mentioned method in further detail fig3 shows the device 25 as a whole this device 25 is equipped with two optical units 26 and 27 which as is schematically represented in fig4 and 5 make it possible for the products 1 2 to be scanned on either side every unit 26 27 respectively has a construction as is schematically represented in fig1 as well as in fig6 which will be described hereafter in order to carry the products 1 2 in the shape of a product stream 4 with a certain width but with a small thickness past the place where they are scanned a device 25 is equipped with means 28 in the shape of a vibrating table 29 from where the products 1 2 are vibrated downward over the edge 30 of this vibrating table 29 via a sliding surface 31 they are guided into a zone 32 where they fall down freely and where they are also scanned as mentioned above the products 1 which have been let through are guided further via a discharge chute 33 whereas the removed products 2 are collected in a recipient 34 or such it is clear that according to a variant instead of a vibrating table 29 use can also be made of a conveyor belt or such also longitudinal ducts or grooves can be provided in the vibrating table to obtain different parallel rows of products 1 2 falling.