Method and apparatus for the inspection of defects

An apparatus for inspecting an object, the object including an element coated with a transparent protection layer, to detect a defect within or on the surface of the transparent protection layer, said apparatus comprising:

• means for illuminating the surface of the object obliquely with a slit-formed illumination light;
• means for automatically focusing the illumination light on the surface of the transparent protection layer;
• means for condensing light reflected obliquely from the transparent protection layer;
• means for converting the condensed reflected light into a first image signal;
• means for detecting waveforms in the first image signal less than a first threshold level to provide a first defect signal indicative of a void in the surface of the transparent protection layer;
• means for detecting waveforms in the first image signal greater than a second threshold level to provide a second defect signal indicative of an etching remnant on the surface of the transparent protection layer;
• means for condensing light scattered from the transparent protection layer in a direction substantially normal to the surface of the transparent protection layer;
• means for converting the condensed scattered light into a second image signal;
• and
• means for detecting waveforms in the second image signal greater than a third threshold level to provide a third defect signal indicative of a transparent foreign body in the transparent protective layer.

A method of inspecting an object, the object including an element coated with a transparent protection layer, to detect defects within or on the surface of the transparent protection layer, said method comprising:

• illuminating the object obliquely with an illumination light;
• converting light reflected obliquely from the surface of the transparent protection layer into a first image signal;
• detecting waveforms in the first image signal less than a first threshold level to provide a first defect signal indicative of a void in the surface of the transparent protection layer;
• detecting waveforms in the first image signal greater than a second threshold level to provide a second defect signal indicative of an etching remnant on the surface of the transparent protection layer;
• converting light scattered from the transparent protection layer in a direction substantially normal to the surface of the transparent protection layer into a second image signal;
• and
• detecting waveforms in the second image signal greater than a third threshold level to provide a third effect signal indicative of a foreign particle within the transparent protection layer.

An apparatus for inspecting an object, the object including an element coated with a transparent protection layer, to detect defects within or on the surface of the transparent protection layer, said apparatus comprising:

• means for illuminating the object obliquely with an illumination light;
• means for converting light reflected obliquely from the surface of the transparent protection layer into a first image signal;
• means for detecting waveforms in the first image signal less than a first threshold level to provide a first defect signal indicative of a void in the surface of the transparent protection layer;
• means for detecting waveforms in the first image signal greater than a second threshold level to provide a second defect signal indicative of an etching remnant on the surface of the transparent protection layer;
• means for converting light scattered from the transparent protection layer in a direction substantially normal to the surface of the transparent protection layer into a second image signal;
• and
• means for detecting waveforms in the second image signal greater than a third threshold level to provide a third defect signal indicative of a foreign particle within the transparent protection layer.