Abstract
Problems, related to hard copying still image in the electronic endoscopes, are studied. An original chart is made while quantitatively comparing and studying an image obtained by phtographing the monitor and another image gained by inputting digital signal directly into the memory, in terms of resolution. The chart, consisting of 1, 1.5 and 3 lines in a colum of 1 mm width in vertical and horizontal directions, was made with an image analyzer. Six type of charts were printed out using a 35mm camera and pictrograhy 1, 000 (FUJI FILM). These 12 types of images were quantitatively compared and examined. A microdensitometer was used to have a density profile. The microdensitometer has a slit of 25 × 1, 000 μm specially machined. The lines of the created images were scanned by the microdensitometer in the arrow direction. The output wavef orms were recorded while defining their amplitudes with a A. Amplitude A0 was defined for the scanning with the lines of 1 line/mm. A variable CTF (contrast transfer function) was defined by normalizing A by A0 and used as an index of resolution. Resolution for a pitch of 1 line/ mm in both digital and still images were defined as 100%. Then the resolution of the digital screen in 3lines/mm was superior, 93.2% and 76% in horizontal and vertical directions, respectively. Conventionally used still image of a monitor screen was inferior to digital image in terms of resolution among hard copies of still images the electronic endoscopes. In order to make use of features of the electronic endoscopes, we have to introduce into the digital systems.
