Illumination standard and lighting quality

1. Indicators for measuring illuminance:

The standard for measuring illuminance depends on whether it is possible to see the object in the year, and whether it is easy to see the object and whether the subjective feeling is comfortable. Therefore, the illuminance first satisfies the “visibility”, followed by the “satisfaction”. Illumination levels should take into account factors such as visual efficacy, comfort, economy and energy efficiency. Different social conditions and illuminance levels in different regions may have large differences.

1, visibility:

When the object's detail size is determined, the visibility depends on the illuminance and the brightness contrast of the job. The visibility of the human eye increases rapidly with increasing illumination. When the illuminance exceeds 500 lx, the illuminance must be multiplied by increasing the visibility. This has led to a significant increase in costs and the need for an economic analysis.

2. Satisfaction:

Satisfaction is determined by two aspects: one is the ease of viewing under actual conditions; the other is the degree of comfort and satisfaction of the visual environment. The former is a physiological indicator; the latter is a psychological indicator. People's psychological satisfaction is governed by factors such as personal hobbies, cultural level, appreciation and past experience, and is related to the indoor color and furnishings of the lighting environment.

Second, the illuminance standard rating :

The illuminance level difference is the smallest difference that can be reflected subjectively and is consistent with the CIE recommendation. The standard level of contrast in "Industrial Enterprise Lighting Design Standards" is as follows: (unit: lx): 0.5, 1, 2, 3, 5, 10, 15, 20, 30, 50, 75, 100, 150, 200, 300, 500 , 750, 1000, 2000, 3000. Among the adjacent two-stage illuminance, the latter is 1.5 times the best as the former.

Third, the quality of lighting:

The illumination quality includes the brightness distribution of the light environment, illumination uniformity, light color and color rendering, glare limitation level, directionality of light, and stereoscopic effect of the object.

1, brightness distribution:

a), work area brightness distribution:

Work brightness and ambient brightness should not be too disparate to avoid visual fatigue. From the perspective of visual comfort, the ambient brightness is preferably lower than the brightness of the work surface. Lighting with a higher ambient brightness can only be used when the nature of the work requires that the attention of the person is mainly concentrated around. The ambient brightness is preferably not less than 1/3 of the brightness of the job.

b), face brightness and indoor environment brightness:

As far as the brightness of the face is concerned, the UK stipulates that the room illumination and the room illumination of all working rooms are 200lx. This data can be used as a reference value for some public buildings in China.

c), brightness of the lamp:

The brightness limit curve method is commonly used to evaluate the brightness of the lamp, and the brightness of the lamp is determined according to the glare limit, that is, the brightness of the lamp is determined according to the glare limit level and the illuminance. When the visual work is very fine, the glare is strictly limited, and the brightness of the lamp is required to be low. When the general visual operation requires less glare limitation, the brightness of the luminaire is allowed to be higher.

When the illumination is high, the brightness of the lamp is required to be low, and when the illumination is low, the brightness of the lamp is allowed to be high.

2, illumination uniformity:

a), spatial uniformity:

CIE stipulates that the ratio of minimum illuminance to average illuminance is less than 0.8, and the national standard stipulates that it should not be less than 0.7 In the case where the luminaire arrangement is less than the maximum allowable aspect ratio, the above requirements should also be met. The higher the ratio of the maximum allowable distance to the height of the lamp, the more the light is cross-irradiated, and the relative uniformity will be improved.

b), time uniformity:

The illumination of any lighting device will not always change. The illuminance is reduced due to the reduced luminous efficiency of the bulb, the aging of the luminaire, and the ash surface in the room. In China, the final maintenance illuminance is taken as the recommended illuminance, that is, the average illuminance before replacing the light source and cleaning the luminaire is the recommended illuminance, so that the illuminance higher than the illuminance standard is obtained throughout the use period. Under no circumstances should the initial illumination of the new lighting fixture and the clean room be used as illuminance recommendations.

3, light color and color rendering and its application:

The color and color rendering of light is very important in lighting engineering, especially in places where light color and color rendering are required. The color characteristics of light are mainly manifested in two aspects of the color table and color rendering ability of light. Optical radiation consists of many spectral radiations. The more complete the spectral components, the better the color table and color rendering performance of the light. However, the two different spectral components of light can have the same color table, but the color rendering may vary greatly. Therefore, the color rendering cannot be determined according to the color of the light.

a), the color table of the light source:

A-1. Use the CIE1931 chromaticity diagram to indicate the color of the light source:

Any color can be represented on the chromaticity diagram with two color coordinates. The basis is that the color of any kind of light can be synthesized from the three primary colors of red, green and blue. The three primary colors are also referred to as "standard chromatic observer spectral tristimulus values" and are represented by the symbols X(λ), Y(λ), Z(λ). They are three relative sensitivity curves representing the amount of red, green, and blue primary colors required for pure spectral colors of various wavelengths. From the tristimulus value, the color tristimulus value of any one of the light source colors can be further determined and expressed by X, Y, and Z. These quantities are related to the three sensitivity curves and the spectral power distribution of the source.

In the chromaticity diagram, x, y, and z are represented by relative values, obviously there are

x+y+z=1

A-2, using the color temperature to indicate the color table of the light source:

When the spectrum of a heat radiation source (such as an incandescent lamp or a tungsten halogen lamp) is similar to that emitted by a black body heated to a temperature Tc, the temperature Tc is referred to as the color temperature of the light source. The chromaticity diagram of the incomplete radiator source is not on the black body trajectory, but in the vicinity of the trajectory, the color temperature can be expressed by the "correlated color temperature". The concept of correlated color temperature is only meaningful for light sources with a spectral energy distribution and a complete radiator approximation.

The relationship between color temperature and light color is as follows:

A-3, the properties of the light source color table and the application of the color table:

The color temperature of the light source is different, giving people a different feeling. The low color temperature has a warm feeling, and the high color temperature has a cold feeling. CIE divides the color table of the lamp into three categories, as shown in the table below. The first set of warm tones is suitable for residential areas such as homes, hotels, restaurants, and special operations or cold weather conditions; Group 2 workplaces are the most widely used; Group 3 cool colors are suitable for high-light areas, special operations or Warm climatic conditions.

In 1941, Kludoff of Germany quantitatively proposed the range of the light color comfort zone, and later studies confirmed his conclusion.

The first criterion of Kludoff is that in order to display the normal color of the object being viewed, light sources of different colors should be selected according to the illumination. Warm colors are used for low illumination and cool colors for high illumination. For example, in low light, the warm color of pink, light orange or light yellow is not, the human skin color is "gentle" natural, and the cold color makes the human skin pale and terrible. The use of a cool color similar to daylight in high illumination makes the skin color appear more natural and real. The second criterion of Kludolf is that the color can be truly reflected only under appropriate high illumination, and low illumination cannot show the nature of color.

Light with low color temperature in low illumination makes people feel happy and comfortable. When high illumination, it is irritating. Light with high color temperature feels gloomy, dim and cold in low illumination, and feels comfortable and pleasant in high illumination. Therefore, in low illumination, warm light is used, which is close to the twilight mood, creating an intimate and relaxed atmosphere indoors; in high illumination, cold light should be used to give people a tense and lively atmosphere.

In the light source, the color of light with poor color rendering is also not good, such as fluorescent high pressure mercury lamp Ra is 30~40, lacking red light component; sodium lamp Ra is 23~25, only yellow component is highlighted in light. The use of the former in the room makes the skin pale; the latter makes the person yellow and yellow. Neither of these lamps should be used separately for indoor lighting .

b), color rendering of the light source:

4, glare restrictions:

a), glare types and effects:

Glare is due to excessive contrast or high brightness in the field of view. Glare can cause discomfort or reduce visibility. There is discomfort called discomfort glare; reducing visibility is called disability glare. In addition, there is a visual state of both.

Glare also has the difference between direct glare and reflected glare. Direct glare is directly caused by high-intensity light sources such as lamps, bulbs, windows, etc. Reflected glare is caused by the reflection of high reflectance surfaces such as mirrors, shiny metal surfaces or other surfaces. The glare produced by regular reflections in the direction of the eye is called reflected glare. When the light is reflected to the eye, the working body is masked, and the contrast between the working body and the surrounding object is weakened, and the visual difficulty is called light curtain reflection.

Lighting is divided into two categories: one is for bright lighting, the main function is to limit glare; the other is for ambient lighting, mainly to form better ambient lighting to meet certain special requirements. Therefore, a small area of ​​glare of metal, glass, and glossy objects is often used to produce some charm. There is no limit to glare in this case.

There are four factors that determine the intensity of glare: 1. The higher the brightness of the light source, the larger the area, the more severe the glare; 2. The darker the surrounding environment, the more severe the glare; 3. The closer the light source is to the eye, the more severe the glare; 4. The light source The closer the position is to the line of sight, the more severe the glare.

b) Classification of glare restrictions:

"Industrial Enterprise Lighting Design Standards" (GB50034-92) is recommended to be classified according to five levels; "Civil Building Lighting Design Standards" (GBJ133-90) is divided into three levels.

c), brightness control method:

Glare is mainly caused by the brightness of the lamp itself, so measures are taken to limit the brightness of the lamp in the direction of the human eye. The method is to hide the lights in the fixture or to combine them with the building components. Brightness control has methods such as occlusion, deflection direction, use of translucent materials, and indirect illumination.

The occlusion light can be used for illuminator reflectors, light-shielding grilles, shading rings, light barriers, and the like. The more light that is blocked, the lower the illumination efficiency. Therefore, designs often make choices in reducing brightness and improving efficiency.

The light can be redirected by an optical device, such as a lens, a prism, a mirror, or the like.

The full diffuse transmission of a translucent material reduces the brightness of the source. Brightness is a function of the amount of internal light and the projected area of ​​its surface. The larger the area, the lower the surface brightness. Translucent materials reduce the brightness, but the light flux from the light source is not much reduced, and it is suitable for places where vertical illumination is required, such as frosted glass cover, opal glass lamp cover, etc. Brightness can also be controlled in combination with other methods, such as translucent light barriers and shade grids. Controlling the brightness of indirect illumination is a combination of two principles. One is to hide the light by applying the occlusion method; the other is to apply the yaw direction to the light to the secondary illuminating member (the ceiling or the wall). The larger the area of ​​the secondary illuminator, the more uniform the brightness, and the lower the surface brightness, the better the effect. Sometimes indirect lighting, occlusion, and deflection can be combined to achieve better results.

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