Abstract: A method is provided to calibrate an optical array consisting of an image detector and an optical imaging unit to depict a measurement volume on the image detector. At least one image of a periodic calibration pattern within a measurement volume is recorded by the optical array and depicted on a display. The calibration pattern has pattern structure units that differ in respect of at least one pattern structure feature, and the pattern scale that is representative of sizes of the pattern structure units is variable. The method correlates positions of the recorded calibration pattern points with image points on which they are displayed. At least one of the pattern structure units is depicted with an optically differentiable auxiliary unit that depends on the current pattern scale, such that the pattern scale can be determined from the depiction features of at least one depicted auxiliary unit.