Accurate measurements of modulation transfer functions (MTFs) of image displays are often necessary for objective quality assessments but are difficult to carry out due to the need for specialized apparatus. In this work, the modulation transfer function of a cathode ray tube (CRT) device is determined by using a monochrome still digital camera of medium resolution. Firstly, a number of computer generated sine wave images of discrete spatial frequencies and constant modulation are displayed and photographed from a close distance. Fourier techniques are employed to extract the amplitude of the display signal form the resulting noisy macroimages. Secondly, measurements are carried out by displaying artificial step-edges and applying the ISO 12233 Slanted-edge Spatial Frequency Response plug-in for automatic edge analysis. The display MTF, in both cases, is extracted from the closed-loop system MTF. The standard test conditions are described, results are compared and advantages and limitations of this approach are discussed.
展开▼
