• Current Optics and Photonics
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• 제6권1호
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• pp.23-31
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• 2022

Heterodyne efficiency is an indicator to evaluate the performance of space coherent laser communication systems. It is affected by signal light and local oscillator (LO) light amplitude, phase and polarization state. In this paper, based on the common heterodyne efficiency, a heterodyne efficiency model that can reflect polarization aberration of optical system is proposed. The heterodyne efficiency is analyzed when the signal light and the LO light are linearly polarized or circularly polarized. For a coherent communication optical system, when the incident signal light is right-circularly polarized light and the incident LO light is 45° linear polarized light. Based on the three-dimensional ray tracing theory and the heterodyne efficiency proposed in this paper, the change of polarization states and the distribution of heterodyne efficiency of the signal light and LO light influenced by the optical system's polarization aberration are analyzed. Analysis shows that the heterodyne efficiency model proposed in this paper can be used to evaluate coherent communication systems and reflect the influence of optical system polarization aberration.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.922-925
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• 2005

This article describes a FM modulation algorithm to increase the measurement speed by increasing the beat frequency of the laser without acousto-optic modulator(AOM) in the heterodyne laser interferometer. The proposed algorithm can increase the beat frequency of the heterodyne laser which limit the measurement speed by adjusting a carrier frequency through electronic circuit, while AOM is used to shift the frequency of the heterodyne laser in conventional method. Electronic circuit is constructed to modulate the signals from a laser interferometer and a waveform generator. The brier analysis, the measurement scheme of the system, and the experimental results using a Zeeman-stabilized He-Ne laser are presented. They demonstrate that the proposed algorithm is proven to enhance the measurement speed limit by increasing the beat frequency of the heterodyne laser.

• 대한전자공학회논문지SD
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• 제45권4호
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• pp.64-71
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• 2008

SAW(Surface Acoustic Waves)를 기반으로 passive RFID(Radio Frequency IDentification) tag 및 송수신 시스템을 제작하였다. Pulse position encoding 방식의 SAW ID 태그(tag)를 제작하여 amplitude on/off 방식의 SAW ID 태그에 비해 3배의 데이터 용량 증대 효과를 얻을 수 있었다. 또한, 수신 시스템을 heterodyne 방식과 direct conversion 방식으로 제작하였다. 측정 결과 direct conversion 방식으로 제작된 수신 시스템이 heterodyne 방식의 수신 시스템과 비교하여 isolation 특성이 10 dB 증가하였으며, 그 결과 무선 도달 거리가 증가했다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1738-1740
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• 1996

Laser Doppler Vibrometer using heterodyne method with a 632.8 nm He-Ne laser, has been developed for the measurement of small displacement and velocity. The measurement uses heterodyne method can be made insensitive to undesired vibration effect acting the system and can yield the sign of Doppler shift at the expense of increased complexity. A Bragg cell gives a frequency shift of 40MHz for heterodyne method. Frequency Modulated output is detected by spectrum analyzer.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.195-198
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• 2002

Demand for high precision measurement of large area is increasing in many industrial fields. White-light Scanning Interferometer(WSI) is a well-known method for 3D profile measurement. However WSI has some limitations in a measurement range because of the sensing mechanism. Therefore, in this paper we use a heterodyne laser interferometer to get over the limitations of a short measurement range in WSI, We suggest a new WSI system combined with heterodyne laser interferometer. This system is aimed at eliminating Abbe error with measuring the focus point directly. With the use of triggering functionality of WSI, we can use this system as a probe of a precision stage such as a probe of CMM. The suggested system gives a repeatability of 87 nm in the absolute distance measurement test under the laboratory environment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.225-226
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• 2007

In the semiconductor manufacturing industry, the heterodyne laser interferometer plays as an ultra-precise measurement system. However, the heterodyne laser interferometer has some unwanted environmental error which is caused from refraction in the air. This is an obstacle to improve the measurement accuracy in nanometer scale. In this paper we propose a compensation algorithm based on Data Fusion method which reduces the environmental error in the heterodyne laser interferometer. Through some experiments, we demonstrate the effectiveness of the proposed algorithm in measurement accuracy.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1142-1146
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• 2004

The ultra precision linear stage is an essential device in the fields of MEMS and Bio technology. A piezo electric motor is widely used for its better linear characteristics, faster response time, and smaller size than conventional electro-magnetic actuator. We develop a new inchworm type motor to implement an actuator-integrated a long stroke linear stage which can move fast. To implement a servo system, we use a heterodyne interferometer as a position sensor, and we propose a new measurement technique using I/Q demodulator, and we propose a counting method to measure the position of fast moving object with low cost circuitry. The characteristics of the actuator and servo system are evaluated by measuring its displacement with a commercial laser interferometer.

• International Journal of Precision Engineering and Manufacturing
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• 제6권2호
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• pp.34-39
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• 2005

The precision stage is an essential device for optic fiber assembly systems, micro machines and semiconductor equipments. A new piezoelectric inchworm type actuator is proposed to implement an actuator-integrated long-stroke linear stage. An in-and-quadrature phase (I/Q) heterodyne interferometer is developed as a feedback sensor of a servo system, and a synchronized counting method is proposed. The proposed measurement system can measure the accurate position of fast moving object with robustness to external sensing noise from actuator vibration. The developed servo stage will be applied to optic fiber device assembly system.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.140.1-140.1
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• 2015

Currently, As Plasma application is expanded to the industrial and medical industrial, Low temperature plasma characteristics became important. Especially in Medical industrial, Low temperature plasma directly adapted to human skin, so their plasma parameter is important. One of the plasma parameters is electron density, some kinds of method to measuring electron density are Thomson scattering spectroscopy and Millimeter-wave transmission measurement. But most methods is expensive to composed of experiment system. Heterodyne interferometer system is cheap and simple to setting up, So we tried to measuring electron density by Laser heterodyne interferometer. To measuring electron density at atmospheric pressure, we need to obtain the phase shift signal. And we use a heterodyne interferometer. Our guiding laser is Helium-Neon laser which generated 632 nm laser. We set up to chopper which can make a laser signal like a pulse. Chopper can make a 4 kHz chopping. We used Needle jet as Ne plasma sources. Interference pattern is changed by refractive index of electron density. As this refractive index change, phase shift was occurred. Electron density is changed from Townsend discharge's electron bombardment, so we observed phenomena and calculated phase shift. Finally, we measured electron density by refractive index and electron density relationship. The calculated electron density value is approximately 1015~1016 cm-3. And we studied electron density value with voltage.

• Current Optics and Photonics
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• 제1권4호
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• pp.295-307
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• 2017

An innovative system for the alternative continuous wide spectral spatial heterodyne spectrometer (ACWS-SHS) is proposed. The relationship between the ACWS-SHS and the wide spectral spatial heterodyne spectrometer (WS-SHS) at the resolution limit, the spectral range, the grating diffraction efficiency and the interference fringes contrast ratio has been analyzed theoretically. Through the comparison of the theoretical analysis and simulation results, it is found that the two systems for the WS-SHS and the ACWS-SHS have the same resolution limit and spectral range, which are ${\delta}{\sigma}$ and ${\sigma}_{01}$, while in the ACWS-SHS system the critical diffraction efficiency of echelle grating is 68.39% and the critical contrast ratio of interference fringes is 0.4135, which is much better than the performance of the WS-SHS system. Therefore, the ACWS-SHS reduces the high requirements for the precision of equipment and expands the application field of SHS effectively.