Guidelines for purchasing point balls

2023-10-09 21:58:39 303

The integrating sphere is a hollow sphere with a diffuse reflective coating on the inside and a carbon steel metal structure on the outside, with small holes on the side. Test the finished lamp with a large integrating ball, and test a single lamp bead with a small integrating ball.

The method of purchasing point balls

　　1、Firstly, determine the required size of the integrating sphere:

　　Choosing the most suitable integrating sphere should be carefully considered based on the actual needs of the measurement. Generally speaking, the diameter of the integrating sphere should be more than twice the size of the devices (including brackets) installed inside the sphere, and the larger the multiple, the better; The smaller the total area of the opening on the ball wall, the better, with a maximum of 5% of the total area of the ball; The output signal of a small diameter integrating sphere with the same opening is strong, which means high conversion efficiency, but the integrating effect of the sphere is worse. So the size of the integrating sphere should be chosen appropriately.

　　2、To determine the number of openings for the integration ball you need:

　　Generally speaking, open 1-2 holes to measure the luminous flux of the light source; When measuring the reflectance, transmittance, and fluorescence characteristics of the sample, the integrating sphere has 3-4 holes; When using dual optical path measurement, more than 4 holes can be opened. It should be noted that multiple openings can affect the integration effect, so it is important to make reasonable openings based on actual measurement needs.

　　3、The position and size of the hole in the integrating sphere:

　　It should be considered based on actual measurement needs. Generally speaking, the position of the opening of the integrating sphere should be determined according to the designed optical path, which should be conducive to adjusting and fixing the optical path; The size of the opening should meet the usage conditions of the light spot and receiver.

　　4、Add a partition between the sample hole and the receiver:

　　A screen is usually added between the input beam and the output hole, and the function of the integrating sphere partition is to prevent the primary light from entering the receiver to improve measurement accuracy.

　　5、The inner wall coating of the integrating sphere

        The key to integrating the sphere is to homogenize the uneven incident light, so the inner wall coating is a key factor affecting the measurement, and the selection of coating mainly depends on the following four aspects:

        ① Diffuse reflectance: The directional nature of the integrating sphere LED light is very strong, and it must undergo multiple reflections to achieve uniform distribution of light inside the sphere. Therefore, a reflectance of over 95% is required; Projection lights have stronger directionality and higher requirements for diffuse reflectance.

        ② Lambert characteristics: Lambert characteristics refer to the diffuse reflectance performance of coatings. Good coatings have the same brightness value when viewed from any angle, regardless of the angle of incident light. In this case, sampling is only meaningful.

        ③ Spectral selectivity of coating reflectance: Spectral reflectance refers to the reflectance of coatings at different wavelengths. The flatter the spectral reflectance curve, the more reliable the measurement results are, indicating that the coating has no wavelength selectivity.

        ④ Stability: The chemical composition of the integrating sphere coating changes over time. Some coatings oxidize, turn yellow, or even peel off shortly after being exposed to ultraviolet light, indicating that the chemical composition has changed, and changes in reflectivity, Lambert characteristics, and spectral selectivity are inevitable.

　　6、Sometimes other accessories need to be considered:

　　If the opening of the integrating ball is not in use, use a hole plug to plug it; A light trap is a cylindrical cavity coated with strong absorption black paint to collect the specular reflection components of the sample; For example, an integrating sphere adapter is used to connect other devices, etc.

Method for selecting the size of the integrating sphere

The size of the integrating sphere is generally specified based on the diameter of the side opening, which is generally divided into 0.3m, 0.5m, 1.0m, 1.5m, 1.75m, 2.0m, etc.

1. To ensure that the errors caused by the baffle and self absorption in solid-state lighting product testing are not too significant, the size of the integrating sphere should be large enough;

2. In order to prevent the heat of the light source to be tested from increasing too high with temperature, the size of the integrating sphere should be large enough;

3. In order to avoid the detector receiving signals that are too weak and the exposure time is too long, the size of the integrating sphere should not be too large.

4. In general, for measuring a 500W or stronger light source, a 2m or larger integrating sphere should be used;

5. Typically, compact fluorescent lamps use a sphere size of 1m or larger. The larger the lamp, the larger the required size of the integrating sphere. For example, high intensity gas discharge lamps and four legged linear fluorescent lamps should use an integrating sphere of 1.5m or larger;

6. In a 2 π geometry, the diameter of the opening used for installing solid-state lighting products should be less than 1/3 of the diameter of the sphere;

7. In a 4 π geometry, the total surface area of solid-state lighting products should be less than 2% of the spherical wall area. The diameter of the corresponding spherical object should be less than 1/7 of the diameter of the integrating sphere, and the diameter of linear products should be less than 2/3 of the diameter of the sphere.

Overall, the 30cm integrating sphere system is mainly used for measuring the light, color, and electricity of a single LED; The 50cm integrating sphere system is mainly used for measuring the light, color, and electricity of single LED, COB, modules, and small light sources; The 1m integrating sphere system is mainly used for measuring the light, color, and electricity of a single LED, COB, module, and light source; The 2m integrating sphere system is mainly used for measuring the light, color, and electricity of COB, modules, light sources, and lamps; The 3m integrating sphere system is mainly used for measuring the light, color, and electricity of light sources and lamps.