Patent ID: 7127098

Claim:
An image detection method comprising the steps of: sequentially picking up a surface image of a sample at an image pickup position by using image pickup means while moving a scanning stage in one direction and said stage having the sample mounted thereon; sequentially detecting a surface height of the sample at plural points including two points which are respectively on the opposite sides of the image pickup position in said one direction by projecting a slit-shaped light onto a region stretching over said image pickup position, dividing an image of said slit-shaped light projected on said position into plural images and detecting said divided plural images with a linear image sensor while sequentially picking up a surface image of the sample at the image pickup position; sequentially Calculating the height of the sample at the image pickup position based on the height information detected sequentially at the plural points; adjusting the focal position of the image pickup means by using the sample height information sequentially calculated for the plural points; and sequentially picking up a surface image of the sample at the image pickup position by using the image pickup means whose focal position is adjusted while moving the scanning stage having the sample mounted thereon.