![]() Coatings may not equally well stick to different surfaces.Some additional properties can be relevant for applications: A high thermal stability (chemical stability at high temperatures) is essential. This is the case for application in power meters, for example. In some cases, the ability of a black coating to withstand high optical intensities is relevant. Note that the optical properties of the coating may change with time in particular, there can be aging for operation under extreme conditions. well below 1%) throughout the visible region and may be called super-black. Some coatings have an extremely low reflectance (e.g. For grazing incidence, the reflectance is often substantially increased. Further, the reflectance may substantially depend on the angle of incidence and the polarization of light. if a camera sensor also has some responsivity in the infrared. Often, a wide spectral range is relevant – for example, the full visible range or more, e.g. The performance of a black coating cannot be fully characterized with a single number, for example with the hemispherical reflectance at a particular wavelength for normal incidence (which is typically a few percent, sometimes below 1%). Performance Figures Hemispherical reflectance is a key performance figure. In some space applications, the high emissivity of black coatings is utilized, for example to provide effective cooling by thermal radiation into space, in infrared heaters, or in reference standards for thermal radiation. Strong absorption in the infrared and visible ranges important, also a long lifetime and the durability at elevated temperatures. Thermal solar panels need to efficiently absorb solar radiation and transfer it to water flowing through connected pipes. Similarly, black coatings are needed for pyroelectric detectors and for beam dumps. This may be accomplished with a black coating on a thin metal part connected to a heat sensor. In a thermal power meter, incident light must be fully absorbed and converted to heat. A low reflectance can help to suppress disturbing influences of sunlight. used by the automotive industry, often need to contain black parts having black coatings. However, light may be scattered within the device, and such scattering should be suppressed with a suitable black coating in order to avoid a substantial degradation of image quality.ĭisplays, e.g. For example, a photographic objective may be hit by sunlight under an angle for which there is no nominal transmission of light to the image sensor. Similarly, in imaging applications it is desirable to suppress a stray light as much as possible. This is particularly important for applications where faint spectral components need to be detected in the presence of strong light at other wavelengths – for example, in Raman spectroscopy. For that purpose, optimized black coatings can be used. A very low degree of reflectance is desirable. Therefore, the housing must be equipped with light-absorbing materials – ideally, not only the inner side of the box, but also light shields at well chosen positions. It must be made sure that all other wavelengths components, which should be suppressed, do not get through the exit slit in other ways by scattering within the monochromator's housing. of Czerny–Turner type, different wavelength components are spatially separated with a diffraction grating, and only a narrow range of wavelength components is transmitted through the exit slit. Examples of Applicationsīlack coatings can be applied to a variety of substances, such as metals, polymers, glasses, semiconductors and ceramics. However, there are also coatings which are black for visible light while exhibiting a low emissivity (thus also low absorption) in the infrared. Here, a low reflectance in the infrared is usually of highest importance. Therefore, black coatings may also be needed where a maximum of thermal radiation from some parts is required. a high absorptance, is associated with strong thermal emission, i.e., a high emissivity. Their main application is to suppress stray light in optical systems. Some of them also exhibit strong absorption in the infrared or in the ultraviolet. There are various types of coatings which are strongly absorbing light so that they appear black. How to cite the article suggest additional literature German: schwarze oder absorbierende BeschichtungenĬategories: general optics, optical materials ![]() ![]() ![]() Definition: coatings with strong light absorption ![]()
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