Schmidt Correction Plate

Schmidt correction plate

[′shmit kə′rek·shən ‚plāt]
(optics)
In the Schmidt system, a glass plate with one face a plane and the other aspherical and deviating from a plane in such a way that it bends light, traveling to the system's spherical mirror, so as to correct for spherical aberration and coma. Also known as Schmidt lens.

Schmidt Correction Plate

 

an optical part of the Schmidt telescope designed to compensate for spherical aberration in the telescope’s primary mirror, which has a spherical shape. The Schmidt correction plate, which is mounted at the center of curvature of the primary mirror, is a glass plate one surface of which is flat and the other surface of which has a complex form described by the equation

x = (y4ay2)A3D/512(n – 1)

where A is the relative aperture, D is the diameter of the primary mirror, n is the index of refraction of the plate material, and a is a free parameter on the selection of which the chromatism of the plate depends (minimum chromatism is achieved when a = 1.5).

The Schmidt correction plate introduces in the optical system a spherical aberration equal in magnitude but opposite in sign to the spherical aberration of the primary mirror, thus making the system stigmatic.

N. N. MIKHEL’SON