Lens design fundamentals and the role of filtersApexeloptic
Basic principles of lens design: Any lens, new or old, can be distinguished by the term “lens description” to distinguish the number of lenses, the type of glass, the radius of the lens surface, the thickness of the lens, the distance from the lens to the lens, the diameter of each lens, and so on. These are the parameters used to fully describe the lens.
When light from an object passes through a glass surface, the light is refracted, as described by the physics we learn in middle school physics textbooks. The amount of light refracted depends on the refractive index of the glass. If a lens designer knows exactly where and at what Angle light enters the optical lens of the front lens, he can accurately trace the path of light through a system of light theory.
The Angle and the distance can be calculated from the sines and cosines of the trigonometric functions. So with simple plane geometry, the path of light can be traced. We know that the energy emitted by any point source is scattered and has no direction to speak of.
Only part of the energy passes through the lens, and the designers assumed that simple math to calculate the energy passing through the lens (which is seen as a series of individual rays) would allow tracing the path of those rays.
Lens designers first trace a small amount of light from a point on the optical axis. The assumption here is that each object point will form at its corresponding point on the film plane, so that light from the object will be converted into a phase point like an optical lens, and will have the same relative position.
This is GaussianFiction. For those points close to the optical axis, designers can have reason to believe that the Gaussian image is fairly accurate, known as parallel optical optics. Although the formula is fairly simple (at least for experienced designers), IT requires that THESE NUMBERS BE calculated TO 5 to 8 decimal places.
In photography, a filter (protective lens) is used to protect the lens and to filter light. The lens in the camera is the most precious, it is necessary to strengthen the protection, and install the filter, so you can not let some dust erode, of course, it is also very convenient to wipe, do not worry about wiping the lens. Lens in photography focus lens to accept light and people see objects if it is under a strong light to see things suddenly will not adapt, and the eyes will be tired, so wear color filter glasses, feel the eyes more comfortable, that is because the lens blocked a part of the strong ultraviolet light, let the eyes in the case of negative to accept the outside things.
The same goes for the filter on the lens, which can effectively prevent the penetration of strong ultraviolet rays to create the image sharpness, and also prevents some air pollution from eroding the lens. When you use a traditional camera and you shoot with film. Due to the chemical properties of the film, it is particularly sensitive to the ultraviolet rays of sunlight, in the ultraviolet strong place, the use of film to take a picture of blue, and white. The photo quality is seriously affected.
A light filter (guard) in front of the lens can effectively filter out UV rays and improve the clear and aspherical quality of the photo. Alpine photography or high photography, can make the distant scenery clearer, and restore a more real, gorgeous picture.
At that time, the filter became a necessary color filter. Filters can not only improve the image but also protect the lens from dust, fingerprints, and other pollution. So. The filter is always mounted in front of the lens without removal and is the most widely used color filter.
In the digital age, because the core imaging component of the digital machine, the CCD, is no longer as sensitive to ultraviolet light as film, the filter (protective lens) to ultraviolet light filtering function gradually decreased, but damage due to oil stains, fingerprints, scratches lens coating still exists. At this point, the filter provides more protection. Some people worry that adding filters will affect image quality.