Device for calibrating an irradiation system of an apparatus for producing a three-dimensional work piece, the irradiation system comprising a first irradiation unit for selectively irradiating a first irradiation beam along a first operating axis onto an irradiation plane and a second irradiation unit for selectively irradiating a second irradiation beam along a second operating axis onto the irradiation plane , wherein the device comprises: - a control unit adapted to control the first irradiation unit so as to irradiate the first irradiation beam onto the irradiation plane according to an irradiation pattern and to control the second irradiation unit so as to displace the second operating axis relative to the irradiation plane such that the second operating axis traverses the irradiation pattern produced by the first irradiation unit onto the irradiation plane ; and - a detecting unit adapted to detect process emissions emitted from a region of an impingement point on the irradiation plane at which the second operating axis of the second irradiation unit passes the irradiation plane and to output signals indicative of the detected process emissions to the control unit , and wherein the control unit is further adapted to: - determine a position (x 1...n , y 1...n ) of the irradiation pattern produced by the first irradiation unit on the irradiation plane , - determine a position (x' S1 , y' S1 ) of at least one intersection point between the irradiation pattern produced by the first irradiation unit and the second operating axis of the second irradiation unit based on the signals output by the detecting unit , and - calibrate the irradiation system based on the determined position (x 1...n , y 1..n ) of the irradiation pattern produced by the first irradiation unit and the determined position (x' S1 , y' S1 ) of the at least one intersection point. - a control unit adapted to control the first irradiation unit so as to irradiate the first irradiation beam onto the irradiation plane according to an irradiation pattern and to control the second irradiation unit so as to displace the second operating axis relative to the irradiation plane such that the second operating axis traverses the irradiation pattern produced by the first irradiation unit onto the irradiation plane ; and - a detecting unit adapted to detect process emissions emitted from a region of an impingement point on the irradiation plane at which the second operating axis of the second irradiation unit passes the irradiation plane and to output signals indicative of the detected process emissions to the control unit , and wherein - determine a position (x 1...n , y 1...n ) of the irradiation pattern produced by the first irradiation unit on the irradiation plane , - determine a position (x' S1 , y' S1 ) of at least one intersection point between the irradiation pattern produced by the first irradiation unit and the second operating axis of the second irradiation unit based on the signals output by the detecting unit , and - calibrate the irradiation system based on the determined position (x 1...n , y 1..n ) of the irradiation pattern produced by the first irradiation unit and the determined position (x' S1 , y' S1 ) of the at least one intersection point. <EOS>