A novel method of generating optical phase conjugation using an azo-doped liquid crystal valve is proposed for the first time. Its response time, diffraction efficiency, and threshold intensity are measured. The resolution of the device is discussed. An observation of diffraction rings caused by self-phase modulation when a low-power laser beam passes through the azo-doped liquid crystal valve is reported. Finally, these phenomena are shown to be results of the reorientation of liquid crystal molecules driven by the photoinduced isomerization, not merely an azo dye effect or a local heating effect.