Japanese 7.5 x 60 mm with 45 Degree Inclined Ocular
The 7.5 x 60 mm Japanese military binoculars were built with a 45 degree Schmidt roof design in combination with a rhomboid whose housing may be rotated to adjust interpupillary distance, or IPD. IPD is the distance between the pupils of your eyes measured from center to center when your eyes are focused on infinity. The eyepiece is an altered version of the classic five-element Erfle design with apparent field of 60 degrees. The real field of this design is 8 degrees, and the prism system and housings of this instrument are identical to those used in the Japanese 20 x 120 mm model with 45 degree inclined oculars.