| 摘要 |
An apparatus for providing a light beam for use in a diffraction instrument (1) includes a device (10; 17; 28) for generating a light beam; and means (12, 21; 24) for shaping the light beam generated by the device (10; 17; 28), dimensioned, in use, to determine the beam shape, and including: an aperture (21; 25) and means (13; 24) for rejecting spatial frequency components above a certain range in the light beam. The apparatus further includes a spatial low-pass filter (14; 15; 26; 27) arranged to filter a beam provided by the beam shaping means. |
