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LOST RADIATION
Fig. 13 Upper diagram: Petzval's Katadioptric Condenser. Lower Diagram: Adaptation of an automobile headlight to a M.P. condenser
In case of a single condenser the corresponding figures will be 1.58 and 1.53.
The question may now be raised what, is the best result obtainable at the present state of the art and in which directions may improvements be made.
We found the following factors of influence upon the efficiency of the condenser system:
(i) Radiation from the source not intercepted by the optical system and, therefore, lost;
(2) Spherical aberration of the condenser;
(3) Chromatic aberration of the condenser;
(4) Diaphragm action (I) of the aperture plate on account of the rectangular shape of the opening;
(5) Diaphragm action (II) of the aperture plate on account of its location when the light source is not point-shaped;
(6) Absorption and reflection.
Of these the influence of (3) and (6) can be shortly dealt with. Chromatic aberration causes no loss of light in a properly designed system, while the loss by absorption and reflection which amounts to from 12% to 15% in single lens condensers and to 20% to 27% in doublets is absolutely unavoidable.
The loss due to the rectangular shape of the stencil, diaphragm action (I), cannot be avoided even by employing an optically perfect condenser and a point-shaped source and so there remain for consideration only the utilization of the radiation not intercepted by the condenser lens, the spherical aberration and the diaphragm action (II) of the aperture plate when the source is not point-shaped.
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