Defect detection method and device

Abstract

A defect detection deviceis provided with: a laser light sourcefor irradiating laser light to a measurement region R of a surface of an inspection object S; a laser light source control unitfor controlling the laser light source so as to cause laser light to be outputted continuously or quasi-continuously for a time longer than a period of vibration generated in the inspection object; an interferometer (speckle shearing interferometer) for generating interference light in which reflected light of the laser light reflected in the measurement region and reference laser light emitted from the laser light sourceinterfere; a detector (image sensor) for detecting the intensity of the interference light for each point in the measurement region R; a phase shifterfor shifting the phase of the reflected laser light or the reference laser light; an integrated intensity pattern determination unitfor obtaining an integrated intensity obtained by integrating the intensity for each point over an integration time longer the period of the vibration in three or more phases, the phase being shifted by the phase shifterinto three or more different phases; an interference degree distribution generation unitfor obtaining the distribution of the degree of interference based on the integrated intensity obtained in each of the three or more phases for each point; and a defect detection unitfor detecting a defect in the measurement region R based on the distribution of the degree of interference in the measurement region R.