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

摘要

The inspection of the walls of a deep hole (12) of minute deameter in a strcture such as an integrated circuit board (10) is carried out by inserting into the hole a reflective optical sphere (14) having a diameter at least slightly smaller than the hole diameter. A coated optical fiber (18) having a diameter substantially less than the diameter of the sphere has one end attached to the sphere. An optical scattering means (22) 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 (20) is provided at the opposite end of the optic fiber, and an optical system (24) is positioned axially at the end of the hole to pick up the image of the illuminated walls reflected from the sphere.