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  Surveying Instrument Collection 


Topcon Kogaku Kikai, Japan


Mirror Stereoscope

Serial Number



718 x 260 x 310 mm



This is a mirror stereoscope for the viewing of stereo photographs, including 23 x 23 cm aerial photographs. The image plane separation (a) of the two viewing telescope axes is 250 mm. The interpupillary distance (a') between the two telescopes is adjustable from 56 to 74 mm.

Schwidewsky (1959, see figure above) explains the working principle as follows: "The mirror stereoscope permits the observation of large photographs in that the distance (a) between the axis rays is enlarged by double reflection to a multiple of the interpupillary distance (a'). The figure shows a cross-section with two reflecting prisms at (1), two larger mirrors at (2), and the two component stereophotographs that are to be examined at (3) and (4). The spectacle lenses (5) mounted above the prisms (1) permit accomodation free observation and slightly magnify the images."

Without the attachment of a telescope magnifier unit (3x), the photographs can be viewed with folded legs, if a round lens attached to the 90 degree prisms is rotated into the optical path (field of view 110 mm diameter for both eyes).

With extended legs, the photos can be viewed without the telescope magnifier unit, if the rotatable lenses are removed from, the optical path (field of view 21 x 21 cm on both sides).

With the attached telescope magnifier unit (3x), the image can be focussed. The two lenses attached to the 90 degree prisms must be switched into the ray path. Field of view: 60 mm diameter.

There is one custom made screw that maintains the telescope magnifier unit at the correct distance to the 90 degree prisms. One foot is adjustable in height to allow a stable set-up.

For more details of "plotting with a mirror stereoscope", for example, see pages 158-167 in Schwidewsky, K. (translated by J. Fosberry), 1959. An Outline of Photogrammetry, Sir Isaac Pitman & Sons Ltd, London.

History & comments

Sold by Fielder Instrument Company, 85(?) George Street, Sydney


in wooden box, 470 x 220 x 190 mm, with handle and two lockable snaplocks




Two plastic covers for mirrors. Felt pen markings "12" on the box, on the stereoscope and on the telescope magnifier unit.


Catalogued in September 2013 by JMR. Photo by JMR.

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