ZHAO Hui, BAO Ge-tang, TAO Wei. Experimental research and analysis of automatic focusing function for imaging measurement[J]. Editorial Office of Optics and Precision Engineering, 2004,(5): 531-536
ZHAO Hui, BAO Ge-tang, TAO Wei. Experimental research and analysis of automatic focusing function for imaging measurement[J]. Editorial Office of Optics and Precision Engineering, 2004,(5): 531-536DOI:
Experimental research and analysis of automatic focusing function for imaging measurement
Several general automatic focusing functions for imaging measurement are put forward
compared and analyzed in defail. The main parameters of automatic focusing
including sensitivity
consistency
stability and calculating speed
were tested and validated through a series of experiments under different conditions
such as different lighting or different background. The results of experiments show that in the background lighting
the gray functions all have better performance than others
the Variance function and the sum of gray-change function have a large focusing range
good linearity and low sensitivity
so they are propitious to focusing in large range with lower accuracy. The Laplacian and Tenengrad functions both have sharp peak
good sensitivity and small focusing range
which make them applicable to accurate focusing in small range. But in reflection lighting
only the Tenengrad and Brenner functions have fine single peak and low sensitivity. All of these focusing functions will be disabled when the complex backgrounds exist. So
when it comes to practical application
background lighting should be chosen instead of reflection lighting
also interference coming from background should be reduced to minimum level.
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references
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