945 
INTEGRATED RANGE CAMERA CALIBRATION 
USING IMAGE SEQUENCES FROM HAND-HELD OPERATION 
Wilfried Karel 
Christian Doppler Laboratory for Spatial Data from Laser Scanning and Remote Sensing at the Institute of 
Photogrammetry and Remote Sensing, Vienna University of Technology Gusshausstrasse 27-29 / E122, 1040 Vienna, 
Austria - wk@ipf.tuwien.ac.at 
KEY WORDS: Imaging Systems, 3D Sensors, Calibration, Close Range Photogrammetry, Video Camera, Machine Vision 
ABSTRACT: 
This article concentrates on the integrated self-calibration of both the interior orientation and the distance measurement system of a 
time-of-flight range camera that employs amplitude-modulated, continuous-wave, near-infrared light (photonic mixer device - PMD). 
In contrast to other approaches that conduct specialized experiments for the investigation of individual, potential distortion factors, in 
the presented approach all calculations are based on the same data set being captured under near-real-world conditions, guided by 
hand and without auxiliary devices serving as high-order reference. Flat, circular targets stuck on a planar whiteboard and with 
known positions are automatically tracked throughout the amplitude layer of long image sequences. These image observations are 
introduced into a bundle block adjustment, which on the one hand results in the determination of the camera’s interior orientation 
and its temporal variation. On the other hand, the reconstructed exterior orientations and the known planarity of the imaged board 
allow for the derivation of reference values of the actual distance observations. These deviations are checked on relations with the 
reference distance itself, the observed signal amplitude, the integration time, the angle of incidence, and with both the position in the 
field of view and in object space. Eased by the automatic reconstruction of the camera’s trajectory and attitude, several thousand 
frames are processed, leading to comprehensive statistics. 
1. INTRODUCTION 
Range Imaging (RIM) denotes the capture of distances at the 
pixels of a focal plane array using simultaneous time-of-flight 
measurements. Thereby, the round-trip time of the emitted 
signal and hence the object distance may be determined in 
various ways. Currently, alternatives employing nanosecond 
Laser pulses are highly investigated. So-called Flash LADARs 
or Laser Radars utilize avalanche photo diodes (APD) for 
photon detection, eventually supported by photo cathodes for 
signal amplification (Stettner et al., 2004), and may facilitate 
maximum observable distances of up to a kilometre. Another 
technique, called Time-Correlated Single Photon Counting, 
employs the most sensitive single photon avalanche diodes 
(SPAD) as detectors (Aull et al., 2002, Niclass et al., 2007, 
Pancheri et al., 2007, Wallace et al., 2001), minimizing the 
requirements on the illumination power. In Multiple Double 
Short Time Integration (MDSI), different fractions of the echo 
energy are captured in consecutive images by varying the 
shutter speed and using conventional chips that integrate the 
irradiance (Mengel et al., 2001, Elkhalili et al., 2004). The 
requirements for nanosecond Laser pulses or high-speed 
shutters and the integration of highly precise, miniaturized 
timing circuitry however boost the complexity and costs of all 
these systems. 
Photonic mixer devices (PMD, lock-in pixels) employ 
incoherent, near-infrared, amplitude-modulated, continuous 
wave (AM-CW) light and determine the signal phase shift and 
hence the object distance by mixing the emitted with the 
returned signal at every pixel (Spirig et al., 1997, Lange et al., 
1999). As on the one hand, the illumination unit of PMD close- 
range cameras may be realized with low-cost LED arrays, and 
on the other hand, the operation point of the system is limited to 
the single frequency of modulation, implying that the demands 
on the electronic components are lower (Buttgen et al., 2005), 
the purchase costs are comparatively low, lying in the range of 
professional SLR cameras. 
The present article concentrates on this latter technique, 
implemented in the Swissranger™ SR-3000 by MESA Imaging 
AG. This instrument samples the correlation function of the 
emitted and returned signal one after another at every quadrant 
of the modulation period. It features a sensor resolution of 
144x176 pixels, a fix-focus lens, range and amplitude data 
encoded with 16 bit, an overall ranging precision of a few 
centimetres, and a maximum range of 7.5m when using the 
default modulation frequency. As other PMD cameras, its 
ranging system suffers from large systematic distortions 
reaching decimetres, why comprehensive calibration methods 
are needed in order to harness the potentials of RIM for 
geometry- and quality-oriented realms. 
1.1 Related Work 
For the correct reconstruction of the object space imaged by a 
range camera, knowledge of its interior orientation is an 
essential prerequisite in combination with undistorted range 
observations. Westfeld (2007) determines the intrinsic 
projection parameters by application of conventional 
photogrammetric techniques to amplitude images, and reports 
an unstable position of the principal point. Having calibrated 
the camera optics, Lindner and Kolb (2006) gather range 
images at known distances from a planar target and experience 
the deviations of the range measurements as being partly of 
periodic nature. Steitz and Pannekamp (2005) report influences 
of the angle of incidence and the surface type on the range 
observations. Kahlmann et al. (2006) perform elaborate 
laboratory experiments and also reveal the partly cyclic non- 
linearities of the distance observations. Additionally,