Multi-axis interferometer with integrated optical structure and method for manufacturing rhomboid assemblies

An interferometer (300) comprises a polarizing beam-splitter (330) oriented to split an input beam into a reference beam and a measurement beam for a first measurement axis of the interferometer. A polarization-changing element (371) is optically attached to a surface of the polarizing beam-splitter (330), the polarization-changing element (371) being in a path of the reference beam. A reference reflector (381) is optically attached to the polarization-changing element (330), wherein the reference reflector (381) is positioned to reflect reference beam back through the polarization-changing element (371) and back into the polarizing beam-splitter (330). A retroflector (361, 366) is optically attached to the polarizing beam-splitter (330), the retroflector (361, 366) being positioned to receive the reference beam reflected from the reference reflector (381) and receive the measurement beam after reflection of the measurement beam from a measurement reflector (350) on an object being measured, wherein the retroflector (361, 366) is positioned to further receive a second reference beam and a second measurement beam that are associated with a second measurement axis of the interferometer.