Wavefront reconstruction by adding modulation capabilities of two liquid crystal devices

Tudela, R.

doi:10.1117/1.1803551

Cited by 22 publications

(9 citation statements)

References 11 publications

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“…In this case, a key problem is the alignment of the SLMs because the optical fields displayed separately on two different devices should match perfectly when they are combined. In practice, it was reported than an error as small as one pixel was already inducing significant errors 13 . In this study, we examine the effects of mismatch in the reconstruction distance in a complex modulation system based on two SLMs in additive configuration.…”

Section: Introductionmentioning

confidence: 99%

Modification of the reconstruction distance of Fresnel holograms for display with multiple spatial light modulators

2016

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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.

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Section: Introductionmentioning

confidence: 99%

Modification of the reconstruction distance of Fresnel holograms for display with multiple spatial light modulators

2016

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“…Therefore it is possible to calculate an optimum phase hologram, with only the real image reconstructed by using spatial filtering 9 and also to control of the position of the reconstruction of the object by adding a linear phase shift to the hologram. We have then the possibility to transfer this hologram to a spatial light modulator (SLM) and to obtain an optical reconstruction of the optimized digital hologram [10][11][12][13][14][15][16] . This opens a new degree of flexibility and practicability for holographic metrology.…”

Section: Introductionmentioning

confidence: 99%

Alignment of master and sample in comparative digital holography

2006

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A comparative digital holography system suitable for shape and deformation comparisons between master and sample objects with rough surfaces is described. The innovative aspect of comparative digital holography is the illumination of the sample by the conjugated wavefront of the master, as a type of coherent mask, using a liquid crystal display (LCD). The resulting interferogram indicates directly the shape or the deformation differences between the master and sample. As it is not necessary that both objects to be compared are located at the same place for this technique, remote shape or deformation comparison between a master and a sample is possible. A current research topic is the precise alignment of the sample and the reconstructed master wavefront so that the resulting phase map only contains information of the differences in shape or deformation. The reconstructed master wavefront can be adjusted digitally to correctly illuminate the sample object, by introducing an artificial phase-shift. This phase-shift is induced by the LCD, and offers also the possibility of calibrating precisely the set-up. The value for the phase-shift is obtained by a comparison of the resulting interferogram with a database containing fringes from simulations of misalignments between master and sample objects. Using the iterative algorithm described here, the correction of the sample position can be controlled by an automatic adaptation of the coherent mask.

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“…Since these fundamental mode fields are separated from each other in space, they could be reconstructed using a pair of low resolution SLMs and a micro lens array (MLA) as illustrated in Fig.2. For the device in Fig.2 we may adjust the gray scale of each pixel of SLMs so that it modulates the amplitude and the phase of illuminating laser beam properly [Neto, et al 1996;Tudela, et al 2004] and reconstruct a conjugate field proportional to above decomposed fundamental mode field within each isolated single-mode waveguide at the right wide end. Due to reciprocity of an optical path the digitally reconstructed conjugate light field within each isolated single-mode waveguide would travel inversely to the left narrow end of the taper, combine and create an optical field proportional to the original incident optical field.…”

Section: Generation Of Laser Probes Via Digital Optical Phase Conjugamentioning

confidence: 99%

Laser Probe 3D Cameras Based on Digital Optical Phase Conjugation

Li¹

2012

Digital Image Processing

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Wavefront reconstruction by adding modulation capabilities of two liquid crystal devices

Cited by 22 publications

References 11 publications

Modification of the reconstruction distance of Fresnel holograms for display with multiple spatial light modulators

Modification of the reconstruction distance of Fresnel holograms for display with multiple spatial light modulators

Alignment of master and sample in comparative digital holography

Laser Probe 3D Cameras Based on Digital Optical Phase Conjugation

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