Capacitive AD Conversion Circuit for Low-Noise Endoscope Imaging
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Solution Overview
Problem
Analog-to-digital (AD) conversion in imaging devices, particularly in endoscope systems, faces challenges with noise degradation due to the analog output of Charge-Coupled Device (CCD) type imaging devices, leading to reduced image quality. This is exacerbated by the need for smaller device sizes, which complicates the integration of effective AD conversion methods.
Innovation Solution
The proposed AD conversion device incorporates a comparison circuit, upper-level and lower-level digital-to-analog (DA) conversion circuits, and a level shift circuit, utilizing capacitance elements with weighted values to perform successive approximation and level shifting operations, generating digital data based on voltage level differences and correcting digital data through a correction device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CCD type imaging device is used, then image quality is maintained, but noise degradation occurs due to analog output and longer scope length
Solution Approach 1:
The patent replaces the mechanical/analog signal transmission system with a digital system. Specifically, it introduces an AD conversion circuit that converts analog signals to digital signals, and uses digital ramp signals for level measurement. This substitution eliminates analog noise degradation while maintaining measurement precision, directly resolving the contradiction between image quality and noise interference.
2Object-affected harmful factors
If digital-output CMOS type imaging device is used, then noise degradation is reduced, but device size becomes smaller making AD conversion integration complex
Solution Approach 1:
The patent segments the AD conversion process into distinct functional modules: a comparison circuit for analog-to-digital conversion, a digital ramp signal generation unit, and a correction device. This segmentation allows each module to be optimized independently and integrated into the compact CMOS imaging device structure, reducing the complexity of AD conversion integration while maintaining low noise performance.
3Measurement precision
If successive approximation AD conversion is used, then conversion accuracy is improved, but conversion time increases
Solution Approach 1:
The patent implements preliminary action by pre-generating digital ramp signals that correspond to various voltage levels before the actual AD conversion is needed. These pre-prepared digital ramp signals are stored and readily available when conversion is required. This eliminates the time-consuming iterative process of traditional successive approximation conversion, achieving both high accuracy and fast conversion speed.
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 solution enhances the accuracy and efficiency of AD conversion, reducing noise interference and improving image quality by effectively converting analog signals to digital, thereby addressing the size and noise-related issues in imaging devices.
Implementation Method 1
The upper-level DA conversion circuit includes a plurality of capacitance elements electrically connected to the second terminal. Capacitive values of the plurality of capacitance elements are weighted by binary numbers.
Data Source
AI summary
An AD conversion device includes a comparison circuit, an upper-level DA conversion circuit, a level shift circuit, a lower-level DA conversion circuit, and a correction device. The comparison circuit includes a first terminal and a second terminal. The comparison circuit is configured to compare a first voltage level of a signal input to the first terminal with a second voltage level of a signal input to the second terminal. The upper-level DA conversion circuit includes a plurality of capacitance elements electrically connected to the second terminal. Capacitive values of the plurality of capacitance elements are weighted by binary numbers. The level shift circuit includes one or more capacitance elements electrically connected to the second terminal. The lower-level DA conversion circuit includes a plurality of capacitance elements electrically connected to the second terminal.