What You Need to Know About Anti-Reflection Coatings
Typically used to decrease the reflectivity of an object, optical coatings are specially designed as anti-reflection coatings. There can be a variance in the extent to which reflectivity can be lessened, depending on the composition of anti-reflection coatings. Regardless, the same method goes into making every anti-reflective coating:
- Opposing reflective index materials are alternately layered.
- This way the desired spectrum is transmitted because certain light wavelengths are blocked.
- Depending on the application, the design of anti-reflective coatings typically affects ultraviolet, visible, or infrared light.
- Compared to others, some coatings block a greater range of light.
Note: The relationship of a coating to light wavelengths should be fully understood when considering optical coatings and anti-reflection coating types in general. That relationship will not be discussed here but should be researched in order to make an informed decision as to the type of anti-reflective coating needed for an application.
Types of Anti-Reflection Coatings
The number of layers typically classifies different types of anti-reflection coatings: i.e., multilayer or single layer. Also available is a coating referred to as absorbing anti-reflection, which is the third kind of coating of this sort.
- Thin-film – An anti-reflection coating referred to as thin-film reduces reflectivity at one quarter of the wavelength light.
- Thick-film – Typically, reflectivity is increased when thick-film coatings are used. Compared to the wavelength of light hitting the coating, this film is thicker. The angle at which a coating’s surface is hit by light, and the wavelength of light, will both determine a coating’s effect on reflectivity.
- Thin-film interference – When the lower and upper layers of an anti-reflective coating reflect incident light waves, what occurs is referred to as thin-film interference. The light waves reflected interfere with each other but, eventually, another light wave is formed when they merge.
Light Spectrum
Anti-reflective coatings are designed to block different kinds of light spectrums. To describe these spectrums of lights, terms such as dual band, narrowband, and broadband are used. Infrared light is blocked by high-efficiency coatings. On the other hand, over a wide range of wavelengths, reflectivity is reduced by broadband coatings. The appropriate coating will be determined by the precise light spectrum that someone is trying to block or transmit.
Antiglare Treatments
Antiglare treatments and anti-reflective coatings are not the same. To defragment the reflected light off of a surface, antiglare solutions use diffusive properties. The difference between antiglare treatments and antireflective coatings is the capacity at which they eliminate or diffuse light waves in all spectrums – from UV to longwave infrared.
Common Applications of Anti-Reflection Coatings
So, who uses anti-reflection coatings? In planetary astronomy, they are particularly essential. They are used to reduce reflection in microscopes and telescopes and eliminate stray light, thereby improving an image’s contrast.
Anti-reflection coatings are also used on binoculars to reduce glint for the viewer and to make the eyes of a glasses wearer more visible to people looking at them.
In micro electric photolithography, these coatings are used to reduce image distortions. Otherwise, from the surface of the substrate, reflections could interfere. Either after or before the photoresist, various kinds of anti-reflective coatings are applied. This helps reduce specular reflections, thin-film interference, and standing waves.
A&A Coatings has the appropriate coating for your company, no matter what industry you are involved in. For decades, we have assisted owners and operators in making an informed decision as to which type of coating will best serve their needs. Talk to one of our knowledgeable representatives today to find out how thermal spray coatings can make a difference in your business.
