Destructive Read Image Sensor Signal Accumulation for Low Light Focus
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Solution Overview
Problem
Image-capturing devices face challenges in achieving optimal image display and focus detection at lower brightness levels, as existing technologies struggle to balance signal refresh cycles and focus detection using signals from image and focus detection pixels.
Innovation Solution
The implementation of a destructive read-type image sensor with a specific pixel configuration, including focus detection pixels with unique spectral characteristics, and a control unit for uniform storage time, allows for effective signal addition and focus detection by integrating signals from multiple pixels over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the read unit reads out signals from the image sensor over a short cycle to provide optimal image display refresh, then the image display refresh rate is improved, but the signal level from focus detection pixels becomes insufficient for reliable focus detection in low-light conditions
Solution Approach 1:
The system performs preliminary action by accumulating multiple low-level signals from focus detection pixels over time in the storage unit before processing. This accumulation of signals over multiple read cycles builds up sufficient signal level for reliable focus detection without requiring a longer individual read cycle, thus maintaining high refresh rate while ensuring detection accuracy.
2Measurement precision
If multiple signals are accumulated over time to improve focus detection signal level, then the focus detection accuracy is improved, but the refresh cycle for image display is extended
Solution Approach 1:
The system segments the pixel array into distinct image-capturing pixels and focus detection pixels. This segmentation allows independent processing: image-capturing pixels provide signals for rapid display refresh, while focus detection pixels accumulate signals for accurate focus measurement. The segmentation enables both functions to operate optimally without interfering with each other's timing requirements.
Solution Approach 2:
The system applies partial action by using only specific pixels (focus detection pixels) for signal accumulation rather than all pixels. This selective approach limits the accumulation burden to a subset of pixels, allowing the overall system to maintain fast refresh cycles while still achieving sufficient signal levels for focus detection through targeted accumulation.
3Device complexity
If focus detection pixels use the same spectral characteristics as other pixels, then the device complexity is reduced, but the focus detection capability in low-light conditions deteriorates
Solution Approach 1:
The system applies local quality by giving focus detection pixels different spectral characteristics from image-capturing pixels. Specifically, focus detection pixels lack the color filter that blocks infrared light, allowing them to detect a broader spectrum including infrared. This local differentiation optimizes each pixel type for its specific function: image-capturing pixels for visible light imaging, focus detection pixels for sensitive focus measurement in various lighting conditions.
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 ensures reliable focus detection and maintains a constant refresh cycle for optimal image display, even in low-light conditions, by adjusting signal levels and storage times to enhance image quality and detection accuracy.
Implementation Method 1
a destructive read-type image sensor that executes photoelectric conversion of a light flux from an optical system at a plurality of pixels
Data Source
AI summary
An image-capturing device includes: a destructive read-type image sensor that executes photoelectric conversion of a light flux from an optical system at a plurality of pixels, stores electrical charges resulting from the photoelectric conversion at the plurality of pixels, and outputs a signal corresponding to each of the stored electrical charges; a read unit that reads out the signal from the image sensor over a specific cycle; a display unit at which display is brought up based upon the signal read out by the read unit each time the read unit reads out the signal; a storage unit that individually stores signals read out by the read unit, each in correspondence to a read operation; an adding unit that adds up a plurality of signals obtained sequentially over time among the signals stored in the storage unit; and a focus detection unit that detects a focus adjustment state of the optical system based upon adding results provided by the adding unit.