Chapter 10The Tessar, Heliar, and Other Compounded Triplets
10.1 The Classic Tessar
Although the Tessar is actually a descendant of the double-meniscus anastigmat form, as described in Chap. 11, it can also be regarded as a modification of the Cooke triplet. As explained in more detail in Sec. 3.5, the substitution of a new achromat doublet for a crown in the triplet is the equivalent of using a high-index, high-V-value glass, and allows the possibility of utilizing the cemented surface of the doublet to control coma and oblique spherical aberration.
In the Tessar rear doublet, the convergent cemented surface:
a. Reduces the zonal spherical
b. Reduces the overcorrected oblique spherical
c. Reduces the “belly” in the astigmatism plots at the ...
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