Two-Stage Signal Range Adjustment for Saturation-Free Image Scanning
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Solution Overview
Problem
Image scanning devices face challenges in preventing saturation during the scanning of high and low density images, as existing methods rely on discrete gain adjustments and conversion tables, which are insufficient for accurate sensitivity switching and gradation preservation.
Innovation Solution
A signal processing device comprising a first sensitivity adjuster (PGA) for coarse adjustment and a second sensitivity adjuster (A/D converter) for fine adjustment, along with a digitizer, which coarsely and finely adjusts the signal output range and digitizes the signal to generate a digital output, effectively utilizing the dynamic range of the A/D converter by changing the reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If discrete gain adjustments and conversion tables are used for sensitivity switching, then the device complexity is reduced, but the measurement precision and ability to prevent saturation are insufficient
Solution Approach 1:
The sensitivity adjustment function is segmented into two independent adjusters: a first adjuster for coarse adjustment and a second adjuster for fine adjustment. This segmentation allows each adjuster to operate within an optimized range, achieving high precision without requiring a complex single-stage adjustment mechanism.
Solution Approach 2:
The system dynamically switches between coarse and fine adjustment modes based on the signal characteristics. The first adjuster handles large-range adjustments when needed, while the second adjuster takes over for precision tuning, creating a dynamic adaptation mechanism that maintains simplicity while achieving high precision.
2Productivity
If a single adjuster is used for sensitivity adjustment, then the device complexity is reduced, but the ability to effectively utilize the dynamic range of the A/D converter is limited
Solution Approach 1:
The dynamic range adjustment is segmented into coarse and fine components. The first adjuster covers the broad dynamic range requirements, while the second adjuster optimizes the utilization of the A/D converter's full range, ensuring maximum productivity without saturation.
Solution Approach 2:
The system changes the output range parameter of the signal through coordinated adjustment of both adjusters. The first adjuster sets the primary output range, and the second adjuster fine-tunes it to match the A/D converter's optimal input range, maximizing conversion efficiency and dynamic range utilization.
3Manufacturing precision
If coarse adjustment only is used, then the device complexity is reduced, but the gradation accuracy and saturation prevention in high and low density images are insufficient
Solution Approach 1:
The adjustment mechanism is segmented into two stages: coarse adjustment for overall signal level control and fine adjustment for gradation precision. This segmentation enables accurate gradation representation in both high and low density images without requiring an overly complex single-stage system.
4Measurement precision
If fine adjustment only is used, then the measurement precision is improved, but the ease of operation and response time are reduced
Solution Approach 1:
The adjustment process is segmented into rapid coarse adjustment followed by precise fine adjustment. The first adjuster provides quick response for major changes, while the second adjuster delivers precision when needed, combining speed and ease of operation with measurement precision.
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 adjustment of sensitivity, preventing saturation and ensuring accurate gradation across a wide range of image densities, enhancing the scanning performance by effectively utilizing the dynamic range of the A/D converter.
Implementation Method 1
charge-coupled devices (CCD) and complementary metal oxide semiconductor (CMOS) sensors to convert reflected light (optical signals) from a scanned document into electrical signals
Data Source
AI summary
A signal processing device includes a first adjuster, a second adjuster, and a digitizer. The first adjuster coarsely adjusts an output range of a signal input to the first adjuster to output a first signal. The second adjuster adjusts an output range of a signal more finely than the first adjuster adjusts to output a second signal. The digitizer digitizes the first signal or the second signal to output a digital signal. The digital signal has an output range of a signal that is finely adjusted with the second adjuster after being coarsely adjusted with the first adjuster.