Wide-field tracking of moving objects with a compact multi-object dispersed fixed-delay interferometer

2012 ◽  
Author(s):  
Jian Ge ◽  
Xiaoke Wan ◽  
Derek Myers ◽  
Scott Powell
Keyword(s):  
Moving Objects ◽  
Wide Field ◽  
Fixed Delay ◽  
Delay Interferometer

Orthopteran DCMD neuron: a reevaluation of responses to moving objects. II. Critical cues for detecting approaching objects

1992 ◽  
Vol 68 (5) ◽  
pp. 1667-1682 ◽  
Author(s):  
P. J. Simmons ◽  
F. C. Rind
Keyword(s):  
Moving Objects ◽  
Optic Lobe ◽  
Receptive Fields ◽  
Wide Field ◽  
Motion Detector ◽  
Dark Light ◽  
Subsequent Response ◽  
Object Movement ◽  
Line Movement ◽  
Important Stimulus

1. We examine the critical image cues that are used by the locust visual system for the descending contralateral motion detector (DCMD) neuron to distinguish approaching from receding objects. Images were controlled by computer and presented on an electrostatic monitor. 2. Changes in overall luminance elicited much smaller and briefer responses from the DCMD than objects that appeared to approach the eye. Although a decrease in overall luminance might boost the response to an approaching dark object, movement of edges of the image is more important. 3. When two pairs of lines, in a cross-hairs configuration, were moved apart and then together again, the DCMD showed no preference for divergence compared with convergence of edges. A directional response was obtained by either making the lines increase in extent during divergence and decrease in extent during convergence; or by continually increasing the velocity of line movement during divergence and decreasing velocity during convergence. 4. The DCMD consistently gave a larger response to growing than to shrinking solid rectangular images. An increase compared with a decrease in the extent of edge in an image is, therefore, an important cue for the directionality of the response. For single moving edges of fixed extent, the neuron gave the largest response to edges that subtended 15 degrees at the eye. 5. The DCMD was very sensitive to the amount by which an edge traveled between frames on the display screen, with the largest responses generated by 2.5 degrees of travel. This implies that the neurons in the optic lobe that drive this movement-detecting system have receptive fields of about the same extent as a single ommatidium. 6. For edges moving up to 250 degree/s, the excitation of the DCMD increases with velocity. The response to an edge moving at a constant velocity adapts rapidly, in a manner that depends on velocity. Movement over one part of the retina can adapt the subsequent response to movement over another part of the retina. 7. For the DCMD to track and continue to respond to the image of an approaching object, the edges of the image must continually increase in velocity. This is the second important stimulus cue. 8. Edges of opposite contrasts (light-dark compared with dark-light) are processed in separate pathways that inhibit each other. This would contribute to the reduction of responses to wide-field movements.

Orthopteran DCMD neuron: a reevaluation of responses to moving objects. I. Selective responses to approaching objects

1992 ◽  
Vol 68 (5) ◽  
pp. 1654-1666 ◽  
Author(s):  
F. C. Rind ◽  
P. J. Simmons
Keyword(s):  
Moving Objects ◽  
Temporal Frequency ◽  
Angular Acceleration ◽  
Spike Rate ◽  
Single Peak ◽  
Wide Field ◽  
Movement Detector ◽  
Star Wars ◽  
Wide Range ◽  
Real Objects

1. The "descending contralateral movement detector" (DCMD) neuron in the locust has been challenged with a variety of moving stimuli, including scenes from a film (Star Wars), moving disks, and images generated by computer. The neuron responds well to any rapid movement. For a dark object moving along a straight path at a uniform velocity, the DCMD gives the strongest response when the object travels directly toward the eye, and the weakest when the object travels away from the eye. Instead of expressing selectivity for movements of small rather than large objects, the DCMD responds preferentially to approaching objects. 2. The neuron shows a clear selectivity for approach over recession for a variety of sizes and velocities of movement both of real objects and in simulated movements. When a disk that subtends > or = 5 degrees at the eye approaches the eye, there are two peaks in spike rate: one immediately after the start of movement; and a second that builds up during the approach. When a disk recedes from the eye, there is a single peak in response as the movement starts. There is a good correlation between spike rate and angular acceleration of the edges of the image over the eye. 3. When an object approaches from a distance sufficient for it to subtend less than one interommatidial angle at the start of its approach, there is a single peak in response. The DCMD tracks the approach, and, if the object moves at 1 m/s or faster, the spike rate increases throughout the duration of object movement. The size of the response depends on the speed of approach. 4. It is unlikely that the DCMD encodes the time to collision accurately, because the response depends on the size as well as the velocity of an approaching object. 5. Wide-field movements suppress the response to an approaching object. The suppression varies with the temporal frequency of the background pattern. 6. Over a wide range of contrasts of object against background, the DCMD gives a stronger response to approaching than to receding objects. For low contrasts, the selectivity is greater for objects that are darker than the background than for objects that are lighter.

Design of a stable fixed delay interferometer prototype for the ET project

2004 ◽  
Author(s):  
Suvrath Mahadevan ◽  
Jian Ge ◽  
Curtis DeWitt ◽  
Julian C. van Eyken ◽  
Gerald Friedman
Keyword(s):  
Fixed Delay ◽  
Delay Interferometer

First Planet Confirmation with a Dispersed Fixed-Delay Interferometer

2003 ◽  
Vol 600 (1) ◽  
pp. L79-L82 ◽  
Author(s):  
J. C. van Eyken ◽  
J. Ge ◽  
S. Mahadevan ◽  
C. DeWitt
Keyword(s):  
Fixed Delay ◽  
Delay Interferometer

The human cortical areas V6 and V6A

2015 ◽  
Vol 32 ◽  
Author(s):  
SABRINA PITZALIS ◽  
PATRIZIA FATTORI ◽  
CLAUDIO GALLETTI
Keyword(s):  
Moving Objects ◽  
Visual Motion ◽  
Dynamic Condition ◽  
Arm Movement ◽  
Wide Field ◽  
Object Distance ◽  
Close Proximity ◽  
Retinotopic Organization ◽  
Evoked Activity ◽  
Self Motion

AbstractIn macaque, it has long been known since the late nineties that the medial parieto-occipital sulcus (POS) contains two regions, V6 and V6A, important for visual motion and action. While V6 is a retinotopically organized extrastriate area, V6A is a broadly retinotopically organized visuomotor area constituted by a ventral and dorsal subdivision (V6Av and V6Ad), both containing arm movement-related cells active during spatially directed reaching movements. In humans, these areas have been mapped only in recent years thanks to neuroimaging methods. In a series of brain mapping studies, by using a combination of functional magnetic resonance imaging methods such as wide-field retinotopy and task-evoked activity, we mapped human areas V6 (Pitzalis et al., 2006) and V6Av (Pitzalis et al., 2013d) retinotopically and defined human V6Ad functionally as a pointing-selective region situated anteriorly in the close proximity of V6Av (Tosoni et al., 2014). Like in macaque, human V6 is a motion area (e.g., Pitzalis et al., 2010, 2012, 2013a,b,c), while V6Av and V6Ad respond to pointing movements (Tosoni et al., 2014). The retinotopic organization (when present), anatomical position, neighbor relations, and functional properties of these three areas closely resemble those reported for macaque V6 (Galletti et al., 1996, 1999a), V6Av, and V6Ad (Galletti et al., 1999b; Gamberini et al., 2011). We suggest that information on objects in depth which are translating in space, because of the self-motion, is processed in V6 and conveyed to V6A for evaluating object distance in a dynamic condition such as that created by self-motion, so to orchestrate the eye and arm movements necessary to reach or avoid static and moving objects in the environment.

All-sky extrasolar planet searches with multi-object dispersed fixed-delay interferometer in optical and near IR

2004 ◽  
Author(s):  
Jian Ge ◽  
Suvrath Mahadevan ◽  
Julian C. van Eyken ◽  
Curtis DeWitt ◽  
Jerry Friedman ◽  
...  
Keyword(s):  
Extrasolar Planet ◽  
Near Ir ◽  
Fixed Delay ◽  
Delay Interferometer

Doppler high precision extra-solar planet surveys by a fixed delay interferometer

2003 ◽  
Author(s):  
Jian Ge ◽  
Julian C. van Eyken ◽  
Suvrath Mahadevan ◽  
Curtis DeWitt ◽  
Lawrence W. Ramsey ◽  
...  
Keyword(s):  
High Precision ◽  
Fixed Delay ◽  
Delay Interferometer

scholarly journals Measuring Stellar Radial Velocities with a Dispersed Fixed‐Delay Interferometer

2008 ◽  
Vol 678 (2) ◽  
pp. 1505-1510 ◽  
Author(s):  
Suvrath Mahadevan ◽  
Julian van Eyken ◽  
Jian Ge ◽  
Curtis DeWitt ◽  
Scott W. Fleming ◽  
...  
Keyword(s):  
Radial Velocities ◽  
Fixed Delay ◽  
Delay Interferometer
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