Time of Flight Pixel Delay Circuit Transistor Gate Length
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Solution Overview
Problem
Time of flight imaging systems face challenges in achieving accurate distance calculations due to signal delays, particularly in small devices, where design rules limit metal interconnect width and increase processing requirements, complicating real-time 3D image creation.
Innovation Solution
The implementation of a time of flight sensing system with varying transistor gate lengths in delay circuits to compensate for signal propagation delays, ensuring synchronized sync signals across the pixel array, and the use of a stacked chip scheme with a pixel die and ASIC die for efficient processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital algorithms are used to calibrate the delayed signal, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent changes the physical parameter of transistor gate length to create different propagation delays. By varying the gate length of transistors in the sync signal path, the system introduces controlled time delays that compensate for signal propagation variations without requiring complex digital calibration algorithms, thus improving measurement precision while reducing processing complexity
Solution Approach 2:
The patent introduces delay circuits with specifically designed transistor gate lengths as intermediary elements between the light source and sensor. These intermediary delay circuits act as mediators that pre-compensate for signal propagation delays, allowing the system to achieve accurate time of flight measurements without relying on complex post-processing algorithms
2Measurement precision
If metal interconnect resistance and capacitance are reduced, then measurement precision is improved, but device complexity increases
Solution Approach 1:
Instead of reducing metal interconnect resistance and capacitance through complex interconnect design, the patent changes the parameter of transistor gate length to control signal propagation delay. This approach achieves the desired delay compensation without requiring complex interconnect design modifications, thus improving measurement precision while avoiding increased device complexity
3Measurement precision
If stereo imaging technique is used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces the mechanical/optical approach of stereo imaging (requiring multiple cameras with physical separation) with an electronic time of flight measurement system. By using light emission and detection with electronic timing, the system achieves 3D depth measurement without requiring complex multi-camera setups, thus improving measurement precision while reducing device complexity
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 allows for accurate and efficient time of flight calculations, enabling real-time 3D image creation with reduced processing requirements and improved performance in small devices.
Implementation Method 1
delays in the electronic signals can compromise the time of flight calculations that indicate the distance of the object from the sensor
Implementation Method 2
The time between the emission from the light source and the detection of reflected light by the sensor indicates the distance of the object in relation to the sensor
Implementation Method 3
a light source that directs light at an object and a sensor that detects the light that is reflected from the object
Data Source
AI summary
A time of flight sensor includes control circuitry and a time of flight pixel array. The control circuitry is coupled to synchronously send a sync signal. The time of flight pixel array includes a plurality of time of flight pixel cells. Each one of the time of flight pixel cells includes a photosensor and a delay circuit. The photosensor is configured to generate an image signal in response to receiving photons from a light pulse reflected from an object. The delay circuit is coupled to generate a delayed sync signal in response to the sync signal. The delay circuit includes a delay transistor. The time of flight pixel array includes a transistor gradient where a transistor gate length of the delay transistor varies so that each of the time of flight pixel cells receive their respective delayed sync signal at a same time.