Abstract: A charged particle evaluation system that may include a column that includes an opening; an illumination unit that is configured to scan an area of a sample with an electron beam that passes through the opening; and an optical auto-focus unit that is configured to (i) illuminate the sample with an optical beam that is proximate to the electron beam, during the scan of the area with the electron beam; (ii) receive a reflected optical beam from the sample, (iii) determine a focus status of the electron beam, and (iv) participate in a compensating of an electron beam misfocus.

Abstract: A spatial beam shaper structure and a corresponding optical system are provided. The spatial beam shaper structure comprises a light collecting surface configured for affecting light impinging thereon to provide a substantially smooth light profile of at least one optical property, the light collecting surface having a pattern in the form of multiple surface regions comprising regions of at least two different optical properties arranged in an alternating fashion, wherein an interface region between each two locally adjacent regions of the different optical properties has the at least two different optical properties, to provide substantially smooth transition of said different optical properties within the interface region.

Abstract: A spatial beam shaper structure and a corresponding optical system are provided. The spatial beam shaper structure comprises a light collecting surface configured for affecting light impinging thereon to provide a substantially smooth light profile of at least one optical property, the light collecting surface having a pattern in the form of multiple surface regions comprising regions of at least two different optical properties arranged in an alternating fashion, wherein an interface region between each two locally adjacent regions of the different optical properties has the at least two different optical properties, to provide substantially smooth transition of said different optical properties within the interface region.