s, etc.—These are objectives or other pieces of opticalapparatus (oculars, illuminators, etc.), in which the spherical distortion is whollyor nearly eliminated, and the curvatures are so made that the central and marginalparts of the objective focus rays at the same point or level. Such pieces of… … CH. /.] MICROSCOPE AND ACCESSORIES. 13 fluoride, Fluorite, or Fluor spar). The name, Apochromatic, is used to indicatethe higher kind of achromatism in which rays of three spectral colors are com-bined at one focus, instead of rays of two colors, as in the ordinary achromaticobjectives. At the…
Microscopy
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