort glare.
In this study, we investigated the effect of direct viewing glare due to LED floodlights on a player’s performance by measuring the reaction time for catching moving stimuli presented with a glare stimulus, a high-intensity LED light source. Three different trajectories (low, middle, and high) were used as moving stimuli. The error rate greatly increased in the low-trajectory condition at the glare luminance of 1.2×106 cd/m2 but only slightly increased in the medium-trajectory condition at the same luminance. This indicates that the luminance of LED floodlights in a lighting tower should be kept below 1.2×106 cd/m2 to avoid unexpected errors due to direct viewing glare.
Blue light often causes discomfort glare, but it is unclear which visual pigments are the main contributing factors. Thus, we conducted an experiment to clarify the effects of two visual pigments, S-cones and melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs), by applying a silent substitution method for keeping the stimulations of L and M cones intact in foveal and peripheral vision. The color temperatures of the stimuli were 2700 K and 8000 K, and the luminance value was 1000 cd/m2. The background luminance was set to 5.0 cd/m2 to create photopic conditions. Participants were exposed to the discomfort glare of the two stimuli sequentially and evaluated them using pairwise comparisons. The results showed that stimulation of ipRGCs significantly increases the discomfort glare in peripheral vision whereas the stimulation of S-cones does not, indicating that ipRGCs play a crucial role in the occurrence of discomfort glare caused by blue light.
High-brightness digital signage have begun to be installed for outdoor advertisements in Japan. The CIE150 standard sets a maximum luminance value of 1000 cd/m2, but it is hardly regulated by outdoor advertising in Japan. In this survey, we first investigated the brightness functions of digital signage and found that most did not have a dimming function for adjusting to the brightness of the environment. In addition, we measured the luminance and size of outdoor advertisements and vertical illuminance in the Shibuya, Ginza, and Shinjuku neighborhoods of Tokyo. Many of the signs exceeded 1000 cd/m2, so there is an urgent need for regulation. We hope that the results of this research will serve as the starting point for brightness regulation in Japan.
Driver assistance projection technology, in which specific symbols are projected onto the road ahead of a vehicle using an adaptive driving beam (ADB), has been developed to assist drivers in driving safety; However, depending on how the projection used, it may distract the driver in the host vehicle as well as others on the road such as other drivers, pedestrians and cyclists. Thus, we conducted an experiment to validate the safety and readability of the projections. The effect of symbol projection on safe driving was investigated by measuring the drivers' response time in response to the brake lights of the vehicle in front. We also evaluated the readability of the symbols for the host vehicle drivers and other road users. Under the conditions of this experiment, when a symbol was projected onto the road, their response time was 0.1 to 0.2 s slower than when it was not projected. We also verified that the response time was longer when the symbol was difficult to read such as lamp low luminous intensity and far projected and that symbols projected with high luminous intensity near the vehicle were more noticeable for both host vehicle drivers and pedestrians. The results show that the luminous intensity, projected position, and size of the symbols need to be adjusted accordingly such that they can be easily read by the driver of the host vehicle without interfering with other road users.
Discrete spectrum light sources are expected to become the next generation’s light sources. In this study, we investigated the brightness and appearance of RGB laser illumination, its brightness was 7% higher, and its color appearance was tinged yellowish-green compared with the conventional white LED illumination. In this paper, we verified both the brightness and appearance of color for RGB LED illumination which had a wider half width than that of RGB laser. The results showed that the brightness of RGB LED illumination was 10% higher, and the color appearance was tinged yellowish-green compared with a conventional white LED lamp at the same chromaticity coordinates.
We developed a simulation model to analyze the characteristics of low-pressure mercury-argon torus plasma generated in an inductive fluorescent lamp. This model is based on the classic models developed by Waymouth, Bitter and Cayless, and the characteristics of the torus plasma with non-circular cross-section can be evaluated by applying the concept of “equivalent tube” and “equivalent discharge”. We included the elastic collision of electrons with mercury atoms to take into account the low filling gas pressure of argon, i.e., ～20 Pa. The accommodation coefficients, which were originally introduced by Waymouth to fit the calculated results with experimental data, were reexamined, i.e., the ionization cross-section from 63P levels and the effective imprisonment time of the resonance radiation. The calculated plasma parameters, electrical characteristics, luminous flux and efficacy showed good agreement with the experimental data. This agreement mainly attributes to the accommodation coefficients we selected, and the physical interpretation of these coefficients was suggested. We applied the model to investigate the possibility of further improvement in the luminous efficacy by changing the shape of the discharge vessel, mercury vapor pressure, and argon gas pressure. The results indicate that the luminous efficacy is expected to increase up to about 7% with a larger vessel diameter, lower mercury vapor pressure, and lower argon gas pressure. Our model is expected to be useful in designing the driving circuit as well as addressing the thermal issue of an inductive fluorescent lamp.