Aspherical lens
Optimax Systems

Aspheres have one or more optical surfaces of nonconstant curvature, with departure from a spherical surface representing the asphericity of the surface. Aspheres are typically defined by a polynomial equation and reduce the number of elements required in an optical system, reducing system size and weight. Used to manage aberrations inherent to spherical lens systems, aspheres are commonly found in telescopes, camera lenses, and diagnostic instruments.

Specifying Aspheres
Specifying an asphere begins with a custom aspheric form, often fit to the Forbes Q Polynomial (Figure 1) or the Even Aspheric Equation (Figure 2). Describing form involves specifying Vertex Radius (I/C). Conic Constant (k) and applicable Aspheric Coefficients (a). Including a Sag Table (Figure 3) provides reference information to check correct data entry for each manufacturing or metrology tool used.