• Korean Journal of Optics and Photonics
• /
• v.8 no.5
• /
• pp.362-365
• /
• 1997

This paper presents a new optical phase stabilization technique for interferometric such as Mach-Zehnder interferometers or Homodyne detectors. The proposed technique can lock such interferometric systems in their maximum/minimum optical outputs without using a dither signal. The phase control scheme is a modified steepest decent algorithm, and is analyzed in terms of a delta modulation approach. It is also applicable to low-repetition rate pulsed interferometric systems in which conventionally used dithering method is difficult to be applied.

• Korean Journal of Optics and Photonics
• /
• v.10 no.2
• /
• pp.128-137
• /
• 1999

We found the point-spread function (PSF) including the recording and reconstruction systems of the modified triangular interferometer. We also derived the resolutions of the modified and Cochran's triangular interferometers, then the resolutions of both systems for amplification factor, wavelength, and hologram size were found and analyzed. Also, to demonstrate the feasibility of incoherent holography, the formation of an incoherent hologram using a mercury lamp and its optical reconstruction were presented.

• Korean Journal of Optics and Photonics
• /
• v.26 no.3
• /
• pp.155-161
• /
• 2015

We report the design and performance analysis of an off-axis three-mirror telescope as the fore optics for a new hyperspectral sensor aboard a small unmanned aerial vehicle (UAV), for low-altitude coastal remote sensing. The sensor needs to have at least 4 cm of spatial resolution at an operating altitude of 500 m, $4^{\circ}$ field of view (FOV), and a signal to noise ratio (SNR) of 100 at 660 nm. For these performance requirements, the sensor's optical design has an entrance pupil diameter of 70 mm and an F-ratio of 5.0. The fore optics is a three-mirror system, including aspheric primary and secondary mirrors. The optical performance is expected to reach $1/15{\lambda}$ in RMS wavefront error and 0.75 in MTF value at 660 nm. Considering the manufacturing and assembling phase, we determined the alignment compensation due to the tertiary mirror from the sensitivity, and derived the tilt-tolerance range to be 0.17 mrad. The off-axis three-mirror telescope, which has better performance than the fore optics of other hyperspectral sensors and is fitted for a small UAV, will contribute to ocean remote-sensing research.

• Korean Journal of Optics and Photonics
• /
• v.23 no.4
• /
• pp.167-171
• /
• 2012

This paper reports on the stray light analysis results of a compact imaging spectrometer (COMIS) for a microsatellite STSAT-3. COMIS images Earth's surface and atmosphere with ground sampling distances of 27 m at the 18~62 spectral bands (0.4 ~ 1.05 ${\mu}m$) for the nadir looking at an altitude of 700 km. COMIS has an imaging telescope and an imaging spectrometer box into which three electronics PCBs are embedded. The telescope images a $27m{\times}28km$ area of Earth surface onto a slit of dimensions $11.8{\mu}m{\times}12.1mm$. This corresponds to a ground sampling distance of 27 m and a swath width of 28 km for nadir looking posture at an altitude of 700 km. Then the optics relays and disperses the slit image onto the detector thereby producing a monochrome image of the entrance slit formed on each row of detector elements. The spectrum of each point in the row is imaged along a detector column. The optical mounts and housing structures are designed in order to prevent stray light from arriving onto the image and so deteriorating the signal to noise ratio (SNR). The stray light analysis, performed by a non-sequential ray tracing software (LightTools) with three dimensional housing and lens modeling, confirms that the ghost and stray light arriving at the detector plane has the relative intensity of ${\sim}10^{-5}$ and furthermore it locates outside the concerned image size i.e. the field of view of the optics.

• The Optical Journal
• /
• s.120
• /
• pp.39-44
• /
• 2009

한국광학기기협회가 격월간으로 발행하는 광학세계가 창간 20주년을 맞아 독자 대상의 설문조사를 실시했다. 1989년 4월 창간되어 2009년 3월로 통권 120호가 되는 광학세계는 그간 광학분야 전문잡지로 자리매김을 해왔다. 20년 동안 내용적인 변화는 물론 외형적인 변화도 있었다. 초기 $4{\times}6$배판에서 $5{\times}7$국배판으로 변화됐으며 협회 홈페이지를 통해 온라인상에서도 과월호를 볼 수 있게 되었다. 설문분석 결과 응답자들은 대체로 현재의 편집스타일과 기획에 만족하고 있다고 답했다. 대부분 광학세계를 통해 산업 및 업계 동향 파악의 활용이 가장 많은 것으로 나타났고 더욱 다양한 산업분야의 기술 및 시장 동향 소개를 바라는 요구가 있었다. 광학세계는 이와 같은 독자들의 생생한 평가와 제안을 수렴하여 앞으로 더욱 독자들의 요구를 만족시켜주는 광학전문잡지로 거듭나기 위해 노력할 것이다.

• Korean Journal of Optics and Photonics
• /
• v.28 no.4
• /
• pp.146-152
• /
• 2017

Alignment of the mirrors composing a space telescope is an important process for obtaining high optical resolution and performance of the camera system. The alignment of mirrors using cube mirrors requires a relative coordinate mapping between the mirror and the cube mirror before optical-system integration. Therefore, to align the spacecraft camera mirrors, the relative coordinates of the vertex of each mirror and the corresponding cube mirror must be accurately measured. This paper proposes a new method for finding the vertex position of a primary mirror, by using an optical fiber and alignment segments of a computer-generated hologram (CGH). The measurement system is composed of an optical testing interferometer and a multimode optical fiber. We used two theodolites to measure the relative coordinates of the optical fiber located at the mirror vertex with respect to the cube mirror, and achieved a measurement precision of better than $25{\mu}m$.

• New Physics: Sae Mulli
• /
• v.68 no.11
• /
• pp.1268-1274
• /
• 2018

Aircraft-warning lights are lights that are used to inform pilots in flight about the presence of buildings or dangerous objects. Currently, the light sources of most aircraft-warning lights have been replaced by light-emitting diodes (LEDs). However, the aircraft-warning lights that are installed do not meet the optical performance standards and may cause airplane collisions. Therefore, the use of such light poses a risk to aviation safety. In order to solve this problem, we designed a Fresnel lens with the same luminous intensity distribution ovef $360^{\circ}$ direction; thus, we collimated the light beam from the LED light source with a narrow beam divergence angle in the form of an array of aspheric pieces. After that, we designed and simulated an aircraft-warning-light optical system with a center luminous intensity of 20,000 cd and a vertical divergence angle of $3^{\circ}$ or more by optimizing the lens' tilt and the distance between the LED and the Fresnel lens.

• Proceedings of the Optical Society of Korea Conference
• /
• 2009.02a
• /
• pp.469-470
• /
• 2009

• Proceedings of the Optical Society of Korea Conference
• /
• 2004.07a
• /
• pp.198-199
• /
• 2004

• Proceedings of the Optical Society of Korea Conference
• /
• 2004.07a
• /
• pp.76-77
• /
• 2004