Automatic Computation of Spot Diagrams*

The spot diagram is a useful device for estimating the distribution of light over an optical image. A method has been devised in which spot diagrams are obtained by an interpolation process which uses automatic computing and plotting machines. From a single object point a number of rays are traced through an optical system, providing data which determine the coefficients of high-degree polynomials. These polynomials replace the exact ray tracing formulas and are used to calculate the intersections with the image plane of a large number of rays distributed uniformly over the entrance pupil. The coordinates of these rays on the image plane are then fed into a plotting machine which produces the spot diagram.