Printing Inspection Device Binarization Threshold Optimization

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Solution Overview

Problem

Existing printing inspection devices struggle to accurately read two-dimensional codes printed by general-purpose printers like inkjet printers due to issues with binarization threshold values, leading to potential misinterpretation of code positions and failure to decode the codes correctly.

Innovation Solution

A printing inspection device that captures images of two-dimensional codes as multi-level images, determines an optimum binarization threshold value through a read test by analyzing the maximum and minimum readable brightness values, and sets the median value as the binarization threshold for practical printing inspections.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a fixed binarization threshold is used for decoding two-dimensional codes, then the decoding process is simple and fast, but the position of cells after binarization shifts significantly, causing reading failures

Engineering Contradiction:
Improvedecoding speedVSAvoidcell position accuracy
Core Design Contradiction:
ProductivityVSMeasurement precision

Solution Approach 1:

The patent changes the binarization threshold parameter dynamically based on the actual brightness characteristics of the printed two-dimensional code. Instead of using a fixed threshold, the system calculates an optimal threshold by analyzing the brightness distribution of the captured image, thereby adapting the parameter to match the specific printing conditions and prevent cell position shifts.

Inventive Principle:
Principle #35Parameter changes

2Measurement precision

If the binarization threshold is adjusted to improve cell position accuracy, then reading accuracy improves, but the complexity of the decoding process increases

Engineering Contradiction:
Improvecell position accuracyVSAvoiddecoding process complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The system performs self-adjustment by automatically calculating the optimal binarization threshold based on the brightness characteristics of the captured two-dimensional code image. The device uses the image data itself to determine the appropriate threshold value, eliminating the need for external calibration or complex manual adjustment mechanisms.

Inventive Principle:
Principle #25Self-service

3Ease of operation

If a simple binarization method is used, then the processing is fast and simple, but it cannot handle variations in printing brightness from general-purpose printers

Engineering Contradiction:
Improveprocessing simplicityVSAvoidbrightness variation tolerance
Core Design Contradiction:
Ease of operationVSAdaptability or versatility

Solution Approach 1:

The patent performs preliminary analysis of the brightness distribution in the captured image before performing binarization. By pre-calculating the optimal threshold value based on the actual image characteristics, the system prepares the binarization parameter in advance, ensuring that the subsequent decoding process can handle various printing brightness conditions effectively.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentEP3862913B1Printing inspection device
Publication Date: 2025.05.21 HITACHI IND EQUIP SYST CO LTD
  • EP3862913B1 patent drawingFigure 1
  • EP3862913B1 patent drawingFigure 2
  • EP3862913B1 patent drawingFigure 3

AI summary

To obtain a printing inspection device that an optimum binarization threshold value in the printing inspection device that captures an image including a two-dimensional code printed by a general-purpose printer such as an ink jet printer, as a multi-level image, creates a binary image from the multi-level image with a predetermined binarization threshold value, and then performs decoding. Before a practical printing inspection is performed, a read test is performed. The read test is performed on one or more inspection samples by binarizing a multi-level image with brightness values for all gradations as a threshold value. A range (maximum value and minimum value) of readable brightness values is obtained, and then a median value between the minimum value and the maximum value is used as a binarization threshold value for a two-dimensional code image in a practical printing inspection.