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Light can change the space, it directly affects the person's perception of the size, shape, texture and color of the object. In terms of human vision, there is no light without everything, and in interior design, we often encounter a problem in interior lighting design, that is, glare.
1 It turned out that you are such a glare
Dazzle is one of the important causes of visual fatigue. Due to the unfavorable brightness distribution in the visual field, or the extreme brightness contrast in space or time, the visual conditions that cause visual discomfort and reduce the visibility of the object are caused. The sensation of light that the human eye cannot adapt to within the field of vision may cause disgust, discomfort, or loss of visibility. (If you don't understand it, you can understand it as "glare")
Picture: The normal attention range of the human eye is 30° above the horizontal plane and 60° below. In this range, there is a dazzling light, which is glare.
The mechanism by which the glare reduces the visual function can be understood as follows: The light emitted by the glare source is scattered in the direction of the retina to form a bright light curtain superimposed on a clear scene image. This light curtain has an equivalent veiling luminance, which is equivalent to increasing the background brightness, reducing the contrast, causing people to feel glare, and making it difficult to see the target.
We can classify glare into glare and disability glare. They are defined as:
Uncomfortable glare: glare that does not necessarily reduce the visibility of the object by causing discomfort;
Disability glare: Glare that reduces the visibility of an object without necessarily causing discomfort.
These two glare are produced together, but they are two completely different phenomena. The cause of disability glare is mainly due to the light energy entering the eye, not the illumination of the light source. In contrast, light source illumination is a major factor in discomfort glare. Disability glare is almost unaffected by time, and people in the factory or office are exposed to high-illuminance light for a long period of time, and there is a corresponding increase in uncomfortable glare.
In addition there is a more serious glare - blindness glare, refers to the temporary blindness due to intense light. Therefore, the glare interference must be effectively controlled to ensure the safety and quality of indoor lighting.
2 Those standards about glare
In indoor lighting, in general there will be no disability glare and blinding glare, and there will be more discomfort glare. In the “Architectural Lighting Design Standard†(GB 50034-2013), glare is an important indicator of lighting quality, and The uniform glare index (URG) was used for evaluation.
The UGR value is a kind of glare index, and there are BGI (British Glare Index), CGI (CIE Glare Index), and the like. However, UGR is a more practical indicator that combines the glare evaluation methods established in various countries.
Figure: Generally, there are different UGR value requirements depending on the environment. For example, the typical UGR value for a typical office environment is 19.
In general, UGR values ​​range from 10 to 30. The smaller the number, the lower the glare effect, and the higher the glare effect.
Although the glare is different from the ultraviolet damage to the eyes, it is also very harmful to the eyes. How did glare come about? How can we prevent it?
3 Generation of glare
In our lives, the general causes of glare can be summed up as follows:
1, the brightness of the light source (higher brightness, the more significant glare)
2, the location of the light source (the closer to the line of sight, the more significant glare)
3, the size and number of light source appearance (the larger the apparent area, the greater the number of light sources, the more remarkable glare)
4, the surrounding environment (the ambient brightness is darker, the lower the eye adapts to the brightness, the more significant the glare)
4 Glare control methods
When the illuminance of a naked lamp exceeds a certain limit, the illuminance will be controlled by three types of devices, namely a translucent diffuser, a beam splitter panel, and a light-shielding body or a sunroof. Regardless of the special case in which, for example, a skylight is made of a translucent material rather than an opaque material, the luminance distribution of a lamp using these three types of devices can be conveniently divided into a constant distribution, a variable distribution, and a light distribution distribution.
(1) Constant distribution
The light source and the cover that pass through the diffuse plastic or glass plate usually have an appropriate illuminance, which does not exceed 15 kcd.m-2, and in the critical angle range, the illuminance (Ls) is usually maintained at an appropriate constant, with respect to the light distribution of the light source. The angular distribution ranges from 0°≤θ≤45° and 45°≤γ≤90°.
(2) Distribution of variables
A good design device will gradually reduce the illuminance (Ls) so that the illuminance at a level of 90° is lower than the illuminance of γ=45°. This device is widely used in a recessed luminaire installed in a ceiling and in a large room. In the case of a light-cutting fixture, the area of ​​influence of glare is determined by the light distribution of the fixture, not the actual room size.
(3) Light distribution
Here we talk about the light distribution controlled by the shading plate. Regardless of how much θ becomes smaller than the expected shield angle S, the lamp is still completely shielded. The shield angle S is controlled by the mechanical structure of the lamp.
Figure: Principle of light cut (shield angle), θ
a) The worker's normal sight is not above the horizon;
b) Extremely high power lamps cannot be installed too low to be close to the worker's head.
This method has great practical significance. The masking angle is a simple concept that is easy to define and measure, as shown in Figure 3. However, once shading occurs, the brightness of the visible part of the light source is usually very low, so the degree of glare is actually independent of the size of the room. In addition, with a suitable shape, a particularly perfect grid, the brightness after shading can be greatly reduced while the limit value is also low.
Figure: Measurement of the shield angle S.
Also pay attention to the installation of the lamps, it is recommended to take the following measures:
Figure: The conventional light-blocking angle is based on normal vision elevation angle of 30 degrees, and when the light-blocking angle of the light is greater than 30 degrees, light can be prevented from directly entering the human eye.
1. The built-in lighting has built-in anti-glare baffles or increased grids to increase the shading angle of the lamps (the angle between the edge of the light and the outlet of the lamp and the horizontal line) to reduce the generation of glare.
2, control the lighting projection direction, try to avoid the normal range of human activities, reducing the generation of glare.
3. Control the projection angle of the luminaire so that the elevation angle of the luminaire mounted at the opposite site edge to this direction is more than 30° to reduce the generation of direct glare.
4. Use a low-gloss surface decoration material to reduce the occurrence of reflective glare.
Figure: The deep-illuminated light fixture with deep light source increases the installation height of the light source under the same structure, so as to increase the shading angle.
Note: Some of the information in this article is sourced from Zhongzhao.com.com.
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