We conducted subjective experiments to determine an ideal method for achieving both energy saving and comfort in office lighting. The experiments were conducted in an actual office under 48 conditions of lighting and furniture, such as different average illuminance, lighted areas, reflectance, and height of partitions, and added wall-washers. Luminance images were captured from the subject's viewpoint, and converted into brightness images based on the Nakamura method. We then analyzed the relationship between the perceived brightness and the brightness images. In the results, the subjective evaluation value of the brightness of the room strongly correlated with the average values of the brightness scale of vertical components, such as a wall or partition, calculated from the brightness images. This suggests that we can reduce the electricity consumption of lighting and achieve higher perceived brightness without losing comfort by raising the brightness of the vertical components in the field of view.
This study aims to determine the appropriate lighting conditions for applying makeup. We presumed that applying makeup includes two tasks : ‘base makeup’, i.e., foundation and cheek rouge ; and ‘point makeup’, i.e., mascara and lip rouge. The brightness or visibility of one's face, and the task performance of applying makeup in different lighting conditions is reported. We conducted a subjective experiment on the lighting condition of a washstand in a bathroom. The washstand used in the experiment was equipped with four fluorescent lamps or two incandescent lamps, enabling varying conditions of illuminance on the face, light color, and lighting of the mirror to be presented. Twenty subjects observed their faces under 32 lighting conditions, and they evaluated the “brightness of one's face”, “visibility of features of one's face”, “visibility of shadows”, “glare of lighting”, “discomfort of glare”, “annoyance of shadow”, “task performance”, and “satisfaction” after applying both base makeup and point makeup. In the evaluation results, “task performance” and “satisfaction” in base makeup were clearly higher when the illuminance on the face was high. “Task performance” and “satisfaction” in point makeup were also clearly higher when the mirror was lit from all four sides or from vertical sides by fluorescent lamps than when the lighting was from above and below.
We investigated the discharge characteristics in a cold cathode lamp of 4 mm inner diameter used for backlighting liquid crystal displays. The electrode on one side of the lamp was made of nickel, and that on other side was platinum. The Ne gas pressure filling the lamp was 53 hPa. The cathode voltages of a lamp with the electrodes made of different materials were simultaneously measured with a high voltage probe connected to a digital oscilloscope when the lamp was operated by a sine wave power supply under the same discharge condition. The breakdown and maintained voltages in the case of the nickel electrode were lower than those of the platinum electrode. The measured reignition voltages were almost constant breakdown voltages in the frequency region of 0.1 to 100 Hz. In frequencies above 100 Hz, the reignition voltages decreased sharply, a becoming close to the maintained voltages. The accurate breakdown voltage was estimated to be less than a 100 Hz sine wave.
The electric characteristics of a magnetic-coupling-type electrodeless discharge lamp are investigated. The discharge tube of the lamp is a hollow cylinder, and a magnetic path made of a ferrite core passes through the tube. A high-frequency power voltage is applied across an excitation coil wound around the core through a capacitor. The operating frequency is adjusted to the resonance frequency of the circuit. The light emission from the lamp and magnetic loss are measured as a function of the number of excitation coil turns. The resonance frequency and light output from the lamp decrease with increase of the number of coil turns, while the coil input power shows nearly constant characteristics. The light output decreases with the number of coil turns due to increment of magnetic loss. The eddy current loss in the magnetic material is independent of the operating frequency, but the hysteresis loss that comprise a large part of the magnetic loss around 150 kHz increases with decrease of the operation frequency. These results show that higher frequency is preferable for operating an inductively coupled electrodeless lamp with a magnetic core.