An apparatus and to a method for imaging the inner contour of a tube are provided. The method includes radiating light having a first polarization direction onto a first tube end in the longitudinal direction of the tube; reflecting the light downstream of a second tube end, wherein the light that is returning through the tube due to the reflection has a second polarization direction that is orthogonal with respect to the first polarization direction; and filtering the returning light with a polarization filter to transmit only the returning light.