US 5,305,392 AGranted

High speed, high resolution web inspection system

AssigneePhilip Morris Incorporated

InventorsH. Cary Longest, Jr., Robert H. Moffitt, W. Randolph Sweeney

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Abstract

A modular system and method using the system for the high speed high resolution inspection of printed webs are provided. Each module inspects one lane of a printed web for print defects. Each gray scale or bipolar gray scale gradient pixel value of a digitally converted input image is compared to the minimum and maximum threshold values of the image template by a real-time digital signal processor. The image template is created in a secondary non-real-time processor by producing a statistical representation of a number of input images. The image template is desensitized to longitudinal and transverse jitter of the printed web so that jitter is not identified by the system as a print defect. The user is signaled if actual print defects exist and the lanes in which the defects exist are identified.

Claims10

Dependent claims

For use in a modular system for the inspection of the lanes of a printed web, said system having analog image input means, analog-to-digital conversion means, primary real-time digital signal processing means and secondary non-real-time processing means, a method for detecting flaws in a printed web, said method comprising the steps of:

inputting an analog representation of each pixel of a line of an input image from a printed web;
converting the analog representation to a gray scale digital representation;
transferring the digital representation of each line to the primary digital signal processing means;
generating pre-stabilization offsets for the digital representation in the primary digital signal processing means;
transferring the digital representation of a collection of lines comprising an image to the secondary processing means;
creating in the secondary processing means a statistical representation of the gray scale values for each pixel from a set of input images;
calculating in the secondary processing means the minimum and maximum threshold values for a jitter desensitized template;
transferring the template to the primary digital signal processing means;
and
comparing input images to the template in the primary digital signal processing means.

7 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/002,892Filed 11 Jan 1993
Granted: 19 Apr 1994
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

B41F 33/0036
Indicating, counting, warning, control or safety devices: devices for scanning or checking the printed matter for quality control
G01N 21/89
Investigating the presence of flaws or contamination: in moving material, e.g. running paper or textiles
G01N 21/956
Characterised by the material or shape of the object to be examined: inspecting patterns on the surface of objects
G01N 2021/8861
Grading and classifying of flaws: determining coordinates of flaws