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Joseph I. Pascal, M.D.

Arch Ophthal. 1939;22(3):448-449.

	Since this article does not have an abstract, we have provided the first 150 words of the full text PDF and any section headings.

Every optical system has six important points, called cardinal points, associated with, and inherent in, the system. These are two principal focal points, F₁ and F₂, two principal points, P₁ and P₂, and two nodal points, N₁ and N₂. In the simplest optical system, such as a curved spherical mirror, these six cardinal points are reduced to three, as each pair of points coincide; i. e., F₁ coincides with F₂, P₁ with P₂ and N₁ with N₂. In a slightly more complex optical system, such as a single refracting surface, the six cardinal points are reduced to four, as two pairs of points coincide, i. e., P₁ with P₂ and N₁ with N₂. In a lens situated in air, the six cardinal points also are reduced to four but by a different kind of coincidence. . . . [Full Text PDF of this Article]

Author Affiliations
New York

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