characteristics 45 46 shown represent possible predefinitions for the device with which the device operates and according to which it evaluates defects the method according to the invention operates as follows firstly there is generated an image b fig6 of a flat textile structure such as for example that known from fig1 but without defects or representations of defects this can be performed by means of the image recording device 36 this image b is delivered to the first image memory 37 and then stored this image b can be generated through lighting with incident light i e frontally incident light or with back lighting in which case the image recording device 36 and a light source are disposed on different sides of the flat structure in order to produce a basis for an evaluation of real defects in the flat structure 43 representations of typical defects are included in the image b to this end the image b is firstly divided into sections a b c d etc by a two dimensional grid 18 one dimension of this grid 18 represents the quantity for the length l of the defects this being preferably in one direction for continuously increasing length of the defects the other dimension of the grid in the other direction represents a quantity for increasing contrast k of the defects one or both dimensions are preferably graduated in a logarithmic scale representations of defects in this case the defects 2 17 for example are then generated within the.