Arrangement for recognizing undesirable particles in textile fibre material

In a device for identifying undesirable particles in textile fibre material, especially on spinning preparation machines, in which the detection of the undesirable particles is effected by optoelectronic means, the fibre material can be detected by a recognition device and the measurement results can be supplied to an image-processing device. In order substantially to improve evaluation of the measurement of the undesirable particles, there is a combing-out element for at least one fibre sliver, with which a fibre tuft having open ends in the working direction and a fibre tuft having open ends opposite to the working direction can be produced. The measured values of undesirable particles at both fibre tufts can be supplied to a comparison device and the comparison values can be used for optimising setting parameters and/or structural elements of the spinning preparation machines.