SPOT is used to evaluate optical instruments or to conceive new ones. Once the system is drawn, it plots the layout of the rays by using the laws of geometrical optics and presents the aspect of the image obtained (on the axis or out of the axis etc...), showing the various aberrations like astigmatism. The image can be seen with several zoom levels. It is superimposed on a screen representing the rate of diffraction for a diameter chosen by you, a circle of 25 µm, or various pixel sizes of commercial CCD cameras. One can also do a Foucault test and get a diagram of the conceived system. Moreover, one can see a graph of the light wave and a graph of the longitudinal aberration.
The optical system can contain up to 20 surfaces including plane surfaces, spherical, parabolic, elliptic, hyperbolic, Schmidt, as well as obstructions and diaphragms. One can conceive all types of instruments used by amateurs: Newton, Cassegrain, Schmidt, Maksutov, using all types of glasses and even instruments with components tilted and shifted like Schiefspiegler. One can define up to 9 types of different glasses for the systems where there is refraction.
The beam can be monochromic or composed of three colors. One can choose the colors (wavelengths) contained in the beam. The image obtained contains the colors of the beam and can show the chromatic aberrations. These chromatic aberrations are also shown in the graph of the longitudinal aberrations. Once the system buit, the software calculates the effective focal distance, geometrical and photographic F/D ratios, as well as the percentage of vignetting.
12 sample designs are supplied with program along with an Help system.
