AUTOMATIC LASER BEAM SCANNING FILM FLAW DETECTOR
1,254,325. Flaw detection in films. GAF CORP. Jan. 6, 1969 [Jan. 8, 1968], No. 712/69. Heading G1A. In an apparatus for detecting flaws in a running web by means of detecting the reflection from the film of a transversely scanning laser beam, pulses in the detector output resulting from the beam tra...
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Zusammenfassung: | 1,254,325. Flaw detection in films. GAF CORP. Jan. 6, 1969 [Jan. 8, 1968], No. 712/69. Heading G1A. In an apparatus for detecting flaws in a running web by means of detecting the reflection from the film of a transversely scanning laser beam, pulses in the detector output resulting from the beam traversing the film edges or a flaw are applied to a counter which is arranged to operate an alarm at a count of three and is reset after each traverse. The arrangement precludes false alarms due to the beam traversing the film edge. The traverse may be effected by a rotating multi-sided mirror and the counter may be reset either by a light transducer in the scan path adjacent the running film or by an electromagnetic pulse generator coupled to the rotating mirror. The number of flaws in a scan may be counted and recorded. The sensor may be a photo-multiplier the dynode voltage to which is regulated to give a constant output irrespective of the incident light and the dynode voltage is indicative of the incident light value. In the detection circuit Fig. 5, a reference voltage 51 is applied to the dynode regulator and its output is passed through an emitter follower 52 and a high and low pass filter 53 to an operational amplifier 54 and to a peak holding operational amplifier 57 providing an output proportional to the average peak input in a time determined by capacitor 58. The outputs from the two amplifiers are compared in a unit 60 to reject unwanted noise signals before being applied to the counter through an amplitude discriminating flip-flop 61. |
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