We propose curved V-groove-based patterns for light guide plates (LGPs) and demonstrate their performance by calculating their uniformity and luminance. Instead of the linear V-groove patterns used in previous research, curved patterns with asymmetric V-groove cuts were applied to the LGPs. The feasibility of obtaining enhanced uniformity and luminance from LGPs with the proposed patterns was evaluated by varying the degree of asymmetry of the V-grooves themselves and the distance between the V-groove patterns. The suggested patterns provided more stable uniformity with a small number of patterns and a large distance between patterns. The number of V-grooves is directly related to the processing time, and the degree of asymmetry in the V-groove cuts corresponds to the processing error during fabrication. Therefore, the proposed patterns could be fabricated with a low tolerance and shorter processing time. Their use would contribute to the cost-effective fabrication of LGPs. Because LGPs using the proposed patterns exhibited uniform illumination, a small number of curved patterns composed of asymmetric V-grooves can improve the characteristics of edge-type backlighting.
We report an optimization of the fabrication method on arrays of vertically grown nanometer scaled silver rod using nanosphere (polystyrene) lift-off on SiO<sub>2</sub> wafer as a surface-enhance Raman scattering substrate by thermal evaporation technology as well as real-time vapor phase detection of CHCl<sub>3</sub> by the radiation of fiber optic coupled 785 nm diode laser. Raman peak at 668.2 cm<sup>-1</sup> for CHCl<sub>3 </sub>(C-H stretching band) was compared to the peak at 1088.4 cm<sup>-1</sup> of 1- propanethiol (CH<sub>3</sub> rock band) and the detection limit of CHCl<sub>3</sub> vapor phase contamination level was estimated as a function of the peak intensity ratio of 668.2 vs. 1088.4. The detectable range using Ag nanorod wells on SiO<sub>2</sub> substrate was 20-800 ppm. We were able to make significant steps toward developing cost effective nano-pattern as a Raman sensor.
We demonstrate the feasibility of OCT imaging for the investigation of samples, which are processed by the short pulse laser. The use of short pulse lasers in various material processing have provided the advantages such as a high peak power and a small heat affected zone over conventional methods based on mechanical treatment. However, due
to the improper application of the lasers, the unwanted surface or structural deformation of materials and the thermal damages around an irradiation spot can be caused. Thus, the real-time monitoring/evaluation of laser processing performance <i>in-situ</i> is needed to prevent the excessive deformation of the material and to determine optimal processing conditions. As a standard method to investigation of the material processing by using the lasers, the
scanning electron microscopy (SEM) or the transmission electron microscopy (TEM) observation of a physically cleaved surface is used although sample damages are given during the cleaving and polishing process. In this paper, we utilized the OCT advantages such as high resolution and non-invasive investigation to evaluate the laser processing performance. OCT images for the deformation monitoring of the ABS plastic present correlation with images obtained from conventional investigation methods. OCT images of the maxillary bone clearly show the difference in the pit formation of the biological sample at different irradiation conditions. We prove the potential of
OCT for the evaluation of laser-processed various samples. Integrating OCT system into a laser processing system, we can visualize the effect of laser-based treatments in clinical and industrial fields.
Recently techniques for two dimensional (2D) or three dimensional (3D) image engraving inside crystal have been developed utilizing its transparency and high refractive index. However, due to the low tolerance against shock, heaviness and high cost of crystal, poymethyl methacryslate (PMMA) can be an attractive alternative for the laser engraving because PMMA has comparable transparency and refractive index to crystal while it is much easier to process. In this paper, we present the preliminary evaluation of PMMA as laser engraving material, potentially replacing crystal. For the comparative evaluation of crystal and PMMA, we used a 3D Laser Engraving System with a Q-switched 2<sup>nd</sup> harmonic Nd:YAG laser. Pulse energy and repetition rate of Nd:YAG laser were 26.9 mJ and 50 ~ 60 Hz, respectively to produce dot engravings inside crystal and PMMA. Also, the pulse duration time was less than 10 ns. We observed the size and shape of engraved points inside both material and resulting image formation depending on the distance between points (100 ~ 150 μm) as a function of laser power output. For the surface image comparison, an optical microscopy was used, and the cross sectional views of individual points were scanned every 10 μm using an optical coherence tomography (OCT) system. Our results demonstrate that laser engraving inside PMMA created better defined image formation from pure melting process rather than from cracking process inside crystal. We also present optimal 3D laser engraving conditions for PMMA as an alternative material to improve upon crystal's disadvantages.
In quantitative evaluation of facial skin chromophore content using color imaging, several factors such as view angle and facial curvature affect the accuracy of measured values. To determine the influence of view angle and facial curvature on the accuracy of quantitative image analysis, we acquire cross-polarized diffuse reflectance color images of a white-patched mannequin head model and human subjects while varying the angular position of the head with respect to the image acquisition system. With the mannequin head model, the coefficient of variance (CV) is determined to specify an optimal view angle resulting in a relatively uniform light distribution on the region of interest (ROI). Our results indicate that view angle and facial curvature influence the accuracy of the recorded color information and quantitative image analysis. Moreover, there exists an optimal view angle that minimizes the artifacts in color determination resulting from facial curvature. In a specific ROI, the CV is less in smaller regions than in larger regions, and in relatively flat regions. In clinical application, our results suggest that view angle affects the quantitative assessment of port wine stain (PWS) skin erythema, emphasizing the importance of using the optimal view angle to minimize artifacts caused by nonuniform light distribution on the ROI. From these results, we propose that optimal view angles can be identified using the mannequin head model to image specific regions of interest on the face of human subjects.
We propose anovel application of optical coherence tomography (OCT) to monitor pit formation in laser irradiated optical storage materials. A multilayer optical storage recordable compact disk, is composed of multiple layers, each of different structure. Disks were irradiated with a Q-Switched Nd:YAG laser with an energy of 373 mJ. Post-irradiated disks were evaluated by OCT and those images were compared with optical microscopy. Our results indicate that OCT is a useful instrument to investigate pit formation in mulitlayer optical storage disks and might also provide information to optimize optical memory technology.
In cutaneous vascular laser surgery, hemoglobin and melanin are important skin chromophores that influence treatment of port wine stain (PWS) birthmarks. A potential problem in quantitative chromorphore evaluaton is the error in image analysis associated with a number of factors, including nonuniform illumination and skin curvature. In this study, we used a mannequin head model to investigate how the accuracy of image analysis is influenced by view angle and facial curvature. Our results indicate that view angle and facial curvature affect the accuracy of the recorded color information. From this analysis, we propose that optimal view angles can be determined on an individual patient basis to analyze features on different regions of the face.
We suggest that Optical coherence tomography (OCT) is a potential imaging modality capable of assisting diagnosis in pulmonary medicines. OCT can provide extremely high resolution imaging and be performed with flexible fiber-optic bronchoscopy with small diameter
endoscopic probes. In this study, animal models of trachea, and lung surface were to investigate utility of OCT in pulmonary. Normal, malignant, and infectious disease animal model samples measured by OCT were compared to standard histologic H&E light microscopic imaging of the same sites.