• 한국광학회지
• /
• 제8권2호
• /
• pp.161-164
• /
• 1997

편광유지 광섬유를 이용한 주파수가 안정화된, 두 개의 서로 수직으로 편광된 종모우드를 갖는 He-Ne레이저 빛을 LoTa $O_{3}$ 위상변조기로 구성된 센서부(sensor head)로 전달해 줌으로써 원격에서 전기장을 측정할 수 있는 hybrid, heterodyne 간섭식 센서를 구성하였다. In/quadrature-phase위상변조풀이 방식을 이용하여 전기광학 효과에 의해 서로 수직으로 편광된 두 모우드 사이에 유도된 위상차이를 측정함으로써 항상 높은 검지율을 유지할 수 있는 전기장 센서를 구성하고, 이를 이용하여 광학 물질에 유도된 복굴절도 측정을 할 수 있었다.

• 한국광학회지
• /
• 제8권1호
• /
• pp.26-30
• /
• 1997

서로 수직으로 편광되고 두개의 종모우드로 발진하는 주파수가 안정화된 He-Ne 레이저를 이용하여 넓은 측정 범위를 갖는 헤테로다인 간섭계를 구성하였다. 두 모우드 사이의 맥놀이 주파수인 684MHz에 대한 라디오 주파수 간섭을 이용하여 약 .+-.1.74.mu.m의 분해능으로 광학매질의 광학두께를 측정할 수 있는 장치를 구성하였다. 이와 같은 측정장치를 이용하여 Nd:YAG 레이저의 수동형 Q-스위칭에 포화흡수체로 사용되고 있는 유기염료 박막의 두께와 국부적인 광학두께의 변화에 대한 map을 구할 수 있었다.

• International Journal of Aeronautical and Space Sciences
• /
• 제13권2호
• /
• pp.221-228
• /
• 2012

An active compensation method for the deformation of composite structures using additional controllable metal parts is proposed, and its feasibility is experimentally investigated in a simulated space environment. Composite specimens are tested in a vacuum chamber, which is able to maintain pressure on the order of 10-3 torr and interior temperature in the range of ${\pm}30^{\circ}C$. The displacement-measuring interferometer system, which consists of a heterodyne HeNe laser and an interferometer, is used to measure the displacement of the whole structure. Meanwhile, the strain of the composite part and temperature of both parts are measured by fiber Bragg grating sensors and thermistors, respectively. The displacement of the composite structure is maintained within a tolerance of ${\pm}1{\mu}m$ by controlling the elongation of the metal part, which is bonded to the end of the composite part. Also, the possibility of fiber Bragg grating sensors as control input sensors is successfully demonstrated using a proper corrective factor based on the specimen temperature gradient data.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 하계학술대회 논문집 E
• /
• pp.2434-2437
• /
• 1999

In order to detect the ultrasonic that is generated by the partial discharge of the heavy electric machinery, a Laser Doppler Vibrometer (LDV) was developed. A Michelson type interferometer which employed heterodyne signal process technique was built to measure the frequency and amplitude of vibration. The output signal of the fast photodetector was a frequency modulated signal centered at 40 MHz. The signal from the detector was amplified and downconverted to intermediate frequency centered at 1 MHz after mixing process. The voltage output that was proportional to the velocity of the moving surface(PZT) was obtained using PLL. The spectrum of the FM signal was analyzed and integration method was introduced to obtain amplitude information. This LDV can be used to measure the vibration of MEMS devices, automobiles, HDD and CDP.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2000년도 하계학술대회 논문집 C
• /
• pp.2195-2197
• /
• 2000

In order to detect the ultrasonic that is generated by the partial discharge of the heavy electric machinery a Laser Doppler Vibrometer (LDV) is developed. A Michelson type interferometer which employed heterodyne signal process technique is built to measure the frequency and amplitude of vibration. The output signal of the fast photodetector is a frequency modulated signal centered at 40 MHz. The signal from the detector is amplified and converted to intermediate frequency centered at 1 MHz after mixing process. The voltage output that is proportional to the velocity of the moving surface(PZT) is obtained using PLL. The spectrum of the FM signal is analyzed and integration method was introduced to obtain amplitude information. This LDV can be used to measure the vibration of MEMS devices, automobiles, HDD and CDP.

• 한국자기학회지
• /
• 제8권6호
• /
• pp.380-387
• /
• 1998

본 논문에서는 수소($H_2$)의 주입에 따라(자기적 성질)와 strain (elastic 성질)의 변화가 최대가 될 수 있는 Fe/Zr 다층박막으로 구성된 센서재료를 개발하였다. Sputtering (RF diode) 진공 적층 시스템을 이용하여 srqurntial supttering 빙식으로 변조파장($\lambda$)이 $3{\AA}{$\leq}{\lambda}{$\leq}50{\AA}$이고 $Fe_{80}Zr_{20}$의 성분을 가진 compositionally modulated(CM)된 Fe/Zr 다층박막을 적층 시킨 후 전기분해 방법으로 수소를 주입 시켜 수소에 의해 변화된 자화 및 strain 이 최대가 되는 Fe/Zr 박박을 선택하였다. 박막 재료가 수소화된 자기적 성질의 변화는 자화 및 stain 이 최대가 되는 Fe/Zr 박막을 선태하였다. 박막 재료가 수소화된 후의 자기적 성질의 변화는 히스테리시스 graph와 vibrating sample magnetometer (VSM)를 통해, 그리고 strain 의 변화는 laser heterodyne interferometer (LHI)등으로 분서되어 졌다. 선택된 최적의 센서재료는 single-mode 광섬유를 이용한 Michelson interometer의 sensing arm에 직접 coating 되어 주입된 수소의 양을 간접적으로 측정할 수 잇는 Fiber-optic H2 gas 센서에 응용되엇다. 개발된 센서는 진단하고자 하는 구조물 내의 부식(수소화에 의한) 정도를 손쉽고, 정확하게 감지할 수 있을 것으로 기대 되므로 비파괴 검사(non-destrucive test evaluation; NDE) 응용에 사용될 수 있다.

• 한국정밀공학회지
• /
• 제21권11호
• /
• pp.75-82
• /
• 2004

A metrological atomic force microscope (M-AFM) was developed fur the length measurements of nanometer range, through the modification of a commercial AFM. To eliminate nonlinearity and crosstalk of the PZT tube scanner of the commercial AFM, a two-axis flexure hinge scanner employing built-in capacitive sensors is used for X-Y motion instead of PZT tube scanner. Then two-dimensional displacement of the scanner is measured using two-axis heterodyne laser interferometer to ensure the meter-traceability. Through the measurements of several specimens, we could verify the elimination of nonlinearity and crosstalk. The uncertainty of length measurements was estimated according to the Guide to the Expression of Uncertainty in Measurement. Among several sources of uncertainty, the primary one is the drift of laser interferometer output, which occurs mainly from the variation of refractive index of air and the thermal stability. The Abbe error, which is proportional to the measured length, is another primary uncertainty source coming from the parasitic motion of the scanner. The expanded uncertainty (k =2) of length measurements using the M-AFM is √(4.26)$^2$+(2.84${\times}$10$^{-4}$ ${\times}$L)$^2$(nm), where f is the measured length in nm. We also measured the pitch of one-dimensional grating and compared the results with those obtained by optical diffractometry. The relative difference between these results is less than 0.01 %.

• 한국재료학회지
• /
• 제6권6호
• /
• pp.632-635
• /
• 1996

조성 변조된 비정질 Fe80Zr20박막의 자기적 성질과 기계적 성질 변화를 전해적 방법에 의한 수소 취입 시간의 함수로 측정하여, 그 상관 관계를 연구하였다. 박막의 Young's modulus는 진동 cantilever 시료의 공명 주파수를 , 10-4nm의 측정 감도를 지닌 laser heterodyne interferometer를 써서 측정하였다. 농도 2N의 인산 전해액에 침적된 시료에 26.3mA/$\textrm{cm}^2$의 전류를 흘려 이루어진 수소취입에 의해, Fe80Zr20 박막의 포화자화 정도는 8배, Young's modulus는 18배 가량 증가하였다. Fe80Zr20박막의 자기적 성질의 변화가 원자적 scale의 미세 구조 변화에 의한 것이라는 간접적인 증거를 제공하였으며, cantilever 시료의 공명주파수 측정을 통하여 박막재료의 기계적 성질을 연구할 수 있는 새로운 가능성을 제시하였다.

• Journal of the Optical Society of Korea
• /
• 제15권4호
• /
• pp.394-397
• /
• 2011

For the purpose of fabricating off-axis aspheric optics, we propose an 8-axis-polishing machine combined with a testing tower whose height is up to 9 m. The proposed polishing machine was designed and analyzed by using a well-known finite element method. The eight axes of the machine have a synchronized motion generated by a computer, and each axis was calibrated by a heterodyne laser interferometer or an optical encoder. After calibration, the maximum positioning error of the machine was less than 2 ${\mu}m$ within a whole 2 m ${\times}$ 2 m area. A typical fabrication result of a ${\phi}1.5$ m concave mirror was also described in this manuscript.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2005년도 추계학술대회 논문집
• /
• pp.216-219
• /
• 2005

In precision length measurements using optical interferometry based on homodyne or heterodyne principles, it is crucial to have frequency-stabilized monochromatic light sources. To the end, we investigate the possibility of utilizing the optical comb constituted by ultrashort femtosecond pulse lasers generated from a gain medium of titanium-doped aluminium oxide $(Ti:Al_2O_3)$. The optical comb is stabilized by locking to the caesium atomic clock, which allows all the modes of the comb to maintain an extremely high level of frequency stabilization to precision of one part in $10^{16}$. Then, high precision length measurements are realized by extracting a single or group of particularly wanted optical frequency components or by adopting a third-party light source locked to the comb. Required measurement system setup will be presented in detail along with experimental results.