Research on autofocusing method with automatic calibration for aerial camera based on imaging resolution

摘要

Air materiel depot is a warehouse which store consumed all the parts and equipment vault of the plane. In order to ensure the various aviation equipment integrity of the backup piece rate, the inside temperature of depot must be controlled within a certain range. Therefore, the depot must be equipped a self-contained temperature real-time monitoring system. This paper presents a distributed temperature sensing alarm system to apply to real-time measure spatial distribution of temperature field. In order to eliminate influence to the scattering strength from the light source instability and the fiber bending splice loss and to improve temperature measurement accuracy, the system design used dual-channel dual-wavelength comparison method which make Anti-Stokes as signal channel and Stokes as a reference channel to collect signals of two channel respectively and detect the ratio of the two channels' signals. The light of LD directional coupling to the sensing optical fiber in the temperature field to test, domain reflect light from the sensing optical fiber directional coupling to receive channel again, Rayleigh domain reflect light is filtered after optical filter, the Anti-Stokes and Stokes are both taken out, converted and magnified, the two signals is digitalized by A/D Converter, and written to the storage machine , which linear cumulative to the content of the storage unit, The distributed measurement of the temperature field to test is finished. The collected 2900 measuring points real-time on 2km of optical fiber. The spatial resolution of the system was 0.7m, measurement range was -20-370 °C, and measurement error was ± 2 °C. All index of the system achieved the desired objective. To get an accurate temperature field spatial distribution and the information of temporal variation, the system enabled real-time temperature of aviation depot monitoring and early warning . As a new sensing technology, the distributed fiber optic sensor has the functions of self- calibration, self-calibration and self-test. Even when the fiber damaged, the distributed fiber optic sensor also can continue work and can detect the breakpoint location. The system can be applied to many engineering fields and has significant application value.