Binocular Tracking Based on Virtual Horopters

This paper presents a stereo active vision system which performs tracking tasks on smoothly moving objects in complex backgrounds. Dynamic control of the vergence angle adapts the horopter geometry to the target position and allows to pick it up easily on the basis of stereoscopic disparity features. We introduce a novel vergence control strategy based on the computation of "virtual horopters" to track a target movement generating rapid changes of disparity. The control strategy is implemented on a binocular head, whose right and left pan angles are controlled independently. Experimental results of gaze holding on a smoothly moving target translating and rotating in a complex surrounding demonstrate the efficiency of the tracking system. 1 Introduction The importance of eye movement to biological visual systems is obvious. In contrast, controlled camera movement have played a small role in computer vision research, but are becoming increasingly recognized as important capabilities in ..

Effects of the pollution by petroleum on the tracheids along the stem of Podocarpus lambertii Klotzsch ex Endl., Podocarpaceae

Podocarpus lambertii Klotzsch ex Endl. (Podocarpaceae) is native and a member of the Pinophyta (Gymnosperm) of southern Brazil, locally known as "pinheiro-bravo". The present work aims to investigate the effects of petroleum on the tracheids dimensions. Wood samples from twenty individuals were studied along the stem, ten being exposed to pollution and ten used as a control set. The wood samples were collected from incisions at three levels: at the ground level, and one and two metres above the ground level. From these samples, sub-samples were selected at the border of the growth layers in the vascular cambium-medulla direction. The methodology followed that traditionally recommended for plant anatomy studies, with analyses done by light microscopy (OLYMPUS - BX41) assisted by the software Image Pro-plus for measurements. Comparison of the individuals exposed to petroleum with the control set, showed that the length, diameter and cell wall width of the tracheids of the former were smaller, a trend which was statistically significant according to the Student's t-test. These traits were observed mainly on the tracheids of the last growth layer, corresponding to the year in which the individuals were exposed to petroleum