- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Study on the measurement error and scope of analytical gradient model in phase measuring deflectometry
摘要： The existing analytical gradient models in phase measuring de?ectometry (PMD) usually su?er in the ambiguous problem. To solve this problem, simpli?cation/assumption is often given to the surface shape, which causes non-ignorable measurement error in certain situations. In order to analyze the relation between the surface shape and measurement error when simpli?cation/assumption is used, a ray tracing simulation model is developed in this paper. For any given PMD system setup, the relation between the height/slope variations of test surface and measurement accuracy can be carried out. The corresponding experiment work proves the correctness of this simulation model. The increasing of either the height or slope of object will lead to the exponential aggravating of measurement error. For our experiment setup, the measurement gradient error will be less than 0.5% if the ratio of the distance between the LCD (Liquid Crystal Display) screen and the reference plane and the STD (standard derivation) of object height is larger than 200.
关键词： Phase measuring de?ectometry,Error analysis,Ray tracing model,Optical 3D measurement
更新于2025-09-23 15:22:29
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Misalignment correction for free-form surface in non-null interferometric testing
摘要： Unlike rotational symmetric surfaces, free-form surfaces have sophisticated degrees of freedom, therefore, are more difficult to be aligned. In this work, a practical and accurate correction method is proposed for the misalignment removal of the free-form surface in a non-null interferometric testing system based on computer modeling. The misalignment aberrations, introduced by axial location error, rotation error and non-axial attitude error, are modeled and corrected step by step. The axial and non-axial positions of the free-form surface in the computer model are adjusted from the ideal position to the misaligned one, matching the actual positions in experiment for the correction. Since the modeled position are tuned to be consistent with the actual one, all the misalignment aberrations can be removed from the test wavefront with the reconstruction algorithm. Computer simulations are displayed to verify the accuracy of the proposed method. Experimental results after alignment show basic consistency with the results of Taylor Hobson Profilometer, in which the peak-to-valley (PV) value error of the profile line is better than 1/30λ.
关键词： Figure,Surface measurement,Interferometry,Free-form surface
更新于2025-09-23 15:22:29
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Simultaneous measurement of temperature and refractive index based on microfiber Bragg Grating in Sagnac loop
摘要： In this paper, a simultaneous measurement system of temperature and refractive index (RI) is proposed and demonstrated. The dips in the output spectrum of the proposed sensor are formed by the micro?ber Bragg Grating (mFBG) and Sagnac loop. Due to di?erent interference mechanisms, the dual-parameter measurement is realized by mFBG and Sagnac loop with di?erent sensitivities to temperature and RI. Compared with the traditional Sagnac loop sensors, the proposed Sagnac loop with mFBG is much sensitive to surrounding RI. The results show that the temperature sensitivity is 0.033 nm/°C and ?0.015 dB/°C. And the RI sensitivity is 39.30 nm/RIU and 41.51 dB/RIU. The proposed sensor has a simple structure and great potential in biological and chemical ?elds.
关键词： Micro?ber Bragg Grating,Sagnac loop,Dual-parameter measurement
更新于2025-09-23 15:22:29
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Study of a large lateral core-offset in-line fiber modal interferometer for refractive index sensing
摘要： A large lateral core-offset in-line fiber modal interferometer was proposed in order to avoid the relative direction of the two core-offset joints affecting the interference performance. The RI sensing performances of the interferometers with different arm lengths were evaluated and compared with the small core-offset ones. The simulation and experimental results showed that the power remaining in the core mode decreased from 25 to 0.002% after the input light passing through the first core-offset joint as the core-offset displacement increased from 6 to 40 μm. Thus, the interference between the core mode and cladding mode within the enlarged core-offset interferometer was suppressed, and meanwhile the interference within the cladding modes was dominated. As the core-offset displacement was simply enlarged from 6 to 40 μm, the RI sensitivity was greatly improved from 43.97 to 123.40 nm/RIU. The proposed sensor is a cost-effective solution for RI sensing purpose, and exhibits the advantages of high sensitivity, simple structure and easy fabrication with only a fusion splicer.
关键词： Fiber modal interferometer,Core-offset,Optical fiber sensor,Refractive index measurement
更新于2025-09-23 15:22:29
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Noise-optimized ultrastable low-noise current amplifier
摘要： We have developed a noise-optimized ultrastable low-noise current amplifier (ULCA) aimed at reducing the uncertainty at low currents. It involves a thin-film resistor network with 6.75 GΩ at the high-ohmic path which reduces the noise level to 1.6 fA/√Hz. Noise investigations as well as short-term and long-term stability studies were carried out. The stability of the input current gain was measured using a cryogenic current comparator at ±6.1 nA. Methods for investigating the measurement accuracy at low input currents of about 100 pA at a level of below one part in 10^7 are introduced and experimentally verified. The performance of the noise-optimized ULCA is compared with that of the standard variant introduced in 2014. It is shown that the reduced noise floor is achieved without impairing the stability of the transresistance.
关键词： low-current measurement,cryogenic current comparator,current amplifier,stability,noise optimization
更新于2025-09-23 15:22:29
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Measurement-device-independent and arbitrarily loss-tolerant verification of quantum steering
摘要： We propose a method to verify quantum steering for two-qubit states with an arbitrary amount of null results when both the steering and steered parties cannot be trusted. We converted the steering inequality proposed in a recent article [Phys. Rev. X 2, 031003 (2012)] to a corresponding measurement-device-independent steering criterion that depends on the heralding efficiency of the steering party, number of measurement settings, and imperfection of the state preparation. As a result, for a relative frequency of valid measurement outcomes ηH, the steering can be verified using a number of different measurement settings larger than 1/ηH and maximally entangled states. Furthermore, steerability is guaranteed as long as the measurement efficiency of the steered party is nonzero. Our result is useful for loss-tolerant and measurement-device-independent steering tasks.
关键词： two-qubit states,loss-tolerant,quantum steering,measurement-device-independent,heralding efficiency
更新于2025-09-23 15:22:29
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[IEEE 2018 Asia Communications and Photonics Conference (ACP) - Hangzhou, China (2018.10.26-2018.10.29)] 2018 Asia Communications and Photonics Conference (ACP) - A code-free optical undersampling technique for broadband microwave spectrum measurement
摘要： A novel broadband microwave (MW) spectrum measurement (BMSM) scheme based on code-free optical undersampling and homodyne detection is proposed. The fully analog generation of optical pulses with a far-less-than-Nyquist rate is only through modulating cascaded electrooptical modulators by a single RF tone instead of any high-speed coding sequence modulation. Homodyne detection will reduce the analysis bandwidth of BMSM and enhance the detection performance of weak signal. A multi-band signal with 20 GHz spectral range and SNR = 61 dB is used to investigate the BMSM performance of this scheme, and the results show good performance for BMSM. The potentials for further optimization in practice are also discussed.
关键词： homodyne detection,optical undersampling,microwave spectrum measurement
更新于2025-09-23 15:22:29
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<i>β</i> -Ga <sub/>2</sub> O <sub/>3</sub> thin film grown on sapphire substrate by plasma-assisted molecular beam epitaxy
摘要： Monoclinic gallium oxide (Ga2O3) has been grown on (0001) sapphire (Al2O3) substrate by plasma-assisted molecular beam epitaxy (PA-MBE). The epitaxial relationship has been confirmed to be [010](ˉ201)β-Ga2O3||[1ˉ100](0001)Al2O3 via in-situ reflection high energy electron diffraction (RHEED) monitoring and ex-situ X-ray diffraction (XRD) measurement. Crystalline quality is improved and surface becomes flatter with increasing growth temperature, with a best full width at half maximum (FWHM) of XRD ω-rocking curve of (ˉ201) plane and root mean square (RMS) roughness of 0.68° and 2.04 nm for the sample grown at 730 °C, respectively. Room temperature cathodoluminescence measurement shows an emission at ~417 nm, which is most likely originated from recombination of donor–acceptor pair (DAP).
关键词： CL measurement,β-Ga2O3,sapphire substrate,PA-MBE,crystalline quality
更新于2025-09-23 15:22:29
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Highly compact vector bending sensor with microfiber-assisted Mach-Zehnder interferometer
摘要： A low-cost and highly compact fiber-optic vector bending sensor component is proposed and experimentally demonstrated for vector bending sensing. A segment of microfiber tapered from standard single-mode fibers (SMFs) is spliced between two SMFs with pre-designed lateral offset to construct a sandwich type Mach-Zehnder interferometer of 243.32 μm in length. Sensing performances of the proposed vector bending sensor is theoretically analyzed in detail. As the applied curvature increases from 0.3873 m-1 to 3.0 m-1, the transmission spectra of the proposed sensor show distinct linear wavelength shift sensitivities for different directions, the maximum of which is up to 3.419 nm/m-1. Besides, temperature test indicates that the proposed sensor possesses a low temperature cross sensitivity of 33.71 pm/°C, which ensures its applicability for practical uses in temperature-fluctuated environment. Hence, our proposed vector bending sensor possesses such desirable merits as high sensitivity, compact size, low thermal crosstalk, low cost and orientation-dependent spectral response.
关键词： Vector bending sensor,Mach-Zehnder interferometer,Lateral core-offset,Curvature measurement
更新于2025-09-23 15:22:29
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A New Algorithm for Blood Flow Measurement Based on The Doppler Flow Spectrogram
摘要： The blood ?ow is traditionally obtained by multiplying the cross sectional area of the blood vessel and the average blood speed in the cross section, or is given by the integral of the product of the cross section and blood velocity of each element. However, both methods are affected greatly by the measurement precision of the area and velocity. A new algorithm, which is based on the Doppler blood ?ow spectrogram, is proposed to measure the blood ?ow in this paper. In the algorithm, the blood ?ow is calculated according to the double integral of a Doppler blood ?ow spectrogram. To verify the feasibility of the proposed algorithm, experiments have been performed on the Doppler blood-mimicking system KS205D?1 using the SonixTouch ultrasonic system. In addition, linear-regression analysis is carried out to observe the correlation factors between the experimental values and real values of different ?ow rates. Experimental results show that the calculated values and real values correlate signi?cantly (r > 0.969, P < 0.0000001). Experimental results both on males and females also veri?ed the proposed algorithm (r > 0.915, P < 0.00053). Hence the proposed algorithm is proven effective for relative mean blood ?ow measurement. Due to the special structure of the human brain, it is dif?cult to measure the cross sectional area of blood vessel with ultrasound imaging. In this algorithm, there is no need to measure the cross sectional area of the blood vessel. Therefore, the proposed algorithm has the potential to be a new method for clinical ultrasonic blood ?ow measurement, especially cerebral blood ?ow measurement.
关键词： Blood ?ow measurement,Doppler blood-mimicking system,Doppler spectrogram,linear-regression analysis
更新于2025-09-23 15:22:29