Abstract: An optical linear encoder for measuring distance includes a housing with a glass bar having precision gratings; a reading head body which moves along the housing in a measuring direction; and a carriage which is coupled to the reading head body rigidly in the measuring direction while allowing for minor movements in lateral directions. The carriage includes a scanning reticle guided along the glass bar by the carriage at a constant gap from the glass bar; a photo electronic sensor array which reads variations in intensity of the collimated light passing through both scanning reticle and glass bar, and a light source and a beam forming optics, with the beam forming being performed by an off-axis reflector.