PROCEEDINGS ARTICLE | February 20, 2017
Proc. SPIE. 10110, Photonic Instrumentation Engineering IV
KEYWORDS: Photonic devices, Optical filters, Holograms, Holography, 3D image reconstruction, Digital holography, Image processing, Digital filtering, Particles, CCD cameras, Optical tracking, Charge-coupled devices, Double sideband modulation
Nowadays, digital holographic systems are based on two main optical schemes: off-axis (OA) and inline (IL) holographic systems. In OA set-ups, the reference and the object beams present a relative angle at the registration plane. Thus, a real image of the object can be obtained without the influence of conjugated images by performing a spatial filtering at the reconstructed plane. IL configurations are less sensitive to vibrations and air flows than OA configurations, but the undesired influence of conjugated images in the final hologram is not avoided. To overcome this limitation, a number of IL based methods have been proposed. One interesting approach is the phase-shifting technique, which leads to efficient holograms for IL applications. However, due to the time-sequential nature of this technique, it is somewhat inappropriate for dynamic processes. We present a new method, for IL digital holography, based on a doublesideband (DSB) filter. This method not only removes the conjugate images in the reconstruction process but also reduces the distortions that usually appear when using single-sideband filters. Moreover, it is only time-limited by the acquisition time of the CCD camera. The appropriateness of the technique to be applied in dynamic processes was tested for the tracking of micro-particles. To this aim, particle holographic images were obtained by using the DSB method and afterwards processed with digital picture recognition methods, this allowing us to accurately track the spatial position of the particles. By using this approach, the instantaneous trajectory and velocity described by glass microspheres in movement were experimentally determined
