cs.CVMar 6, 2026

Spatial Calibration of Diffuse LiDARs

Authors: Nikhil Behari, Ramesh Raskar

Organizations: MIT

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Abstract

Diffuse direct time-of-flight LiDARs report per-pixel depth histograms formed by aggregating photon returns over a wide instantaneous field of view, violating the single-ray assumption behind standard LiDAR-RGB calibration. We present a simple spatial calibration procedure that estimates, for each diffuse LiDAR pixel, its footprint (effective support region) and relative spatial sensitivity in a co-located RGB image plane. Using a scanned retroreflective patch with background subtraction, we recover per-pixel response maps that provide an explicit LiDAR-to-RGB correspondence for cross-modal alignment and fusion. We demonstrate the method on the ams OSRAM TMF8828.

Figures & tables

Figure 2: Pixel aggregation modes on the ams OSRAM TMF8828 diffuse dToF LiDAR [ 1 ] . The sensor supports multiple spatial aggregation layouts; in each mode, reported pixels integrate photon returns over a wide instantaneous field-of-view under flood illumination. Our example calibration uses 3 ×\times 3 Wide mode ( P=9P{=}9 ).
Figure 3: Custom rigid mount for co-located diffuse LiDAR (TMF8828) and RGB (RealSense D435i). Left: CAD mount design (dimensions in mm), showing the fixed sensor-to-sensor geometry and mounting hole layout. Right: real capture mount used for our calibration data collection.
Figure 4: Retroreflective patch scan grid sampled with a UR10 robot arm. We traverse an 80×4580{\times}45 grid ( K=3600K{=}3600 ) using a snake pattern to reduce motion between points. At each grid location, we record synchronized RGB frames and per-pixel LiDAR histograms; an identical patch-removed scan is also captured for background subtraction.
Figure 5: Per-pixel spatial response maps for the TMF8828 3 ×\times 3 Wide mode overlaid on the co-located RGB image. Nonzero regions show the pixel’s effective support in RGB coordinates, and the response magnitudes encode relative spatial sensitivity within that support.
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