AUTOMATIC DENSITY CORRECTION METHOD FOR READING FILM FOR RADIO GRAPHIC TEST

摘要

PURPOSE:To use all gradation number effectively by applying A/D conversion to picture density on a film picked up within a predetermined density range into picture data comprising a luminance over nearly all areas of existing gradation number with a predetermined conversion formula. CONSTITUTION:A received film 10 is placed on a transparent lighting base 7 and contrast of each area of a picked-up image 11 on a pickup film 6 is received by a TV camera 1 as analog data. Furthermore, contrast data of film pieces 5a-5m of a film 5 whose density is known are received simultaneously. Then the contrast data of the picked-up image 11 and the film pieces 5a-5m are compared by a controller 2 to obtain a density D along the arrow A. Next, the density D is converted into a luminance value 1 in an A/D converter 3. Then the obtained maximum and minimum luminance values are acquired and a correction parameter is obtained in a computer 4 so that the obtd. luminance values are included within almost the entire area of existing gradation numbers 0-255 and the film density is A/D-converted into a luminance value again from the parameter and picture data are obtained.