A spherical lens is a spherical lens whose optical function is to make parallel rays form a focal point F. In eyeglass optics, there are thin lenses and thick lenses.

A spherical lens is the reflecting surface of a part of a sphere. The surface may be convex or concave. A concave spherical lens has an inward convex reflecting surface and reflects light inward. A convex spherical lens has a reflective surface raised toward the light source and reflects light outward. The substrate materials of the spherical lens include various optical glass, ultraviolet fused quartz, infrared fused quartz, calcium fluoride (CaF2), magnesium fluoride (MgF2), zinc selenide (ZnSe), germanium (Ge), silicon (Si), etc., and provide various optical films such as anti-reflective film, highly reflective film, beam splitting film, metal film, etc. The wideband antireflective film can be applied to ultraviolet, visible, near-infrared, and mid-infrared bands.

A lens is said to be thin if its center is so thin that its optical properties are independent of its shape and form, that is, whether the shape of a convex lens is biconvex, planoconvex, or concave-convex; No matter the shape of concave lens is double concave, flat-concave or convex-concave, the influence of the central thickness on its optical properties can be ignored, and we can call it a thin lens. In this case, the convex lens is represented by a double arrow facing each other, while the concave lens is represented by a double arrow facing each other.

(1) Spherical lens classification

Concave mirror: A spherical mirror with the inner side of the spherical surface as a reflecting surface is called a concave mirror. Convex lenses can be divided into three forms: double convex, flat-convex, and concave-convex.

Convex mirror: A spherical mirror with the outside of the spherical surface as the reflecting surface is called a convex mirror. Concave lenses can be divided into three forms: double concave, flat-concave, and convex concave.

(2) Optical properties of spherical lenses

1. Spherical lenses have the ability to bend and focus light.

2. The spherical lens bends rays equally at all meridians.

3. Top focus: A unit of measure used to describe the flexion capacity of a lens to light rays. It is numerically equal to the inverse of the focal length of the lens. Namely, F=1/ F where F is the focal length and F is the top focal degree. The unit of top focal degree is diopter and the symbol is “D”.

4. Specular degree of the spherical lens; A spherical lens has two interfaces, each of which has the ability to bend the incoming light rays. The ability of each interface to bend the light rays is expressed by the top focal degree, which is called the surface mirror degree.

5. Top focal degree of spherical lens for an eye; The top focal degree of a spherical lens is equal to the sum of the two diameters of the sphere, namely F=F1+F2

(F is the top focal degree of the spherical lens, F1 is the mirror degree of the front surface of the spherical lens, and F2 is the mirror degree of the rear surface of the spherical lens)

6. Visual image shift of spherical lens; Put -3.00D in front of your eyes, observe the distant target through the mirror, and slowly move the lens up and down in parallel, the target will also move up and down: when the lens is moved left and right in parallel, the target will also move left and right, and the movement of the target is consistent with the translation direction of the mirror, which is called forward movement. Put +1.00D in front of your eyes, observe the distant target through the mirror, and slowly move the lens up and down in parallel, it will be found that the target moves against the direction of the mirror, which is called inverse motion.