Abstract
Time-of-flight cameras, based on Photonic Mixer Device (PMD) technology, are capable of measuring distances to objects at high frame rates, however, the measured ranges and the intensity data contain systematic errors that need to be corrected. In this paper, a new integrated range camera self-calibration method via joint setup with a digital (RGB) camera is presented. This method can simultaneously estimate the systematic range error parameters as well as the interior and external orientation parameters of the camera. The calibration approach is based on photogrammetric bundle adjustment of observation equations originating from collinearity condition and a range errors model. Addition of a digital camera to the calibration process overcomes the limitations of small field of view and low pixel resolution of the range camera. The tests are performed on a dataset captured by a PMD[vision]-O3 camera from a multi-resolution test field of high contrast targets. An average improvement of 83% in RMS of range error and 72% in RMS of coordinate residual, over that achieved with basic calibration, was realized in an independent accuracy assessment. Our proposed calibration method also achieved 25% and 36% improvement on RMS of range error and coordinate residual, respectively, over that obtained by integrated calibration of the single PMD camera.
Highlights
Providing three-dimensional information about the real environment is an essential factor for various applications in industry, computer vision, automation, multimedia, robotics, mobile mapping and many more fields
The self-calibration bundle adjustment is performed based on observation equations of image point coordinates on intensity images of both cameras as well as range measurements of the Photonic Mixer Device (PMD) camera
Most pre-researched systematic error sources affecting the range accuracy are taken into account, Image and range observations are adjusted in an integrated bundle adjustment, Problems coherent to small field of view (FoV) of range camera such as high correlation between interior and exterior orientation parameters are overcome, and Specific equipment such as robot arms or laser scanners are not required
Summary
Providing three-dimensional information about the real environment is an essential factor for various applications in industry, computer vision, automation, multimedia, robotics, mobile mapping and many more fields. Time-of-Flight (ToF) devices, based on Photonic Mixer Device (PMD) technology, are becoming increasingly popular solutions in 3D imaging applications [1,2,3,4]. This new generation of active devices can capture range, amplitude and intensity images simultaneously with one array sensor at video rates. Called depth image, each pixel individually measures the distance to the observed point by computing the turnaround time of the modulated near infrared light. The amplitude image shows the signal strength of the active illumination, while the intensity image represents the gray-scale values of pixels. The main advantages of range cameras in comparison with traditional 3D data acquisition systems such as laser scanners or stereo cameras are as follows:
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