An indirect radar holography apparatus for scanning a scene and generating a high-density signal pattern representing the scene. The apparatus illuminates the scene with radiation according to an illumination signal; generates a reference signal from the illumination signal; detects radiation emitted in a predetermined spectral range from a spot of the scene; generates a radiation signal per spot from the detected radiation; performs control so that radiation is detected at a number of spots distributed over the scene, the number being lower than the number of intensity signals of the high-density signal pattern; combines the radiation signals generated from the detected radiation and the reference signals to obtain a low-density signal pattern of intensity signals; and processes the intensity signals of said low-density signal pattern to generate the high-density signal pattern by applying compressive sensing to the low-density signal pattern.