What Is an Integrating Sphere?
An integrating sphere is a spherical device that reflects light evenly. The interior is coated with a light-scattering material with high reflectivity, such as titanium dioxide, and incident light is multiply reflected in various directions. The repeated reflection of light within the integrating sphere enables spatially integrated and uniform light to be extracted. They are widely used for quality evaluation of lasers and light sources and as experimental equipment in research institutes.
Uses of Integrating Spheres
Integrating spheres can be used to extract light or to emit uniform light. For example, light homogenized by integrating spheres is suitable for detecting the intensity of a light source. Also, when measuring reflectance or transmittance, it is possible to detect reflection and transmission by diffusion besides directly irradiated light. Furthermore, it can also be used as a light source emitting light that is homogenized by integrating spheres. By repeating reflection inside the sphere, it is possible to create a light source with constant intensity.
Principle of the Integrating Spheres
The structure of an integrating sphere is very simple. However, the direction in which light is incident and the part of the sphere where it is detected differ depending on the intended use. Here, we will introduce the principle of measuring reflectance and transmittance, which are characteristic features.
The integrating spheres are an important device when measuring the reflectance and transmittance of a sample. By using an integrating sphere, it is possible to detect the reflection and transmission of light caused by diffusion in addition to light directly hitting the sample. The structure of the integrating spheres is such that light is incident from one side and the sample is placed on the other side. It is important to place the detector at the bottom so that light from the light source does not directly enter the sample. However, since this method is relative to a reference sample, the reference must be set accurately.
In addition to this, there are other ways to detect light and use it as a light source. Since light often differs in intensity depending on its direction, integrating spheres, which can achieve uniformity by using reflection and diffusion, are useful in a variety of places. This device is widely used mainly at universities and other research institutions.