KEYWORDS: Light emitting diodes, Cameras, Calibration, Time metrology, Signal processing, Image processing, Lamps, Design and modelling, Data analysis, Visible radiation
When the photoelectric theodolites are used to measure the same object, the values of timing equipment between the devices have deviation as well as the response of the camera and other devices also has difference. This situation leads to certain deviation of the synchronization of each device. At the same time, the exposure time of the camera deviates from the set value, which affects both the center exposure system and the front exposure system. The above situation leads to the time misalignment error of the target image when multiple photoelectric theodolites synchronously observe the same target. This error affects the accuracy of data processing and makes the calculation result unable to meet the measurement equipment of high accuracy undershoot. To measure the exposure time and the time deviation between camera, this paper studied the detection method based on calibrating lamp and experimented with this method. As a result, the detection method based on calibrating lamp can be used to measure exposure time both in visible light and shortwave as well as the time deviation detection. The detection accuracy is up to 5us. This method can be widely used in the camera detection of time deviation in optical equipment.
This paper proposes a improved method for measuring the focal length of a telephoto lens. In this paper, a photoelectric theodolite with high accuracy of angle measurement is used. Besides, a CMOS camera is used to take a position image of the center point of the theodolite, and the corresponding azimuth displayed by the theodolite is recorded. Leveling the optoelectronic theodolite on the open field, Polaris is used as a point light source outdoors. Adjusting the point target on the CMOS image, by which the target is placed in the view center of the field (crosshair center). And then, the pitch and azimuth data of the device are recorded. Adding disturbance to the photoelectric theodolite, the CMOS images is recorded. Adapting methods of target feature segmentation, sub-pixel positioning is performed on the point target image which captured by the CMOS camera. And the point target coordinates is obtained. Finally, the result based on the theodolite angle offset, sub-pixel offset and elevation angle data is calculated. The perturbation data is averaged to calculate the focal length of the telephoto lens. Compared with equipment testing result of focal length, experiments have achieved high measurement accuracy. And this method is suitable for detecting the focal length of an optoelectronic device in an outdoor environment.
As the lightwave passing through the atmosphere, the light’s path is not the uniform linear motion as well as the path has been bent, which causes the atmospheric refractive error of lightwave. As usual, two photoelectric theodolites are used to supply data for refractive error calculation. In the case of one photoelectric theodolite in the same time or the same area, the calculation method above is not suitable. This article proposes the calculation method of atmospheric refractive error based on single photoelectric theodolite which needs radar ranging to the flight target. First, station coordinate system is built and the station of photoelectric theodolite should be transformed to the system as well as the station of radar. Second, the original geocentric distance should be cut to L levels by lightwave refraction index from the station of photoelectric theodolite and the apparent distance between photoelectric theodolite and flight target is calculates. Third, the calculated geocentric distance should be cut to L levels by lightwave refraction index and the geocentric angle between photoelectric theodolite and flight target is calculated. At last, both the real elevation angle of photoelectric theodolite to the flight target and lightwave’s atmospheric refractive error are calculated by formula of elevation angle. The calculation method of atmospheric refractive error in this article only uses data of single photoelectric theodolite, as well as definite integral formulas of both apparent distance and geocentric angle are optimized, by which more accuracy error calculation of lightwave’s atmospheric refraction can be achieved.
Accuracy Measurement on aerial track of moving target is one of the major target for photoelectric theodolite, which target is solved by angle intersection algorithm of two-stations. For analyzing the accuracy and the photoelectric theodolite of the angle intersection measurement, this paper simulated 6 aerocrafts’ tracks. L,K algorithms of coplanar rendezvous and MLE algorithms of non-uniplanar intersection were used to measure aerocrafts’ tracks. The measurement result was relative analyzed with simulation track in angle intersection, then the L,K ,MLE algorithm’s applicability was fixed. One aerocraft track of simulation was chosen to measure by MLE algorithm in different station-setting conditions. The measurement error was compared in intersection angle, azimuth angle, pitching angle, baseline length, station location. And the relation between the conditions and measurement accuracy of tracks was fixed. Also the condition of station-setting was fixed. The work above has directive significance in the intersection algorithm choice and station-setting later.
Measurement elements of optical equipment are teams of A, E, which is shorten as nAE. The nAE is belong to angle intersection measurement mechanism [1]. The optical equipment usually supplies angle information only, two-stations theodolites or n-station theodolites are used in solid intersection measurement, and spacial coordinate of aerocraft is fixed [2]. This method is called angle intersection measurement. This article simulated 4 aerocrafts tracks, and used 3 algorithms above to measure the tracks [3]. The measurement result was relative analyzed with simulation tracks in intersection angle, and the L, K, MLE algorithm’s applicability was fixed [4].
Usage of photoelectric theodolite faces the problem of station-setting, and the station-setting directly influences the measurement accuracy of track [5]. This article chooses one aerocraft track to measure by MLE algorithm in different condition of station-setting. The measurement error was relative analyzed in intersection angle, azimuth angle, pitching angle, baseline length and station location, by which the relation between measurement accuracy and 5 conditions was fixed. The condition of station-setting was fixed on the base.
Most aircrafts is driven by chemic energy which is released in the combustion process. For improving the capability of engine and controlling the running on-time, the processes of fuel physics and chemistry need to be analysis by kinds of high quality sensor. In the research of designing and improving the processes of fuel physics and chemistry, the concentration, temperature and velocity of kinds of gas in the combustor need to be detected and measured. In addition, these engines and research equipments are always in the harsh environment of high temperature, high pressure and high speed. The harsh environment needs the sensor to be high reliability, well repetition, no cross- sensitivity between gases, and the traditional measurement system can’t satisfy the metrical requirement well.
Tunable diode laser absorption spectroscopy (TDLAS) analytic measurement technology can well satisfy the measurement in the harsh environment, which can support the whole measurement plan and high quality measurement system. Because the TDLAS sensor has the excellence of small bulk, light weight, high reliability and well specifically measurement, the TDLAS measurement technology has wide prospects.
Different from most measurements, only a beam of laser can be pass through the measured environment by TDLAS, and the measurement equipment needn’t be set in the harsh environment. So, the TDLAS equipment can’t be interrupted by the measured equipment. The ability of subsistence in the harsh environment is very valuable, especially in the measurement on the subject of aerospace with environment of high speed, combustion and plasma. This paper focuses on the collecting the articles on the subject of oxygen detection of TDLAS. By analyzing the research and results of the articles, we conclude the central issues, difficulties and results. And we can get some instructive conclusions.
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