1. Apparatus for detecting defects of an object having linear straight line features and nonlinear defects comprising: a coherent light source for emitting coherent light; an incoherent light source for emitting incoherent light; a first collimator for collimating said coherent light to a prescribed light thickness; a second collimator for collimating said incoherent light to a prescribed light thickness; means for irradiating coherent light passed through said first collimator and incoherent light passed through said second collimator on the same optical axis to said object; a transform lens for transforming the intensity distribution of permeated light or reflected light of said object into a Fourier-transform pattern; a spatial filter located on the Fourier-transform plane of said transform lens, and for preventing the passing of coherent light having information of said linear straight line features of said object; and means for projecting a coherent image and an incoherent image respectively passed through said spatial filter on one another.