1. Basic dimensions parameters

Diameter (D): The diameter of a spherical lens determines its size and is typically measured in millimeters (mm). Spherical lenses of different diameters are suitable for various application scenarios.

Thickness: For certain types of spherical lenses (such as compound spherical lenses with diaphragms), thickness is also an important parameter, which can affect the focal length and imaging quality of the lens.

2. Focal length parameters

Effective focal length (EFL, effective focal length): The effective focal length is an important parameter of a spherical lens, which determines the imaging characteristics and magnification of the lens. The calculation formula for the effective focal length may vary depending on the material, shape, and structure of the lens.

For example, for a single spherical lens, its effective focal length can be calculated using a specific formula that takes into account the diameter (D) of the lens and the refractive index (n) of the material.

Back focal length (BFL, back focal length): The back focal length is the difference between the effective focal length and half of the lens diameter. It determines the distance from the rear focus of the lens to the rear surface of the lens. In some applications, the size of the back focal length is crucial for determining the layout and performance of the imaging system.

3. Material parameters

Refractive index (n): The refractive index is an important optical property of the lens material, which determines the speed and direction of light propagation in the lens. Different materials have different refractive indices, so this affects the imaging quality and focal length of the lens. For example, the refractive index of common K9 glass is 1.5163.

Abbe number (Vd): The Abbe number is a physical quantity that measures the dispersion of lens materials. It determines the imaging quality of the lens under different wavelengths of light.

The higher the Abbe number, the lower the dispersion of the lens and the better the imaging quality. Common optical glasses are classified according to their Abbe numbers. Glass with an Abbe number ≥50 is crown glass (denoted by “K”), and glass with an Abbe number <50 is flint glass (denoted by “F”).

4. Other parameters

Sphericity: For spherical lenses, the sphericity of their surfaces is an important parameter that determines the imaging quality and consistency of the lenses. The higher the degree of sphericity, the better the imaging quality of the lenses.

Surface finish: The surface finish of the lenses also affects their imaging quality. Lenses with a higher surface finish have fewer surface defects and thus better imaging quality.