The theory of single-axis flexure hinge is applied to a four connecting rods hinge mechanism
which has been used on the sagittally focusing double-crystal monochromator at Shanghai Synchrotron Radiation Facility(SSRF).It outputs limit angular motion with an inputting force.Mechanism system errors were analyzed by elastic deformation of mechanism
and inputting force was analyzed
too.Correctness of the mechanism has been validated in online tests of the focused beam.