Interferometer with deadpath error compensation

摘要

The invention provides for automatic compensation for deadpath error in heterodyne laser displacement measuring device. The embodiment illustrated in figure 3 provides for a quarter wave plate retarder 31 to be partially inserted into the reference beam between beam splitter 30 and reference mirror 26. A similar retarder 33 is placed in the measurement beam between beam splitter 30 and measurement mirror 28 at the reset position D. Retarder 33 is partially mirrored.