SPAD Image Sensor Architecture for High Pixel Density Photon Counting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional solid-state image sensors face challenges in improving pixel density and power saving while maintaining sensitivity, as sharing circuits among single-photon avalanche diodes (SPADs) leads to increased circuit scale and reduced sensitivity when attempting to reduce the light receiving area or operate at low voltages.
Innovation Solution
A solid-state image sensor design featuring a light-receiving substrate with multiple avalanche photodiodes and a logic substrate with a counter, utilizing selection transistors, detection circuits, and control circuits to manage photon counting, reduce circuit scale, and optimize pixel selection and data generation, while incorporating pulse-shaping and voltage control mechanisms to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If circuits are shared among multiple SPADs to reduce circuit scale, then circuit scale is reduced, but pixel density and power saving performance cannot be further improved
Solution Approach 1:
The patent divides the image sensor into two separate substrates: a light-receiving substrate containing only avalanche photodiodes and a logic substrate containing only processing circuits (inverter, switch elements, counter). This segmentation allows each substrate to be optimized independently, enabling further reduction of circuit scale on the logic substrate while increasing pixel density on the light-receiving substrate without the trade-off that exists in integrated designs.
2Productivity
If light receiving area of each pixel is reduced to improve pixel density, then pixel density is improved, but sensitivity decreases
Solution Approach 1:
The patent moves the processing circuits from the light-receiving substrate to a separate logic substrate, effectively adding a spatial dimension to the system architecture. This allows the light-receiving substrate to be densely packed with photodiodes (improving pixel density) while the logic substrate handles all processing functions, maintaining sensitivity through proper circuit design without being constrained by on-substrate circuit space.
3Use of energy by stationary object
If circuit for operation at low voltage is added to improve power saving, then power saving is improved, but circuit scale increases
Solution Approach 1:
The patent extracts all processing circuits from the light-receiving substrate and places them on a separate logic substrate. This extraction allows the light-receiving substrate to maintain minimal circuit scale with only photodiodes, while the logic substrate can implement low-voltage operating circuits for power saving without increasing the overall device complexity in a way that compromises pixel density or 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
The design achieves reduced circuit scale for each substrate, improved pixel density, and enhanced power saving by effectively counting photons and managing pixel data, thereby improving the overall performance of the solid-state image sensor.
Implementation Method 1
a plurality of avalanche photodiodes, each generating a current corresponding to incident of a photon
Data Source
AI summary
Improved is performance of a solid-state image sensor that detects presence or absence of a photon.The solid-state image sensor includes a light-receiving substrate and a logic substrate. In the solid-state image sensor, there is disposed, on the light-receiving substrate, a plurality of avalanche photodiodes, each of the avalanche photodiodes generating a current corresponding to incident of a photon. Furthermore, in the solid-state image sensor, there is disposed, on the logic substrate, a counter that counts the number of photons on the basis of a current of a selected avalanche photodiode among the plurality of avalanche photodiodes.