Off-axis Digital Holograms Research Articles

Transmission digital holographic microscopy based on a beam-splitter cube interferometer

A new optical configuration for digital holographic microscopy is presented. Digital off-axis holograms are recorded by use of a single cube beam splitter in a nonconventional configuration to both split and combine a diverging spherical wavefront as it emerges from a single point source. Both the amplitude and the phase can then be reconstructed, yielding intensity and phase images with improved resolution. The novelty of the proposed configuration is its simplicity, minimal number of optical elements, insensitivity to vibration, and its inherent capability to compensate for the phase curvature that results from the illuminating wavefront in the case of microscopic samples.

Digital holographic microscopy with physical phase compensation

An optical configuration for digital holographic microscopy is presented. Digital off-axis holograms are recorded by using a single-cube beam splitter in a nonconventional configuration so as to both split and combine a diverging spherical wavefront emerging from a microscope objective. When a plane numerical reference wavefront is used for the reconstruction of the recorded digital hologram, the phase curvature introduced by the microscope objective together with the illuminating wave to the object wave can be physically compensated.

Numerical reconstruction and twin-image suppression using an off-axis Fresnel digital hologram

In this work we proposed a novel approach for the numerical reconstruction of digital holography that uses only an off-axis Fresnel digital hologram and can easily be carrying out in a personal computer. From the presented off-axis holographic principle, the reference wave accompanies to the numerically reconstructed image, also makes the separation to the zero-order and twin images. Therefore, the concept can be applied to suppress the blurring of numerical reconstruction by adding the extra reconstruction plane and the formularized numerically reference wave in the reconstruction procedure. As expected, the blurring images can be separated out and removed from the reconstructed image. Then, by performing the back propagating to the exact reconstruction plane, one can obtain the pure object image without the blurring. In contrast to the temporal phase-shifting digital holographic-based scheme that employs multiple exposures the technique can be more effectively and easily overcome the blurring problem, also provide the practical feasibility in the digital holographic application.

Recovering image resolution in reconstructing digital off-axis holograms by Fresnel-transform method

The resolution of amplitude and phase reconstruction of images from digital holograms by the Fresnel transformation method is limited by the pixel width in the reconstructed image plane. The reconstruction pixel depends on distance, wavelength, and number of pixels in the hologram. The spatial frequencies, in the reconstructed image, are band limited by the size of the reconstruction pixel. Undersampling can occur, in the image plane, in the reconstructed amplitude and/or wrapped phase maps. Recovery of reconstructed undersampled spatial frequencies, is possible by the fictitious enlargement of the digital hologram. Correct profile reconstruction of a silicon microelectromechanical structure is demonstrated, applying the proposed method.