Luminance-to-Density Conversion for Dual-Range Calibration
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Solution Overview
Problem
Conventional image forming apparatuses struggle to accurately detect density unevenness due to a limited density signal range and resolution, which affects the tone characteristic of the formed images, especially when transitioning from low to high densities.
Innovation Solution
The apparatus employs an image forming unit, sensor, amplifier, and controller to form test images for calibration, adjusting gain levels to amplify signals for both tone and density unevenness corrections, using specific luminance-density conversion tables to enhance resolution and range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the density signal range is widened to cover low to high density measurement images, then the tone characteristic detection is improved, but the resolution for detecting density unevenness in a specific density range is decreased
Solution Approach 1:
The patent divides the density measurement into two separate processes: tone characteristic measurement (low to high density range) and density unevenness measurement (specific density range only). Each process uses dedicated conversion characteristics optimized for its specific purpose, allowing both wide range coverage and high resolution within the respective ranges without compromise
Solution Approach 2:
The patent applies different conversion characteristics tailored to specific measurement purposes. For tone characteristic detection, a conversion characteristic optimized for wide density range is used. For density unevenness detection, a separate conversion characteristic optimized for high resolution in a specific density range is used. This local optimization ensures each measurement task receives the appropriate processing parameters
2Device complexity
If a single conversion characteristic is used for all density ranges, then the device complexity is reduced, but the ability to detect both tone characteristic and density unevenness with high accuracy is compromised
Solution Approach 1:
The patent segments the measurement process into distinct tone characteristic measurement and density unevenness measurement phases, each with its own dedicated conversion characteristics. This segmentation allows accurate detection of both parameters while managing complexity through clear process separation rather than attempting to handle all cases with a single complex conversion system
3Measurement precision
If the density detection range is narrowed to a specific density range for high resolution measurement, then the resolution for density unevenness detection is improved, but the overall tone characteristic detection capability is limited
Solution Approach 1:
The patent performs tone characteristic measurement first across the full density range (low to high density), then performs density unevenness measurement in a specific density range with higher resolution. This sequential segmentation allows the system to achieve both wide range coverage and high resolution without requiring a single measurement process to optimize for both simultaneously
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 allows for precise detection of density unevenness with high accuracy, ensuring consistent image quality by expanding the density signal range and resolution, thereby improving the tone characteristic of the output images.
Implementation Method 1
a sensor configured to receive reflected light from a test image formed by the image forming unit and output a signal based on a result of receiving the reflected light
Implementation Method 2
an amplifier configured to amplify the signal outputted from the sensor based on a gain
Data Source
AI summary
An apparatus forms a test image for a first density calibration, amplifies a first signal from a sensor based on a result of receiving a reflected light from a test image for the first density calibration, and performs the first density calibration based on the amplified first signal by an amplifier. The apparatus forms a test image for a second density calibration, amplifies a second signal from the sensor based on a result of receiving a reflected light from the test image for the second density calibration, and performs the second density calibration based on the amplified second signal by the amplifier. A gain of the second signal is higher than that of the first signal.