An inspecting method for inspecting foreign substances, comprising projecting beams from an illumination system arranged above a light-permeable body to be inspected with an angle of incidence of a first elevation angle onto an upper face of the body, and receiving a reflecting light and a scattering light generated by the beams with a photodetecting angle of a second elevation angle by a photodetecting system. The method further comprising, before the beams are projected, setting a width of the beams of the illumination system to be not larger than w calculated according to an expression w<2* sin .alpha.*t{tan[sin.sup.-1 {sin(90.degree.-.alpha.)/n}]-tan[sin.sup.-1 {sin(.theta.-90.degree.)/n}]} from the angle of incidence .alpha., the photodetecting angle .theta., a thickness t of the body and a refractive index n of the body to a substance over the body.
Fiber optic alignment methods and apparatus in accordance with the present invention first identify a target beam width incidence on an end of an optical element. The end of the optical element is placed into a beam of light at an axial location relative to the beam of light. The end of the optical element is subsequently moved transversally (perpendicular) to the beam of light until a position of maximum optical power, as measured through the optical element, is identified. A beam width of the beam of light is measured at that axial location. The movement and measurement sequence is repeated at multiple axial locations relative to the beam of light. Linear regression, or an equivalent approach is used, to predict an axial location relative to the beam of light with the target beam width. The end of the optical element is then moved to the axial location with the target beam width.
An inspection system for a sheet of glass. The system comprises a first laser and a second laser, each of which provide a sheet of light, a cylindrical lens system, and a first light detection system and a second light detection system. The first laser is located at the focal point of the lens system. The second laser is located at a distance from the lens system that is greater than that of the first laser, and off of the axis of the lens system. The first light detection system receives light from the first laser and the second light detection system receives light from the second laser. The inspection system is adapted to position a sheet of glass between the lens system and the detection systems. A method is also described.
A method and apparatus for detecting defects are provided for detecting harmful defects or foreign matter with high sensitivity on an object to be inspected with a transparent film, such as an oxide film, by reducing noise due to a circuit pattern. The apparatus for detecting defects includes a stage part on which a substrate specimen is put and which is arbitrarily movable in each of the X-Y-Z-.theta. directions, an illumination system for irradiating the circuit pattern with light from an inclined direction, and an image-forming optical system for forming an image of an irradiated detection area on a detector from the upward and oblique directions. With this arrangement, diffracted light and scattered light caused on the circuit pattern through the illumination by the illumination system is collected. Furthermore, a spatial filter is provided on a Fourier transform surface for blocking the diffracted light from a linear part of the circuit pattern. The scattered and reflected light received by the detector from the specimen is converted into an electrical signal. The converted electrical signal of one chip is compared with that of the other adjacent chip. If these signals are not identical to each other, the foreign matter is determined to exist on the specimen in detection.
