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BINOCULAR INSTRUMENT
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See also:BINOCULAR See also:INSTRUMENT , or briefly BINOCULAR,4 an apparatus through which See also:objects are viewed with both eyes. In this See also:article only those See also:instruments will be considered in which solid objects or objects in space are viewed; reference should be made to the article See also:STEREOSCOPE for the instruments in which See also:plane representations are offered to both eyes. The natural See also:vision is such that different central projections of the objects are communicated to both eyes; the difference of the two See also:perspective representations arises from the fact that the See also:projection centres are laterally separated by an See also:interval about equal to the distance between the eyes (the inter-pupillary distance). Binocular instruments should aid the natural spatial or stereoscopic vision, or make it possible if the eyes fail. If the objects be so far
4 The See also:term binocular (from the See also:Lat. bini, two at a See also:time, and oculi, eyes) was originally an See also:adjective used to describe things adapted for the simultaneous use of both eyes, as in " binocular vision," " a binocular See also:telescope or See also:microscope "; now " a binocular " is used as a noun, meaning a binocular microscope, a See also: I). After these discoveries the subject received no more See also:attention until the 19th See also:century; no improvements of these instruments are recorded in the literature of the second See also:half of the 18th century. The re-invention of the Dutch binocular telescope apparently dates from 1823, and is to be assigned to the Viennese optician, Johann Fried- See also:rich Voigtlander (1779–1859); but the See also:credit of having placed these instruments on the See also:market probably belongs to J. P. Lemiere in See also:Paris, who, in 1825, took out a See also:French patent for an improve- ment of the Dutch double telescope. Lemiere's instruments were furnished with a See also:common focusing arrangement, and the adapting to the inter-pupillary distance was effected by turning the two parallel telescopes See also:round their common See also:axis. The development of this instrument was studied by opticians for the See also:remainder of the first half of the 19th century; the last improvement apparently was made by P. G. Bardou in 1854, and by H. See also:Helmholtz in 1857 when he described the telestereoscope (fig. 2) with telescopic magnification. By utilizing the telescope with See also:prism-See also:inversion, devised in 1851 by Ignazio Porro (1795–1875), A. A. See also:Boulanger succeeded in producing a binocular of an entirely new type in 18J9 (fig. 3). But he overlooked the possibility of increasing the distance between the objectives; Camille Nachet introduced this improvement in 1875, but, his instruments did not meet with much popularity. This was probably due to the fact that, at this time,
the manufacture of the glass for the prisms was too difficult; this was overcome by E. See also:Abbe, after the See also:founding of the glass-See also:works at See also:Jena, who effected, independently of his predecessors, the wider separation of the ob-
jectives (fig. 4), and increased it in the telestereoscope (fig. 5), or See also:relief telescope, in a manner nearly approaching to Helmholtz's proposal.
The first binocular microscope was invented by the previously
mentioned See also:Father Micro- Cherubin whose in-
See also:scope.
strument consisted of two inverting systems, and consequently gave a totally wrong impression of See also:depth, i.e. depressions appeared as elevations, and See also:vice versa, or, as we must say after See also: In 1853 the See also:American J. L. Riddell (1807–1867) devised his binocular microscope, which contained the essentials of Wheatstone's pseudoscope. F. H. Wenham, another constructor, did not at first succeed in avoiding the pseudoscopic effect, but, by the application of refracting dividing prisms, he subsequently arrived at orthoscopic representations and continued the development of the different methods for producing micro-photographic stereograms; this was effected in the first See also:case by FIG. 4. placing a See also:diaphragm over one half of the See also:objective for each exposure, and in the second case by a suitable direction of the See also:illuminating See also:pencil (fig. 6). Of greater benefit, how-ever, for stimulating See also:interest in binocular microscopes, was his invention of reflecting dividing prisms (fig. 7). Other experiments, begun by See also:Powell and Lealand, and See also:developed with' greater skill by Wenham, were concerned with the binocular vision of identical images. Such an impression could not possibly be stereoscopic, and these experiments led to the construction of a non-stereoscopic binocular micro- scope. Of the other workers in this field mention may be made 1 The first See also:part appeared in 1838. of See also:Alfred Nachet, who in 1853, and subsequently in 1863, brought forward two forms of binocular microscope. The earliest stages of the development of the binocular microscope had been always confined to those instruments with one objective, in the immediate neighbourhood of which the systems for dividing the pencil were placed. At a later date attempts were made to See also:separate the two halves of the objective by modifying the eye-piece; this led to the construction of stereoscopic eye-pieces, initiated by R. B. Tolles, E. Abbe and A. Prazmowski. Of See also:special importance is the See also:work of Abbe; although, as he himself has stated, his methods accidentally led to the Wenham See also:system, he certainly was far above his predecessors in his theoretical treatment of the problem, and in the perspicuity and clearness of his explanation. To him is also due the re-See also:establishment of the instruments, which Wenham had abandoned by See also:reason of too great technical difficulties (fig. 8). The newest See also:form of the binocular microscope is very similar to the See also:oldest form in which two completely separated tubes were employed. The inventor, H. S. See also:Greenough, employs two systems for setting up the See also:image, in order to avoid the pseudoscopic effect. After experiments in the Zeiss works, the erecting of Porro's prisms simultaneously permitted a convenient See also:adaptation to the eye-distance of the observer. The first binocular magnifying glass or See also:simple microscope (See also:German, Lupe) was devised by J. L. Riddell in 1853; in this instrument (fig. 9) the pencil of See also:light is transmitted simple to the eyes by means of two pairs of parallel mirrors. mtcro- Of the many different improvements mention may scope. be made of A. Nachet's. H. Westien made use of two See also:Chevalier-Brucke's simple microscopes with their See also:long working distances in order to form an instrument in which the curvature of the image was not entirely avoided. Mention may also be made of the binoculars of K. Fritzsch (formerly Prokesch) and E. Berger. Binocular Instruments for Range-finding.--For measur- See also:ing purposes binocular tele- scopes with parallel axes are the only types employed. The measurement is effected by adjoin- ing to the space or interval to be measured some means of measure- ment defined; for example, by a fixed See also:scale which extends into the space, or by a movable point (Wandermarke). This instru- ment shows a transition to the stereoscope, inasmuch as the scale or means of measurement is not directly observed, but to each eye a plane See also:representation is offered, just as in the stereoscope; the space to be measured, on the other See also:hand, is portrayed in exactly the same way as in the double telescope. The method for superposing the two spaces on one another was deduced by See also:Sir See also:David See also:Brewster in 1856, but he does not appear to have dealt with the problem of range-finding. The problem was attacked in 1861 by A. Rollet; later, in 1866, E. See also:Mach published a promising See also:idea, and finally—independently of the researches of his predecessors—Hektor de Grousilliers, in See also:partnership with the Zeiss See also:firm (E. Abbe and C. Pulfrich), constructed the first stereoscopic range-finder suitable for See also:practical use. (O. Additional information and CommentsThere are no comments yet for this article.
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