Imaging ADC Comparator Scheme for Noise and Offset Reduction
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Solution Overview
Problem
The existing imaging devices with AD converters face an issue of increased circuit scale due to the inclusion of multiple comparators, which can generate offsets when using reference signals with different gradients for analog-to-digital conversion, affecting the accuracy of digital signal generation from noise and photoelectric conversion signals.
Innovation Solution
The proposed imaging device employs a comparator that executes first, second, and third comparisons using reference signals with different changing quantities, generating digital signals based on these comparisons, and a signal processor that processes these signals to reduce noise components and offset errors, thereby decreasing the circuit scale of the AD converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple comparators are used in the AD converter, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the comparison process into three distinct comparison stages, each handling different signal components (noise signal comparison with first reference signal, noise signal comparison with second reference signal, and photoelectric conversion signal comparison with selected reference signal). This segmentation allows the single comparator to perform multiple specialized functions that would traditionally require multiple comparators, thereby reducing circuit complexity while maintaining measurement precision.
Solution Approach 2:
The patent implements periodic action by sequentially executing three comparison operations in a structured sequence: first comparing the noise signal with the first reference signal, then comparing the noise signal with the second reference signal, and finally comparing the photoelectric conversion signal with the appropriate reference signal. This periodic, sequential comparison approach enables one comparator to accomplish what would traditionally require multiple comparators operating simultaneously, thus reducing device complexity while preserving measurement accuracy.
2Measurement precision
If reference signals with different gradients are used, then measurement precision is improved, but object-generated harmful factors increase
Solution Approach 1:
The patent applies preliminary action by first comparing the noise signal with both the first reference signal (smaller gradient) and the second reference signal (larger gradient) before performing the final photoelectric conversion signal comparison. This preliminary comparison sequence allows the system to characterize the noise components under different reference signal conditions, enabling subsequent correction of offset errors in the final measurement, thereby eliminating the harmful effects of using reference signals with different gradients.
Solution Approach 2:
The patent implements feedback by using the results from the first two comparisons (noise signal versus first reference signal and noise signal versus second reference signal) to inform and correct the third comparison (photoelectric conversion signal versus selected reference signal). The digital signals generated from these comparisons are processed to compensate for offset errors, creating a feedback mechanism that eliminates the harmful effects of gradient differences in reference signals while maintaining high measurement precision.
3Measurement precision
If multiple comparisons are executed, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent maintains continuity of useful action by executing the three comparisons in an integrated, sequential manner without idle transitions. The comparator continuously processes signals through the three comparison stages, with each comparison immediately following the previous one. This continuous operation minimizes time loss while achieving the measurement precision benefits of multiple comparisons, as the system maintains productive activity throughout the conversion process rather than having intermittent pauses or reconfigurations.
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 the generation of digital signals with reduced noise components and offsets, improving the accuracy of imaging while minimizing the increase in circuit scale of the AD converter.
Implementation Method 1
a pixel configured to output a photoelectric conversion signal based on incident light
Data Source
AI summary
An imaging device includes a comparator that compares a noise signal with each of a first reference signal and a second reference signal having potentials with different changing quantities per unit time, and that compares a photoelectric conversion signal with each of the first reference signal and the second reference signal. Also, the imaging device AD-converts signals obtained by amplifying the noise signal by a first gain and a second gain having different gains, and AD-converts a signal obtained by amplifying the photoelectric conversion signal by one of a first gain and a second gain.