TOF Pixel Sensor Modulation Gates for Higher Contrast Readout
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional time-of-flight (TOF) pixel sensors suffer from high temporal noise, high power consumption, low charge modulation frequency, and high modulation latency, leading to low modulation contrast and reduced sensor precision.
Innovation Solution
Implementing structures that increase vertical electric field strength, reduce charge transfer barriers, and utilize storage diodes adjacent to a silicon photoconversion structure for low latency charge storage, along with continuous phase modulation and light retention structures to enhance photocarrier production and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional TOF pixel sensors use standard charge storage and readout mechanisms, then device complexity is maintained at acceptable levels, but temporal noise is high and modulation contrast is low
Solution Approach 1:
The pixel sensor is divided into distinct functional regions: a modulation chamber for photocarrier generation, storage diodes for charge storage, and readout circuitry. This segmentation allows each region to be optimized for its specific function, improving modulation contrast while managing complexity through modular design
Solution Approach 2:
Storage diodes are introduced as intermediary structures between the modulation chamber and readout circuitry. These diodes temporarily hold photocharge, enabling low-latency storage and facilitating correlated double sampling to cancel kTC noise, thereby improving modulation contrast without excessive complexity increase
2Reliability
If CAPD pixel sensors use diode modulation nodes for charge storage, then charge storage is achieved, but power consumption is high due to constant current flow
Solution Approach 1:
Instead of constant current flow, the patent uses periodic pulsing of the photocharge drain to transfer charge from the modulation chamber to storage diodes. This periodic action maintains charge storage capability while dramatically reducing power consumption by eliminating continuous current flow through forward-biased diodes
3Reliability
If CAPD pixel sensors use diode modulation nodes, then charge storage is enabled, but modulation latency is high due to weak vertical electric field
Solution Approach 1:
The patent creates a localized strong vertical electric field in the modulation chamber by applying voltage to modulation gates positioned adjacent to the chamber. This local field enhancement expedites photocharge transfer to storage diodes, reducing modulation latency while maintaining charge storage capability
Solution Approach 2:
Storage diodes are pre-positioned adjacent to the modulation chamber and pre-biased to ready states. This preliminary preparation allows immediate charge storage upon photocharge generation, minimizing modulation latency while ensuring reliable charge storage
4Reliability
If PPD pixel sensors are used for charge conversion, then charge conversion is achieved, but temporal noise is high due to low conversion gain on floating diffusion nodes
Solution Approach 1:
Storage diodes serve as intermediary structures between the pinned photodiode and floating diffusion nodes. By storing photocharge in the diodes before transfer to floating diffusion, the system achieves higher conversion gain and reduced temporal noise through correlated double sampling, while maintaining charge conversion capability
5Reliability
If PPD pixel sensors are used, then charge conversion is enabled, but modulation frequency is low and modulation contrast is reduced due to slow charge transfer
Solution Approach 1:
The patent creates a localized strong vertical electric field in the modulation chamber through adjacent modulation gates. This local field enhancement significantly accelerates charge transfer from the pinned photodiode to storage diodes, enabling high modulation frequencies while maintaining reliable charge conversion
Solution Approach 2:
Storage diodes are pre-positioned and pre-biased adjacent to the modulation chamber, ready to immediately accept photocharge. This preliminary preparation eliminates charge transfer bottlenecks, enabling high-speed modulation while maintaining charge conversion reliability
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
Achieves significantly higher modulation contrast, enabling improved depth/distance resolution and precision by mitigating kTC noise and expediting charge storage, thus enhancing sensor performance.
Implementation Method 1
Implementing structures that increase vertical electric field strength, reduce charge transfer barriers, and utilize storage diodes adjacent to a silicon photoconversion structure for low latency charge storage
Implementation Method 2
utilize storage diodes adjacent to a silicon photoconversion structure for low latency charge storage
Data Source
AI summary
First and second modulation gates disposed adjacent a silicon photoconversion structure generate, throughout the exposure interval, alternating first and second electrostatic fields that compel photocharge generated within the silicon photoconversion structure to the first and second storage diodes, respectively. Upon conclusion of the exposure interval, accumulated photocharge within the first and second storage diodes is transferred to first and second floating diffusion nodes, respectively, as part of a correlated-double-sampling readout with respect to each of the floating diffusion nodes.