Detecting a mixture ratio of two components of a textile fiber structure

A method for detecting a mixture ratio of two components of a textile fiber structure, wherein:

• electromagnetic radiation in a spectral band is transmitted from a radiation source in a direction of the textile fiber structure,
• at least a part of the electromagnetic radiation interacts with the textile fiber structure,
• at least a part of the electromagnetic radiation is received by a radiation sensor after interacting with the textile fiber structure, and
• at least a part of the electromagnetic radiation is filtered by a spectral filter with spectral properties in the spectral band before or after interacting with the textile fiber structure,
• wherein,
• the spectral filter is selected such that,
• a transmittance or a reflectance in the spectral band has at least one local maximum and at least one local minimum, and
• its spectral properties in the spectral band are adapted to the spectral properties of the radiation source and each of the two components in the textile fiber structure such that a radiation intensity received by the radiation sensor is a monotonous function of the mixture ratio of the two components.