A polarization-modulation scanning laser microscope includes a conventional laser scanning microscope, which has been improved by addition of: a polarization state generator; a polarization state analyzer; a photo-detector for receiving laser light transmitted though a sample; a signal demodulator providing two signals in response to the transmitted laser light, one of the signals being indicative of polarization orientation, and the other signal being indicative of magnitude of the transmitted polarized light. A relay interface toggles between the two signals provided by the signal demodulator and at least one other signal provided either by the photodiode of the laser scanning microscope, or by an external optical beam induced current, or both. A signal processing unit provides an image output to a display device.