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3nh
2025-02-09
Cotton grading is an important part of cotton quality evaluation. However, in the process of cotton grading, the unstable light source environment can easily lead to deviations in grading results. In order to unify the light source environment for cotton grading, there are regulations on the light source for cotton grading. So, what light source is used for cotton grading? This article introduces the light source and lamp models for cotton grading.
Cotton grading light source
Cotton grading is an important part of cotton quality evaluation, among which the evaluation of cotton color, gloss, fiber quality and other aspects is the key. In order to ensure the accuracy and consistency of these evaluations, it is necessary to use standard light sources that meet international standards for inspection. In cotton grading, the commonly used light source is D75 light source.
The D75 light source is a standard light source that simulates the average sunlight in the north, and its color temperature is 7500K. Because sunlight varies with climate and time, its light source color temperature varies between 5500 and 7500K. Color temperature is a representation of the color quality of the light source. The color quality of a light source means understanding the hue tendency and color saturation of the light from a light source. Technically, we use color temperature (K) to represent the color quality of a light source. Regarding color temperature and light source color quality, it can be considered that the higher the color temperature, the colder the light, and the lower the color temperature, the warmer the light.
In simple terms, D75 light source is also a standard light source that simulates daylight. The main difference between it and the commonly used D65 and D50 in China is the color temperature.
Standard illuminant D represents the relative spectral power distribution of sunlight at various phases, also known as typical sunlight or reconstructed sunlight. Since standard illuminant D has a relatively close relative spectral power distribution to actual sunlight, and is more consistent with the chromaticity coordinates of actual sunlight than standard illuminants B and C. Therefore, CIE recommends the use of standard illuminant D first. Standard illuminant D is divided into several types such as D50, D55, D65, and D75. When standard illuminant D65 cannot be achieved, it is recommended to use standard illuminants D50, D65, and D75 as much as possible. Their relative spectral power distribution curves are shown in the figure.
D75 light source relative spectral power distribution curve
The correlated color temperatures of standard illuminants D50, D55, D65 and D75 are 5000K, 5500K, 6500K and 7500K respectively. As can be seen from the above figure, the spectral power distribution curves of standard D50, D55 and D75 are very similar to that of D65.
Cotton grading light source
At present, there are many brands and models of D75 light source lamps on the market. Here we mainly introduce 3nhD75 light source lamps.
3nhD75 light source color matching lamps are mainly divided into 20W and 40W models, which are suitable for cotton inspection and grading rooms to evaluate cotton color and other similar occasions. They replace traditional north-facing skylight daylight, are more stable than natural light, overcome the influence of geographical location, season, weather conditions and other factors, can work day and night, and improve efficiency.
Among them, the 20W d75 color matching lamp tube is 60cm long, and the lamp color rendering index Ra≥92%, which has a superb color reproduction effect.
Cotton grading lamp
The 40W d75 color matching lamp tube is 120cm long and has a display index Ra≥92%, which has a superb color reproduction effect.
Cotton grading lamp
Different power lamps have different light intensities, which is what we usually call the "brightness" of the lamp. Different power D75 color matching lamps can be selected for different places. 3nhD75 light source lamps have the following characteristics:
1. Light source
High light efficiency, high color rendering index, restores the true color effect of the illuminated object, and makes vision more comfortable.
2. Card holder pins
Silver electroplating technology, high metal purity and good conductivity, effectively prevents oxidation and is durable.
3. Lamp body
The lamp body is made of high-quality aviation-grade material, which is easy to install, high temperature resistant and has good heat dissipation performance.
Cotton grading light box
1. Illumination requirements
Too much or too little light will affect the classer's accurate observation of cotton fibers. Too much light may cause the color of the fiber to be distorted, while insufficient light will make the details blurred. In cotton grading, the recommended light range is:
Illuminance E: (750±100)lx
Illuminance uniformity Ux: Us＞80%
This range of illumination ensures that the classifier can clearly see the color, impurities and length of the cotton fiber, so as to make accurate grading judgments. In addition, in order to maintain the stability and uniform distribution of illumination, the lighting equipment in the grading room should be maintained regularly to ensure that it is in good working condition.
2. Color temperature requirements
The choice of color temperature is also important for cotton grading because it can affect the classer's perception of the color of the cotton fiber. For cotton grading, the recommended color temperature range is:
Correlated color temperature Tc: (7500 ± 200) K
Correlated color temperature uniformity Ur: U＞80%
Color temperature within this range can better restore the natural color of cotton fibers, preventing graders from making wrong grading decisions due to the influence of light source color. If the color temperature is too high, the cotton fibers may look too cold and white, affecting color judgment; while if the color temperature is too low, the cotton fibers may look too warm and yellow, which is also not conducive to accurate grading.
