ToF Image Sensor Overflow Detection for Accurate Depth Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing image sensors using indirect Time-of-Flight (ToF) technology face increased area burden due to the need for multiple analog-to-digital converters and are prone to information errors from electronic saturation in floating diffusion nodes.
Innovation Solution
An image sensor with a 2-tap pixel structure and an overflow detection circuit that detects overflow through a simple structure, using logic operations and current paths to prevent electronic saturation, thereby reducing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple analog-to-digital converters are used in indirect ToF technology, then measurement precision is improved, but area increases
Solution Approach 1:
The patent extracts the overflow detection function from the floating diffusion node and implements it through a separate overflow detection circuit that monitors voltage levels. This allows the floating diffusion node to be optimized for photoelectric conversion without being constrained by overflow detection requirements, effectively separating measurement precision functions from area-consuming components.
Solution Approach 2:
The patent introduces an overflow detection circuit as an intermediary component that monitors the voltage level of the floating diffusion node and generates overflow detection signals. This intermediary mechanism enables overflow detection without requiring multiple analog-to-digital converters, thus maintaining measurement precision while controlling area.
2Ease of manufacture
If floating diffusion node is used in pixel circuit, then ease of manufacture is improved, but reliability deteriorates due to electronic saturation
Solution Approach 1:
The patent applies preliminary action by implementing an overflow detection circuit that continuously monitors the voltage level of the floating diffusion node before saturation occurs. When the voltage approaches the saturation threshold, the circuit generates an overflow detection signal to alert the system, allowing for preventive measures to be taken before electronic saturation compromises signal accuracy.
Solution Approach 2:
The patent implements feedback through the overflow detection circuit that monitors the voltage level of the floating diffusion node and provides feedback signals to the pixel circuit. This feedback mechanism enables real-time detection of overflow conditions, allowing the system to adjust operations to prevent electronic saturation and maintain signal 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
The solution effectively prevents information errors by detecting overflow in the image sensor's pixel array, ensuring accurate depth measurement and reducing the area burden of analog-to-digital converters.
Implementation Method 1
detecting overflow of the first tap pixel based on a first tap pixel signal outputted from the first tap pixel and overflow of the second tap pixel based on a second tap pixel signal outputted from the second tap pixel, and forming a current path from an overflow current source to a ground voltage terminal when a voltage of the first tap pixel signal or a voltage of the second tap pixel signal drops below a predetermined voltage
Implementation Method 2
distances may be measured by irradiating light from a light source near an image sensor and measuring the time taken for the light to be reflected off an object and returned
Implementation Method 3
electrons are generated in a pixel circuit by a majority current that is created through an application of a substrate voltage
Implementation Method 4
the generated electrons are detected by using a potential difference between electric fields
Data Source
AI summary
Disclosed is an image sensor including a first tap pixel, a second tap pixel, and an overflow detection circuit suitable for detecting overflow of the first tap pixel based on a first tap pixel signal outputted from the first tap pixel and overflow of the second tap pixel based on a second tap pixel signal outputted from the second tap pixel, and forming a current path from an overflow current source to a ground voltage terminal when a voltage of the first tap pixel signal or a voltage of the second tap pixel signal drops below a predetermined voltage.