Image Forming Apparatus Color Adjustment via Sensor Correction
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Solution Overview
Problem
Current color adjustment techniques in inkjet printers face challenges in accurately correcting sensor reading characteristics, leading to density unevenness due to variations in sensor and illumination angles, and difficulties in matching colorimetric and scanned data, especially when high-frequency patterns are involved.
Innovation Solution
The proposed solution involves an image forming apparatus with a printing unit, a scan unit, and a colorimetry unit that generate correction information and color adjustment information by correlating pixel positions in scanned data with colorimetric data, using a specific chart configuration with patches and position adjustment patterns to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If colorimetry is performed manually or with low-resolution devices, then the measurement process is simpler and faster, but the correspondence between colorimetric data and scanned data is not established accurately, leading to insufficient correction
Solution Approach 1:
The patent applies preliminary action by pre-forming position adjustment patterns (such as ruler marks or edge patterns) on the test chart before colorimetry and scanning. These patterns enable the system to pre-establish the correspondence relationship between colorimetry positions and scanned pixel positions, allowing accurate correction without complex real-time alignment procedures during actual measurement.
Solution Approach 2:
The patent uses position adjustment patterns as an intermediary element that bridges the gap between colorimetry data and scanned data. These patterns serve as reference markers that can be detected by both the colorimeter and the scanner, enabling accurate registration and correspondence between the two different measurement systems without requiring complex direct coordination between them.
2Measurement precision
If a mark (blank portion) is inserted into a patch to cause colorimetric data and scanned data to correspond to each other, then the correspondence accuracy improves, but the correction accuracy decreases when high-frequency patterns exist
Solution Approach 1:
The patent segments the test chart into multiple functional regions: uniform density patches for colorimetry measurement, position adjustment patterns for registration, and high-frequency pattern regions for correction validation. This segmentation allows each region to serve its specific purpose without interfering with others, enabling accurate correspondence establishment while preserving correction accuracy for high-frequency patterns through separate dedicated measurement areas.
Solution Approach 2:
The patent applies local quality by creating different types of patterns in different regions of the test chart. Uniform density patches are placed in regions where colorimetry measurement is needed, while position adjustment patterns and high-frequency patterns are placed in other regions. This localized differentiation ensures that each measurement type can be performed optimally in its designated area without compromising the other.
3Manufacturing precision
If sensor reading characteristics are obtained by scanning a test chart, then the head shading correction can be performed, but variations in sensor reading characteristics due to angle dependence cause density unevenness
Solution Approach 1:
The patent implements feedback by measuring the actual sensor reading characteristics through scanning the test chart with position adjustment patterns, comparing these measurements against the intended colorimetric values, and using the differences to generate correction data. This feedback loop allows the system to automatically adjust and compensate for angle-dependent variations in sensor reading characteristics, achieving accurate head shading correction despite the underlying physical limitations.
Data Source
AI summary
Based on scanned data obtained by a scan unit reading a first chart printed and output by a printing unit and colorimetric data obtained by a colorimetry unit measuring the first chart, correction information for correcting a sensed value of the scan unit is generated. The first chart includes a patch extending in a main scanning direction substantially perpendicular to a sheet conveyance direction and having a uniform density, and a position adjustment pattern formed outside the patch for identifying a position in the main scanning direction on the patch. A first generation unit generates the correction information by causing a pixel position of an end portion of the patch in the scanned data and a colorimetry position of an end portion of the patch in the colorimetric data to correspond to each other and determining a corrected value of the sensed value at a specific pixel position.