1. Optical lens manufacturers introduce：Spherical degree:
When light rays pass through a lens with power, they are bent or refracted.
(1) In a lens with positive power, light rays gather or refract toward each other. The point where light rays converge is called the focal point and appears behind the surface of the lens.
(2) In a lens with negative power, light rays diverge or refract away from each other. If these rays are inferred or traced back to the light source, they will converge in front of the lens surface and form a focus lens.
(3) Spherical degree is related to focal length or the distance between lens and focus. More specifically, the spherical degree is the reciprocal of the focal length in meters. The power of lens is represented by diopters (d).
The formula is: degree = 1 / focal length
2. Optical lens manufacturers introduce Astigmatism (cylinder)
Optical power also includes astigmatism power, which is used to correct astigmatism. When light passes through a lens with astigmatism, it will be aggregated or dispersed as if it passes through a lens with astigmatism. But the focus will be along a line rather than a point. Astigmatism is expressed as diopters (d) and is calculated in meters as the mirror direction distance between the lens and the focal line or meridian.
3. Optical lens manufacturers introduce Prismatic:
The prism can be used to correct a person's uncoordinated line of sight, such as strabismus. When the binocular line of sight is not very coordinated into a straight line, the right and left eyes see different images, which will lead to blurring or ghosting. The prism can make the image seen by both eyes into a straight line, so the two eyes will see the image, restore the visual clarity. Prism power, like lens power, is also measured by diopters (d), but in different ways. The prism degree of a D is equivalent to measuring from a meter away from the prism, which shifts the beam of light by one centimeter from its original path.
