Application of lidar techniques to time-of-flight range imaging.

Area of Science:

• Optics and Photonics
• Computer Vision
• Robotics

Background:

• Amplitude-modulated continuous wave (AMCW) time-of-flight (ToF) cameras measure distance using modulated light.
• AMCW ToF suffers from errors like multipath interference, motion, and phase wrapping.
• Existing AMCW ToF systems have limitations in complex or obstructed environments.

Purpose of the Study:

• To modify an AMCW ToF camera for operation in continuous wave (CW) and stepped frequency continuous wave (SFCW) modes.
• To evaluate the performance of CW and SFCW modes for velocity and range measurements.
• To assess the resilience of SFCW range measurements against common AMCW errors.

Main Methods:

• Modified an existing AMCW ToF camera to support CW and SFCW operational modes.
• Measured object velocity using CW mode and compared it to true velocity.
• Evaluated SFCW range accuracy in a complex scene with a translucent sheet, comparing it to AMCW.

Main Results:

• CW mode demonstrated linear velocity measurement (R2=0.9969).
• SFCW range measurements showed resilience to multipath, phase wrapping, and modulation nonidealities.
• In a challenging scenario, SFCW reduced median range error from -1.3m to -0.06m and IQR from 4.0m to 0.18m.

Conclusions:

• CW and SFCW modes offer significant improvements over standard AMCW ToF.
• SFCW mode provides robust range imaging, overcoming key limitations of AMCW.
• The modified ToF camera enhances capabilities for applications requiring accurate distance and velocity sensing.