Patent ID: 7324201

Claim:
A yarn sensor for optically scanning a yarn traveling in its lengthwise direction through a measurement gap, comprising: a light source for projecting a beam of light across the measurement gap, a first receiver for directly transmitted light, a second receiver for light reflected from the yarn, a third receiver for light reflected from the yarn, and elements for transmitting the light between the light source, measurement gap and receivers, the light transmitting elements comprising: a first light-transmitting element disposed between the light source and the measurement gap and including a diaphragm and a lens, downstream of the light source in the direction of light projection, and arranged such that the diaphragm is projected at least approximately into infinity, and second and third light-transmitting elements respectively disposed between the measurement gap and the second and third reflected light receivers, each of the second and third light-transmitting elements comprising a lens disposed upstream in the projected direction of the light reflected from the yarn such that, in the absence of the yarn, projected images on an opposing surface of the measurement gap are detectable by the second and third receivers essentially outside both opposite sides of a projected image of the light source across the measurement gap.