Abstract An inspection system for web materials that includes electronic means responsive to means scanning the web for detecting a nonuniform appearance condition of the web. The electronic means provides a low signal-to-noise ratio signal having AC and DC components. A first DC extractor circuit is coupled to said electronic means for extracting the DC component of said signals and providing an AC signal output having a pre-established lower bandwidth limit. A low pass filter is connected to said first DC extractor circuit to permit a preselected band of frequencies from said AC signal output representative of said nonuniform web appearance to pass through a rectifier connected to said filter. The rectifier produces a DC signal from said AC signal output having an RMS value representative of the said nonuniform web appearance. An amplifier conditions the said DC signal representative of said value of nonuniform web appearance, such that said amplifier output characterizes the uniformity in appearance of said web. A long time constant averaging filter is connected to said amplifier for producing a smoothed amplitude time-averaged signal from said DC signal level produced from said AC signal output. The persistence and magnitude of said nonuniform appearance condition is characterized by a change in amplitude of said time-averaged signal representing said uniformity in appearance of said web.
In an inspection system for web materials that includes electronic means responsive to means scanning the web for detecting a nonuniform appearance condition of the web, said electronic means providing a low signal-to-noise ratio signal having AC and DC components, the improvement comprising: a first DC extractor circuit coupled to said electronic means for extracting the DC component of said signal and providing an AC signal output; a low pass filter connected to said fist DC extractor circuit for permitting a preselected band of frequencies from said AC signal output representative of said nonuniform web appearance to pass through; a rectifier connected to said low pass filter, said rectifier producing a DC signal from said AC signal output, said DC signal having an RMS value representative of the said nonuniform web appearance; an averaging filter connected to said rectifier for producing a time-averaged signal from said DC signal level produced from said AC signal output, the persistence and magnitude of said nonuniform appearance condition being characterized by a cHange in amplitude of said time-averaged signal; and means for recording said time-averaged signal and signalling when said time-averaged signal exceeds a preselected threshold value.
Claim 2
Dependent Claim
193 words
In an inspection system for web materials that includes electronic means responsive to means scanning the web for detecting a nonuniform appearance condition of the web, said electronic means providing a low signal-to-noise ratio signal having AC and DC components, the improvement comprising: a first DC extractor circuit coupled to said electronic means for extracting the DC component of said signal and providing an AC signal output; a low pass filter connected to said fist DC extractor circuit for permitting a preselected band of frequencies from said AC signal output representative of said nonuniform web appearance to pass through; a rectifier connected to said low pass filter, said rectifier producing a DC signal from said AC signal output, said DC signal having an RMS value representative of the said nonuniform web appearance; an averaging filter connected to said rectifier for producing a time-averaged signal from said DC signal level produced from said AC signal output, the persistence and magnitude of said nonuniform appearance condition being characterized by a cHange in amplitude of said time-averaged signal; and means for recording said time-averaged signal and signalling when said time-averaged signal exceeds a preselected threshold value.
Claim 3
Dependent Claim
19 words
The system defined in claim 1, including a second DC extractor circuit connected between said filter and said rectifier.
Claim 4
Dependent Claim
86 words
The system as defined in claim 2, each of said first and second DC extractor circuits comprising: an amplifier; a follower; a charging circuit connected between the amplifier and follower, said charging circuit including a capacitor connected between the output of the amplifier and the input of the follower; a resistor connected between the input of the follower and ground; and an electronic switch connected from the input of the follower to ground, said switch being operated in timed relationship with said low signal-to-noise ratio signal.
Claim 5
Dependent Claim
70 words
The system as defined in claim 1, said system being a flying spot inspection system for web materials that includes a radiation source, a means for traversing a beam of radiation from said source in a scan across the web, said electronic means being responsive to said beam of radiation in the transmission or reflection mode with respect to said web for detecting a nonuniform appearance condition of the web.
Claim 6
Dependent Claim
20 words
The system as defined in claim 1, including a selectable bias amplifier connected between said rectifier and said averaging filter.