Indirect Time-of-Flight Pixel Readout for Motion Blur Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing 3D imaging technologies, such as stereo triangulation and time-of-flight cameras, face challenges in creating 3D images in real time due to complexity and power requirements, especially in small devices, and suffer from motion blur and systematic errors.
Innovation Solution
The use of indirect time-of-flight (iTOF) pixel circuits with modulated light and phase modulation signals, including 0°/180° and 90°/270° phases, allows for parallel readout of memory nodes and cancellation of offset and dark current errors, improving motion blur performance and reducing readout speed requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If indirect time-of-flight sensors use conventional sequential readout methods, then device complexity is reduced, but motion blur increases and image quality deteriorates
Solution Approach 1:
The pixel array is divided into multiple independently readable blocks or regions. Each block can be read out in parallel through separate readout paths, allowing simultaneous acquisition of multiple image segments without requiring a single high-speed sequential readout, thereby reducing motion blur while maintaining manageable device complexity
Solution Approach 2:
The readout architecture transitions from a single-dimensional sequential readout to a multi-dimensional parallel readout structure. By adding spatial dimensionality through multiple readout paths and temporal dimensionality through coordinated timing, the system achieves high-speed readout without excessive complexity in any single dimension
2Manufacturing precision
If indirect time-of-flight sensors increase readout speed to reduce motion blur, then image quality improves, but power consumption increases
Solution Approach 1:
The sensor employs periodic modulation of the light source and synchronized periodic sampling of the photodetector output. By using alternating phases (0°/180° and 90°/270°) and periodic readout cycles, the system achieves high effective readout speed for motion blur reduction while allowing power management through controlled activation periods and idle periods
Solution Approach 2:
The system performs preliminary integration and accumulation of charge signals during the exposure period before final readout. By pre-processing and storing charge information in memory nodes during the integration phase, the actual readout operation can be faster and more efficient, reducing the power required for high-speed readout while maintaining image quality
3Measurement precision
If indirect time-of-flight sensors use single-phase readout, then device complexity is minimized, but systematic errors from offset and dark current increase
Solution Approach 1:
The system uses asymmetric phase sampling with specific phase combinations (0°/180° and 90°/270°) rather than symmetric uniform sampling. This asymmetric sampling strategy allows differential measurement techniques that inherently cancel offset and dark current errors, improving measurement precision while requiring only moderate increases in readout architecture complexity
Solution Approach 2:
The sensor creates multiple copies of the measurement process at different phase states (0°, 90°, 180°, 270°). By taking multiple measurements with different phase modulations and then processing these copies through differential calculations, the system cancels systematic errors while maintaining a relatively simple hardware architecture that merely replicates basic measurement functions
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 enables high-resolution 3D imaging with reduced power consumption and improved image quality by enhancing readout speed and reducing systematic errors in time-of-flight sensors.
Implementation Method 1
a photodetector configured to detect the incident modulated light and generate a portion of charge in response to the detected incident modulated light
Implementation Method 2
Time-of-flight cameras typically employ a light source that directs light at an object, a sensor that detects the light that is reflected from the object, and a processing unit that calculates the distance to the object based on the round-trip time it takes for the light to travel to and from the object
Data Source
AI summary
A time-of-flight pixel circuit includes a photodiode configured to generate charge in response to modulated light reflected from an object. First and second transfer transistors are coupled to the photodiode. The first transfer transistor transfers a first portion of charge from the photodiode in response to a first modulation signal and the second transfer transistor transfers a second portion of charge from the photodiode in response to a second modulation signal. The second modulation signal is an inverted first modulation signal. A first floating diffusion is coupled to the first transfer transistor to receive the first portion of charge in response to a first modulation signal. Each one of a first plurality of sample and hold transistors is coupled between a respective one of a first plurality of memory nodes and the first transfer transistor.