Rolling Shutter CMOS Depth Imaging via Signal Down-Conversion
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Solution Overview
Problem
Standard image sensors are bandwidth limited when capturing the phase of high-frequency signals used in indirect time-of-flight depth imaging, making it difficult to effectively determine the range of objects in environments, such as those traversed by vehicles.
Innovation Solution
A method and system that down-converts the reflected signal using a mixing frequency, allowing standard image sensors to capture the information by modulating the intensity or quantum efficiency of the sensor array, and processing the signal to determine the range of objects based on the time-of-flight of the signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If standard image sensors are used to capture high-frequency AMCW signals, then the device complexity is reduced, but the measurement precision deteriorates due to bandwidth limitations
Solution Approach 1:
The patent changes the frequency parameter of the signal by using down-conversion to transform the high-frequency reflected signal (in the Megahertz range) into a lower-frequency intermediate signal that standard image sensors can accurately capture while preserving the phase information needed for depth measurement
Solution Approach 2:
The patent introduces an intermediary processing stage that includes mixing the reflected signal with a reference signal and applying a low-pass filter to extract the phase information at a lower frequency, enabling standard sensors to measure high-frequency signals indirectly with high precision
2Productivity
If high-frequency AMCW signals are used for depth imaging, then the productivity is improved by enabling accurate depth measurement, but the device complexity increases due to bandwidth requirements
Solution Approach 1:
The patent uses mixing and low-pass filtering as intermediary operations to bridge between the high-frequency reflected signal and the bandwidth-limited standard image sensor, enabling depth imaging capability while keeping the sensor system relatively simple
Solution Approach 2:
The patent replaces the need for complex high-bandwidth hardware with simpler signal processing operations (mixing and filtering) that can be implemented with standard components, achieving the same depth imaging functionality
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 accurate determination of object range using standard image sensors, overcoming bandwidth limitations and providing effective depth imaging capabilities for autonomous vehicles and other applications.
Implementation Method 1
The reflected signal is modulated using a mixing frequency to form a down-converted signal
Implementation Method 2
The down-converted signal is recorded at a sensor array of the vehicle
Implementation Method 3
The range of the object to the vehicle is determined using the down-converted signal... determining a time-of-flight of the reflected signal and a range to the object from the time-of-flight
Data Source
AI summary
A vehicle, imaging system and method of determining a range of an object to a vehicle. The imaging system includes a light source, a receiver and a processor. The light source is configured to transmit a source signal at a source frequency at an object, wherein the source signal is reflected from the object to create a reflected signal. The receiver includes a sensor array and is configured to modulate the reflected signal at a mixing frequency to generate a down-converted signal and record the down-converted signal at the sensor array. The processor is configured to determine a range of the object to the vehicle using the down-converted signal.