1. A system comprising: an elongated structure including an instrument lumen extending through the elongated structure, the elongated structure having a distal end including an annular area surrounding an unobstructed opening out of which an end of an instrument inserted through the instrument lumen may extend past the distal end of the elongated structure; a plurality of receptors, each of the receptors comprising an optical system with an optical axis passing through the annular area, the optical systems being distributed around the instrument lumen, wherein each of the receptors captures light from a field of view covering only a portion of an object environment, and wherein the field of view of each of the receptors overlaps with at least one of the fields of view of the other receptors; and a processing system coupled to receive and process image data derived from the light that the receptors capture, wherein the processing system combines the image data to construct a representation of the object environment.