Image Sensor Readout Unit Switching for Focus Detection
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Solution Overview
Problem
Conventional image capturing apparatuses face a challenge in maintaining a high framerate while increasing the number of pupil divisions for improved focus detection accuracy, as increased pupil divisions lead to longer pixel signal readout times, limiting the framerate and affecting the speed of focus adjustment, especially for moving subjects.
Innovation Solution
An image capturing apparatus with a readout unit that switches between different readout operations based on the status of the apparatus, allowing for efficient signal processing by reading out signals from a subset or all pupil areas at varying framerates, thereby optimizing framerate and focus detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of pupil divisions is increased to improve focus detection accuracy, then the accuracy of focus detection is improved, but the readout time is lengthened which limits the framerate
Solution Approach 1:
The patent divides the pixel array into multiple regions (first region and second region) with different readout characteristics. The first region contains pixels for normal image capture while the second region contains pixels for phase difference focus detection. By segmenting the readout process into separate regional operations, the system can optimize each region independently, allowing high framerate in the first region while maintaining accurate focus detection in the second region, thus resolving the contradiction between readout time and focus detection accuracy.
Solution Approach 2:
Different regions of the pixel array are assigned different functions and readout characteristics. The first region is optimized for high framerate normal image capture, while the second region is optimized for phase difference focus detection. This local differentiation allows each region to operate at its optimal performance level, enabling the system to achieve both high framerate and accurate focus detection simultaneously without being constrained by the slower readout requirements of the entire array.
2Productivity
If the readout time is reduced to increase framerate, then the framerate is improved, but the number of pupil divisions must be reduced which decreases focus detection accuracy
Solution Approach 1:
The pixel array is segmented into functional regions that can be read out independently at different rates. The first region supports high framerate operation for normal imaging, while the second region performs phase difference detection with appropriate readout timing. This segmentation allows the system to achieve high overall framerate while maintaining sufficient focus detection accuracy through the specialized second region.
Solution Approach 2:
Instead of requiring the entire pixel array to operate at maximum speed, the patent applies partial action by having only the necessary second region operate at optimized readout rates for phase difference detection. The first region can operate at high framerate without compromising focus detection, as the critical focus measurement function is performed by the specialized second region with appropriate readout characteristics.
3Ease of operation
If all photodiode signals are added together to obtain normal images, then the image signal is obtained, but the disparate signals needed for phase difference focus detection are lost
Solution Approach 1:
The pixel array is divided into first and second regions that preserve different signal characteristics. The first region maintains signals suitable for normal image capture, while the second region preserves disparate signals necessary for phase difference focus detection. By segmenting the pixel array, the system can simultaneously maintain both image signal acquisition and phase difference detection capabilities without requiring signal addition that would eliminate disparity information.
Solution Approach 2:
Different regions of the pixel array are optimized for different functions: the first region for normal image capture and the second region for phase difference focus detection. This local quality differentiation ensures that both image signal acquisition and disparate signal preservation coexist within the same device, allowing the system to maintain ease of operation for imaging while preserving measurement precision for focus detection.
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 solution enables the suppression of framerate drops even with increased pupil divisions, improving focus accuracy and speed for moving subjects by optimizing readout operations and reducing processing time.
Implementation Method 1
each of the pixels including a plurality of photoelectric conversion elements for a single microlens
Data Source
AI summary
An image capturing apparatus includes: an image sensor; a readout unit capable of switching between carrying out a first readout operation of reading out signals from photoelectric conversion elements corresponding to a first number of pupil areas and a signal obtained by adding together signals from the photoelectric conversion elements corresponding to all of the pupil areas, and a second readout operation of reading out signals from photoelectric conversion elements corresponding to a second number and a signal obtained by adding together signals from the photoelectric conversion elements corresponding to all of the pupil areas; and a control unit that controls whether to cause the readout unit to carry out the first readout operation or the second readout operation in accordance with a status of the image capturing apparatus.