scholarly journals Research on Focal Length Measurement Scheme of Self-Collimating Optical Instrument Based on Double Grating

Sensors ◽  
2020 ◽  
Vol 20 (9) ◽  
pp. 2718
Author(s):  
Wenchang Yang ◽  
Zhiqian Wang ◽  
Chengwu Shen ◽  
Yusheng Liu ◽  
Shaojin Liu ◽  
...  
Keyword(s):  
Measurement Accuracy ◽  
Focal Length ◽  
Optical Path ◽  
Good Resolution ◽  
Mean Square ◽  
Optical Instrument ◽  
Moiré Fringes ◽  
Measurement Resolution ◽  
Designed Experiment ◽  
Better Than

In this paper, we propose a scheme for measuring the focal length of a collimating optical instrument. First, a mathematical model for measuring the focal length of a collimator with double gratings is derived based on the moiré fringe formula and the principles of geometric optics. Mathematical simulation shows that a slight difference in the focal length of two collimators has an important influence on the imaging law of moiré fringes. Our solution has a good resolution ability for focal length differences within 5‰, especially in the small angle range below 4°. Thus, the focal length of collimators can be measured by the amplification of the slight difference. Further, owing to the relative reference measurement, the measurement resolution at the symmetrical position of focal length is poor. Then, in the designed experiment, a corresponding moiré image at different angles is acquired using collimators with known focal length. The experimental results indicate that the root mean square error (RMSE) of the collimator corresponding to grating angles of 2°–4° is better than 4.7‰, indicating an ideal measurement accuracy of the proposed scheme. This work demonstrates that our proposed scheme can achieve an ideal accuracy in the measurement of a symmetrical optical path.

Focal length measurement by the analysis of moiré fringes using the wavelet transformation

2005 ◽  
Vol 28 (1) ◽  
pp. 33-38 ◽  
Author(s):  
Ching‐Huang Lin ◽  
Chien‐Yue Chen ◽  
Jin‐Yi Sheu ◽  
Ping‐Lin Fan ◽  
Rong‐Seng Chang
Keyword(s):  
Wavelet Transformation ◽  
Focal Length ◽  
Length Measurement ◽  
Moiré Fringes

Scheme design and key technology verification of Narrow Angle Sensor for small body mission

2021 ◽  
Author(s):  
Fenzhi Wu ◽  
Xiao Liang ◽  
Yanpeng Wu ◽  
Yunfang Zhang ◽  
Yuan Zhao ◽  
...  
Keyword(s):  
Autonomous Navigation ◽  
Measurement Accuracy ◽  
Small Body ◽  
Spectral Observation ◽  
Detection Sensitivity ◽  
Composition Analysis ◽  
Processing Unit ◽  
Scientific Observation ◽  
Exploration Mission ◽  
Better Than

<p>   In small body exploration mission, the uncertainty of the target characteristics and the special weak gravitational environment put forward higher requirements for the optical autonomous navigation accuracy of the probe and the detection ability of the navigation sensor. Narrow Angel Sensor(Hereinafter referred to as NAS), as the key instrument of China’s first small body exploration mission, has both optical autonomous navigation function and scientific observation ability, and it must give consideration to both near and far, and achieve breakthroughs in dynamic range, detection sensitivity, pointing measurement accuracy, angular resolution and spectral observation ability. The specific performance is as follows: To capture and track Near Earth Asteroids 2016HO3 from tens of thousands of kilometers, NAS is required to have the ability of point target detection, and the detection sensitivity is better than MV10, and  the accuracy of pointing measurement is better than 1 ″. As the probe approaches the target, NAS must be able to clearly image the shape and surface texture of 2016HO3, so as to obtain the motion parameters such as the spin axis and rotation period of the target. In remote sensing and descending stage, the mission requires NAS to be able to carry out global centimeter scale and landing area millimeter scale multi-spectral observation of the target, and optical navigation uses high-resolution images to construct landmark feature library, so as to realize terrain relative navigation; meanwhile, the image is used to provide data support for the scientific research of the target topography, spectral characteristics and surface material composition analysis.</p> <p>   NAS adopts split design, and the detector part is composed of front door, baffle, focusing optical system, filter wheel, image processing circuit, and motor drive circuit, the algorithm is implemented in the image navigation processing unit. The prototype of the instruments has been developed, and the function and performances such as MTF, detection sensitivity, pointing measurement accuracy etc were verified. The instrument achieved expected design objectives,  and can meet the requirements of optical autonomous navigation and scientific observation for China’s small body exploration mission.</p>

scholarly journals Research on Tuning Fork Dimension Optimization and Density Calculation Model Based on Viscosity Compensation for Tuning Fork Density Sensor

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Hai Yang ◽  
Yue Rao ◽  
Li Li ◽  
Haibo Liang ◽  
Tao Luo ◽  
...  
Keyword(s):  
Real Time ◽  
Measurement Accuracy ◽  
Tuning Fork ◽  
High Viscosity ◽  
Calculation Model ◽  
Online Measurement ◽  
Liquid Viscosity ◽  
Density Calculation ◽  
Model Based ◽  
Measurement Resolution

At present, real-time online measurement of fluid density is of great significance to improve the automation level of petrochemical and food industries. The tuning fork density sensor is widely used because of its characteristics of real-time online measurement, high measurement accuracy, simple structure, and convenient use. The traditional tuning fork density sensor in the market has the disadvantage of low resolution and being susceptible to liquid viscosity, which makes the sensor’s measurement accuracy low and not suitable for the measurement of high-viscosity liquid density. The measurement resolution and antiviscosity interference capability of the tuning fork density sensor are two major indexes to measure the measurement performance of the sensor, among the antiviscosity interference capability refers to the degree to which the measurement results of the sensor are affected by viscosity properties. However, the structural design of the tuning fork density sensor results in the conflict between the measurement resolution and the antiviscosity interference capability of the sensor, and the improvement of one performance is bound to affect the performance of the other. Aiming at the problem of how to balance the measuring performance of the tuning fork sensor, a density calculation model based on viscosity compensation is proposed in this paper. By studying the working principle and structure design of the tuning fork, the vibration characteristics of tuning fork in liquid with different viscosities and densities are modelled and simulated. From the results of simulation analysis, the better set of dimensions with balanced measuring performance is selected. Not only does the structure of the tuning fork have the characteristics of high resonance frequency, but also the measured results are less affected by the viscosity of the liquid. To solve the problem that density measurement is still affected by high-viscosity liquid after tuning fork dimension optimization, in this paper, the partial least square model is used to fit the experimental data of the frequency-density characteristics; then, the density calculation model based on the viscosity compensation is obtained by combining the frequency-viscosity characteristic experiment. Finally, through the performance test experiment comparing with the traditional tuning fork density sensor, the measurement resolution of the improved tuning fork density sensor is as high as 0.0001 g/cm3; within the viscosity range of 180 MPa·s, the accuracy reached ±0.001 g/cm3, and within 480 MPa·s, the measurement accuracy reached ±0.002 g/cm3. When the liquid viscosity reaches more than 10 MPa·s, the improved tuning fork density sensor has better overall measurement performance than the traditional tuning fork density sensor, and both of its measurement resolution and antiviscosity interference capability have been greatly improved.

scholarly journals Compact Laser Collimation System for Simultaneous Measurement of Five-Degree-of-Freedom Motion Errors

2020 ◽  
Vol 10 (15) ◽  
pp. 5057
Author(s):  
Chuang Sun ◽  
Sheng Cai ◽  
Yusheng Liu ◽  
Yanfeng Qiao
Keyword(s):  
Simultaneous Measurement ◽  
Measurement Accuracy ◽  
Measurement Data ◽  
Optical Path ◽  
Degree Of Freedom ◽  
Experimental Setup ◽  
Collimation System ◽  
Optical Configuration ◽  
Series Of Experiments ◽  
The Common

A compact laser collimation system is presented for the simultaneous measurement of five-degree-of-freedom motion errors. The optical configuration of the proposed system is designed, and the principle of the measurement of five-degree-of-freedom errors is described in detail. The resolution of the roll and the horizontal straightness is doubled compared with other laser collimation methods. A common optical path compensation method is provided to detect light drift in real time and compensate for straightness and angle errors. An experimental setup is constructed, and a series of experiments are performed to verify the feasibility and stability of the system. Compared with commercial instruments, the pitch and yaw residuals are ± 2.5 ″ and ± 3.5 ″ without correction, and the residuals are ± 1.9 ″ and ± 2.8 ″ after correction, respectively. The comparison deviations of the horizontal straightness and vertical straightness changed from ± 4.8   μ m to ± 2.8 μm and ± 5.9 μm to ± 3.6 μm, respectively. The comparison deviation of the roll is ± 4.3 ″ . The experimental results show that the data of the five-degree-of-freedom measurement system obtained are largely the same as the measurement data of commercial instruments. The common optical path compensation can effectively improve the measurement accuracy of the system.

scholarly journals NuSTAR observations of rotation-powered pulsars and magnetars

2012 ◽  
Vol 8 (S291) ◽  
pp. 331-336
Author(s):  
V. M. Kaspi ◽  
H. An ◽  
M. Bachetti ◽  
E. Bellm ◽  
A. M. Beloborodov ◽  
...  
Keyword(s):  
Point Source ◽  
Angular Resolution ◽  
Focal Length ◽  
Effective Area ◽  
X Ray ◽  
Large Effective Area ◽  
Better Than

AbstractNASA's NuSTAR observatory is the first focusing hard X-ray telescope. Launched in June 2012, NuSTAR is sensitive in the 3–79 keV range with unprecedented ~17″ FWHM angular resolution above 12 keV, a result of its multilayer-coated optics and 10-m focal length. With its large effective area (900 cm2 at 10 keV), NuSTAR has point-source sensitivity ~100 times better than previous hard X-ray telescopes. Here we describe NuSTAR and its planned work on rotation-powered pulsars and magnetars during its nominal 2-yr baseline mission that has just commenced.

Synthesis，Film Morphology and Performance on Fabrics of a Novel Amino Functional Polysiloxane

2011 ◽  
Vol 239-242 ◽  
pp. 2981-2985
Author(s):  
Liang Xian Huang ◽  
Xi Ya Zhang ◽  
Qiu Feng An
Keyword(s):  
Cotton Fiber ◽  
Evaluation System ◽  
Chemical Structure ◽  
Wafer Surface ◽  
Root Mean Square Roughness ◽  
Film Morphology ◽  
Mean Square ◽  
Atomic Force ◽  
And Performance ◽  
Better Than

A novel polysiloxane bearing (N,N)-dimethyl-γ-aminopropyl-γ-aminopropyl side groups(ASO-2) was synthesized by copolymerization of octamethylcyclotetrasiloxane with (N,N)-dimethyl-γ-aminopropyl-γ-aminopropyl methyl dimethoxysilane and hexamethyldisiloxane. Chemical structure, film morphology and the softening fabric property of ASO-2 were characterized and investigated by IR, 1H-NMR, SEM, atomic force microscope(AFM) and Kawabata evaluation system(KES).The experiment results indicate that ASO-2 can form a hydrophobic film on both the cotton fiber and silicon wafer surface. The ASO-2 film relatively exhibits a non-homogeneous structure and uneven morphology in its AFM images. Consequently, in 2 μm2 scanning field, the root mean square roughness of ASO-2 film reaches to 0.226 nm, which is 2.69 times rougher as compared with that of N-β-aminoethyl-γ-aminopropyl polysiloxane (ASO-1) film. Application experiments indicate though the tactile of ASO-2 imparted on 100% cotton is somewhat rougher than that of ASO-1, the whiteness and wettability of the cotton treated by ASO-2 are better than those by ASO-1.

The Pulsed Thermocouple for Gas Turbine Application

1977 ◽  
Vol 99 (1) ◽  
pp. 1-10 ◽  
Author(s):  
D. Kretschmer ◽  
J. Odgers ◽  
A. F. Schlader
Keyword(s):  
Exact Solution ◽  
Temperature Distribution ◽  
Gas Turbine ◽  
Temperature Rise ◽  
Measurement Accuracy ◽  
Gas Analysis ◽  
Gas Turbine Combustor ◽  
Analogue Circuit ◽  
Good Repeatability ◽  
Better Than

A mechanically pulsed suction thermocouple has been developed. The gas to be measured is sucked through a sonic orifice, thus eliminating the influence of the velocity inside the combustor. The signal from the thermocouple is processed by an analogue circuit. Contrary to the usual approach to the problem of dynamic temperature measurements (i.e., the attempt to find an exact solution to the extrapolation of the temperature rise curve) in this work, a calibration of the probe was done. This calibration showed very little scatter and a good repeatability. The overall measurement accuracy was better than ±1 percent. As a test of application, a partial survey of the temperature distribution within an aircraft gas turbine combustor was done. A satisfactory agreement was observed between temperatures measured by the thermocouple and those determined from gas analysis. In this test the pulse thermocouple proved to be a reliable and fast tool for the measurement of local gas temperatures.

SiC Single Crystal Growth on Dual Seed with Different Surface Properties

2013 ◽  
Vol 740-742 ◽  
pp. 11-14
Author(s):  
Sang Il Lee ◽  
Jung Young Jung ◽  
Mi Seon Park ◽  
Hee Tae Lee ◽  
Doe Hyung Lee ◽  
...  
Keyword(s):  
Surface Properties ◽  
Growth Period ◽  
Single Crystal Growth ◽  
Seed Crystal ◽  
Vapor Transport ◽  
Physical Vapor Transport ◽  
Mean Square ◽  
Transport Technique ◽  
Better Than

SiC crystal ingots were grown on 6H-SiC dual-seed crystal with different surface properties by a PVT (Physical Vapor Transport) technique. And then SiC crystal wafers sliced from the SiC ingots were systematically investigated in order to find out the dependence of surface properties for seed on the polytype formation. While n-type SiC crystals exhibiting the 4H polytype were grown on seed crystal having high root-mean-square (rms) value, 6H-SiC crystals were grown on seed having lower rms value. However, 6H polytype was maintained on on-axis and off-axis seeds during the entire growth period. The crystal quality of 6H-SiC single crystals grown on on-axis seed were revealed to be slightly better than that of 6H-SiC crystal grown on off-axis seed.

Deformation Analysis of Lateral Support of 600mm Aperture Interferometer Mirrors

2011 ◽  
Vol 79 ◽  
pp. 146-150 ◽  
Author(s):  
Zhao Dong Liu ◽  
Lei Chen ◽  
De Hua Yang ◽  
Zhi Gang Han
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Root Mean Square ◽  
Measurement Accuracy ◽  
Wave Force ◽  
Deformation Analysis ◽  
Mean Square ◽  
Axial Distribution ◽  
Square Wave ◽  
Large Aperture

The deformations of the 600mm aperture interferometer mirrors induced by gravity and supporting forces must be controlled strictly to ensure the accuracy of the large aperture interferometer to achieve 63nm. The mirror deformations induced by two types of forces and four axial distribution positions are analyzed respectively by finite element method. And the deformed interference wavefront are simulated by synthesizing deformations of reference flat and test flat mirrors. The maximum deformed interference wavefront formed by the cosine wave force at the middle of the mirrors and the minimum formed by the square wave force at the periphery of the mirrors. The peak to valley value varies 30nm and root mean square value varies 2.8nm between them. The measurement accuracy of large aperture interferometers can be improved by adjusting the force distributions and supporting positions of the mirrors according to the analysis.

Precise Time Measurement Using CTMU

2012 ◽  
Vol 214 ◽  
pp. 232-236
Author(s):  
Xiao Qiong Zuo ◽  
Ya Xian Liu
Keyword(s):  
Measurement Accuracy ◽  
Low Cost ◽  
Time Measurement ◽  
Analog To Digital Converters ◽  
Analog To Digital ◽  
Current Consumption ◽  
Measurement Resolution ◽  
Precise Time

Numerous applications require very precise time measurement. Usually, the measurement accuracy is increased by improve the MCU MIPS. It will take the high cost and current consumption, and the accuracy is limited in the MCU MIPS. Using CTMU channels work in conjunction with Analog to Digital converters, the high precise time measurement with low cost MCU can be achieved, and make the time measurement resolution to 1 nanosecond. CTMU module is available in many Microchip microcontrollers.

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