Digital hologram quality improvement by elimination of imaging sensor noise

摘要

Digital holography allows displaying of shape and parameters of 2D-objects and 3D-scenes. This is achieved by interference pattern recording using imaging sensors (CCD, CMOS, and etc.) and it's further processing. In result amplitude and phase of the investigated object can be obtained. Cross-sections of registered scene or full 3D-image can be reconstructed numerically (using computer) or optically (using spatial light modulators). There are several restrictions on quality of images reconstructed from the digital holograms: speckle noise, twin image and zero order, camera's sensor temporal noise (especially shot noise) and fixed pattern noise (especially photo response non-uniformity). The most popular methods of improvement of hologram quality are based on digital filtering techniques. In spite of quality increasing, several parameters (such as resolution or contrast) of the reconstructed images are usually a little or significantly worsened. In this work temporal and spatial noises of the sensor are accurately eliminated without digital hologram resolution worsening. Also effect of camera's noise on reconstructed images is investigated. Characteristics of cameras of different types were used. Numerical experiments were conducted using standard parameters of holographic recording setups in visible optical spectrum (532 nm). Quality of reconstructed images was estimated by the signal-to-noise ratio values. Images reconstructed from digital holograms with various temporal and fixed pattern noise values are shown. Results of improvement of quality of the digital holograms by camera's noise elimination are presented.