Jan. 22, 2026
Share:
A spherical lens refers to an optical lens with one or two surfaces shaped as part of a sphere. Each spherical surface can be defined by a central reference point and a fixed radius of curvature. Spherical lenses are the most common type of optical lenses, as they are easier to design, manufacture, and inspect compared with other lens types. This guide introduces how spherical lenses are used and manufactured.
Spherical lenses are used in applications where light needs to be converged or diverged in order to form a smaller or larger image of an object or field of view.
For example, in a camera system, lenses are used to focus the image of an object located at different distances onto an image sensor (often a CMOS sensor) that is only a few millimeters wide. When taking a photo of a building, the large real-world scene is reduced proportionally from several meters to just a few millimeters and converted into digital information that can be stored or printed.
In contrast, in a microscope, spherical lenses are used to magnify extremely small objects into a larger image. This enlarged image can be observed directly by the human eye through an eyepiece or captured by a digital sensor.
Spherical lenses are usually defined by the shape of their two surfaces, which is mix of flat, concave, and convex.
· Plano-Convex Lens
This lens has one flat (plane) surface and one convex surface. It is mainly used to focus parallel light rays to a focal point and is widely applied in imaging systems, laser optics, and collimation applications.
· Plano-Concave Lens
Featuring one flat surface and one concave surface, this lens causes light rays to diverge. It is commonly used in beam expansion systems and for correcting optical aberrations in more complex optical assemblies.
· Bi-Convex (Double Convex) Lens
Both surfaces of this lens are convex. It provides strong converging power and is often used in magnifying glasses, cameras, microscopes, and projectors.
· Bi-Concave (Double Concave) Lens
With two concave surfaces, this lens is a diverging lens. It is typically used in optical instruments to spread light beams and in applications requiring image size reduction.
· Meniscus Lens
This type of lens has one convex surface and one concave surface. Depending on the relative curvature of each surface, it can function as either a converging or diverging lens. Meniscus lenses are frequently used to reduce spherical aberration in optical systems.
Remarks:
It is also common for some lenses to have one non-spherical surface and one spherical surface.
In some publications, an optical element with both surfaces flat is referred to as a “flat lens.” In this guide, we do not use this term and instead refer to such elements as optical windows, as they are not designed to converge or diverge light.
The standard manufacturing process for a spherical lens is as follows:
1. Cut or mold a preform close to the final shape of the lens.
2. Grind the preform to achieve the required spherical geometry.
3. Polish both optical surfaces using semi-automatic polishing equipment.
4. Center and edge the lens to align the mechanical axis with the optical axis. Proper lens centering is critical, as poor centering can lead to degradation of optical performance after system assembly.
5. Clean the lens using ultrasonic cleaning machines to remove residual contaminants.
6. Apply optical coatings to the lens using a coating system.
Most optical materials can be used to manufacture spherical lenses. The choice of material should be based on the following criteria:
· Refractive index, which defines how light rays behave at the air–lens interface
· Abbe number, which defines the level of chromatic dispersion
· Useful wavelength range, such as UV, visible, or infrared
· Melting point, especially if the lens is produced by molding
· Material availability and cost. Some materials may be an ideal match for the design, but may be unavailable or extremely expensive; in such cases, a close equivalent material can be considered
· Operating conditions. For example, under extreme conditions, extra-hard materials such as sapphire may be selected
If there are no specific constraints, we recommend designing lenses using N-BK7 (Schott) or H-K9L (CDGM) optical glass, as these materials are widely available and offer a good balance of optical performance and cost efficiency.
Spherical lenses can be priced across a very wide range, from less than one US dollar to several thousand US dollars per lens. The following parameters have a direct impact on the price of a spherical lens:
| Parameter | Impact on Spherical Lens Cost |
|---|---|
| Raw Material | Lens cost varies significantly with material selection, ranging from cost-effective options such as N-BK7 / H-K9L, B270, fused silica, and plastics to high-value materials including sapphire, germanium, silicon, and other specialized optical materials. |
| Lens Size | Very small lenses (less than 5 mm) and extra-large lenses (greater than 100 mm) are more expensive to manufacture due to increased polishing difficulty and lower production yield. |
| Optical Specifications | Surface accuracy, polishing quality, and cosmetic requirements have a major impact on lens cost. Tighter tolerances and higher surface quality can significantly increase pricing at the component level. |
| Order Quantity | Spherical lenses are typically polished using semi-automatic polishing machines in parallel. As a result, manufacturing time and setup costs are similar for small or medium batch sizes, making higher quantities more cost-effective per unit. |
| Optical Coatings | Optical coatings are applied in batch processes, with each coating run often costing several hundred USD. Higher quantities allow costs to be distributed across more parts, reducing the unit price. Contact us to determine the optimal order quantity for coating efficiency. |
The focal point of a spherical lens is the point on the optical axis at which an incident bundle of light rays converges to focus.
The focal length is the distance between the center of the lens and the focal point. The focal length is a positive value in the case of a converging lens, and negative in the case of a diverging lens.
According to the shape of the surfaces, a spherical lens can be diverging or converging.
The focal length formula (Gaussian formula) is:
1/u + 1/v = 1/f
Where:
u: the distance from the object to the center of the lens
v: the distance from the image to the center of the lens
f: the focal length
For example, with an object at infinity, 1/u tends toward 0, so 1/v = 1/f and therefore v = f. The image is formed at the focal length.
A spherical lens is defined by its optical power, which is inversely related to the focal length. This means that the closer the focal point is to the lens, the higher the optical power of the lens.
P = 1/f
Where P is the optical power and f is the focal length.
The focal length of a spherical lens can be simulated based on the refractive index of the material (Snell’s law), the lens thickness, and the radius of curvature. As the calculation is relatively complex, we recommend using optical simulation software (such as Zemax) to obtain reliable values.
An optical lens usually has two types of tolerancing:
· optical tolerancing
· mechanical tolerancing
Concentricity is directly linked to both. Lens concentricity defines how close the optical center is to the mechanical center. This specification is particularly important in optical systems involving multiple lenses assembled in the same mechanical barrel, as the concentricity error of each lens can accumulate and degrade overall system performance.
Hot Products
