l82 



wells: formulae for meridian rays 



Fig. I. — ^NoTATioN. 

 Symbols referring to the object-space are unprinied, to the image-space are primed, 

 the image-space for the k'th surface becoming the object-space for the (k -f i)'th 

 surface. 



k'th refracting surface. 



Hk = index of refraction, object-space, 

 n^ = index of refraction, image-space. 

 vertex distances, 

 i'k = VkCk = radius of curvature. 



Uk = VrOk = object distance. 



VkO^ = image distance. 



Ck = OkCk = object distance (to center). 

 C„ = O^Ck = image distance (to center). 



ds = VkVk + 1 = interval between vertices. 

 dcK = CnCK-f 1 = interval between centers. 



slope angles. 



slope angle of normal at incidence point. 



"K = BkOkVk = slope angle of incident ray. 

 a = BkO'Vk = slope angle of refracted ray. 



A 



Ok = OrBkCk = angle of incidence. 



e' = O' BkCk = angle of refraction. 



hg = DkBk = incidence height (measured positively upward). 



identities. 





