The Dual Optical Comb Ranging (DCR) method has the advantages of large range, fast speed and high precision, which has a wide application prospect in the field of absolute ranging. In this paper, the Mie scattering theoretical model and the key parameters of atmospheric refractive index which affect the ranging accuracy of the DCR system are studied numerically. The effects of the relative size and refractive index of the Mie scattering particles on the ranging accuracy are simulated. The numerical results show that with the increase of the relative size and refractive index, the loss of light energy is greater, resulting in the reduction of the Signal to Noise Ratio (SNR) of the ranging results. The influence of atmospheric refractive index on ranging results is also simulated, and the influence of atmospheric temperature jitter on ranging is 2.9033 μm/(m∙°C), atmospheric pressure jitter on ranging is 8.203 μm /(m∙kPa), atmospheric humidity on ranging is 3.7676 μm for 1m ranging target with 1% humidity jitter, and atmospheric carbon dioxide on ranging is 1.45×10-4 μm /(m∙ppm).
In this paper, we propose a non-contact real-time centroid measurement method for non-cooperative targets, which calculates the coordinates of the centroid point of the motion model in real time at a frequency of 30 Hz. The TOF (Time of flight) camera configuration, working principle and point cloud preprocessing technology including point cloud fusion of the measurement system are presented. Through the XYZ coordinates of the point cloud data, we calculate the centroid point position of the model. Experiments show that the measured centroid point XYZ three-axis accuracy is about 0.1mm.
In this paper, we proposed a high-frequency angular vibration calibration system based on phase modulated laser interferometer technique, which can provide the real-time rotation angle measurement with vibration frequency of up to 1000Hz. The optical configuration, operation principle, and phase generation carrier demodulation (PGC) technique of this calibration system are presented. Both theoretical and experimental results demonstrate that our proposed angular vibration calibration system can realize an angle measurement with an amplitude of 0.3” at angular frequency of 1000Hz.
KEYWORDS: Clouds, 3D modeling, Reconstruction algorithms, 3D metrology, Data modeling, Reverse modeling, RGB color model, 3D acquisition, Surface plasmons, Optical filters
In this paper, a novel method for measuring the projected area of complex 3D objects based on lidar point cloud data is present. To solve the problem of partial data missing in the process of collection, a method of combining Moving Least Squares (MLS) and greedy projection triangulation algorithm for 3D surface reconstruction is proposed. Combined with the MLS method, the problem of greedy projection triangulation method that it requires the point cloud density to change uniformly is made up. The surface data obtained by this method is smoother and the number of holes is reduced, so that the final projected area calculated is much more accurate. The point cloud display platform is written in C++ under Win10 environment. We select PCL to render point clouds and grids and use VTK framework to implement visual interface, which can display the algorithm results of this article.
Fiber optic gyroscope (FOG) has the advantages of small size, light weight, large dynamic range, fast start up and long life. It can be widely used in military fields and civil fields. As the performance of the optoelectronic devices in the FOG varies with the temperature, the performance of the FOG will be affected. In the use of the carrier high speed, the scaling factor error caused by temperature change is the main error of the FOG, its effect on accuracy is much greater than random drift. FOG often needs to work in a wide temperature range, so the scaling factor needs to be modeled and compensated. Because of the temperature error of the scaling factor is very non-linear, the accuracy of using the traditional polynomial fitting method to compensate the scaling factor is poor. The neural network can approximate any continuous function with any desired accuracy, so this paper uses the BP neural network method to compensate the temperature error of the FOG scaling factor. First, this paper analyzes the error mechanism of the scaling factor, and establishes a theoretical model of the temperature error of the scaling factor. Then the FOG scaling factor in the full temperature range is measured, and the temperature error of the scaling factor is modeled and compensated by using the above two methods. It can be seen from the compensation results that the neural network model can get a good compensation effect, and the accuracy is better than the polynomial fitting method.
There is an increasingly urgent need for model attitude measurement technology in fields of urban modeling, aerospace, autonomous driving, etc. Among them, the point cloud registration algorithm is essential. The existing registration algorithms cannot simultaneously meet the requirements of high speed, high precision and large field of view. To this end, this paper proposes a registration algorithm, which combines normal distribution transform (NDT) and iterative closest point (ICP) to perform secondary registration on point clouds. An attitude measurement platform has been built and the LiDAR continuously obtains the point cloud data of the model. Multi-layered voxel and quasi-Newton method were used to accelerate the NDT algorithm, which is used to calculate the transformation matrix of adjacent frames. If the attitude change exceeds the threshold, ICP will be used with the initial solution from NDT. This method combines the high precision of ICP with the high speed of NDT, so that the dynamic model attitude measurement can be in real time under the premise of high precision, and it is suitable for a variety of attitude measurement scenarios with high precision, high speed and large field of view.
In order to accurately evaluate the dynamic performance of inertial devices, this paper proposed an angular vibration test system and method for inertial devices based on heterodyne interference technology. This system is mainly composed of the angular vibration excitation device and the angular vibration measurement device. By installing an angular reflector on the swing table, the dual-frequency laser interferometer (DFLI) can measure the real-time angle value of the swing table, then obtain its amplitude-frequency characteristics with the Fast Fourier Transform algorithm . The experimental results show that the test system can measure angular vibrations exceeding 1000 Hz. Furthermore, the frequency bandwidth of an interferometric fiber optic gyroscope (IFOG) fabricated in our laboratory is evaluated by the angular vibration test system aforementioned, and its cut-off frequency is measured as 375 Hz. Finally, a comprehensive theoretical analysis has been implemented to investigate the uncertainty factors in the DFLI of this system.
An integrated optical chip (IOC) is the phase modulation actuator in a closed-loop interferometric fiber optic gyroscope (IFOG). Research on temperature characteristic of IOC is meaningful for high-precision IFOG working in harsh environment. We focus on the temperature modeling of the IOC modulation phase error. In theoretical analysis, based on the temperature dependence of the IOC equivalent capacitance, a model between IOC modulation phase error and temperature is proposed. Through experiments, the variation tendency of the IOC equivalent capacitance with temperature is first presented. Subsequently, the IOC modulation phase error is demonstrated to be linear with temperature, which verifies the effectiveness of the proposed model. We provide an error research direction of IOC for high-precision fiber optic gyroscopes.
The basic principle of a dynamic goniometer based on fiber optic gyroscope was introduced. According to this principle, the model on uncertainty of angle measurement results was established and the simulation analysis on uncertainty of measurement results was performed. Furthermore, a series of repetitive experiments with this goniometer at different rotational velocities were carried out. Experiments results showed that they were consistent with the uncertainty got from the theoretical analysis when the confidence level was set to 95% and the evaluation model on uncertainty was effective.
Publisher’s Note: This paper, originally published on 18 January 2019, was retracted from the SPIE Digital Library on 24 April 2019 upon verification that an incomplete draft of the paper was submitted and published in which text and figures were omitted, and figures were adapted or copied from the following publications without attribution:
Figure 4: S Svitlov, P Masłyk, Ch Rothleitner, H Hu, and L J Wang, “Comparison of three digital fringe signal processing methods in a ballistic free-fall absolute gravimeter,” Metrologia, Volume 47, Number 6 (2010); https://doi.org/10.1088/0026-1394/47/6/007
Figures 7 and 8: S Svitlov, Ch Rothleitner, and L J Wang, “Accuracy assessment of the two-sample zero-crossing detection in a sinusoidal signal,” Metrologia, Volume 49, Number 4 (2012); https://doi.org/10.1088/0026-1394/49/4/413
In an axial magnetic field (AMF), which is vertical to the plane of the fiber coil, a polarization-maintaining fiber optic gyro (PM-FOG) appears as an axial magnetic error. This error is linearly related to the intensity of an AMF, the radius of the fiber coil, and the light wavelength, and also influenced by the distribution of fiber twist. When a PM-FOG is manufactured completely, this error only appears a linear correlation with the AMF. A real-time compensation model is established to eliminate the error, and the experimental results show that the axial magnetic error of the PM-FOG is decreased from 5.83 to 0.09 deg/h in 12G AMF with 18-dB suppression.
The precise control of the thermal splicing temperature of ZBLAN fiber and silica fiber was guaranteed by theoretical simulation, analysis, and experimental optimization. The thermal splicing model was established, and optimized thermal splicing parameters were obtained based on the simulation results. The thermal splicing parameters were finely repeatedly tuned and optimized further in the thermal splicing experiments according to simulation parameters. The achieved loss was measured to be about 0.3 dB in the thermal splice experiments. The offset thermal splicing method demonstrated a repeatable, low-loss, and promising technique for the splice of ZBLAN fiber to silica fiber.
A novel micro fluid oscillator with a boron diffused resistor is proposed in this paper. The actuation principle is based on the combination of Marangoni effect. The contemporary microfabrication technique enables us to fabricate microheater tiny enough to control temperature so quickly and precisely in micro length scale. The devices exhibiting the Marangoni effect in square channels were designed and fabricated from one silicon substrate and two quartz substrates. And the three substrates were aligned, bonded and packaged for testing. In this actuator there is a pair of micro-heaters to produce a thermal gradient along the slit. The driving wattage is about 0.1W and the resistors can make a temperature difference about 100 degrees during 0.1s with a pulsewidth of 20us for 0.1A current pulses. Then the movement is driven towards the lower temperature direction by the interfacial tension of the air-liquid interface. This micro fluid actuator can play important role in many liquid micro-systems such as in micromotor and micro valve.
The tunable optical filter used for WDM system was fabricated by employed the birefringence of liquid crystal. When the driver voltage changed, the refractive index of the liquid crystal was altered, which inverted to change the effective thickness of the cavity of the filter based on the Fabry-Perot etalon, so the peak of the transmittance was shifted and the filter achieved the tunable performance. The experiment result of the device was achieved to the tunable range from 1534.5nm to 1562.5nm and the full width of the half maximum is nearly 0.8nm and was in agreement with the design one.
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