Method for measuring the thickness of flat workpieces

The invention relates to a method for measuring a thickness of a flat workpiece. A method for measuring the thickness of flat workpieces processed in a double-side processing machine comprises steps of processing the workpieces in a working gap formed between an upper working disk and a lower working disk configured to remove material from the workpieces, optically measuring the thickness of the workpieces during processing by at least one optical thickness measurement apparatus disposed on at least one of the upper working disk or the lower working disk, wherein at least one optical thicknessmeasurement apparatus configured to measure the thickness of the workpieces disposed in the working gap through at least one through-hole in a corresponding upper working disk or the lower working disk, supplying the measurement results of the at least one thickness measurement apparatus to a control apparatus of the double-side processing machine, and terminating the processing of the workpiecesonce a previously specifi