Method and device for detecting faults in flat glass

A method of determining the optical quality of and detecting faults in flat glass, especially float glass, or other optically transparent materials, wherein a video camera (1) is arranged to monitor an illuminating device (3) either through the material (2) or by observing the reflection thereof on the material, the focus being on the glass and the material, respectively, and the video camera (1) generates signals in dependence on the quality of the glass (2) and these signals are evaluated, characterized in that an illuminating device (3) is used whose color and/or intensity is changed in a defined manner from one outer edge to the other one, that an observation spot (6) of the video camera (1) in the faultless condition of the glass (2) is located substantially in the middle of the illuminating device (3), that the illuminating device (3) has assigned thereto two video signals U1,U2 according to color and/or intensity and that a change of intensity of the video signals U1,U2 is used for evaluating the quality of the glass (2).