• Current Optics and Photonics
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• v.7 no.5
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• pp.485-495
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• 2023

The pixel size in high-resolution complementary metal-oxide-semiconductor (CMOS) image sensors continues to shrink due to chip size limitations. However, the pixel pitch's miniaturization causes deterioration of optical performance. As one solution, a quad color filter (CF) array with pixel binning has been developed to enhance sensitivity. For high sensitivity, the microlens structure also needs to be optimized as the CF arrays change. In this paper, the covered microlens, which consist of four microlenses covered by one large microlens, are proposed for the quad CF array in the backside illumination pixel structure. To evaluate the optical performance, the suggested microlens structure was simulated from 0.5 ㎛ to 1.0 ㎛ pixels at the center and edge of the sensors. Moreover, all pixel structures were compared with and without in-pixel deep trench isolation (DTI), which works to distribute incident light uniformly into each photodiode. The suggested structure was evaluated with an optical simulation using the finite-difference time-domain method for numerical analysis of the optical characteristics. Compared to the conventional microlens, the suggested microlens show 29.1% and 33.9% maximum enhancement of sensitivity at the center and edge of the sensor, respectively. Therefore, the covered microlens demonstrated the highly sensitive image sensor with a quad CF array.

• Korean Journal of Remote Sensing
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• v.26 no.2
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• pp.251-262
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• 2010

In order to provide quantitative control of the standard products of Geostationary Ocean Color Imager (GOCI), on-board radiometric correction, atmospheric correction, and bio-optical algorithm are obtained continuously by comprehensive and consistent calibration and validation procedures. The calibration/validation for radiometric, atmospheric, and bio-optical data of GOCI uses temperature, salinity, ocean optics, fluorescence, and turbidity data sets from buoy and platform systems, and periodic oceanic environmental data. For calibration and validation of GOCI, we compared radiometric data between in-situ measurement and HyperSAS data installed in the Ieodo ocean research station, and between HyperSAS and SeaWiFS radiance. HyperSAS data were slightly different in in-situ radiance and irradiance, but they did not have spectral shift in absorption bands. Although all radiance bands measured between HyperSAS and SeaWiFS had an average 25% error, the 11% absolute error was relatively lower when atmospheric correction bands were omitted. This error is related to the SeaWiFS standard atmospheric correction process. We have to consider and improve this error rate for calibration and validation of GOCI. A reference target site around Dokdo Island was used for studying calibration and validation of GOCI. In-situ ocean- and bio-optical data were collected during August and October, 2009. Reflectance spectra around Dokdo Island showed optical characteristic of Case-1 Water. Absorption spectra of chlorophyll, suspended matter, and dissolved organic matter also showed their spectral characteristics. MODIS Aqua-derived chlorophyll-a concentration was well correlated with in-situ fluorometer value, which installed in Dokdo buoy. As we strive to solv the problems of radiometric, atmospheric, and bio-optical correction, it is important to be able to progress and improve the future quality of calibration and validation of GOCI.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.10
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• pp.788-793
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• 2017

This paper presents the verification of accuracies of theoretical models for calculating the microwave reflections from rough sea surfaces. First of all, the Pierson-Moskowitz ocean spectrum was used to generate the rough sea surfaces. Then the relationship between the significant wave heights, root-mean-square(RMS) heights and wind speed was derived by estimating the significant wave heights and RMS heights of the generated sea surfaces according to various wind speeds, and compared the derived relationship with other measurement data sets. The reflection coefficients of the sea surfaces were calculated by using a numerical method(the moment method). Then, the numerical results were compared with Ament model, PO(Physical Optics) model, GO(Geometrical Optics) model and B-M(Brown-Miller) model for various roughness conditions(wind speed) and incidence angles. It was found that the Ament model is not accurate except for a very low roughness conditions($kh_{rms}$<0.4, k is wavenumber and $h_{rms}$ is RMS height). It was also found that at incidence angles lower than $70^{\circ}$, the PO and the GO models agree well with the numerical results, while the B-M model agrees well with the numerical analysis results at incidence angles higher than $80^{\circ}$ for very rough sea surfaces with $kh_{rms}$>10.

• Journal of Integrative Natural Science
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• v.4 no.3
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• pp.192-196
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• 2011

New method to encode multiple photonic features of Bragg type reflector on silicon wafer has been investigated. Multiple bit encodes of distributed Bragg reflector features have been prepared by electrochemical etching of crystalline silicon by using various square wave current densities. Optical characterization of multi-encoding of distributed Bragg reflectors on porous silicon was achieved by Ocean optics 2000 spectrometer for the search of possible applications of multiple bit encoding of distributed Bragg reflectors such as multiplexed assays and chemical sensors. The morphology and cross-sectional structure of multi-encoded distributed Bragg reflectors was investigated by field emission scanning electron micrograph.

• Proceedings of the KSRS Conference
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• v.1
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• pp.479-482
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• 2006

The absorption coefficient and backscattering properties of phytoplankton were calculated from the Mie theory. Given a simple case that phytoplankton and mineral particles are the only constitutions in seawater, the reflectance $b_b({\lambda})/[a({\lambda})+b_b({\lambda})]$was analyzed. Then the chlorophyll concentrations were estimated from remote sensing OC2 algorithm. The results show that reflectance in short wavelength region is more sensitive to the Chl variation; High mineral concentrations in seawater have significant influence on the reflectance spectrum; the existence of high mineral concentration may result in the mistake in chlorophyll estimation from OC2 algorithm.

• Journal of Integrative Natural Science
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• v.3 no.4
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• pp.237-240
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• 2010

Recently, number of studies for porous silicon have been investigated by many researchers. Multistructured porous silicon (PSi), distributed Bragg reflector (DBR) PSi, has been a topic of interest, because of its unique optical properties. DBR PSi were prepared by an electrochemical etch of $P^{{+}{+}}$-type silicon wafer of resistivity between 0.1 $m{\Omega}cm$ with square wave current density, resulting two different refractive indices. In this work, We have fabricated a simple and portable organic vapor-sensing device based on DBR porous silicon and investigated the optical characteristics of DBR porous silicon. DBR porous silicon have been characterized by FT-IR, Ocean optics 2000 spectrometer. The device used DBR PSi chip has been demonstrated as an excellent gas sensor, showing a great senstivity to a toxic vapor (TEP, DMMP, DEEP) at room temperature.

• Journal of Integrative Natural Science
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• v.3 no.1
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• pp.24-27
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• 2010

Multi-functionalized rugate porous silicon (PSi) for biosensor was developed by hydrosilylation with silole and its further reaction with biotin groups. PSi was generated by an electrochemical etching of silicon wafer in aqueous ethanolic HF solution PSi prepared by using etching conditions showed that many sharp spectral lines can be obtained in the optical reflectivity spectrum. 1,1-hydrovinyl-2,3,4,5-tetraphenylsilole was obtained from the reaction of 1,1-dilithio-2,3,4,5-tetraphenyl-1,3-butadiene with dichlorovinylsilane. Multi-functionalized PSi with silole and biotin groups was characterized by UV-vis absorption spectroscopy, Ocean optics 2000 spectrometer, and fluorescence spectroscopy. Optical characteristics such as reflectivity and photoluminescence (PL) were observed. An increase of the reflection wavelength in the reflectivity spectrum by 20 nm was observed, indicative of a change in refractive indices induced by hydrosilylation of the silole and biotin groups to the rugate PSi. This red-shift was attributed to the replacement of some of the Si-H group of fresh rugate PSi with silole and biotin group.

• Journal of Integrative Natural Science
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• v.2 no.4
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• pp.275-279
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• 2009

Recently, number of studies for porous silicon (PSi) have been investigated by many researchers. Multistructured porous silicon such as a distributed Bragg reflector (DBR) PSi, has been a topic of interest, because of its unique optical properties. DBR PSi were prepared by using an electrochemical etch of $P{^+}{^+}$-type silicon wafer with resistivity between 0.1 and $10m{\Omega}cm$. The electrochemical etch with square wave current density results in two different refractive indices in the porous layer. In this work, DBR porous silicon chips for a simple and portable organic vapor-sensing device have fabricated. The optical characteristics of DBR PSi have been investigated. DBR porous silicon have been characterized by FT-IR and Ocean optics 2000 spectrometer. The device used DBR PSi chip has been demonstrated as an excellent gas sensor, showing a great senstivity to organic vapor at room temperature.

• Journal of Integrative Natural Science
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• v.4 no.1
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• pp.11-14
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• 2011

Free-standing multilayer distributed Bragg reflectors (DBR) porous silicon dielectric mirrors, prepared by electrochemical etching of crystalline silicon using square wave currents are treated with polymethylmethacrylate (PMMA) to produce flexible, stable composite materials in which the porous silicon matrix is covered with caffeine-impregnated PMMA. Optically encoded free-standing DBR PSi dielectric mirrors retain the optical reflectivity. Optical characteristics of free-standing DBR PSi dielectric mirrors are stable and robust for 24 hrs in a pH 12 aqueous buffer solution. The appearance of caffeine and change of DBR peak were simultaneously measured by UV-vis spectrometer and Ocean optics 2000 spectrometer, respectively.

• Journal of Integrative Natural Science
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• v.5 no.1
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• pp.27-31
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• 2012

Relationship between reflection resonance and applied current density in Bragg photonic crystal has been investigated. Multiple bit encodes of distributed Bragg reflector features have been prepared by electrochemical etching of crystalline silicon by using various square wave current densities. Optical characterization of multi-encoding of distributed Bragg reflectors on porous silicon was achieved by Ocean optics 2000 spectrometer for the search of possible applications of multiple bit encoding of distributed Bragg reflectors such as multiplexed assays and chemical sensors. The morphology and cross-sectional structure of multi-encoded distributed Bragg reflectors was investigated by field emission scanning electron micrograph.