CMOS Pixel Signal Reading and OB Correction for Focus Accuracy
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Solution Overview
Problem
Current imaging apparatuses with CMOS sensors face challenges in efficiently performing focus detection and image generation due to limitations in signal processing and correction methods, particularly in handling signals from different photodiodes for accurate focus control and image quality.
Innovation Solution
The imaging apparatus incorporates a pixel region with unit pixels having first and second photoelectric conversion units, a reading controller for mixed signal reading modes, and an optical black (OB) clamp processor to correct signals based on light shielding region outputs, enabling effective focus detection and image generation by adjusting signals according to imaging conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signals from multiple photodiodes are read separately for focus detection, then focus detection accuracy is improved, but reading time increases
Solution Approach 1:
The pixel array is divided into a first region for focus detection and a second region for image generation. The reading controller reads signals from the first region in a first reading mode (separately from multiple photodiodes) and from the second region in a second reading mode (mixed signals), thereby segmenting the reading process to achieve both accurate focus detection and efficient image generation without reading all signals from all regions in full detail.
Solution Approach 2:
The patent applies partial action by reading signals only from the first region (focus detection region) with high precision separate photodiode reading, while reading mixed signals from the second region (image generation region). This partial detailed reading approach achieves sufficient focus detection accuracy without the time cost of separately reading all photodiodes in the entire pixel array.
2Manufacturing precision
If optical black region signals are used for correction, then image quality is improved, but device complexity increases
Solution Approach 1:
The optical black pixels within the pixel array itself generate correction signals that are used to correct the image signals. The system uses its own internal resources (optical black regions) to perform correction, eliminating the need for external correction devices or complex additional processing hardware, thereby improving image quality without proportionally increasing device complexity.
3Productivity
If separate reading modes are implemented for different regions, then focus detection and image generation efficiency are improved, but device complexity increases
Solution Approach 1:
The reading controller is designed with multi-functionality to handle both first reading mode (for focus detection) and second reading mode (for image generation) through a single unified component. This universal reading controller can switch between different reading modes and processes signals from different regions according to different requirements, thereby achieving improved processing efficiency without requiring separate dedicated reading devices for each function, thus limiting the increase in device complexity.
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 configuration enhances focus detection accuracy and image quality by correcting signal offsets and noise, reducing reading time and improving image continuity, while allowing for efficient operation in various imaging conditions.
Implementation Method 1
each of the unit pixels including first and second photoelectric conversion units
Data Source
AI summary
An imaging apparatus includes a pixel region having a plurality of unit pixels arranged in a matrix, each of the unit pixels including first and second photoelectric conversion units, a reading controller configured to read first signals obtained by mixing signals output from the first and second photoelectric conversion units in rows of a first reading mode and read second signals at least including signals of the first photoelectric conversion units and third signals at least including signals of the second photoelectric conversion units in rows of a second reading mode, and an OB clamp processor configured to correct signals in the unit pixels included in an opening region in the pixel region based on signals output from the unit pixels included in a light shielding region in the pixel region. The OB clamp processor performs one of various correction processes depending on an imaging condition.