We propose a full-color holographic three-dimensional imaging system that composes a recording stage, a transmission and processing stage and reconstruction stage. In recording stage, color optical scanning holography (OSH) records the complex RGB holograms of an object. In transmission and processing stage, the recorded complex RGB holograms are transmitted to the reconstruction stage after conversion to off-axis RGB holograms. In reconstruction stage, the off-axis RGB holograms are reconstructed optically.
In digital holography, spatial light modulators (SLMs) devices are used to display the holographic patterns. However, modulation is imperfect because SLMs cannot modulate phase and amplitude at the same time. Then undesired terms such as twin image can be observed in the image plane. One solution to remove twin image contribution without physical spatial filter is to perform complex modulation. Phase and amplitude modulation can be performed sequentially with two different SLMs. Similarly, real and imaginary part of hologram can be displayed and combined in an additive configuration through a polarizing beam splitter. In both case, a major problem is the alignment of the two display devices since misalignment as small as one pixel may degrade significantly quality of the reconstruction. For our experiment, we used data computed numerically to obtain separately real and imaginary part of hologram. Then, we focused on additive configuration where two SLMs are displaying real and imaginary part of hologram respectively.
Reconstruction distance of hologram is fixed and distance between SLM and beam splitter should be the same for the two devices. In this paper, we study the effect of having different reconstruction distance for the real and imaginary hologram. We performed simulations and explained the result with the scalar diffraction theory. A method to compensate numerically the reconstruction distance is proposed for on-axis configuration. This method can also be applied to modify reconstruction distance of Fresnel hologram displayed with a single SLM and has potential application in RGB holographic reconstruction
We demonstrate a 3D holographic imaging system that composed 1. Recording stage, 2. Processing and transmission stage and 3 Reconstruction stage. First, we record the hologram of a diffusely reflective object using optical scanning holography without speckle noise as well as twin image and background noises. Second, we convert the hologram into an off-axis horizontal-parallax-only (HPO) hologram. Third, we reconstruct the off-axis HPO hologram using amplitudeonly SLM. To the best of our knowledge, this is the first demonstration that records and displays an HPO hologram of a diffusely reflective object optically.
The optical imaging takes advantage of coherent optics and has promoted the development of visualization of biological
application. Based on the temporal coherence, optical coherence tomography can deliver three-dimensional optical
images with superior resolutions, but the axial and lateral scanning is a time-consuming process. Optical scanning
holography (OSH) is a spatial coherence technique which integrates three-dimensional object into a two-dimensional
hologram through a two-dimensional optical scanning raster. The advantages of high lateral resolution and fast image
acquisition offer it a great potential application in three-dimensional optical imaging, but the prerequisite is the accurate
and practical reconstruction algorithm. Conventional method was first adopted to reconstruct sectional images and
obtained fine results, but some drawbacks restricted its practicality. An optimization method based on 2 l norm obtained
more accurate results than that of the conventional methods, but the intrinsic smooth of 2 l norm blurs the reconstruction
results. In this paper, a hard-threshold based sparse inverse imaging algorithm is proposed to improve the sectional image
reconstruction. The proposed method is characterized by hard-threshold based iterating with shrinkage threshold strategy,
which only involves lightweight vector operations and matrix-vector multiplication. The performance of the proposed
method has been validated by real experiment, which demonstrated great improvement on reconstruction accuracy at
appropriate computational cost.
MATLAB is a widely accepted software tool routinely used in engineering, but not so much in applied optics and especially in acousto-optics. In this talk, we first explore the use of MATLAB to solve some well-known examples in acousto-optics such as Bragg diffraction and Raman-Nath diffraction. After establishing the correctness of the MATLAB approach, we then apply it to investigate image processing using acousto-optics and complete power transfer into the second and third Bragg order.
It is discussed a 3-D pattern recognition technique in which, the holograms of objects is recorded as a form of electric signal and 3-D pattern recognition by digital processing of the holograms is achieved. In this technique, is not necessary to record a series of 2-D images for representation of a 3-D object because the holographic information of the object is utilized.
We describe a novel holographic technique for the recognition of 3D objects. We first briefly review an optical heterodyne scanning technique. We will then discuss the use of the technique to create a hologram of the 3D reference object and show how to use this holographic information for 3D object recognition. Finally, we address the important and practical z-invariance of the system and show that the overall scheme of the system is 3D shift- invariant. Computer simulation will be provided for the classification and confirmation of the idea.
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