Image Pickup AD Conversion Linearity Correction
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Solution Overview
Problem
Existing image pickup apparatuses do not adequately address the correction of the reference potential used in successive approximation AD conversion circuits and the correction of digital signals generated through AD conversion, leading to suboptimal linearity and increased circuit complexity.
Innovation Solution
A method and apparatus that utilize a combination of successive approximation and ramp AD conversion circuits to determine higher-order and lower-order bits of digital signals, generating correction values to adjust the reference potential and correct the digital signals, thereby improving linearity and reducing circuit complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If correction of digital signal is performed, then AD conversion linearity is improved, but calculation amount increases and processing time is extended
Solution Approach 1:
The patent performs correction value calculation during a dedicated correction period before normal image signal processing. By pre-calculating correction values using test signals and storing them, the system avoids real-time calculation during image processing, thus improving linearity without extending processing time for actual images
Solution Approach 2:
The patent divides the correction process into distinct phases: a correction period for calculating correction values using test signals, and a normal processing period for converting image signals. This segmentation allows correction computations to be performed separately from image processing, preventing time extension for actual imaging operations
2Measurement precision
If two-stage AD conversion is performed, then conversion precision is improved, but discontinuities occur in input-output characteristics between adjacent subranges
Solution Approach 1:
The patent uses feedback by calculating correction values based on the relationship between first digital signals (from first stage) and second digital signals (from second stage). These correction values are then applied to compensate for discontinuities, ensuring smooth transitions between subranges while maintaining the precision benefits of two-stage conversion
Solution Approach 2:
The patent adjusts the reference potential of the successive approximation AD conversion circuit based on calculated correction values. By dynamically changing the reference potential parameter, the system compensates for discontinuities between subranges and maintains continuous input-output characteristics across the full conversion range
3Manufacturing precision
If reference potential correction is performed, then AD conversion linearity is improved, but circuit complexity increases
Solution Approach 1:
The patent introduces a correction value calculation circuit that acts as an intermediary between the two-stage AD conversion circuits. This intermediary component computes correction values based on the relationship between first and second digital signals, enabling linearity improvement through software/algorithmic correction rather than complex hardware modifications
Solution Approach 2:
The patent replaces complex hardware-based reference potential adjustment mechanisms with a computational approach. Instead of using additional analog circuitry to physically adjust reference potentials, the system uses digital correction values calculated from test signal conversions, substituting mechanical/analog complexity with digital processing
Data Source
AI summary
There are provided an image pickup apparatus, an image pickup system, and a method for driving the image pickup apparatus which perform correction of a reference potential used in an operation performed by a successive approximation AD conversion circuit and correction of a digital signal, into which a pixel signal which is output by a pixel is converted.