A metrology system, an inspection method, and a lithography apparatus are provided. The metrology system includes a radiation source, an optical system, an optical element, a detector, and a processor. The radiation source generates a radiation beam. The optical system is configured to direct the radiation beam toward a target structure, and receive a first scattered beam and a second scattered beam of radiation from the target structure. The first scattered beam comprises a first non-zero diffraction order and the second scattered beam comprises a second non-zero diffraction order that is different from the first non-zero diffraction order. The optical element attenuates one of the first scattered beam or the second scattered beam. The detector generates a detection signal. The processor analyzes the detection signal to determine a property of the target structure based on at least the detection signal.
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