Stacked SPAD Image Sensor Layout for Smaller Pixels
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Solution Overview
Problem
Existing sensor devices face challenges in miniaturizing Single Photon Avalanche Diode (SPAD) pixels due to size limitations of the SPAD circuit, which also increase costs and parallax issues when combining image and distance information from separate camera modules.
Innovation Solution
A sensor device with a first substrate unit containing an SPAD pixel and visible-light pixels in a mixed array on a shared semiconductor substrate, and a second substrate unit with an SPAD circuit and visible-light pixel circuit, allowing for miniaturization of SPAD pixels without size constraints and shared optical axis for image and distance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the SPAD pixel size is reduced, then pixel density increases, but the SPAD pixel size is limited by the size of the SPAD circuit
Solution Approach 1:
The sensor device is divided into two separate substrate units: a first substrate unit containing only the SPAD pixel and visible-light pixels, and a second substrate unit containing the SPAD circuit and visible-light pixel circuit. This segmentation allows the SPAD pixel to be miniaturized independently without being constrained by the SPAD circuit size, as the circuit is located on a different substrate.
Solution Approach 2:
The solution moves from a two-dimensional planar integration to a three-dimensional stacked configuration. By stacking the first substrate unit (pixel layer) and second substrate unit (circuit layer) in the vertical dimension, the patent enables independent sizing of pixels and circuits, allowing SPAD pixel miniaturization while maintaining full circuit functionality on the separate substrate.
2Reliability
If separate camera modules are used for image and distance sensing, then functional independence is achieved, but mounting area increases and parallax occurs at short distances
Solution Approach 1:
The patent combines image sensing (visible-light pixels) and distance sensing (SPAD pixel) into a single integrated sensor device with a shared optical axis. Both substrate units are optically aligned to the same optical path, eliminating parallax while maintaining functional independence through separate pixel and circuit processing.
Solution Approach 2:
The first substrate unit serves dual purposes: the visible-light pixels capture image information while the SPAD pixel captures distance information. Both functions share the same optical path and substrate, creating a multi-functional sensor that eliminates the need for separate camera modules.
3Reliability
If separate camera modules are used, then image and distance sensing are independent, but data processing complexity increases due to parallax compensation
Solution Approach 1:
By integrating both visible-light pixels and SPAD pixel on the same first substrate unit with a shared optical axis, the patent eliminates parallax between the two sensing functions. This merging of optical paths simplifies data processing as no parallax compensation is required, while functional independence is maintained through separate pixel circuits on the second substrate unit.
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 miniaturization of SPAD pixels, reduces image processing load, and enhances the ability to acquire both image and distance data on the same optical axis, thereby reducing power consumption and increasing pixel density.
Implementation Method 1
a first substrate unit and a second substrate unit bonded to the first substrate unit
Data Source
AI summary
Provided is a sensor device capable of miniaturizing an SPAD pixel. The sensor device includes a first substrate unit and a second substrate unit bonded to the first substrate unit. The first substrate unit includes a first semiconductor substrate and a pixel region provided on the first semiconductor substrate and in which the SPAD pixel and a plurality of visible-light pixels are mixed in an array. The second substrate unit includes a second semiconductor substrate facing the first semiconductor substrate, an SPAD circuit provided on the second semiconductor substrate and connected to the SPAD pixel, and a visible-light pixel circuit provided on the second semiconductor substrate and connected to the plurality of visible-light pixels.