Stacked Solid-State Imaging Device Phase Difference Autofocus
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Solution Overview
Problem
In mirror-less single lens reflex cameras, integrating a phase difference AF sensor is challenging due to the placement of image acquisition pixels and phase difference AF pixels in the same effective pixel area, leading to defective pixels and compromised image quality.
Innovation Solution
A solid-state imaging device with stacked substrates, where the first substrate has photoelectric conversion units for image acquisition and the second substrate has pairs of photoelectric conversion units for phase difference AF, with charge isolation regions to prevent charge movement and ensure efficient light separation using micro lenses and color filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixels for phase difference AF are disposed in the effective pixel area, then phase difference AF performance is improved, but image quality deteriorates due to defective pixels
Solution Approach 1:
The patent transitions from a two-dimensional planar arrangement to a three-dimensional stacked configuration by placing image acquisition pixels on a first substrate and phase difference AF pixels on a second substrate. This vertical separation in the third dimension allows both pixel types to coexist without spatial conflict, enabling full utilization of the effective pixel area for both imaging and autofocus functions simultaneously.
Solution Approach 2:
The pixel array is segmented into functionally distinct groups located on separate substrates: image acquisition pixels on the first substrate and phase difference AF pixels on the second substrate. This segmentation allows independent optimization of each pixel type's performance without compromise, as each substrate can be dedicated to its specific function.
2Measurement precision
If a predetermined number of pixels for phase difference AF are secured, then autofocus operation is improved, but image data requires supplementary defect processing
Solution Approach 1:
Phase difference AF pixels are extracted from the image acquisition pixel array and placed on a separate second substrate. This extraction eliminates the need for defect processing in image data, as phase difference AF pixels no longer occupy positions that would otherwise be used for image acquisition, removing the source of defective pixels entirely.
Solution Approach 2:
By moving phase difference AF pixels to a separate substrate in the vertical dimension, the patent eliminates the spatial overlap that causes defective pixels. This dimensional separation ensures that image data acquisition and phase difference AF measurements occur at distinct physical locations, removing the need for complex defect processing algorithms.
3Reliability
If stacked substrate structure is used, then spatial conflict between pixel types is resolved, but device complexity increases
Solution Approach 1:
The patent combines image acquisition pixels and phase difference AF pixels into a single integrated solid-state imaging device through stacking. While this creates a multi-substrate structure, the merging of both functions into one device maintains compact form factor and enables coordinated operation, with the added complexity offset by the elimination of separate components.
Solution Approach 2:
The stacked substrate structure creates a universal imaging device that performs both image acquisition and phase difference AF measurements simultaneously. The first substrate handles imaging while the second substrate handles autofocus, making the device multi-functional without requiring separate components, thereby justifying the increased structural complexity through enhanced versatility.
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 allows for improved image quality by enabling effective phase difference AF operations without compromising image acquisition, as signals for focus detection are generated from multiple positions, reducing signal variations and enhancing autofocus performance.
Implementation Method 1
first photoelectric conversion units configured to convert the incident light into signals
Data Source
AI summary
A solid-state imaging device has a plurality of micro lenses, a first substrate, and a second substrate. The first substrate has a plurality of first photoelectric conversion units. Each of the plurality of first photoelectric conversion units corresponds to any one of the plurality of micro lenses. The second substrate has a plurality of second photoelectric conversion units and a plurality of third photoelectric conversion units. A plurality of pairs of photoelectric conversion units are disposed, and each of the plurality of pairs of photoelectric conversion units includes one of the second photoelectric conversion units and one of the third photoelectric conversion units. Each of the plurality of pairs of photoelectric conversion units corresponds to at least one of the plurality of first photoelectric conversion units. The second substrate further includes charge isolation regions disposed between the second photoelectric conversion units and the third photoelectric conversion units.