EP0194331A1
Expired / Lapsed
EP
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Inspecting device for print
Assignee: Mitsubishi Heavy Industries Ltd
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Filing: 1985-03-14
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Granted: —
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Expires: 2005-03-14
Abstract
Abstract The present invention relates to an inspecting device for a print which can scan the entire print pattern (3') of a printed sheet (3) by an optical detecting device (8), detects the image information of the print pattern (3') at every pixel, calculates the difference between the detected image information with reference information, delays the differential signal in several pixels in the scanning direction of the optical detecting device (8), calculates the difference between the differential signal and the delayed differential signal, sets a threshold level to the twice differential signal produced from the result, and judges the production of a printing defect when the twice differential signal exceeds the threshold level, thereby accurately detecting the printing defect even when the entire variation in the color density occurs on the printed sheet (3).
Inventors
- 👤 Toshiro Masuda
- 👤 Toshiji Fujita
- 👤 Kouichi Ishizuka
- 👤 Yoshio Kinoshita
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-24 17:35
CPC Classifications
B; B41; B41F; B41F33/00; B41F33/0036; G; G01; G01N; G01N21/00; G01N21/84; G01N21/88; G01N21/95; G01N21/956; H; H04; H04N; H04N1/00; H04N1/00002; H04N1/00026; H04N1/00037
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
212 words
An inspecting device for a print for inspecting a printing defect occurred on a print pattern of a printed sheet characterized by comprising an optical detecting device (8) for detecting image information at every pixel by optically scanning the print pattern (3') of the printed sheet (3) in a direction perpendicularly to the feeding direction of the printed sheet (3), reference information storing means (15) for storing the image information at every pixel of the print pattern of the normal printed sheet as reference information, first differential calculating means (101) for calculating the difference between the detected image information and the reference information, delay means (103) for delaying the differential signal produced by said first differential means (101) by several pixels in the scanning direction of said optical detecting device (8), second differential calculating means (102) for calculating the difference between the differential signal produced by said first differential calculating means (101) and the differential signal delayed and produced by said delay means (103), and comparing means (105) for comparing the differential signal produced by said second differential calculating means (102) with a predetermined allowable value to output an error signal for meaning the production of a printing defect on the print pattern (3') when the differential signal exceeds the allowable range.
Claim 2
Dependent Claim
212 words
An inspecting device for a print for inspecting a printing defect occurred on a print pattern of a printed sheet characterized by comprising an optical detecting device (8) for detecting image information at every pixel by optically scanning the print pattern (3') of the printed sheet (3) in a direction perpendicularly to the feeding direction of the printed sheet (3), reference information storing means (15) for storing the image information at every pixel of the print pattern of the normal printed sheet as reference information, first differential calculating means (101) for calculating the difference between the detected image information and the reference information, delay means (103) for delaying the differential signal produced by said first differential means (101) by several pixels in the scanning direction of said optical detecting device (8), second differential calculating means (102) for calculating the difference between the differential signal produced by said first differential calculating means (101) and the differential signal delayed and produced by said delay means (103), and comparing means (105) for comparing the differential signal produced by said second differential calculating means (102) with a predetermined allowable value to output an error signal for meaning the production of a printing defect on the print pattern (3') when the differential signal exceeds the allowable range.
Claim 3
Dependent Claim
77 words
An inspecting device for a print according to claim 1, characterized by further comprising accumulating means (106) for accumulating the differential signal produced by said first differential calculating means (101), and comparing means (108) for comparing the accumulation signal produced by said accumulating means (106) with a predetermined allowable value to output an error signal for production of the entire variation in color density on the print pattern (3') when the accumulation signal exceeds the allowable range.
Claim 4
Dependent Claim
23 words
An inspecting device for a print according to claim 1, characterized in that said optical detecting device (8) is a line sensor camera.
Claim 5
Dependent Claim
22 words
An inspecting device for a print according to claim 3, characterized in that said line sensor camera is a CCD line sensor.
Claim 6
Dependent Claim
22 words
An inspecting device for a print according to claim 3, characterized in that said line sensor camera is a MOS line sensor.
Claim 7
Dependent Claim
23 words
An inspecting device for a print according to claim 3, characterized in that said line sensor camera is a close contact line sensor.
Claim 8
Dependent Claim
64 words
An inspecting device for a print according to claim 1, characterized in that an optical filter (10) having a transmission factor larger in the spectral transmission factor in a wavelength band of 400 nm to 500 nm than that in other visible light wavelength band of 500 nm to 700 nm is disposed between said optical detecting device (8) and the printed sheet (3).
Claim 9
Dependent Claim
103 words
An inspecting device for a print according to claim 1, characterized by further comprising timing control means (200) for correcting the scan starting timing of the print pattern of next set by calculating the averaged value of the displacements of synchronization per one print pattern of the printed sheets with a plurality of print patterns as a set and feeding back the value, and averaging means (300) for averaging the image information of continuous two or more sheets produced by scanning at the corrected timing, thereby inputting the averaged information as the information to be inspected to said first differential calculating means (101).
References Cited (Backward Citations)
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