In the road lighting standard, the average brightness of the road surface is often less than 2of m2, which belongs to the middle vision category. Therefore, the brightness value under bright visual conditions should not be used to evaluate the road lighting effect, especially the brightness under 2* field of view conditions. The value is directly evaluated, that is, the brightness value measured by the luminance meter cannot be directly used for direct evaluation. Under intermediate vision conditions, the luminous efficiency of the light source is not only related to the spectral distribution of the light source, but also to the level of adaptation of the human eye. Therefore, in order to make the road lighting level more in line with the actual viewing effect and meet the requirements of road lighting energy saving, it is necessary to reasonably determine the luminous efficiency of the light source at different adaptation levels of the human eye.
1 Intermediate visual time spectrum optical efficiency function 1.1 Spectral optical efficiency function measured values ​​Under the visual and dark visual conditions, the spectral optical efficiency function has been recommended by CIE in 1924 and 1951, respectively, and the optical efficiency of intermediate visual spectrum. The function Vm(A) is suggested by scholars to calculate the visual and dark visual response values. Park Dazhi and others of China Institute of Metrology, in 1986, conducted a study on the optical visual efficiency function of the intermediate visual spectrum. Using the heterochromatic brightness matching method, 26 people were measured under 9 retinal illumination levels and 10* field of view. Observer's intermediate visual spectrum light efficiency function, and proposed the spectral light efficiency function value (logarithmic unit) from 100Td (Mesh A) - the net illuminance is 0.01Td; lgV (human) a reticulated illuminance is Spectral light efficiency function value (logarithmic unit) at 10CTd.
1.2 The proportional coefficient a value can be calculated by the formula (1). The expression of the proportional coefficient is in the range of 520 nm. The arithmetic mean of the proportional coefficient a under different net illuminance is shown in Table 1.
In the 700nm band, the proportional coefficient a should be sinusoidal for curve fitting under different net illuminance. The regression equation is shown in the following table. From Table 2, the complex correlation of the regression equation is obtained when the illuminance ETD is 0.032Td. The coefficient R is relatively small, because the corresponding proportional coefficient a in the 520700 nm band varies with wavelength. The arithmetic mean of the different net illuminance a in Table 1 at 400~520 nm Table 2 The different net illuminances at S0-700 nm a The logarithm of the expression brightness L is approximately proportional: according to the definition of the illuminance of the mesh film, dividing the net illuminance E* by 10 is the field of view brightness L. Therefore, the subjective brightness and the galvanic illuminance can be obtained from the formula (13). The conclusion that the logarithmic value is approximately proportional, which indicates that the degree of visual perception of light radiation by the human eye is approximately proportional to the logarithm of the net illuminance. Spectral optical performance is used to measure the visual sensation caused by radiation. Therefore, the maximum value of the spectral optical performance when different illuminances are obtained by linear interpolation: from the above, according to different illuminance levels It is reasonable to calculate the maximum value of spectral optical performance (14), which is convenient to use in actual lighting engineering; however, it should be further verified and improved by direct brightness matching method.
3 luminous efficiency of the light source When the accessory loss of the light fixture is not considered, the luminous efficiency of the light source can be calculated according to the spectral power distribution of the light source, etc., * the luminous flux of the light source, m; the power of the light source, W; Km - the spectral light sight Maximum performance; 6831 hVW in bright vision, 1700 lnVW in dark vision, (14) in intermediate vision; 400 W standard high pressure sodium lamp and 400 W metal halide lamp (xenon lamp) as an example, calculated in human The luminous efficiency of the light source at different levels of adaptation of the eye.
The high-pressure sodium lamp radiates a large amount of energy in the sensitive wavelength region of the human eye during bright vision, so the luminous efficiency of the lamp is large, but the energy radiated in the short-wave region of visible light is small; the metal halide lamp (xenon lamp) is A dense spectral line is radiated in the visible light region, which can be considered as continuous, and the light color is similar to sunlight, and has good color rendering.
The maximum performance expression of the 400W standard high pressure sodium lamp and the 400W metal halide lamp (xenon lamp) is calculated by equation (15) at different adaptation levels of the human eye. Academic Electrnic Publish light efficiency is shown in the topsoil... In order to facilitate comparative analysis, table c4 also lists the luminous efficiencies of a 250W typical fluorescent high pressure mercury lamp (transparent bubble lamp) and a 180W S0X low pressure sodium lamp and a 1500 W sodium lamp.
Table 4 Luminous efficiency of different light sources when the human eye has different adaptation levels (lim/WQ human eye adaptation level visual dark visual metal halide 4) W é• ç¯ ç¯ ç¯ 1500W/é’ª sodium lamp 250W / typical fluorescent high pressure mercury lamp (transparent blister Lamp) 400W / standard high pressure sodium lamp 180W / SOX type low pressure sodium lamp As seen from Table 4, even at the different adaptation levels of the human eye, even the actual luminous efficiency of the same type of light source is subject to change, and when the light source emits visible light When the energy of the short-wave region is small, the luminous efficiency of the light source will become small in dark vision due to the influence of the Purkinje phenomenon. For example, the standard high-pressure sodium lamp has a luminous efficiency of only 66% in bright vision in dark vision, and the luminous efficiency at this time is 711WW; on the contrary, when the energy of the short-wave region of the visible light is large, for example, the color rendering property is good. Metal halide lamps (xenon lamps) are more than twice as bright in dark vision as bright vision, reaching 1821WW!
If the existing photometric instrument is used, that is, the luminous efficiency calculated by the spectral optical efficiency function V(A) of the visual field of the visual field 21, the relative luminous efficiency of different light sources at different adaptation levels of the human eye is as follows. Table 5 shows.
Table 5 Luminous efficiency of different light sources at different adaptation levels of human eyes Human eye adaptation level Visual dark vision metal halide lamp 1500W/é’ª sodium lamp 250W/typical fluorescent high pressure mercury lamp (transparent bulb lamp) 4(1)W standard high pressure sodium lamp 180W/SOX The low-pressure sodium lamp can be seen from Table 5. At different adaptation levels, the luminous efficiency of the light source varies with the adaptation level of the human eye, and the magnitude of the change is determined by the adaptation level of the human eye and the relative power distribution of the light source.
4 Summary When the radiation spectrum of the light source contains more short-wave radiation, its luminous efficiency will increase with the decrease of the human eye adaptation level. For example, metal halide lamps (xenon lamps) belong to this category, and their luminous efficiency is equivalent in dark vision. Yuming's vision is about 2 times; due to the different spectral radiation power distribution, the luminous efficiency of some light sources fluctuates with the adaptation level of the human eye. For example, when the low-pressure sodium lamp is at the 1cd/m2 human eye adaptation level, its luminous efficiency increases by 10%. The dark ray's luminous efficiency is only about 1/5 of that of Ming Vision. The effect of the luminous efficiency of such a light source on the level of adaptation of the human eye is not negligible in the design of road lighting.
Under the condition of road illumination, the cone photoreceptor cells and the rod photoreceptor cells in the human eye are in an active state, and the peripheral vision played by the two photoreceptors is very sensitive to the discovery of moving objects in front, etc., so road illumination is performed. The design also considers the influence of the light source with different relative power distribution under different road lighting levels on the visual response time, which is also a major factor affecting driving safety.
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