Method for defect inspection of transparent substrate by integrating interference and wavefront recording to reconstruct defect complex images information
A method for defect inspection of a transparent substrate comprises (a) providing an optical system for performing a diffraction process of object wave passing through a transparent substrate, (b) interfering and wavefront recording for the diffracted object wave and a reference wave to reconstruct the defect complex images (including amplitude and phase) of the transparent substrate, (c) characteristics analyzing, features classifying and sieving for the defect complex images of the transparent substrate, and (d) creating defect complex images database based-on the defect complex images for comparison and detection of the defect complex images of the transparent substrate.
1. A method for defect inspection of a transparent substrate, comprising:
interfering an object diffraction wave passing through said transparent substrate with a reference wave to form at least one hologram, and wavefront recording said at least one hologram to reconstruct defect complex images of said transparent substrate, wherein said reference wave is a spherical wave magnified by an encoding spherical factor to improve lateral resolution of said defect complex images of said transparent substrate;
analyzing and classifying said defect complex images of said transparent substrate by a computer to obtain characteristics classification of said defect complex images of said transparent substrate;
performing numerical propagation and focusing for each classified defect complex images of said transparent substrate to establish image characteristics and spatial distribution of said classified defect complex images in different planes, wherein said each classified defect complex images is recorded no matter which can be imaged or not;
creating defect complex images database based by said computer based-on said characteristics classification of said defect complex images, wherein said created defect complex images database recording includes characteristics classified defect complex images of said transparent substrate, each of said characteristics classified defect complex images, which is recorded with its spatial distribution information and location information in a three-dimensional coordinate axis, containing amplitude image and phase image; and
comparing second defect complex images of a second transparent substrate with said defect complex images in said defect complex images database to define a defect type of said second defect complex images.
2. The method of claim 1 , wherein at least one optical image reduction system is used to record said at least one hologram.
3. The method of claim 2 , wherein said optical image reduction system includes a first and a second lens.
4. The method of claim 1 , wherein types of said defect complex images are classified as phase image and amplitude image.
5. The method of claim 1 , further comprising up-sampling said defect complex images to improve equivalent resolution of a photodetector array of said optical system.
6. The method of claim 5 , further comprising a numerical propagation of Fourier transform approach, convolution approach, angular spectrum approach or Fresnel diffraction transform approach to reconstruct said defect complex images of said transparent substrate.
7. The method of claim 1 , wherein said at least one hologram is recorded by at least one optical image reduction system.
8. The method of claim 1 , wherein said defect complex images are classified as phase image and amplitude image.