1. Antireflective coating (antireflecting film)
When the ray is injected into another medium with refractive index of N1 from the medium with refractive index of N0, the reflection of light will be generated at the interface between two media, and the loss of transmittance, the brightness of image will decrease, and the operating distance will be affected. Affected by stray light, the contrast of the image is reduced. There are many different types of antireflection films available to meet the significant portion of the technical optics needs. However, the complex optical system and laser optics often have special and strict requirements for the performance of antireflection. Besides, the broadband antireflection coating can improve the image quality, the color balance and the action distance, and enhance all the performance of the system. Therefore, the practical needs of production promote the continuous development of antireflection film.
There is no complete systematic method for designing anti-reflection film. The simple and effective way is to use vector method and obtain better structure through trial method. Then it is verified by numerical calculation to eliminate the approximate influence inherent in vector method.
2. Beam splitters
Beam splitter can be divided into beam splitting film and dichroic film, the latter is different according to the color (wavelength) of light, it is a beam of light is divided into spectral components according to the proportion of the same two beam of light, it is at the wavelength of a region, such as the visible region, have the same transmittance, the wavelength of reflection the proportion, so the reflected light and transmitted light has no color, and was neutral. The spectroscope is always tilted, it can split the incident light into reflected light and transmitted light two parts, for different purposes, the spectroscope often have different transmittance and reflectance ratio T/R.
3. Reflectance coating
In the optical film, reflective film and antireflection film are almost equally important for the reflection of optical instrument, because of the characteristics of pure metal film most of them already meet common requirements, so in the discussion of metal reflective film, in some applications, the numerical requirements of higher reflectivity of metal film can reach the additive the additional dielectric film on the metal film to enhance their reflectivity, the other all-dielectric multilayer reflective film, because the reflective film has the highest reflectivity and the minimum absorption rate in laser applications has been widely used.
4. Optical filter
The requirements of a wavelength range of the beam efficiently transmitted from the wavelength of the beam suddenly changed to high-reflection (or suppression) of the interference cut-off filter has been widely used, usually we suppress the shortwave region, the transmission of long-wavelength filter Films are called long pass filters. In contrast, the long-wavelength region is suppressed, and the cut-off filter transmitting the short-wavelength region is called a short-pass filter.