In the corners of each Siemens star are three/four patches (number of patches depends on the test target) with a small white square inside a bigger black square which is used to detect the position of the Siemens star. A central marc helps to get the focus right and to fine tune the detection of the center. The test targets containig sinusoidal Siemens stars use only structures which lead to constant measurement results independent of the target position relative to the sensor.Įach star of a test target is surrounded by 16 gray patches, which are used to linearize the image prior to the analysis. The method provides information about the resolution at different positions in the image, it is stable and leads to reliable results especially concerning sharpening and compression algorithms as sinusoidal structures avoid high contrast and sharp edges. Actually the method requires only a single image to capture all the necessary data, multiple images can be used to reach a higher level of accuracy. We have been using this method succesfully for years now for several applications like photography, video, automotive, machine vision and others. The resolution measurement with sinusoidal Siemens stars is applicable to all digital cameras and done within minutes.
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