Know About Optical Filter

An optical filter is a passive device that allows the transmission of light of a specific wavelength or set of wavelengths. There are two types of filters, each of which works on a different principle: absorption filters and dichroic filters.

What is the Optical Filter?

An optical filter is a passive device that allows the transmission of light of a specific wavelength or set of wavelengths. There are two types of filters, each of which works on a different principle: absorption filters and dichroic filters.
Absorptive filters have a coating of different organic and inorganic materials that absorb specific wavelengths of light, thus allowing the desired wavelength to pass through. Because they absorb light energy, these filters operate at elevated temperatures.
They are simple filters that can be added to plastic to make filters that cost less than glass filters. The operation of these filters does not depend on the angle of incident light but on the properties of the materials that make up the filter. Therefore, they are good filters when reflected light of unwanted wavelengths causes noise in the optical signal.

Dichroic filters work on a more complex principle. They consist of a series of optical coatings with precise thicknesses that are designed to reflect unwanted wavelengths and transmit the desired wavelength range. This is accomplished by causing the desired wavelengths to interfere constructively on the transmitting side of the filter, while other wavelengths interfere on the reflecting side of the filter.

Application of Optical Filters

Filters are very important in the application of laser experiments. Laser safety glasses are optical filters that are worn to protect your eyes from laser radiation. They typically filter out a small percentage of the wavelengths, allowing you to see your surroundings when the laser is turned on for optical experiments. It is important to wear safety glasses that are appropriate for the wavelength of the laser being used.

Optical filters are also important as optical components in laser experiments. For example, when measuring the photoluminescence (PL) of a material, all the light from the laser-excited spot is coupled into an optical fiber and measured in a spectrometer. The intensity of the laser is so high that, depending on the wavelength of the photoluminescence, the laser can overcome the intensity of the signal. Using a filter of the laser wavelength somewhere between the film and the lens that collects the light from the film reduces or eliminates the laser peaks so that we can see the photoluminescence peaks.

Filters can be used to "diminish or enhance an image". Filters can also reflect unique wavelengths, split an image into two identical images, or transmit an image.

Filters made of glass are usually coated on the surface of optical glass to interfere with the light transmission properties of the lens, thereby transmitting or blocking specific wavelengths. The coating method is usually designed to pass dielectric film materials or metal film materials through high temperature through film system design. Evaporation and sublimation to the lens surface. Its high-temperature resistance is much higher than that of acrylic material, and its light transmittance is relatively higher. The most important thing is that it is more selective to light. It can be made according to the parameters required by customers; the wavelength range is also wider, from ultraviolet to visible light. , near-infrared, and mid-far infrared can be produced. Glass filters are usually used in intelligent driving, biomedical treatment, fluorescence analysis, biometric identification, security monitoring, lidar, beauty instruments, smart homes, anti-fatigue monitoring systems, aerospace, machine vision, drones, and 3D scanning. , photography, industrial cameras, industrial automation, lasers, sensors, filters, laser welding, laser lights, night vision devices, etc. applied to the field of optics.

RZ Optics Co., Ltd. is a manufacturer of optical components, and main products including spherical lenses, domes, optical windows, optical filters, mirrors, etc. The materials we use for our products are optical glass N-BK7, H-K9L, fused silica, sapphire, silicon, and so on. Our products are widely used in various fields. We also could provide OEM service.

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