Synchronous optical measurement and inspection method and means
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Abstract
A method for finding holes, and other related defects and measuring characteristics of sheets of industrial material. Optical detections systems are constantly plagued by intense ambient light and challenged in accuracy. The invention exhibits a defect detection method and apparatus that is resistant to intense ambient light and is capable of inspecting sheets of material (410, 510, 610, 710) continuously, without integration of long periods. In the invention, synchronous detection between the optical transmitters and receivers is utilized. The invention is applicable for inspecting and measuring materials like paper, metal, rubber, plastic, aluminum foil, copper foil, film, coated metal sheet or any other sheet-like material that could run on a production line. The invention is also applicable for finding special defects like holes, pinholes, scratches, spots, cracks, edge faults, streaks, surface faults or any other conceivable defects.
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Citations
46 Claims
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1-24. -24. (canceled)
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25. An optical measurement and inspection method comprising at least two light emitters, at least one light receiver, at least one signal generator connected to at least one light emitter and at least one light receiver and means for converting the received light to electrical current, characterised in that,
a sheet of material lies or traverses between and/or in front of at least two light emitters and at least one light receiver (200), at least one signal generator controls at least one light emitter and at least one light receiver by sending them an electronic synchronisation signal and thereby synchronises the emission and detection of light rays (205, 215, 245), at least one signal generator drives at least two light emitters with different carrier frequencies waveforms and/or phases, and at least one light receiver with both of these frequencies, waveforms and/or phases, at least two light emitters emit at least two rays of light (220), at least two rays are incident on the stationary or traversing sheet (225), at least two grazing, transparent and/or reflected rays of light from the sheet or directly from the light emitters are detected by the same light receiver (230), the intensity of at least one said emitted ray of light follows a carrier waveform signal and at least one received light ray is demodulated from the carrier waveform signal using the electronic synchronisation signal, at least two rays of light are converted to photocurrent (240), the processed photocurrent and/or changes in the processed photocurrent are diagnosed and observed to find defects and/or determine characteristics of the said sheet of material (250).
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37. An optical measurement and inspection arrangement, comprising at least two light emitters, at least one light receiver, at least one signal generator connected to at least one light emitter and at least one light receiver and means for converting the received light to electrical current, is characterised in that,
a sheet of material (410, 510, 610, 710) is arranged between and/or in front of at least two light emitters (400, 500, 600, 700) and at least one light receiver (420, 520, 620, 720), at least two light emitters (400, 500, 600, 700) are arranged to emit at least two rays of light incident on at least one sheet, said at least two grazing, transparent and/or reflected rays of light are arranged to be detected by the same light receiver (420, 520, 620, 720), at least one ray of light is arranged to be converted to photocurrent by at least one photoelectric device (530, 630, 730) at least one signal generator is arranged to control at least one light emitter (400, 500, 600, 700) and at least one light receiver (420, 520, 620, 720) by sending them an electronic synchronisation signal and thereby synchronises the emission and detection of rays, at least one signal generator is arranged to drive at least two light emitters with different carrier frequencies, waveforms and/or phases, and at least one light receiver with both of these frequencies waveforms and/or phases, the intensity of at least one said emitted ray of light is arranged to follow a carrier waveform signal and at least one received light ray is arranged to be demodulated from the carrier waveform signal using the electronic synchronisation signal, the photocurrent and/or changes in photocurrent are arranged to be diagnosed and observed to find defects and/or determine characteristics of the said sheet of material (310).
Specification