Stacked Depth Sensor Photosites Enhance Sensitivity
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Solution Overview
Problem
Existing depth image sensors face challenges in achieving high resolution with reduced dimensions and increased sensitivity while maintaining the same lateral dimensions as conventional sensors.
Innovation Solution
The development of a depth image sensor utilizing a configuration of depth pixels with pairs of photosites on stacked semiconductor substrates, where each depth pixel acquires multiple samples of charges at different phase shifts to determine the phase shift between incident and reflected light signals, enhancing sensitivity without increasing surface area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional depth image sensors are used, then resolution can be achieved, but sensitivity is insufficient and dimensions cannot be reduced
Solution Approach 1:
The patent transitions from a planar sensor architecture to a three-dimensional stacked architecture. Multiple photosensitive elements are arranged in vertical stacks along the depth direction, allowing the sensor to maintain high lateral resolution while increasing sensitivity through additional detection layers without expanding the sensor's footprint area.
Solution Approach 2:
The patent implements nested photosensitive elements within stacked layers, where multiple photosites are positioned at different depths within the same lateral footprint. This nesting approach allows multiple detection functions to be integrated within the same spatial envelope, improving sensitivity without increasing lateral dimensions.
2Area of stationary object
If sensor dimensions are reduced, then compactness is improved, but resolution deteriorates
Solution Approach 1:
By moving to a three-dimensional stacked architecture, the patent decouples resolution from lateral dimensions. High resolution is achieved through multiple photosensitive elements arranged vertically within the same lateral footprint, allowing compact sensor size while maintaining or improving resolution through the additional depth dimension.
Solution Approach 2:
The sensor is segmented into multiple independent photosensitive elements arranged in stacks, with each element contributing to the overall resolution. This segmentation allows the resolution to be determined by the number of stacked layers rather than lateral area, enabling compact dimensions while maintaining high resolution.
3Measurement precision
If multiple photosensitive elements are stacked, then sensitivity increases, but complexity of charge acquisition increases
Solution Approach 1:
Multiple photosensitive elements sharing the same pixel coordinates in different stacks are merged into a single pixel unit. Their charge outputs are combined through shared readout circuits and processing logic, allowing the system to benefit from increased sensitivity while managing complexity through consolidation rather than independent handling of each element.
Solution Approach 2:
The stacked photosensitive elements are designed with universal functionality, where elements at the same pixel coordinates across different stacks perform identical detection functions. This multi-functionality allows a single set of readout circuits and processing algorithms to handle multiple elements, reducing overall system complexity despite increased sensitivity.
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 improved sensitivity and accuracy in depth mapping without degrading resolution or increasing sensor size, enabling more precise distance information reconstruction without the need for compensation or calibration between detection levels.
Implementation Method 1
each photosite corresponding to a single photosensitive element and an assembly of components enabling to acquire at least one sample of charges photogenerated by absorption by this photosensitive element of the reflected light signal
Data Source
AI summary
A sensor of a reflected light signal for acquiring a depth map of the scene. Each depth pixel of the sensor includes at least one pair of photosites. Each pair of photosites incudes a first photosite of a first semiconductor substrate and a second photosite of a second substrate having the first substrate stacked thereon. Each pixel is configured to acquire, for each pair of photosites of the pixel, at least one sample of charges simultaneously photogenerated in photosensitive elements of the photosites of said pair.