To the Graduate Council: I am submitting herewith a thesis written by ...

Chapter 3: Data Collection and Modeling 29where i and j respectively are the horizontal and vertical pixel positions, β (= 90degrees) and α is the illumination angle and the camera view angle respectively, andB is the base line distance between camera and the laser source. These are theimportant design parameters that decide the field of view of the scanning mechanism.External parameters such as temperature (T), environmental light (η), surfacereflectance and color of the objects (χ) and the trajectory of the relative motion (µ)also influence the quality of range scans. We have characterized the scanner tominimize the effect of such external factors. We have deduced that the warm up timeof 40-50 minutes yielded stable and reliable data. We ignore effects of environmentaltemperature. We also realize that the Ranger is sensitive to light and tends to introducesignificant error when the ambient illumination is strong. Most of the scanning that wedo inside the lab is performed with minimal lighting. We have learned that the effectof illumination can be compensated by the use of a powerful laser (> 100mW andwavelength 685nm) that we propose to use for scanning under the vehicle. We haveperformed a simple experiment to characterize the sensor’s behavior to the color andreflectance of the objects. We have tried to image wooden and metal rectangularblocks of the same size and compared the range measurements. We have concludedthat the IVP range sensor is not influenced by surface reflectance but black objectsbecause of their laser beam reflectance characteristics need modification. We havesimply painted the object with a lighter color to work around this sensitivity. We havesimulated the triangulation geometry of the Ranger system in MATLAB to understandthe effect of different sensor parameters that influence the scanning mechanism andthe process of calibration.In Figure 3.2 we demonstrate the principle behind range acquisition using the IVPRange scanner. We show the sheet-of-the-light laser falling on a target object. Thelaser line that provides cues about the surface shape of the object is called a surfaceprofile. By traversing the entire object either by moving the sensor setup or the scene,a sequence of surface profiles is accumulated as a range image.Equation 3.2 is the reduced form of range r as a function of the geometry, focal length(b 0 is the distance between the lens and the sensor approximated as the focal length ofthe lens) and sensor offset position in the 512 x 512 CCD chip assuming that we havecompensated for the external sensor sensitivity parameters.r( s )( b0tanα− s )cosα= B= Bb0−( b0tanα− s )sinαcosαf tan α - sf + s tanα(3.2)