Time-of-Flight Depth Sensing With Multiple Modulation Frequencies
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Solution Overview
Problem
Time-of-flight sensors are unreliable in environments with varied lighting and multiple objects at different distances, leading to ambiguous returns and inefficient data processing, which can result in inaccurate object detection and obstacle identification for safe vehicle navigation.
Innovation Solution
The use of multiple modulation frequencies for time-of-flight sensors to improve depth measurement accuracy, combining data from different configurations to disambiguate depths and filter pixels based on intensity thresholds, thereby enhancing sensor data reliability and object detection in complex environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single modulation frequency is used for time-of-flight sensors, then the device complexity is reduced, but measurement precision deteriorates due to ambiguous depth returns in complex environments
Solution Approach 1:
The patent changes the modulation frequency parameter of the time-of-flight sensor to resolve depth ambiguity. By capturing depth information at multiple modulation frequencies (e.g., first frequency for long range, second frequency for short range), the system disambiguates depth measurements that would be incorrect at a single frequency, thereby improving measurement precision without requiring fundamentally different sensor hardware.
2Measurement precision
If multiple modulation frequencies are used to disambiguate depth, then measurement precision improves, but processing time increases due to multiple data captures and computations
Solution Approach 1:
The patent performs preliminary action by capturing depth information at multiple modulation frequencies before object detection and classification are performed. This multi-frequency depth data is prepared in advance and used to filter candidate objects and resolve ambiguities early in the processing pipeline, reducing the overall processing time compared to resolving ambiguities after initial detection.
Solution Approach 2:
The patent segments the depth measurement process by using different modulation frequencies for different depth ranges. The first modulation frequency captures long-range depth information while the second captures short-range information, allowing the system to process and filter objects at different depth zones independently, thereby managing processing complexity more efficiently.
3Reliability
If multiple modulation frequencies are used, then reliability of sensor data improves in varied lighting environments, but device complexity increases
Solution Approach 1:
The patent changes the modulation frequency parameter to improve reliability in varied lighting conditions. Different modulation frequencies are less susceptible to interference from ambient light at different wavelengths and intensities. By switching frequencies based on environmental conditions or using multiple frequencies simultaneously, the system maintains reliable depth measurement across diverse lighting environments without adding physical shielding or filtering components.
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 provides more accurate and reliable depth measurements, reducing ambiguity and improving the ability to identify and navigate around obstacles, leading to safer and more efficient vehicle operation in diverse environments.
Implementation Method 1
a first frame includes first intensity information and first depth information captured by a time-of-flight sensor in a first configuration
Implementation Method 2
The sensor can be configured to output sensor data in a quadrature format, for example, by determining a phase shift between the carrier and the response carrier
Data Source
AI summary
Sensors, including time-of-flight sensors, may be used to detect objects in an environment. In an example, a vehicle may include a time-of-flight sensor that images objects around the vehicle, e.g., so the vehicle can navigate relative to the objects. The sensor may generate first image data at a first configuration and second image data at a second configuration. An estimated depth of an object may be determined from the first image data, and an actual depth of the object may be determined from the second image data, based on the estimated depth. In examples, the first and second configurations have different modulation frequencies such that a nominal maximum depth in the first configuration is greater than the nominal maximum depth in the second configuration.