Unmanned aerial vehicles are increasingly being tasked to connect to payload objects or docking stations for the purposes of package transport or recharging. However, autonomous docking creates challenges in that the air vehicle must precisely position itself with respect to the dock, oftentimes in the presence of uncertain winds and measurement errors. This paper describes an autonomous docking mechanism comprising a static ring and actuated legs, coupled with an infrared tracking device for closed-loop docking maneuvers. The dock's unique mechanical design enables precise passive positioning such that the air vehicle slides into a precise location and orientation in the dock from a wide range of entry conditions. This leads to successful docking in the presence of winds and sensor measurement errors. A closed-loop infrared tracking system is also described in which the vehicle tracks an infrared beacon located on the dock during the descent to landing. A detailed analysis is presented describing the interaction dynamics between the aircraft and the dock, and system parameters are optimized through the use of trade studies and Monte Carlo analysis with a three degree-of-freedom simulation model. Experimental results are presented demonstrating successful docking maneuvers of an autonomous air vehicle in both indoor and outdoor environments. These repeatable docking experiments verify the robustness and practical utility of the dock design for a variety of emerging applications.

Background: Depth-inversion illusions (DII) involve stimuli for which physically distant points are perceived to be closer to observers than physically near points. Schizophrenia (SZ) patients are less likely to perceive DII as strongly as controls. In particular, there is a negative correlation between the tendency to obtain DII and positive SZ symptoms (Keane et al. 2013). Objectives: First, to test the hypothesis that the tendency to obtain DII correlates negatively with delusional ideation in healthy controls, since delusion is an important positive SZ symptom. Second, to ascertain the frequency with which individuals in the general population perceive DII. Methods: We developed a test in psiTurk to obtain data from hundreds of participants. We assess DII tendency by testing performance with DII stimuli, and we measure delusional ideation adapting Peters Delusions Inventory (PDI; Peters et al. 1999) into an online version. We used two classes of 3D objects: perceptually stable unambiguous objects that serve as “catches”: banana, apple, toy, etc.; and bistable objects that can exhibit DII but can also be perceived without depth inversion: human hollow mask, monkey hollow mask and a reverse-perspective scene. To obtain depth from motion, each object was rotated clockwise or counterclockwise around a vertical axis. We used 3-D probes embedded in strategic locations of the objects to infer whether participants obtained the veridical or illusory depth percept. Results: We conducted a pilot study with 9 participants that validated our approach of using probes to assess the perceptual state of participants. Results from large-scale psiTurk sessions are forthcoming. Discussion: Using the depth-from-motion approach is justified in light of results from a study that obtained evidence for its validity in DII experiments with SZ patients and controls (Keane et al. 2013). Our crowd sourcing experiments can study useful unexplored correlations that require large numbers of participants.

Introduction: Recovering depth from stereo image pairs is known to have difficulties (Hoffman et al., 2008; Kim et al., 2012). The main issue: Poor matching of the distance between the two eyes' images and the placement of the eyes' prisms. We describe results with a hardware/software method enabling the precise adjustment of the horizontal position of images and the viewing prisms of the haploscope. Methods: A two-piece apparatus was added to prism-and-mirror haploscope that was initially designed with a fixed interpupillary distance (IPD) suitable most viewers. We added 1) a 3D-printed slider for the precise positioning of the prisms. 2) an eye piece with separate viewing ports to ensure a fixed distance between the eyes and the prisms.The IPD of each observer was used to adjust the distance between the centers of the haploscope prisms. Observers used a program developed in MATLAB to adjust the degree of horizontal displacement of left/right images on the screen.We compared results with the original haploscope and with the improved apparatus. Stimuli included random-dot stereograms (RDS), computer-generated objects and pictures of human faces. In the RDS condition, the task was to decide whether the presented shape was located in front or behind the background. In the 3D object and the face conditions, the task was to report whether the object/face was convex, concave or flat. Results: Data indicates significant improvement in accuracy with RDS images with the customized setup. Surprisingly, even after the improvement, not all viewers were virtually 100% correct in perceiving convex faces as convex, whereas they were all virtually 100% correct with physical masks (Keane et al. 2013). Conclusion: Setting up the haploscope to accommodate the viewer's unique IPD distance improves accuracy of depth perception. Despite the improvement, performance with stereoscopic images is still inferior to that with physical objects. Meeting abstract presented at VSS 2017

Introduction: Two depth-inversion (DI) illusions, where viewers perceive depth structure opposite to the stimulus's physical depth, are hollow masks and reverspectives [Wade & Hughes, 1999]. For faces, one explanation is that face-specific 3D stored knowledge and a general convexity bias overcome data-driven depth cues to produce DI. For reverspectives, stored general perspective rules (e.g., that retinal trapezoids are rectangles slanted in physical space with their long retinal edge closer to viewer) may account for the DI [Gregory, Phil. Trans. R. Soc. B, 2005]. We call such easily obtained DI illusions "Easillusions". Rationale for present study: We investigated whether humans can downplay stored knowledge and rules to obtain DI "hardillusions" for stimuli in which stored knowledge and rules oppose, rather than favor, DI [Papathomas et al. ECVP 2015]. Examples of such stimuli are normal, convex 3-D faces and "proper-perspectives", in which the retinal trapezoids are consistent with the depth of the physical surfaces. However, our 2015 study included only unpainted masks and fragments of reverse-perspectives. Methods: This study included a complete reverspective and realistically painted convex masks. Stimuli were both easillusions (hollow mask, reverspective) and hardillusions (convex mask, proper-perspective). Also, all stimuli were either realistically painted or unpainted. We assessed how long it took 16 subjects to obtain DI. Results: Painted reverspectives tended to produce DI faster than unpainted ones, whereas painted proper perspectives were much slower than unpainted ones. For faces, the difference for obtaining DI between painted and unpainted faces was much smaller both for the hollow and convex masks. The only stimuli that no subject was able to get DI were painted convex masks. Conclusions: Perspective painted cues played a much stronger role than facial painted cues, providing additional evidence that facial 3D geometry plays a larger role than scene 3D geometry. Meeting abstract presented at VSS 2017

Background: One of the best-known depth-inversion illusions (DII) that offers strong evidence for the influence of stored knowledge on the visual input [Bar et al. PNAS2006] is the hollow-face illusion [Gregory, "The intelligent eye", 1970; Georgeson, Perception 1979], where a concave face is misperceived as convex. A general explanation is that lifelong familiarity with convex faces overrides data-driven sensory signals. The convexity bias may also play a role in the illusion [Hill & Bruce, Perception 1994]. To isolate the role of the convexity bias we assessed the illusion strength using computer generated 3D convex and concave ovoid objects (results with similar computer generated face stimuli were reported last year [Farkas et al. VSS2015]). Methods: We modeled 14 ovoid "non-face" objects (7 convex, 7 concave), differing in shape, texture and depth structure. Three types of textures were mapped onto the objects, with random black-and-white square textels (texture elements): (1) "Concave texture": Textel size decreased linearly from periphery to center to provide perspective depth cue favoring concavity. (2) "Convex texture": Opposite size variation (increase from periphery to center), favoring convexity. (3) "Neutral texture": Uniform textel size. Each object oscillated around its vertical axis. Observers had to report whether the object was convex or concave. Results: The results indicate that DII strength depends on both structure and texture. The stimuli that produce the most ambiguous percept are the ones in which the textural depth cues compete against depth structure. Using this method we obtained a psychometric function for the DII tendency elicited by a set of virtual "non-face" objects. Conclusions - Discussion: The data show far weaker DII effects with ovoid stimuli as compared to the hollow-face illusion from our previous studies [Farkas et al. VSS2015]. These stimuli will be used to study differences in DII perception between schizophrenia patients and controls. Meeting abstract presented at VSS 2016

We introduce a novel procedure that uses dynamic 3-D computer graphics as a diagnostic tool for assessing disease severity in schizophrenia patients, based on their reduced influence of top-down cognitive processes in interpreting bottom-up sensory input. Our procedure uses the hollow-mask illusion, in which the concave side of the mask is misperceived as convex, because familiarity with convex faces dominates sensory cues signaling a concave mask. It is known that schizophrenia patients resist this illusion and their resistance increases with illness severity. Our method uses virtual masks rendered with two competing textures: (a) realistic features that enhance the illusion; (b) random-dot visual noise that reduces the illusion. We control the relative weights of the two textures to obtain psychometric functions for controls and patients and assess illness severity. The primary novelty is the use of a rotating mask that is easy to implement on a wide variety of portable devices and avoids the use of elaborate stereoscopic devices that have been used in the past. Thus our method, which can also be used to assess the efficacy of treatments, provides clinicians the advantage to bring the test to the patient’s own environment, instead of having to bring patients to the clinic.