An embodiment simultaneously receives light waves emanating from an object and having first frequency components f1.1 and f1.2, and pumped monochromatic coherent light waves having a second frequency f2. The method non-linearly combines the light waves having the first frequency component f1.1 and the pumped monochromatic coherent light waves, and generates coherent light waves having a third frequency component f3.1 that is a sum of the first frequency f1.1 and the second frequency f2. The method non-linearly combines the light waves having the first frequency component f1.2 and the pumped monochromatic coherent light waves, and generates coherent light waves having a third frequency component f3.2 that is a sum of the first frequency f1.2 and the second frequency f2. The method digitizes the generated coherent light waves and outputs an image responsive to the light waves emanating from the object.