Optical-effect touchpad on a steering wheel for finger detection

A system for detecting command gestures made by at least one finger (P, F) of a driver of a motor vehicle, the system comprising:

• at least one interface pad (3) located in proximity to the rim of the steering wheel (8),
• at least one light source (4) that emits an optical beam (L1) mainly in the near-infrared band toward the interface pad (3),
• an imaging sensor (5), for capturing at least images steered (L2) by the interface pad (3) away from the driver,
• wherein the interface pad (3) comprises a base frame (1) and a movable plate (2) that is movable between a rest position (P0) and at least one activation position (P1, P2) obtained by pressing one of the fingers (P, F) on the movable plate (2), the base frame (1) and the movable plate (2) lying generally in a reference plane XY and having a small thickness in the direction Z perpendicular to said reference plane XY, an optical zone of interest seen from the imaging sensor being defined at the interface between the base frame (1) and the movable plate (2), wherein the interface pad (3) comprises at least one elastic deformable seal (6;
• 61, 62;
• 7) interposed between the base frame (1) and the movable plate (2), the elastic deformable seal (6;
• 61, 62;
• 7) being generally absorbent at the optical wavelengths of interest, the interface pad (3) comprising a reflective strip (17) behind the elastic deformable seal (6;
• 61, 62;
• 7) from the point of view of the imaging sensor (5), so that the elastic deformable seal (6;
• 61, 62;
• 7) forms a dim zone (ZF) on the optical path (L1, L2) in the optical zone of interest seen by the imaging sensor (5), the size of the dim zone (ZF) depending on the pressure exerted on the movable plate (2).