A Linearity measurement of array spectroradiometer is of great importance in the fields of photometry, radiometry, and thermometry. An accurate linearity measurement system with the flux addition method has been developed to evaluate linearity characteristics of array spectroradiometer. A nonlinear behavior of 4 % for an array spectroradiometer in the visible light was measured with reproducibility of less than 0.2 %. This result enables us to correct the nonlinear behavior of the array spectroradiometer and contributes to highly accurate optical measurements.

To examine the quantitative relationship between the degree of discomfort glare and a number of photometric quantities, experiments were conducted using red LED lamps for automotive lighting devices. Illuminance at the observer’s eye and effective glare luminance proposed by Tashiro et al. were employed as photometric quantities. The results show that the illuminance at the observer’s eye denotes the same tendency as the results of previous study. However, the results of effective glare luminance show different trends. Using a discomfort glare evaluation formula with effective glare luminance, the results of this study and Tashiro’s study were compared. The results showed a strong correlation between the evaluation and estimation values of discomfort glare. This means that the discomfort glare rating for any LED sources can be satisfactorily estimated.

LED lighting sources have become widely used in various illumination settings. The purpose of our study is to clarify the effect of luminance level of LED light sources on the visibility of a moving ball. The light was falling on the observers’ fovea and 5 luminance levels from 1^＊10⁴ to 30^＊10⁴ cd/m² were prepared. The ball size was 0.16 or 0.25 deg in visual angle. Observers pursued a falling ball in front of the light source, then responded by a two-alternative forced choice (2 AFC) method whether they could detect the ball or not. In addition, observers responded whether they could see the falling ball in whole or partially on the light source, and the apparent size of the ball if observers could detect a ball. The results showed that the probabilities of disappearance increase with luminance levels, and that the probability of disappearance for smaller balls is higher. Balls more frequently appeared partially and smaller with increasing luminance levels. We derived psychometric equations for the probability of the ball-disappearance phenomena as a function of luminance of light source, suggesting that the luminance threshold is around 30^＊10⁴ cd/m².

The nonlinearities of two silicon photodiodes (Si PDs) in visible and infrared light were experimentally measured in an optical power range from nanowatts to milliwatts. Spectral supralinearities for a Si PD were clearly observed in visible and infrared visible light. This resulted from a decrease in the recombination loss of the generated photocurrent ratio in the silicon-bulk region or the interface between the Si bulk and the silicon dioxide. These experimentally measured results are adequate for correcting the responsivity of Si PDs in a wide optical power range and predicting the spectral supralinear behaviours.