An imaging instrument for controlling a target designation makes it possible to visualise a target designation spot (SP) within a scene (SC), while using only one image sensor. To do this, a filter is arranged on the image sensor, in a restricted area (ZC) of same. The filter makes it possible to increase a contrast and a signal-to-noise ratio for an image of the target designation spot, when a misalignment (DP) is produced in order to bring the image of the target designation spot into the area of the filter.