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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Kang Y.,Beijing Institute of Technology | Yang S.,Beijing Institute of Technology | Yang S.,Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology | Brunel M.,Rennes Institute of Physics | And 3 more authors.
Applied Optics | Year: 2017

A dual-frequency CW laser at a wavelength of 1.064 μm is frequency doubled in a MgO:PPLN nonlinear crystal. The fundamental dual-frequency laser has a tunable beat note from 125 MHz to 175 MHz. A laser-diode pumped fiber amplifier is used to amplify the dual-frequency fundamental output to a maximum power of 50 W before frequency doubling. The maximum output power of the green light is 1.75Wwhen the input fundamental power is 12 W, corresponding to a frequency doubling efficiency of 14.6%. After frequency doubling, green light with modulation frequencies in two bands from 125 MHz to 175 MHz and from 250 MHz to 350 MHz is achieved simultaneously. The relative intensities of the beat notes at the two bands can be adjusted by changing the relative intensities at different frequencies of the fundamental light. The spectral width and frequency stabilities of the beat notes in fundamental wave and green light are also measured, respectively. The modulated green light has potential applications in underwater ranging, communication, and imaging. © 2017 Optical Society of America.


Zhao Z.,Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology | Zhao Z.,Beijing Institute of Technology | Hui M.,Beijing Key Laboratory for Precision Optoelectronic Measurement Instrument and Technology | Hui M.,Beijing Institute of Technology | And 4 more authors.
Chinese Physics B | Year: 2017

The point spread function (PSF) is investigated in order to study the centroids algorithm in a reverse Hartmann test (RHT) system. Instead of the diffractive Airy disk in previous researches, the intensity of PSF behaves as a circle of confusion (CoC) and is evaluated in terms of the Lommel function in this paper. The fitting of a single spot with the Gaussian profile to identify its centroid forms the basis of the proposed centroid algorithm. In the implementation process, gray compensation is performed to obtain an intensity distribution in the form of a two-dimensional (2D) Gauss function while the center of the peak is derived as a centroid value. The segmental fringe is also fitted row by row with the one-dimensional (1D) Gauss function and reconstituted by averaged parameter values. The condition used for the proposed method is determined by the strength of linear dependence evaluated by Pearsons correlation coefficient between profiles of Airy disk and CoC. The accuracies of CoC fitting and duces the root-mean-square error (RMSE) by nearlcentroid computation are theoretically and experimentally demonstrated by simulation and RHTs. The simulation results show that when the correlation coefficient value is more than 0.9999, the proposed centroid algorithm rey one order of magnitude, thus achieving an accuracy of ∼ 0.01 pixel or better performance in experiment. In addition, the 2D and 1D Gaussian fittings for the segmental fringe achieve almost the same centroid results, which further confirm the feasibility and advantage of the theory and method. © 2017 Chinese Physical Society and IOP Publishing Ltd.


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.


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.

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