Solid-state imaging gain error correction circuit
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Solution Overview
Problem
Existing solid-state imaging apparatuses face challenges in maintaining an improved signal-to-noise (S/N) ratio and dynamic range due to gain errors and AD conversion errors caused by different signal processing gains, leading to image degradation and increased complexity in circuit configuration.
Innovation Solution
A solid-state imaging apparatus with a column amplifying unit for each column of pixels, an analog-to-digital converter, a comparing unit for level-shifting and detecting gain errors, and a correction unit to adjust signals based on detected errors, enabling accurate gain error detection and correction to improve S/N ratio and dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a detection circuit is provided for each column to detect pixel signals and perform gain control, then signal saturation is avoided and S/N ratio is improved, but circuit configuration becomes more complicated and device area increases
Solution Approach 1:
Multiple detection circuits are merged into a single detection circuit that processes signals from all columns. The patent combines the detection functions of all columns into one shared circuit, eliminating the need for separate detection circuits in each column while maintaining signal saturation avoidance through centralized gain control.
Solution Approach 2:
A single detection circuit is designed to handle multiple functions: detecting signals from all columns, performing gain control for multiple columns, and managing both small-amplitude and large-amplitude signals. This universal circuit replaces multiple specialized circuits, reducing overall device complexity while maintaining reliability.
2Adaptability or versatility
If signals are amplified at different gains by column amplifying units, then dynamic range is increased, but gain errors and AD conversion errors occur leading to image degradation
Solution Approach 1:
The patent implements a feedback mechanism where the detection circuit monitors the actual gain applied to signals and provides correction information back to the amplifying units. This feedback loop enables real-time gain error detection and correction, ensuring that signals amplified at different gains are accurately adjusted to maintain manufacturing precision while preserving extended dynamic range.
Solution Approach 2:
The system dynamically changes gain parameters based on signal amplitude characteristics. The detection circuit identifies whether signals are small-amplitude or large-amplitude and adjusts amplification parameters accordingly. This parameter adaptation allows the system to maintain high precision across different gain levels while preserving the benefits of extended dynamic range.
3Reliability
If gain control is performed for each column independently, then small-amplitude signals are not saturated, but pixels exhibit different S/N ratios
Solution Approach 1:
The patent applies equipotentiality by ensuring that all pixel signals, regardless of their initial amplitude or column origin, are adjusted to a consistent reference level through the centralized detection circuit. This circuit uniformly controls gain across all columns, creating equal signal conditions that result in consistent S/N ratios while preventing saturation of small-amplitude signals.
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
The solution effectively reduces noise in small-amplitude signals and enhances image quality by correcting gain errors, resulting in improved S/N ratio and dynamic range while simplifying the circuit configuration and reducing the physical size of the apparatus.
Implementation Method 1
a plurality of pixels arranged in a matrix for generating a signal by a photoelectric conversion
Data Source
AI summary
A solid-state imaging apparatus comprising a plurality of pixels generating a photoelectric conversion signal, a column amplifying unit corresponding to columns of the pixels, for outputting a first and second signals generated by amplifying the photoelectric conversion signal at a smaller first gain and larger second gain respectively, an analog to digital converter (21) for converting the first and second signals from an analog signal to a digital signal, a comparing unit (224) for inputting the digital signal from the analog to digital converter, level-shifting into the same gain level the first and second signals converted by the analog to digital converter, and thereafter detecting a gain error between the level-shifted first and second signals, and a correction unit (226) for correcting the first and second signals based on the gain error.