Self-adjustment of spectral components to object wave field extraction in off-axis digital holography.

In this paper, we introduce a positioning system to self-adjust the spectral components of holograms recorded by an off-axis digital holography setup. The incidence angle of the reference arm is carried out by two motorized actuators controlled by an algorithm that automatically adjusts it to avoid the overlapping of the spectral components. The right positioning of the spectral components allows selection of a spectral region to extract only the virtual component so that, after an inverse Fourier transformation, the object wave field can be obtained, thus eliminating the undesired components and increasing the image quality of the reconstructed image.

Object wave field extraction in off-axis holography by clipping its frequency components.

Suitable extraction of an object's wave field in an off-axis digital holographic array is the core for any numerical reconstruction process. In this manuscript, we propose an algorithm that reduces the number of pixels needed for an object's wave field trimming, reducing notably its processing time without significant changes in the quality of the reconstructed image. Our method generates an extraction window containing a complete object's wave field. The energy that the generated extraction window must contain is analyzed, defined, and used as a reference value. Our proposal reduces significantly the number of operations and execution time for holographic reconstruction.

Using an aliasing operator and a single discrete Fourier transform to down-sample the Fresnel transform.

In Digital Holography there are applications where computing a few samples of a wavefield is sufficient to retrieve an image of the region of interest. In such cases, the sampling rate achieved by the direct and the spectral methods of the discrete Fresnel transform could be excessive. A few algorithmic methods have been proposed to numerically compute samples of propagated wavefields while allowing down-sampling control. Nevertheless, all of them require the computation of at least two 2D discrete Fourier transforms which increases the computational load. Here, we propose the use of an aliasing operator and a single discrete Fourier transform to achieve an efficient method to down-sample the wavefields obtained by the Fresnel transform.