The Description of Integrating Sphere Coating

The ideal integrating sphere coating should have below performances:
1. High-Lambert characteristics (good diffuse reflection characteristics)
2. High reflectance in a wide wavelength range
3. High stability
4. Easy construction
5. Easy to remove

The history of integrating sphere coating:
In 1934, Principle of Optics mentioned the description of principle of integrating sphere and the formulations of interior coating: The most important thing for the interior coating of integrating sphere is the perfect diffuse reflection characteristics of itself, especially is non-selective diffuse reflection. It won’t change the color of the light under the repeated reflection inside the sphere. Commonly most use white spray paint technology, generally we recommend the magnesia technology, and atomize the sprayed surface.

Common sprayed integrating sphere coating:
1. BaSO4 integrating sphere coating (the most common in the market):

1) High reflectance
2) Easily spray
3) Easy to remove
4) Non-toxic
5) high-Lambert characteristics (process correctly)

1) Water soluble
2) Not strong enough, easily damaged (eg powder out)

2. Firm integrating sphere coating

High reflectance, waterproof (washable), high-Lambert characteristics (process related)

Slightly low reflectance, difficult to remove, low UV reflectance

3. Integrating sphere coating based on Teflon (PTFE):
Pressed PTFE powder; it uses silicone vacuum rubber to press with the PTFE powder together, the proportion is about 1.0 g cm-3

Advantages: very high reflectance and Lambert characteristics

Disadvantages: more brittle, fragile, sensitive to temperature, poor thermal stability, easily be polluted

4. Sintered PTFE coating:

Advantages: very high reflectance and lambert characteristic, stable

Disadvantages: heavy, expensive