Print Media Inspection Layout for Stray Light Isolation
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Solution Overview
Problem
Existing image inspection techniques for print media suffer from measurement inaccuracies due to stray light interference between the imager and color measuring unit, particularly when both units are positioned to face the same roller, leading to reduced measurement accuracy.
Innovation Solution
The imager and color measuring unit are arranged oppositely with respect to the print medium, and a light-shielding part is placed between them to prevent stray light from entering the color measuring unit, ensuring no member contacts the image-bearing surface between the rollers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the imager and color measuring unit are arranged to face the same roller, then the device complexity is reduced, but measurement precision deteriorates due to stray light interference
Solution Approach 1:
The patent divides the inspection system into two separate measurement positions: one for imaging and one for color measurement. Each position faces a different roller, physically segmenting the measurement paths to eliminate stray light interference between the imager and color measuring unit.
Solution Approach 2:
A light-shielding part is introduced as an intermediary element between the imager and the color measuring unit. This light-shielding part blocks stray light from the imager from reaching the color measuring unit, thereby protecting the measurement precision without requiring complete spatial separation of the devices.
2Measurement precision
If a roller is arranged between the imager and color measuring unit to shield stray light, then measurement precision improves, but the image may be altered due to contact with the roller
Solution Approach 1:
Instead of using a roller as the light-shielding intermediary, the patent employs a dedicated light-shielding part that does not contact the print medium. This intermediary element blocks stray light while leaving the image-bearing surface untouched, preserving image integrity.
Solution Approach 2:
The light-shielding function is extracted from the roller and assigned to a separate light-shielding part. This extraction allows the roller to maintain its primary function of supporting and transporting the print medium without the secondary function of light shielding that would cause image alteration.
3Measurement precision
If the color measuring unit operates with prescribed illumination, then measurement precision is maintained, but stray light from the imager reduces measurement accuracy
Solution Approach 1:
A light-shielding part is positioned between the imager and the color measuring unit to block stray light from the imager. This intermediary element protects the color measuring unit's light receiver from receiving unwanted illumination, ensuring that only the prescribed illumination light from the color measuring unit's own light source reaches the print medium and is measured.
Solution Approach 2:
The patent acknowledges the presence of stray light from the imager as an inevitable byproduct of the imaging operation. Instead of trying to eliminate the imager's light source, the solution converts this potentially harmful stray light into a controlled situation by using the light-shielding part to direct it away from the color measuring unit, allowing both imaging and color measurement to coexist.
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
This configuration maintains high measurement accuracy by preventing stray light interference and image alteration, allowing for precise image inspection on print media.
Implementation Method 1
a light-shielding part which is arranged between the imager and the light receiver on a side of the first main surface of the print medium stretched over the first roller and the second roller and configured to shield light from the imager toward the light receiver
Implementation Method 2
receive reflected light from an imaging region of a region where the first illumination light enters and capture an image of the imaging region
Implementation Method 3
receive light reflected from a color detection region of a region where the second illumination light enters by a light receiver and conduct color detection on the color detection region
Data Source
AI summary
An image inspection apparatus supports a print medium in a state that the print medium is stretched over a first roller and a second roller. The image inspection apparatus includes an imager, a color measuring part and a light-shielding member. The imager illuminates the print medium in an area wound on the first roller, receives reflected light and captures an image. The color measuring part illuminates the print medium in an area wound on the second roller, receives reflected light by a light receiver and conducts color detection on the color detection region. The light-shielding part is arranged between the imager and the light receiver on a side of a first main surface of the print medium stretched over the first roller and the second roller and configured to shield light from the imager toward the light receiver.