Spherical VS. Aspheric Lenses: How They're Used in Imaging Applications

Spherical Lenses

Spherical lenses - also sometimes referred to as singlets - are optical lenses that feature a spherical surface with a radius of curvature that is consistent across the entire lens. They are constructed such that the light entering them diverges or converges, depending on the lens design. Concave spherical lenses have a negative focal length that causes incident light to diverge (creating a virtual image). In contrast, convex spherical lenses have a positive focal length that causes incident light to converge (creating real and virtual images). The real images formed are highly focused, while the virtual images formed are highly magnified.

The main advantages of using spherical lenses in optical systems are their simpler surface design and lower manufacturing cost. These benefits make them suitable for various imaging applications in a diverse set of markets. Plano-convex lenses are often used in light collimation and monochromatic illumination operations that require infinite or near-infinite conjugate imaging properties. Plano-concave lenses are suitable for optical applications requiring the projection of light, the expansion of the light beam, or the expansion of the system's focal length.

Aspherical Lenses

Aspherical lenses are optical lenses that feature a non-spherical, non-cylindrical shape that is rotationally symmetric. Unlike spherical lenses, they have a radius of curvature that varies from the center to the edge of the lens.

While the design and manufacture of aspherical lenses can be challenging, when constructed correctly, they can offer greater optical functionality than a comparable spherical lens. Some of the key benefits of using an aspherical lens in an optical application are:

ㆍSmaller number of elements required in an optical assembly

ㆍReduced effects of spherical aberration, distortion, and marginal astigmatism

ㆍSharper focusing

ㆍLarger aperture size

ㆍImproved light focusing and collection efficiency

For the above reasons, aspherical lenses are used in many imaging applications. They are commonly found in microscope imaging objectives and other image lens assemblies in life science instruments, semiconductor wafer inspection tools, medical devices, and defense and aerospace night vision imaging optics that rely on precision optical components.

Use in Imaging Applications

Both spherical and aspherical lenses find application in a wide range of imaging applications in a variety of end markets. They enable engineers, researchers, and scientists to use equipment - such as advanced microscopes, laser scanners, and other imaging devices - to make very precise measurements.

Some examples of the applications where spherical and aspheric lenses are found include:

ㆍFluorescence microscope platforms: used by researchers to facilitate the identification and examination of specific sections of a specimen (e.g., decoding DNA sequences and imaging individual cells and tissue samples)

ㆍCameras and laser-based ophthalmic tools for vision correction: used by trained clinicians and surgeons to diagnose and treat eye diseases and correct vision

ㆍSemiconductor wafer inspection tools: used by computer chip engineers to map defects and probe cards

ㆍIndustrial laser machine tools: used by manufacturing companies to create and inspect products before, during, and after manufacturing

ㆍNight vision optics: used by frontline marines and soldiers operating under cover of darkness on critical defense missions

Optical Solutions At Oplens

At Oplens, we have designed and manufactured high-quality custom optical solutions for over 16 years. Our team has the knowledge and skills to develop and deliver Ultraviolet (UV) Lens, Infrared (IR) Lens, and Large-diameter Lens for some of the most demanding customer applications.

For additional information about our spherical and aspherical lens offerings, contact us today. To speak with one of our experts about an upcoming optical project, request a quote.