METHOD AND APPARATUS FOR INSPECTING CYCLIC PATTERN

• Main Authors: OKAZAWA ATSUSHI, CHINJU TAKUTETSU, NISHIDA MASASHI, SOEDA MASAHIKO
• Format: Patent
• Language: English
• Published: 20.04.2001
• Edition: 7
• Subjects: BASIC ELECTRIC ELEMENTS; ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS; ELECTRICITY; INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIRCHEMICAL OR PHYSICAL PROPERTIES; MEASURING; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS; MEASURING LENGTH, THICKNESS OR SIMILAR LINEARDIMENSIONS; PHYSICS; TESTING

PROBLEM TO BE SOLVED: To quickly and highly accurately inspect a nonuniformity of a cyclic pattern. SOLUTION: When an object with a cyclic pattern is to be picked up by an area sensor camera so as to inspect a color unevenness defect caused by a nonuniformity of the cyclic pattern on the basis of the obtained image, an optical system of the area sensor camera is set to a first focus Fa where a focal point meets a target size at a surface of the object, and a first product image Ia is picked up by the camera. The optical system is then set to a second focus Fb shorter than the first focus Fa and a second product image Ib is picked up by the same camera. The second product image Ib is subtracted from the first product image Ia, thereby forming an emphasis image Ie. The emphasis image is masked by a mask image formed by binarizing the second product image, thereby forming a masked emphasis image Ime. A color unevenness defect of a size corresponding to the target size is detected on the basis of the masked emphasis image.