A 4-Pi microscope for imaging a sample, comprising a first objective for focusing a first light beam on the sample at a spatial point one or more Digital Optical Phase Conjugation (DOPC) devices, wherein the DOPC devices include a sensor for detecting the first light beam that has been transmitted through the sample and inputted on the sensor; and a spatial light modulator (SLM) for outputting, in response to the first light beam detected by the sensor, a second light beam that is an optical phase conjugate of the first light beam; and a second objective positioned to transmit the first light beam to the sensor and focus the second light beam on the sample at the spatial point, so that the first light beam and the second light beam are counter-propagating and both focused to the spatial point.