Image Sensor with Stacked Substrates for Simultaneous Still and Moving Image Capture
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Solution Overview
Problem
Existing image capturing technologies cannot simultaneously shoot still and moving images without degrading image quality, as they require storage elements that increase pixel area and reduce photodiode size, affecting saturation characteristics and image quality.
Innovation Solution
An image capturing apparatus with a first semiconductor substrate for photodiodes and a second semiconductor substrate for storage elements, connected by transfer and readout units, allowing simultaneous storage and reading of pixel signals from different pixel groups across multiple frame periods to generate both still and moving images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If each pixel includes a storage element for sequential charge storage, then high frame rate imaging is achieved, but pixel area increases and photodiode area decreases, degrading image quality
Solution Approach 1:
The pixel array is divided into multiple independent pixel groups (first pixel group and second pixel group), each capable of independent charge accumulation and transfer. This segmentation allows different pixel groups to perform different functions simultaneously, enabling high frame rate imaging without requiring each individual pixel to contain complex storage elements, thus maintaining small pixel area and large photodiode area for high image quality.
Solution Approach 2:
The patent introduces a temporal dimension by utilizing multiple frame periods for charge accumulation and transfer. Instead of requiring storage elements within each pixel for instantaneous high frame rate capture, the system uses time-multiplexed charge transfer across multiple frames, achieving high frame rate capability while keeping pixel structure simple and photodiode area large.
2Speed
If each pixel includes storage elements for sequential charge storage, then high frame rate imaging is achieved, but the number of pixels that can be arranged in limited area decreases, degrading image quality
Solution Approach 1:
By segmenting the pixel array into multiple pixel groups that can be independently controlled and transferred, the system achieves high frame rate imaging without adding storage elements to each pixel. This allows maximum pixel density in the available area while maintaining high frame rate capability through coordinated operation of segmented pixel groups.
3Quantity of substance
If each pixel includes many storage elements, then charge storage capacity increases, but photodiode area decreases and saturation characteristic deteriorates, degrading image quality
Solution Approach 1:
The patent moves charge storage from the spatial domain (multiple storage elements within each pixel) to the temporal domain (charge accumulation across multiple frames in photodiodes). This allows large photodiode area for high charge storage capacity while maintaining excellent saturation characteristics, as charges are accumulated in the photodiode's depletion region over time rather than in separate storage elements.
4Speed
If charges are sequentially stored in storage elements, then high frame rate imaging is achieved, but simultaneous shooting of still image and moving image becomes impossible
Solution Approach 1:
The pixel array is segmented into multiple independent pixel groups that can be independently controlled. The first pixel group can accumulate charges for still image capture while the second pixel group simultaneously accumulates charges for moving image capture. This segmentation enables versatile simultaneous imaging modes without compromising high frame rate capability.
Solution Approach 2:
The system dynamically allocates different pixel groups to different imaging modes (still image or moving image) based on operational requirements. This dynamic flexibility allows the system to adapt to various imaging scenarios, including simultaneous still and moving image capture, while maintaining high frame rate performance through coordinated charge transfer operations.
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
Enables simultaneous shooting of still and moving images while maintaining image quality by efficiently managing pixel signals across multiple frame periods, without reducing photodiode area or degrading image resolution.
Implementation Method 1
charges generated by photoelectrical conversion upon exposure
Data Source
AI summary
An image capturing apparatus comprises an image sensor including a first semiconductor substrate on which a photodiode is arranged, a second semiconductor substrate on which a storage element is arranged, and a connection unit configured to electrically connect the photodiode and the storage element, a first transfer unit configured to transfer pixel signals of a first pixel group to the storage element, a first readout unit configured to read out the pixel signals of the first pixel group, a second transfer unit configured to transfer pixel signals of a second pixel group to the storage element, and a second readout unit configured to read out some of the pixel signals of the second pixel group, wherein an image of one frame is generated by composing the pixel signals of the second pixel group and the first pixel group.