Optical lenses can be categorized into three main classifications: spherical, aspherical, and cylindrical. Each of the three types offers unique characteristics that make it suitable for different use cases.
The following article focuses on spherical and aspherical lenses, outlining their distinct properties, key benefits, and typical applications.
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 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:
- Smaller number of elements required in an optical assembly
- Reduced effects of spherical aberration, distortion, and marginal astigmatism
- Sharper focusing
- Larger aperture size
- Improved 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:
- Fluorescence 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)
- Cameras and laser-based ophthalmic tools for vision correction: used by trained clinicians and surgeons to diagnose and treat eye diseases and correct vision
- Semiconductor wafer inspection tools: used by computer chip engineers to map defects and probe cards
- Industrial laser machine tools: used by manufacturing companies to create and inspect products before, during, and after manufacturing
- Night vision optics: used by frontline marines and soldiers operating under cover of darkness on critical defense missions
Optical Solutions at JML Optical
At JML Optical, we have designed and manufactured high-quality custom optical solutions for over 40 years. Our team has the knowledge and skills to develop and deliver spherical, plano, and aspherical glass lenses and complex lens assemblies suitable for some of the most demanding customer applications. In addition to our fabrication capabilities, we also offer the following services:
- Design assistance
- Manufacturability assistance and design performance
- Lens assembly optimization