One-Line CIS Color Shift via Periodic RGB Illumination
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Solution Overview
Problem
Conventional image reading apparatuses using one-line contact image sensors (CIS) experience color shift and moire in RGB read-image data due to the moving print medium, which is exacerbated at lower resolutions, and addressing this issue with three-line arrays or higher resolutions increases costs or slows down the scanning process.
Innovation Solution
An image reading apparatus with a light source unit that sequentially turns on RGB light sources for a single line period, a sensor with a one-line array of image sensing elements, and a carrier unit that moves the print medium in a sub-scanning direction, ensuring the single line period is at least twice the duration of the light source ON period to minimize color mismatch and shift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a one-line array of image sensing elements is used, then manufacturing cost is reduced, but color shift and color non-uniformity occur in the read-image data
Solution Approach 1:
The patent applies periodic action by sequentially turning on red, green, and blue light sources in repeating cycles during the reading process. This periodic illumination allows each pixel to capture multiple color samples over time, enabling accurate color reproduction with a one-line array while avoiding the need for expensive three-line arrays.
2Manufacturing precision
If reading resolution is increased to suppress color shift, then color accuracy is improved, but scanning speed decreases
Solution Approach 1:
The patent uses periodic action by implementing time-sequential color sampling where RGB light sources are turned on in repeating cycles. This allows the system to maintain lower reading resolution for faster scanning while still achieving accurate color data through multiple sequential measurements at each pixel position.
Solution Approach 2:
The patent applies preliminary action by performing multiple color sampling measurements at each pixel position before final image reconstruction. The system collects R, G, and B line data through sequential light source activation, then generates accurate RGB pixel data through synthesis, allowing color correction without requiring higher spatial resolution.
3Manufacturing precision
If a three-line array of image sensing elements is used, then color shift is suppressed, but manufacturing cost increases
Solution Approach 1:
The patent replaces the spatial arrangement of a three-line array with temporal periodic action. Instead of having three simultaneous sensor lines, the system uses a single line that sequentially captures R, G, and B data through periodic light source activation, achieving the same color accuracy at lower cost.
Solution Approach 2:
The patent transitions from a spatial solution (three-line array in the vertical dimension) to a temporal solution (sequential sampling in the time dimension). This dimensional change allows the system to achieve color accuracy without increasing spatial complexity or manufacturing cost.
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 effectively suppresses color non-uniformity and moire in the RGB scanned-image data without the need for a three-line array, maintaining scanning speed and reducing manufacturing costs.
Implementation Method 1
The light sources are sequentially turned on once in a single line period to emit light of corresponding colors to irradiate a print medium with the light
Implementation Method 2
The sensor includes an array of image sensing elements that read information from the print medium irradiated with the light to generate element data
Data Source
AI summary
An image reading apparatus includes light sources, an image sensor, a data generating unit, and a carrier unit. The light sources are sequentially turned on for an identical period once in a single line period. The image sensor reads information from a print medium irradiated by the light sources. The data generating unit generates pixel data corresponding to the information. The carrier unit carries the print medium such that the image print medium is scanned by the image sensor in a sub-scanning direction. The single line period is equal to or more than twice a period from when first one of the light sources is turned on until last one of the light sources is turned off.