Dual-Pixel Image Sensor Reflecting Portions for Phase Detection
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Solution Overview
Problem
Conventional image-capturing devices face challenges in achieving accurate focus detection and maintaining sensitivity due to the miniaturization of pixels, which restricts light entry and decreases the electric charge generated, making it difficult to execute focus detection based on phase difference information without reducing the opening rate at pixels.
Innovation Solution
The image sensor employs a dual-pixel structure with reflecting portions disposed at different positions relative to the photoelectric conversion units, allowing for phase difference information calculation using signals from both pixels without the need for a light-shielding film, thereby improving sensitivity and preventing a decrease in focus detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If pixels are miniaturized to increase pixel density, then the number of pixels per unit area increases, but the amount of light entering each pixel decreases and the electric charge generated decreases
Solution Approach 1:
The pixel is divided into two separate photoelectric conversion units (first and second photoelectric conversion units) within the same pixel structure. This segmentation allows each unit to independently receive light and generate electric charge, effectively doubling the light reception capability without increasing the overall pixel footprint, thus resolving the contradiction between high pixel density and sufficient light reception.
2Measurement precision
If a light-shielding film is introduced to enable phase difference focus detection, then focus detection accuracy can be maintained, but the opening rate at pixels decreases and sensitivity is reduced
Solution Approach 1:
The pixel is divided into two separate photoelectric conversion units that can independently detect light. By comparing the signals from these two units, phase difference information can be obtained without requiring a light-shielding film, thus maintaining both focus detection accuracy and high sensitivity.
Solution Approach 2:
The dual photoelectric conversion unit structure serves multiple functions simultaneously: it enables phase difference focus detection, maintains high sensitivity due to increased light reception area, and achieves accurate focus detection without requiring additional light-shielding films. This multi-functionality resolves the contradiction between measurement precision and sensitivity.
3Device complexity
If a reflecting layer is disposed at a uniform position relative to the photoelectric conversion unit, then the structure is simple, but it cannot provide phase difference information for focus detection
Solution Approach 1:
Instead of using a uniform reflecting layer, the invention segments the light reception function into two separate photoelectric conversion units within each pixel. This segmentation enables the extraction of phase difference information by comparing signals from the two units, while maintaining relatively simple pixel-level structures without requiring complex reflecting layer arrangements.
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 accurate focus adjustment and maintains high sensitivity, allowing for effective focus detection and image generation even with highly miniaturized pixels, without the need for light-shielding films, thus preventing a decrease in light reception and focus detection accuracy.
Implementation Method 1
a first photoelectric conversion unit that generates an electric charge through photoelectric conversion of light having entered therein
Implementation Method 2
a reflecting portion disposed at least in a part of an area located in the first direction relative to a center of the first photoelectric conversion unit... which reflects part of light having been transmitted through the first photoelectric conversion unit toward the first photoelectric conversion unit
Data Source
AI summary
An image sensor having a plurality of pixels along a first direction includes: a first pixel having a first photoelectric conversion unit that generates an electric charge through photoelectric conversion and a reflecting portion disposed at least in a part of an area located in the first direction relative to a center of the first photoelectric conversion unit, which reflects part of light having been transmitted through the first photoelectric conversion unit toward the first photoelectric conversion unit; and a second pixel having a second photoelectric conversion unit that generates an electric charge through photoelectric conversion and a second reflecting portion disposed at least in a part of an area located in a direction opposite from the first direction relative to a center of the second photoelectric conversion unit, which reflects part of light having been transmitted through the second photoelectric conversion unit toward the second photoelectric conversion unit.