Aplanatism is the theoretical state where an optical system produces an image completely free of spherical blurring and off-axis distortion. Achieving this requires precise balancing of lens curvatures and glass types to satisfy the sine condition. It is a primary goal in optical engineering when designing high-fidelity imaging systems and tight laser focusing heads.
Heard on the job
Achieving true aplanatism in this short a focal length will require at least three separate elements.