Patent ID: 7244927

Claim:
A motor vehicle control panel, having a face ( 2 ) having an aperture, and at least one rotatable knob ( 10 ) for adjustment of a parameter relating to a stream of air which is propelled by a ventilating, heating and/or air conditioning apparatus that at least partially extends through the aperture, wherein: the rotatable knob ( 10 ) is an optical encoder comprising a rotatable part ( 20 ) and a fixed part ( 30 )underneath the face of the control panel; the rotatable part ( 20 ) of the optical encoder at least partially extends through the aperture and is passenger accessible, and the fixed part ( 30 ) is provided with an optical detection device ( 31 ) comprising; at least one light emitter ( 33 ; 37 ) for forming an incident light beam (E 1 ; E 3 ) directed towards the rotatable part ( 20 ); and at least two optical receivers ( 34 , 38 ) capable of intercepting a second light beam (E 2 ; E 4 ) reflected off the rotatable part ( 20 ); the rotatable part ( 20 ) comprises a plurality of radial incremental elements having a reflective surface and consisting of an alternate arrangement of projecting portions ( 23 ; 23 ′) and recesses ( 24 ; 24 ′); the fixed part ( 30 ) is on a base plate ( 1 ) and the alternate arrangement of projection portions and recesses are found on apices or crowns ( 25 , 25 ′) of the radial incremental elements, and at least one crown faces the optical detection device ( 31 ); and wherein the optical receivers ( 34 , 38 ) are offset circumferentially in respect to one another in such a way that one of the optical receivers ( 34 ; 38 ) receives a light beam reflected by the moving part ( 21 ), while the other optical receiver ( 38 ; 34 ) receives none.