<title>Practical range camera calibration</title>

Abstract

This paper presents a calibration procedure adapted to a range camera intended for space applications. The range camera, which is based upon an auto-synchronized triangulation scheme, can measure objects from about 0.5 m to 100 m. The eld of view is 30 30 . Objects situated at distances beyond 10 m can be measured with the help of cooperative targets. Such a large volume of measurement presents signicant c hallenges to a precise calibration. A two-step methodology is proposed. In the rst step, the close-range volume (from 0.5 m to 1.5 m) is calibrated using an array of targets positioned at known locations in the eld of view of the range camera. A large number of targets are evenly spaced in that eld of view because this is the region of highest precision. In the second step, several targets are positioned at distances greater than 1.5 m with the help of an accurate theodolite and electronic distance measuring device. This second step will not be discussed fully here. The internal and external parameters of a model of the range camera are extracted with an iterative nonlinear simultaneous least-squares adjustment method. Experimental results obtained for a close-range calibration suggest a precision along the , and axes of 200 m, 200 m, and 250 m, respectively, and a bias of less than 100 m in all directions.

Electromechanical 3D Optoelectronic Scanners: Resolution Constraints and Possible Ways of Improvement

“…It is beyond the scope of this paper to discuss the details of operation of the scanner and the exact mathematical model. This information is available from previous publications where the scanner is operated in imaging mode (Blais et al, 1988;Beraldin et al, 1993;Beraldin et al, 2000). Here, we will use the simplified models illustrated in Figure 10 to model range measurement and to associate object pose estimation obtained using video camera models shown in Figures 10 and 11 and techniques discussed in section 4. where f is the focal length of the lens, d is the triangulation base, θ is the deflection angle following the x-axis, and p is the position of the imaged laser spot of the position sensor (see (Blais et al, 1988) for details).…”

Modeling an auto-synchronizing laser range scanner

“…The mirror angles were controlled by entering a value between -1 and 1 corresponding to the normalized minimum and maximum mirror angles. According to [3] the prototype of Figure 4 of the LRS has a maximum field of view (FOV) of 30º by 30º. The prototype of Figure 2 has a larger FOV.…”

“…where out is the angle of the fixed output mirror, in is the angle of the fixed input mirror and U is an estimator for the deflection of the laser (line starting at and passing through the point of reflection with the y-axis mirror f 3 ) and the imaging axis (line starting at and passing through the point of reflection with the yaxis mirror a 3 The intersection point f 3 of the laser with the y-axis mirror in the LRS frame of reference can now be estimated. It can be seen in Figure 3 that the intersection of the laser with the y-axis mirror is in the (x,y)-plane so we define f 3z as zero.…”

“…Here we defined the maximum and minimum angular deviations as 15º and -15º respectively. The galvanometers controlling each mirror are driven by 16-bit D/A converters [3] so the -1 to 1 value was quantized [8] and converted to an integer value between -32768 and 32767.…”

“…The peak location was normalized to a value between 0 and 1. The CCD array and its peak detector produce a 16-bit value corresponding to 1/64 of a pixel [3] so the peak value was quantized [8] and converted to an integer between 0 and 32767. If the intersection point and the output ray origin are the same point then a peak value of 0 is returned to indicate no peak location.…”