Image Quality
While astigmatism remains present in the Wright camera, it combines with the mirror's Petzval field curvature to result in a flat best image surface. In effect, the only monochromatic fourth order (wavefront) aberration of the Wright camera is relatively strong astigmatism.
In terms of the wavefront error, the flat-field P–V errors are identical in both, Schmidt and Wright camera, given by W=h2/16DF3 (h being the height in the image plane, D the aperture diameter and F the focal ratio number).
However, while the off-axis error in the flat-field Schmidt results from defocus, in the Wright camera it is caused by astigmatism. Since the RMS/P–V error ratio is smaller by a factor of 0.51/2 for astigmatism, the actual quality flat-field radius in the latter is larger by a factor of 1.4.
On the other hand, (curved) image surface of the Schmidt is practically free from off-axis aberrations, hence clearly superior in quality to a best (flat) field in the Wright camera. Also, since the Wright camera requires twice as strong corrector to cancel spherical aberration of the mirror, its chromatic error is double that in a comparable Schmidt camera.
Both, more strongly aspherized corrector and, especially, strongly aspherized fast mirror (into a rather unpopular type of aspheric shape) of the Wright are a fabrication disadvantage. On the plus side, the Wright camera is only about half as long as an equivalent diameter Schmidt. Also, since the corrector in Wright's arrangement nearly coincides with the image plane, it can support the film/detector assembly, clearing the optical path from supporting vanes.
Read more about this topic: Wright Camera
Famous quotes containing the words image and/or quality:
“It is indeed typical that you Earth people refuse to believe in the superiority of any world but your own. Children looking into a magnifying glass, imagining the image you see is the image of your true size.”
—Franklin Coen. Joseph Newman. The Monitor (Douglas Spencer)
“This fellow is wise enough to play the fool,
And to do that well craves a kind of wit.
He must observe their mood on whom he jests,
The quality of persons, and the time,
Not, like the haggard, check at every feather
That comes before his eye. This is a practice
As full of labor as a wise man’s art.”
—William Shakespeare (1564–1616)