Calibration of spatial light modulators suffering from spatially varying phase response
Artikel i vetenskaplig tidskrift, 2013

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 layer of 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 varying scale factor, generally does not yield sufficiently accurate conversion for applications requiring highly controllable output fields, such as holographic optical trapping (HOT). We therefore propose a method where the pixel addressing values are given by a three-dimensional polynomial, with two of the variables being the (x;y)-positions of the pixels, and the third their desired phase values. The coefficients of the polynomial are determined by measuring the phase response in 8×8 sub-sections of the SLM surface; the degree of the polynomial is optimized so that the polynomial expression nearly replicates the measurement in the measurement points, while still showing a good interpolation behavior in between. The polynomial evaluation increases the total computation time for hologram generation by only a few percent. Compared to conventional phase conversion methods, for an SLM with varying phase response, we found that the proposed method increases the control of the trap intensities in HOT, and efficiently prevents the appearance of strong unwanted 0th order diffraction that commonly occurs in SLM systems.

Computer holography

Phase modulation

Holographic optical element

Digital holography

Spatial light modulators

Diffractive optics

Optical tweezers

Laser trapping

Optical manipulation

Författare

David Engström

Göteborgs universitet

Martin Persson

Göteborgs universitet

Jörgen Bengtsson

Chalmers, Mikroteknologi och nanovetenskap (MC2), Fotonik

Mattias Goksör

Göteborgs universitet

Optics Express

1094-4087 (ISSN)

Vol. 21 13 16086-16103

Styrkeområden

Informations- och kommunikationsteknik

Nanovetenskap och nanoteknik

Livsvetenskaper och teknik

Ämneskategorier

Medicinsk apparatteknik

Atom- och molekylfysik och optik

Elektroteknik och elektronik

DOI

10.1364/OE.21.016086