• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.44-50
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• 2003

This paper describes the thermal effect at Nd:YAG using a laser-diode side-pumping. To detect the depolarization loss and the retardation caused by the thermal effect, a λ/4 plate is inserted between the polarizer and the Nd:YAG laser material. Using a CCD has allowed detection of the variation of the beam pattern that could analyze the change of the refractive index of the Nd:YAG laser material by the thermal effect. Through the change of the probe beam power, we know that 21% of the pumping power was converted into heat in the material. The depolarization loss was 24.7% under a temperature of $25^{\circ}C$ of the laser material and a pumping power of 15 W. The inhomogeneous distribution showed that the retardation angle was 7$^{\circ}$ in the center of the material and 19$^{\circ}$ on the edge of it. It is confirmed that the thermal effect is analyzed at the each point of the laser material and it suggests an effective method to reduce the thermal effect on the LD side-pumped laser material.

• Journal of Biomedical Engineering Research
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• v.26 no.1
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• pp.37-42
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• 2005

We construct and test the polarization-sensitive optical coherence tomography (PS-OCT) system for imaging porcine and human articular cartilages. PS-OCT is a new imaging technology that provides information regarding not only the tissue structures but tissue components that show birefringence such as collagen. In this study, we measure the cartilage thickness of the porcine joint and the phase retardation due to collagen birefringence. Also, we demonstrate that changes of the collagen fiber orientation could be detected by the PS-OCT system. Finally, differences between normal and damaged human articular cartilage are observed using the PS-OCT system, which is then compared with the regular histology pictures. As a result, the PS-OCT system is proven to be effective for diagnosis of the pathology related to the cartilage. In the future, this technology may be used for discrimination of the collagen types. When combined with endoscope technologies, the PS-OCT images may become a useful tool for in vivo tissue testing.

• Korean Journal of Optics and Photonics
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• v.26 no.4
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• pp.195-202
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• 2015

We developed a reflection ellipsometer so that one can measure the extremely small optical anisotropy of a rubbed polyimide alignment layer, without being disturbed by the residual anisotropy of the substrate. The optical anisotropy of the alignment layer was measured as rubbing strength was increased, and the measured anisotropy was compared to the retardation obtained by using a transmission-type ellipsometer, to confirm the reliability of our reflection ellipsometer. With this measured anisotropy we could verify the formation of an alignment layer by rubbing, and could quantitatively evaluate the formation of the alignment layer.

• Korean Journal of Optics and Photonics
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• v.22 no.5
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• pp.219-222
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• 2011

Integrated optical waveguide polarization converters are among the essential components for constructing various functional optical integrated circuits. The RM materials have been widely used in liquid crystal displays for fabricating waveplates. In this work, the polarization converters are fabricated by using a solution of Reactive Mesogen(RM) dissolved in liquid crystal(LC). In the middle of the polymer waveguide, a groove is defined by an oxygen plasma etching in a direction perpendicular to the optical waveguide. The solution of RM-LC is inserted to fill up the groove, and then liquid crystal is aligned in a certain direction by applying an electric field. After the alignment, RM materal is crosslinked by UV light so as to form a permanent waveplate. The phase retardation of the waveplate is determined by the width of the groove, and by the birefringence and the degree of alignment of the LC. Polarization conversion efficiency of 90% is obtained for the wavelength of 1550 nm.

• Korean Journal of Optics and Photonics
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• v.11 no.6
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• pp.385-389
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• 2000

A phase-retardation function which was derived from Wigner distribution function (WDF) is used to increase a focal depth of a radially symmetric optical system. The WDF for one-dimensional signal is represented as a two-dimensional function of phasespace ($\chi,\zeta$), and a normalized irradiance is described as a form of the Strehl ratio (SR). The increase in the focal depth is accomplished by delivering a shearing tilt a that represents a characteristic of free space propagation with simple manipulation in the WDF space. In this paper we propose a method for evaluating the focal depth quantitatively by representing the phaseretardation function in terms of the focal depth term. In order to verify the validity of the proposed method, we compared the numerically analyzed result with that of J. Sochki's study. study.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.8
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• pp.494-498
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• 2016

In this paper, we proposed the 3-dimenstional (3D) analysis for calculating the optical characteristics of an autostereoscopic display with electric field driven liquid crystal (ELC) lens. From 3D analysis considering the slanting of lens, we calculate the cross-talk of each images and the distortion of viewing zone. Using geometric opics and extended Jones matrix method (EJMM), phase retardation of ELC lens according to position is calcuated and then optical path difference in 3D space considering tilt and azimuth angle of incident light is gotten. Then, intensity distribution is presented in the space. Through camparing the intensity distribution using ideal lens with the ELC lens, we identify the noise and image distortion of ELC lens. As a result, this analysis is expected to provide optimum design conditions for realistic and rigorous 3D display with ELC lens.

• Polymer(Korea)
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• v.35 no.5
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• pp.493-498
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• 2011

Reactive mesogens were used to prepare photo-cured liquid crystal films in which orientations of liquid crystal molecules were preserved by crosslinked networks of cured reactive mesogens. The molecular orientations of liquid crystal mixtures of photo-reative mesogens and non-reactive nematic liquid crystals were studied and compared before and after curing reactions. The effects of temperature and the amount of the non-reactive nematic liquid crystal in the mixture on birefringence of the liquid crystal films were investigated. It was found that optical compensation films with different birefringence could be prepared by controlling the amount of the nematic liquid crystals in the reactive mesogen mixtures.

• Korean Journal of Optics and Photonics
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• v.3 no.3
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• pp.143-147
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• 1992

1)iscussed in this paper are the effects of phase modulation on the line spread functions (LSF) and MTFs of ;I binocular objective system. The binocular objective lens is made in Korea. It has rotationally symmetric aberrations. The LSFs and MTFs are measured experimentally. The phase modulation is carried out by applying phase retardation $\pi$ on the aperture. The area where the phase is not retarded presents a double annular type. The OTF curves of phase modulated aperture are compared with that of unmodulated aperture. The comparison shows that there is the aberration compensation effect in aberration loaded system. Therefore the performance of many optical system can be improved without any loss of light energy by properly modulating the phase on the aperture.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.2
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• pp.344-348
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• 2007

In this paper, we propose the electrode of the Patterned Vertical Aligned (PVA) cell [1] for high transmittance. We use the 'TechWiz LCD' for calculation of the director configuration and optical characteristics to ensure the results of the proposed electrode structure. In general, the transmittance of the PVA cell depends on the shape of the electrode and cell gap. In this work the width of gate line and data line of the improved electrode design is set to be equal to that of the PVA conventional. Instead, we modified the shape of the top and bottom electrode on order to decrease the area of the defect. For verification, we compared the calculated optical transmittance of the PVA cell with the proposed electrode structure to the conventional PVA cell . As a result, we can confirm that the optical loss due to the variation of the retardation the LC cell around electrode can be definitely decreased by the proposed electrode.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.895-898
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• 2004

We propose configurations for a transflective in-plane switching (IPS) cell using muti-domain structures. Usually, the cell configurations for a transflective liquid crystal(LC) cell have a complicated structure, because retardation change of transmissive part and reflective part are not same. The transflective LC cell should have two configurations for each part, such as a multi-cell gap structure. With the ion-beam alignment and the horizontal switching LC cell, a simple structure for a transflective LC cell is proposed. The configuration only adopts one cell gap structure, which may help the enhancement of a yield. Their original optical properties in conventional transmissive and reflective type IPS liquid crystal dispaly(LCD) are kept, it shows the wide-viewing angle and the good wavelength dispersion characteristics.