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Constant magnification optical tracking system
A constant magnification optical tracking system for continuously tracking of a moving object is described. In the tracking system, a traveling objective lens maintains a fixed relationship with an object to be optically tracked. The objective lens was chosen to provide a collimated light beam oriented in the direction of travel of the moving object. A reflective surface is attached to the traveling objective lens for reflecting an image of the moving object. The object to be tracked is a free-falling object which is located at the focal point of the objective lens for at least a portion of its free-fall path. A motor and control means is provided for mantaining the traveling objective lens in a fixed relationship relative to the free-falling object, thereby keeping the free-falling object at the focal point and centered on the axis of the traveling objective lens throughout its entire free-fall path.
MOTS - THE MINITRACK OPTICAL TRACKING SYSTEM
Description of the minitrack optical tracking system used for satellite tracking
Improved electro-optical tracking system
Electro-optical tracking system employs a laser beam illuminating source, an electronic laser beam deflector, and an image dissector photomultiplier. An electronic scanning transmitter and receiver follows rapid movements or accelerations of the target.
Sci—Sat AM: Stereo — 09: Accuracy of Liver Cancer Treatment on Cyberknife® with Synchrony™ Optical Tracking Throughout the Respiratory Cycle
The Cyberknife® robotic stereotactic body radiation therapy system is well-suited for treating liver lesions over the respiratory cycle as it includes room-mounted orthogonal x-ray tracking of internal fiducial markers and optical tracking of external markers. The Synchrony™ software generates a model of internal target positions during patient respiration and correlates it to the external optical tracking system for real-time optical-based position corrections of the linear accelerator during beam delivery. Although clinical studies have provided preliminary outcomes for liver lesions treated with the Cyberknife system, to date, there is little data demonstrating the ability of the Synchrony software to track targets in the liver, which deforms throughout the respiratory cycle. In this study, we investigated the respiratory motion model performance for predicting tumour motion. We conducted a retrospective analysis of fifteen liver cancer patients treated on the Cyberknife using the Synchrony optical tracking system. We analyzed Cyberknife tracking information stored in the log files to extract the left-right (LR), anterior-posterior (AP) and superior-inferior (SI) correlation errors between the model-predicted position and the internal fiducial centroid position determined by x-ray imaging. Only translational tracking and corrections were applied during treatment. Overall, the correlation errors were greatest in the SI direction. We calculated radial correlation errors, and determined that the 95{sup th}, 98{sup th} and 99{sup th} percentile errors were 3.4 mm, 4.4 mm and 5.1 mm, respectively. Based on translational correlation tracking errors we expect the clinical target volume will be within 3.4 mm of the planning target volume for 95 % of beam delivery time.
Design problems in a control system used for precise optical tracking of satellites and stars
Design problems and solutions in control system for precise optical tracking of stars and satellites
Utilization of optical tracking to validate a software-driven isocentric approach to robotic couch movements for proton radiotherapy
Purpose: An optical tracking and positioning system (OTPS) was developed to validate the software-driven isocentric (SDI) approach to control the six-degrees-of-freedom movement of a robotic couch. Methods: The SDI approach to movements rotating around a predefined isocenter, referred to as a GeoIso, instead of a mechanical pivot point was developed by the robot automation industry. With robotic couch-sag corrections for weight load in a traditional SDI approach, movements could be accurately executed for a GeoIso located within a 500 mm cubic volume on the couch for treatments. The accuracy of SDI movement was investigated using the OTPS. The GeoIso was assumed to align with the proton beam isocenter (RadIso) for gantry at the reference angle. However, the misalignment between GeoIso and RadIso was quantitatively investigated by measuring the displacements at various couch angles for a target placed at the RadIso at an initial couch angle. When circular target displacements occur on a plane, a relative isocenter shift (RIS) correction could be applied in the SDI movement to minimize target displacements. Target displacements at a fixed gantry angle without and with RIS correction were measured for 12 robotic couches. Target displacements for various gantry angles were performed on three couches in gantry rooms to study the gantry-induced RadIso shift. The RIS correction can also be applied for the RadIso shift. A new SDI approach incorporating the RIS correction with the couch sag is described in this study. In parallel, the accuracy of SDI translation movements for various weight loads of patients on the couch was investigated during positioning of patients for proton prostate treatments. Results: For a fixed gantry angle, measured target displacements without RIS correction for couch rotations in the horizontal plane varied from 4 to 20 mm. However, measured displacements perpendicular to couch rotation plane were about 2 mm for all couches. Extracted misalignments of GeoIso and RadIso in the horizontal plane were about 10 mm for one couch and within 3 mm for the rest of couches. After applying the RIS correction, the residual target displacements for couch rotations were within 0.5 mm to RadIso for all couches. For various gantry angles, measured target location for each angle was within 0.5 mm to its excepted location by the preset RadIso shift. Measured target displacements for ±30° of couch rotations were within 0.5 mm for gantry angles at 0° and 180°. Overall, nearly 85% of couch movements were within 0.5 mm in the horizontal plane and 0.7 mm vector distance from required displacements. Conclusions: The authors present an optical tracking methodology to quantify for software-driven isocentric movements of robotic couches. By applying proper RIS correction for misaligned GeoIso and RadIso for each couch, and the RadIso shifts for a moving gantry, residual target displacements for isocentric couch movements around the actual RadIso can be reduced to submillimeter tolerance.
Resolution of a target-tracking optical novelty filter
The resolution of a target-tracking optical novelty filter is discussed in terms of the response time of the nonlinear medium, the speed of the target, and the resolution of the input device. Optical novelty filters using a faster nonlinear medium may have a higher output resolution. This is particularly true in the case of tracking high-speed targets. The potential of implementing high-resolution optical novelty filters using photorefractive GaAs is investigated experimentally.
Optical tracking of lunar spacecraft
Specular reflection measurements for optical tracking of lunar spacecraft
Monitoring ABC-assisted deep inspiration breath hold for left-sided breast radiotherapy with an optical tracking system
Purpose: Recent knowledge on the effects of cardiac toxicity warrants greater precision for left-sided breast radiotherapy. Different breath-hold (BH) maneuvers (abdominal vs thoracic breathing) can lead to chest wall positional variations, even though the patient’s tidal volume remains consistent. This study aims to investigate the feasibility of using optical tracking for real-time quality control of active breathing coordinator (ABC)-assisted deep inspiration BH (DIBH). Methods: An in-house optical tracking system (OTS) was used to monitor ABC-assisted DIBH. The stability and localization accuracy of the OTS were assessed with a ball-bearing phantom. Seven patients with left-sided breast cancer were included. A free-breathing (FB) computed tomography (CT) scan and an ABC-assisted BH CT scan were acquired for each patient. The OTS tracked an infrared (IR) marker affixed over the patient’s xiphoid process to measure the positional variation of each individual BH. Using the BH within which the CT scan was performed as the reference, the authors quantified intra- and interfraction BH variations for each patient. To estimate the dosimetric impact of BH variations, the authors studied the positional correlation between the marker and the left breast using the FB CT and BH CT scans. The positional variations of 860 BHs as measured by the OTS were retrospectively incorporated into the original treatment plans to evaluate their dosimetric impact on breast and cardiac organs [heart and left anterior descending (LAD) artery]. Results: The stability and localization accuracy of the OTS was within 0.2 mm along each direction. The mean intrafraction variation among treatment BHs was less than 2.8 mm in all directions. Up to 12.6 mm anteroposterior undershoot, where the patient’s chest wall displacement of a BH is less than that of a reference BH, was observed with averages of 4.4, 3.6, and 0.1 mm in the anteroposterior, craniocaudal, and mediolateral directions, respectively. A high positional correlation between the marker and the breast was found in the anteroposterior and craniocaudal directions with respective Pearson correlation values of 0.95 and 0.93, but no mediolateral correlation was found. Dosimetric impact of BH variations on breast coverage was negligible. However, the mean heart dose, mean LAD dose, and max LAD dose were estimated to increase from 1.4/7.4/18.6 Gy (planned) to 2.1/15.7/31.0 Gy (delivered), respectively. Conclusions: In ABC-assisted DIBH, large positional variation can occur in some patients, due to their different BH maneuvers. The authors’ study has shown that OTS can be a valuable tool for real-time quality control of ABC-assisted DIBH.
Adaptive compensation for an optical tracking telescope
The application of model referenced adaptive control theory to an optical tracking telescope is discussed. The capability of the adaptive technique to compensate for mount irregularities such as inertial variations and bearing friction is demonstrated via field test results on a large tracking telescope. Results are presented which show a 6 to 1 improvement in tracking accuracy for a worst-case satellite trajectory.
Intercomparison of the minitrack and optical tracking networks using GEOS-1 long arc orbital solutions, part 1
Minitrack and optical tracking networks compared using Explorer 29 /GEOS 1/ long arc orbital solutions
Visibility and optical tracking studies for the concentric flight plan of lunar orbit rendezvous
Visibility and optical tracking studies for concentric flight plan of lunar orbit rendezvous
Laboratory test results of the high speed optical tracking system for the Spaceborne Geodynamic Ranging System
The high speed, high resolution optical tracking system for the Spaceborne Geodynamic Ranging System employs a two-axis gimbaled pointing device that can operate from a Space Shuttle platform and can track multiple retroreflector ground targets with arcsec accuracy. Laboratory tests of the stepping characteristics of the pointing system for various step sizes and directions has shown arcsec repeatability with little wasted motion, overshoot, or ringing. The worst rms tracking jitter was 1 and 2 arcsec in the roll and pitch axes, respectively, at the maximum tracking rate of 2 deg/sec.
Intercomparison of the Minitrack and optical tracking networks using GEOS 1 long-arc orbital solutions
Intercomparison of Minitrack and optical tracking networks using GEOS 1 long arc orbital solutions
Analysis of atmospherically induced errors in an optical tracking system Quarterly report, 14 Oct. 1968 - 14 Jan. 1969
Atmospherically induced errors induced in optical tracking system
Optical tracking telescope compensation
In order to minimize the effects of parameter variations in the dynamics of an optical tracking telescope, a model referenced parameter adaptive control system is described that - in conjunction with more traditional forms of compensation - achieves a reduction of rms pointing error by more than a factor of six. The adaptive compensation system utilizes open loop compensation, closed loop compensation, and model reference compensation to provide the precise input to force telescope axis velocity to follow the ideal velocity.
The evolution of electronic tracking, optical, telemetry, and command systems at the Kennedy Space Center
A history is presented of the major electronic tracking, optical, telemetry, and command systems used at ETR in support of Apollo-Saturn and its forerunner vehicles launched under the jurisdiction of the Kennedy Space Center and its forerunner organizations.