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Excellent CREE flashlight design, advanced LED flashlight equipment, to enjoy CREE flashlight gives us the comfort and convenience. But the problem of glare (glare), has been a very big headache.
What is glare? Why would produce glare? How to reduce or even eliminate glare?
Glare: Perspective of the luminance distribution or the brightness range is inappropriate, or extreme contrast exists, thus causing an uncomfortable feeling or reduce the ability to observe the detail or target visual phenomenon.
Glare is a bad visual phenomena, it will make people feel the glare cause eye pain, tearing, decreased visual acuity, and may even temporarily lost, as the ability to see.
Glare reduced visual function mechanism to understand: issued by the glare source of light scattering in the retinal direction to form a bright light screen, superimposed in the clear on the scene like. The light curtain has an equivalent light screen brightness (equivalent veiling luminance), which acts as the background increase the brightness, contrast, decline, engender glare sense, and it is difficult to see the goal.
3 glare Evaluation Method
So far, for the indoor environment, stadiums, motor vehicle road CREE flashlight occasions, it has been summed up the following four major glare evaluation of expressions:
3.1 unified glare value UGR
Unified glare rating value (unified glare rating) UGR calculation:
, Lb - background luminance (cd/m2);
La - observer direction each lamp brightness (cd/m2);
ω- each luminaire light emitting portion is formed on the observer's eye perspective angle (sr);
P - each individual lamps position index.
These parameters should be determined according to the following formula and provisions:
1) Lb = Ei / π
Wherein, EI - observer's eye direction and indirect illumination (Lx).
2) La = Ia / A • cosα
The formula Ia - the observer eye direction Luminous intensity (cd);
A • cosα - lamps in the direction of the observer's eye projected area (m2);
α- folder CREE flashlight the surface normal and the viewer's eye direction angle (°).
3) ω = AP / r2
AP - luminaire components apparent area (m2) in the direction of the observer's eye;
r - luminaire parts center distance (m) between the observer's eye.
4) Guth position index P should be Figure 2 generates the H / R and the T / R ratio is determined by the position index table.
System (R, T, H), the ratio of H / R and T / R is generated on the lamp center.