Yuejin Zhao

Beijing Institute of Technology, Peping, Beijing, China

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Publications (106)96.44 Total impact

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    ABSTRACT: In this paper, we theoretically and experimentally demonstrate that the imaging speed of the optomechanical focal plane array infrared imaging system can be significantly improved by changing the pressure in the vacuum chamber. The decrease in the thermal time constant is attributed to the additional thermal conductance caused by air. The response time will be greatly shortened to about 1/3 time in low vacuum (around ∼10<sup>2</sup> Pa) compared with that in high vacuum. At a chamber pressure of 50 Pa, the "trailing" in the IR image of a moving hot iron is eliminated with negligible deterioration in the image quality. Moreover, infrared images on rapid occurrence events, such as ignition of an alcohol blast burner, lighting and fusion of a tungsten filament, are captured at a frame rate up to 200 Hz. The above results show that the proposed pressure-dependent performance provides a way to improve the system imaging speed and helps to slow down a dynamic event, which is of great value to the uncooled IR imaging systems in practical applications.
    No preview · Article · Dec 2015 · Applied Optics
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    Lei Yang · Ming Liu · Liquan Dong · Yuejin Zhao · Xiaohua Liu
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    ABSTRACT: A new non-contact heart rate detection method based on the dual-wavelength technique is proposed and demonstrated experimentally. It is a well-known fact that the differences in the circuits of two detection modules result in different responses of two modules for motion artifacts. This poses a great challenge to compensate the motion artifacts during measurements. In order to circumvent this problem, we have proposed the amplitude spectrum and phase spectrum adaptive filter. Comparing with the time-domain adaptive filter and independent component analysis, the amplitude spectrum and phase spectrum adaptive filter can suppress the interference caused by the two circuit differences and effectively compensate the motion artifacts. To make the device is much compact and portable, a photoelectric probe is designed. The measurement distance is from several centimeters up to several meters. Moreover, the data obtained by using this non-contact detection system is compared with those of the conventional finger blood volume pulse (BVP) sensor by simultaneously measuring the heart rate of the subject. The data obtained from the proposed non-contact system are consistent and comparable with that of the BVP sensor.
    Preview · Article · Nov 2015 · Optics Communications
  • Zhu Zhao · Mei Hui · Ming Liu · Liquan Dong · Xiaohua Liu · Yuejin Zhao
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    ABSTRACT: Most CCD imaging detectors integrated microlens arrays (MLAs) to increase fill factor and sensitivity. However, they also introduce spot calibration issues with the inconsistency of spot geometry center and intensity distribution center. We setup theoretical and experimental models to research the problem of centroid shifting. According to the Seidel and Zernike coefficients of the optical model, we analyze main aberrations of microlens. In “Chief Ray” and “Centroid” reference frames, centroid shift numerical value is calculated with Geometric Ensquared Energy (GEE). Based on pentaprism test for 8.4 m mirror segment, we conduct spot imaging experiment in interference system. Spots images are obtained, and two-dimensional centroid algorithm processing is performed on them to get the analog experiment values of centroid movements. The results show that the MLA placed in KAI‐16000 imaging detector causes the spot centroid to move. When there is a 14° (or −14°) angle of incident ray, the shifting values are about 1.46 μm in simulation and 2.18 μm in experiment. Our research makes a contribution to the compensation of calibrated error in metrology technology. We also prove that a significant portion of the shift comes from the low order aberration of microlens.
    No preview · Article · Nov 2015 · Optics Communications
  • Feng Wen · Yuejin Zhao · Xiaomei Yu · Yongfeng Ren
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    ABSTRACT: A biosensor with mirror microcantilevers, based on silicon-on-insulator (SOI) was designed and fabricated for biochemical detection. For measuring the extremely low deflections of the microcantilevers, a high precision optical readout approach based on a fiber optical reflective light intensity readout approach were presented. The results demonstrate that microcantilever biosensor has very high sensitivity of 6.26908 mV/nm, and the measurement resolution is up to 0.1998 nm. In the practical measure glucose solution concentration experiments, the results demonstrate that the sensitivity is up to 1.19 mV/μg/ml.
    No preview · Article · Nov 2015 · Optik - International Journal for Light and Electron Optics
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    Cheng Gong · Yuejin Zhao · Liquan Dong · Xuhong Chu · Xiaomei Yu
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    ABSTRACT: An approach named Windowed XOR photography is proposed for optical readout bimaterial cantilever focal plane array (FPA) imaging. It can replace the conventional differential amplifying method for separating the target from the background radiation. Compared with the conventional method, the approach is helpful to reducing image data's bit-width for processing, avoids negative values and data overflow. A novel integrated aspheric optical readout system and digital processing system were developed to evaluate the approach. Comparative infrared imaging experiments were conducted. The results and analyses show that the Windowed XOR photography has preferable effect and performance.
    Preview · Article · Oct 2015 · Optik - International Journal for Light and Electron Optics
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    ABSTRACT: Optical readout method plays a critical role in bimaterial cantilever array sensing system. The common optical readout methods are based on spectral plane filtering. In the paper an all-optical background subtraction readout approach inspired by total reflection and optical lever principle is presented for the bimaterial cantilever array sensing. Comparing with the spectral plane filtering methods the proposed approach eliminates digital subtraction operation by using optical total reflection instead of digital subtraction and avoids spectral filtering operation. An all-optical background subtraction directly-view infrared sensing system was developed to evaluate the approach. The infrared target can be directly acquired by the visible light CCD. The experimental results and analysis show its unique advantages.
    Full-text · Article · Sep 2015 · Optics Express
  • Mei Hui · Ming Liu · Liquan Dong · Xiaohua Liu · Yuejin Zhao
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    ABSTRACT: Multiple synthetic aperture imaging can enlarge pupil diameter of optical systems, and increase system resolution. Multiple synthetic aperture imaging is a cutting-edge topic and research focus in recent years, which is prospectively widely applied in fields like astronomical observations and aerospace remote sensing. In order to achieve good imaging quality, synthetic aperture imaging system requires phase extraction of each sub-aperture and co-phasing of whole aperture. In the project, an in-depth study about basic principles and methods of segments phase extraction was done. The study includes: application of sinusoidal extreme strip light irradiation phase shift method to extract the central dividing line to get segment phase extraction information, and the use of interference measurement to get the aperture phase extraction calibration coefficients of spherical surface. Study about influence of sinusoidal extreme strip phase shift on phase extraction, and based on sinusoidal stripe phase shift from multiple linear light sources of the illumination reflected image, to carry out the phase shift error for inhibiting the effect in the phase extracted frame.
    No preview · Article · Aug 2015 · Proceedings of SPIE - The International Society for Optical Engineering
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    ABSTRACT: In the research of optical synthetic aperture imaging system, phase congruency is the main problem and it is necessary to detect sub-aperture phase. The edge of the sub-aperture system is more complex than that in the traditional optical imaging system. And with the existence of steep slope for large-aperture optical component, interference fringe may be quite dense when interference imaging. Deep phase gradient may cause a loss of phase information. Therefore, it's urgent to search for an efficient edge detection method. Wavelet analysis as a powerful tool is widely used in the fields of image processing. Based on its properties of multi-scale transform, edge region is detected with high precision in small scale. Longing with the increase of scale, noise is reduced in contrary. So it has a certain suppression effect on noise. Otherwise, adaptive threshold method which sets different thresholds in various regions can detect edge points from noise. Firstly, fringe pattern is obtained and cubic b-spline wavelet is adopted as the smoothing function. After the multi-scale wavelet decomposition of the whole image, we figure out the local modulus maxima in gradient directions. However, it also contains noise, and thus adaptive threshold method is used to select the modulus maxima. The point which greater than threshold value is boundary point. Finally, we use corrosion and expansion deal with the resulting image to get the consecutive boundary of image.
    No preview · Article · Aug 2015 · Proceedings of SPIE - The International Society for Optical Engineering
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    ABSTRACT: The structured light illumination method is applied in an optical readout uncooled infrared imaging system to improve the IR image quality. The unavoidable nonuniform distribution of the initial bending angles of the bimaterial cantilever pixels in the focal plane array (FPA) can be well compensated by this method. An ordinary projector is used to generate structured lights of different intensity distribution. The projected light is divided into patches of rectangular regions, and the brightness of each region can be set automatically according to the deflection angles of the FPA and the light intensity focused on the imaging plane. By this method, the FPA image on the CCD plane can be much more uniform and the image quality of the IR target improved significantly. A comparative experiment is designed to verify the effectiveness. The theoretical analysis and experimental results show that the proposed structured light illumination method outperforms the conventional one, especially when it is difficult to perfect the FPA fabrication.
    No preview · Article · Apr 2015 · Optics Letters
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    ABSTRACT: Terahertz (THz) emission from laser-induced air plasma is a well known and widely used phenomenon. We report that when two laser beams from the laser creating two plasma filaments interact with each other, THz absorption is observed. We believe that a change in the refractive index of the plasma causes the THz-wave absorption. The following experimental results reveal that the THz absorption becomes more pronounced with increasing pump power and that the gas species surrounding the femtosecond laser filament can also influence the THz absorption rate. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE).
    No preview · Article · Apr 2015 · Optical Engineering
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    ABSTRACT: The structured light illumination method is applied in an optical readout uncooled infrared imaging system to improve the IR image quality. The unavoidable nonuniform distribution of the initial bending angles of the bimaterial cantilever pixels in the focal plane array (FPA) can be well compensated by this method. An ordinary projector is used to generate structured lights of different intensity distribution. The projected light is divided into patches of rectangular regions, and the brightness of each region can be set automatically according to the deflection angles of the FPA and the light intensity focused on the imaging plane. By this method, the FPA image on the CCD plane can be much more uniform and the image quality of the IR target improved significantly. A comparative experiment is designed to verify the effectiveness. The theoretical analysis and experimental results show that the proposed structured light illumination method outperforms the conventional one, especially when it is difficult to perfect the FPA fabrication.
    No preview · Article · Apr 2015 · Optics Letters
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    ABSTRACT: Wavefront coding (WFC) technology is adopted in the space optical system to resolve the problem of defocus caused by temperature difference or vibration of satellite motion. According to the theory of WFC, we calculate and optimize the phase mask parameter of the cubic phase mask plate, which is used in an on-axis three-mirror Cassegrain (TMC) telescope system. The simulation analysis and the experimental results indicate that the defocused modulation transfer function curves and the corresponding blurred images have a perfect consistency in the range of 10 times the depth of focus (DOF) of the original TMC system. After digital image processing by a Wiener filter, the spatial resolution of the restored images is up to 57.14 line pairs/mm. The results demonstrate that the WFC technology in the TMC system has superior performance in extending the DOF and less sensitivity to defocus, which has great value in resolving the problem of defocus in the space optical system.
    No preview · Article · Apr 2015 · Applied Optics
  • Wei Ma · Yongzheng Wen · Xiaomei Yu · Yun Feng · Yuejin Zhao
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    ABSTRACT: This letter presents an infrared (IR) focal plane array (FPA) with metamaterial absorber (MMA) integrated to enhance its performance. A glass substrate, on which arrays of bimaterial cantilevers are fabricated as the thermal-sensitive pixels by a polyimide surface sacrificial process, is employed to allow the optical readout from the back side of the substrate. Whereas the IR wave radiates onto the FPA from the front side, which consequently avoids the energy loss caused by the silicon substrate compared with the previous works. This structure also facilitates the integration of MMA by introducing a layer of periodic square resonators atop the SiNx structural layer to form a metal/dielectric/metal stack with the gold mirror functioning as the ground plane. A comparative experiment was carried out on the FPAs that use MMA and ordinary SiNx as the absorbers, respectively. The performance improvement was verified by the evaluation of the absorbers as well as the imaging results of both FPAs.
    No preview · Article · Mar 2015 · Applied Physics Letters
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    ABSTRACT: We describe the application of wavefront coding technique for infrared imaging system to control thermal defocus. For traditional infrared imaging system, athermalization is necessary to maintain imaging performance which may increase complexity and cost of the imaging system. Wavefront coding includes a phase mask at the pupil which can re-modulate wave front so as to produce an encoded image. After digital processing, the system is insensitive to defocus. In this paper, the combination of wavefront coding technique and infrared imaging system has been discussed. We report here the optic design of the wavefront coding IR system based on Zemax. The phase mask is designed to ensure that the modulation transfer function (MTF) is approximately invariant in the range of working temperature. Meanwhile, we designed three IR systems to put up contrast experiments. System one and two are designed to compare the influence before and after the insertion of phase mask. System three is designed to compare the imaging performance before and after reducing lens in wavefront coding IR system. The simulation results show that the infrared imaging system based on wavefront coding can control thermal defocus in a temperature varying from -60 degrees C to 60 degrees C, at the same time the weight and cost of optical elements are reduced by approximately 40%.
    No preview · Conference Paper · Sep 2014
  • Zhu Zhao · Mei Hui · Ping Zhou · Tianquan Su · Yun Feng · Yuejin Zhao
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    ABSTRACT: Low order aberration was founded when focused Gaussian beam imaging at Kodak KAI -16000 image detector, which is integrated with lenslet array. Effect of focused Gaussian beam and numerical simulation calculation of the aberration were presented in this paper. First, we set up a model of optical imaging system based on previous experiment. Focused Gaussian beam passed through a pinhole and was received by Kodak KAI -16000 image detector whose microlenses of lenslet array were exactly focused on sensor surface. Then, we illustrated the characteristics of focused Gaussian beam and the effect of relative space position relations between waist of Gaussian beam and front spherical surface of microlenses to the aberration. Finally, we analyzed the main element of low order aberration and calculated the spherical aberration caused by lenslet array according to the results of above two steps. Our theoretical calculations shown that , the numerical simulation had a good agreement with the experimental result. Our research results proved that spherical aberration was the main element and made up about 93.44% of the 48 nm error, which was demonstrated in previous experiment. The spherical aberration is inversely proportional to the value of divergence distance between microlens and waist, and directly proportional to the value of the Gaussian beam waist radius.
    No preview · Conference Paper · Sep 2014
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    ABSTRACT: This paper presents the design, fabrication, and performance of a $256 times 256$ multiband infrared (IR) focal plane array (FPA) using microbimaterial cantilever as the sensitive pixel. Different from traditional uncooled IR FPA that works only at long wavelength IR, the working bandwidth of the presented FPA is extended to full band IR, covering the three IR atmospheric windows of 1– $2.5~mu $ m, 3– $5~mu $ m and 8–14 $mu $ m simultaneously. The multiband performance is attributed to the elaborately designed multiband absorber consisting of a stacked layer of silicon nitride, chromium nanofilm, and gold mirror. The absorbing mechanism of the stacked layer is discussed in detail and testified by experimental results. Images of short-wavelength, middle-wavelength, and long-wavelength IR were captured successfully with the single FPA. The measured sensitivity and noise equivalent temperature difference of the FPA are $0.18~mu $ m/K and 194.7 mK, respectively. [2014-0090]
    No preview · Article · Jul 2014 · Journal of Microelectromechanical Systems
  • Feng Wen · Yuejin Zhao · Xiaomei Yu · Cheng Gong · Jiancheng Yang
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    ABSTRACT: For measuring the deflections of the microcantilever biosensor, a reflective grating microcantilevers based on SDI were designed and fabricated, a high precision optical readout approach based on diffraction spectrum balancing feedback control was presented. The diffraction spectrum image was collected by a 12-bit digital area array monochrome CCD. According to the sum gray value of the image which subtracted each other at the balancing position and bending position to control a high precision motorized rotation stage revolve make the sum gray value remained in the balancing position always, then the motorized rotation stage revolving angle is just the cantilever bend angle. The resolution of motorized rotation stage is 35 x 10(-6) deg, the system practical measurement resolution is 1 x 10(-4) deg, that is to say, for a length of 250 mu m microcantilever, the tip measure resolution is up to 0.043 nm. Measurement results clearly demonstrate that this reflective grating microcantilever biosensor and this read out method have a great potential for biological and chemical applications.
    No preview · Article · Jan 2014 · Optik - International Journal for Light and Electron Optics
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    ABSTRACT: This paper presents the design, fabrication and performance of a 256×256 bimaterial cantilever focal plane array (FPA) which is able to work in the three infrared (IR) atmospheric windows of 1~2.5μm, 3~5μm and 8~14μm simultaneously. The FPA employs a silicon-framed structure by selectively etching away the substrate with Deep Reactive Ion Etching technique, and a stacked layer of chromium and SiNx serves as the multi-band absorber. The images of short wavelength, middle wavelength and long wavelength infrared were captured successfully with the same FPA by combining the Chromium nano-film with silicon nitride as the multi-band IR absorber. The measured sensitivity of the FPA is 0.18μm/K.
    No preview · Conference Paper · Jan 2014
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    ABSTRACT: In the wavefront encoding optical system, a low-resolution sensor is adopted to capture encoded image. Through bi-cubic interpolation and L-R filtering using the PSF as the deconvolution filter, the super-resolution image is achieved.
    No preview · Conference Paper · Jan 2014
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    ABSTRACT: The camera lens effects for deflectometry surface measurements are analyzed. The evaluations of aberration induced errors are based on image simulation. Experiments for verification are undergoing.
    No preview · Conference Paper · Jan 2014