A method for optically recognizing alphanumeric characters which involves storing polygonal outer contours and inner contours of reference characters and their relative geometrical positions as normalized reference curves transformed into a tangent space. Outer and inner contours of a character to be recognized are optically scanned and the scanned data is converted into binary data. The outer and inner contours of the character to be recognized are approximated as a polygon, and straight line segments of the polygon are normalized and transformed into a tangent space to generate character curves. The character to be recognized is compared to the reference characters in a rotation-invariant manner by shifting at least its character curve for the outer curve and the reference curves of the outer contours relative to each other in the tangent space until a surface area enclosed by the character curve and a given reference curve is at a minimum. The surface area between the character curves for the outer contour and the inner contours of the character to be recognized and respective reference curves for outer contours and the inner contours of the reference characters are used as a measure of the extent to which the character and the reference characters differ. The reference character which yields the smallest surface area between the character curves and the reference curves is then selected as the recognized character.