Tangential plane), and δξ′ is the x-component of aberration (for rays in the x-z Note that δη′ is the y-component of aberration (for rays in the y-z plane, the Given amount of Seidel aberration, by differentiating the wavefront aberration as Simple equations, we can calculate the expected transverse ray aberrations for a Since the Seidel coefficients are related to the wavefront aberrations by some Re-state the fact that the third-order (Seidel) aberrations alone are rarely enough toĬompletely determine the image-forming properties of a system. The above relationships is more a matter of understanding. ![]() ![]() If we need to calculate theĪberration coefficients i w jk we would do this by ray tracing. We should point out, here, that we would hardly ever calculate the aberrationĬoefficients i w k from the Seidel coefficients. (4.14),Ģ w 20 (field curvature) corresponds to 1/4 (S 3 + S 4), but 2 w 22 (astigmatism) However, comparing the above equations with Eq. On axis the wavefront aberration at full aperture is 1/8 S 1 the coma at fullĪperture and full field is 1/2 S 2, and the distortion, expressed as a wavefrontĪberration, is 1/2 S 5. The first five terms in the aberration polynomial can be written in the following We shall now look at how they relate to wavefront, transverse, and We have seen that the Siedel coefficients are fairly simply expressed andĬomputed.
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