Methods and apparatus to facilitate the measurement of the amount of scattered electrons collected by an anti-fogging baffle arrangement are provided. For some embodiments, by affixing a lead to an electrically isolated (floating) portion of the baffle arrangement, the amount of scattered electrons collected thereby may be read out, for example, as a current signal. Thus, for such embodiments, the baffle arrangement may double as a detector, allowing an image of surface (e.g., a mask or substrate surface) to be generated.