Variable Gain Amplifier Automatic Gain Control for Image Scanners
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Solution Overview
Problem
Existing image scanning devices face challenges in accurately adjusting the amplifier gain due to noise influences when scanning a reference white plate with dust or flaws, leading to potential output saturation and increased start-up time.
Innovation Solution
An image scanning device with a variable gain amplifier and digital amplifier, where the amplifier gain is initially set based on first digital image data from a reference white plate, and adjusted by decreasing the gain if the highest value exceeds a predetermined range, reducing the need for multiple scans and minimizing noise impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple scans of the reference white plate are performed to reduce noise influence, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent performs a preliminary scan of the reference white plate to obtain initial digital image data, then uses this data to set the amplifier gain before actual document scanning begins. This preliminary action allows the system to prepare the optimal gain setting in advance, avoiding the need for multiple scans during operation and thus reducing start-up time while ensuring accurate gain adjustment.
2Productivity
If the amplifier gain is set high to maximize output dynamic range, then productivity is improved, but reliability worsens due to output saturation from noise peaks
Solution Approach 1:
The patent implements a feedback mechanism where the system scans the reference white plate, detects the highest value in the obtained digital image data, compares it with a predetermined threshold, and adjusts the amplifier gain accordingly. This feedback loop ensures that the gain is optimized to maximize the output dynamic range while preventing output saturation caused by noise peaks or dust on the reference plate, thus maintaining both productivity and reliability.
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 quick and accurate adjustment of the amplifier gain, reducing the risk of output saturation and decreasing the time required for automatic gain control, thereby enhancing the reliability and efficiency of the image scanning process.
Implementation Method 1
a line sensor for converting a line image into an electric signal (analog image signal)
Data Source
AI summary
An image scanning device includes an image sensor obtaining an analog image signal; a variable gain amplifier amplifying the analog image signal; an analog-to-digital converter converting the amplified analog image signal into digital image data; a highest value detection unit detecting the highest value in the digital image data; and an amplifier gain setting unit setting an amplifier gain of the variable gain amplifier. The amplifier gain setting unit initially sets the amplifier gain of the variable gain amplifier such that the highest value in first digital image data of a reference image falls within a predetermined range, and if the highest value in second digital image data of the reference image obtained with the initially-set amplifier gain exceeds the predetermined range, the amplifier gain setting unit decreases the amplifier gain of the variable gain amplifier.