Image Sensor Crosstalk Weighting for Phase Detection
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Solution Overview
Problem
Conventional focus detection techniques face challenges in achieving accurate focus detection results due to the effects of crosstalk, which can vary with pixel output, incident light angle, F-number, image height, and photoelectric conversion portion area, making it difficult to accurately correct for crosstalk and ensuring reliable focus detection even with remaining errors.
Innovation Solution
An image capturing apparatus with a two-dimensionally arrayed image sensor, where each pixel has a first and second photoelectric conversion portion receiving light from different pupil regions, generates combined signals by weighting down signals from photoelectric conversion portions with significant crosstalk effects, allowing for phase difference detection between these signals to improve focus detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If crosstalk correction is performed using conventional methods, then focus detection accuracy is improved, but the complexity of the system increases due to the large number of parameters required for correction
Solution Approach 1:
The patent extracts and removes the crosstalk component from the pixel signals through correction processing. By identifying and subtracting the crosstalk portion from the total signal, the system achieves accurate focus detection without needing to manage complex correction parameters for all possible crosstalk scenarios
Solution Approach 2:
The patent creates a model or representation of the crosstalk effect based on signal characteristics, and uses this copied model to correct the actual signals. Instead of directly measuring and correcting each crosstalk instance with complex parameters, the system uses the signal pattern itself to identify and correct crosstalk
2Reliability
If crosstalk correction is performed, then focus detection reliability is improved, but the amount of information required for correction increases making accurate correction difficult
Solution Approach 1:
The patent enables the signal processing system to self-correct crosstalk effects by using the inherent characteristics of the signals themselves. The correction process uses the signal data already present in the system without requiring external correction parameters or additional information about the crosstalk sources
Solution Approach 2:
The system uses feedback from the signal characteristics to automatically adjust and correct for crosstalk effects. By monitoring the signal patterns and applying correction based on observed deviations, the system maintains reliable focus detection without needing extensive prior information about crosstalk conditions
3Power
If signals from all photoelectric conversion portions are combined equally, then signal strength is maximized, but crosstalk effects reduce focus detection accuracy
Solution Approach 1:
The patent applies different processing weights to different photoelectric conversion portions based on their individual crosstalk characteristics. Instead of uniform combination, signals from portions with higher crosstalk susceptibility are weighted differently, allowing the system to maintain signal strength while improving accuracy by emphasizing cleaner signals
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 enables accurate focus detection even with errors from crosstalk, by effectively reducing the impact of crosstalk through signal weighting, thereby enhancing the reliability and precision of focus detection results.
Implementation Method 1
each of the pixels having a first photoelectric conversion portion that receives a light beam passing through a first pupil region of an exit pupil of an imaging optical system and a second photoelectric conversion portion that receives a light beam passing through a second pupil region of the exit pupil of the imaging optical system
Data Source
AI summary
An image capturing apparatus includes an image sensor that has a plurality of two-dimensionally arrayed pixels, each of the pixels having a first photoelectric conversion portion and a second photoelectric conversion portion, a generation unit that generates a first image signal by connecting, in a pupil divided direction, a first signal obtained by combining signals of the first photoelectric conversion portions, and generate a second image signal, in the pupil divided direction, a second signal obtained by combining signals of the second photoelectric conversion portions. In a case of combing signals of the first photoelectric conversion portions, or combining signals of the second photoelectric conversion portions, the generation unit decreases weighting of a signal of a photoelectric conversion portion in which an effect of crosstalk from a neighboring photoelectric conversion portion is large.