• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.49-52
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• 2001

Moire topography method is a well-known non-contacting 3-D measurement method. Recently, the automatic 3-D measurement by moire topography has been required since the method was frequently applied to the engineering and medical fields. 3-D measurement using projection moire topogrphy is very attractive because of it s high measuring speed and high sensitivity. In this paper, using two-wavelength method of projection moire topography tested to measuring object with the $2\pi$-ambiguity problem. Experimental results prove that the proposed scheme is capable of finding absolute fringe orders, so that the $2\pi$-ambiguity problem can be effectively overcome so as to treat large step discontinuities in measured objects.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.1
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• pp.247-252
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• 2019

The diffraction properties of optical signals by multi-layered periodic structures is formulated in two-dimensional space by using Fourier expansions associated with basic grating profile. The fields in each layer are then expressed in terms of characteristic modes, and the complete solution is found rigorously by using a modal transmission-line theory(MTLT) to address the pertinent boundary-value problems. Such an approach can treat periodic arbitrary gratings containing arbitrarily shaped dielectric components, which may generally have optical properties along directions that are parallel or perpendicular to the multi-layers. This paper illustrates the present approach by comparing our numerical results with data reported in the past for simple periodic circular 2D structures. In addition, this proposed theory can apply easily for more complex configurations, which include multiple periodic regions with several possible canonic shapes and high dielectric constants.

• Proceedings of the Optical Society of Korea Conference
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• 1996.09a
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• pp.51-51
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• 1996

• ETRI Journal
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• v.31 no.2
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• pp.228-230
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• 2009

InP-based planar waveguide 48-channel concave grating demultiplexers with a channel spacing of 0.8 nm (100 GHz) are described and demonstrated. Polarization insensitivity and flattened spectral response are successfully achieved by the introduction of a polarization compensator and a two-focus grating, respectively. The fabricated device shows a polarization-dependent wavelength shift of less than 20 pm and a -3 dB spectral width of about 0.55 nm (68.75 GHz) over all channels.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.4
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• pp.605-610
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• 1997

An analysis method for the electromagnetic scattering of a Tm polarized plane wave from a periodic strip grating over a grounded dielectric slab is considered from the viewpoint of reflection grating problem. The parameters of strip gratings showing Bargg and Off-Bragg blazing phenomena at the frequency of 10GHz are derived teoretically. The strip grating structure is implemented using Aluminum plate(groung conductor), paraffin(dielectric material.epsilon.$_{r}$=2.24), and copper(strip conductor0.08m thickness). The experimental results(reflection power) of Bragg as well as Off-Bragg blazing phenomenon for TM polarized plane wave have been compared with the theoretical results and fairly good agreements between theory and experiment have been observed.d.

• Broadcasting and Media Magazine
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• v.6 no.2
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• pp.84-101
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• 2001

In this paper, we present a primitive system design of a super multi-view(SMV) 3-D display system based on a focused light array(FLA) concept using reflective vibrating scanner array(ViSA). The parallel beam scanning using a vibrating scanner array is performed by moving left and right an array of curvature-compensated mirrors or diamond-ruled reflective grating attached to a vibrating membrane. The parallel laser beam scanner array can replace the polygon mirror scanner which has been used in the SMV 3-D display system based on the focused light array(FLA) concept proposed by Kajiki at TAO(Telecommunications) Advancement Organization). The proposed system has great advantages in the sense that it requires neither huge imaging optics nor mechanical scanning pals. Some mathematical analyses and fundamental limitations of the proposed system are presented. The proposed vibrating scanner array, after some modifications and refinements, may replace polygon mirror-based scanners in the near future.

• Korean Journal of Optics and Photonics
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• v.16 no.3
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• pp.196-200
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• 2005

A 40 channel arrayed-waveguide grating (AWG) filter operating in C-band and L-band wavelength regions has been fabricated using PLC (Planar Lightwave Circuit) processes with 0.75 refractive index difference. Its design was optimized for matching the center wavelength with the ITU-recommended wavelength. The characteristics of the fabricated C-band AWG are as follows; average insertion loss < 2.5 dB, polarization-dependent loss < 0.3 dB, non-adjacent crosstalk >35dB, and the loss uniformity of 0.8 dB. In the L-band AWG, wavelength accuracy is below 0.02nm.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.11
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• pp.70-75
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• 1997

a wavelength division multiplexer based on a polymeric arrayed-waveguide grating has been designed and fabricated. A 4-channel multiplexer with a spacing of 3.2 nm is designe dby using te 2-dimensional beam propagation method. A UV-curable epoxy, NOA73, is used for the core layer, and a passive polymer, PMMA, for the cladding layer. The polymer waveguides are fabricated by the reactive ion etching method and their optical properties are characterized. The fabricted device has a center wavelength of 1548.3 nm, and the wavelength spacing between the channels is 3.2nm. The measured crosstalk is better than -18dB.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.3
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• pp.173-178
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• 2019

To analyze the diffraction properties of optical signals by periodic blazed 2D diffraction gratings, Toeplitz dielectric tensor is first defined and formulated by 2D spatial Fourier expansions associated with asymmetric blazed grating profile. The characteristic modes in each layer is then based on eigenvalue problem, and the complete solution is found rigorously in terms of modal transmission-line theory (MTLT) to address the pertinent boundary-value problems. Toeplitz matrix of symmetric and sawtooth profiles is derived from that of asymmetric blazed grating profile, and the diffraction properties for each profile are numerically simulated. The numerical results reveal that the asymmetric and symmetric profiles behave as anti-reflection GMR filter while the sawtooth profile works better as anti-transmission one rather than anti-reflection filter.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.2
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• pp.350-356
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• 2012

The tension effect on fiber Bragg gratings was analyzed and the linearity of 1.24 nm/10kpsi was obtained when Bragg wavelength was varied within 3 nm by applied tension. Using tension control method, different center wavelength fiber Bragg grating(FBG) were fabricated by only single period phase mask. These serially connected four FBGs showed the transmission spectrum of 1.5 nm linewidth as a 3 dB bandwidth which was twice that of a conventional FBG.