Optical projection: a treatise on the use of the lantern in exhibition and scientific demonstration (1906)

Record Details:

Title:
Optical projection: a treatise on the use of the lantern in exhibition and scientific demonstration
Date:
1906
Author:
Wright, Lewis, 1838-1905
Publisher:
London, New York, Bombay : Longmans, Green and Co.
Volume:
Optical projection: a treatise on the use of the lantern in exhibition and scientific demonstration
Leaf #:
00040
Language:
English
Collection:
Books
Format:
Books
Contributor:
University of California Libraries
Sponsor:
MSN
Coordinator:
Media History Digital Library
Description:
Date Added:
July 19, 2022
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THE PARTS OF A LANTERN 2$ which have been already mentioned in § 4. When hand- painted slides only were in use with oil lamps, two simple meniscus lenses combined gave fair results, because there was no detail sharp and colourless enough to manifest optical defects; but photographic slides and diagrams make con- spicuous either chromatic fringes, or distortion of figure. Practically, achromatic lenses only are now used in lanterns. They may be of four kinds. (a) The simple achromatic lens, or lens composed of one convex crown c, corrected by a concave of flint F, usually of the plano-convex total form, as shown at A, fig. 14. TLislens FIG. 14.—Single Achromatic Objectives is employed with its convex surface towards the slide s. If the plane face is turned to the slide, the definition is sharper in the centre of the field, but falls off rapidly at the margin ; and the image is also formed on a hollow curved surface instead of on a plane. By reversing the lens a little is sacri- ficed at the centre, but the picture is better and more uniform over the rest. A lens cannot, however, be made of this con- struction of short focus, say 4J to 7 inches, which will give a good image. It may be well to explain here the principal errors which have to be corrected in the objective. As regards a condenser, it has already been seen that the most noticeable result of spherical aberration is to bring the marginal rays to a shorter