초록 ▼

Cracks in bridges or other structures are detected by applying a thermal gradient to the test structure in a selected region so heat flows from left to right. A first image of the thermal gradient with heat flowing from left to right is taken and stored for further processing. Next a thermal gradien

Cracks in bridges or other structures are detected by applying a thermal gradient to the test structure in a selected region so heat flows from left to right. A first image of the thermal gradient with heat flowing from left to right is taken and stored for further processing. Next a thermal gradient is applied so heat flows from right to left through the selected region. A second thermal image is taken and stored of the heat flowing from right to left. An image taken before a thermal gradient is applied is subtracted from the first and second images to remove thermal reflection and non-induced gradients from the stored images. Each differentiated image is then normalized by dividing each pixel of the differentiated image by the total photon flux from the undifferentiated image. The second image is than subtracted from the first image producing a third image which highlights features which produce thermal gradients of opposite signs. Paint chips and paint drips and other variations in surface emissivity which can produce the appearance of a thermal gradient have the same apparent gradient when heat is applied from either side. Thus the technique of utilizing two temperature gradient images where the gradient is applied from opposite sides uniquely highlights real defects.

대표청구항 ▼

[ I claim:] [1.] A method for finding flaws in a structure comprising the steps of:a) selecting a region on the structure to be examined;b) inducing a first flow of heat through the selected region;c) imaging the selected region to form at least a first thermal image after the first flow of heat has

[ I claim:] [1.] A method for finding flaws in a structure comprising the steps of:a) selecting a region on the structure to be examined;b) inducing a first flow of heat through the selected region;c) imaging the selected region to form at least a first thermal image after the first flow of heat has induced a first thermal gradient;d) inducing a second flow of heat through the selected region, wherein the second flow of heat is from a substantially different direction than the first flow of heat;e) imaging the selected region to form at least a second thermal image after the second flow of heat has induced a second thermal gradient; andf) processing the first thermal image and the second thermal image to detect thermal gradient features common to both images where the sign of the thermal gradient of the feature changes between the first thermal image and the second thermal image.