Method of calibrating a measuring instrument comprising a laser measuring device that emits a laser beam along a measuring axis, a camera device having a target axis, and a control device, comprising the steps: ▪ taking a first image of a target object by means of the camera with the laser beam turned off, ▪ defining an image portion about a position (Xp, Yp) of the target axis stored in the control device in the first image of the target object, ▪ determining a first contrast (K 1) between the darkest image region (P 1, min) of the image portion and the brightest image region (P 1, max) of the image portion, ▪ comparing the first contrast (K 1) with a first limit value (G 1) stored in the control device, ▪ taking a second image of the target object by means of the camera device with the laser beam turned on, if the first contrast (K 1) does not exceed the first limit value (G 1), ▪ determining a differential image between the first and the second image (51, 53) of the target object, ▪ identifying a received beam reflected and/or scattered by the target object and a surrounding region in the differential image of the target object, ▪ determining a second contrast (K 2) between the brightest image region (P 2, min) of the surrounding region and the darkest image region (P 2, max) of the received beam, ▪ comparing the second contrast (K 2) with a second limit value (G 2) stored in the control device, ▪ determining a centroid of the received beam and the centroid coordinates (X S, Y S), if the second contrast (K 2) does not fall below the second limit value (G 2) and ▪ storing the centroid coordinates (Xs, Ys) of the received beam as new position (Xp, Yp) of the target axis in the control device. ▪ taking a first image of a target object by means of the camera with the laser beam turned off, ▪ defining an image portion about a position (Xp, Yp) of the target axis stored in the control device in the first image of the target object, ▪ determining a first contrast (K 1) between the darkest image region (P 1, min) of the image portion and the brightest image region (P 1, max) of the image portion, ▪ comparing the first contrast (K 1) with a first limit value (G 1) stored in the control device, ▪ taking a second image of the target object by means of the camera device with the laser beam turned on, if the first contrast (K 1) does not exceed the first limit value (G 1), ▪ determining a differential image between the first and the second image (51, 53) of the target object, ▪ identifying a received beam reflected and/or scattered by the target object and a surrounding region in the differential image of the target object, ▪ determining a second contrast (K 2) between the brightest image region (P 2, min) of the surrounding region and the darkest image region (P 2, max) of the received beam, ▪ comparing the second contrast (K 2) with a second limit value (G 2) stored in the control device, ▪ determining a centroid of the received beam and the centroid coordinates (X S, Y S), if the second contrast (K 2) does not fall below the second limit value (G 2) and ▪ storing the centroid coordinates (Xs, Ys) of the received beam as new position (Xp, Yp) of the target axis in the control device.