Coating

Green Optics produces special coating sand products to meet customer needs. Coating design is applicable to all sectors, from ultraviolet rays to far-infrared rays, and the design and coating methods are continuously studied and deceloped, according, according to related industry and performance improvement of the products.

An optical multi-layered thin film consists of the combination of various materials and thicknesses to meet the capacity required for an optical filter. Filters often needto separate the wavelength of special parts. In particular, this is increasingly important for laser mirrors or spectroscopes. Although the application scope of filters is broad, the scope will include one of the followingcoating types.

1. Although an optical system consists of a single factor or complex factor, it is most important to control the transmission of energy that passes through the system. Energy control means to maximize the amount of energy that passes through the system, while minimizing the amount of energy that generally disperses or misses the target. Non-reflection coating is the method that is the most ideal for this. Non-reflection coating can be considered as an impedance transformer that delicately harmonizes theimpedance between the media neighboring the coated surface. Precise impedance adjustment in a single wavelength or in the very narrow band wavelength is relatively simple. Also, 1 layer or 2 layer coating layers are enough for this method. However, as wavelength band range increases, the number of coating layers increases and it becomes gradually more difficult to maintain impedance perfectly with regard to the entire bands.
   
   
2. It is important to sort the desired energy band out from the undesired energy band, and there are many application fields for an interference filter. A transmitting filter is designed to absorb or reflect undesired energy bands, that it, shorter or longer wavelength bands, and in general transmit the desired wavelength. A reflecting filter is designed to reflect the desired band. However, it cannot make a high ratio of signal to noise like a transmitting filter. Interference filters can be divided into single color filters, which take out the narrow light from a successive spectrum, and band filtersthat take out a relatively wider range of light. Coating should be designed for cut-on and cut-off slopes to be generally steep.
   Namely, theborder from low transmission bands to high transmission bandsshould be clear.
   In theory, the gradient should be l% or less. To achieve this, a great number of coating layers are needed. However, a 5% or 6% gradient seems to be an adequate compromise point between high performance and adequate price.
   
   
3. A reflecting coating is designed to perfectly reflect energy at a specific wavelength. Although it is a simple concept, there is a relatively many number of coating layers and difficulties when a reflection rate of 99.5% or more is required in the scope beyond 10% from central wavelength of reflecting coating in reflecting scope. For the main application fields, this is widely used in an opticalsystem to change the direction of beam, rotate the image, change the polarization ingredients and effectively change energy over wider wavelength than proved by refraction ingredients.
   
   
4. Conductive transmission coating consists of a conductive layer and augmentation layers top and bottom to maximize the transmission rate and electrical conductivity in a specific wavelength scope. The resistance of a completely even thin film can be measured by bus bars located in the two opposite ends of independent blind spots of the film (Four terminal measuring methods). The resistance measured for such a thin film is indicated to be independent (ohms per square). Thin film resistance is typically 1-100,000 in the 60-98% transmission range. The two most general conductive transmitting coatings used in the visible scope are TPG thin film and ITO thin film. These are used as an anti-power failure device for contact switches, LCD's pattern electrode and optical lens and window. Conductive transmitting coating is also used to prevent transmission of an undesired high frequency or radar wave fromcomputer displays or TV screens.