Integrating spheres are relatively new to us, but they are indispensable. What exactly is the role of the integrating sphere?

1. What is an integrating sphere?

Integrating sphere is a cavity sphere coated with white diffuse reflective material on the inner wall, also known as photometric sphere, optical flux sphere, etc.. The inner wall of the ball is coated with the ideal diffuse reflective material, also * is the diffuse reflection coefficient close to 1 material. The commonly used material is magnesium oxide or barium sulfate, it will be mixed evenly with the gel adhesive, sprayed on the inner wall.

2. The principle of integrating ball

After the light is incident from the input hole, the light is reflected and diffused evenly inside this ball, so the light obtained from the output hole is a fairly uniform diffuse beam. The angle of incidence, spatial distribution, and polarization of the incident light do not affect the intensity and uniformity of the output beam. Because the light is integrated inside the integrating sphere before it is emitted, the integrating sphere can also be used as a light intensity attenuator. Its output intensity to input intensity ratio is about: the area of the light output hole / the internal surface area of the integrating sphere.

3. The role of the integrating sphere

1. Light receiver

The measured light enters the ball through a small hole in the integrating sphere, and one or two light detectors are set on the inner wall, and the light current output by the light detectors is proportional to the illumination of the inner wall of the integrating sphere. This * can be based on the change in the output photocurrent to know the change in the light flux into the integrating sphere.

2. Uniformly illuminated object surface

On the inner wall of the integrating sphere with the light outlet hole symmetrically set up several bulbs uniformly (usually four or six). The light emitted by the bulb through the inner wall many times diffuse reflection and the formation of a uniform bright light-emitting sphere, the integrating sphere for the photographic objective vignetting coefficient and image surface illumination uniformity measurement.

3. Spherical parallel light tube

With collimation objective, bulb, and black and white plug of the integrating sphere is called spherical parallel light tube, it is used to measure the telescopic coefficient of stray light coefficient. Measurement, through the photodetector respectively measured the illumination of the black body target image and the "white plug" image, but also * is the photodetector respectively measured by the corresponding indicator value, after calculation can be obtained by the measured telescope stray light coefficient. Because, if the telescope to bright sky a black body target image is not all black, it means that the telescope in addition to the target image, there are stray light to the image surface.