共查询到20条相似文献,搜索用时 31 毫秒
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All-fiber digital heterodyne interferometry is a laser metrology technique employing pseudo-random codes phase modulated onto
an optical carrier signal. In this heterodyne interferometer system, the optical signal includes signal reflected and transmitted
from the sample, respectively. Compared with the conventional heterodyne interferometry, this enhanced optical system has
much higher measurement sensitivity, and can distinguish the signal which reflected from the front and the rear surface of
the sample. Analysis and simulation for the digital heterodyne interferometry are presented. It takes approximately 4 s to
scan the whole surface with the diameter of 300 mm. The thickness profile of the sample is obtained in the experiment. The
discussion about the experiment is given finally. 相似文献
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报道了光学外差法测量表面起伏精度及横向分辨精度达到0.11nm及4μm。本文采用的是完全共光路外差干涉系统,阐述了它的原理、构造及噪声的影响,并将测量结果与其它商品仪器测量结果作了比较。 相似文献
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Russell B. Pillers Banmali S. Rawat 《International Journal of Infrared and Millimeter Waves》1996,17(11):1809-1820
The nonlinearity of a frequency-ramped single-mode laser source to be used in optical heterodyne interferometry has been investigated. The analysis is based on mode-hopping due to variation in injection current, temperature and mismatch reflections. 相似文献
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希尔伯特变换处理的布里渊散射DOFS的研究 总被引:4,自引:0,他引:4
光时域反射结构的布里渊散射分布式光纤传感器所检测的自发布里渊散射光信号非常微弱,且频带宽度在几十兆赫以上,难以应用普通相干解调方法,提出了基于希尔伯特变换的光相干检测方法,具体采用微波电光调制产生频移参考光和自发布里渊散射光进行相干检测得到光电信号,再应用基于希尔伯特变换的数字信号处理技术对光电信号进行幅度解调,得到了信噪比改善的布里渊散射光谱,从而有利于提高传感器的检测性能, 相似文献
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本文提出的光外差调制法用于提高空间解调低相干光纤传感器峰顶位置的分辨率,由此提高系统的测量灵敏度.未采用光外差调制法前的杨氏空间解调低相干光纤位移传感器的测量灵敏度为0.12μm;而采用后可达0.033μm. 相似文献
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W. Chen R. Rocquet J. Burie D. Boucher 《International Journal of Infrared and Millimeter Waves》1997,18(1):217-232
A submillimeter-wave/far-infrared (SMM/FIR) laser sideband heterodyne spectrometer has been built for molecular rotational
spectroscopy application in the frequency range of 600–3000 GHz. Based on Gaussian optics, optical system of the spectrometer
is designed to be quasi-achromatic and low losses. In this article the optical design and the performance of the spectrometer
are presented. 相似文献
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The heterodyne technique has been applied to three-beam interference, and three interferometer arrangements are discussed. These arrangements are suitable for electronic measurement of optical phase. A three-beam heterodyne interferometer is demonstrated. 相似文献
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一种探测光纤BSBS温敏效应的新方法黄民双(长沙铁道学院长沙410075)刘邦群(武汉大学物理学系武汉430072)ANewDetectionMethodofOpticalFiberThermalySensitiveEfectusingBSBSAbs... 相似文献
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Various optical coherent transient signals in ruby have been examined by using an optical phase sensitive detection (PSD) technique. The PSD is performed by comparing the phase of the heterodyne beat signals obtained by the Stark switching technique with that of a local oscillator whose frequency is equal to the heterodyne beat frequency. The optical FID, two-pulse photon echoes, radiation locked echoes and notched echoes have been detected as υ-mode signals with small u-mode signals probably due to the asymmetry of the inhomogeneous broadening. The dependence of the phase of the radiation locked and notched echoes upon the driving pulses is also examined. The experimental results are in good agreement with theoretical predictions based on Bloch equations. 相似文献
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Raman heterodyne detection is a coherent optical-RF double resonance technique where the optical and RF fields induce coherence within a three level system and a resultant Raman field is measured using heterodyne detection. This approach has been used previously to detect NMR and more recently EPR. In this paper the parameters that affect the amplitude and signal to noise ratio of the Raman heterodyne signals are considered. The power levels in relation to the oscillator strength and dephasing times, the amplitude and spectrum of the laser frequency jitter in relation to the optical homogeneous linewidths and holeburning rates, and the sample properties such as absorption strength and optical quality, are all factors that affect the Raman signal. The presentation is focused on the Raman heterodyne detected EPR of the nitrogen-vacancy pair centre in diamond making comparisons with Raman heterodyne detected NMR signals obtained for rare earth ion systems. RF-RF double resonance studies, RF holeburning and ENDOR, which give information about the hyperfine levels are also reported for the nitrogen-vacancy centre. The resonance frequencies are in agreement with those predicted from the spin Hamiltonian. The factors affecting the lineshapes and relative intensities of the double resonance signals are discussed. 相似文献
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A new technique is presented for measuring the spectral broadening of light that has been multiply scattered from scatterers in motion. In our method the scattered light is detected by a heterodyne receiver that uses a CCD as a multipixel detector. We obtain the frequency spectrum of the scattered light by sweeping the heterodyne local oscillator frequency. Our detection scheme combines a high optical etendue (product of the surface by the detection solid angle) with an optimal detection of the scattered photons (shot noise). Using this technique, we measure, in vivo, the frequency spectrum of the light scattered through the breast of a female volunteer. 相似文献
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G. C. Bjorklund M. D. Levenson W. Lenth C. Ortiz 《Applied physics. B, Lasers and optics》1983,32(3):145-152
Frequency modulation (FM) spectroscopy is a new method of optical heterodyne spectroscopy capable of sensitive and rapid measurement of the absorption or dispersion associated with narrow spectral features. The absorption or dispersion is measured by detecting the heterodyne beat signal that occurs when the FM optical spectrum of the probe wave is distorted by the spectral feature of interest. A short historical perspective and survey of the FM spectroscopy work performed to date is presented. Expressions describing the nature of the beat signal are derived. Theoretical lineshapes for a variety of experimental conditions are given. A signal-to-noise analysis is carried out to determine the ultimate sensitivity limits. 相似文献
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微波电光调制的布里渊散射分布式光纤传感技术 总被引:20,自引:7,他引:13
在分析布里渊散射分布式光纤传感器检测原理的基础上,针对布里渊散射光信号比较微弱且和瑞利散射光之间存在频移的特点,采用微波电光调制产生频率可调的参考光,和后向布里渊散射光进行相干检测,得到放大的布里渊散射光信号,再用高速模拟数字转换和存储叠加进行时序信号处理,最后得到分布式传感信号。给出了各部分实验过程和结果,得出与理论分析一致的布里渊散射光频谱和光强随温度升高而产生变化。实现了25km的分布式温度传感,初步实验结果证明了方案的可行性。 相似文献
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A powerful method for the phase retardation measurement of a reflective liquid crystal cell is presented. The proposed method is based on the heterodyne interferometer theory for probing cell parameters. Due to common-path optical arrangement, a fast measurement with high accuracy and sensitivity was possible. Both theoretical analysis and experimental procedures are presented. The experimental results agree well with that obtained theoretically. 相似文献
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Yukihiro Ishii 《Optics and Lasers in Engineering》1991,14(4-5):293-309
Laser-diode (LD) interferometry based on heterodyne techniques is described. The developments covered include: sinusoidal phase- modulating, distance-measuring feedback and phase-shifting interferometry. The wavelength is controlled by the laser injection current and is continuously or stepwise changed to introduce a time-varying phase difference between the two beams of an interferometer with unbalanced optical path lengths. A feedback interferometer is described with electronics to stabilize the phase shift and to lock the interferometer on a preset phase condition by controlling the injection current of the LD. An automated phase-measuring interferometric system is developed in which the laser current is changed to synchronize intensity data acquisition with the clocks of a charge-coupled device. A typical experimental result shows measurements of the profile of a diamond- turned Al surface. 相似文献
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The effects of quantum confined stark effect (QCSE) and quantum well (QW) thickness on the optical properties of violet InGaN laser diodes (LDs) have numerically been investigated. The simulation results indicated that the QCSE greatly effects the optical properties of LDs, where QCSE relates to the QW thickness and it increases when the QW thickness is wider which leads to deteriorating of the optical proprieties of the violet InGaN LD. The polarization in the active region of the InGaN LD has been estimated by the blue shift of the wavelength and it is found that the blue shift of the wavelength depends on the QW thickness. The major simulation result has shown that the best properties of violet InGaN LD can be obtained with smaller QW thickness, where more carriers can be restricted, stayed and overlapped inside the QW which leads to a larger stimulated recombination rate and optical material gain which in turn increase the output power of the LD; while decreasing the threshold current of the LD. 相似文献