During the on-line measurement of the tolerance of glass thickness with laser refraction method

how to achieve the accurate orientation in the abominable environment（with a temperature higher than 650 ℃） is the key of the apparatus design because of the large difference between actual circumstance and standard laboratory circumstance.CCD image spots position subdivision method is to utilize the high relativity of gray degree value between the image elements for object image spots

and construct mathematics model that reflects precisely the object area image elements gray degree value

position and centroid location of object image spots as possible

so the accurate estimation of spot object images spots location.These methods have been analyzed and deduced

and each applicable field and characteristic detected experimentally and compared.