Printed Image Reading with Switchable Transmitted Illumination
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Solution Overview
Problem
Existing reading devices struggle to acquire preferable read data for inspection of printed images on transparent substrates, particularly in ink jet printing systems, due to issues with visibility of non-printed regions and difficulty in contrasting white ink against the background, leading to inadequate defect detection and unevenness correction.
Innovation Solution
A reading device with both transmitted bright-field and dark-field illumination devices, controlled by a setting unit to adjust illumination conditions based on the process, allowing for optimal read data acquisition, including the use of color sensors and line sensors, and controlling the amount of emitted light to enhance reading sensitivity and defect detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transmitted dark-field illumination is used to make scratches and foreign substances less noticeable, then image quality degradation is suppressed, but defect detection capability is reduced
Solution Approach 1:
The illumination device is segmented into multiple independent illumination units: transmitted bright-field illumination devices and transmitted dark-field illumination devices. Each unit can be controlled independently to provide different illumination modes, allowing the system to switch between defect detection mode and image quality mode as needed.
Solution Approach 2:
The illumination conditions are made dynamic and adjustable based on the reading purpose. The control unit can switch between different illumination modes (bright-field and dark-field) and adjust illumination intensity according to whether the goal is defect detection or maintaining image quality, making the system adaptable to different operational requirements.
2Measurement precision
If transmitted bright-field illumination is used to enhance defect visibility, then defect detection is improved, but scratches and foreign substances become more noticeable causing image quality degradation
Solution Approach 1:
The illumination device is divided into separate bright-field and dark-field illumination units, each optimized for specific purposes. The bright-field units enhance defect visibility while dark-field units minimize scratch visibility, and they can be activated independently based on operational needs.
Solution Approach 2:
Different regions of the illumination device provide different illumination characteristics. Bright-field illumination is applied when defect detection is the priority, while dark-field illumination is applied when image quality maintenance is the priority, allowing local optimization of illumination properties for different functional requirements.
3Adaptability or versatility
If white ink is printed on transparent substrate, then printing versatility is improved, but contrast between ink and background is reduced making reading difficult
Solution Approach 1:
The illumination device can change the spectral characteristics of the illumination light to match the ink being read. By adjusting the wavelength and intensity of illumination, the system enhances the contrast between white ink and the transparent substrate, making white ink readable while maintaining support for other ink colors.
Solution Approach 2:
The illumination parameters (intensity, wavelength, direction) are adjusted based on the ink type and substrate properties. For white ink on transparent substrate, specific illumination parameters are selected to maximize contrast, while other parameters can be used for different ink types, maintaining versatility while optimizing reading accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables accurate reading and inspection of printed images on transparent substrates by effectively distinguishing ink-applied and non-ink-applied regions, reducing noise, and enhancing defect detection, even when white ink is used, thus improving the quality of read data for inspection.
Implementation Method 1
a transmitted illumination device that is disposed at a position facing a light-receiving surface of the image sensor
Implementation Method 2
an imaging lens that forms an optical image of the printed image on the image sensor and has a defined visual field representing a range in which an illumination device is disposed such that illumination light is directly incident on the imaging lens
Implementation Method 3
the light shielding plate is moved on a light diffusion plate to block illumination light incident on a lens stop
Data Source
AI summary
Provided are a reading device, a reading method, a program, an inspection device, and a printing system that can acquire preferred read data of a printed image for inspection or the like using the read data of the printed image. A reading device includes an image sensor, an imaging lens, a transmitted illumination device including a transmitted bright-field illumination device and a transmitted dark-field illumination device, and a transmitted illumination condition setting unit that sets transmitted illumination conditions according to a process performed on read data, and controls each of the transmitted bright-field illumination device and the transmitted dark-field illumination device according to transmitted illumination conditions.