Apparatus for inspection of the walls of deep holes of minute diameter

摘要

The inspection of the walls of a deep hole of minute diameter in a structure such as an integrated circuit board is carried out by inserting into the hole a reflective optical sphere having a diameter at least slightly smaller than the hole diameter. A coated optical fiber having a diameter substantially less than the diameter of the sphere has one end attached to the sphere. An optical scattering means is interposed between the sphere and the fiber to disperse illumination from the optic fiber to illuminate the walls of the hole. A source of illumination is provided at the opposite end of the optic fiber, and an optical system is positioned axially at the end of the hole to pick up the image of the illuminated walls reflected from the sphere.