Image Reader Show-Through Prevention Using Complementary Light
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Solution Overview
Problem
Existing image readers face challenges in preventing show-through from light reflected by the back-side image during double-side reading, as they cannot avoid the influence of light reflected from the back side without using a photoelectric transducer configured to receive only specific colors.
Innovation Solution
The image reader employs a configuration with a first and second light emitting unit emitting different complementary colors, and a light receiving unit that receives light from both emitting units, allowing it to output read image data by controlling the light sources to emit mutually complementary colors, thereby minimizing the impact of light reflected from the back-side image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a photoelectric transducer configured to receive only light of a specific color is used, then the influence of show-through from the back side can be reduced, but the device complexity increases and the ability to read full-color images is compromised
Solution Approach 1:
The patent changes the parameter of light color by using complementary colors (e.g., red and cyan, green and magenta, blue and yellow) for the two light sources. This allows the light receiving unit to receive both transmitted light (from the opposite side) and reflected light (from the same side) simultaneously, and through image processing, separate the front-side and back-side images effectively without requiring color-selective photoelectric transducers
Solution Approach 2:
The patent introduces image processing as an intermediary step that receives the combined light signals containing both transmitted and reflected components, then separates and reconstructs the front-side and back-side images. This intermediary processing resolves the contradiction by handling the show-through problem computationally rather than requiring complex hardware filtering
2Object-affected harmful factors
If the light receiving unit receives only reflected light from the front side, then show-through is avoided, but the light intensity and reading accuracy are reduced
Solution Approach 1:
Image processing acts as an intermediary that separates the mixed light signals containing both reflected light (useful for reading the front side) and transmitted light (causing show-through). By processing the combined signals, the system extracts the front-side image information while eliminating the show-through effect, thereby maintaining high reading accuracy without sacrificing light intensity
Solution Approach 2:
By using complementary colors for the two light sources, the patent creates distinct spectral signatures for transmitted and reflected light paths. The image processing then utilizes these parameter differences to separate the light components, allowing the system to utilize the full light intensity while maintaining accurate front-side image reading
3Object-affected harmful factors
If complementary colors are used for the two light sources, then show-through from the back side is prevented, but the device complexity increases due to additional light source control
Solution Approach 1:
The patent uses complementary colors (red-cyan, green-magenta, blue-yellow) for the two light sources, which creates distinct spectral characteristics that are easily distinguishable by the light receiving unit. This parameter change allows simple temporal or spectral separation of the light signals without requiring complex control mechanisms, as the complementary color relationship provides natural differentiation
Solution Approach 2:
The patent implements periodic emission of light from the two light sources, where each light source emits light in alternating time intervals. This periodic action, combined with the complementary color scheme, allows the light receiving unit to distinguish between transmitted and reflected light paths through timing and color information, reducing the need for complex continuous control systems
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 approach effectively prevents show-through from light reflected by the back-side image without requiring photoelectric transducers sensitive to specific colors, enabling accurate color image reading by ensuring that the light receiving unit receives combined achromatic light, reducing the influence of transmitted and reflected light.
Implementation Method 1
a first light emitting unit configured to emit light toward a first side of a document sheet that is in a predetermined reading area, a second light emitting unit configured to emit light toward a second side of the document sheet
Implementation Method 2
a first light receiving unit configured to receive light emitted by the first light emitting unit and then reflected by the document sheet
Implementation Method 3
light emitted by the second light emitting unit and then transmitted through the document sheet
Implementation Method 4
each contact image sensor includes a light source and a photoelectric transducer for each color of RGB
Data Source
AI summary
An image reader is provided, which includes a first light emitting unit emitting light toward a first side of a document sheet in a predetermined reading area, a second light emitting unit emitting light toward a second side of the document sheet in the predetermined reading area, a first light receiving unit receiving light emitted by the first light emitting unit and reflected by the document sheet and light emitted by the second light emitting unit and transmitted through the document sheet, and a controller that controls the first light emitting unit to emit light of a first color, controls the second light emitting unit to emit light of a second color, the first and second colors being mutually complementary colors, and controls the first light receiving unit to output read image data of the document sheet based on a light receiving result of the first light receiving unit.