Image Sensor Pixel Array Grouping for Low-Light Focus Detection
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Solution Overview
Problem
Existing image capturing systems face challenges in performing accurate phase difference detection type focus adjustment, especially in low-light conditions where noise levels are high, making correct correlation operations for focus detection difficult.
Innovation Solution
The system employs an image sensor with a pixel array and column output lines, where signals from multiple photoelectric conversion elements are read out simultaneously to a column output line, enabling accurate focus adjustment by controlling the connection of floating diffusion portions of unit pixels in the same column, thereby improving focus detection accuracy in low-light conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signals from photoelectric conversion elements are read out individually from each unit pixel, then the device complexity is reduced, but the measurement precision of focus detection deteriorates in dark environments
Solution Approach 1:
The patent merges signals from multiple unit pixels (specifically 2×2 or 2×3 adjacent pixels) into a single group for simultaneous readout. This combining approach increases the signal strength and improves focus detection accuracy in dark environments by reducing noise impact, while maintaining manageable device complexity through systematic grouping strategies.
Solution Approach 2:
The patent implements a universal signal readout mechanism that can handle both individual pixel readout and grouped pixel readout through the same column output lines. The control unit dynamically selects between different readout modes (individual or grouped) based on lighting conditions, providing multi-functionality without requiring separate dedicated output lines for each mode.
2Measurement precision
If signals from multiple unit pixels are read out simultaneously to improve signal strength, then the measurement precision improves, but the loss of time increases due to additional signal processing
Solution Approach 1:
The patent performs preliminary grouping of unit pixels into predetermined groups before the actual focus detection operation. The control unit pre-configures which pixels belong to which groups and prepares the readout sequence in advance. This preliminary organization reduces the processing time during actual operation by eliminating dynamic decision-making during signal readout.
Solution Approach 2:
The patent implements periodic readout cycles where grouped signals are read out in systematic intervals. The control unit alternates between reading out different pixel groups in a predetermined sequence, allowing parallel processing of multiple groups over time. This periodic approach distributes the processing load and reduces overall processing time compared to sequential individual pixel readout.
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 allows for precise automatic focus adjustment even in dark environments by reducing noise and enhancing the accuracy of focus detection operations.
Implementation Method 1
two photodiodes are provided in one pixel of an image sensor, and the two photodiodes are each configured so as to use one microlens to receive light that has passed through a different pupil area of the image capturing lens
Data Source
AI summary
An image capturing apparatus comprises an image sensor that includes a pixel array in which a plurality of unit pixels, each having a plurality of photoelectric conversion elements, are arranged in matrix, and a plurality of column output lines respectively provided in columns of the pixel array, and a control unit that performs control such that in a case in which signals from a portion of photoelectric conversion elements of each of the plurality of unit pixels is to be read out, signals from a plurality of unit pixels that are arranged in the same column of the pixel array are output simultaneously to one column output line out of the plurality of column output lines.