Research On Temporal Light Mechanism And Modulation Technology Of Low-Level Lighting

In recent years,urban expressways,viaducts,sea-crossing and river-crossing bridges have developed rapidly.As the main form of lighting,the traditional high-pole lighting is gradually replaced by low-level lighting because of its heavy foundation,weak resistance to wind pressure,inconvenient maintenance and so on.Low-level lighting means that the installation height is less than 1.5m and is arranged along both sides of the road.At present,the existing low-level lighting mode in China directly throws the street lamp light with strong glare exposed in the driver’s vision into the middle of the road,so the bright street lamp surface forms a strong contrast with the environmental background,when the driver passes by,alternating light and dark stimuli form a temporal light,commonly known as the flicker effect,which is very easy to cause driver visual fatigue,and visual fatigue is one of the important factors leading to traffic accidents.At present,the research on the flicker effect of low street lamps at home and abroad is mainly based on the suggestion of CIE n88-2004.The recommendation indicates that the flicker effect is related to frequency,which is determined by vehicle speed and street lamp spacing,and that it is less than 2.5Hz or greater than 15 Hz.However,the proposal is incomplete: 1.The proposal makes the installation distance of street lamps have a "forbidden area",which has an impact on the actual project;2,the research shows that the flicker frequency around 20 Hz is an important factor causing epilepsy,and avoiding the 2.5Hz-15 Hz area is precisely the main stimulation area that causes seizures;3.Bloch’s law shows that human eyes perceive the flicker of the signal,the signal should meet a certain energy intensity.The flicker intensity caused by alternating light stimulation signals to human eyes is related to the energy of stimulation signals.This suggestion only pays attention to the influence of frequency on human eyes,but ignores the method of flash energy and does not fully reveal the internal mechanism of stroboscopic.In addition,the current research on flicker effect is mainly based on people’s subjective feelings and can not be quantified.First of all,in order to solve the above problems,this paper constructs the flicker index model according to the definition of flicker in IESNA.The model shows that the flicker index is related to the flicker energy ratio and duty cycle.The flicker energy ratio is the strength ratio of strong and weak signals.Duty cycle,in the time domain,refers to the proportion of strong and weak flicker signals over a period of time.In the spatial domain,it refers to the ratio between the length of the street lamp and the distance between the lights.Its essence is the duration of stimulation to the human eye,that is,the amount of energy received by the human eye.The flicker effect is determined by the flicker index,and the essence of the flicker index is the energy problem,so it is revealed that the mechanism of the low-level lighting transient light is the energy ratio.The flicker index value can be calculated by measuring the street lamp surface face brightness,environmental background brightness,street lamp luminous surface length and installation spacing,so as to evaluate the flicker effect intensity.Secondly,the temporal and spatial response characteristics of human vision are analyzed.According to this characteristic,the flicker index model is modified,and the modified model is related to the driver’s motion state and belongs to the dynamic process,so the concept of low-level lighting dynamic glare is put forward.Furthermore,by detecting the visual fatigue value of testers under different intensity signals to judge the effects of different degrees of stimulus signals on people,the experimental study shows that: the greater the intensity of stimulation signals,the more prone to fatigue.It proves that the flicker index model is correct and scientific.The experimental study on whether the background light source compensation measure is beneficial to reduce the influence of flicker effect on people by detecting the tester’s eye movement parameters shows that the smaller the energy ratio is,the smaller the blinking frequency is,and the shorter the eye closing time is.It proves that the effective measure to reduce the flicker effect is to reduce the energy ratio.Reducing the energy ratio can increase the background brightness or reduce the street lamp surface face brightness,but increasing the background brightness has no practical significance,so the key technology to reduce the energy ratio is to reduce the street lamp surface face brightness.It reveals the modulation technology of low-level lighting temporal light.Finally,the transient light mechanism of low-level lighting is similar to that of tunnel and underground passage lighting.In this paper,the revelation of the mechanism of temporary light and the research results of modulation technology are also applicable to the lighting design of tunnels and underground passages,which provides a reference basis for practical projects.