We evaluated the performance of light focus in an existing otoscope with a headlight employing an LED source. The mechanism of the otoscope was shown, and a coordinate system was set in the otoscope to evaluate the light-focusing performance. Experimental equipment based on the set coordinate system was built using the existing otoscope and headlight. We demonstrated experimental methods for measuring illuminance at the narrow mouth in the otoscope using the built experimental equipment. In the experiments conducted using the experimental methods, the performance of light focus in the existing otoscope was evaluated by measuring the illuminance. The optimal new otoscope for focusing light was designed using a headlight employing the LED source. The otoscope was built using the results obtained by the designs. We evaluated the performance of light focus in the designed otoscope with the otoscopes we built. The experimental equipment was built with the constructed otoscope and the headlight. We demonstrated experimental methods for measuring illuminance at the narrow mouth in the otoscope using the built experimental equipment. In the experiments conducted using the experimental methods, the performance of light focus in the designed otoscope was evaluated by the measured illuminance.

Conventional lighting booths with custom standard fluorescent lights are used in industry for testing and quality control of color materials. In this study, we constructed a lighting booth based on an LED spectrally tunable light source (LSTL) that implemented a simple forced air-cooling system. The LSTL was composed of a UV-LED, single color LED, and quasi-yellow LED to cover the wavelength range from 340 to 800 nm. To compensate for the lack of appropriate green LEDs in the wavelength range from 520 to 625 nm, the LSTL used the quasi-yellow LED, which was made by cutting the blue spectrum of a white LED with a long-pass optical filter. The reconstructed spectrum was more approximate CIE standard illuminant than a D65 fluorescent lamp, and the fluctuation of optical intensity was of considerable well property. In addition, we also discussed advantages of and improvements enabled with LSTL through a comparison with D65 standard fluorescent lamps.

Research into shadow quality or light quality has exchanged light diffusers or changed the arrangement of parts to change light quality. This necessity has restricted the type of psychological experiments that can be realized. In this study, electrically controllable polymer dispersed liquid crystal (PDLC) was applied for a continuously tuned diffuser. This illumination system using PDLC finely tunes light quality, which influences shadow quality. Though light quality can only be tuned by finely controlling applied voltage to the PDLC, the light quality is not proportional to the controlled applied voltage. To construct an interface based on the magnitude of shadow softness (i.e., the light quality), the magnitude estimation (ME) method was used to estimate the relationship between the magnitude of shadow softness and applied voltage to the PDLC. When the applied voltage was adjusted with equal intervals in the magnitude of shadow softness obtained by ME, the shadows resulting under the illumination system using PDLC were felt at almost equal intervals in the shadow softness. Although this proposed protocol for constructing a light-quality tunable illumination system using PDLC may be incomplete at this stage, it is expected to motivate new research into light and shadow quality.

The objective of this research was to develop a high efficiency backlight for liquid crystal displays (LCDs). A typical LCD panel includes a pair of dye polarizers. The polarizer functions by absorbing light of one component and by allowing the other component, which has a plane orthogonal to the first component, to pass through the polarizer. Therefore, the polarizer absorbs at least 50% of the light illuminated onto the LCD panel if it is unpolarized. Hence, the ratio of the light from the backlight absorbed by the polarizer need to be reduced to achieve low power consumption in the LCD. Light output at the interface of refraction is known to contain more p-polarized light than s-polarized light, and this can be attributed to the transmittance difference between the two kind of light there. We make use of interface refractions from existing optical components and maintain the state of polarization as light passes through them. In accordance with this concept, we have successfully developed a polarized backlight utilizing a p-polarized light out-coupling by effectively using the interface refractions of optical components. In our backlight, the luminance for the p-polarized light was improved by 30% or more compared to that of a conventional backlight. In addition, this backlight can be composed of fewer components. Therefore, low power consumption can be achieved by applying our backlight to LCDs, and the added benefits are that the module can be made thinner and at low cost.