How to prevent lamp glare

"Glare" is a bad lighting phenomenon. When the brightness of the light source is very high or the brightness difference between the background and the center of the field of view is large, "glare" will emerge. "Glare" phenomenon not only affects viewing, but also has an impact on visual health, which may cause disgust, discomfort and even loss of eyesight.

For ordinary people, glare is not a strange feeling. Glare is everywhere. Downlights, spotlights, high beam lights of oncoming cars and sunlight reflected from the opposite glass curtain wall are all glare. All in a word, the uncomfortable light that makes people feel dazzling is glare.

How is glare formed? The main reason is the scattering of light in the eye.

When light passes through the human eye, due to the heterogeneity or different refractive index of the components constituting the refractive stroma, the propagation direction of the incident light changes, and the outgoing light mixed with scattered light is projected onto the retina, resulting in the reduction of the contrast of the retinal image, which leads to the decline of the visual quality of the human eye.

According to the consequences of glare, it can be divided into three types: adaptive glare, uncomfortable glare and incapacitated glare.

Adaptive glare

It refers to that when a person moves from a dark place (cinema or underground tunnel, etc.) to a bright place, due to the strong glare source, a central dark spot is formed on the retina of the human eye, resulting in unclear vision and decreased vision. Generally, it can be recovered after a short adaptation time.

Inadaptable glare

Also known as "psychological glare", it refers to visual discomfort caused by improper brightness distribution and bright light sources within the sight (such as reading in strong sunlight or watching high brightness TV in a dark house). This maladjustment, we usually subconsciously avoid the loss of vision through visual escaping. However, if you are in an environment that is not suitable for glare for a long time, it will cause visual fatigue, eye pain, tears and vision loss;

Disabling Glare

It refers to a phenomenon that the contrast of human retinal image decreases due to the messy glare light sources around, resulting in the difficulty of image analysis by the brain, resulting in the reduction of visual function or temporary blindness. The experience of getting dark because of observing the sun for a long time or being illuminated by the high beam of a car in front of you is incapacitated glare.

The psychological parameter to measure the glare parameters of a lamp is UGR (Unified glare rating). In 1995, CIE officially adopted UGR value as an index to evaluate the uncomfortable glare of lighting environment. In 2001, ISO (International Organization for Standardization) incorporated UGR value into the lighting standard of indoor workplace.

UGR value of a lighting product is divided as follows:

25-28: severe glare unbearable

22-25: dazzling and uncomfortable

19-22: slightly dazzling and tolerable glare

16-19: acceptable glare level. For example, this file is applicable to the environment that needs light for a long time in offices and classrooms.

13-16: do not feel dazzling

10-13: no glare

< 10: professional grade products, applicable to hospital operating room

For lighting fixtures, inadaptable glare and disabling glare can occur at the same time or alone. Similarly, UGR is not only a visual puzzle, but also a puzzle in design and application. In practice, how to reduce UGR to comfort value as much as possible? For lamps, the lower UGR value dose not mean to remove the light when looking directly at lamps, but to reduce the light at a certain angle.

1.The first is design

Lamps are composed of shell, power supply, light source, lens or glass. At the initial stage of design, there are many methods to control UGR value, such as controlling the brightness of light source, or making anti-glare design on lens and glass, as shown in the following figure:

2. It's still a design problem

Within the industry, it is generally agreed that there is no UGR when the lamps meet the following conditions:

① VCP (visual comfort probability) ≥ 70;

② When viewed longitudinally or transversely in the room, the ratio of the maximum lamp brightness to the average lamp brightness at the angles of 45 °, 55 °, 65 °, 75 ° and 85 ° from the vertical is ≤ 5:1;

③ To avoid uncomfortable glare, the maximum brightness at each angle of the lamp and the vertical line shall not exceed the provisions of the following table when viewed longitudinally or transversely:

3. Methods of controlling UGR in later stage

1) Avoid installing lamps in the interference area;

2) The surface decoration materials with low gloss shall be adopted, and the reflection coefficient shall be controlled between 0.3 ~ 0.5, which shall not be too high;

3) Limit the brightness of lamps.

In life, we can adjust some environmental factors to try to keep the brightness of various lights in the field of vision consistent, so as to reduce the impact of this glare on us.

It is not the truth that the brighter the light is, the better is. The maximum brightness that human eyes can bear is about 106cd / ㎡. Beyond this value, the retina may be damaged. In principle, the illuminance suitable for human eyes should be controlled within 300lux, and the brightness ratio should be controlled at about 1:5.

Glare is one of the most important factors affecting lighting quality. In order to improve the quality of light environment of home, office and commercial, reasonable measures must be taken to limit or prevent glare. Wellway can effectively avoid glare and provide customers with a comfortable and healthy light environment through early lighting design, lamp selection and other means.

Taking wellway's LED louver fitting, ELS series as an example, we adopt high-quality lens and aluminum reflector, exquisite grille design and reasonable luminous flux to make the UGR of the product reach about 16, which can meet the lighting demands of classrooms, hospitals, offices and other environments, and create bright and healthy environmental lighting for special group of people.