Apparatus for detecting defects on bottle sidewalls

An apparatus for detecting defects on bottle sidewalls is disclosed. The apparatus for detecting defects on bottle sidewalls comprises: illumination means for illuminating the sidewall of a bottle; photoelectrically converting means for photoelectrically converting an image of lights transmitted through the sidewall of the bottle illuminated by the illuminating means; defect detecting means for inspecting the transmitted light image photoelectrically converted by the photoelectrically converting means for any defects to detect defects based on brightnesses of at least two points; area-masking means for setting a masking area corresponding to a point to be noted in the transmitted light image, and outputting an area masking signal indicating that the point to be noted is a defect point, based on a distribution of defect points in the masking area; and judging means for judging the presence of a defect on the sidewall of the bottle, based on the area masking signal from the area masking means. The apparatus for detecting defect on bottle sidewalls can detect with high precision opaque defects which are thin and extend over large areas.