One way to reduce the cost of OPTICS is to use resin lenses. What is the difference between the two compared to a optics with glass lenses?
If you are careful, you'll 'find that the lenses of the telescope have colored reflections, which is the effect of the coated lenses. After the coating of the lens, the telescope will make the field of view brighter and clearer, next I will explain the difference between resin and glass lenses from the perspective of lens coating.
The role of lens coatings are two:
1, to increase the light transmission of the lens, the raw material for the manufacture of lenses is glass, although glass is transparent, it also has a light-blocking effect, experiments have learned that each piece of glass light-blocking rate of about 8%, the lens is composed of multiple pieces of glass, ferry on a layer of film (oxidation picks) can greatly improve the light transmission, reduce the loss of light transmission;
2, to prevent stray light interference image, improve image clarity.
There are two main types of lens coatings: one is anti-reflective film, that is, by coating the front surface of the lens with multiple layers of transparent materials of different refractive indices and thicknesses, using the principle of light interference to reduce the excess reflected light on the surface of the lens. The anti-reflective coating increases the permeability of the lenses to light, and the user feels that the glare is reduced and the vision is clearer and brighter. Another type of coating is hardening, which is mainly used for resin lenses. It is usually applied to the front surface of the lens, making the resin lens more resistant to abrasion and enhancing light permeability.
When cleaning the hard coated lenses, the user should first wash the front and back surfaces of the lenses with detergent and then dry them with a clean soft cloth, taking care not to wipe them when they are dry.
Resin lenses can be coated with anti-reflective film or hard coated, while glass lenses are generally coated with anti-reflective film only.
For resin lenses, whether made of inorganic or organic materials, the friction with dust or grit (silicon oxide) can cause wear of the lenses in daily use, producing scratches on the surface of the lenses. Compared to glass lenses, those made of organic materials are less stiff and more prone to scratching. Through the microscope, we can observe two main types of scratches on the surface of the lens, one is due to the grit, shallow and small, not easily noticeable to the observer; the other is due to the larger grit, deep and rough around, which affects the clarity of the field of view if it is in the center of the lens. That is why most telescopes use lenses with optical glass coating instead of resin lenses.
Therefore, binoculars with resin lenses can reduce the lifetime of the telescope because they are prone to scratches. While telescopes with glass lenses can last more than 5 years, we strongly recommend that you always choose a telescope with glass lenses when buying a telescope.
In the next chapter, we'll continue to introduce the difference between glass lenses and resin lenses regarding the field of view(FOV).
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