Focus Detection Pixels for Low-Light Imaging
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Solution Overview
Problem
Solid-state imaging devices struggle to perform accurate focus detection in low-light environments due to insufficient light reception by focus detection pixels, leading to failure in executing optimal focus detection during live view display in electronic cameras.
Innovation Solution
The implementation of a solid-state imaging device with a two-dimensional array of pixels, including first and second focus detection pixels receiving light fluxes through different areas of the exit pupil, allowing for simultaneous selection and signal combination to enhance focus detection accuracy, while also incorporating imaging pixels for image capture, and alternating their disposition within rows or columns to optimize light reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If focus detection pixels are used to detect image shift for focus detection, then focus detection capability is provided, but in low-light environments insufficient light is received resulting in failure to execute accurate focus detection
Solution Approach 1:
The patent combines multiple focus detection pixels (first focus detection pixels receiving light through a first area of the exit pupil and second focus detection pixels receiving light through a second area of the exit pupil) into a unified focus detection system. By simultaneously selecting and combining signals from multiple pixels disposed within a single row or column, the system increases the total light reception quantity while maintaining focus detection accuracy, thereby resolving the contradiction between measurement precision and illumination intensity.
2Productivity
If image signals are output at a predetermined frame rate for live view display, then real-time display is achieved, but exposure time is limited preventing optimal focus detection
Solution Approach 1:
The patent applies partial action by selectively reading out only the necessary focus detection signals from the combined focus detection pixels at the predetermined frame rate, while allowing extended exposure time for signal accumulation. The scanning circuit is configured to select and read out signals from multiple focus detection pixels simultaneously, enabling the system to maintain high frame rate productivity while achieving sufficient exposure time for accurate focus detection through the combined signal from multiple pixels.
3Measurement precision
If multiple focus detection pixels are combined to increase light reception, then focus detection accuracy in low light is improved, but device complexity increases
Solution Approach 1:
The patent segments the pixel array into distinct functional regions: first focus detection pixels disposed within a single row or column that receive light through a first area of the exit pupil, and second focus detection pixels that receive light through a second area of the exit pupil. This segmentation allows the scanning circuit to selectively read out only the necessary focus detection signals, combining functionality while maintaining manageable device complexity through organized spatial arrangement.
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 enables accurate focus detection and live view display in electronic cameras, even in low-light conditions, by ensuring sufficient light reception for focus detection pixels and maintaining image capture functionality.
Implementation Method 1
Each pixel includes a photodiode that generates signal charge in correspondence to incoming light
Data Source
AI summary
A solid-state imaging device includes a plurality of pixels disposed in a two-dimensional array, a scanning circuit that selects a specific pixel among the pixels by selecting a pixel row and a pixel column and a signal output circuit that outputs a signal from the pixel selected by the scanning circuit. The plurality of pixels include a plurality of first focus detection pixels and a plurality of second focus detection pixels. The first focus detection pixels and the second focus detection pixels are disposed within a single row or a single column. The scanning circuit selects a plurality of first or second focus detection pixels disposed within the single row or column at once. The signal output circuit combines signals from the plurality of first or second focus detection pixels selected by the scanning circuit and outputs a resulting composite signal.