What is the function of the integrating sphere and how to choose it?

The integrating sphere can be used as a light receiver, a uniformly illuminated object surface, and a spherical collimator. When purchasing, it is necessary to determine the size of the integrating sphere, the number of openings, the location and size of the openings, etc. Let's take the integrating sphere of the Hopoocolor as an example, and introduce it in detail.

First, the role of the integrating sphere
1. The integrating sphere can be used as a light receiver
The light to be measured enters the sphere through the small hole on the integrating sphere, and one or two photodetectors are arranged on the inner wall. The photocurrent output by the photodetector is proportional to the illumination of the inner wall of the integrating sphere. In this way, the change of the luminous flux entering the integrating sphere can be known according to the change of the output photocurrent.
2. The surface of the object that the integrating sphere can illuminate evenly
On the inner wall of the integrating sphere, several bulbs (usually four or six) are evenly arranged symmetrically with the light exit hole. The light emitted by the bulb is diffusely reflected by the inner wall to form a uniform and bright luminous sphere.
3. The integrating sphere can be used as a spherical collimator
An integrating sphere with a collimating objective lens, a bulb, and black and white stoppers is called a spherical collimator, which is used to measure the stray light coefficient of the telephoto coefficient. During the measurement of the integrating sphere, the illuminance of the black body target image and the "white plug" image are respectively measured by the photoelectric detector, that is, the corresponding indication values measured by the photoelectric detector respectively, and the stray light coefficient of the telescope under test can be obtained after calculation. Because, if the telescope's imaging of a black-body target in the bright sky is not completely black, it means that the telescope is not only imaging the target, but also stray light hits the image surface.

Second, the selection method of the integrating sphere
1. First, determine the size of the integrating sphere required
The selection of the most suitable integrating sphere should be carefully considered according to the actual needs of the measurement. Generally speaking: the diameter of the integrating sphere should be more than twice the size of the device installed in the sphere (including the bracket), the larger the multiple, the better; the smaller the total area of the opening on the sphere wall, the better, and the maximum does not exceed 5% of the total area of the sphere . The same opening of the integrating sphere with a small diameter has a strong output signal, that is, the conversion efficiency is high, but the integrating effect of the small sphere is worse. Therefore, the size of the integrating sphere should be moderately selected.
2. To determine the number of openings in the integrating sphere you need
Generally speaking: when measuring the luminous flux of the light source, open 1-2 holes; when measuring the reflectance, transmittance and fluorescence characteristics of the sample, the integrating sphere should open 3-4 holes; when using dual optical path measurement, more than 4 holes can be opened . It should be noted that the integration effect will be affected when there are many openings, so the openings must be reasonably opened according to the actual measurement needs.
3. The position and size of the opening of the integrating sphere
It should be considered according to the 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 the adjustment and fixation of the optical path. The size of the opening should meet the conditions of the light spot and the receiver.
4. Add a spacer between the sample well and the receiver
Between the input beam and the light exit hole, a shield is usually required. The function of the integrating sphere baffle is to prevent the primary light of the light source from entering the receiver, so as to improve the measurement accuracy.

Hangzhou Hopoo Light&Color Technology Co., Ltd. focuses on the production, research and development and sales of lighting and electrical testing instruments. The whole series of products are developed and produced in strict accordance with the requirements of ISO9001:2015; all products meet the requirements of CIE; in addition, All products of hopoocolor have passed CE certification and obtained the qualification to export to the European Union. The main products include goniophotometer, integrating sphere, spectroradiometer, illuminometer, colorimeter, and LED test instruments. 

If you want to know more technical or product information, please feel free to contact us.
Sales Department: 86 18069445092, Sales_fob@hopoocolor.com