The mechanism of Abbe error and cosine error resulting from beam pointing and positional errors in a laser interference measurement system was analyzed, a PSD-based measurement method was proposed to measure both errors simultaneously. A light intensity adaptive measuring device was designed for measurement of pointing and positional errors. Experimental results indicated that the measuring range and resolution of the position deviation could reach ±4.5mm and 1μm respectively; the angular range and resolution could reach ±0.112rad and 25μrad.
Modified gamma distribution was used to describe the distribution of particles in clouds. The polydisperse particle
system may be converted into a monodisperse particle system. 1) The averaged radius of nonspherical particles
associated with a given size distribution, 2) the averaged scattering parameters of water droplets in cumulus, stratus and
stratocumulus and that of ice crystals in cirrus, and 3) infrared emissivity of a cirrus layer from the mixing ratios and
effective sizes of cloud drop and ice crystal were separately calculated. Simulation results indicate that all scattering
parameters of water droplets in cumulus, stratus and stratocumulus are similar. Cross sections increase with the
increasing equivalent radius. While efficiency factors vibrate with the increase of equivalent radius. The averaged albedo
reaches its peak between 2 and 3 micron, and then decrease with the increasing equivalent radius. The averaged
asymmetry factor also vibrates with the increase of equivalent radius. But the scattering parameters of ice crystals in
cirrus change differently, and they vary linearly with equivalent radius.
It is known from relationship between brightness temperature and true temperature of a multi-spectral thermometer that
brightness temperature is equal to true temperature if the wavelength approaches to zero. Thus true temperature can be
acquired by fitting brightness temperatures and corresponding wavelengths using non-linear least squares method. This
method was named AMBT (approach method based on brightness temperature). The emissivities of metals and nonmetals
were used to simulate AMBT at a temperature from 160K to 3000K. The effective wavelengths chosen are 3.00,
3.25, 3.50, 3.75, 4.00, 4.25, 4.50 and 4.75 micron in the atmospheric window of 3-5 micron. While in another
atmospheric window of 8-12 micron, the effective wavelengths are 8.00, 8.50, 9.00, 9.50, 10.00, 10.50, 11.00 and 11.50
micron. Actual measurements were used to verify the effectiveness of AMBT. Results show that the errors are always
smaller at a lower temperature and increase with the increase in temperature. The errors of 3-5 micron are lower than
those of 8-12 micron. At same temperature, the errors of metals are lower than those of non-metals. AMBT is more
accurate to be used at a low temperature than be used at a high temperature. AMBT can be used to identify materials in
common use, offering a new method to get true temperature of low temperature objects.ï
A general computing formula has been formulated for the measurement of surface temperature and the corresponding
relation between the thermal value and the true temperature of infrared images according to the principles of thermal
radiation and temperature measurement with infrared thermal imager. A least squares method and an improved neuralnetwork
method have been developed to calculate the temperature to diminish the deviation of neural-network method.
The above two methods use the ratios among the three basic colors output from the thermal infrared imager as the
independent variable or input variable, and can personalize the colorimetric temperature-measurement algorithm, so that
the influence of emissivity, soot and combustion flame on the temperature result can be reduced. Simulation results show
that the precision of these two methods are higher than that of the traditional neural network method. In addition, the
precision of the proposed neural-network method is higher than that of the least squares method.