Dual-band Imaging System Research Articles

An unmanned aerial vehicle (UAV)-borne dual-band polarization imaging system for evidence search

Existing evidence search systems mostly adopt traditional intensity imaging, which has low image contrast and is easily affected by environmental conditions, thus making it difficult to accurately identify the target and unable to meet the demand for evidence search in the case scene. To solve the aforementioned problems, we propose a combined visible polarization and long-wave infrared evidence search method, developed a high-resolution polarization imager, and perform a test to detect evidence with visible polarization and long-wave infrared imaging on unmanned aerial vehicles (UAVs). The results show that the target contrast is 10–20 % higher than that of traditional intensity imaging. And contrast ratio can be improved by up to 30% after graphics fusion processing. Therefore, the application of visible polarization and infrared combined imaging detection technology can significantly improve the search capability and system environmental adaptability of the evidence at the crime scene. In conclusion, the findings can significantly improve the efficiency of the case and are of great importance for effective and rapid search for evidence.

Design method of dual-band synchronous zoom optical system based on co-path zoom groups

The dual-band zoom imaging system has great application value in military and civilian fields with the advantages of a large field of view (FOV) search, long-range tracking, camouflaged target reconnaissance, and all-day operation. To address the problem of synchronous zoom in dual-band co-aperture zoom optical systems, a dual-band simultaneous zoom optical system design method based on the co-path zoom groups is proposed. This optical system can realize zooming simultaneously in visible (VIS) and shortwave infrared (SWIR) bands and effectively control the total length. We first analyze the synchronous zoom principle of the dual-band co-path zoom optical system, then we propose a joint solution method for solving the initial structure of the dual-band zoom optical system. After obtaining the initial structure parameters, we performed the real-lens replacement and aberration correction in Zemax. Finally, a dual-band co-path simultaneous zoom optical system with working bands of 900∼1700 nm and 480∼660 nm, and zoom ranges of 10∼150 mm and 100∼150 mm, respectively, was designed. The focal length difference of the dual-band optical system is less than 0.16% during the simultaneous zooming process, and the system also has the advantages of good imaging quality, compact structure, simple zoom structure, and smooth cam curve.

Small Zoom Mismatch Adjustment Method for Dual-Band Fusion Imaging System Based on Edge-Gradient Normalized Mutual Information.

Currently, automatic optical zoom setups are being extensively explored for their applications in search, detection, recognition, and tracking. In visible and infrared fusion imaging systems with continuous zoom, dual-channel multi-sensor field-of-view matching control in the process of synchronous continuous zoom can be achieved by pre-calibration. However, mechanical and transmission errors of the zoom mechanism produce a small mismatch in the field of view after co-zooming, degrading the sharpness of the fusion image. Therefore, a dynamic small-mismatch detection method is necessary. This paper presents the use of edge-gradient normalized mutual information as an evaluation function of multi-sensor field-of-view matching similarity to guide the small zoom of the visible lens after continuous co-zoom and ultimately reduce the field-of-view mismatch. In addition, we demonstrate the use of the improved hill-climbing search algorithm for autozoom to obtain the maximum value of the evaluation function. Consequently, the results validate the correctness and effectiveness of the proposed method under small changes in the field of view. Therefore, this study is expected to contribute to the improvement of visible and infrared fusion imaging systems with continuous zoom, thereby enhancing the overall working of helicopter electro-optical pods, and early warning equipment.

Optical design of athermalized infrared dual-band annular folded lens with multilayer imaging diffractive optical elements

In order to realize the miniaturization of the infrared dual-band imaging system, a common optical path annular folded lens (AFL) with multilayer imaging diffractive optical element (MIDOE) is designed in this paper. The design principle of the AFL is studied, and the relationship between the obscuration ratio and the field of view is given. For the wide temperature range, the theoretical model of the optimal substrate materials selection for the MIDOE is established to achieve the high diffraction efficiency. According to theory analysis, the infrared dual-band AFL with IRG26-ZNS MIDOE is designed in the mid-wave infrared (MWIR) 3∼5 μm and long-wave infrared (LWIR) 8∼12 μm. The focal length is 50 mm, the equivalent F number is 1, and the full field of view is 14 ° The modulation transfer function (MTF) curves of each field of view are close to the diffraction limit when the spatial frequency is 20lps/mm, and the MTF values are greater than 0.61 and 0.28 in MWIR and LWIR, respectively. When the ambient temperature ranges from -40 °C to 80 °C, the high image quality is achieved in dual-band. In addition, the tolerance analysis is performed to verify machinability of the system. The research in this paper has important significance for the realization of a new generation of the low-cost, integrated dual-band imaging system.

Modeling and evaluation of performance of dual field-of-view common-aperture dual-band imaging system

For the modeling and evaluation of dual field-of-view (FOV) common-aperture dual-band imaging system performance, two factors must be considered at the same time. One is that the system must have a larger target acquisition range, and the other is that the detection range and recognition range of the system must be the same. In this paper, taking the dual FOV common-aperture visible/long-wave infrared (LWIR) imaging system as an example, the performance of the dual FOV common-aperture dual-band imaging system is modeled and evaluated using an imaging system performance model based on comprehensive resolution. Firstly, the target acquisition range of the dual FOV visible imaging system is analyzed, and the condition that the detection range is equal to the recognition range is obtained. Then, under the condition of common aperture, the target acquisition range and the relationship between detection range and recognition range of dual FOV LWIR imaging system are analyzed. The analysis results show that, under the condition of dual FOV and common aperture, when the detection and recognition ranges of the visible imaging system are equal, the detection and recognition ranges of the LWIR imaging system are not equal. When the detection and recognition ranges are close by reducing the comprehensive resolution, the target acquisition range of the dual FOV common-aperture dual-band imaging system will decrease.

Design of a Dual-Band Compact Integrated Remote Sensing System for Visible Light and Long-Wave Infrared

This paper presents a design of a dual-band integrated space telescope system for visible light and long-wave infrared. The system can simultaneously image the visible light band of 450–900 nm and the long-wave infrared band of 7700–10,500 nm. The dual-band integrated imaging system can freely switch the observation band to adapt to different scenes and environmental changes. The camera can also further expand its capabilities in the fields of multi-spectral observation and low-light observation by collocation with different detectors. This design is based on a coaxial reflection system, the two bands share the camera’s primary and secondary mirrors, and the separation of the two bands is achieved through a separate field of view design. After simulation, the average Modulation Transfer Function (MTF) value of the visible light band of the system at 50 lp/mm (line pairs per millimeter) reaches 0.45, and the average MTF value of the long-wave infrared band at 50 lp/mm reaches 0.36. In addition, tolerance analysis, ambient temperature analysis and transmittance analysis of the integrated system are carried out in this paper to further improve the integrated system scheme, and the feasibility of the system is further verified.

Design of infrared dual-band common path annular aperture ultrathin imaging system

In order to solve the problems of the large number of components and complex structure in the mid-long wave infrared dual-band system, the structural characteristics of the annular folded imaging system was analyzed, and the calculation method of the obscuration ratio was explained. An infrared dual-band annular aperture ultrathin imaging system with common path was designed. The focal length is 50 mm, the field of view is 14°, and F number is 1. The system is made up of only one optical element, so it has simple structure and compact optical path. The ratio of total optical length to focal length is 0.48. At the spatial frequency of 20 lp/mm, the modulation transfer function (MTF) of the full field of view is more than 0.45 in medium wave infrared 3-5 μm, and that is more than 0.30 in long wave infrared 8-10 μm. The athermalization of system is realized in the range of −40-80 ℃. According to the tolerance results, this system is machinable. The chalcogenide glasses used for the substrate material can be precision molded to achieve batch processing. The study provides a new idea for the realization of low-cost and miniaturized infrared dual-band system.

Design of two-DMD based zoom MW and LW dual-band IRSP using pixel fusion

In order to test the anti-jamming ability of mid-wave infrared (MWIR) and long-wave infrared (LWIR) dual-band imaging system, a zoom mid-wave (MW) and long-wave (LW) dual-band infrared scene projector (IRSP) based on two-digital micro-mirror device (DMD) was designed by using a projection method of pixel fusion. Two illumination systems, which illuminate the two DMDs directly with Kohler telecentric beam respectively, were combined with projection system by a spatial layout way. The distances of projection entrance pupil and illumination exit pupil were also analyzed separately. MWIR and LWIR virtual scenes were generated respectively by two DMDs and fused by a dichroic beam combiner (DBC), resulting in two radiation distributions in projected image. The optical performance of each component was evaluated by ray tracing simulations. Apparent temperature and image contrast were demonstrated by imaging experiments. On the basis of test and simulation results, the aberrations of optical system were well corrected, and the quality of projected image meets test requirements.

A Novel Anti-Spoofing Solution for Iris Recognition Toward Cosmetic Contact Lens Attack Using Spectral ICA Analysis.

In this study, we maneuvered a dual-band spectral imaging system to capture an iridal image from a cosmetic-contact-lens-wearing subject. By using the independent component analysis to separate individual spectral primitives, we successfully distinguished the natural iris texture from the cosmetic contact lens (CCL) pattern, and restored the genuine iris patterns from the CCL-polluted image. Based on a database containing 200 test image pairs from 20 CCL-wearing subjects as the proof of concept, the recognition accuracy (False Rejection Rate: FRR) was improved from FRR = 10.52% to FRR = 0.57% with the proposed ICA anti-spoofing scheme.

Image registration for a UV–Visible dual-band imaging system

The detection of corona discharge is an effective way for early fault diagnosis of power equipment. UV–Visible dual-band imaging can detect and locate corona discharge spot at all-weather condition. In this study, we introduce an image registration protocol for this dual-band imaging system. The protocol consists of UV image denoising and affine transformation model establishment. We report the algorithm details of UV image preprocessing, affine transformation model establishment and relevant experiments for verification of their feasibility. The denoising algorithm was based on a correlation operation between raw UV images, a continuous mask and the transformation model was established by using corner feature and a statistical method. Finally, an image fusion test was carried out to verify the accuracy of affine transformation model. It has proved the average position displacement error between corona discharge and equipment fault at different distances in a 2.5m-20 m range are 1.34 mm and 1.92 mm in the horizontal and vertical directions, respectively, which are precise enough for most industrial applications. The resultant protocol is not only expected to improve the efficiency and accuracy of such imaging system for locating corona discharge spot, but also supposed to provide a more generalized reference for the calibration of various dual-band imaging systems in practice.

Stray light analysis on infrared channel of dual-band imaging system

Stray light analysis on infrared channel of dual-band imaging system

Practical dual-band terahertz imaging system.

This paper introduces a dual-band terahertz imaging system as a potential product for nondestructive testing using heterodyne detectors and continuous-wave sources. The operating frequencies of the system are 110.4 and 220.8 GHz. Multiband fusion technology combines the advantages of the greater spatial resolution of the high-frequency band and the enhanced sensitivity of the low-frequency band to improve the detection ability of the system. Additionally, the interference cancellation technology is used to obtain a superior image quality. The spatial resolution of this system was approximately 3 mm. The results show that the system can be used for bonding quality and embedded defect detection in radomes and foam materials adhered to metal plates in aircrafts.

Processing and fusion of passively acquired, millimeter and terahertz images of the human body

A passive, millimeter wave (MMW) and terahertz (THz) dual-band imaging system composed of 94 and 250 GHz single-element detectors was used to investigate preprocessing and fusion algorithms for dual-band images. Subsequently, an MMW and THz image preprocessing and fusion integrated algorithm (MMW-THz IPFIA) was developed. In the algorithm, a block-matching and three-dimensional filtering denoising algorithm is employed to filter noise, an adaptive histogram equalization algorithm to enhance images, an intensity-based registration algorithm to register images, and a wavelet-based image fusion algorithm to fuse the preprocessed images. The performance of the algorithm was analyzed by calculating the SNR and information entropy of the actual images. This algorithm effectively reduces the image noise and improves the level of detail in the images. Since the algorithm improves the performance of the investigated imaging system, it should support practical technological applications. Because the system responds to blackbody radiation, its improvement is quantified herein using the static performance parameter commonly employed for thermal imaging systems, namely, the minimum detectable temperature difference (MDTD). An experiment was conducted in which the system’s MDTD was measured before and after applying the MMW-THz IPFIA, verifying the improved performance that can be realized through its application.

Simultaneous Dual-Color Fluorescence Microscope: A Characterization Study

Background: High spatial resolution and geometric accuracy is crucial for chromosomal analysis of clinical cytogenetic applications. High resolution and rapid simultaneous acquisition of multiple fluorescent wavelengths can be achieved by utilizing concurrent imaging with multiple detectors. However, such class of microscopic systems functions differently from traditional fluorescence microscopes.Objective: To develop a practical characterization framework to assess and optimize the performance of a high resolution and dual-color fluorescence microscope designed for clinical chromosomal analysis.Methods: A dual-band microscopic imaging system utilizes a dichroic mirror, two sets of specially selected optical filters, and two detectors to simultaneously acquire two fluorescent wavelengths. The system’s geometric distortion, linearity, the modulation transfer function, and the dual detectors’ alignment were characterized.Results: Experiment results show that the geometric distortion at lens periphery is less than 1%. Both fluorescent channels show linear signal responses, but there exists discrepancy between the two due to the detectors’ non-uniform response ratio to different wavelengths. In terms of the spatial resolution, the two contrast transfer function curves trend agreeably with the spatial frequency. The alignment measurement allows quantitatively assessing the cameras' alignment. A result image of adjusted alignment is demonstrated to show the reduced discrepancy by using the alignment measurement method.Conclusions: In this paper, we present a system characterization study and its methods for a specially designed imaging system for clinical cytogenetic applications. The presented characterization methods are not only unique to this dual-color imaging system but also applicable to evaluation and optimization of other similar multi-color microscopic image systems for improving their clinical utilities for future cytogenetic applications.

Design strategy for broadband or dual-band ultrathin imaging system

Using reflective multiple-fold approach can reduce bulk and weight compared with large high-quality optical systems and improved resolution and light collection compared with miniature conventional systems. Air-spaced concentric multi-reflection (ACMR) systems, where two reflective surfaces surround a hollow cavity, are useful for extended focal distance, achromatic aberration, useful for inexpensive, lightweight IR imagers and may lead to convenient designs for broadband or dual-band imagers. Design a camera, which spectral response 2⿿12μm, with a total thickness of 30mm, 130mm effective focal length, ±4.2° FOV, 0.022mrad resolution and 68mm effective aperture, 96mm outer aperture. Application can fit into the hull or wing of a micro-UAV aircraft, which weight and thickness are tightly constrained, for long range surveillance.

Kinetic inductance detectors for millimeter and submillimeter astronomy

We present recent developments in Kinetic Inductance Detectors (KID) for large arrays of detectors. The main application is ground-based millimeter wave astronomy. We focus in particular, as a case study, on our own experiment: NIKA (N\'eel IRAM KID Arrays). NIKA is today the best in-the-field experiment using KID-based instruments, and consists of a dual-band imaging system designed for the IRAM 30 meter telescope at Pico Veleta. We describe in this article, after a general context introduction, the KID working principle and the readout electronics, crucial to take advantage of the intrinsic KID multiplexability. We conclude with a small subset of the astronomical sources observed simultaneously at 2 mm and 1.4 mm by NIKA during the last run, held in October 2010. Nous d\'ecrivons les r\'ecents d\'eveloppements concernant les grandes matrices de d\'etecteurs \`a inductance cin\'etique (KID) dont l'application principale est l'astronomie millim\'etrique au sol. Nous d\'etaillons en particulier notre propre cam\'era : NIKA (N\'eel IRAM KID Arrays) qui est aujourd'hui l'instrument le plus abouti mettant en oeuvre des KIDs. NIKA est une cam\'era bi-bande con\c{c}ue pour le radiot\'elescope de 30 m\`etres de l'IRAM \`a Pico Veleta. Apr\'es avoir d\'ecrit le contexte instrumental dans lequel ils s'inscrivent, nous expliquerons le principe de fonctionnement des KIDs et de leur \'electronique de lecture, cruciale pour pouvoir tirer parti de leur potentiel de muliplexage. Pour finir, nous pr\'esentons quelques exemples d'observations effectu\'ees par NIKA dans les bandes de 2 mm et 1,4 mm au cours de la derni\`ere campagne d'observation en octobre 2010.

Design and calibration of a dual-band imaging system

A prototype portable multispectral imaging system, in terms of design, fabrication, compactness, and cost effectiveness was developed for real-time contaminant detection in poultry processing plants. The prototype system developed in this research was a dual-band spectral imaging system that acquired two different spectral images simultaneously. This was accomplished by using a two-port imaging system that consisted of two identical monochrome cameras, optical components, and two interchangeable optical filters. Spectral reflectance from an object was collimated by lenses and split identically in two directions by a beamsplitter. Focusing lenses behind a beamsplitter projected each image on its respective sensor. Two optical bandpass filters determined the spectral characteristics of each image and are easily interchangeable. In order to co-register two-band images, a system-specific calibration algorithm was developed that corrected lens distortions and lens-sensor geometric misalignments. The prototype imaging system and the system calibration algorithm were tested for image registration accuracy. The imaging system acquired two-band images of 3D object with less than 8.1 μm error in terms of the position of the sensor. The prototype system was able to effectively detect feces (duodenum, cecum, colon) and ingesta on the surface of poultry carcasses.