A MINI MULTI-GAS DETECTION SYSTEM BASED ON INFRARED PRINCIPLE

To counter the problems of gas accidents in coal mines, family safety resulted from using gas, a new infrared detection system with integration and miniaturization has been developed. The infrared detection optics principle used in developing this system is mainly analyzed. The idea that multi gas detection is introduced and guided through analyzing single gas detection is got across. Through researching the design of cell structure, the cell with integration and miniaturization has been devised. The way of data transmission on Controller Area Network (CAN) bus is explained. By taking Single-Chip Microcomputer (SCM) as intelligence handling, the functional block diagram of gas detection system is designed with its hardware and software system analyzed and devised. This system designed has reached the technology requirement of lower power consumption, mini-volume, big measure range, and able to realize multi-gas detection.     

基于红外光谱技术的混合气体检测系统概述

为了给从事红外混合气体检测领域的研究人员提供一定的借鉴与参考,针对红外混合气体检测系统中的光学复用结构以及检测方法进行了详细评述。目前,以量子级联激光器(QCL)、带间级联激光器(ICL)为代表的相干光源已逐渐取代热辐射红外光源、红外发光二极管(LED)等传统非相干光源,成为红外混合气体检测中的主流光源。相应地,具有超高探测度和极短响应时间的红外光探测器也逐渐超越以往的红外热探测器,占据红外探测器领域的主导地位。基于“复用思想”的光学复用结构则是红外混合气体检测系统的核心,主要包括单光源复用检测结构和多光源复用检测结构。其中,单光源复用检测结构以其体积小、集成度高等优点成为构建便携式混合气体检测系统的重要选择;而多光源复用检测结构是时分复用、频分复用、波分复用等思想的具体化,并凭借其较宽的光谱覆盖范围、较高的光谱分辨率等优势成为当前混合气体检测系统中的主导结构。应用于红外混合气体检测的检测方法主要有非分光红外(NDIR)光谱技术、波长/频率调制光谱技术、腔增强光谱技术以及光声光谱技术等。研究人员可通过对红外混合气体检测系统各组成部分充分了解后,设计出实用的红外混合气体检测系统,对工农业生产、环境监测、生命科学等诸多领域都具有重要意义。     

Review on multi gas detector using infrared spectral absorption technology

To provide some references for researchers engaged in infrared multi gas detection, this study introduced the infrared multi gas detection system thoroughly from infrared light source, infrared detector, optical multiplexing structure, and detection method. Currently, the coherent source represented by quantum cascade laser has replaced the traditional incoherent source like thermal radiant infrared light source and became the dominant light source in infrared multi gas detection. Accordingly, the infrared photodetector is widely used. The optical multiplexing structure based on the “multiplexing thought” is the core of infrared multi gas detection system. It mainly includes the single-source multiplex detection structure and multi-source multiplexing detection structure. Nondispersive infrared spectroscopy, long optical distance spectroscopy, wavelength/frequency modulation spectroscopy, cavity enhancement spectroscopy, and photoacoustic spectroscopy are major detection methods used in the infrared multi gas detection. This has important significance to many fields, such as industrial and agriculture production, environmental monitoring, life science, etc.     

机载红外热像仪探测海面温度场的仿真计算

通过建立海洋背景下的红外辐射模型,对机栽红外探测系统所获得的热图进行了仿真计算,提出了一种从探测器红外焦平面上的探测像元到海面红外辐射单元的映射方法。利用MODTRAN软件计算了被探测海域各红外辐射单元通过大气传输后最终到达机载红外热像仪探测像元的红外辐射强度,最后利用Visual ＋＋结合计算机图形学方法实现了红外热图的仿真计算。仿真结果基本反映了海面温度场的红外特性。     

基于微机电系统红外光源的长光程气体检测

针对红外气体传感器对光源的要求,选用了一种宽波长、高调制频率、低功耗的小体积微机电系统(micro-electro-mechanic system, MEMS)红外光源作为辐射源,其各项性能均能很好的满足红外传感系统对于光源的要求。由于其面光源的朗伯辐射特性,整形之后的红外光数值孔径仍然很大,采用传统的长光程气室结构很难实现长光程从而提高系统的检测灵敏度。本文结合双波长单光路的差分检测方法,设计了一种基于积分球特性的吸收气室,有效地解决了MEMS红外光源在高灵敏度气体检测应用中难于实现长光程的问题;并运用光在传输过程中光通量守恒的原理,推导了此积分球吸收气室的等效光程,解决了积分球气室等效光程计算的难题;同时采用FPGA主控芯片对MEMS红外光源进行高频调制并处理探测器的输出信号,使得外围电路的设计更加简单、灵活。设计中,使用直径为5 cm的积分球吸收气室便可实现166.7 cm的等效光程,研究结果显示系统可测得的最小甲烷浓度达0.001×10-6,极大地提高了红外检测系统的灵敏度。     

大变倍比中波红外变焦系统的小型化设计

基于中波红外320240制冷型探测器,采用机械正组补偿方式,引入衍射光学元件（DOE）,并采用折叠光路,实现大变倍比中波红外变焦光学系统的小型化设计。利用变焦原理和Zemax光学设计软件给出系统结构参数,并对设计结果进行像质评价,对凸轮曲线求解等。设计与分析结果表明:系统使用6片透镜在3.7 m~4.8 m波段实现了18 mm~360 mm连续变焦,满足100 %冷光阑匹配,在空间频率16 lp/mm处MTF值均大于0.5。该系统具有大变倍比、变焦轨迹平滑等特点,可应用于机载光电侦察设备中。     

High-performance integrating infrared detector

Improvement in the performance of a Si: P integrating infrared (IR) detector are described. The detector has the structure of a p-i-n diode but the mode of IR detection involves photoemission of charge stored in localized impurity states in the i-region at low temperatures. After IR exposure, the remaining occupied localized states are field ionized. In order to measure the remaining charge, the transient field ionization current is digitized and integrated. Increased quantum efficiency is obtained by increasing the photosensitive i-region thickness and impurity concentration. With increasing impurity concentration, the quantum efficiency of a 110 μm thick detector can be increased from 0.5% to about 70% in the neighborhood of 27 μm while the maximum charge storage time (IR integration time) decreased from more than 12 h to about l s.     

一种基于MEMS光栅光调制器的近红外光谱探测系统

基于微机电系统技术的近红外光谱探测系统已成为了近红外光谱仪研究的一个新方向。文章提出了一种基于光栅光调制器的新型近红外光谱探测系统。该系统采用微加工技术制造的光栅光调制器阵列与单点近红外探测器相结合使用的方法进行光谱探测。设计了该光谱探测系统的光学结构, 论述了系统光谱探测原理, 并使用经表面微加工工艺得到的光栅光调制器器件进行了系统分辨本领、波长准确性、系统稳定性、器件响应频率等特征参数测试实验。结果表明,该探测系统在1 320到1 400 nm波长范围内,分辨本领小于10 nm, 波长准确性小于1 nm, 系统稳定性小于0.5%, 光栅光调制器的响应频率为5kHz。实验结果证明了该近红外光谱探测系统的可行性, 为研制基于微机电系统光栅光调制器的微型化近红外光谱仪提供了理论基础及实验指导。     

利用红外光谱吸收原理的CO浓度测量装置研究

介绍了一种基于红外光谱吸收原理 ,利用钽酸锂热释电探测器实现一氧化碳浓度测量的装置。该装置主要由探测器系统、信号放大与处理系统及显示报警系统三部分组成。介绍了该装置的工作原理、基本结构及主要技术指标。讨论了其中的技术难点及其相应的解决方法。     

A novel opto-mechanical uncooled infrared detector

This paper presents a novel opto-mechanical uncooled infrared detector that has successfully been fabricated. The detector is composed of a bi-material micro-cantilever array released from the Si substrate, whose reflector retains its shape even with changes in temperature. In comparison with the generally used sacrificial layer cantilever, the loss of incident IR energy caused by the reflection from and absorption by the silicon substrate is eliminated in this substrate-free structure. Moreover, the freestanding structure of the detector makes it easy to fabricate. The revised reflector in this structure has no distortion during its activity that keeps the sensitivity of the detector from being passivated. We present an infrared (IR) image of a person’s hand to demonstrate the ability of the structure to create images. The performance test showed that the noise-equivalent temperature difference of the imaging system can reach about 175 mK.     

集成式光读出FPA红外成像系统设计

本文对读出原理、像差要求、图谱质量进行深入研究,进而对读出技术进行深度整合与简化,实现光读出FPA红外成像系统小型化、轻量化、集成化。首先,从FPA的热-机械效应出发,介绍了光读出FPA红外成像系统的工作原理;然后,针对通常采用的光读出FPA红外成像系统体积大、重量大、结构复杂缺陷,提出了高集成度的新型光读出系统;接着,在分析讨论读出光路像差容限、特点的基础上,对以异形棱镜为核心元件的光读出系统进行了具体的光学仿真设计;最后,设计了集光、机、电、软技术的集成式光读出FPA红外成像系统。对系统样机测试结果表明:在确保成像性能的前提下,光读出FPA红外成像系统的体积减小到175 mm×83 mm×105 mm。以异形棱镜为核心元件的光读出技术,在满足成像精度和灵敏度的前提下,可减小读出系统的复杂程度,有效降低了光读出FPA红外成像系统的体积和重量,从而促进光读出FPA成像系统的工业化应用。     

A super-pixel QWIP focal plane array for imaging multiple waveband temperature sensor

The multi-waveband temperature sensor (MWTS) array, in which each super-pixel (2 × 2 pixel cell) operates at four distinct thermal infrared (IR) wavebands is being developed. Using this high spatial resolution, four-band thermal IR band detector array, accurate temperature measurements on the surface of an object can be made without prior knowledge of its exact emissivity. This multi-band detector involves intersubband transition in III–V semiconductor-based quantum layered structures. Each detector stack absorbs photons within the specified wavelength band while allowing the transmission of photons in other spectral bands, thus efficiently permitting multi-band detection. This produces multiple, spectrally resolved images of the scene that are recorded simultaneously in a single snapshot on the FPA. From the multispectral images and calibration information about the system, computational algorithms are used to evaluate the temperature on the surface of a target.     

Two-channel IR gas sensor with two detectors based on LiTaO3 single-crystal wafer

An infrared (IR) single-element detector based on a lithium tantalate (LiTaO₃) single-crystal wafer has been successfully fabricated. The preparation and design of the device are discussed and analyzed in detail. The processing of a thin LiTaO₃ wafer, the characterization of an IR filter window, and the assembly of the wafer and filter are explained. A LiTaO₃ sensor element, a CMOS amplifier, a narrow-band filter (which can be selected to operate within the appropriate spectral region), and the read-out circuits are set into a TO-18 vessel. Each TO-18-type detector offers a single channel (a single detection wavelength). Two TO-18 detectors with different filters, one acting as a detection channel and the other as a reference, a broadband light source, a circuit board and a flake of wire gauze are assembled and integrated into a gilded gas cell for the purpose of detecting ethene gas.     

基于热释电探测器DIGA数学模型

根据热释电探测器工作原理 ,对其使用特点进行了分析。在分光型红外气体分析器 (DIGA)设计原理基础上 ,建立了基于热释电探测器的红外气体分析系统输入输出数学模型。依据该模型研制了一个新型多组分红外气体分析器 ,并指出设计DIGA注意的若干问题。应用表明 ,该模型对DIGA的设计、研究、性能分析和进一步改进具有一定的参考价值     

A novel accurate and expandable infrared radiation transmission effect computing service

In infrared imaging simulation system, the infrared radiation transmission is significantly affected by natural environment. Attenuation and blurring are introduced by atmospheric environment impacts on the transmission process from zero sight infrared radiation to the detector. The classic IR transmission calculation methods have been intensively studied and many applicable approaches are proposed. The novel IR transmission effect computing service introduced in this paper could render accurate and expandable IR simulation result based on synthetic natural environment, especially concerning the atmosphere effects imposed on the IR transmission process. A simulation architecture is constructed and supports an infrared imaging simulation system for the IR transmission process calculation. The environment representation approach and the transmission effect calculation method were elaborated. Simulation experiment was carried out and the result was shown to be more accurate than that of conventional MODTRAN based atmosphere transmission simulation results. The two results are both compared with the physically captured image. The comprehensive simulation experiment results are implied to be competent and offered an applicable solution for the infrared imaging simulation system. Furthermore, this interdisciplinary simulation method can be extended to other synthetic natural environment supported military simulation and further serve the large-scale distributed collaborative combat simulation.     

Near-infrared methane sensor based on a distributed feedback laser

In this article, a near-infrared methane detection system using tunable diode laser absorption spectroscopy technology was designed and implemented. The distributed feedback laser was driven by a self-developed temperature and current controller to allow scanning the selected absorption wavelength at 1654?nm. Laser temperature fluctuation was lower than 0.01%, and the output emission wavelength was linear and stable. The emitted beam passed a reflective gas chamber and was received by the Indium Gallium Arsenide photodiode detector. Through a data acquisition card, a digital lock-in amplifier was developed to extract the second harmonics with real-time monitoring and adjustment. Based on Allan deviation analysis, the limit of detection was about 48?ppm with a path length of 30?cm, at an integration time of 6?s. The experimental results revealed a maximum detection error of less than 3% at a gas concentration higher than 100?ppm. The fluctuations rates in long-term (9?hr) stability measurements for 1?×?10³?ppm and 1?×?10⁴?ppm methane samples were 0.8% and 0.48%, respectively, indicating good stability for the sensor. In the control module design, compared with previous reports on methane detection systems, the current system uses a self-developed temperature controller, a current driver and a signal processor, to allow real-time display and adjustments. The potential for adjustable wavelength scanning is available for multi-gas detection based on a single detection system.     

Novel differentially strained p-doped quantum well infrared detector

We propose a differentially strained p-doped quantum well infrared (IR) photodetector that achieves high performance specifications. We examine key device and material considerations for such a detector for near 10 μm detection. We calculate that through differential strain, this novel detector has improved gain and substantially reduced dark current over previous quantum well IR photodetectors, while being able to detect normal incident light.     

Complementary barrier infrared detector (CBIRD) with double tunnel junction contact and quantum dot barrier infrared detector (QD-BIRD)

The InAs/GaSb type-II superlattice based complementary barrier infrared detector (CBIRD) has already demonstrated very good performance in long-wavelength infrared (LWIR) detection. In this work, we describe results on a modified CBIRD device that incorporates a double tunnel junction contact designed for robust device and focal plane array processing. The new device also exhibited reduced turn-on voltage. We also report results on the quantum dot barrier infrared detector (QD-BIRD). By incorporating self-assembled InSb quantum dots into the InAsSb absorber of the standard nBn detector structure, the QD-BIRD extend the detector cutoff wavelength from ∼4.2 μm to 6 μm, allowing the coverage of the mid-wavelength infrared (MWIR) transmission window. The device has been observed to show infrared response at 225 K.     

激光本振红外光谱干涉成像及其艇载天文应用展望(特邀)

本文分析了红外干涉成像现状和难点,介绍了激光本振红外相干探测的原理,阐述了基于电子学的红外光谱细分和干涉成像原理,讨论了激光本振红外阵列探测器形式.激光本振和相干探测器的设置,可保证两个望远镜的红外信号相位的正确传递,在电子学实施窄带滤波形成的窄带红外信号有利于实现长基线干涉成像.在此基础上,类似微波综合孔径射电望远镜...     

基于二元光学的红外成像光谱仪离轴系统设计

对Lyons采用二元光学元件的红外成像光谱仪的设计理论进行了分析，为消除其二元光学元件作为透射式成像元件导致的焦距随波长的变化而变化的缺陷.提出将离轴三反射镜系统与具有二元光学透镜的变焦距系统相结合的新技术方案，并从军事目标的红外热探测的基本要求出发，给出了具体的设计实例.设计结果表明，系统具有设计精巧、结构简单、光能接收率高、消像差特性好、对材料的要求低以及满意的红外焦平面凝视阵列探测器的配准精度和探测精度.