• Proceedings of the KIEE Conference
• /
• 2007.11a
• /
• pp.138-139
• /
• 2007

The use of conventional Twyman and Fizeau interferometers inevitably fails in testing high precision optics because of errors always existing in reference elements producing the reference wavefront. Therefore it is necessary to apply to this task the interferometers of a radically new type, which are able to produce perfect reference wavefront with the help of light diffraction by a small obstacle or pinhole. In this paper new theoretical approaches and schematics of point diffraction interferometers are considered in detail with paying attention to constructive reliability. Such interferometers do not use reference optical surfaces and readily provide adequate estimation of errors and aberrations value of 0.01 wavelengths.

• Current Optics and Photonics
• /
• v.4 no.4
• /
• pp.330-335
• /
• 2020

We have investigated optimization of the working distance (WD) for a highly miniaturized imaging probe for endoscopic optical coherence tomography (OCT). The WD is the axial distance from the distal end of the imaging probe to its beam focus, which is demanded for dimensional margins of protective structures, operational safety, or full utilization of the axial imaging range of OCT. With an objective lens smaller than a few hundred micrometers in diameter, a micro-optic imaging probe naturally exhibits a very short WD due to the down-scaled optical structure. For a maximized WD careful design is required with the optical aperture of the objective lens optimally filled by the incident beam. The diffraction-involved effect was taken into account in our analysis of the apertured beam. In this study, we developed a simple design formula on the maximum achievable WD based on our diffraction simulation. It was found that the maximum WD is proportional to the aperture size squared. In experiment, we designed and fabricated very compact OCT probes with long WDs. Our 165-㎛-thick fiber-optic probes provided WDs of 3 mm or longer w ith reasonable OCT imaging performance.

• Journal of the Microelectronics and Packaging Society
• /
• v.22 no.3
• /
• pp.73-77
• /
• 2015

This paper presents integrated polymeric spectrometer module which offers compact size, easily-fabricated structure and low cost. The proposed spectrometer module includes the nano diffraction grating with non-uniform pitch and planar optical waveguide with concave mirror to be fabricated by UV imprint lithography. To increase the reflection efficiency, we designed the nano diffraction grating with triangular profiles. The polymeric planar spectrometer includes a spectral bandwidth of 700 nm, resolution of 10 nm and precision below 5 nm. This polymeric planar spectrometer is well-suited for sensor system.

• Laser Solutions
• /
• v.17 no.2
• /
• pp.19-25
• /
• 2014

Optical embedded diffraction gratings with the bulk modification in BK-7 glass plates excited by tightly focused high-intensity femtosecond (130fs) Ti: sapphire laser (peak wavelength = 790nm) were demonstrated. The structural modifications with diameters ranging from 400nm to $4{\mu}m$ were photo-induced after plasma formation occurred upon irradiation with peak intensities of more than $1{\times}1013W/cm^2$. The graded refractive index profile was fabricated to be a symmetric around from the center of the point at which low-density plasma occurred. The maximum refractive index change was estimated to be $1.5{\times}10^{-2}$. The two optical embedded gratings in BK-7 glass plate were demonstrated with refractive index modification induced by the scanning of low-density plasma formation.

• Korean Journal of Optics and Photonics
• /
• v.9 no.5
• /
• pp.315-320
• /
• 1998

The characteristics and structures of photopolymer are analyzed in this paper, which recently have various applications in optical information processing and optical memory, Especially, Du Pont's photopolymer OmniDex 706 reflection film is used in many experiments of different exposures and incident angles, and analyzed by the diffraction pattern generated by glass plate's reflection beam. With the dark reaction of the monomer in photopolymerization, dynamic parameters are considered due to the variation of exposure time and diffusion time delay after exposure. The performance of diffraction efficiency is improved by 10%, when an exposure time is 6.25 sec, and a diffusion time delay is 2 minute.

• Applied Microscopy
• /
• v.37 no.3
• /
• pp.199-208
• /
• 2007

We have made an optical device to study the wave optics phenomena, such as image and diffraction pattern, constructive and destructive interference, by direct operation of laser beam and optical lenses. It consists of laser beam, goniometer, objective lens, intermediate lens, projection lens, CCD system, and computing system. As a result of the performance test, we were able to magnify samples up to 44 times with the resolution of about $5{\mu}m$. It is expected to help EM users understanding more easily principles of transmission electron microscopy (TEM).

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.22 no.5
• /
• pp.956-966
• /
• 1997

Dynamic free-space optical interconnection system is experimented by a holographic crossbar with single-state switching architecture. For dynamic operation, electrically addressed liquid-crystal spatial light modulator and diffraction gratings are used in place of passive holograms of matrix-matrix crossbar. Diffraction gratings are consisted of regular cells which have different phase delays. This pixelated phase grating array displayed on SLM(Spatial Light modulator) deflects an input beam toward a wanted direction or splits an input beam into many beams and then steers them to desired positions. Through the experimental results, free-space optical interconnection is dynamically perfomed using a computer, SLM and phase diffraction gratings.

• Molecules and Cells
• /
• v.44 no.11
• /
• pp.851-860
• /
• 2021

Label-free optical diffraction tomography (ODT), an imaging technology that does not require fluorescent labeling or other pre-processing, can overcome the limitations of conventional cell imaging technologies, such as fluorescence and electron microscopy. In this study, we used ODT to characterize the cellular organelles of three different stem cells-namely, human liver derived stem cell, human umbilical cord matrix derived mesenchymal stem cell, and human induced pluripotent stem cell-based on their refractive index and volume of organelles. The physical property of each stem cell was compared with that of fibroblast. Based on our findings, the characteristic physical properties of specific stem cells can be quantitatively distinguished based on their refractive index and volume of cellular organelles. Altogether, the method employed herein could aid in the distinction of living stem cells from normal cells without the use of fluorescence or specific biomarkers.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2004.08a
• /
• pp.1208-1211
• /
• 2004

When irradiated with visible light in HPDLC, photoinitiator and coinitiator produce a radical for photopolymerization. According to the kinds of photoinitiator and coinitiator, quantity and rate of produced a radical is different. It is influence on photopolymerization rate relate on diffraction efficiency. Thus, this paper is about the effect of photoinitiator/coinitiator combinations in terms of diffraction efficiency and real-time first order diffraction efficiency.

• Proceedings of the Optical Society of Korea Conference
• /
• 1990.07a
• /
• pp.87-93
• /
• 1990

Estimation and collection of the suitable recording materials are important for the fabrication of the holographic optical elements. In this study, silver halide emulsion, photoresist and dichromated gelatin are selected as a recording materials to investigate the properties and processing methods. Some parameters which affect the diffraction efficiencies of the holographic optical elements (HOE) are presented. As an example of the HOE, the results of design and the fabrication method of the off axis 12P hologram lens are also presented.