scholarly journals Angular responsivity of ground and space-based direct solar irradiance radiometers

2022 ◽  
Vol 2149 (1) ◽  
pp. 012001
Author(s):  
Gregor Hülsen ◽  
Julian Gröbner ◽  
Daniel Pfiffner ◽  
Manfred Gyo ◽  
Natalia Kouremeti ◽  
...  

Abstract The angular response setup of PMOD/WRC was modified to facilitate measurements of the narrow field of view of radiometers for direct solar irradiance. First, The pointing of the JTSIM-DARA radiometer was measured four times during its construction in the optic laboratory of PMOD/WRC. The final offset of the pointing before shipping relative to the optical axis, defined by a removable alignment cube, is 1.07° / 0.67° (β/γ-axis) for the four-quadrant sensor and 0.095°/-0.017° for the radiometer cavity A. Next to JTSIM-DARA the DARA for the occulter of the satellite Proba-3 was characterised at PMOD/WRC. First tests of the pointing have been carried out and the final pointing characterization will be carried out in summer 2021. Finally, the angular response setup was also used the angular responsivity of solar direct irradiance filter radiometers. The first test was carried out using Precision Filter Radiometer (PFR) F-064.

Sensors ◽  
2020 ◽  
Vol 20 (9) ◽  
pp. 2697
Author(s):  
Carl Leake ◽  
David Arnas ◽  
Daniele Mortari

This study introduces a new “Non-Dimensional” star identification algorithm to reliably identify the stars observed by a wide field-of-view star tracker when the focal length and optical axis offset values are known with poor accuracy. This algorithm is particularly suited to complement nominal lost-in-space algorithms, which may identify stars incorrectly when the focal length and/or optical axis offset deviate from their nominal operational ranges. These deviations may be caused, for example, by launch vibrations or thermal variations in orbit. The algorithm performance is compared in terms of accuracy, speed, and robustness to the Pyramid algorithm. These comparisons highlight the clear advantages that a combined approach of these methodologies provides.


Author(s):  
Matthew J. Kundrat ◽  
Per F. Reinhall ◽  
Christopher M. Brown ◽  
Eric J. Seibel

In order to develop a one-millimeter outside diameter endoscope we have moved away from using a bundle of optical fibers that are an integral part of current endoscopes. To achieve the field of view and the resolution requirements in spite of the small diameter we are using a single optical fiber that acts as a scanning source. Photo detectors positioned along the side of the scanning fiber detect the backscattered light and software then reconstructs the image on a monitor. The single optical fiber moves in a spiral scan pattern that is produced using a four quadrant piezoelectric tube as the actuator. The optical fiber is fed through the center of the piezoelectric tube and glued into place.


2011 ◽  
Vol 403-408 ◽  
pp. 2919-2922
Author(s):  
Ying Chao Li ◽  
Yuan Jian Zhang

A dual field of view and zoom infrared optical system with uncooled infrared staring focal plane arrays is designed in this paper. The operating waveband of the system is 8~12μm, and zoom radio is 3×. The optical configuration is based on the axial motion of a lens group along the optical axis. Optical material used infrared monocrystalline silicon、Znse, In order to achieve high performance、high image quality, used two even aspheric surfaces in this system. The advantages of this system are the high imaging quality、small volume、light weight.


Author(s):  
Ya.V. Shkorbotun

One of the predetermining factors to perform minimally invasive rhinosurgery successfully is the searching for optimal surgical access areas, the choice of which at present mostly depends on the visualization capabilities of endoscopic devices. The angular vision is one of the important factors for planning and performing endonasal interventions on the anterior maxillary sinus. A large viewing angle allows surgeons to expand the potentials of minimally invasive access, reduce the need to replace endoscopes with different angles during the intervention and improve the quality of the surgical procedure. The purpose of this study was to improve the method for selecting surgical access to the maxillary sinus, taking into the optical axis and the actual size of the field of view provided by the endoscope. The simulation of the process of selecting the optimal option for access to the maxillary sinus on the basis of our own method of predicting the visualization of the lumen in the sinus was performed. To determine the actual viewing angle of the endoscope, we compared the application of the standard methodology and the approach we elaborated. 3 endoscopes with a 70° optical axis orientation were examined; the studies were performed three times. We found that the results of determining the boundaries of the field of view according to our technique and to the method of Wang Q. et al. (2017) did not differ significantly, that indicates the comparable accuracy of both methods. With the declared identical characteristics of all three endoscopes, we revealed the magnitude of the field of view differed quite significantly (by a maximum of 8.7°). Moreover, the value of the viewing angle in all samples of endoscopes tested was greater than that provided by the manufacturer for standard endoscopes (60 °). The average duration of measuring the magnitude of the field of view of the endoscope by the method we proposed took 25.3 ± 3.2 s that was significantly faster than by the method of Wang Q. et al. (2017), 83.7 ± 2.0 s P≤0.05). We should also stress on the greater convenience of carrying out examinations according to our method. When assessing the potential of the maxillary sinus visualization, it is necessary to take into account not only the individual anatomical features of a patient, but also the actual optical characteristics of endoscopes. The device we designed for determining the boundaries of the field of view of endoscopes is easy to manufacture, requires less time for testing and enables to determine the actual viewing angles of the endoscope quicker and more effectively. Actual optical characteristics of endoscopes may differ from the standards.


2011 ◽  
Vol 403-408 ◽  
pp. 4388-4397
Author(s):  
Xiao Hu ◽  
Jiu Li ◽  
Jin Feng Liu ◽  
Zi Qiang Huang

A novel double liquid lens based on Electrowetting-On-Dielectric (EWOD) is presented and analyzed. The special construction is that the lens was divided into four quadrants. The particular fabrication process is presented to achieve the structure. It was proved that the lens not only expressed the electric zoom character but also shifted focal point away from optical axis. It also achieved an infinite focal length under zero electric field. The paper presented the relationship between the focus length and applied voltage, also gave the association between focus length and the applied voltage from 0V to 80V. We analyzed how the optical axis shifted according to the voltage difference between quadrants, furthermore, explained the new function that the focus object was away from center of lens.


2020 ◽  
pp. 1-13
Author(s):  
Chunxi Zhang ◽  
Yanqiang Yang ◽  
Hao Zhang ◽  
Xiaowen Cai

The star sensor field of view varies from several arc-minutes to 20 degrees, which directly determines the star vector orientation in the field of view (FOV). Although the relationship between star vector orientation in the FOV and attitude accuracy has been revealed, the influence mechanism of star vector orientation on the integrated navigation performance of a stellar inertial navigation system has not been analysed. In order to improve the integrated accuracy, the main errors such as star sensor installation error, gyro error and initial platform angle error should be estimated online. It is significant to study the influence mechanism of star vector orientation on estimation of the above errors. In this paper, the star sensor sensitivity and the geometry factor are defined to feature the difference between the optical axis direction and the non-optical axis direction. The formulised mechanism and quantification results between star vector orientation and integration attitude and error estimation accuracy are clearly given. Simulation and ground testing were conducted and it was found that the larger the star vector orientation along the optical axis, the better the error estimation accuracy. In contrast, the attitude accuracy is weakly sensitive to the orientation of the star vector in conditions of appropriate posture adjustment and star observation scheme. This conclusion can offer universal guidance for the design and evaluation of stellar inertial navigation systems with narrow field of view or large field of view star sensors.


2006 ◽  
Vol 45 (18) ◽  
pp. 4383 ◽  
Author(s):  
Boyan Petkov ◽  
Vito Vitale ◽  
Claudio Tomasi ◽  
Ubaldo Bonafé ◽  
Salvatore Scaglione ◽  
...  

2021 ◽  
Author(s):  
Duo Wu ◽  
Ping Zhu ◽  
Wei Fang ◽  
Xin Ye ◽  
Kai Wang ◽  
...  

<p>A space based relative radiometer has been developed and applied to the PICARD mission. It has successfully measured 37 months solar radiation, terrestrial outgoing radiation, and a comparable interannual variation in Earth Radiation Budget (ERB) is inferred from those measurements [1]. However, since the BOS (Bolometric Oscillation Sensor [2]) relative radiometer is originally designed to measure the solar irradiance with 10 seconds high cadence comparing to the absolute radiometer. The high dynamic range of BOS limits its performance to track the Earth’s outgoing radiation in terms of instantaneous field-of-view (iFOV) and the absolute radiation level. Two relative radiometers (RR) will be developed for JTSIM/FY-3F. One is the solar channel relative radiometer aimed to measure the solar irradiance side by side with the cavity solar irradiance absolute radiometer (SIAR). The second RR is acting as a non-scanner instrument to measure the Earth’s outgoing radiation. Comparing to the design of PICRD-BOS. Each RR has included an aperture, for the solar channel it limits its Unobstructed Field of View (UFOV) to about 1.5 degree and for the Earth channel to about 110 degrees, respectively. We also test the possibility to use the Carbon Nanotube coating on the main detector. In this presentation, the design of the earth channel relative radiometer (ERR) will be introduced, including the aperture design, dynamic range and the active temperature control system. The preliminary laboratory test result of the ERR will be discussed in the end.</p><p>[1] <strong>P. Zhu,</strong> M. Wild, M. van Ruymbeke, G. Thuillier, M. Meftah, and Ö. Karatekin. Interannual variation of global net radiation flux as measured from space. J. Geophys. Res. doi:10.1002/2015JD024112, 121:6877–6891, 2016.</p><p>[2] <strong>P. Zhu,</strong> M.van Ruymbeke, Ö. Karatekin, J.-P.Noël, G. Thuillier, S. Dewitte, A. Chevalier, C. Conscience, E. Janssen, M. Meftah, and A. Irbah. A high dynamic radiation measurement instrument: the bolometric oscillation sensor (bos). Geosci. Instrum. Method. Data Syst., 4,89-98,:doi:10.5194/gi–4–89–2015, 2015.</p><p><strong>Acknowledgement</strong>: this work is partly supported by the National Natural Science Foundation of China No. 41974207 and CSC Scholarship No.202004910181</p><p> </p>


Sensors ◽  
2021 ◽  
Vol 21 (22) ◽  
pp. 7544
Author(s):  
Mirco Bartolomei ◽  
Lorenzo Olivieri ◽  
Carlo Bettanini ◽  
Stefano Cavazzani ◽  
Pietro Fiorentin

Sky Quality Meter (SQM) is a commercial instrument based on photometers widely used by amateur astronomers for skyglow measurement from the ground. In the framework of the MINLU project, two SQM-LE units were integrated in an autonomous sensor suite realized and tested at University of Padova for monitoring light pollution from drones or sounding balloons. During the ground tests campaign before airborne measurement, the performance of both SQM units was verified in laboratory using controlled light sources as a reference input; the results showed that both units presented an angular response deviating consistently from the expected performance and that the sensors’ field of view was larger than the one declared in the manufacturer’s datasheet. This aspect in particular would affect direct skyglow measurements during flight as light sources close to the boundaries of the field of view would not be attenuated but instead detected by the sensors. As a direct consequence, the measurement of low-intensity skyglows at stratospheric altitudes could be affected by high-intensity punctual sources acting as lateral disturbances. A dedicated test campaign was therefore conceived and realized to investigate SQM unit response to light sources in the field of view and identify the true angular response curve; the setup consisted in a controlled rotatory stage moving the unit in front of a fixed diffusive light source. Different test conditions were used to validate the experimental procedure, demonstrating the repeatability of the measurements. This paper presents the experimental campaign and the resulting SQM angular response curve; results indicate for both SQMs a larger than expected field of view and the presence of a double peak in the angular response, which is likely related to a non-perfect alignment of SQMs collimation optics. Furthermore, the wider resulting curves suggest that the contribution of lateral sources is more prominent with respect to the response predicted by the manufacturer. For this reason, the utilization of baffles to restrict SQMs field of view is analyzed to minimize the disturbance of lateral light sources and two different geometries are presented.


2013 ◽  
Vol 336-338 ◽  
pp. 1053-1058
Author(s):  
Bo Wang ◽  
Xing Guang Qi

For a monocular camera-based mobile robot system,we propose the active visual method for robot localization,based on the double freedom pan-tilt.First,the kinematic model of the mobile robot system of monocular vision is given.Secondly,by controlling the pitch and yaw angles of pan-tilt,the camera optical axis always points to the target geometry center in order to solve the field of view problem.Coordinate system relative pose solution method which based on dual quaternion avoids calculating the singularity and improves the positioning accuracy of mobile robots.Finally,according to pan-tilts feedback angles,extrinsic parameters of the camera,the pose and the position of the camera,the position vector and pose vector of the mobile robot are obtained.


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