Calibration element for a polarization axis measuring device and polarization axes measuring device with a calibration element

The invention relates to a calibration element (10) for insertion into a receptacle (108) of a polarization axis measuring device (100) (a transilluminable calibration body (12) of polarizing material having a first and an opposite second flat side (26, 28), and a holder 14) (for engaging the calibration element 12), which holder (14) has at least one positioning device (20) intended for reproducible arrangement (in a receptacle 108). In this case, the holder (14) to an irradiation region (16) for irradiating the calibration element (12) with light. The positioning device (20) has at least two diametrically opposite positioning elements (22, 24, 32, 34, 42), wherein the holder (14) with the calibration body (12) with either its first flat side (26) or with its second flat side (28) is used the polarization axes of the measurement device (100) into the receptacle (108). The invention further relates to a polarization axis measuring device (100) with such a calibration element (10) and a method for calibrating a polarization axes measuring device (100) with such a calibration element (10).