| 摘要 |
The test object 10 for a multi-beam device comprises multiple regions 20, wherein each region 20 comprises multiple fields (Fig. 2, 30); wherein each field (30) comprises multiple sub-fields (Fig. 3); wherein each sub-field comprises multiple patterns structural elements (Fig. 11, 12, 13). A location and number of sub-fields of at least one field (30) correspond to a number of beams in an array of beams of the multiple beam system and to an expected spatial relationship between the beams of the array. By obtaining images of sub-fields of a field of a test object by scanning the sub-fields by an array of beams the bean system may be accessed. This is achieved by at least one spatial or optical characteristic of the array of beams based on the images of the sub-fields.
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