What is an aspherical lenses and how does it work? Canon shared a video explaining the challenges engineers face when designing lenses and how Canon solved them with aspherical lense.

Canon celebrated the 50th anniversary its aspherical lenses technology with a new exhibit in their virtual Canon Camera Museum. You will find videos and articles on fluorite and aspherical lenses, as well as interviews with project staff who talk about the development of the EOS lenses and EF lenses.

Canon claims that aspherical lenses are well-known for correcting various lens aberrations in optical design and improving overall image quality. Aspherical elements are now commonplace and can be found in lenses from entry-level to professional-level optics made by a variety of manufacturers.

Here are two photos that illustrate this: one shot with a spherical camera and one with an aspherical.

Canon explained that traditional lenses have a curving surface that looks like a slice from a sphere. This is why they are called “spherical”. However, there are some issues with this design.

Spherical aberration on a spherical lens element
An aspherical lens element ensures light rays converge at the same position.

Canon explains that light rays traveling through the center of a cylindrical element must travel longer distances to reach the image plane than rays coming from its peripheries. This causes light rays to converge at different locations. This causes a phenomenon called spherical aberration. Point light sources are rendered as points instead of blurred.

Also, spherical lenses can also be affected by distortion.

Although aspherical lens were proven to fix these problems, the manufacturing of such lenses was difficult for many years. Canon claims that it was difficult to achieve the precise curvature control required to maintain submicron levels (1/10,000th millimeter). Aspherical lenses were so difficult to create that they were called “dream lenses.”

Canon released an interchangeable lens that was compatible with SLR cameras over 50 years ago, in 1971. It included aspherical lenses elements. Canon has improved its processing techniques and precision technology over the years and is proud to have been a part of the continuous improvement in image quality with aspherical lenses.

The digital Canon Camera Museum has a special exhibition that provides more information on aspherical lenses, and Canon’s use of them over the years. Canon has also included a detailed explanation about fluorite glass. You can access all the videos and information for free.