Camera hardware setup: NUFRL Research Collaboration

Camera hardware details for test platform. This gallery details the time synchronization rig built for a research collaboration between myself and Abhinav Kowkuntla at the NU Field Robotics Lab (NUFRL) in fall 2025.

Hardware for Time-Sync

Slide describes the optical chopper wheel.

Expected synchronization

Slide representing the expected temporal synchronization between RGB and IR camera frames. Time sync needed to be to within 5 milliseconds.

Cross modal rig (front)

View of the test platform with mounted stereo RGB and stereo IR cameras.

Cross modal rig (top)

Thermal chopper rig

View of the thermal chopper rig showing timing control electronics, power infrastructure, displays, and Arduino. Optical encoder built into motor is used to regulate wheel angular velocity with PID feedback controller.

Thermal chopper rig

View of the thermal chopper rig showing gearmotor. Optical encoder built into gearmotor is used to regulate wheel angular velocity with PID feedback controller.

Thermal chopper rig

Thermal chopper wheel binary encoding may be read off at horizontal or vertical edge. I chose materials and colors to ensure there would be sufficient contrast to both visible and far-IR sensors. The contrast schemes are in fact inverted of each other; in visible light the wheel is light and the background dark- in IR the wheel is dark and the background bright.

Thermal chopper wheel at 8400 nm IR

At calibration time, each frame is aligned with the time axis by reading the 0-29 count off the wheel face, and comparing it between the RGB and IR images. Because the wheel spins at 2 Hz, each of the 30 unique radians counts off 1/60th of a second, or 16.7 milliseconds minimum resolution. In practice its about 1/4 of that (4 ms) because you can estimate partial exposures with reasonable accuracy.

Chopper wheel Onshape CAD model

Waterjet cutting wheel

Thermal chopper wheel was fabricated in-house on the ProtoMax waterjet cutter.

Thermal chopper wheel

I designed the wheel to align with our 30 and 60 Hz camera frame frequencies. It has 30 binary-encoded radians, reading 0-29.

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