a Stereoskop is optical equipment, with which one can regard two stereoskopische half-images in such a way that a spatial depth effect is perceptible. By means of mirrors or lenses the two localdifferent half-images are brought in such a way in the field of vision thatduring binocular view a virtual spatial image develops.
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articles close when regarding offers a seeing with two eyes a substantial means to the correctEstimation of the distances. With the right eye we see a close article project on another point of the background than with the left, and this difference becomes all the more importantly, the more near the article moves. We put both eyes upa point removed not too far, then the two eye axles make an angle (aspect) with one another, which becomes all the smaller, the further the article departs.
The size of this angle gives us therefore a measure for the distancethe articles. We differentiate thus when seeing with two eyes clearly, which points before-step more, and which are past more.
In addition it comes still that we close articles with the right eye somewhat more of the one, with the left eye somethingmore from the other side see, and that the straight combination of these somewhat unequal pictures contributes to a total impression substantially to it, the planar opinion of the individual eye to a physical to raise a plastic.
A design implemented on a surfaceor a painting can show in each case the opinion of an individual eye; if one darbietet however each eye that suitably drawn picture of an article, then both pictures will unite to only one total impression.
history and development
the mirror Stereoskop was invented 1832 by Sir Charles Wheatstone in London. Since at this time the photography was not yet invented, hadit the two for representation needed fields compute and draw. Only starting from approximately 1841 it manufactured the necessary pictures on photographic way.
Wheatstone reached the combination of the two fields by its Spiegelstereoskop. The same consists of two right-angledmirrors bent against each other, whose levels stand vertically. The observer looks with the left eye in the left, with the right eye into the right mirror. Laterally of the mirrors two put forwardable Brettchen are attached, which the reverse perspective designsan object take up. Now the jets outgoing from appropriate points of the two designs are reflected by the mirrors in such a way that they seem to come from a only one point behind the mirrors to. Each eye sees thus it associated the pictureto the same places of the area, and the observers therefore receives the impression as if the article daselbst itself physically would find.
Brewster replaced the mirrors of this instrument by lens-like bent prisms, and these Stereoskope were in 19. Century generally in the use. A collecting lens of approximately 18 cm focal length is cut through; the two halvesare against each other arranged, fastened in a rack, with their sharp edges, and at the soil of the same the sheet, which contains the two designs (or photographic pictures), is pushed in. By the application of the pieces of lens it is first possible, the pictures for the eyeto bring more near; then however they work also like prisms, as the lens half before the right eye pushes the picture for something after the left, while the picture appears to the right moved to the design regarded with the left eye somewhat.
Upthis way is brought out complete collapsing of the two pictures. If one ensures by a senkrechte septum present between the pictures that each eye sees only the associated to him, not however for other eye the determined picture, soa further device, around which pictures zubringen for covering, is not at all necessary (Stereoskop of Frick). With concave half lenses the picture intended for the right eye must left, which for the left certain right lie; the pictures of the Brewster Stereoskopstherein with wrong relief would appear.
The meaning of the Stereoskope, which found a so substantial promotion by the photography, is well-known; one uses it, except for maintenance, also for the illustration of trigonometric and stereometrischer theorems and for the study of the lawsbinocular seeing.
Dove demonstrated the emergence of the gloss with the help of the Stereoskops. If the surface is painted of a design blue and the appropriate of the others yellow, then one sees it, if one her in the Stereoskop by a violet glassregarded, metallically shining. White and black lead to one still living adhesives picture of the kind. Also to the distinction of genuine securities of false Dove used the Stereoskop. If one regards the papers with the instrument, which can be compared, then immediately those becomesmallest differences noticeably. The individual indications, which do not agree exact with the original, cover themselves not and apparent are in different levels.
It was already mentioned that the aspect becomes very small, if we both eyes on one fardistant point arrange. Therefore the advantages of seeing with two eyes in the measure, when the articles which can be inspected continue to lie away, decrease and disappear already completely when regarding a landschaftlichen distance. The eyes lie too near,everyone the same a noticeably different picture to present itself could do.Helmholtz therefore „the Telestereoskop “designed, which darbietet itself the Beschauer of two covering pictures of a landscape, directly as if the eye from other several meters would be away.
The instrumentconsists of four plane mirrors, which are bent fastened perpendicularly in a wooden box and under 45° against the longest edges of the same. The light coming from the far object falls on the two expresses large mirrors, becomes right-angled from these upthe two inside reflects and arrived, after it was right-angled reflected also by the small internal mirrors, into the eyes of the observer. Each eye seen in the small mirrors the picture of the landscape in one, reflected by the large mirrorssuch perspective projection, as it appears from the two large mirrors. If one wants to increase the picture, then one can let the rays of light, before they arrive into the eyes, go also still through small telescopes.
- Brewster, The stereoscope (Lond. 1856);
- Ruete, the Stereoskop (2. Aufl., Leipz. 1867);
- Stone houses, over the geometrical construction of the Stereoskopbilder (Graz 1870).
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