The principle and application of optical integrating sphere

Optical integrating sphere is an important optical measurement device used to evenly distribute optical signals within a spherical surface, thereby achieving accurate measurement of parameters such as luminous flux, light intensity, and spectrum. Its basic structure is a sphere coated with high reflectivity diffuse reflective material inside, usually made of white coating or diffuse reflective material, and can be equipped with a light source or detector inside.

working principle

The working principle of an integrating sphere is based on multiple diffuse reflections. When the light from the light source enters the sphere, due to the extremely high diffuse reflection characteristics of the inner wall of the sphere, the light can be evenly distributed after multiple reflections on the inner wall of the sphere. This uniformly distributed light is captured by a detector through a detection window on the sphere, enabling the measurement of optical parameters.

Integral spheres typically have multiple openings, such as an entrance, a detection port, and a light source port. The entrance port is used for light to enter, the detection port is used to connect the detector, and the light source port may be used for calibrating the light source or ventilation. By designing the size and position of these openings reasonably, the uniformity of light distribution inside the integrating sphere can be ensured.

application area 

Luminous flux measurement: Integral spheres are widely used for measuring luminous flux, such as the total luminous flux test of LED lights. Its uniform distribution characteristic eliminates the influence of light source directionality on measurement results, thereby providing more accurate measurement results.

Spectral measurement: In spectral analysis, an integrating sphere can be used to collect light signals from various directions and guide them to a spectrometer for analysis. This is particularly important when measuring the emission characteristics of complex light sources.

Measurement of material reflectivity and transmittance: Integrating spheres can be used to measure the diffuse reflectivity and transmittance of materials. By placing the material between the light source and the integrating sphere and comparing the changes in light signal intensity with and without the material, the relevant optical parameters of the material can be calculated.

Calibration of optical equipment: Integrating spheres are often used as calibration standard light sources to provide stable and uniform light output.

Advantages and limitations

The advantage of an integrating sphere is its ability to achieve uniform distribution of light, making measurement results more reliable. However, its limitation lies in the high quality requirements for the internal coating, and the reflectivity and stability of the coating will directly affect the measurement accuracy. In addition, the volume of the integrating sphere is relatively large and not suitable for portable scenarios.

summary

Optical integrating spheres have played an important role in the field of optical measurement due to their unique ability to uniformly distribute light. With the continuous development of optical technology, the application range of integrating spheres is also expanding, and further breakthroughs may be made in miniaturization design and high-precision measurement in the future.