We briefly report on the development of a 50 mm balloon-borne coronagraph and its recent ground experiment results made at the high altitude (4800 m above the sea level) site of Mt. Wumingshan in Daocheng, Sichuan of China. The main scientific purpose for developing this coronagraph is to investigate the morphology and dynamics of low-layer coronal structures before and during solar eruptions by observing at a float altitude of about 30 km from 1.08 Rsun to 1.5 Rsun at white light wavelength (centered at 550.0 nm, bandwidth 5 nm). The instrument is an internally occulted Lyot coronagraph developed by Yunnan Observatories in collaboration with Shangdong University (in Weihai) and Changchun Institute of Optics, Fine Mechanics and Physics. The coronagraph was designed with scattered light intensity level of better than 1×10-5 Isunin the inner field of view. A filter wheel system with linear polarizers and an sCMOS camera provided polarization and total brightness images of size 2048 x 2048 pixels. The first successful results were taken on February 27, 2021 in the Daocheng site. This coronagraph experiment obtained coronal images only showing obvious coronal structures very near limb. Furthermore, during the end of March and early April, after improving the polarizer filter system, higher-quality coronal images with pB coronal structures appeared in the full field of view were obtained in our ground-based experiments. Comparison between our results and the other coronal data in the world are discussed. The success of the 50 mm coronagraph in ground experiments is a milestone for us to develop the next-generation large-aperture coronagraph, as well as for future near space projects.
Near space usually refers to the earth space with a height of about 20-100 km. It is a highly interdisciplinary field involving atmospheric physics, space physics, plasma physics, photochemistry, solar and geosciences, Geosciences and life sciences. The development and utilization of near space is far less than that of traditional airspace and satellite orbital space. Near space usually corresponds to areas where traditional airplanes are difficult to fly and satellites are not easy to detect. Compared with the middle and lower atmosphere and higher ionosphere and outer space, there has been a lack of systematic and efficient observers in the near space for a long time. Objectively, near space has become a weak point of human's understanding of the whole earth's space.
With the development of high-speed digital system, high-speed serial data transmission is widely used and the FPGA containing high-speed serial transceiver is also widely used. The high-speed serial interface of Xilinx's FPGA includes GTP, GTX, GTH and other high-speed transceivers with different transmission rate. The physical transmission speed of these transceivers can reach tens of Gbps. These low-level high-speed transceivers can support a variety of top-level transmission protocols, such as SRIO, PCIE, SATA, optical fiber and so on. Among these top-level transmission protocols, optical fiber transmission has the longest transmission distance and is widely used in various scenarios. Optical fiber transmission has three advantages. Firstly, its transmission capacity is very large and it can support ultralong distance transmission, one line optical fiber transmission rate can easily reach several Gbps. Secondly, optical fiber communication has strong anti-electromagnetic interference characteristics, which can ensure the quality of data transmission. Thirdly, optical fiber transmission uses light wave for data transmission and the light wave transmitted in the optical fiber cannot run out, so there is no radiation and it is difficult to eavesdrop.
Limited by the volume and power of lasers, nanosecond short-pulse lasers are commonly used in laser communication, laser range finder, laser guidance, pulse laser Radar, high-speed photography and 3D imaging systems. Therefore, as one of the key laser indicators, the nanosecond short-pulse laser peak power measurement is essential. In this paper, a new method for measuring peak power of nanosecond short-pulse laser is proposed. The peak power can be measured directly by extending the pulse width without using super high speed ADC chip. Research is made from two parts: detector and control host. As for the detector, a new attenuation unit is designed, which can well suppress the peak power decrease caused by the traditional detector broadening the short pulse and realize the original waveform output (non-distortion). In the control host, a new pulse broadening circuit is proposed, which realized the peak signal acquisition of 20ns pulse width (5ns rising edge) laser without the use of ultra-high speed ADC acquisition chip. The measurement system can achieve technical indicators as follows: the measurable pulse width is 20ns~150us, Pulse rising edge is 5ns~10us, the repetition frequency is 100Hz~500kHz, and the measurement range of laser peak power is 1W~500W.
With the rapid development of image sensor research, mobile industry processor interface (MIPI) was used to meet the massive data throughput capacity since the higher frame rate and more pixels on the smaller sensors. This paper realized the image processing of MIPI based on FPGA. The image sensor used here is OS08A10, which has 8Mega Pixels and contains up to 4-lane MIPI serial output interface. The resolution of image sensor is 3840*2160 at frame rate of 25fps and each pixel is 10 bit, so the data throughput is 2Gbps. Since the FPGA used in this project is Spartan 6 series and it cannot deal with MIPI data directly, it is necessary to change these MIPI data into LVDS data beforehand. After receiving the processed sensor data, FPGA stores these data into DDR3 and output them through HDMI for display. The result shows that the data transmission and process of MIPI is stable and reliable which can be widely used in other MIPI sensor control.
KEYWORDS: Digital signal processing, Field programmable gate arrays, Logic, Image sensors, Clocks, Cameras, Image processing, Real time image processing, Data conversion, Image transmission
In the real-time image processing system, SRIO was used to meet the demands of massive data interacting capacity between FPGA and DSP. This paper realized the massive image data transmission between FPGA and DSP with SRIO. The image sensor outputs image data in 4 channels and the clock in each channel is 175MHz, five times of input clock. Since the data channel is double data rate, so the data rate of one channel is 350Mbps, the data rate of the whole image sensor is 1400Mbps. FPGA receives the sampled data from image sensor and reorganizes the image data, and then transmits the organized data to camera link interface for display testing on the one hand; on the other hand, FPGA transmits the sorted data to DSP via SRIO for further process. The SRIO transmission between FPGA and DSP uses x1 mode, 8b/10b coding, and the transmission rate is 2.5Gbps per lane. The result shows that the image in camera link interface is fine and the SRIO transmission is successful.
In this paper, a multi-line interferogram stitching method based on orthogonal shear using the Wollaston prism(WP) was proposed with a 2D projection interferogram recorded through the rotation of CCD, making the spectral resolution of Fourier-Transform spectrometer(FTS) of a limited spatial size increase by at least three times. The fringes on multi-lines were linked with the pixels of equal optical path difference (OPD). Ideally, the error of sampled phase within one pixel was less than half the wavelength, ensuring consecutive values in the over-sampled dimension while aliasing in another. In the simulation, with the calibration of 1.064μm, spectral lines at 1.31μm and 1.56μm of equal intensity were tested and observed. The result showed a bias of 0.13% at 1.31μm and 1.15% at 1.56μm in amplitude, and the FWHM at 1.31μm reduced from 25nm to 8nm after the sample points increased from 320 to 960. In the comparison of reflectance spectrum of carnauba wax within near infrared(NIR) band, the absorption peak at 1.2μm was more obvious and zoom of the band 1.38~1.43μm closer to the reference, although some fluctuation was in the short-wavelength region arousing the spectral crosstalk. In conclusion, with orthogonal shear based on the rotation of the CCD relative to the axis of WP, the spectral resolution of static FTS was enhanced by the projection of fringes to the grid coordinates and stitching the interferograms into a larger OPD, which showed the advantages of cost and miniaturization in the space-constrained NIR applications.
Fourier transform infrared spectroscopy is an important technique in studying molecular energy levels, analyzing material compositions, and environmental pollutants detection. A novel rotational motion Fourier transform infrared spectrometer with high stability and ultra-rapid scanning characteristics is proposed in this paper. The basic principle, the optical path difference (OPD) calculations, and some tolerance analysis are elaborated. The OPD of this spectrometer is obtained by the continuously rotational motion of a pair of parallel mirrors instead of the translational motion in traditional Michelson interferometer. Because of the rotational motion, it avoids the tilt problems occurred in the translational motion Michelson interferometer. There is a cosine function relationship between the OPD and the rotating angle of the parallel mirrors. An optical model is setup in non-sequential mode of the ZEMAX software, and the interferogram of a monochromatic light is simulated using ray tracing method. The simulated interferogram is consistent with the theoretically calculated interferogram. As the rotating mirrors are the only moving elements in this spectrometer, the parallelism of the rotating mirrors and the vibration during the scan are analyzed. The vibration of the parallel mirrors is the main error during the rotation. This high stability and ultra-rapid scanning Fourier transform infrared spectrometer is a suitable candidate for airborne and space-borne remote sensing spectrometer.
Imaging spectral is a novel detection approach which simultaneously acquires two-dimensional visual picture and
one-dimensional spectral information.The imaging spectrometer not only provides abundant data for aeronautics and
astronautics remote sensing, but also offers promising applications on biomedical imaging, conservation and identification
of art works,surveillance of food safety,prevention and control of plant diseases and elimination of pests,and so forth. In
this paper, the snapshot imaging spectrometer using image replication based on Wollaston prisms is designed. This system
includes the telescope objective, the collimator lens, the wave plates, Wollaston prisms, and the imaging lens.The imaging
spectrometer system based on multi-configuration can obtain a high diffraction efficiency. Every configuration provide a
kind of wave. The 16 configurations are in one mechanical structure. The system’s MTF at 56 line pairs is better than 0.75.
The RMS of the spots are all in one pixel.The imaging spectrometer can obtain perfect data.
Coded aperture spectroscopy allows for sources of large field to be efficiently coupled into dispersive spectrometers by
replacing the traditional input slit with a patterned mask. Spectral calibration is requisite for spectroscopy to obtain the
spectrum information exactly. In this paper, we described the spectral calibration’s principle and methods of coded
aperture spectral imaging, and then gave the results of the experiment using a monochromatic extended source, at last we
tested the accuracy of spectral calibration. The results indicate that this method can calibrate the coded aperture imaging
spectrometer with high accuracy.
In many modern optical systems, the resolution is limited not only by the diffraction caused by physical dimensions of the optics lens, but also by the CCD’s nonzero pixel size. Especially for the traditional incoherent illumination, the restriction of CCD pixel is greater than that of optical diffraction. Here we develop a novel approach to enhancing resolution beyond the limit set by CCD’s pixels, in which a two-dimensional and orthogonal encoding mask is attached before the imaging lens to modulate frequency on input target spectrum. Here we focus on the design about a 4f optical imaging system, considering the ability of Fourier transformation to achieve the equivalent conversion between space and frequency domain. And to prevent the loss of frequency in the overlapping regions when sampled by classical CCD, there must be some proportion between the spatial range of object plane and corresponding frequency plane. Meaning while, the wavefront aberration of Fourier lens needs to be controlled to fulfill the mathematical features of Fourier transformation. We apply to improving and revising the theoretical design for the encoding mask based on the design limit of opticalmechanical engineering, and we analyze the different orthogonal forms of encoding masks which can bring the spectra diffraction to the imaging area. According to the theoretical discussion, revision and algorithm simulation, the results in the preliminary testing system show that the encoding mask can be used to produce enhancement of resolution by a factor of 2 in-exchange for decreasing the field of view by the same factor.
Coded aperture spectral imaging is a new system to captures multiframes images and reconstructs them into spectral
image cube based on compressive sensing theory (CS). However, using dynamic transformed coded aperture pattern can
cause two primary problems, firstly the whole exposure procedure needs to be staring on the same surface feature which
is depended on a high quality stable platform; secondly the coded aperture’s transformation might reduce the system’s
stability. To avoid these problems without a loss of information for precise reconstruction, in the paper we propose
dividing the single image panel into encoding spatial overlapped sub-districts. We design a pushbroom scan pattern to
ensure each sub-district have enough sampling measurements. In each sub-district, we infer its measurement matrix can
satisfy the sparsely requirements needed for accurate estimation and final reconstruction with CS sampling. Considering
with efficiency and accuracy, we design a orthogonal self-loop coding mask (lines irrelevant) to guarantee the coding are
irrelevant among distinct snapshot of the same scene. The simulation experiment reveals the design helping reconstruct
the scene spectral cube with high throughput and resolution.
KEYWORDS: Mobile communications, Virtual reality, Mobile devices, Internet, Computing systems, Global Positioning System, Data communications, Wireless communications, Telecommunications, Cell phones
With the development of mobile technologies and the integration with the spatial information technologies, it becomes
possible to provide a potential to develop new techno-support solutions to Epidemiological Field Investigation especially
for the disposal of emergent public health events. Based on mobile technologies and virtual geographic environment, the
authors have designed a model for collaborative work in four communication patterns, namely, S2S (Static to Static),
M2S (Mobile to Static), S2M (Static to Mobile), and M2M (Mobile to Mobile). Based on the model mentioned above,
this paper stresses to explore mobile online mapping regarding mobile collaboration and conducts an experimental case
study of HFRS (Hemorrhagic Fever with Renal Syndrome) fieldwork, and then develops a prototype system of emergent
response disposition information system to test the effectiveness and usefulness of field survey based on mobile
collaboration.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.