Method for detecting bar codes by means of a code reader which has a transmitter emitting transmitted light beams, a deflection unit and a receiver on which transmitted light beams reflected back from a bar code impinge as received light beams, wherein by means of the deflection unit the transmitted light beams periodically scan a scanning area within one scan in each case, and wherein the code reader has an evaluation unit, characterised in that in the evaluation unit for detecting bar codes received signals at the output of the receiver are evaluated in accordance with the following method steps. • forming the differentiated temporal reception signal profile for each scan, • determining valid pairs of a minimum and a maximum following this minimum within the received signal path of a scan, • wherein, in a search for a minimum, successive received signal values are compared and the current received signal value is adopted as the current minimum if it is smaller than the previous received signal value, and wherein a current threshold value S min is calculated from the sum of the current mininum and a threshold δ 0, which is predetermined as an initial value, wherein the search for the minimum is terminated when the current received signal value is above the previously determined current threshold value S min and the current minimum is stored thereon as a valid minimum and a search for a maximum is started thereon, and wherein successive received signal values are compared during a search for a maximum and the current received signal value is adopted as the current maximum if it is greater than the previous received signal value, and wherein a current threshold value S max is calculated from the difference between the current maximum and the or a further threshold δ 0, wherein the search for the maximum is terminated when the current received signal value is below the previously determined current threshold value, and thereafter the current maximum is stored as a valid maximum and the search for a minimum is then started, • determining at least one modified threshold δ from the stored valid minima and maxima of this scan, wherein the modified threshold δ is defined as a certain fraction of the amount of a selected extreme value and wherein its value is contractually greater than its initial value, • determining final pairs of consecutive pairs of minima and maxima by repeating the search for minima and maxima with the modified threshold δ for the saved valid pairs of minima and maxima of the scan, • decoding the barcode on the basis of the determined final pairs of minima and maxima for the respective scan and a digital reception signal derived therefrom, which contains the coding of the code elements of the barcode. • forming the differentiated temporal reception signal profile for each scan, • determining valid pairs of a minimum and a maximum following this minimum within the received signal path of a scan, • wherein, in a search for a minimum, successive received signal values are compared and the current received signal value is adopted as the current minimum if it is smaller than the previous received signal value, and wherein a current threshold value S min is calculated from the sum of the current mininum and a threshold δ 0, which is predetermined as an initial value, wherein the search for the minimum is terminated when the current received signal value is above the previously determined current threshold value S min and the current minimum is stored thereon as a valid minimum and a search for a maximum is started thereon, and wherein successive received signal values are compared during a search for a maximum and the current received signal value is adopted as the current maximum if it is greater than the previous received signal value, and wherein a current threshold value S max is calculated from the difference between the current maximum and the or a further threshold δ 0, wherein the search for the maximum is terminated when the current received signal value is below the previously determined current threshold value, and thereafter the current maximum is stored as a valid maximum and the search for a minimum is then started, • determining at least one modified threshold δ from the stored valid minima and maxima of this scan, wherein the modified threshold δ is defined as a certain fraction of the amount of a selected extreme value and wherein its value is contractually greater than its initial value, • determining final pairs of consecutive pairs of minima and maxima by repeating the search for minima and maxima with the modified threshold δ for the saved valid pairs of minima and maxima of the scan, • decoding the barcode on the basis of the determined final pairs of minima and maxima for the respective scan and a digital reception signal derived therefrom, which contains the coding of the code elements of the barcode.