Spherical lens are used in applications where light will be converged or diverged to form a smaller or bigger image of an object / field of view.

For example on a camera, lenses are used to focus the image of an object which is close or far from the device on a sensor (often a CMOS) of several mm wide. If you are taking a picture of a building, this building image will be shrink at exact proportions from several meters to several mm and transcribe into digital information so you would be ablet to print it.

On the opposite on a microscope the lens will enlarge a very small object to a wider image that can be seen either by raw eye on a eye piece or by a digital sensor.

What are the types of spherical lenses?

Spherical lenses are usually defined by the shape of their two surfaces, which is mix of flat, concave, and convex.

Illustration 1 : a Plano-concave lens (PCV lens), with a flat surface and a spherical concave surface (with radius of curvature of 140mm in this example.

Illustration 2 : a plano-convex lens (PCX lens), with a flat surface on the right and a spherical convex surface on the left with a radius of curvature of 36mm in this example.

Illustration 3:  meniscus lens, thin lens with with a concave spherical surface on the left and a spherical concave surface of the on the right.

Illustration 4: a biconvex lens with two surface of spherical convex surface with a radius of curvature of 80,5mm for both sides in this example.

Illustration 5 : a biconcave lens with two spherical concave surfaces and a center thickness of 1,8mm in this example.

Remarks :

• It is also commun for some lenses to have one face non spherical and an other face spherical.
• In some publications an optical elements with both faces flat is called “flat lens”, we will not use this term and refer to these elements as optical windows as they are not shaped to converge of diverge the light.

How spherical lenses are made?

Normal process for manufacturing of a spherical lens is as below :

1. Cut or mold a preform close to the shape of the lens

2. Grinding of the part to get the right shape
3. Polishing of both optical surfaces on semi-automatic polishing device

4. Centering / edging of the lens to match the lens mechanical axis and optical axis. Lens centering is very important as bad centering will conduct to degradation of optical properties in the optical system after assembly.
5. Cleaning of the lens with ultrasound cleaning machines

6. Coating of the lens, in a coating device

Which optical material can be used for spherical lens?

Most optical material can be used to manufacture a spherical lens, choice of material should be made according to below criteria :

• Refractive index (define how the light rays will react at the interface of air / lens)
• Abbe number  (define the chromatic dispersion)
• Useful wavelength (UV, visible, IR)
• Point of fusion in case the lens is to be molded
• Availability / cost of material.  Some material may be the exact match for your desing, but they may not be available or extremely expensive, therefore a close equivalent maybe considered.
• Usage conditions : for example under extreme condition extra hard material like sapphire may be chosen.

In case no specific constraint, we advise to design lens with N-BK7 ( Schott)/ HK9L (CDGM) optical glass, they are widely available and relatively cheap.

How much does a spherical lens cost?

Spherical lens can be found from a wide range from less than one USD to several thousand USD per lens. Below are the parameters that impact a lens price :

If you are looking for a specific price for your project don’t hesitate to request for a free quotation :

Spherical lens focal length

The focal point of a spherical lens is the point on the optical axis at which an incident bundle of light rays will converge to focus.