| 1. |
- Engström, David, 1976, et al.
(författare)
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Calibration of spatial light modulators suffering from spatially varying phase response
- 2013
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 21:13, s. 16086-16103
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Tidskriftsartikel (refereegranskat)abstract
- We present a method for converting the desired phase values of a hologram to the correct pixel addressing values of a spatial light modulator (SLM), taking into account detailed spatial variations in the phase response of the SLM. In addition to thickness variations in the liquid crystal layerof the SLM, we also show that these variations in phase response can be caused by a non-uniform electric drive scheme in the SLM or by local heating caused by the incident laser beam. We demonstrate that the use of a global look-up table (LUT), even in combination with a spatially varyingscale factor, generally does not yield sufficiently accurate conversion forapplications requiring highly controllable output fields, such as holographicoptical trapping (HOT). We therefore propose a method where the pixeladdressing values are given by a three-dimensional polynomial, with twoof the variables being the (x;y)-positions of the pixels, and the third theirdesired phase values. The coefficients of the polynomial are determined bymeasuring the phase response in 8×8 sub-sections of the SLM surface; thedegree of the polynomial is optimized so that the polynomial expressionnearly replicates the measurement in the measurement points, while stillshowing a good interpolation behavior in between. The polynomial evaluationincreases the total computation time for hologram generation by onlya few percent. Compared to conventional phase conversion methods, for an SLM with varying phase response, we found that the proposed methodincreases the control of the trap intensities in HOT, and efficiently preventsthe appearance of strong unwanted 0th order diffraction that commonlyoccurs in SLM systems.
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| 2. |
- Persson, Martin, 1979, et al.
(författare)
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Computer Generated Holograms Designed to Reduce Intensity Fluctuations During SLM Update
- 2009
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Ingår i: Digital Holography and Three-Dimensional Imaging, OSA Technical Digest (CD). - Washington, D.C. : OSA. - 2162-2701. ; , s. DWC3-
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Konferensbidrag (refereegranskat)abstract
- We have investigated design criteria for calculation of computer generated holograms, aiming to reduce the deterioration of the spot pattern during SLM updates. A modified Gerchberg-Saxton algorithm that efficiently minimizes unwanted intensity fluctuations is introduced.
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| 3. |
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| 4. |
- Persson, Martin, 1979, et al.
(författare)
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Improving spot uniformity in holographic optical tweezers
- 2011
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Ingår i: Optics InfoBase Conference Papers. - Washington, D.C. : OSA. - 2162-2701. - 9781557529091
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Konferensbidrag (refereegranskat)abstract
- We have developed a method for compensating for crosstalk between adjacent pixels in liquid crystal based spatial light modulators. The method decreases the uniformity error of the trap intensities in holographic optical tweezers (HOT) systems.
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| 5. |
- Persson, Martin, 1979, et al.
(författare)
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Minimizing intensity fluctuations in dynamic holographic optical tweezers by restricted phase change
- 2010
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Ingår i: Optics Express. - 1094-4087. ; 18:11, s. 11250-11263
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Tidskriftsartikel (refereegranskat)abstract
- We present a method for reducing intensity fluctuations that typically occur when a spatial light modulator is updated between consecutive computer generated holograms. The method is applicable to most iterative hologram generating algorithms and minimizes the average phase difference between consecutive holograms. Applications with high stability requirements, such as optical force measurement with holographic optical tweezers, should benefit from this improvement. (C) 2010 Optical Society of America
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