Communication window lighting (CWL) had been proposed as a system to provide information from the external world into a closed space. In this system, the brightness and color of the external world are reproduced on windows to provide information such as time, direction, and weather. In our experiment, subjects estimated the perceived time, direction, and weather using the CWL. We examined the effectiveness of brightness and color information. We found that brightness reproduction mainly contribute to providing time information and color reproduction effectively provide the weather information.

View full abstract

In this study, comparative experiments were conducted on the apparent brightness of visual targets illuminated by three types of headlight sources (halogen, HID, and LED), and the results were analyzed in terms of characteristics of visual perception. Those visual targets (with visual size of about 1 degree) were used on an actual road surface and a grey cotton cloth. To compare the apparent brightness under different light sources, we used the matching stimuli presented on the CRT display as a reference. The subjects adjusted the gradation of the matching stimuli until they perceived the brightness of the matching stimuli and that of the sample as equal. Under different light sources, luminance was set to 13 cd/m² for the road surface sample and 9.6 cd/m² for the grey cotton cloth. Atotal of 40 subjects aged between 25 and 65, including three women, participated in the experiment. Their average age was 48, and four of them wore glasses. The results indicate that the apparent brightness of road surface differed among the light sources even at the same level of luminance. This demonstrates that the LED light source had higher brightness efficiency than the HID and halogen light sources (meaning that the same brightness can be obtained from the LED light source moreover at a lower level of luminance). Furthermore, such perception changed with observer age, the results for the grey cotton cloth were similar mostly. Instead of the spectral luminous efficiency, V(λ), used for the present photometric system, a new spectral sensitivity, Vk(λ), which takes account of the spectral sensitivity of the short-wave sensitive cones associated with photopic vision, was used for the analysis, and it could accurately explain the experimental results. This suggests that the apparent brightness of white light can be quantitatively compared and evaluated based on the practical effect of luminance of brightness calculated using the spectral sensitivity that takes into consideration the contribution of the short-wave sensitive cones.

View full abstract

The estimation of optimal print size for reading is often essential in clinical treatment and/or universal design; however, it is not known how to calculate the proper letter size for reading with maximum efficiency. Psychophysics studies have revealed psychometric functions of reading that exhibit a hill-like shape with a plateau of maximum speed and a downfall beyond Critical Print Size (CPS). To control the magnification rate of visual aids for patients with visual impairments, CPS that can indicate the boundary of maximum efficiency is now becoming a noteworthy index to determine optimal letter size. In addition to reading, word searching is also an important task for our living. However, the CPS of word search tasks has not been examined yet. We estimated the CPS of word search from the results of two experiments focused on searching for words in Chinese characters and Japanese alphabet (Katakana: square forms) in Japanese. The functions of the searching tasks showed a hill-like shape almost identical to the reading tasks but with elevated speed, and the CPS were stable around 0 logMAR in both the reading and the searching tasks. Hence, CPS is unsusceptible to tasks and can function as a robust marker for the smallest print size with maximum speed. This finding indicates that CPS is the threshold of proficiency (maximum/reduced) beyond the threshold of vision (visible/invisible). CPS can be a meaningful index to achieve the appropriate control of print size and subsequently help people with visual problems.

View full abstract