%0 Journal Article %A Koh, Kwang Uoong %A Kim, Joo Youn %A Lee, Sang Yong %D 2001 %I Begell House %N 4 %P 317-333 %R 10.1615/AtomizSpr.v11.i4.20 %T DETERMINATION OF IN-FOCUS CRITERIA AND DEPTH OF FIELD IN IMAGE PROCESSING OF SPRAY PARTICLES %U https://www.dl.begellhouse.com/journals/6a7c7e10642258cc,207922417517f7a9,0bbcd78675f984e9.html %V 11 %X In the present study, in-focus criteria and depth of field in image processing of spray particles within the size range 10–300 mm have been examined. As the indices of the in-focus criteria, the critical normalized value of contrast (VCcritical) proposed earlier was carefully reviewed, and the concept of the critical gradient indicator (GIcritical) was newly introduced. The criterion with VCcritical) was confirmed to be appropriate only for the small particle range (Ј 30 mm). In contrast, the criterion with GIcritical was determined to be appropriate for large particles і 30 mm). The dependence of the depth of field on the values of VCcritical and GIcritical was examined. The depth of field decreases with higher values of VCcritical and GIcritical , and varies linearly with particle size in both VC- and GI-applicable ranges. To keep the normalized standard deviation of the measurements below 0.1 while maintaining the continuity of the depth-of-field variation at the borderline of 30 mm, the adjustable constants C and DGI for VCcritical and GIcritical should be set to 0.85 and 0.22, respectively, for the present optical setup. %8 2001-08-01