Fluctuations in the intensity read out of CCD/CMOS arrays in digital holographic setups: An experimental investigation

In modern optical systems discrete digital devices for measuring intensity distributions play an indispensible role. The intensity incident on the CCD or CMOS array is averaged over the spatial extent of each pixel for a given exposure time. Fluctuations in the power of a laser, vibrations on an optical table, and electronic noise from the digital sensor all contribute to some degree to a base-line noise level for a particular optical system. Hence we expect that the intensity value measured by each pixel will fluctuate over time. In this paper we investigate the effects of noise of cameras over time using a speckle field for a range of different camera parameters such as exposure time, gain factor, and light power. We then examine how this baseline noise level changes when the incident speckle field is mixed with a plane reference wave forming to form a hologram at the camera plane. We comment on our experimental results and how they apply to general optical systems that measure the phase distribution for a complex field.