Digital Column Circuitry Offset Compensation for Image Sensor Dynamic Range
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Solution Overview
Problem
Modern imaging devices face limitations due to systematic offsets introduced by analog column circuitry, which reduce the dynamic range of digital image data, making it desirable to improve imaging devices by compensating for these offsets.
Innovation Solution
The implementation of digital column circuitry that extracts and provides systematic signal offset corrections to analog column circuitry, allowing for the generation and application of analog signal offset codes to compensate for systematic biases in image data, thereby enhancing the dynamic range of digital image data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If analog column circuitry is used to readout image data, then image data can be readout from the image sensor, but systematic offsets are introduced that reduce the dynamic range of digital image data
Solution Approach 1:
The patent implements a feedback mechanism where the systematic offset is first measured during an offset measurement phase, then this measured offset value is fed back to the analog column circuitry to be subtracted from subsequently read image data, thereby compensating for the offset and restoring dynamic range
Solution Approach 2:
The patent performs offset measurement and correction value generation in advance before actual image data readout. The analog column circuitry is configured to measure its own systematic offset during a preliminary phase, and this pre-measured offset information is stored and applied to correct subsequent image data readings
2Reliability
If bits are allocated to represent the offset in digital circuitry, then the offset can be represented, but the dynamic range is limited due to bit allocation for offset representation
Solution Approach 1:
The patent extracts the systematic offset component from the image data readout process. By measuring and identifying the offset as a separate, distinct value that can be independently determined and stored, the offset is taken out from the main image data stream, allowing it to be compensated without consuming dynamic range bits that would otherwise represent image signal variations
3Measurement precision
If digital column circuitry extracts and applies offset corrections, then systematic offsets can be removed from image data, but additional circuitry complexity is introduced
Solution Approach 1:
The patent merges the offset measurement, storage, and correction functions into the existing analog column circuitry structure. The digital column circuitry is configured to work integrally with the analog column circuitry, combining their functions to achieve offset compensation without requiring entirely separate correction circuits, thereby limiting the increase in overall system complexity
Data Source
AI summary
An image sensor may be provided that includes an image pixel array, analog column circuitry and digital column circuitry. The digital column circuitry may extract a systematic analog signal offset from data received from the analog column circuitry. The digital column circuitry may generate analog signal offset correction values based on the systematic analog signal offsets and provide the analog signal offset correction values to the analog column circuitry. The analog column circuitry may remove signal offsets from subsequently read out image data from the image pixel array using the analog signal offset correction values provided by the digital column circuitry. The image pixel array may include image pixels having color filters of various colors. The digital column circuitry may generate analog signal offset correction values corresponding to each of the various colors.