Abstract：To achieve the ultra-low rotating speed online measurement, a geometric center of gravity subpixel extraction algorithm based on microscopic image was proposed.Firstly, the measurement of ultra-low rotation speed was transformed into translational measurement according to the microscopic image method,the surface fitting method and gradient method which are commonly used at presentnot only take longer to extract sub-pixel but also have weak anti interference ability, thesub-pixel extraction algorithm of the geometric center of gravity method solved these problems.The core of the geometric center of gravity method was to calculate the index value of the difference between the reference pixel gray value and the integer pixel gray value within the range of 3×3 pixel on the basis of the integer pixel extraction, then extracted the sub-pixel value from the acquired 3-point index value by using the geometric center of gravity method.Through the verification of micro-displacement captured images by grating reference platform, the average time of geometric center of gravity method was less than 0.2s, which was shorter than the surface fitting method and the gradient method.The standard deviation of the extract subpixel value was less than one thousandth of a pixel, which conformed to the basic requirements of ultra-low rotating speed online measurement.
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2020, Vol. 41 
