Gauge line position measuring device, program for measuring a gauge line position, and gauge line mark

1. 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.

2. A gauge line position measuring device according to claim 1 , wherein the gauge line mark further includes a second continuous harmonious color density line-symmetrical to a line orthogonal to the gauge line and passing through a predetermined point on the gauge line; and when the load is applied on the test piece, the gauge line is displaced toward an X-axis direction orthogonal to the gauge line and a Y-axis direction parallel to the gauge line, and the calculation device calculates a X-coordinate and a Y-coordinate of the test piece by using the gauge line mark having the second continuous harmonious color density.

3. A gauge line position measuring device according to claim 1 , wherein in the first continuous harmonious color density, the gauge line has a black color, and a density of the black color is gradually changed in the direction away from the gauge line without a space.

4. A gauge line position measuring device according to claim 3 , wherein an area exceeding ±π from the gauge line has a white color.

5. A gauge line position measuring device according to claim 1 , wherein the first continuous harmonious color density is arranged symmetrically with respect to the gauge line and a line orthogonal to the gauge line, and the first continuous harmonious color density is gradually changed in a direction away from a position where the first gauge line intersects with the line orthogonal to the gauge line.