Aberration compensation using a spatial light modulator LCD

Author(s): R. Amézquita, O. Rincón and Y. M. Torres

Abstract:

“The dynamic correction of aberrations introduced in optical systems have been a widely discussed topic in the past 10 years. Adaptive optics is the most important developed field where the Shack-Hartmann sensors and deformable mirrors are used for the measurement and correction of wavefronts. In this paper, an interferometric set-up which uses a Spatial Light Modulator (SLM) as an active element is proposed. Using this SLM a procedure for the compensation of all phase aberrations present in the experimental setup is shown.”

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Publication: Journal of Physics: Conference Series
Issue/Year: J. Phys.: Conf. Ser. 274 012111 (2011)
DOI: 10.1088/1742-6596/274/1/012111

Rapid calculation algorithm of Fresnel computer-generated-hologram using look-up table and wavefront-recording plane methods for three-dimensional display

Author(s): Tomoyoshi Shimobaba, Hirotaka Nakayama, Nobuyuki Masuda, and Tomoyoshi Ito

Abstract:

“A rapid calculation method of Fresnel computer-generatedhologram (CGH) using look-up table and wavefront-recording plane (WRP) methods toward three-dimensional (3D) display is presented. The method consists of two steps: the first step is the calculation of a WRP that is placed between a 3D object and a CGH. In the second step, we obtain an amplitude-type or phase-type CGH to execute diffraction calculation from the WRP to the CGH. The first step of the previous WRP method was difficult to calculate in real-time due to the calculation cost. In this paper, in order to obtain greater acceleration, we apply a look-up table method to the first step. In addition, we use a graphics processing unit in the second step. The total computational complexity is dramatically reduced in comparison with conventional CGH calculations. We show optical reconstructions from a 2,048×2,048 phase-type CGH generated by about 3×104 object points over 10 frames per second.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 18, Issue 19, pp. 19504-19509 (2010)
DOI: 10.1364/OE.18.019504

Optical reconstruction of digital holograms recorded at 10.6 μm: route for 3D imaging at long infrared

Author(s): Melania Paturzo, Anna Pelagotti, Andrea Finizio, Lisa Miccio, Massimiliano Locatelli, Andrea Gertrude, Pasquale Poggi, Riccardo Meucci, Pietro Ferraro

Abstract:

“We demonstrate the optical reconstruction in the visible range (0.532μm) of digital holograms recorded at long IR wavelengths (10.6μm) by means of a spatial light modulator. By using an integrated recording-reconstruction system, it is, in fact, feasible to achieve direct imaging of holograms acquired outside the visible range, i.e., in the IR spectrum. By choosing a Fourier recording configuration, the reconstructed image, obtained at about a 20 times shorter wavelength than the acquisition image, exhibits minor aberrations, which do not significantly affect the optical reconstruction. The high NA achievable at a long IR wavelength allows us to image large objects at reasonable distances.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 35, Issue 12, pp. 2112-2114 (2010)
DOI: 10.1364/OL.35.002112

Implementation of a digital optical phase conjugation system and its application to study the robustness of turbidity suppression by phase conjugation

Author(s): Meng Cui, Changhuei Yang

Abstract:

“In this work, we report a novel high capacity (number of degrees of freedom) open loop adaptive optics method, termed digital optical phase conjugation (DOPC), which provides a robust optoelectronic optical phase conjugation (OPC) solution. We showed that our prototype can phase conjugate light fields with ~3.9 x 10−3 degree accuracy over a range of ~3 degrees and can phase conjugate an input field through a relatively thick turbid medium (μsl ~13). Furthermore, we employed this system to show that the reversing of random scattering in turbid media by phase conjugation is surprisingly robust and accommodating of phase errors. An OPC wavefront with significant spatial phase errors (error uniformly distributed from – π/2 to π/2) can nevertheless allow OPC reconstruction through a scattering medium with ~40% of the efficiency achieved with phase error free OPC.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 18, Issue 4, pp. 3444-3455 (2010)
DOI: 10.1364/OE.18.003444

Refining common path interferometry with a spiral phase Fourier filter

Author(s): Christian Maurer , Stefan Bernet, Monika Ritsch-Marte

Abstract:

“Recently, spiral phase filtering for isotropic edge enhancement and for optical thickness measurements of phase samples has been implemented in microscopy, using gray value images on a spatial light modulator (SLM) placed in a Fourier plane of the sample. In a common path interferometer, the light going through the central part of the helical phase hologram is overlapped with the light passing through the periphery of the phase filter. Replacing the center by a disk of uniform phase leads to pseudo-relief images, with the apparent illumination direction depending on the gray level of the central area. If one uses such images to reconstruct the optical thickness of phase objects, the reference wave through the central part ideally should have a plane wavefront. This is normally not the case, especially when the imaging setup requires a relatively large central area around the DC Fourier component. This paper shows how a direct measurement of the amplitude of the reference beam, which can be done in the given setup by simply changing the image on the SLM, can increase the accuracy of phase measurement, allowing one to determine the refractive index with a relative error below 0.6%.”

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Publication: Journal of Optics A
Issue/Year: J. Opt. A: Pure Appl. Opt. (2009) 11 094023
DOI: 10.1088/1464-4258/11/9/094023

A novel three-dimensional holographic display system based on LC-R2500 spatial light modulatora

Author(s): Huadong Zheng, Yingjie Yu, Cuixia Dai

Abstract:

“A novel holographic display system is proposed in this paper. The system takes LC-R2500, a kind of reflective liquid crystal spatial light modulator, (LC-SLM) as the core display unit, which can meet the requirement of real-time reconstruction of three-dimensional (3D) objects from holograms in free space. The relationship between hologram recording and image reconstruction is discussed, and the parameters associated with the magnification of reconstructed image over original object are determined. Experimental results of holographic display using the system are also given in the end.”

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Publication: Optik – International Journal for Light and Electron Optics
Issue/Year: Optik – International Journal for Light and Electron Optics, Volume 120, Issue 9, May 2009, Pages 431-436
DOI: 10.1016/j.ijleo.2007.11.002

Color holographic reconstruction using multiple SLMs and LED illumination

Author(s): Fahri Yaras and Levent Onural

Abstract:

“A color holographic reconstruction technique by using three light emitting diodes (LEDs) is described. Reflective type phase-only spatial light modulators (SLMs) are used since they are suitable for in-line phase holograms. Gerchberg-Saxton iterative algorithm is used for computing phase holograms. Three phase holograms are calculated separately for red, green and blue colors, for a color reconstruction, and separately loaded to corresponding SLMs. Three LEDs are used for illuminating those phase holograms and reconstructions are combined and captured. Experimental results are satisfactory. ”

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Publication: SPIE Proceedings
Issue/Year: Proc. SPIE, Vol. 7237, 72370O (2009);
DOI: 10.1117/12.806875

Applications of LCoS-based adaptive optical elements in microscopy

Author(s): Andreas Hermerschmidt, Jan Haffner, Tobias Haist, Wolfgang Osten

Abstract:

“Liquid crystal on silicon (LCoS)-based spatial light modulators (SLMs) are versatile adaptive optical elements. In microscopy, among their applications are aberration sensing and correction in wide-field microscopy and also the implementation of holographic optical tweezers. For aberration correction, the required scene-based wavefront sensing can be implemented as a modified correlation-based Shack-Hartmann approach where a high-resolution SLM first senses and then corrects the aberrations. For the implementation of holographic optical tweezers, the SLM serves as a variable optical beam-splitter which is addressed with holograms computed by fast algorithms implemented on the graphics processing unit (GPU) of a common PC almost in real-time.”

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Publication: Proceedings IEEE/LEOS Internationall Conference on Optical MEMs and Nanophotonics
Issue/Year: Proceedings IEEE/LEOS Internationall Conference on Optical MEMs and Nanophotonics, 2008,
DOI: 10.1109/OMEMS.2008.4607842

Structured illumination in total internal reflection fluorescence microscopy using a spatial light modulator

Author(s): Reto Fiolka, Markus Beck, and Andreas Stemmer

Abstract:

“In wide-field fluorescence microscopy, illuminating the specimen with evanescent standing waves increases lateral resolution more than twofold. We report a versatile setup for standing-wave illumination in total internal reflection fluorescence microscopy. An adjustable diffraction grating written on a phase-only spatial light modulator controls the illumination field. Selecting appropriate diffraction orders and displaying a sheared (tilted) diffraction grating allows one to tune the penetration depth in very fine steps. The setup achieves 91 nm lateral resolution for green emission.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 33, Issue 14, pp. 1629-1631
DOI: 10.1364/OL.33.001629

Improved micro topography measurement by LCoS-based fringe projection and z-stitching

Author(s): X. Schwab, C. Kohler, K. Körner, N. Eichhorn, W. Osten

Abstract:

“Fringe projection is a commonly used method for 3D surface metrology. Numerous applications have demonstrated a measurement field from a few millimeters to several meters. To enable the measurement of micro systems with this method, a zoom stereo microscope from Leica was used as the basis for the implementation of a fringe projection microscope. A state of the art twisted nematic WUXGA LCD was used for flexible fringe generation. The high fill factor of this reflective LCoS in combination with a 500 Lumen LED and a 12 bit CCD camera delivers fringe patterns with high contrast. This allows us to measure objects with both a strong reflectivity variation and a low reflectivity. The second main objective was to increase the measurement field and the depth of field. Using the zoom system and exchangeable microscope objectives, the measurement fields could be changed quickly from 4 cm² to less than 1 mm². Depending on the measurement field, the depth of field was between 5.22 mm and 0.018 mm. However, this was often not sufficient to measure the complete depth of a 3D-object. The microscope system also features an integrated high precision motor stage, which is already used for system calibration. Based on this, we implemented a new z-stitching method where n measurements at different well determined z-positions of the motor stage were performed. The n resulting topography maps can be stitched together to get the complete depth map of the entire object. Thus the depth measurement range is only limited by the mechanics of the z-stage. ”

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Publication: SPIE Proceedings
Issue/Year: Proc. SPIE, Vol. 6995, 69950Q (2008);
DOI: 10.1117/12.781822