| 摘要 |
PURPOSE:To make it possible to perform MTF calculation of high precision by regarding as the maximum and minimum values of white and black level regions the mean values of signals, obtained as many as a fixed number, from the fixed number on signals of the white and black level regions. CONSTITUTION:A time series of signals from CCD, classified by a threshold level into white-level and black-level regions, is digitized by A/D converter 28 and then stored in RAM30 via input-output port 29. On the basis of the value of RAM30, micro CPU31 performs digital calculation to find mean value (a) of a signal of a few maximum bits of the white level region and mean value (b) of a few approximate minimum bits of the black level region. From the right equation, MTF is calculated, which is carried out by micro CPU31. Here, (a) and (b) stand for the white level and black level of a needed chart, and A and B are a white level and black level close to a zero space frequency. Then, (a), (b), A and B are detected as many as several bits and respective mean values are substituted in the right equation, so that the calculation precision of MTF will further improve. |
