Apparatus and method for providing sensor data of an optical system, optical system and lithography apparatus having an optical system

A design method for designing an apparatus comprising an analogue-to-digital converter for converting analogue sensor signals into digital sensor signals and a digital filter device, connected downstream of the analogue-to-digital converter, for filtering the digital sensor signals, which include a used signal component with used signal frequencies of a used signal bandwidth and an interference signal component with at least one determinable alias frequency of a known interference frequency undersampled by the analogue-to-digital converter in the analogue sensor signal, the design method comprising:

• a) selecting the sampling frequency of the analogue-to-digital converter so that the at least one alias frequency lies outside the used signal bandwidth and the sampling frequency is not a submultiple of the interference frequency;
• and
• b) selecting the sampling frequency of the analogue-to-digital converter and the filter order of the digital filter device with low-pass behaviour in such a way that the digital filter device allows the signal components within the used signal bandwidth to pass and suppresses the at least one aliasing frequency of the undersampled interference signal components.

An apparatus, comprising:

• an analogue-to-digital converter configured to convert analogue sensor signals into digital sensor signals;
• a digital filter device connected downstream of the analogue-to-digital converter, the digital filter device having low-pass behaviour to filtering the digital sensor signals which include a used signal component with used signal frequencies of a used signal bandwidth and an interference signal component with at least one determinable alias frequency of a known interference frequency undersampled by the analogue-to-digital converter in the analogue sensor signal,
• wherein the sampling frequency of the analogue-to-digital converter and the filter order of the digital filter device are configured so that the at least one alias frequency lies outside the used signal bandwidth and the sampling frequency is not a submultiple of the interference frequency and so that the digital filter device allows the signal components within the used signal bandwidth to pass and suppresses the at least one alias frequency of the undersampled interference signal components.