[citation needed][5] It was at a Physical and Medical Congress in Wageningen in 1933, that Zernike first described his phase contrast technique in microscopy.

His discovery lay at the base of the first phase contrast microscope, built during World War II.

The representation of aberrations was originally based on the theory developed by Ludwig Seidel in the middle of the nineteenth century.

Seidel's representation was based on power series expansions and did not allow a clear separation between various types and orders of aberrations.

Zernike's orthogonal circle polynomials provided a solution to the long-standing problem of the optimum 'balancing' of the various aberrations of an optical instrument.