Visual inspection system for annular product

A visual inspection system inspecting an appearance of an annular product, comprising:

• a holding unit configured to hold the annular product;
• a rotation drive unit configured to cause the holding unit holding the annular product to rotate about a center axis of the annular product;
• a first illumination unit having a line-shaped light projector disposed along a radial direction of the annular product, the first illumination unit being configured to radiate a filmy illumination light radiated from the line-shaped light projector to an outside surface of the annular product to illuminate the outside surface of the annular product;
• a line sensor camera having a line-shaped light receiving unit, the line sensor camera being arranged such that the line-shaped light receiving unit thereof is disposed parallel to the line-shaped light projector of the first illumination unit and being configured to image, from a direction parallel to a direction of radiation of the illumination light radiated to the annular product by the first illumination unit, a region illuminated with the illumination light on the outside surface of the annular product as a region to be imaged;
• and
• a judgment device configured to process an image captured by the line sensor camera to judge whether the annular product is defective in appearance or not,
• wherein either the holding unit is movable or the first illumination unit and the line sensor camera are moveable between inspection positions to alternately image, as the region to be imaged, a top surface, an inner peripheral surface and an outer peripheral surface of the annular product that is being rotated about the center axis, and wherein the top surface, the inner peripheral surface and the outer peripheral surface of the annular product are curved surfaces,
• wherein the first illumination unit and the line sensor camera are arranged such that the light projector of the first illumination unit and a light receiving element of the line sensor camera intersect with the center axis of the annular product at an angle of not less than 20° and not more than 40°;
• and
• wherein the line sensor camera is arranged such that the light receiving element thereof receives at least a reflected light from the outer peripheral surface of the annular product as the region to be imaged.