KEYWORDS: Signal to noise ratio, Modulation transfer functions, Imaging systems, Charge-coupled devices, Spatial frequencies, Image quality, CCD image sensors, Modulation, Data conversion, Data processing
The Modulation Transfer Function (MTF) is a fundamental imaging system design specification and system quality metric often used in remote sensing. The MTF describes the attenuation of sinusoidal waveforms as a function of spatial frequency. Practically, MTF is a metric quantifying the sharpness of the reconstructed image. The Knife-Edge method is becoming widely applied for its advantage of simplified target and accurate computer calculation. Noise in CCD image system is inevitable, thus the SNR becomes a factor influencing the MTF measurement. In this paper, we build relationships between SNR, luminance and MTF. In conclusion, SNR is related with luminance levels linearly. SNR rises with increasing luminance. The higher SNR, the more curves conform to the theoretical MTF.
KEYWORDS: Temperature metrology, Black bodies, Data modeling, Thermometry, Mathematical modeling, Tungsten, Lamps, Transmission electron microscopy, Error analysis, Lithium
Aiming at the problems of temperature measurement and the defects of radiance thermometry theory, one method of spectral-based inferential measurement is proposed, which adopts the Empirical Risk Minimization (ERM) functional model as the temperature measurement model. Then, the radiance thermometry theory and inferential measurement technology are discussed comparatively. Temperatures of some targets, such and tungsten lamp and solar surface, are measured by spectral-based inferential measurement.
KEYWORDS: Calibration, Imaging devices, RGB color model, Camera shutters, Cameras, Measurement devices, Digital cameras, Light sources and illumination, Solids, Lithium
A method of calibration of imaging luminance measuring devices has been studied. By the device-independent color space transformation, the color image by digital camera could be converted to the CIE's absolute color space lab. Then, the calibration model is fitted between ln(L/t) and luminance. At last, luminance image is obtained and the dynamic range of luminance image could be adjusted by shutter speed.
In this paper, the compact spectrometer has been designed and implemented with concave grating. By using the holographic corrected concave grating, the compact spectrometer without movable parts, with a fixed grating and an array detector, could obtain a relative high spectral resolution in a wide spectral range. Then, the spectral resolution has been estimated by the slit function. The spectral resolution (ΔFWHM) is smaller than 5nm from 300nm to 1100nm. It is very suitable for photometry, colorimetry, and radiometry.
A new method, namely the closed-loop pipeline, is proposed for the detection and tracking of point targets in heavy cloudy background. At first, a preprocessing step, i.e., a local contrast threshold is used to remove slowly changing clutter, then the "and logical" pipeline consisting of three frames are used to filter out the noise based on the highly consistency and continuity of the targets in temporal-spatial domain. After the two steps, the sequence is projected into one frame and the trajectory of the target is accumulated in the test pipeline. The target trajectory is detected by cluster analysis and smoothed by finding zero-crossing points; moreover the next searching window is identified by the achieved trajectory segment. So compared with the old open form pipeline, the new structure can predict the tracking window and it is advantageous over the traditional one in terms of searching space, computational complexity and clutter resistance. The experiments show that the proposed method can detect and track dim point targets with arbitrary trajectories accurately, and can also predict the searching windows efficiently.
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