Calibration Method of the Monocular Omnidirectional Stereo Camera

TL;DR

This paper presents a new calibration method for a compact omnidirectional stereo camera using hyperbolic mirrors, significantly reducing calibration and distance measurement errors for autonomous driving applications.

Contribution

A novel calibration approach that accounts for complex distortions and offsets, improving accuracy over conventional methods for omnidirectional stereo cameras.

Findings

Calibration error reduced by 6.0 and 4.3 times for upper and lower images.

Distance measurement error decreased to 4.9% (random) and 5.7% (systematic) up to 14 meters.

Almost ninefold improvement in measurement accuracy compared to traditional calibration methods.

Abstract

Compact and low-cost devices are needed for autonomous driving to image and measure distances to objects 360-degree around. We have been developing an omnidirectional stereo camera exploiting two hyperbolic mirrors and a single set of a lens and sensor, which makes this camera compact and cost efficient. We establish a new calibration method for this camera considering higher-order radial distortion, detailed tangential distortion, an image sensor tilt, and a lens-mirror offset. Our method reduces the calibration error by 6.0 and 4.3 times for the upper- and lower-view images, respectively. The random error of the distance measurement is 4.9% and the systematic error is 5.7% up to objects 14 meters apart, which is improved almost nine times compared to the conventional method. The remaining distance errors is due to a degraded optical resolution of the prototype, which we plan to make further improvements as future work.