Detecting infrared small targets in complex marine environments is an important technology in maritime distress target search and tracking systems. To enrich the feature representation of maritime targets and suppress background noise, a gated bidirectional pyramid context network (GBPC-Net) is proposed. Firstly, a hierarchical feature extraction backbone is constructed to generate multi-scale feature, and then a gated bidirectional connection module (GBCM) is designed to aggregate hierarchical features of infrared maritime targets and eliminate complex background interference. Among them, the channel-based GBCM adopts the directions of top-to-down and bottom-to-up to aggregate multi-scale features from different layers into semantic-assisted detail features and detail-assisted semantic features. While the spatial-based GBCM further hierarchically modulates channel aggregation features in different directions to generate multi-scale gated aggregation features. Next, an adaptive pyramid context module (APCM) is introduced to learn the similarity between the local detail and the context information of different scales, which can emphasize the difference between small maritime targets and complex backgrounds. Subsequently, the features from APCM are used to guide the fusion of detailed features in lower-layer networks, and the aggregated feature map is applied to infrared maritime target detection. Finally, a target detection dataset derived from the real marine environment is constructed, and a series of comparative experiments are conducted on this dataset and the results show that our method can more accurately detect infrared maritime targets than some state-of-the-art methods.
Infrared target detection is a key technology in maritime distress target search and tracking systems. Particularly, detecting small targets overwhelmed in heavy waves is an important and challenging task. In order to effectively enhance small infrared maritime target saliency and suppress heavy wave clutter, a small infrared maritime target detection method based on gradient amplitude difference and multidimensional dissimilarity measure is proposed in this paper. Firstly, we employ Sobel operator to measure the gradient amplitude difference (GAD) by calculating minimum component of gradient between horizontal and vertical directions. Meanwhile, we use facet kernel filtering followed by adaptive threshold segmentation to extract the sizes, shapes, and locations of candidate targets; then, multidimensional dissimilarity information, i.e. multi-direction and multi-scale, is constructed based on original infrared image and locations of candidate targets. Multidimensional dissimilarity measure (MDM) achieves target enhancement and background clutter suppression. The final saliency map is obtained by multiplying GAD and MDM. Finally, an adaptive threshold is used to segment targets from residual interferences. Experimental results on three real infrared maritime image sequences show that, the proposed method achieves better performance in terms of local contrast gain, background suppression factor, and detection probability with low false alarm. Our method performs more satisfactorily and robustly than the state-of-the-art methods.
Due to the light scattering and absorption phenomenon in underwater medium, underwater images always suffer from contrast degradation, detail loss, and color distortion. Color correction is an important process in dehazing underwater images, while current techniques could not remove color bias accurately. This paper introduces an effective color correction method for underwater image, which mainly contains three steps. First, a novel algorithm is proposed to choose the dominant and degraded channel(s) of input. Then a parameter adaptive-adjusted color compensation algorithm is proposed to compensate the degraded channels locally. Last, the traditional gray-world assumption and the famous histogram equalization operation is conducted on the color-compensated image to get the final result. Our experimental results demonstrate the superior performance of the proposed method in both subjective and objective evaluations.
With the continuous development of space technology, the requirements for the technology of modeling for infrared radiation of global background are becoming higher and higher. In this paper, a novel three-dimensional model for the infrared radiation of the global background is proposed, which is rich in elements and detailed information. In the modeling, it first uses latitude and longitude for fine mesh division. Then, this model not only comprehensively consider the terrestrial, oceanic and other elements of the surface of the earth, but also consider aerosols, molecules, the clouds with various types and other elements which are in the atmosphere. In addition, the characteristics of infrared emitted and reflected radiation of these elements under different area, elevation, time and season were researched. Finally, infrared images of global background were simulated, and the results was quantitative analyzed to discuss the model precision. The experimental results show that the proposed model can truly reflect the infrared radiation characteristics of global background, which could provide basic research reference for the studies on space target detection and remote sensing data analysis, etc.
In deep ocean applications, a camera’s viewing range is related to its low-light-level performance. Hence, a high-resolution ultra-low-light-level digital still camera (thereafter L3DSC), designed from the ground up for deep ocean autonomous underwater vehicle (AUV) imaging, is presented. A high-resolution (1024 × 1024) electron-multiplying CCD (EMCCD) is adopted as an image sensor to ensure low-light capability. A thermo electric cooler (TEC) is employed to lower image sensor temperature to promote low-light-level performance. Totem pole circuits that are able to generate 50-V pulse wave at 10 MHz are implemented to drive the EM pin, and power consumption of the circuit is optimized. An EMCCD digital image is buffered in a field-programmable gate array (FPGA) and then transferred through USB interface to a solid-state drive (SSD), which is installed in the image storage unit. The camera is controlled by AUV via Ethernet, and image data stored in the camera could be downloaded via the same interface after AUV retrieved from the sea. The camera module is mounted into a 6000-m depth-rate titanium alloy housing. The diagonal field of view is measured to be 58.4 deg in air. Experiments show that the minimum scene illumination of L3DSC is better than 5 × 10 − 4 Lux; underwater imaging distance is longer than 10 m, and total image data capacity is 200 gigabytes. These results demonstrate the camera’s low-light-level imaging performance and feasibility for AUV applications.
The acceleration of large coal base construction needs the modern management technology of heap storage as a guarantee. And the inventory of coal and other bulk commodities is an important aspect in the modern management technology of heap storage. Therefore, a rapid, accurate and simple method to measure the volume and quality of coal heaps for scientific management, economic benefit evaluation and storage evaluation of heap storage is very important which has a significant application value. In this paper, we introduce the structural features, working principle and application status of a new type portable heap bulk inventory system. Actual measurements have been carried out in the coal base located in Huanghua port, Tianjin and Qinhuangdao. The measurement results indicate that the system can measure the volume of bulk commodities efficiently, quickly and accurately, and it has extensive application prospects.
KEYWORDS: Reconstruction algorithms, Image enhancement, Image processing, Detection and tracking algorithms, Image analysis, Digital image processing, Chemical elements, Analytical research, Information science, Information technology
Aiming at reducing the number of iterations in variational method used to reconstruct image gradient field and overlarge data memory space caused by Kronecker’s direct product operation, the paper discusses a matrix transform method to complete the reconstructing of image gradient field. The algorithm maintains the size of matrix constant and requires no iterations and the algorithm’s time complexity and space complexity are O(N), which meets the basic requirements in engineering calculations.
Single-pixel imaging (SPI) represents a promising approach to multispectral imaging. We investigated the interband similarity of color images among red, green, and blue bands and found that it is highly possible for their wavelet coefficients to be at the same locations due to edges and transactions. Accordingly, we constructed a multiple measurement vectors model that includes a constraint under which the sparse coefficients of different bands have the same sparse structure, and then joint reconstruction is performed for all bands. We ran both simulated and actual experiments to validate the feasibility and effectiveness of the proposed method and found that compared with similar methods, it significantly improves the reconstruction quality of color SPI.
In order to realize accurate detection for small dim infrared maritime target, this paper proposes a target detection algorithm based on local peak detection and pipeline-filtering. This method firstly extracts some suspected targets through local peak detection and removes most of non-target peaks with self-adaptive threshold process. And then pipeline-filtering is used to eliminate residual interferences so that only real target can be retained. The experiment results prove that this method has high performance on target detection, and its missing alarm rate and false alarm rate can basically meet practical requirements.
The mobile pipeline-filtering algorithm is a real-time algorithm that performs well in detecting small dim targets, but it is particularly sensitive to interframe vibration of sequence images. When searching for small dim targets at sea based on an infrared imaging system, irregular and random vibration of the airborne imaging platform causes huge interference problems for the mobile pipeline-filtering. This paper puts forward a pipeline-filtering algorithm that has a good performance on self-adaptive anti-vibration. In the block matching method using the normalized cross-correlations coefficient (NCC), the interframe vibration of sequence images is acquired in real time and used to correct coordinates of the single-frame detection results, and then the corrected detection results are used to complete the mobile pipelinefiltering. Experimental results show that the algorithm can overcome the problem of interframe vibration of sequence images, thus realizing accurate detection of small dim maritime targets.
When searching for small targets at sea based on an infrared imaging system, irregular and random vibration of the airborne imaging platform causes intense interference for the pipeline-filtering, which is an algorithm that performs well in detecting small targets but is particularly sensitive to interframe vibrations of sequence images. This paper puts forward a pipeline-filtering algorithm that has a good performance on self-adaptive antivibration. In the block matching method that combines the normalized cross-correlations coefficient with the normalized mutual information, the interframe vibration of sequence images is acquired in real time and used to correct coordinates of the single-frame detection results, and then the corrected detection results are used to complete the pipeline-filtering. In addition, under severe sea conditions, small targets at sea may disappear transiently, leading to missing detection. This algorithm is also able to resolve this problem. Experimental results show that the algorithm can overcome the problem of interframe vibration of sequence images, thus realizing accurate detection of small maritime targets.
KEYWORDS: Sensors, Signal processing, Signal detection, Data acquisition, Data processing, Light sources, Reliability, Optical testing, Digital signal processing, Field programmable gate arrays
The four-quadrant detector is mainly used in high-precision displacement measurement and other related fields. With the emergence of displacement problem in a large number of projects, the displacement measurement accuracy, speed and reliability have become increasingly demanding. In this paper, the measurement principle of four-quadrant detector is analyzed theoretically, the displacement measurement system based on four-quadrant detector is designed, and the experimental platform is built to test and validate the stability, measurement accuracy and range of the displacement measurement system. Experimental results show that: the deviation of the same spot position on measurement system is less than 0.17μm. The measurement error of spot displacement is less than 3.7μm.
KEYWORDS: Sensors, Signal detection, Nonuniformity corrections, Light sources, Light, Data conversion, Data processing, Information science, Information technology, Photodetectors
The four-quadrant detector is mainly used for high-precision position measurement and related fields, and the
requirement of accuracy keeps increasing. The effection of photoresponse nonuniformity on measurement accuracy of
four-quadrant detector is analyzed theoretically in this paper. The correction method is proposed through calculation,
simulation and analysis. Finally, the experimental platform is built to verify. The results of experiments demonstrate that
after compensated correction, the nonuniformity of detector has been 46.17% compensated, the nonlinear deviation has
been decreased by 44.1%, the measurement accuracy of spot displacement has been improved by 1.33 times.
Using by different output transmittances of 2%, 5%, and 10%, we have investigated the continuously tunable laser performance of c-cut Tm:YAP crystal. The 5-mm long c-cut crystal with 4 at.% thulium ion was used. Without a tuning element, the slope efficiency respect to the absorbed pump power reached 44.1% with transmittance of 5%, corresponding to the conversion efficiency of 35.3%. The laser operated at TEM00 mode with a beam quality factor of M2 ∼ 1.3, which was demonstrated by a 90/10 knife-edge method. A 3-mm thick birefringent plate was used as a tuning element. At transmittance of 5%, the widest tunable range of 159 nm extended from 1899 to 2058 nm. For transmittances of 2% and 10%, the tunable ranges of 150 and 68 nm were achieved, respectively.
KEYWORDS: Photosynthesis, Luminescence, Statistical analysis, Atmospheric modeling, Carbon dioxide, Quantum efficiency, Electron transport, Temperature metrology, Data modeling, Imaging systems
Crop breeding and variety analysis play the important role in the national economy. A lot of sample data and typical
probability distribution are needed in the conventional methods to evaluate the high-yield crop cultivars such as
correlation analysis, regression analysis and grey relational grade analysis etc, which are difficult to be realized. Delayed
fluorescence (DF) can be used to evaluate plant photosynthesis. The current investigation has revealed that there is a
good linear correlation between DF and photosynthesis capacity. More importantly, the slopes of linear fit of the
correlationship for different yield varieties are different. Four known yield crop cultivars from each of the two different
species (Maize and Soybean) are selected as samples to be analyzed. The statistical results show that the slope of
high-yield variety is smaller than that of low-yield. We thus conclude that the slope of linear fit of correlation between
DF and photosynthesis capacity is an excellent marker for high-yield crop cultivars identification. Compared with the
conventional methods, the presented method needs less samples and it's fast and easy to be measured.
KEYWORDS: Photosynthesis, Control systems, Light emitting diodes, Measurement devices, Data acquisition, Luminescence, Signal attenuation, Signal processing, Instrument modeling, Environmental sensing
Photosynthesis is a very important chemical reaction in the plant, and its measurement plays critical role in the
agriculture production and science research of plant. Delayed fluorescence (DF) in plants is an intrinsic label of
efficiency of charge separation at P680 in photosystem II (PS II). In this paper, a portable photosynthesis rate
measurement device by means of DF is proposed. It can achieve DF of plant with high sensitivity and signal-to-noise
ratio basing on ultra-weak luminescence detection technique, and get photosynthesis rate by the corresponding relation
between DF and photosynthesis rate. The device has its illumination power and can obtain all-weather measurement with
less interference of the environment. Locale live survey can be realized by hermetic darkroom design and battery power
supply. The system carries out data acquisition and processing by single-chip microcomputer control. The results show
that this instrument has a lot of values such as low cost, high accuracy and good reliability and convenience.
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