KEYWORDS: Cameras, Infrared cameras, Signal to noise ratio, Signal processing, Infrared radiation, Sensors, Infrared imaging, Signal detection, Long wavelength infrared
When a space infrared camera has a higher temperature sensitivity , the more tiny temperature information it can record in the imaging data. High sensitive infrared camera takes an important role in observation of urban and sea targets and so on. A new space infrared camera system is designed based on pixel-level digital accumulation technology. The new infrared camera based on this technology realize the analog-to-digital convert of detecting signals into single detector pixel, which can reduce the noise caused by readout of analog signal markedly. This infrared system processes input signal by little capacitor packet digital-counting method,the integral capacitor plays the part of “voltage-to-frequency conversion”, which vary far from the traditional detector. The signal quantization process realized by the capacitor packet digitalcounting, every single charge packet is small, a capacitor of several fF in new system has the equal effect of a capacitor of thousands pF in traditional system, that makes the new infrared system can break the limit of integral capacitor’s physical restriction. So the new camera has the ability of achieving 1mK(0.001K) temperature sensitivity by theory without saturation electrons restriction. This ultra-high temperature sensitivity infrared camera system will break the temperature sensitivity limits of all infrared cameras on hand, and improve infrared system’s ability of distinguishing the tiny temperature a lot. The prototype camera has been manufactured and it has a 5mK NETD (Noise Equivalent Temperature Difference), the engineering feasibility of this camera system is valid. The pixel-level digital accumulation infrared camera will be an important development direction of future high-sensitivity space infrared camera technique.
High sensitivity is needed for space-based infrared weak target detecting. Pixel-level Digital Integration is an effective method for promoting detection sensitivity. It’s well suited for long integration time or high irradition targets detecting. To meet the application requirements, multistage digital TDI and secondary quantification were proposeed based on pixel-level digital integration. These methods could extend integration time equivalent and restrain quantization noise. The multistage digital TDI could overcome the problem of integral time limited by the dwell time of space-based platform. The secondary quantification could reduce quantization noise to an ignorable level and therefore promote system sensitivity efficiently to photon-noise limit. On this work in progress, detecting systems with milli-kelvin level sensitivity and for infrared weak targets could be carried out.
In this paper, the infrared radiation characteristics of sea background have been studied. First, MODTRAN4.0 was used to calculate the transmittance of mid-infrared and far-infrared, and the solar spectral irradiance, the atmospheric and sea surface radiation. Secondly, according to the JONSWAP sea spectrum model, the different sea conditions grid model based on gravity wave theory was generated. The spectral scattering of the sun and the atmospheric background radiation was studied. The total infrared radiation of the sea surface was calculated. Finally, the infrared radiation of a piece of sea surface was mapped to each pixel of the detector, and the infrared radiation is simulated. The conclusion is that solar radiance has a great influence on the infrared radiance. When the detector angle is close to the sun’s height angle, there will be bright spots on the sea surface.
This paper gives the preprocessing technique research which includes odd-even calibration, bad pixels compensation and non-uniformity calibration for the high sensitivity push-broom long wave infrared camera. The noise equivalent temperature difference (NETD) of the infrared camera has achieved less than 10 mK. The paper analyzes high sensitive imaging effects by using different preprocessing standards according to the test data, also analyzes the effects on imaging quality when using different preprocessing methods. At last the paper gives the suitable image preprocessing methods for the high sensitive infrared camera: the odd-even calibration method considering velocity to height ratio, the bad pixels compensation methods which are unique for temporal and spatial bad pixels and the non-uniformity calibration methods which combines the calibration based on black body testing data and the calibration based on real scene imaging data. It is validated that the residual nonuniformity of the infrared image can be reduced to 0.03% by using the preprocessing methods, which is satisfied for the requirement of high sensitive imaging.
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.