Does anyone know how to read these diagrams?

[chemisttree]

This is a spot diagram and graph of longitudinal abberation (LA) for an apochromatic lens quadruplet. I know that the LA graph should ideally come to a point for all wavelengths and it appears to in the graph but what is the 'y' axis? Is it the direction of focus? What does the 'x' axis mean?

The spot diagram seems to indicate the degree of coma as you move the lens off axis from the incoming ray bundle. I guess small spots are better than larger ones but how small is good?

Any help?

Thanks.

 

[mgb_phys]

In the longitudinal abberation diagram the vertical axis is the radius of the pupil, the horizontal axis is the position of best focus. SInce the aberation is symetrical you only draw one side of the axis.

In the spot diagram the size of the spot is the size an image of a point source will be on you detector. How big/small this has to be depends on the detector, your image requirements and how much money you have!