Microscope objectives

Claim 1

An apochromatic microscope objective, comprising, when considered in the direction in which a light beam bearing an image of an object being viewed through a microscope employing the objective passes, a first lens assembly, of converging lens elements, a doublet meniscus lens, which is of low positive power and which comprises a positive-power lens element made of glass that is anomalous in the same sense as fluorite and a negativepower lens element made of glass that is anomalous in the opposite sense to fluorite, for reducing aberrations present in the beam as a result of passage through the first lens assembly, and a field-flattening lens assembly which comprises first and second positive-power lens elements made of glass that is anomalous in the same sense as fluorite, first and second negative-power lens elements made of glass that is anomalous in the opposite sense to fluorite, the first negative-power lens element being one component of a biconvex doublet lens of which the said first positive-power lens element is another component, and the second negative-power lens element being biconcave and spaced from the said biconvex doublet lens to impose negative field curvature on the light beam and being one component of a concavo-convex doublet lens of high negative power a further component of which is the said second positive-power lens element, and also comprises a positive-power thick meniscus lens spaced from the said second positive-power lens element, the thick meniscus lens being a doublet lens of which one component is a positive-power meniscus lens element and of which the other component is a negative-power meniscus lens element.