In one embodiment, an interposer resistant to warping is provided. The cable is assembled with the wiring assembly, and then the wiring assembly is assembled with the connecting head, thereby forming a cable connector. Both an exit pupil of the far-optical device and an entrance pupil of the objective are situated inside the housing. The lock slide as brought into contact with the lower end of the release piece when the holder is pivotally raised from the lowered position is disengaged from the holder by being so deflected for deformation.