GB1062710A - Improvements in periscopes - Google Patents

Abstract

1,062,710. Periscopes. B. E. A. M. CUNY. Nov.23, 1954 [Nov.27, 1953], No.33993/54. Heading G2J. A periscope comprising a bottom telescope and a top telescope mounted in the tube of the periscope is characterized in that there is mounted in the tube between the two telescopes at least one inverting afocal system carried by the tube of the periscope in such a position that, under the effect of deformations of the tube due to vibration, the inclination of the optical axis of the afocal system produces an image displacement which compensates for the image displacement due to the relative inclinations of the telescopes. Referring to Fig. 2 the afocal system S is mounted between the bottom telescope L and the top telescope L', and under transverse vibration of the periscope tube the systems S and L' make angles u and i with the axis of the telescope L. It is shown that images remain stationary when the tube vibrates transversely if u (1 + 1/g) = i where g is the magnifying power of the afocal system 2 S. Thus if g = 1, u=i/2 This arrangement also provides partial compensation for longitudinal vibration, but for complete compensation the equation u (1 +1/g ) = i (1 ŒG') must be satisfied, where G' is the magnifying power of the telescope L'. It is possible to satisfy both conditions simultaneously by anamorphosing the system S and introducing a compensating anamorphosis into the system L' as shown in Figs. 9 and 10 where plano-cylindrical lenses (shown crosshatched) are introduced adjacent all the lenses of systems L' and S. Alternatively a compromise may be adopted which reduces but does not eliminate the effect of vibrations in either direction; the condition for this is that u (1 + 1/g ) = i (1 ŒG'/2). If two afocal systems S and S' are used Fig. 5 (not shown) having magnifying powers g and g', and making angles u and u' with the axis, the term u (1 + 1/g) in the equations above should be replaced by u (1 +1/g) + [uu(1 +1/g)] (1+1/g,) Where a single afocal system is used it is necessary to provide inverting means at the eyepiece, e. g. by using a pentagonal prism instead of a triangular prism, to compensate for the inversion produced by the afocal system. The lenses of a single afocal system may be placed in contact with the lenses of telescopes L, L' Fig. 7 (not shown) to form in effect a pair of double lenses which may be replaced by a pair of single lenses each having a power equal to the sum of the power of the two lenses it replaces Fig. 8 (not shown).