The aerial camera focal plane in the correct position is critical to the imaging quality. In order to adjust the aerial camera focal plane displacement caused in the process of maintenance, a new micro-displacement measuring system of aerial camera focal plane in view of the Michelson interferometer has been designed in this paper, which is based on the phase modulation principle, and uses the interference effect to realize the focal plane of the micro-displacement measurement. The system takes He-Ne laser as the light source, uses the Michelson interference mechanism to produce interference fringes, changes with the motion of the aerial camera focal plane interference fringes periodically, and records the periodicity of the change of the interference fringes to obtain the aerial camera plane displacement; Taking linear CCD and its driving system as the interference fringes picking up tool, relying on the frequency conversion and differentiating system, the system determines the moving direction of the focal plane. After data collecting, filtering, amplifying, threshold comparing, counting, CCD video signals of the interference fringes are sent into the computer processed automatically, and output the focal plane micro displacement results. As a result, the focal plane micro displacement can be measured automatically by this system. This system uses linear CCD as the interference fringes picking up tool, greatly improving the counting accuracy and eliminated the artificial counting error almost, improving the measurement accuracy of the system. The results of the experiments demonstrate that: the aerial camera focal plane displacement measurement accuracy is 0.2nm. While tests in the laboratory and flight show that aerial camera focal plane positioning is accurate and can satisfy the requirement of the aerial camera imaging.
Air material 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.
The automatic and accurate focal length measurement of aviation camera lens is of great significance and practical value. The traditional measurement method depends on the human eye to read the scribed line on the focal plane of parallel light pipe by means of reading microscope. The method is of low efficiency and the measuring results are influenced by artificial factors easily. Our method used linear array solid-state image sensor instead of reading microscope to transfer the imaging size of specific object to be electrical signal pulse width, and used computer to measure the focal length automatically. In the process of measurement, the lens to be tested placed in front of the object lens of parallel light tube. A couple of scribed line on the surface of the parallel light pipe’s focal plane were imaging on the focal plane of the lens to be tested. Placed the linear CCD drive circuit on the image plane, the linear CCD can convert the light intensity distribution of one dimension signal into time series of electrical signals. After converting, a path of electrical signals is directly brought to the video monitor by image acquisition card for optical path adjustment and focusing. The other path of electrical signals is processed to obtain the pulse width corresponding to the scribed line by electrical circuit. The computer processed the pulse width and output focal length measurement result. Practical measurement results showed that the relative error was about 0.10%, which was in good agreement with the theory.