Image Sensor Signal Synthesis for Phase Detection
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Solution Overview
Problem
Existing image capturing apparatuses face challenges in performing on-imaging plane phase difference focus detection when dynamic range is expanded, particularly due to the presence of saturated signals which affect the accuracy of focus detection.
Innovation Solution
The apparatus employs an image sensor with multiple photoelectric conversion units per pixel, generating and processing signals with different gains to produce added and averaged signals, which are then synthesized using specific ratios. A determination unit adjusts these ratios to mitigate the impact of saturated signals, enabling accurate phase difference focus detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HDR composition is performed using multiple image signals with different brightness, then the dynamic range is expanded, but the presence of saturated signals degrades the accuracy of on-imaging plane phase difference focus detection
Solution Approach 1:
The patent changes the synthesis ratio parameters dynamically based on saturation detection. When saturation is detected in either the first or second added signal, the determination unit adjusts the second ratio to a predetermined value rather than calculating it based on first ratios, thereby preventing saturated signals from degrading focus detection accuracy while maintaining HDR composition benefits
Solution Approach 2:
The system implements feedback by detecting saturation states in the added signals and using this information to adjust the synthesis ratios. The determination unit monitors the saturation condition and modifies the second ratio accordingly, creating a closed-loop control that maintains focus detection accuracy despite the presence of saturated signals in HDR composition
2Reliability
If multiple photoelectric conversion units per pixel are used to generate signals with different gains, then the dynamic range is expanded, but the complexity of signal processing increases
Solution Approach 1:
The patent segments the signal processing into distinct functional units: an addition unit that combines signals from multiple photoelectric conversion units, an averaging unit that processes partial signals, and a synthesis unit that combines the added and averaged signals. This segmentation organizes the complex processing into manageable, modular stages that can be implemented efficiently in hardware
Solution Approach 2:
The image sensor structure integrates multiple photoelectric conversion units within each pixel, allowing the same pixel to generate multiple signals with different gains simultaneously. This multi-functional approach enables the sensor to capture both high-dynamic-range information and focus detection information using a single integrated structure, reducing overall system 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 approach effectively reduces the influence of saturated signals, allowing for precise phase difference focus detection and expanded dynamic range in image capturing, ensuring accurate autofocus even when saturated signals are present.
Implementation Method 1
an image sensor having a plurality of pixels arranged in a matrix and each provided with a plurality of photoelectric conversion units
Data Source
AI summary
An image capturing apparatus comprises an image sensor that outputs a first added signal and a first average partial signal amplified by a first gain, and a second added signal and a second averaged partial signal amplified by a second gain, a processing unit that generates a third added signal by synthesizing the first and second added signals with a first ratio and a third averaged partial signal by synthesizing the first and second averaged partial signals with a second or third ratio, a determination unit that determines the first ratio based on the first or second added signal and determines the second ratio based on the first ratios, and changes the second ratio of a pixel group that includes a pixel corresponding to the saturated first or second added signal to the third ratio, which is not based on the first ratio.