Imaging Device Signal Processing Capacitor Variation
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Solution Overview
Problem
In imaging devices, variations in capacitance of capacitors used to hold signals can lead to inaccurate obtaining of difference signals between noise and signal charges, affecting image quality.
Innovation Solution
An imaging device with a pixel unit that outputs noise, A+N, and A+B+N signals, where these signals are converted into digital form using a single signal holding unit, allowing for accurate difference signal generation without capacitor variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the A+N signal is held in two different capacitors to obtain difference signals, then the signal processing can be performed, but variations in capacitance of the two capacitors cause inaccurate difference signal acquisition
Solution Approach 1:
The patent merges the function of holding multiple signals into a single capacitor. The first capacitor holds both the N signal and the A+N signal sequentially, eliminating the need for separate capacitors and thus avoiding capacitance variation issues. This is achieved by clearing the N signal and storing it in a register, then holding the A+N signal in the same capacitor for difference signal calculation.
Solution Approach 2:
The patent creates a digital copy of the N signal in a register instead of maintaining it in a physical capacitor. This allows the N signal to be preserved without requiring additional capacitor hardware, enabling accurate difference signal computation by comparing the digital copy with the A+N signal held in the capacitor.
2Ease of operation
If multiple capacitors are used to hold different signals, then signal processing is enabled, but capacitance variations introduce noise and operation variation components
Solution Approach 1:
The patent combines multiple signal holding functions into a single capacitor to eliminate capacitance variation issues. By sequentially storing different signals (N signal, then A+N signal) in the same capacitor and using digital registers to preserve previous values, the system maintains full signal processing capability while ensuring consistent capacitance characteristics for accurate difference signal computation.
3Measurement precision
If the same capacitor is used to hold both N signal and A+N signal, then capacitance variation is eliminated, but signal holding time and processing sequence become constrained
Solution Approach 1:
The patent performs preliminary action by clearing the N signal from the capacitor and storing it in a digital register before holding the A+N signal. This preliminary preparation ensures that when the A+N signal is stored, the capacitor is ready to hold it with consistent capacitance characteristics, enabling accurate difference signal computation without time loss due to capacitance variations.
Solution Approach 2:
The patent replaces the mechanical/electrical system of holding multiple signals in parallel capacitors with a sequential holding system using a single capacitor and digital registers. This substitution eliminates capacitance variation issues while the digital register system efficiently manages signal storage and retrieval, minimizing processing time.
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 ensures accurate conversion and subtraction of noise components from A+N and A+B+N signals, improving image quality by reducing variations due to capacitor capacitance differences.
Implementation Method 1
a pixel having a plurality of photoelectric conversion units that convert optical signals into signal charge and accumulate the signal charge
Data Source
AI summary
Conventionally, in order to obtain a difference signal between an A+N signal and an N signal and a difference signal between an A+B+N signal and the A+N signal, the A+N signal needs to be held in two different capacitors. Hence, there is a problem in that, due to variations in capacitance of the two capacitors, the difference signal between the A+N signal and the N signal and the difference signal between the A+B+N signal and the A+N signal may not accurately be obtained. An imaging device generates a signal obtained by subtracting the same digital N signal from each of the digital A+N signal and the digital A+B+N signal.