Telestereoscope

The development of the binoculars was studied by opticians for the remainder of the first half of the 19th century; the last improvement apparently was made by P.G. Bardou in 1854, and by H. Helmholtz in 1857 when he described the telestereoscope with telescopic magnification.
Source: 1911 EB, Vol. 3, Page 950

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