| We describe a method to measure MTF using Fourier analysis with a square wave chart. This method has the advantage of being able to easily and accurately measure MTF without Coltman's formula by computing the Fourier spectrum of the fundamental frequency of each square chart. It took just 8 sec to automatically obtain measurements of MTF using the square wave chart. To evaluate the usefulness of this method, the contrast method was used to confirm its accuracy and reproducibility using computer-simulated data. MTF data for each sample were measured five times by 10 persons. We analyzed the accuracy and reproducibility of these two methods by using known MTF data with white noise. Our results demonstrated that error for the contrast method was psychologically affected by much noise and unfavorable MTF. The contrast method showed that the MTF obtained from data in which the error was more than 0.01 between the real and measured value was less than 0.2. However, MTF was less than 0.02 with our method. There was a difference between the two methods in terms of accuracy. Because of its superior accuracy and shorter measuring time, we consider our method better for determining MTF than the contrast method. |
