Holographic light detection and ranging

A method for surveying a scene, the method comprising:

• providing output light having a first characteristic from a light source;
• receiving the output light from the light source at a spatial light modulator, “SLM”, arranged to receive the light from the light source;
• providing a sequence of computer-generated holograms to the spatial light modulator;
• displaying the sequence of computer-generated holograms on the spatial light modulator;
• spatially-modulating with the SLM the output light from the light source in accordance with the computer-generated holograms displayed on the SLM, thereby outputting spatially-modulated light from the SLM to the scene, wherein each computer-generated hologram forms structured light having a corresponding pattern in a replay field within the scene;
• and
• receiving light having the first characteristic from the scene at a light detector, the light detector outputting a light response signal, wherein the light detector comprises an array of light detecting elements, the light being received at the light detector through an optical system associated with the array of light detecting elements, the optical system causing each light detecting element to receive light having the first characteristic from a respective sub-area of the replay field within the scene,
• wherein the optical system is arranged so that the each light detecting element of the array of light detecting elements is arranged to detect light reflected from an individual field of view, “IFOV”, of an array of individual fields of view, “IFOVs”, wherein the array of IFOVs corresponds to the replay field within the scene;
• wherein the structured light formed by at least one computer-generated hologram of the plurality of computer-generated holograms is a pattern comprising a plurality of discrete light spots having a selected distribution, shape and brightness, wherein the light spots are spatially separated from each other and each light spot is arranged to illuminate a corresponding IFOV within the scene;
• wherein the holographic controller changes the pattern of the structured light formed in the replay field by at least one of the plurality of computer-generated holograms.