Biomedical subjects

Sarun Sumriddetchkajorn

Publications and source records attributed to Sarun Sumriddetchkajorn.

4 recordsLinked to original sources

PubMed2006

Moderate-to-high optical-isolation reconfigurable 1 x 2 fiber-optic add-drop switches using a dense wavelength division multiplexing thin-film filter.

We propose and experimentally demonstrate thin-film filter- (TF) based reconfigurable 1 x 2 fiber-optic add-drop switch (FADS) structures. Our key idea is to locate a movable mirror oriented at a desired angle near the TF to switch the desired wavelength optical beams to the wanted switching ports. Our first moderate-optical-isolation TF-based reconfigurable 1 x 2 FADS is in a transmissive design. Another TF-based reconfigurable 1 x 2 FADS structure is in a retroreflective configuration, and it gives a very low optical-coherent cross talk. Our experimental proof of concept using an off-the-shelf four-cavity TF measured center wavelength at 1,545.749 nm and a 0.8 mm x 0.8 mm x 0.15 mm movable mirror confirms a -19 dB and a much improved <-53 dB optical-coherent cross talk for our transmissive and retroreflective configurations, respectively.

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PubMed2006

Surface plasmon resonance-based highly sensitive optical touch sensor with a hybrid noise rejection scheme.

A surface plasmon resonance (SPR)-based optical touch sensor structure is proposed that provides high switch sensitivity and requires a weak activating force. Our proposed SPR-based optical touch sensor is arranged in a compact Kretschmann-Raether configuration in which the prism acting as our sensor head is coated with a metal nanofilm. Our optical-based noise rejection scheme relies on wavelength filtering, spatial filtering, and high reflectivity of the metal nanofilm, whereas our electrical-based noise reduction is obtained by means of an electrical signal filtering process. In our experimental proof of concept, a visible laser diode at a 655 nm centered wavelength and a prism made from BK7 with a 50 nm thick gold layer on the touching surface are used, showing a 7.85 dB optical contrast ratio for the first touch. An estimated weak mechanical force of <0.1 N is also observed that sufficiently activates the desired electrical load. It is tested for 51 operations without sensor malfunction under typical and very high illumination of 342 and 3000 lx, respectively. In this case, a measured average optical contrast of 0.80 dB is obtained with a +/-0.47 dB fluctuation, implying that the refractive index change in a small 3.2% of the overall active area is enough for our SPR-based optical touch sensor to function properly. Increasing optical contrast in our SPR-based optical touch sensor can be accomplished by using a higher polarization-extinction ratio and a narrower-bandwidth optical beam. A controlled environment and gold-coated surface using the thin-film sputtering technique can help improve the reliability and the durability of our SPR-based optical touch sensor. Other key features include ease of implementation, prevention of a light beam becoming incident on the user, and the ability to accept both strong and weak activating forces.

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PubMed2003

Micromechanics-based digitally controlled tunable optical beam shaper.

A digitally controlled programmable optical beam shaper that uses a two-dimensional (2-D) small-tilt micromirror device is introduced. The optical intensity profile at any spatial position can be independently modified by use of a macropixel, incorporated with binary pulse-width modulation. An experimental proof-of-concept optical beam shaper with a commercial 2-D digital micromirror device has shown that the spatial profile of a He-Ne laser beam can be digitally manipulated. Investigation of the analog intensity control showed 256-level nonlinear degamma behavior with a measured 24.5-dB optical contrast ratio and a 10-bit spatial resolution. The performance of this tunable optical beam shaper is limited by the dimensions of the micromirror, the intermirror distance, the size of the optical beam, the number of bits used to control the micromirror, the diffraction effect, and the quality of the imaging optical system.

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PubMed2002

Micro-electro-mechanical system-based digitally controlled optical beam profiler.

An optical beam profiler is introduced that uses a two-dimensional (2-D) small-tilt micromirror device. Its key features include fast speed, digital control, low polarization sensitivity, and wavelength independence. The use of this 2-D multipixel device opens up the important possibility of realizing several beam profile measurement concepts, such as a moving knife edge, a scanning slit, a moving pinhole, a variable aperture, and a 2-D photodiode array. The experimental proof of the optical beam profiler concept using a 2-D digital micromirror device to simulate the 2-D moving knife edge indicates a small measurement error of 0.19% compared with the expected number based on a Gaussian beam-propagation analysis. Other 2-D pixel arrays such as a liquid-crystal-based 90 degrees polarization rotator sandwiched between crossed polarizers can also be exploited for the optical beam whose polarization direction is known.

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