Patent ID: 7428049

Claim:
A defect inspection apparatus for detecting defects of a film comprising: a pair of polarizing plates placed to be crossed nicols at both sides of said film, said polarizing plates being parallel to front and rear surfaces of said film, a polarizing transmission axis of one of said polarizing plates being approximately parallel to a slow axis of said film; a light source for projecting light onto one of said surfaces of said film through one of said polarizing plates; a light receiver placed at an opposite side of said film to said light source, said light receiver firstly receiving the light projected from said light source and transmitted through said film and the other one of said polarizing plates, and then outputting a photoelectric signal corresponding to the received light; and a judging device for judging based on the photoelectric signal from said light receiver as to whether there is a defect in said film or not, wherein when θ 1 represents an angle formed between an optical axis of said light receiver and a normal line that is perpendicular to said surfaces of said film, and θ 2 represents a rotational angle formed between said optical axis and a reference line that is orthogonal to said slow axis of said film, said light receiver is positioned to satisfy the following conditions: 15°≦θ 1 ≦35°, 20°≦θ 2 ≦60°.