Abstract: Apparatus for detecting and correcting defects in plywood panels carried on a conveyor including a defect detection and measuring device for scanning the surface of the panels to detect and measure the defects; a plurality of correcting units downstream of the device for correcting the defects, and control devices for receiving data from the detection and measuring device and controlling operation of the correcting units to remove and patch the defects, wherein the detection and measuring means projects a light beam transversely onto the surface of the panels and the reflected beam is resolved into a series of points, the position of each of which is measured with respect to the X, Y and Z axes to determine the size of the defect and the ratio of the light intensity of each point with the mean of the light intensity of all points of the reflected beam is measured to determine the type of defect.