Hybrid TOF-Triangulation Range Sensor for Near and Far Objects
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Solution Overview
Problem
Existing 3D imaging technologies face challenges in accurately determining the range of objects under difficult conditions such as low light, bad weather, and strong ambient light, and struggle to efficiently combine direct time-of-flight (TOF) and triangulation methods for both distant and near objects.
Innovation Solution
A range sensor system that combines direct TOF and triangulation in a single image sensor, using a light source to project a sheet of light at an angle, an offset image sensor, and collection optics, with a controller determining object ranges based on TOF for distant objects and triangulation for near objects, while employing range gating and a single photon avalanche diode (SPAD) array to reduce power consumption and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct TOF method is used for distant objects, then measurement precision is improved, but device complexity increases due to need for additional components
Solution Approach 1:
The patent combines direct TOF and triangulation methods within a single imaging sensor device. The imaging sensor is configured to perform both TOF measurements (for distant objects) and triangulation measurements (for near objects) simultaneously, eliminating the need for separate devices and reducing overall system complexity while maintaining measurement precision across different object distances.
Solution Approach 2:
The imaging sensor is designed with multi-functionality to perform both direct TOF and triangulation operations. By integrating multiple measurement capabilities into a single sensor, the device can adaptively switch between methods based on object distance, improving measurement precision without proportionally increasing device complexity.
2Measurement precision
If triangulation method is used for near objects, then measurement precision is improved, but it fails for distant objects
Solution Approach 1:
The system dynamically selects between triangulation and direct TOF methods based on the distance to the object. For near objects, triangulation provides superior precision, while for distant objects, direct TOF takes over. This dynamic adaptation ensures measurement precision is maintained across the full range of object distances, resolving the limitation of triangulation being ineffective for distant objects.
3Measurement precision
If SPAD array operates in avalanche mode, then detection sensitivity is improved, but power consumption increases
Solution Approach 1:
The operating mode of the SPAD array is changed based on measurement requirements. The system can switch between linear mode (lower power consumption) and avalanche mode (higher sensitivity) depending on the ambient light conditions and measurement needs. This parameter change allows the system to optimize the balance between detection sensitivity and power consumption for different operating scenarios.
4Measurement precision
If range gating is applied, then measurement precision under difficult conditions is improved, but loss of information increases due to excluded ranges
Solution Approach 1:
The measurement range is segmented into different zones handled by different methods. Range gating is applied selectively to exclude only those ranges that are known to be problematic (e.g., extremely distant objects or objects in specific interference zones), while preserving measurement capability for all other ranges. This segmentation approach maintains measurement precision for relevant objects while minimizing information loss by only excluding genuinely problematic ranges.
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 enhances the accuracy and efficiency of range determination, improves performance under challenging conditions, and reduces power consumption by effectively using both TOF and triangulation methods, while minimizing interference and noise.
Implementation Method 1
using a single photon avalanche diode (SPAD) array
Implementation Method 2
measuring the round-trip time it takes for a light signal to travel between a camera and the 3D object
Data Source
AI summary
A range sensor and a method thereof. The range sensor includes a light source configured to project a sheet of light at an angle within a field of view (FOV); an image sensor offset from the light source; collection optics; and a controller connected to the light source, the image sensor, and the collection optics, and configured to determine a range of a distant object based on direct time-of-flight and determine a range of a near object based on triangulation. The method includes projecting, by a light source, a sheet of light at an angle within an FOV; offsetting an image sensor from the light source; collecting, by collection optics, the sheet of light reflected off objects; and determining, by a controller connected to the light source, the image sensor, and the collection optics, a range of a distant object based on direct time-of-flight and a range of a near object based on triangulation simultaneously.