Patent ID: 8502871

Claim:
A gauge line position measuring device for measuring a position of a gauge line provided on a test piece by a non-contact video method, comprising: a gauge line mark adapted to be provided on the test piece and having said gauge line and a first continuous harmonious color density arranged line-symmetrically with respect to the gauge line; a video camera for taking an image of the gauge line mark on the test piece and outputting gauge line mark image data; and a calculation device for calculating a gauge line position based on the gauge line mark image data, wherein the gauge line mark is a gauge line sticker on which the gauge line mark is printed; and said first continuous harmonious color density is an achromatic or chromatic colored continuous harmonious distribution gradually changed in a direction away from the gauge line and arranged line-symmetrically with respect to the gauge line; wherein the calculation device preliminarily calculates a first function f 1 (x) wherein the X-coordinate is a variable as reference data by integrating the gauge line mark image data in a Y-axis direction parallel to the gauge line before a load is applied on an X-axis direction orthogonal to the gauge line; calculates a second function f 2 (x) where the X-coordinate is the variable by integrating the gauge line mark image data in the Y-axis direction when the gauge line marks are displaced in the X-axis direction by a positional displacement of the gauge line due to the load; and obtains a reference symbol T where a correlation function R 12 (T) relative to the first function f 1 (x) and the second function f 2 (x) has a maximum value, thereby determining the gauge line position.