Product series：Optical coating

product model: product

product specification: product

service life: product

Product description

There are many reasons to affect the transparency of a plane lens. The roughness of the mirror will cause incident light diffusion, reduce the transmittance of the lens. In addition, the optical absorption material, it will cause some incident light source which is particularly serious part of the frequency of dissipation. For example, the material that absorbs red light appears to be green. However, these poor processing factors can be removed as much as possible. 　　It is a pity that there is a defect in nature. When the incident light passes through different media, the reflection and refraction will occur. If we are perpendicular to the material, we can define the reflectivity and transmittance.

Refractive index of coating

In fact, these two issues are consistent. As long as we can understand the first question, the other naturally smoothly done or easily solved.

According to the basic theory of electromagnetics, the transmission and reflection of different media are mentioned.

If the medium N1 is perpendicular to the N2

reflectivity＝[ (n2 －n1) / (n1+n2)

Penetration rate＝4n1n2 / (n1+n2)2

（1）Directly from the air into the glass

Penetration rate＝ 4×1.0×1.8 / ( 1+1.8 )2＝91.84%

（2）From the air into the film and then into the glass

Penetration rate＝[ 4×1.0×1.5 / ( 1+1.5 )2] × [ 4×1.5×1.8 / ( 1.5+1.8 )2]＝95.2%

Visible coated glass will increase the transmittance. In addition to this formula, we can calculate the light penetrating the two sides of the lens, and found that even if a perfect lens (refractive index 1.8), the transmittance is about 85%. If a layer of coating (refractive index 1.5), the transmittance of up to 91%.

Coating thickness

Finally, we want to explore the different thickness of the coating, what will be the impact? We already know that the transmittance is related to the refractive index of the coating, but nothing about its thickness. But if we can in the coating thickness on the bit, will find the reflection light reflected light A and optical path difference of NC B * 2D difference. If

nc×2D＝（N+ 1/2）λ among N= 0,1,2,3,4,5..... λ The wavelength of light in the air

Reflection will result in the light of specific wavelengths have destructive effects, so the color of reflected light will change.

In many complex optical systems, the suppression of reflected light is a very important lesson. Therefore, a set of lenses, the use of different thickness of the coating to eliminate the different frequency of reflected light. Therefore, the higher the optical system, the color of the reflected light will be more.