US 11,055,836 B2
Optical contrast enhancement for defect inspection
Zehava Ben Ezer, Balfuria (IL)
Assigned to CAMTEK LTD., Migdal Haemek (IL)
Filed by CAMTEK LTD.
Filed on Feb. 12, 2019, as Appl. No. 16/273,162.
Claims priority of provisional application 62/629,761, filed on Feb. 13, 2018.
Prior Publication US 2019/0251686 A1, Aug. 15, 2019
Int. Cl. G06T 7/00 (2017.01); G01N 21/88 (2006.01); G02B 27/30 (2006.01); H04N 5/232 (2006.01)
CPC G06T 7/0002 (2013.01) [G01N 21/8806 (2013.01); G02B 27/30 (2013.01); H04N 5/23212 (2013.01)] 22 Claims
OG exemplary drawing
 
1. A method for inspection an object, the method comprises:
acquiring a defocused image of an area of an object; and
processing the defocused image of the area to find a phase shift between optical paths associated with proximate points of the area; wherein the phase shift is indicative of a defect;
wherein the acquiring of the defocused image comprises illuminating the area with a radiation beam that is spatially coherent and collimated when impinging on the area;
wherein the illuminating comprises passing the radiation beam through an aperture that is defined by an aperture stop that is positioned within an aperture stop plane; and
wherein a size of the aperture is a fraction of a size of the aperture stop; wherein the acquiring of the defocused image is preceded by entering the aperture stop within an illumination path and is followed by removing the aperture stop from the illumination path.