Patent ID: 7852982

Claim:
A method of testing whether a foreign material including an Fe element or an Al element is adhered to a substrate for a liquid crystal display device in order to select the substrate having the foreign material adhered thereto and remove the substrate during a substrate manufacturing process, comprising: a first test step of detecting size and position of foreign material adhered to substrates; and further steps of excluding a substrate from which the foreign material with a sufficient size to damage an opposite substrate is detected among the substrates having the foreign materials adhered thereto, which are detected in the first test step, performing position adjustment between a test device and the foreign material is detected in the first test step, for the substrates remaining after excluding the substrate, and testing only whether the foreign material includes an Fe element or an Al element, wherein, the position adjustment is performed between the test device and a foreign material defect, based on information of coordinates of the position obtained in the first test step, a camera unit is used to capture an image of a position where there is the foreign material, detailed coordinates of the foreign material are determined from the image, and position adjustment between the test device and the foreign material is performed based on the detailed coordinates, and when the foreign material includes the Fe element or the Al element, the test device determines that the substrate is defective.