Disclosed is a system for detecting command gestures made by a finger of a driver of a motor vehicle, including an interface pad, a light source that emits an optical beam in the infrared band toward the interface pad, an imaging sensor, for capturing images steered by the interface pad away from the driver, with a base frame and a movable plate, an optical zone of interest seen by the imaging sensor being defined at the interface between the base frame and the movable plate, the interface pad including an elastic deformable seal interposed between the base frame and the movable plate, the deformable seal including a first inclined facet, so that an optical path passing via the first inclined facet is proportionally modified by the deformation of the seal under the effect of the movement of the movable pad.