Image Sensor Readout Mode Selection for Focus Adjustment
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Solution Overview
Problem
Current image capturing devices face challenges in achieving high-speed focus adjustment and maintaining image quality due to the integration of focus detection pixels with imaging pixels, particularly during live view and auto focus operations, as existing techniques either compromise on image quality or require complex and expensive optical systems.
Innovation Solution
An image capturing apparatus with a two-dimensional array of pixels, including a first pixel group for image generation and a second pixel group for phase difference detection, employs a readout mechanism with multiple modes to selectively thin and read out pixels based on thinning ratios and phases, allowing for adaptive focus adjustment without degrading image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If focus detection pixels are arranged at predetermined intervals between imaging pixels, then phase difference focus detection can be realized without dedicated AF sensor, but image quality deteriorates at locations where focus detection pixels are arranged
Solution Approach 1:
The patent applies dynamics by making the readout mode changeable based on operational requirements. The image sensor can switch between a first readout mode (reading all pixels for high image quality) and a second readout mode (skipping focus detection pixels for high-speed readout during AF operation), allowing the system to adapt its behavior dynamically according to the current function being performed.
Solution Approach 2:
The patent segments the pixel array into different functional groups: imaging pixels and focus detection pixels. By selectively reading out only imaging pixels in the second readout mode while skipping focus detection pixels, the system separates the functions of image capture and focus detection during specific operations, thereby preventing focus detection pixel artifacts from degrading image quality.
2Productivity
If all pixels are read out for high-speed live view, then live view function is achieved, but focus detection precision decreases
Solution Approach 1:
The system dynamically switches between readout modes based on operational context. During live view operation, the first readout mode reads all pixels including focus detection pixels to maintain focus detection capability. During auto focus operation, the second readout mode skips focus detection pixels to achieve high-speed readout, thereby resolving the contradiction between live view speed and focus detection precision.
3Speed
If focus detection pixels are read out during high-speed readout, then high-speed operation is achieved, but image quality deteriorates due to interpolation from surrounding pixels
Solution Approach 1:
The patent extracts and removes focus detection pixels from the readout stream during the second readout mode. By explicitly skipping these pixels during high-speed readout operations, the system prevents them from being processed as imaging data and requiring interpolation, thereby maintaining image quality while achieving high-speed readout for focus detection purposes.
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 high-speed focus adjustment while minimizing image quality deterioration by strategically selecting readout modes that prioritize image quality or precision, allowing for continuous live view and auto focus operations without the need for additional sensors or complex optical systems.
Implementation Method 1
a first pixel group that photoelectrically converts an object image formed by an imaging lens and generates a first signal for image generation, and a second pixel group that is discretely arranged between a plurality of pixels comprising the first pixel group, splits the pupil region of the imaging lens, photoelectrically converts the object image from the split pupil region
Data Source
AI summary
An image capturing apparatus is provided with an image sensor that has a first pixel group and a second pixel group, a focus adjustment unit that executes focus adjustment of an imaging lens based on the signal from the second pixel group, a readout unit that has a first thinning and readout mode that thins and reads out signals from the plurality of pixels at a predetermined thinning ratio and thinning phase, and a second thinning and readout mode that thins and reads out signals from the plurality of pixels with a difference in at least one of the thinning ratio and the thinning phase from the first thinning and readout mode, and a selecting unit that selects in which mode to operate the readout means from among the first and second thinning and readout modes in accordance with the state of the image capturing apparatus.