Spherical aberrations are one of the most common forms of optical aberration. Spherical aberrations are the result of a ray height dependent effective focal length. Rays farther from the optical axis (peripheral rays) will focus to a different focal distance than rays closer to the optical axis (paraxial rays). This distribution of focal distances with varying ray height introduces a 'focal region' instead of a single focal point for all rays. Spherical lenses when used in high numerical aperture (NA) optical systems or in systems with larger focal ratios can introduce more spherical aberrations. Spherical aberrations can limit the ability to focus a beam, resulting in larger focused spot sizes. In imaging applications, spherical aberrations can reduce image quality and introduce blur in the outer regions of the image. #optics #STEM #science #OpticsExplained #photonics
