Patent ID: 7372553

Claim:
An apparatus for detecting an internal defect in an optical fiber, the apparatus comprising: a detection light illumination device for illuminating detection light to the optical fiber from a direction that crosses the axis of the optical fiber; an imaging device that takes an image of the optical fiber illuminated by the detection light from a direction that crosses the optical axis of the detection light, and outputs light intensity distribution signals in the radial direction perpendicular to the axis of the optical fiber; and a defect detection section that obtains the light intensity distribution signals continuously in the axial direction of the optical fiber, and detects the internal defect based on the level of the light intensity distribution signals in the radial direction and the axial direction, wherein the imaging device is a line sensor camera having plural imaging elements in line, and the detection light illumination device is offset from a center axial line of the optical fiber such that the light axis of the illumination is only in the opposite side of the line sensor camera with respect to the center axial line of the optical fiber.