Research On Infrared Theodolite Design And Key Technologies To Improve The Radiometry Precision

Infrared radiometry is one of the basic technologies of acquiring surface temperature distribution of the target, detecting infrared targets and evaluating infrared stealthy effectiveness. With the development of the infrared detector and the measurement and control technology, more and more high precision ground based infrared imaging systems(such as infrared theodolite) are widely applied in infrared radiometry of military targets. Compared with the visible light TV, infrared imaging systems are significantly influenced by environmental factors, especially the ambient temperature. Due to the complexity of the field measurement test conditions and diversity of the targets, improving radiation measurement precision of the infrared theodolite has always been a challenge. This paper studies the radiometric calibration and measurement model and designed the infrared theodolite on the basis of existing optical theodolite TV. Then the infrared radiometry error sources are analyzed in detail considering the factors such as the imaging system, atmosphere, background radiation and the radiation characteristics of the target. Finally, several methods to improve the precision of radiometry are put forward on the basis of the analysis above. The methods involves improvements of structure design, calibration method and radiation inversion algorithm. The contributions of this thesis are summarized as follows:(1) The existing technologies of infrared radiometry at home and abroad are studied in detail. We deduce the system output as a function of parameters namely radiance, integration time and the ambient temperature. Then an integrated radiometric calibration and measurement is established based on the research on high dynamic radiometric calibration and non-uniformity correction. The researches above provide reliable theoretical supports for further study on radiometric calibration and radiometry error analysis.(2) Fundamental structures of infrared theodolite are designed, for instance the gimbal, the cross, the primary and secondary mirror system, the automatic focusing system, and the automatic switch mirror.(3) According to the established radiometric calibration and measurement model, this thesis analyzes the infrared theodolite’s main source of measurement error. Infrared system is composed of optical system, mechanical structure and detector. This thesis studies the influence of ambient temperature and stray radiation on infrared system response. In addition, calibration error, atmospheric transmission influence factors and the target itself are also important error sources of radiometry.(4) According to theoretical analysis, this thesis puts forward a variety of methods to improve the radiometry precision of the infrared theodolite, covering structure design improvements, output gray value drift compensation, a new calibration method and the atmospheric transmission correction, etc. The research focuses on software calculation and measurement method of internal and external stray radiation, and proposes stray radiation suppression projects based on structural modifications. A calibration scheme for large diameter high dynamic range infrared theodolite is proposed. A collimator combined with a blackbody is used as the calibration source. We achieve high dynamic range calibration and measurement using several neutral attenuation filters and multiple integration times.(5) Characteristics of different targets are studied to satisfy the demands of radiometry of a variety of infrared targets. Then, two small target radiation measurement methods are proposed, in order to improve the measurement precision and expand the use of the infrared radiometry system. Finally infrared radiometry experiments in the fields are carried out to test the accuracy of the infrared theodolite designed in this paper.In this thesis, infrared theodolite design, principles of radiometry and error sources are studied. A variety of solutions, consist of developments in optical-mechanical structure design and measurement algorithm, for improving the infrared theodolite measuring accuracy are proposed. The achievements in this paper yield important theoretical and practical significance on further researches on target radiation characteristics measurement and infrared imaging system design.