6. Examples of corrected optical systems

6.1 Fixed-focus lenses

• Cooke Triplet

  The Cooke triplet (figure 49 ) is the simplest lens with all its Seidel aberrations corrected. The central, divergent component must be highly dispersive to compensate for the dispersion of all convergent elements, and cancel out longitudinal chromatic aberration. If conjugation corresponds to unitary magnification, symmetry eliminates transverse chromatic aberration, coma and distortion. We show that a slight deviation from symmetry...