Figure 2: Estimation of resolution by USAF chart. Various sized white bars are spaced in a line at regular intervals equivalent to the width of a bar. The chart is consisted from 6 “Groups” and each group has 6 “Elements” which have thee vertical and horizontal bars. Size of bars gradually shrinks from Group 2, Element 2 to Group 5 Element 6 in this figure. Figure 2a shows an image obtained using a general ENT video endoscope, Figure 2c shows and image obtained using theVNL-1590 STi, Figure 2b and 2d show observation inside the frame: Group 3, Element 4 to 6. Compared to the conventional video endoscope, the VNL-1590 STi more clearly depicts these bars. Figure 2e (dotted frame) and 2f (dotted oval frame) are images of Group 4 and 5, respectively, on the USAF chart. The VNL-1590 STi can distinguish between 32 (line width = 16 μm) and 36 (line width = 14 μm) vertical line within 1 mm (Group 5, Element 1 and 2) and horizontal line pars of 22.62 (22 μm; Group 4, Element 4).