Patent ID: 6534778
Filing Date: 2003-03-18
Classification: G01N

Abstract:
A ball detecting apparatus for optically detecting non-transparent balls carried one by one by a transparent liquid through a transparent tube having an inner diameter slightly larger than a diameter of the balls, said ball detecting apparatus comprising:a surface light source for projecting diffused light having a predetermined beam spread angle into said tube, a photo detector arranged opposite to said surface light source with said tube therebetween, and judging means for judging passage of said balls carried in said tube based on a light receiving signal produced by said photo detector, wherein said photo detector comprises a light receiving area for receiving both a component of the diffused light projected from said surface light source that has passed through said transparent liquid and a component of the diffused light projected from said surface light source that has been deflected by a bubble produced in said transparent liquid, wherein said light receiving area is adapted to be at least momentarily completely shielded from said diffused light by each of said balls as each of said balls passes through said tube, wherein said light receiving area of said photo detector is dimensioned such that a light receiving angle thereof can be completely covered by each of said balls at least momentarily as each of said balls passes through said tube, and wherein a light projecting area of said surface light source is greater than said light receiving area of said photodetector.