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How to judge whether the optical glass is good and the filter performance
Optical glass refers to glass that can change the direction of light transmission and can change the relative spectral dispersion of ultraviolet, visible or infrared light. Optical glass in a narrow sense refers to colorless optical glass; optical glass can be used to make lenses, prisms, mirrors and windows in optical instruments. The difference between optical glass and other glasses is that as a component of the optical system, it needs to meet the requirements of optical imaging. Therefore, the judgment of the quality of optical glass also contains some special and stricter indicators.
One. The specific optical constants and the consistency of the optical constants of the same batch of glass
Is each type of optical glass correct? The long rays of the same wave optical lens have regular normative refractive index values, which are used as the basis for optical planners to plan the optical system. Therefore, the optical constants of the optical glass produced by the factory need to be within the certain allowable error range of these values, otherwise the actual imaging quality will not match the expected result during planning and the quality of the optical instrument will be affected.
Second, high degree of transparency
The image brightness of the optical system is proportional to the glass transparency. The transparency of optical glass to light of a certain wavelength is expressed by the light absorption coefficient Kλ. After the light passes through a series of prisms and lenses, some of its energy is lost by the interface reflection of the optical parts and some of its energy is absorbed by the medium (lens design glass) itself. Therefore, with regard to an optical system containing multiple thin lenses, the primary way to increase the transmittance is to reduce the reflection loss of the lens surface, such as coating the surface with an anti-reflection coating.
The filter is made of plastic or glass and added with special dyes. The transmittance of the glass sheet is originally similar to that of air, and all colored light can pass through, so it is transparent, but after dyeing the dye, the molecular structure changes and the refractive index also changes, which changes the passage of certain colored light. For example, a beam of white light passes through a blue filter and emits a beam of blue light, while green light and red light are very few, and most of them are absorbed by the filter.
The laser lens filter is used to attenuate (absorb) certain light wavebands in the light wave or pass through the light wave in a small range accurately selected, and reflect (or absorb) it. Other undesirable bands. By changing the structure of the filter and the optical parameters of the film, various spectral characteristics can be obtained, so that the filter can control, adjust and change the transmission, reflection, polarization or phase state of the light wave.
Optical filters also have crystals, blue glass, and AR coating on the outer surface of the crystals is used to improve light penetration, while blue glass is used to filter infrared. In addition to special filters for black-and-white and color photography, there are also some filters that can be used universally, such as ultraviolet lenses, high-power laser lens group polarizers, neutral gray lenses, soft light lenses, fog lenses, etc.
Because of the obvious performance advantages of the filter, the filter has a great effect. It is widely used in the photography industry and often used as a filter. Let's take a look at some of the knowledge points of the filter used as a filter.
1. Ultraviolet filter is also called UV lens. Its function is to absorb ultraviolet light and a small amount of blue ultraviolet light invisible to human eyes, reduce fog and increase the distance of the mouth. The clarity of the scene. In addition, it also plays a role in protecting the lens from water and dust.
2, the polarizer is also called the polarizer, and the angle needs to be adjusted during use to eliminate polarized light. Polarizers are mainly used as mirrors: eliminate the reflection of non-metallic surfaces; darken the blue sky and deepen its hue; increase the color saturation of the subject; because the polarizer is gray, it also acts as a blocker. It acts as a gray density mirror.
3. The soft lens is also called the soft focus lens. The lens is colorless and transparent, and the surface is corroded with different density and density patterns. It can cause the light beam to scatter, thus Softening effect. Soft lenses are often used when shooting portraits.
4. Special effect filters are some of the normal effects that can change the image, making the screen show a variety of wonderful changes. Such as starlight mirrors, multi-shadow mirrors, hollow mirrors, dynamic mirrors and various magic mirrors.