Weft thread reflection optical sensor in a weaving weft feeder

A reflection optical sensor for the detection of a weft thread in a weaving weft feeder, comprising a light emitter and a light receiver assembled on a relative supply printed circuit board and configured to be housed in an arm of the weft feeder which projects towards a front part of the weft feeder and extends alongside a weft feeder drum whereon weft thread coils are wound, so as to form a path of direct light radiation, from said light emitter towards a respective reflective surface placed on said weft feeder drum, and of reflected light radiation, from said reflective surface to said light receiver, for detecting the presence or absence of a weft thread running through said path, wherein said light emitter comprises a light emitter lens and said light receiver comprises a light receiver lens, wherein said light emitter and light receiver are assembled on said supply printed circuit board such that an optical axis of the light emitter lens is arranged mutually parallel to an optical axis of the light receiver lens, both said optical axes being perpendicular to a supply printed circuit board plane, and wherein the optical sensor further includes a screening diaphragm of the reflected light radiation coming from said reflective surface and directed towards an optical detector of said light receiver, said screening diaphragm being configured to convey to the optical detector of the light receiver only a portion of the reflected light radiation, and said screening diaphragm having a cylindrical shape, whose cylinder axis is inclined with respect to the optical axis of the light receiver lens.