File:Characteristics of striæ in optical glass (1920) (14595096319).jpg

Identifier: characteristicso16759unse (find matches)
Title: Characteristics of striæ in optical glass
Year: 1920 (1920s)
Authors:
Subjects:
Publisher: National Bureau of Standards
Contributing Library: NIST Research Library
Digitizing Sponsor: NIST Research Library

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Fig. 15.—(a) Without glass; (6, c) viewed flatwise through rolled windowplate (same as Fig. 10); (d, e,f) edgewise through same plate good so far as the unaided eye could distinguish—far better thanthose obtained with many binoculars in which the amount ofstriae present was negligible. A lot of prisms and lenses, rejected after polishing, were tiu-nedover to this Bureau by the optical shop annex of the Naval GunFactory at Rochester. These prisms were discarded on account Smith, Bennett,!Merritt J Stri(B in Optical Glass 85 of striae, bubbles, and scratches, the polish and workmanship inall cases being above criticism. All of the prisms shown in Fig. 3were taken from this lot of rejects, the prints to the left beingshadowgraphs of the striae in the prisms. Dr. Zwillinger, of theoptical shop annex, loaned the authors a testing frame into whichthe different parts of a biftocular could be fitted at pleasure. Byinserting single, discarded parts in an otherwise first-class optical
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■Stri(2 in large photographic lens train the authors demonstrated visually to their own satifactionthat only relatively heavy striae were an appreciable drawback tothe performance of the prisms and lenses tested. In fact, of thelot of six prisms shown only No. i was really very bad in its per-formance, and the striae in the lens of Fig. 8 seemed to exert nonoticeable effect upon the definition. To obtain a record of the amount of light scattered by the striaein these prisms, each one was inserted in a train otherwise good, 86 Scientific Papers of the Bureau of Standards (voi. i6 and then this was used as a part of an optical-projection systemto project a magnified image of an artificial star—or, perhaps, inthis case it would be more correct to say an artificial planet, forthe pinhole was about 0.8 mm in diameter—on a photographicplate. Because of the fact that the binoculars are chromatically cor-rected for visual impression rather than for photographic record,

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