Function
Schmidt corrector plates work because they are aspheric lenses with spherical aberration that is equal to but opposite of the spherical primary mirror they are placed in front of. It is placed at the center of curvature "C" of the mirror for a pure Schmidt camera and just behind the prime focus for a Schmidt-Cassegrain. The Schmidt corrector is thicker in the middle and the edge. This corrects the light paths so light reflected from the outer part of the mirror and light reflected from the inner portion of the mirror is brought to the same common focus "F". The Schmidt corrector only corrects for spherical aberration. It does not change the focal length of the system.
Read more about this topic: Schmidt Corrector Plate
Famous quotes containing the word function:
“Any translation which intends to perform a transmitting function cannot transmit anything but information—hence, something inessential. This is the hallmark of bad translations.”
—Walter Benjamin (1892–1940)
““... The state’s one function is to give.
The bud must bloom till blowsy blown
Its petals loosen and are strown;
And that’s a fate it can’t evade
Unless ‘twould rather wilt than fade.””
—Robert Frost (1874–1963)
“Literature does not exist in a vacuum. Writers as such have a definite social function exactly proportional to their ability as writers. This is their main use.”
—Ezra Pound (1885–1972)