Indirect Time-of-Flight Readout Architecture for Scanned Pixel Groups
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Solution Overview
Problem
Conventional 3D imaging techniques, such as stereo imaging, face challenges in creating 3D images using small devices due to the need for significant separation between cameras and high computational complexity, making real-time 3D image acquisition difficult.
Innovation Solution
A time-of-flight sensing system that employs a light source to emit modulated light, a pixel array to detect reflected light, and a control circuit to calculate object distance based on phase shifts, allowing for indirect time-of-flight measurements to generate 3D images efficiently, even in small devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If stereo imaging with multiple cameras is used to create 3D images, then depth information can be obtained through triangulation, but the device size increases due to minimum separation distance requirements between cameras
Solution Approach 1:
The patent replaces the mechanical triangulation system (multiple cameras with physical separation) with an optical time-of-flight measurement system. A single sensor captures phase-shifted light signals to determine depth, eliminating the need for multiple separated cameras while maintaining depth measurement capability.
Solution Approach 2:
The patent measures depth by detecting phase shifts in light signals rather than using geometric triangulation. By modulating the light source and measuring phase differences in reflected light, the system obtains depth information from temporal parameters rather than spatial separation, enabling compact device design.
2Measurement precision
If stereo imaging with multiple cameras is used to create 3D images, then depth information can be obtained, but computational complexity increases requiring significant processing power for real-time 3D image creation
Solution Approach 1:
The patent replaces complex computational triangulation algorithms with direct phase measurement. The depth calculation becomes a straightforward phase difference computation from modulated light signals, significantly reducing processing requirements while maintaining real-time 3D image generation capability.
3Area of stationary object
If the entire pixel array is continuously illuminated and read out in a time-of-flight system, then complete scene coverage is achieved, but power consumption increases and background noise increases
Solution Approach 1:
The patent divides the pixel array into multiple groups that are illuminated and read out in sequential time segments. Each group processes a portion of the scene, allowing the system to maintain complete field of view coverage while reducing instantaneous power consumption and minimizing background noise accumulation by limiting active integration time.
Solution Approach 2:
The patent employs periodic illumination and readout cycles for different pixel groups rather than continuous operation. This time-multiplexed approach allows complete scene coverage over a full frame period while reducing average power consumption and background noise by keeping most pixels inactive during any given integration window.
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 efficient and real-time 3D image acquisition with reduced computational requirements and power consumption by selectively illuminating and reading out only fractional portions of the pixel array, improving precision and reducing background noise.
Implementation Method 1
a sensor that detects the light that is reflected from the object
Implementation Method 2
a light source that directs light at an object... calculate the distance to the object based on the round-trip time
Data Source
AI summary
A time-of-flight sensor includes a pixel array of pixel circuits. A first subset of the pixel circuits is illuminated by reflected modulated light from a portion of an object. A second subset of the pixel circuits is non-illuminated by the reflected modulated light. Each pixel circuit includes a floating diffusion that stores a portion of charge photogenerated in a photodiode in response to the reflected modulated light. A transfer transistor transfers the portion of charge from the photodiode to the floating diffusion in response to modulation by a phase modulation signal. A modulation driver block generates the phase modulation signal and is coupled to a light source that emits the modulated light to the portion of the object. The modulation driver block synchronizes scanning the modulated light emitted by the light source across the object with scanning of the first subset of the pixel circuits across the pixel array.