Waste separation method

A method of waste separation, the method comprising:

• irradiating the waste on a feeding device by a source of radiation,
• capturing an image of the waste when irradiated by the source of radiation;
• wherein an item in the waste is provided with a optical relief pattern, the optical relief pattern being provided in or on a surface of the item, the optical relief pattern forming a repetition of dots, a code being stored in a sequence of adjacent ones of the dots,
• processing the image to detect the optical relief pattern;
• decoding the code from the sequence of adjacent ones of the dots of the optical relief pattern;
• automatically separating into a storage, by a separating device, in accordance with the code, the item comprising the optical relief pattern from the waste,
• wherein the source of radiation provides floodlight irradiation along at least part of the surface of the item,
• wherein each dot forms a bump or recess of the surface of the item, the floodlight irradiation along at least part of the surface of the item forming by the dots an image of highlights and shades on the surface of the item,
• wherein capturing the image of the waste when irradiated by the source of radiation comprises capturing the image of highlights and shades, and
• wherein the code is derived from the captured image of highlights and shades and encodes information on how to perform the separating, and wherein the dots of the optical relief pattern are coded into at least four different dot values, at least two of the dot values forming a code information dot value range, the remaining dot values forming a compensation dot value range, the dots having a dot value in the code information dot value range coding the code, the dots having dot values in the compensation dot value range balancing an average dot value of the pattern, a difference in deformation between dots having different dot values in the compensation dot value range being smaller than a difference in deformation between dots having different dot values in the code information dot value range.