Generally speaking, we believe that glass is transparent and colorless is 100% penetration. In fact, at some angles, the glass will reflect the reflection, which is the reflection of the glass surface. Generally, both surfaces of the glass will reflect, and the material of the glass itself (si, sodium, calcium, etc.) will absorb light. Therefore, strictly speaking, the transparent glass is not 100% penetrated, and both sides are reflected and absorbed (absorption The glass material and thickness are about 0.1%~2%, the example is represented by 0.5%), and only about 91~92% of the transmittance is left. Please refer to the illustration in Figure 1 for a description of this paragraph.
Also because there are reflections on both sides of the glass, for imaging or laser equipment, such as surveillance lenses, laser levels, etc., under certain conditions, there will be two images of image or laser light (ghosting) ) or two laser lights appear because of the reflection of the first or second side of the glass (or lens).
The easiest solution is to apply anti-reflection film (Anti-reflection) with reduced reflectance on the glass (or lens). Generally, anti-reflection films are available in single or multiple layers. Monolayer films are usually plated with magnesium fluoride (MgF2), which can reduce the single-sided reflectance to 2%, and increase the transmittance to 95% to 96%. The film can reduce the single-sided reflectance to 0.5%, and the transmittance can be increased to 98%~99%. If combined with higher quality Glass, such as BK7 with higher content, it can reach nearly 100%. Penetration, however, this can only be a certain band. To reach a wider band, the higher the penetration, the more difficult it is.
Please refer to the illustration in Figure 2 for a description of this paragraph.