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Adaptive Focal Length Imaging System using Liquid Crystal Spatial Light Modulator


  • Institute of Field Robotics, King Mongkut’s University of Technology Thonburi, 126 Pracha-utid Road, Bangmod, Tungkaru, Bangkok – 10140, Thailand
  • Department of Mathematics, Srinakharinwirot University, 114 Sukhumvit 23, Bangkok – 10110, Thailand
  • Department of Control System and Instrumentation Engineering, King Mongkut’s University of Technology, Thonburi 126 Pracha-utid Road, Bangmod, Tungkaru,Bangkok – 10140, Thailand


In this paper, we present a single-lens based imaging system that its focal length can be adjusted by using Liquid Crystal Spatial Light Modulator (LC-SLM). The SLM is placed at the aperture stop of the imaging system to work as a Phase Mask (PM) that modifies the light wavefront passing the exit pupil. By changing the pixel-based PM pattern that sends to the SLM, the focal length of the imaging system can be varied in the same spirit as conventional mechanical-zoom lenses. We demonstrate a proof-of-concept system for high magnification industrial inspection applications in a laboratory setup. We show the results that the focal length of the system is adjustable within the range ±2.0mm.


Autofocus, Adaptive Focal Length, Liquid Crystal, Phase Mask, Spatial Light Modulator, Wavefront Modification.

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