Detection of the stroboscopic effect by young adults varying in sensitivity

The advent of LED lighting has renewed concern about the possible visual, neurobiological, and performance and cognition effects of cyclic variations in lighting system luminous flux (temporal light modulation). The stroboscopic visibility measure (SVM) characterises the temporal light modulation signal to predict the visibility of the stroboscopic effect, one of the visual perception effects of temporal light modulation. A SVM of 1 means that the average person would detect the phenomenon 50% of the time. There is little published data describing the population sensitivity to the stroboscopic effect in relation to the SVM, and none focusing on people subject to visual stress. This experiment, conducted in parallel in Canada and France, examined stroboscopic detection for horizontal and vertical moving targets when viewed under commercially available lamps varying in SVM conditions (SVM: ∼0; ∼0.4; ∼0.9; ∼1.4; ∼3.0). As expected, stroboscopic detection scores increased with increasing SVM. For the horizontal task, average scores were lower than the expected 4/8 at ∼0.90, but increased non-linearly with higher SVMs. Stroboscopic detection scores did not differ between people low and high in pattern glare sensitivity, but people in the high-pattern glare sensitivity group reported greater annoyance in the SVM ∼1.4 and ∼3.0 conditions

A fiber optic array spectrometer with parallel multichannel optical lock-in detection and its application to in situ lighting measurements

Lock-in detection is a well-established technique to measure a modulated electrical signal in the presence of noise and large background signals. Commercially available lock-in amplifiers are not adapted to detector arrays such as used in modern compact optical spectrometers. In this case, performing lock-in detection requires a parallel multichannel processing of all spectral channels simultaneously. This paper describes an optical lock-in spectrometer featuring parallel and multichannel lock-in detection. It is based on two compact array spectrometers working in phase quadrature thanks to a wideband optical modulator assembled using standard optical components. In the application example, irradiance and illuminance lock-in measurements were performed on commercial LED lamps exhibiting temporal light modulation at different frequencies. A remote sensing optical device was designed to measure from a distance the temporal luminous waveform of a specific LED lamp and send it to the reference input of the optical lock-in spectrometer. When these lamps were operating together on top of a large continuous luminous background up to 30 times more intense, the optical lock-in spectrometer successfully retrieved the respective spectral irradiance distributions and color parameters of each lamp, allowing their characterization to be performed independently of the other light sources illuminating the sensor during the measurements.</p