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Showing papers on "Apochromat published in 1971"


Patent
10 Sep 1971
TL;DR: In this article, a catadioptric system consisting of a solid refractive support which has a portion of smaller diameter projecting from its forward end and internal reflecting surfaces on its opposite end is provided for a photographic objective.
Abstract: A highly corrected compact optical system which has a large telephoto ratio, and which is particularly adapted for a photographic objective, is provided by a catadioptric system consisting of a solid refractive support which has a portion of smaller diameter projecting from its forward end and internal reflecting surfaces on its opposite end. An annular convergent reflecting surface on the rear end of the support reflects incoming light back through the support to a circular divergent reflecting surface which is on the forward end of the forwardly projecting portion and which reflects the light back through the opening at the center of the annular reflecting surface where a series of lenses are suitably provided for increasing the focal length of the system and correcting for some aberrations. Light enters the system through an afocal doublet at the front of the system consisting of a positive lens in front of a negative lens with an air space between; this doublet has an axial aperture through it and is positioned at the front of the support, around the forwardly projecting portion. The positive lens and the support are both of the same material which has substantially the same dispersive power as the material of the negative lens but a much lower (about 17 percent lower) refractive index, so that apochromatism is achieved with rather shallow spherical surfaces, which avoid zonal spherical aberration and the need for aspheric surfaces.

9 citations


Journal ArticleDOI
TL;DR: In this article, the authors treated orthogonal magnetic quadrupole lens systems that could serve as electron microscope objectives and applied the calculus of variations to obtain systems with minimum chromatic aberrations.
Abstract: Orthogonal magnetic quadrupole lens systems that could serve as electron microscope objectives are treated theoretically. After certain constraints are placed on the quadrupole field strength, the calculus of variations is applied to obtain systems with minimum chromatic aberrations. A digital computer was used to calculate optimum orthomorphic and anamorphotic objective type systems. The resulting orthomorphic systems have four lenses while the corresponding anamorphotic systems have three. The chromatic aberration only varies by a factor of 2 in this study indicating its relative insensitivity to choice of lens systems. It is found that the optimum quadrupoles have about 3.6 times as much chromatic aberration as round lenses with comparable fields and dimensions.

7 citations


Book
01 Jan 1971

6 citations


Journal ArticleDOI
TL;DR: In this paper, a far field intensity distribution has been plotted for a circular aperture suffering from spherical aberration and illuminated by quasi-monochromatic partially space-coherent light.
Abstract: Far-field intensity distribution has been plotted for a circular aperture suffering from spherical aberration and illuminated by quasi-monochromatic partially space-coherent light. Gaussian and besinc forms of correlation have been assumed. It is shown that higher values of coefficient of aberration can be tolerated as the value of number of correlation intervals contained in the aperture increases.

4 citations