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Topic: Optic flow

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	Optic flow -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-11-02)
		Optic flow is the perceived visual (A change of position that does not entail a change of location) motion of objects as the observer moves relative to them.
		Since optic flow relies only on relative motion, it remains the same when you are moving and the world remains still, and when you are standing still but everything you can see is moving past you.
		It also appears to be used by certain insects, especially flying ones, where a large optic flow (indicating a quickly approaching obstacle) triggers muscles to move away.
	www.absoluteastronomy.com /encyclopedia/o/op/optic_flow.htm (270 words)

	Mobileye - General (Site not responding. Last check: 2007-11-02)
		Optic flow analysis allows to detect interesting regions in the scene even before the entire object is fully visible.
		Optic flow is used in several of Mobileye's applications at 2 levels: The first level is for tracking of targets.
		Optic flow is used to detect Blind Spot Detection for Lane Change Assist applications, where only a small portion of the vehicle appears in the image due to the close range.
	www.mobileye.com /opticFlow.shtml (246 words)

	Optic Flow
		Essentially, optic flow is the apparent visual motion that you experience as you move through the world.
		Also the optic flow will vary depending on the angle between your direction of travel and the direction of the object you are looking at.
		The optic flow travels from the forward to backward direction, and is generally faster on the left and right than in the front or back.
	www.centeye.com /pages/techres/opticflow.html (1406 words)

	Optic Flow Based Autonomous Tasks (Site not responding. Last check: 2007-11-02)
		Optic flow refers to the apparent movement of texture in the visual field relative to the insect’s velocity.
		Theoretically, optic flow is measured in rad/sec and is a function of the UAV’s forward velocity, V, angular velocity, w, distance D from an object, and the angle theta, between the MAV’s direction of travel and the object (see Figure 2).
		When the optic flow on the landing surface becomes larger than the desired optic flow, the error is negative and two conditions are possible.
	www.pages.drexel.edu /~weg22/opticFlow.html (1024 words)

	problem set #4
		Optic flow is an approximation of 3D motion that results from an image changing with time.
		Optic flow is an approximation to the motion field which is a velocity vector to each point in the image.
		Optical flow analysis would be performed on segments of video, this analysis would result in a vector field which would describe the movement of the human in the frame (since nothing else in the scene is moving).
	www.cc.gatech.edu /classes/AY2000/cs7495_fall/participants/maribeth/ps4 (677 words)

	Desislava Petkova
		Gibson, who first examined the role of optic flow in the visual control of locomotion during the 60s, did not offer empirical evidence for his hypothesis that optic flow is effective in giving rise to the perception of self movement.
		Optic flow is closely connected with the phenomenon of vection, the visually-induced illusion of movement when there is no actual displacement of the observer.
		On the other hand, expanding or contracting optic flow pattern is projected on the retina; therefore the visual system specifies that the observer is moving.
	www.mtholyoke.edu /~cfennema/ITR-Project/desislava-petkova/AchievingLinearVection.htm (2887 words)

	Optic flow: overview (Site not responding. Last check: 2007-11-02)
		Optic flow is a visual displacement flow field that can be used to explain changes in an image sequence.
		The optic flow equation is filtered with a set of filters of various spectral contents.
		This method also relies on the assumption that the optic flow has to be locally constant.
	www.cmap.polytechnique.fr /~bernard/OpticFlow/page1.html (433 words)

	JPT (Dec 2002): Downhole Fiber-Optic Multiphase Flowmeter (Site not responding. Last check: 2007-11-02)
		For flow regimes with appreciable slip, a more sophisticated slip model must be used to interpret the quantities measured by the meter and determine the flow rates of the individual phases.
		In the beam-pumped well, intermittent flow and relatively high acoustical- and structural-noise environments characteristic of beam pumps were not compatible with passive listening techniques used to monitor flow rates.
		In the ESP well, comparison of the flow rates and water cut measured by the fiber-optic flowmeter and the Coriolis meter were better than expected, plus or minus 2% for water cut and plus or minus 3% for total rate, and well within specifications.
	www.spe.org /spe/jpt/jsp/jptpapersynopsis/0,2439,1104_11038_1038813_1038955,00.html (1349 words)

	Jonathan Kelly - UCSB Psychology (Site not responding. Last check: 2007-11-02)
		According to some researchers, optic flow is the visual stimulus that people use to maintain an upright posture (and also the visual stimulus that causes the child in Figure 1 to fall down).
		Optic flow is defined as the changing angular positions of points in perspective image.
		We think that optic flow is just one type of stimulus to help perceive the changing 3D position of the environment, but not the only way.
	www.psych.ucsb.edu /~j_kelly/posture.html (650 words)

	Journal of Vision - Sensitivity to the gain of optic flow during walking, by Kearns, Durgin, & Warren (Site not responding. Last check: 2007-11-02)
		Optic flow is one source of visual information relied on for various locomotion tasks, including steering, obstacle avoidance, and path integration.
		On the other hand, if optic flow is a robust source of information about self-motion, one might expect sensitivity may be high.
		Results indicate high sensitivity (comparable to similar tasks) regardless of the baseline optic flow rate, indicating that flow sensitivity is relatively constant even in less familiar ranges.
	www.journalofvision.org /2/7/431 (348 words)

	Cogprints - Modulation of Responses to Optic Flow in Area 7a by Retinotopic and Oculomotor Cues in Monkey (Site not responding. Last check: 2007-11-02)
		Perception of two-and-three dimensional optic flow critically depends upon extrastriate cortices that are part of the "dorsal stream" for visual processing.
		The visual response to optic flow was modulated by the retinotopic stimulus position and by the eye position in the orbit.
		The spatial tuning for the eye position signals upon stationary stimuli and optic flow was not the same suggesting multiple anatomical sources of the signals.
	cogprints.org /7 (257 words)

	Optic Flow Based Autonomous Tasks (Site not responding. Last check: 2007-11-02)
		Optic flow can be used to autonomously land an aerial robot in closed quarters.
		Srinivasan observed that honeybees land by keeping the optic flow on the landing surface constant (v/d, where d is the altitude).
		After either control sequence has been implemented to force the optic flow back to the desired value, the throttle and elevator should be reset to its initial settings (i.e.
	www.pages.drexel.edu /~weg22/atol.html (392 words)

	[No title]
		I attempted to calculate the optic flow using the method where the optic flow is assumed to be constant over a given region of the image and the system of equations is optimized using least-squares.
		However, adding the 3 optic flow parameters would differentiate the branches from the sky since the branches would move in the video sequence relative to the sky.
		Using the optic flow data, Method 2 was able to cluster the pixels of tree more accurately because the flow of tree (which is close to the camera) is most likely very different from the lawn and the house.
	www.cs.wustl.edu /~rms2/cs519/project3/project3.htm (710 words)

	Optic Flow
		Optic flow can be defined as the motion of all the surface elements from the visual world.
		The interactive optic flow demo shows how all the tiny bits of texture that define the surfaces of the ground and objects on the world could be used to tell direction of locomotion.
		When optic flow information hits the back of the eye it is called retinal flow (RF).
	www.rdg.ac.uk /AcaDepts/sx/ARL/publish/research/optic_flow.htm (246 words)

	IU First To Isolate Method To Track Blood Flow To Optic Disc, Nerve
		INDIANAPOLIS-- Researchers at the Indiana University School of Medicine are the first to discover a consistent method to measure and quantify blood flow to the optic nerve and optic disc, information that may revolutionize the treatment of glaucoma.
		An infrared laser and dye are used to measure deeper into the eye, penetrating the choroid which is located behind the retina and optic nerve and a major site of blood flow to the eye.
		The tools used to measure ocular blood flow for glaucoma patients also may be applicable in the treatment of other eye diseases such as macular degeneration, and those caused by diabetes and AIDS, Dr. Harris said.
	www.medicine.indiana.edu /news_releases/archive_97/2glaucoma.htm (515 words)

	Optic flow analysis
		The resulting flow of activation f(x,y,t) (hereafter referred as the ``cortical flow'') is the superposition (interference) pattern of all the localized wavefronts.
		Each MST neuron is selective to an elementary flow component referred to the fixation point (i.e., the preferred center of motion of the cell is located on the fovea) and is characterized by a specific tuning to the mean speed of motion of optic flow stimuli.
		On the basis of the spatiotemporal representation of the optic flow (the cortical flow), and taking advantage of the geometrical properties of the log-polar mapping, the template vector matching operations can be reconducted to spatiotemporal filtering operators characterized by directionally-tuned kernels to detect translational motion of the cortical flow.
	www.pspc.dibe.unige.it /Demos/Flow.html (994 words)

	Alternative sensory representations of the visual world
		Optic flow has been used successfully to guide robots along hallways; the basic principle is that texture on the left and right walls will appear to move at the same speed only from a viewpoint that is moving directly down the center of the hallway.
		In our system, optic flow information is also critical in that it suggests to the user that motion has occurred, possibly necessitating a re-rendering of the scene for further exploration.
		The audio output from the program is silent when optic flow is below a threshold, but increases in volume as optic flow increases in the scene, and pans from left to right with the location of maximum optic flow.
	techhouse.brown.edu /~neel/haptic.scene.representation (1727 words)

	[No title] (Site not responding. Last check: 2007-11-02)
		This optic flow vector is the direction and magnitude one pixel needs to move to match the other image.
		During the next iteration, the frame is warped by the computed vector and then the optic flow is found for this frame and added to he previous vector.
		For the non-zero portion of the optic flow field, limbs and other body parts can be identified since the optic flow field for a give body part should be fairly constant or a recognizable pattern for the case of rotations.
	www.cc.gatech.edu /classes/AY2000/cs7495_fall/participants/jammin/ps4 (562 words)

	Optic Flow (Site not responding. Last check: 2007-11-02)
		The flow estimate is obtained with a multi-scale coarse-to-fine algorithm based on a gradient approach described by [
		Optic-flow is sensitive to the motion of image regions and the direction in which different facial features move, but it is also sensitive to the positions of the feature points.
		We computed the dense optic flow of the images extracted from the normalized face image.
	vismod.media.mit.edu /tech-reports/TR-517/node6.html (145 words)

	CELLS IN MACAQUE AREA 7A ARE SENSITIVE TO RETINAL DISPARITIES EMBEDDED IN OPTIC FLOW STIMULI. Raymond E. Phinney & ... (Site not responding. Last check: 2007-11-02)
		To assess the contribution of retinal disparity in optic flow processing, neurons in area 7a of behaving macaques (3 hemispheres in 2 males) were tested with a variety of optic flows and static dot fields, with and without retinal disparity.
		Optic flows used were radial expansion, radial compression, clockwise and counter- clockwise rotation, stationary flickering dot fields, translations in one of 8 directions 45 degrees apart, and structure-from-motion spheres rotating either horizontally or vertically.
		This may indicate that disparity processing is motion-gated in area 7a, so that retinal disparity has only a modulatory influence on optic flow processing in area 7a.
	www.cmbn.rutgers.edu /faculty/siegeldocs/sfn98disparity.htm (404 words)

	Optokinetic Eye Movements Elicited by Radial Optic Flow in the Macaque Monkey -- Lappe et al. 79 (3): 1461 -- Journal ...
		Besides this use of optic flow for the guidance of self-motion, however, a further concern is its implication for visual stability
		During the visual scanning of a radial optic flow stimulus, the visual motion pattern arriving on the retina depends on the
		Optic flow stimuli were generated by a graphics work station (Silicon Graphics Indigo 2).
	jn.physiology.org /cgi/content/full/79/3/1461 (9548 words)

	Biomimetic Flight Control
		By the mid-1990's, researchers were able to integrate optic flow algorithms into robotic platforms and use them to perform simple navigation tasks in real time.
		It was only recently that optic flow sensing was successfully integrated into small aircraft and used to provide the aircraft with some degree of autonomy.
		The goal of this project is to demonstrate that our optic flow sensors can be used by an autopilot to fly a small RC aircraft through a real-world environment.
	www.centeye.com /pages/techres/flightcontrol.html (1641 words)

	Bias in Optic Flow (Site not responding. Last check: 2007-11-02)
		The first step of many visual algorithms is the computation of "optic flow" -- how points move from one frame to the next.
		A statistical analysis of a common method of optic flow computation shows that in the presence of noise in the image, the computed optic flow has a statistical bias; furthermore, this bias is dependent upon the exact distribution of the errors in the image measurements.
		These measurements may also have errors, but the measurements are combined directly with reference to the three-dimensional structure of the world and three dimensional camera motion, and do not give errors involved with consistent bias of image motion.
	www.cfar.umd.edu /users/pless/image_motion.html (255 words)

	The Gradient-Based Approach (Site not responding. Last check: 2007-11-02)
		If the image motion is not known in advance to be restricted to a small range of possible values then a multi-scale analysis must be applied (coarse to fine) so that the scale of the smoothing prior to derivative estimation is appropriate to the scale of the motion.
		Here Horn and Schunk use spatiotemporal derivatives of the evolving image brightness function to give a single equation which partially determines the optic flow; the assumption is made that the brightness of any part of the imaged world changes very slowly, so that the total derivative of the brightness is zero.
		Here the optic flow is only smoothed in the direction perpendicular to the image brightness gradient, so that discontinuity boundaries are much better preserved.
	www.fmrib.ox.ac.uk /~steve/review/review/node3.html (784 words)

	2004; The Role of Central and Peripheral Optic Flow in the Control of Upright Posture Within a Mixed-Frequency Visual ...
		The goal of this study was to investigate the influence of optic flow on upright posture when patterns in the central and peripheral fields of view (FOVs) move simultaneously but at different sinusoidal frequencies.
		There were two visual combinations: in one, the central optic flow stimulus moved at 0.1 Hz while the peripheral optic flow moved at 0.25 Hz; in the other, the frequencies were reversed.
		There were more significant responses to the peripheral optic flow stimulus (58/80) than there were to the central optic flow (16/80).
	www.aro.org /archives/2004/2004_302.html (339 words)

	Schmitt Program - 2002 Colloquium Professors (Site not responding. Last check: 2007-11-02)
		MST cells have large receptive fields and are responsive to full field optic flow stimuli that an observer sees as he moves through the environment.
		I have shown that individual MST cells are modulated by the behavioral relevance of optic flow.
		In the flow-irrelevant task, the monkey had to remember the location or identity of a cue that was presented before the optic flow.
	www.urmc.rochester.edu /smd/NAnat/Schmitt/colloquium-professors/2002.cfm (598 words)

	Speed Selectivity for Optic Flow in Area 7a of the Behaving Macaque -- Phinney and Siegel 10 (4): 413 -- Cerebral Cortex (Site not responding. Last check: 2007-11-02)
		The response of four cells to four optic flows at eight speeds are graphed, one cell per line.
		Duffy CJ, Wurtz RH (1991) Sensitivity of MST neurons to optic flow stimuli.
		Phinney RE, Siegel RM (1997) Speed selectivity for optic flow stimuli in area 7a of the behaving macaque: tuning functions, preferred speeds, bandwidths.
	cercor.oxfordjournals.org /cgi/content/full/10/4/413 (6436 words)

	Tutorial 2 : The instantaneous optic flow field
		The depth Z of course depends on the scene being animated, and in particular the optic flow field in a region depends on the surface structure of the object visible in that region.
		In particular the optic flow field in a region depends on the surface structure of the object visible in that region.
		We have also created a new basis for the first-order optic flow terms, aiming for flows which more closely represent real optic flow fields induced by a moving object.
	cw.scouting.org.za /ian/research/tut2 (699 words)

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