scholarly journals How far away is your phone in this picture? Determining object distance and size in a 2D scene

2021 ◽  
Vol 21 (9) ◽  
pp. 2580
Author(s):  
John Jong-Jin Kim ◽  
Laurence Harris
Keyword(s):  
Object Distance

Biomechanical Models for Radial Distance Determination by the Rat Vibrissal System

2007 ◽  
Vol 98 (4) ◽  
pp. 2439-2455 ◽  
Author(s):  
J. Alexander Birdwell ◽  
Joseph H. Solomon ◽  
Montakan Thajchayapong ◽  
Michael A. Taylor ◽  
Matthew Cheely ◽  
...  
Keyword(s):  
Angular Position ◽  
Three Dimensional ◽  
Radial Distance ◽  
Rate Of Change ◽  
Dynamic State ◽  
Rhythmic Movements ◽  
Tactile Information ◽  
Biomechanical Models ◽  
Object Distance ◽  
Dimensional Object

Rats use active, rhythmic movements of their whiskers to acquire tactile information about three-dimensional object features. There are no receptors along the length of the whisker; therefore all tactile information must be mechanically transduced back to receptors at the whisker base. This raises the question: how might the rat determine the radial contact position of an object along the whisker? We developed two complementary biomechanical models that show that the rat could determine radial object distance by monitoring the rate of change of moment (or equivalently, the rate of change of curvature) at the whisker base. The first model is used to explore the effects of taper and inherent whisker curvature on whisker deformation and used to predict the shapes of real rat whiskers during deflections at different radial distances. Predicted shapes closely matched experimental measurements. The second model describes the relationship between radial object distance and the rate of change of moment at the base of a tapered, inherently curved whisker. Together, these models can account for recent recordings showing that some trigeminal ganglion (Vg) neurons encode closer radial distances with increased firing rates. The models also suggest that four and only four physical variables at the whisker base—angular position, angular velocity, moment, and rate of change of moment—are needed to describe the dynamic state of a whisker. We interpret these results in the context of our evolving hypothesis that neural responses in Vg can be represented using a state-encoding scheme that includes combinations of these four variables.

scholarly journals Effect of Eye-Object Distance on Body Sway during Galvanic Vestibular Stimulation

2018 ◽  
Vol 8 (11) ◽  
pp. 191 ◽  
Author(s):  
Osamu Aoki ◽  
Yoshitaka Otani ◽  
Shinichiro Morishita
Keyword(s):  
Healthy Subjects ◽  
Center Of Pressure ◽  
Force Plate ◽  
Distance Effect ◽  
Vestibular Stimulation ◽  
Galvanic Vestibular Stimulation ◽  
Body Sway ◽  
Mean Square ◽  
Visual Condition ◽  
Object Distance

Gazing at objects at a near distance (small eye-object distance) can reduce body sway. However, whether body sway is regulated by movement in the mediolateral or anteroposterior direction remains unclear. Galvanic vestibular stimulation (GVS) can induce body tilting in the mediolateral or anteroposterior direction. This study examined the directionality of the eye-object distance effect, using body-tilting GVS manipulations. Ten healthy subjects (aged 21.1 ± 0.3 years) stood on a force plate covered with a piece of foamed rubber and either closed their eyes or gazed at a marker located 0.5 m, 1.0 m, or 1.5 m in front of them. The GVS polarities were set to evoke rightward, forward, and backward body tilts. To compare the effects of eye-object distance in the mediolateral and anteroposterior directions, the root mean square (RMS) of the center of pressure (COP) without GVS was subtracted from the COP RMS during GVS. For swaying in the mediolateral direction, significant visual condition-related differences were found during rightward and forward GVS (p < 0.05). Thus, reductions in mediolateral body sway are more evident for smaller eye-object distances during rightward GVS. It would be appropriate to use body-tilting GVS to detect the directionality of the eye-object distance effect.

REAL-TIME PHOTOGRAMMETRY AT THE DIGITAL PHOTOGRAMMETRIC STATION (DIPS) OF ETH ZURICH

1987 ◽  
Vol 41 (2) ◽  
pp. 181-199 ◽  
Author(s):  
Armin W. Gruen ◽  
Horst A. Beyer
Keyword(s):  
Real Time ◽  
Three Dimensional ◽  
Development Program ◽  
Bundle Adjustment ◽  
Object Distance ◽  
Federal Institute ◽  
Adjustment Program ◽  
Three Dimensional Measurement ◽  
Institute Of Technology ◽  
Processing Steps

Real-time photogrammetry (RTP) is a non-contact three-dimensional measurement technique with a response time of one video cycle. As part of a research and development program for digital and real-time photogrammetry, the Institute of Geodesy and Photogrammety at the Swiss Federal Institute of Technology, Zurich, Switzerland, has established the Digital Photogrammetric Station (DIPS). The hardware and software of this development system is explained. Hardware aspects of solid-state cameras relevant to camera calibration for RTP are discussed. An off-line bundle adjustment program with additional parameters has been installed. An initial calibration and point positioning test using this program and existing image processing algorithms has been performed. The processing steps and results are analyzed. Accuracies, as computed from object space check points, in planimetry of 1:5000 or 0.09 pixel pitch, in depth of 0.08%c of object distance, have been achieved.

scholarly journals Refractive Two-View Reconstruction for Underwater 3D Vision

2019 ◽  
Vol 128 (5) ◽  
pp. 1101-1117 ◽  
Author(s):  
François Chadebecq ◽  
Francisco Vasconcelos ◽  
René Lacher ◽  
Efthymios Maneas ◽  
Adrien Desjardins ◽  
...  
Keyword(s):  
Structure From Motion ◽  
Real Data ◽  
Reconstruction Method ◽  
Underwater Imaging ◽  
Shape Estimation ◽  
Camera Model ◽  
Projection Model ◽  
3D Vision ◽  
Object Distance ◽  
View Reconstruction

AbstractRecovering 3D geometry from cameras in underwater applications involves the Refractive Structure-from-Motion problem where the non-linear distortion of light induced by a change of medium density invalidates the single viewpoint assumption. The pinhole-plus-distortion camera projection model suffers from a systematic geometric bias since refractive distortion depends on object distance. This leads to inaccurate camera pose and 3D shape estimation. To account for refraction, it is possible to use the axial camera model or to explicitly consider one or multiple parallel refractive interfaces whose orientations and positions with respect to the camera can be calibrated. Although it has been demonstrated that the refractive camera model is well-suited for underwater imaging, Refractive Structure-from-Motion remains particularly difficult to use in practice when considering the seldom studied case of a camera with a flat refractive interface. Our method applies to the case of underwater imaging systems whose entrance lens is in direct contact with the external medium. By adopting the refractive camera model, we provide a succinct derivation and expression for the refractive fundamental matrix and use this as the basis for a novel two-view reconstruction method for underwater imaging. For validation we use synthetic data to show the numerical properties of our method and we provide results on real data to demonstrate its practical application within laboratory settings and for medical applications in fluid-immersed endoscopy. We demonstrate our approach outperforms classic two-view Structure-from-Motion method relying on the pinhole-plus-distortion camera model.

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