Xiaoqiong Zhuang

Application of advanced IR-FPA in high-sensitivity pushbroom SWIR hyperspectral imager

High sensitivity SWIR(ShortWave Infra-Red) hyperspectral imager is benefit of national resources sensing. Background radiation results in noise and fluctuation of systems dark level, which does much harm to instruments radiometric performance. Basing on the analysis of background radiation and object reflectance signal, a SWIR hyperspectral system solution is given which utilize advanced infrared focal plane array technology. By system integration and testing, its showed that ROICs charge to voltage gain plays an important role in enhancing Signal to Noise Ratio(SNR). At lower light condition, high gain of ROIC and long integration time will lead to smaller dynamic range because of background radiation. A real-time background radiation monitoring method was validated which did a favor for eliminating background radiation in the image data.

High spectral resolution airborne short wave infrared hyperspectral imager

Short Wave InfraRed(SWIR) spectral imager is good at detecting difference between materials and penetrating fog and mist. High spectral resolution SWIR hyperspectral imager plays a key role in developing earth observing technology. Hyperspectral data cube can help band selections that is very important for multispectral imager design. Up to now, the spectral resolution of many SWIR hyperspectral imagers is about 10nm. A high sensitivity airborne SWIR hyperspectral imager with narrower spectral band will be presented. The system consists of TMA telescope, slit, spectrometer with planar blazed grating and high sensitivity MCT FPA. The spectral sampling interval is about 3nm. The IFOV is 0.5mrad. To eliminate the influence of the thermal background, a cold shield is designed in the dewar. The pixel number of spatial dimension is 640. Performance measurement in laboratory and image analysis for flight test will also be presented.

A short-wave infrared hyperspectral imager based on stepwise integrated filter

Space-borne hyperspectral imager is capable of providing large amount of image data with high spatial and spectral resolution. However, with the increase of the resolution, the volume and weight of conventional dispersive (prism/grating) imaging spectrometers also increase significantly. Meanwhile, the demand for the system sensitivity becomes even higher. In this paper, the application of Integrated Stepwise Filter (ISF) in infrared hyperspectral imaging technology was analyzed, including optical efficiency, instrumental background radiation suppression, spectral time delay integration (TDI) and other performances. Several methods which can enhance the system sensitivity were also provided. A compact short-wave infrared (SWIR) hyperspectral imager prototype covering the spectral range of 2.0μm-2.5μm with 6 TDI stages was designed and implemented. The results of the imaging experiment demonstrated that ISF has great application prospects in the field of high sensitivity space-borne hyperspectral imagery.

TDDA technology for high spatial resolution SWIR InGaAs imaging

With the development of remote sensing technology, shortwave infrared (SWIR) imaging technology has got more and more attention because of its ability through the fog and high spatial resolution. High spatial resolution SWIR imaging often requires high frame frequency. If the frame frequency is too high, it could cause the shortage of the image’s signal to noise ratio (SNR), seriously affecting image quality. In order to solve the contradiction between high spatial resolution and sensitivity, time delay and digital accumulation (TDDA) technology is proposed in this paper to improve system’s SNR and image quality. A prototype of SWIR imaging system based on a large format area InGaAs detector is designed, which demonstrates TDDA technology. The experiment results indicate that TDDA technology can increase system’s SNR of the square root of accumulative stage and improve image’s uniformity. The results in this paper are helpful for the improvement and application of high spatial resolution SWIR imaging technology.

A nonintrusive method for the measurement of infrared characteristics from engine exhaust plume

Nonintrusive measurements of infrared characteristics from engine exhaust plume are required for emission control or target tracking, due to the advantage of online measurement without affecting the exhaust plume. Conventional nonintrusive measurement techniques, e.g. the passive Fourier-transform infrared (FTIR) absorption spectrometry, lack prior knowledge of backgrounds and consume time to measure the complete infrared characteristics. Hence, an improved but simple nonintrusive method is proposed. Accordingly, a prototype system with a Mid-wave infrared imager has been developed and tested for the measurement of vehicle engine exhaust plume. Subsequently, the time-variant effective transmittance and emissivity is determined. Compared to the passive FTIR absorption spectrometry, this method incorporates a known background into the measurement and is more adequate for recording the rapidly changing exhaust plume radiation. Therefore, the accurate value of the transmittance and emissivity can be obtained. Further analysis reveals that the imager could be replaced with a dispersive spectrometer, which makes it feasible to acquire the absolute transmittance and emissivity with respect to wavelength. Thus, the concentration of specific toxic gases could be calculated following the radiance inversion technique.