Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology

Beijing, China

Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology

Beijing, China

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Gao M.,Beijing Institute of Technology | Gao M.,Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology | Lan T.,Beijing Institute of Technology | Lan T.,Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology | And 4 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

Optical receiving antenna is usually positioned before the detector of an indoor visible light communication (VLC) system in order to collect more optical energy into the detector. Besides optical gain of the antenna, the field of view (FOV) plays also an important role to the performance of a VLC system. In this paper, the signal noise ratio (SNR) and inter-symbol interference (ISI) versus FOV of the antenna are simulated via Line-of-Sight (LOS) and non-Line-of-Sight (NLOS) links within a room with a size of 5m × 5m × 3m. Results show that, the blind area appears while the FOV is less than 40 deg. and the SNR reduces as FOV increases and keeps small when FOV is more than 70 deg. Furthermore, the average power of ISI rises with the increase of FOV, and the rising trend is relatively moderate when FOV is below 50 deg., while there is a rapid increase between 50 deg. and 70 deg. and finally tends to be stable after 70 deg. Therefore, it is practical to determine the FOV of the optical receiving antenna in the scope of 40 to 50 deg. based on the installment of LED lights on the ceiling here so as to avoid the blind area, attain high SNR, and reduce the influence of ISI. It is also worthwhile in practice to provide an identifiable evidence for the determination of FOV of the optical antenna. © COPYRIGHT 2015 SPIE.


Tian Y.,Beijing Institute of Technology | Tian Y.,Shanghai Institute of Electro Mechanical Engineering | Tian Y.,Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology | Xu R.,Beijing Institute of Technology | And 10 more authors.
IEEE Transactions on Antennas and Propagation | Year: 2016

Edge diffraction of a beam combiner will adversely affect the field uniformity in the observation plane. In order to suppress the edge diffraction, the serrated edge design method is proposed. According to the equivalence principle, a field uniformity analysis method was proposed to compute the spatial field distribution radiated from the aperture of a beam combiner. In order to separate the direct wave from diffracted wave, the spatial field is transformed into the time- and angular-domain spectrum by inverse Fourier transform. First, the height of serrations is designed by analog of the equivalent trapezoidal amplitude taper. Then, the number of serrations was designed by the assumption of isosceles and right triangles. Finally, the shape of serrations was designed by changing the interior angle of serrations. A serrated edge design example is also proposed and analyzed. By comparing the field uniformity in spatial, time, and angular domains before and after serrating the edges, the amplitude and phase ripples decrease from 1.85 dB and 12.16° to 0.53 dB and 3.98°, respectively. The results show that the field uniformity is significantly improved. © 2016 IEEE.


Xu R.,Beijing Institute of Technology | Xu R.,Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology | Wang X.,Beijing Institute of Technology | Wang X.,Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology | And 5 more authors.
Applied Optics | Year: 2016

In order to test a direct-detection ladar in a hardware-in-the-loop simulation system, a ladar scene projector is proposed. A model based on the ladar range equation is developed to calculate the profile of the ladar return signal. The influences of both the atmosphere and the target's surface properties are considered. The insertion delays of different channels of the ladar scene projector are investigated and compensated for. A target range image with 108 pixels is generated. The simulation range is from 0 to 15 km, the range resolution is 1.04 m, the range error is 1.28 cm, and the peak-valley error for different channels is 15 cm. © 2016 Optical Society of America.


Hui M.,Beijing Institute of Technology | Hui M.,Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology | Zhou P.,University of Arizona | Su P.,University of Arizona | And 2 more authors.
Applied Optics | Year: 2015

Lenslet array was introduced to an image detector to compensate for low sensitivity. These lenses deviate the light from different incident angles and potentially introduce errors when subpixel accuracy is needed. We investigated the spot centroid position because the angle of incidence changes on a Kodak KAI-16000 image detector with lenslet array. In our experiment, we noticed that there is a cubic dependency on the incident angle. The experimental results show that dependence on the angle of incidence is related to the lenslet array in the Kodak detector used for the pentaprism test. This situation caused an error in spherical aberration on the test surface after integration. The magnitude of the cubic component at incident angle of 14° (equivalent to F/2) is 11.6 μm, which corresponds to a 48 nm rms spherical aberration for the test surface and brings the scanning pentaprism test closer to the principal test while there is a 56 nm rms discrepancy. The discrepancy in spherical aberration between the two tests reduced to 8 nm after this calibration. It also showed the contrast measurement results for the Kodak detector and PointGrey detector. We performed experiments with two different detectors to quantify this effect. © 2015 Optical Society of America.


Chen L.,Beijing Institute of Technology | Chen L.,Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology | Hao J.,Beijing Institute of Technology | Hao J.,Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology | And 4 more authors.
Optics Communications | Year: 2014

A focal length measurement method by fiber point-diffraction longitudinal interferometry is proposed. By applying two different longitudinal displacements for the object point respectively and measuring the corresponding displacements of the image point, the lens focal length is derived by Newton formula. The displacements of the object point are introduced by glass plates with known refractive index and thickness. The corresponding displacements of the image point are measured interfeorometrically based on the modeling of the longitudinal interferometry of two point sources. Experiments and error analysis reveal that this method has an accuracy less than 0.15% under normal laboratory environment. © 2014 Elsevier B.V.


Xu R.,Beijing Institute of Technology | Xu R.,Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology | Shi R.,Beijing Institute of Technology | Shi R.,Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology | And 4 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

Laser echo signal simulator is one of the most significant components of hardware-in-the-loop (HWIL) simulation systems for LADAR. System model and time series model of laser echo signal simulator are established. Some influential factors which could induce fixed error and random error on the simulated return signals are analyzed, and then these system insertion errors are analyzed quantitatively. Using this theoretical model, the simulation system is investigated experimentally. The results corrected by subtracting fixed error indicate that the range error of the simulated laser return signal is less than 0.25m, and the distance range that the system can simulate is from 50m to 20km. © 2015 SPIE.


Tian Y.,Beijing Institute of Technology | Tian Y.,Shanghai Institute of Electro mechanical Engineering | Tian Y.,Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology | Sun G.,Beijing Institute of Technology | And 6 more authors.
Applied Optics | Year: 2014

In order to reduce the complexity of splicing the mirrors of an infrared (IR)/millimeter wave (MMW) beam combiner into a plane, the wavefront division imaging technique (WDIT) was proposed. However, WDIT would lead to the difference of air gap thicknesses among different mirrors, which will further cause the nonuniformity of the MMW field. Simultaneously, there were slots between every two mirrors after the mirror array was spliced and adjusted, which would also affect MMWand IR diffraction. Thus, the aperture field integration method (AFIM) was proposed to compute the MMW near field distribution and the IR far field distribution. The method was validated by comparing the results obtained from the multilevel fast multipole method and experiment. The experimental results showed that the diffraction phenomenon caused by a tilt slot or a hole can approximate that caused by a slot with the width or a hole with the edge diameter along the tilt direction multiplied by cosine of the tilt angle. The variations of both MMW and IR field distributions were caused by three factors: different tilt angles, air gap thicknesses, and slot widths were analyzed by using AFIM in the spatial domain and the time domain. The simulation results showed that the three factors will affect the uniformity of theMMWfield. And the uniformity introduced by the air gap thicknesses was the worst. However, the uniformity still satisfied the requirement for phase error when the variation of the air gap thicknesses was less than 1 mm. Although the three factors would cause the loss of energy and an enhancement in the background noise received by an IR focal plane array, the resolution of the IR system would not be affected. Thus, the WDIT was validated through the above analysis. © 2014 Optical Society of America.


Tian Y.,Beijing Institute of Technology | Tian Y.,Shanghai Institute of Electromechanical Engineering | Tian Y.,Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology | Sun G.,Beijing Institute of Technology | And 6 more authors.
Applied Optics | Year: 2014

The aperture field integration method (AFIM) is proposed and utilized to efficiently compute the field distributions of infrared/microwave (IR/MW) micro-mirror array beam combiners, including the MW near-field distribution and the IR far-field distribution. The MW near-field distributions of single-dielectric-layer beam combiners with 1, 11, and 101 micromirrors are analyzed by AFIM. Compared to the commonly used multilevel fast multipole method (MLFMM) in the computation of MW near-field distribution, the memory requirement and CPU time consumption are reduced drastically from 16.92 GB and 3.26 h to 0.66 MB and 0.55 s, respectively. The calculation accuracy is better than 96%, when the MW near-field distribution is computed. The IR far-field computational capability is validated by comparing the results obtained through AFIM and experiment. The MW near field and IR far field of a circular and a square shape of three-layer micro-mirror array beam combiners are also analyzed. Four indicators Epv, Erms, φpv, and φrmsrepresenting the amplitude and phase variations are proposed to evaluate the MW near-field uniformity. The simulation results show that the increase of beam combiner size can improve the uniformity of the MW near field, and that the square shape has less influence on the uniformity of the MW near field than the circular one. The zeroth-order diffraction primary maximum intensity of the IR far field is decreased by 1/cos2α0times compared to that of the equivalent mirror, where α0is the oblique angle of each micromirror. When the periodic length of the micro-mirror array is less than 0.1 mm, the position of the secondary maximum will exceed the size of the focal plane array. Simultaneously, the half-width of the zeroth-order diffraction primary maximum is less than the size of a single pixel. Thus, IR images with high quality will be obtained. The simulation results show that the AFIM as a unified method can be applied to design, analyze, evaluate, and optimize IR/MW micro-mirror array beam combiners. © 2014 Optical Society of America.


Tian Y.,Beijing Institute of Technology | Tian Y.,Shanghai Institute of Electro Mechanical Engineering | Tian Y.,Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology | Sun G.,Beijing Institute of Technology | And 7 more authors.
Applied Optics | Year: 2014

The design method of an infrared/millimeter wave mirror array type of beam combiner was investigated. The beam combiner was composed of a support plate, air gap, and mirror array. It had two advantages: one was that the size of the beam combiner could beextended bysplicing more mirrors; the other was that the millimeter wave passband could be tuned by adjusting the thickness of the air gap. The millimeter wave and infrared structure was designed by using transmission line theory and optimized by a simplex Nelder-Mead method. In order to analyze the influence of deformation on performance, the mechanical characteristics of the mirrors and support plate were analyzed by the finite element method. The relationship between the millimeter wave transmission characteristics and the air gap was also analyzed by transmission line theory. The scattered field caused by pillars was computed by the multilevel fast multipole method. In addition, the effect of edge diffraction on the near field uniformity was analyzed by the aperture field integration method. In order to validate the mirror array splicing principle and the infrared imaging performance, a prototype of the mirror array was fabricated and tested. Finally, the infrared images reflected by the mirror array were obtained and analyzed. The simulation and experiment results validated the feasibility of the mirror array beam combiner. © 2014 Optical Society of America.


Xu R.,Beijing Institute of Technology | Xu R.,Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology | Shi R.,Beijing Institute of Technology | Shi R.,Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology | And 4 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

LADAR guidance technology is one of the most promising precision guidance technologies. In the aim of simulating the return waveform of the target, a 3D geometrical model of a target is built and mathematical model of target echo signal for imaging LADAR target simulator is established by using the coordinate transformation, radar equation and ranging equation. First, the 3D geometrical data of the object model is obtained by 3D geometrical modeling. Then, target coordinate system and viewpoint coordinate system are created respectively. 3D geometrical model is built in the target coordinate system. The 3D geometrical model is transformed to the viewpoint coordinate system based on the derived relationship between the two coordinate systems. Furthermore, the range information of the target could be obtained under viewpoint coordinate system. Thus, the data of the target echo signal can be obtained by using radar equation and ranging equation. Finally, the echo signal can be exported through corresponding data interface. In order to validate the method proposed in this paper, the echo signal generated by a typical target is computed and compared with the theory solutions. The signals can be applied to drive target simulator to generate a physical target LADAR image. © 2014 SPIE.

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