Why is the camera lens to be coated? What are the disadvantages?
In order to improve the lens transmittance and image quality, in the modern lens manufacturing process on the lens should be coated. The lens coating is based on the principle of optical interference, in the lens surface coated with a layer of thickness of a quarter of the wavelength of the material (usually fluoride), so that the lens of this wavelength of light reflection to a minimum. Obviously, a layer of film only for a shade work, and multi-layer coating can play a variety of shade. Multilayer coating is usually used in different materials repeatedly coated on the lens surface with different thickness of the film. Multilayer coating can greatly improve the transmittance of the lens. For example, the reflectivity of each surface of the uncoated lens is 5%, the monolayer is reduced to 2% and the multilayer coating can be reduced to 0.2% Can greatly reduce the lens of the lens between the diffuse reflection, thereby enhancing the image contrast and sharpness.
The disadvantage is that the coating layer is more delicate, easy to be bruised.
Not only that, the reflection between the lenses will have a serious impact on the final image quality. The light is penetrated through the lens at the same time by the lens of the surface of the constant reflection of the reflection of some of the light shot, and some are in the lens by the other lens surface reflection, and finally fell on the focal plane, in the image of glare, The contrast of the image, especially the shadow area of ??the contrast decreased, fog up, the sharpness of the image is also greatly reduced.
Knowing from optical knowledge that when light passes through a lens, there is always a portion of the light that is reflected and absorbed, and the amount of reflection and absorption is 5% and 2%, respectively. The lens is made of a lens group, and if the light is reflected and absorbed so much on each lens, the light passes through the lens group to the focal plane is very small, that is, when the light penetrates the lens Was seriously lost.
