• Journal of Korean Ophthalmic Optics Society
• /
• v.15 no.2
• /
• pp.169-174
• /
• 2010

Purpose: The purpose of this study is to evaluate the long-term stability of the improved symptoms and accommodative functions after completion of accommodative therapy. Methods: Seven children (mean age${\pm}$SD: $12{\pm}1.41$ years) who were successfully treated with a vision therapy program for either accommodative insufficiency or infacility were followed for 1 year. The visual symptoms of the subjects were measured by the College of Optometrists in Vision Development Quality of Life (COVD-QOL) checklist, and this was followed by measurement of the monocular and binocular accommodative facility with ${\pm}2.00$ D flipper lens. Results: The mean visual symptoms at the 1 year follow-up examination ($15.14{\pm}8.59$) showed a small increase, but there was no significant difference (p=0.446) from post-therapy ($11.86{\pm}7.22$). There was small regression in the monocular (left eye, $13.86{\pm}3.93cpm$) and binocular ($11.14{\pm}3.13cpm$) accommodative facility at the 1 year follow-up examination, but there were no significant different from the monocular ($15.86{\pm}4.14cpm$, p=0.147) and binocular ($13.21{\pm}3.76cpm$, p=0.066) accommodative facility measurements at post-therapy. Also, every subject met the normative values of ${\geq}7$ cpm for monocular accommodative facility and ${\geq}5$ cpm for binocular accommodative facility in the long-term. Conclusions: There was long-term maintenance of the improved visual symptoms and accommodative functions, and so it is clear that the positive therapeutic effects persist with accommodative therapy.

• Current Optics and Photonics
• /
• v.3 no.1
• /
• pp.78-85
• /
• 2019

The remote phosphor structure has been proven to bear greater luminous efficiency than both the conformal phosphor and in-cup phosphor structures; however, controlling its color quality is much more challenging. To solve this dilemma, various researchers have proposed dual-layer phosphor and triple-layer phosphor configuration as techniques to enhance the display brightness of white LEDs (WLEDs). Likewise, this study picked one of these configurations to utilize in multichip WLEDs with five distinct color temperatures in the range from 5600 to 8500 K, for the purpose of improving the optical properties of WLEDs, such as color rendering index (CRI), color quality scale (CQS), luminous efficacy (LE), and chromatic homogeneity. According to the results of this research, the triple-layer phosphor configuration has superior performance compared to other configurations in terms of CRI, CQS, and LE, and yields higher chromatic stability for WLEDs.

• Korean Journal of Optics and Photonics
• /
• v.1 no.2
• /
• pp.169-177
• /
• 1990

We have constructed the laser system which was consisted of a high voltage pulse poner supply, a rapid high voltage spark gap and the Blumlein transmission line circuit of the multiple parallel plate capacitor type, and have studied the self-preionization effect from this laser system without additional modifications. The value of inductive or resistive loading of the laser oscillator seems to have a significant effect on the preionization. The optimal operational condition of this laser system was obtained at the inductive loading of L = I mtl across the laser tube with the spark gap distance of 6.0 mm. nitrogen pressure of 50 torr, when repetition rate was 70 Hz. Stability was found to be better than 2.0Yo and EIP was 867 V/cm.torr.

• Bulletin of the Korean Chemical Society
• /
• v.11 no.4
• /
• pp.290-296
• /
• 1990

Ion-surface collision studies at low kinetic energies (1-100 eV) provide a unique opportunity for investigating reactions and collision dynamics at surfaces. A special ion optics system for generating an energy- and mass-selected ion beam of this energy is designed and constructed. An ultrahigh vacuum (UHV) reaction chamber, in which the ions generated from the beamline collide with a solid surface, is equipped with Auger electron spectroscopy (AES) and thermal desorption spectrometry (TDS) as in-situ surface analytical tools. The resulting beam from the system has the following characteristics : ion current of 5-50 nA, energy spread < 2eV, current stability within ${\pm}5%,$ and unit mass resolution below 20 amu. The performance of the instrument is illustrated with data representing the implantation behavior of $Ar^+$ into a graphite (0001) surface.

• Current Optics and Photonics
• /
• v.4 no.1
• /
• pp.44-49
• /
• 2020

In this paper, a new method is presented to measure the refractive index of single plain glass or multilayered materials, based on a laser frequency-shifted confocal feedback microscope. Combining the laser frequency-shifted feedback technique and the confocal effect, the method can attain high axial-positioning accuracy, stability and sensitivity. Measurements of different samples are given, including N-BK7 glass, Silica plain glass, and a microfluidic chip with four layers. The results for N-BK7 glass and Silica plain glass show that the measurement uncertainty in the refractive index is better than 0.001. Meanwhile, the feasibility of this method for multilayered materials is tested. Compared to conventional methods, this system is more compact and has less difficulty in sample processing, and thus is promising for applications in the area of refractive-index measurement.

• Current Optics and Photonics
• /
• v.4 no.5
• /
• pp.405-410
• /
• 2020

A new all-optical flip-flop (AOFF) method based on the absorption nulls of an injection-locked Fabry-Perot laser diode (FP-LD) in transverse magnetic (TM) mode is proposed and experimentally demonstrated. For the set and reset operations of the AOFF, injection locking and the destructive minus of beating in transverse electric (TE) mode are used. The absorption nulls on the TM mode are modulated according to the operations, and then non-inverted (Q) and inverted (${\bar{Q}}$) outputs can be obtained simultaneously. Thanks to the use of several absorption nulls, the proposed AOFF can achieve multiple outputs with extinction ratios of more than 15 dB. Even though the experiment is demonstrated at 100 Mbit/s, the results of previous experiments using the injection of a CW holding beam imply that the operation speed can increase to 10 Gbit/s.

• Korean Journal of Optics and Photonics
• /
• v.10 no.3
• /
• pp.259-264
• /
• 1999

The relationship is derived for color CRT display system between the spectral radian existence emitted and digital inputs. The amount of spectral radiant existence depends on the characteristics of the video board, electric circuits, and CRT as well as digital inputs. Especially, the function of this relationship changes as the amplifier gain and offset voltage of electric circuits. In this study, we set the test display system on the optimum state which satisfies gun independence characteristics by using the contrast and the brightness controls of display. Temporal stability, special uniformity, and color distinction of CRT display system are evaluated at the optimum state. Also contrasts in dark room and illuminated room are compared.

• Current Optics and Photonics
• /
• v.7 no.5
• /
• pp.557-561
• /
• 2023

Ultralow-noise soliton pulse generation over a wider Fourier frequency range is highly desirable for many high-precision applications. Here, we realize a low-phase-noise soliton pulse generation by transferring the low phase noise of a mode-locked laser to a silica microcomb. A 21.956-GHz and a 9.9167-GHz Kerr soliton combs are synchronized to a 2-GHz and a 2.5-GHz mode-locked laser through a fractional optoelectronic phase-locked loop, respectively. The phase noise of the microcomb was suppressed by up to ~40 dB at 1-Hz Fourier frequency. This result provides a simple method for low-phase-noise soliton pulse generation, thereby facilitating extensive applications.

• Korean Journal of Optics and Photonics
• /
• v.9 no.6
• /
• pp.390-395
• /
• 1998

Iterative Fourier transform algorithm (IFTA) was utilized for the phase retrieval problem or the optimal of the IFTA depends strongly on the selection of initial phase value. In this paper, we proposed the modified interactive Fourier transform algorithm in order to improve the convergence speed of error and the stability of convergence. The modified IFTA was reduced number of iteration about 30% than existing IFTA with the image size of 128$\times$128 pixel.

• Korean Journal of Optics and Photonics
• /
• v.7 no.4
• /
• pp.403-413
• /
• 1996

We study the propagation of two pulses with orthogonal linear polarizations in a nonlinear periodic dielectric structure with $X^{(3)}$ nonlinearity. Using an envelope- function approach, we derive the coupled nonlinear Schrodinger equations governing the spatio-temporal evolutions of the two orthogonally polarized modes in a nonlinear periodic structure. We then find their solitary-wave solutions referred to as coupled gap solitons. We show that two orthogonally polarized pulses can co-propagate as a coupled gap soliton through a nonlinear periodic structure while each pulse alone will be strongly reflected due to the Bragg reflection. Based on the results, we present an all-optical switching scheme which has a novel architecture and principle. We also study the stability of coupled gap solitons to find the dragging phenomena in a nonlinear birefringent periodic medium.