GAIN AND OFFSET ADJUSTMENT METHOD FOR LOGARITHMIC TRANSFORMATION CIRCUIT, LOGARITHMIC TRANSFORMATION CIRCUIT AND RADIOGRAPHIC READER

摘要

PROBLEM TO BE SOLVED: To provide an adjustment method for logarithmic transformation circuit capable of precisely adjusting a gain and an offset and readjusting them in a proper time and to provide a radiographic image reader having satisfactory reproducibility of image quality. SOLUTION: This gain and offset adjustment method for logarithmic transformation circuit adjusts the gain and/or offset of a logarithmic transformation circuit comprising a log amplifier and an adjusting circuit for setting and adjusting the gain and offset so that the inclinations and offset of output in the input of at least two currents to the log amplifier is a fixed value. A first gain Ga is set in the adjustment circuit to determine a first inclination DA from the outputs in the first reference current and the second reference current, a second gain Gb is then set to determine a second inclination DB from the outputs in the first reference current and the second reference currents, and the gain G of the adjustment circuit forming an intended inclination (gain) is determined from DA and BA by repeatedly changing the first and second gains Ga and Gb.