西门子恒星图 144组 带OECF测试 分辨率测试卡

Sine wave Spatial Frequency Response (s-SFR) analysis algorithm

    An executable version of software has been developed to perform measurements using this test chart. The software, which was created using Matlab®3), can be accessed from www.iso.org/12233. The software can report the results from a single image, or can average the results from numerous images. The star is divided into a user-selected number of segments (typically 8 segments) for analysis. The user selects the area of the captured image that contains the chart, with the lightest patch in the upper right corner. The result shows the modulation versus frequency (in LP/PH) for each of the segments.

    The Siemens star elements are identified using the marks in the corners and the centre of each star. Then the OECF of the camera is determined using the 16 grey patches of the central star. The image is linearized using the inverse of the OECF.