Abstract Method and apparatus for detecting defects optically by subjecting objects to a beam of light transmitted by glass fibers and receiving and analyzing the beam as reflected by the objects. The invention may advantageously be applied to the examination of transparent objects such as glass bottles. In accordance with the invention the beam of incident light is modulated with a known frequency before it impinges on the objects, the reflected beam being received upon a photoelectric cell the output of which is connected to an amplifier of the band pass type sensitive to the frequency of modulation of the light. The invention eliminates the necessity for complete housing of the transmitter-receiver, and facilitates the distinguishing of meaningful signals from ''''noise'''' from extraneous sources, not withstanding the use of optical fibers.
A method of examining a transparent object which comprises projecting onto the object at a single examining station by separate elongated vitreous light conducting means a plurality of focused modulated light beams having different modulated frequencies; transforming into separate modulated electrical signals of different modulated frequencies, by means of separate photoelectric cells, modulated light coming from the object and from said separate beams; amplifying said separate electrical signals in separate amplifiers passing only the frequencies of modulation of those signals respectively; and delivering the amplified modulated signals to separate detectors of signal deviations.
Claim 2
Independent Claim
93 words
A method of examining a transparent object which comprises projecting onto the object at a single examining station by separate elongated vitreous light conducting means a plurality of focused modulated light beams having different modulated frequencies; transforming into separate modulated electrical signals of different modulated frequencies, by means of separate photoelectric cells, modulated light coming from the object and from said separate beams; amplifying said separate electrical signals in separate amplifiers passing only the frequencies of modulation of those signals respectively; and delivering the amplified modulated signals to separate detectors of signal deviations.
Claim 3
Dependent Claim
45 words
A method according to claim 1 in which there are simultaneously employed a first and a second light beam, the first and second light beams being modulated, respectively, at frequencies having a ratio with respect to each other of from about 1/1.5 to about 1/1.7.
Claim 4
Dependent Claim
24 words
A method according to claim 2, wherein the first and second light beams are provided by a single light source and two modulating means.
Claim 5
Dependent Claim
36 words
A method according to claim 2 in which there is a third light beam, the third light beam being modulated at a frequency with respect to the first light beam at a ratio of about 1/2.5.