The complete polarization state generator (PSG), which consists of one rotatable polarizer and one variable retarder with a quarter-wave plate, is introduced. The orientation angle of its output polarization ellipse equals half of the retardance of the variable retarder, and the ellipticity angle corresponds to the polarizer azimuth. The PSG is employed in the quantitative orientation-independent differential polarization microscope, which uses polarized light states with the same ellipticity and different orientation angles. Image processing algorithms using three or four frames are described.