Yuejin Zhao

Beijing Institute Of Technology, Peping, Beijing, China

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Publications (89)71.33 Total impact

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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.
    SPIE Optical Engineering + Applications; 09/2014
  • Optik - International Journal for Light and Electron Optics 01/2014; 125(1):84-88. · 0.77 Impact Factor
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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.
    Computational Optical Sensing and Imaging; 01/2014
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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.
    2014 IEEE 27th International Conference on Micro Electro Mechanical Systems (MEMS); 01/2014
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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.
    Signal Recovery and Synthesis; 01/2014
  • Optik - International Journal for Light and Electron Optics 12/2013; 124(23):6058-6062. · 0.77 Impact Factor
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    ABSTRACT: A new method of pulse signal de-noising based on wavelet transform and coherent averaging method is proposed. Pulse signal is complex and weak, generally submerged by the interference of baseline drift, motion artifact and high frequency noise. Consequently, it's difficult to measure the heart rate by processing only one single-channel pulse signal, especially when the noise frequency and the pulse signal frequency are in the same frequency range. In this paper, multichannel pulse signal processing based on wavelet transform and coherent averaging is proposed to solve the above problem. First, the detail coefficients and approximation coefficients of each channel signal are obtained by N layer wavelet decomposition, then reconstructing the signal with high layers coefficients as the high frequency noises always exist in low layers coefficients. In this way we can filter out the high frequency interference. Second, the centerline of the upper and lower envelope curve obtained by cubic spline estimation is subtracted from each reconstructed signal so as to eliminate the baseline drift completely. Finally, the heart rate is acquired with the coherent averaging method which results in the noise being offset each other and the pulse signal being enhanced in the frequency range of pulse wave. The pulse signal and three kinds of noise signals simulated with the superposition of different frequency sin signal were analyzed, besides the experiment of six channel pulse signals measured simultaneously based on PhotoPlethysmoGraphy (PPG) were conducted. The simulation and experiment results showed that this method was superior to the traditional single channel.
    11/2013;
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    ABSTRACT: In the development process of satellite control systems and solar sensors, conventional solar simulators can‟t show variations in the solar shape and intensity in the state of solar occultation, so we set up a solar simulation and test platform. A method is put forward to simulate the wavefront error based on deformable mirror (DM). In this paper, the main relevant parameters which describe the atmospheric turbulence are introduced. The statistic characteristics of optical wavefront phase influenced by atmospheric turbulence are presented, and analyzed by the method of Zernike modes. A piezoelectric DM with 109 electrodes manufactured by OKO is used as the wavefront phase modulator. The important technology parameter about the deformable mirror is tested. Owing to the linear superposition, we have a research in the optical influence function and voltage deflection. The method of Karhunen-Loeve function is used in the simulation of optical wavefront, because it is statistically independent and can be expanded into the form of Zernike polynomials. We can get the coefficient matrix of random turbulence wavefront, and then link up with surface of the mirror. According to the relationship between deformation of the mirror and the voltage, we can deduce the voltage control matrix, and change the surface of the mirror as we conceive. The numerical results indicate that wavefront error can be introduced to the distribution maps of solar shape and intensity in different orbital position and any tangent point by DM in the light path.
    11/2013;
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    ABSTRACT: This paper presents a new optical structure which achieves super-resolution by means of changing the complex amplitude of light wave. It also establishes the numerical simulation of the structure. Placed in front of the aperture of optical system, this new structure can modulate the light wave by changing the amplitude transmittance, and also make the central maximum of the Airy Pattern narrower to achieve super-resolution. We analyze modulation effects of many kinds of transmittance function. The numerical simulated result shows that the central maximum of the Point Spread Function (PSF), modulated by transmittance function whose edge value is greater than central value, becomes narrower than that of the idea optical system. It is also concluded that this optical structure is insensitive to different wavelength compared with the phase shifting apodizer, which brings about less chromatic dispersion. This conclusion is extremely useful to realize the super-resolution.
    11/2013;
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    ABSTRACT: In the optical imaging system, deep depth of focus brings larger imaging space, thereby obtaining more information from object space, but also correcting defocus error caused by variety reasons. Thus deep depth of focus has profound significance in the practical application. The information optical imaging system based on the wave-front coding is a general interest among the current research of focal depth extension area. A special designed phase mask been added in the optical system, which could encode object information obtained from the designed focal depth range. By this mean, the OTF and MTF become insensitive to defocussing. Thus equal blurred middle images could be obtained, being processed by phase mask decided by the optical system which was known both by designing and testing and digital image process technology, the final clear image with extended depth of focus could be acquired. In this paper, the detail of a novel image restoration algorithm for the wave-front coding system was discussed. We aim at a specific designed wave-front coding imaging lens, using the edge condition and wavelet transform for an improved Wiener filtering processing. The result of simulation and experimental shown this algorithm could quickly decode the obtained blurred middle image. In the premise of retain more details, this method could product a good image restoration within with whole range of the designed depth of focus. The peak of signal-to-noise (SNR) ratio and the information entropy have been promoted. So does the control of the blurred edge and the ringing effect.
    11/2013;
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    ABSTRACT: Standard instrumentation for the assessment of respiration rate is large and based on invasive method, and not suitable for daily inspection. An optical, simple and non-contact measurement method to detect human respiration rate using lowend imaging equipment is discussed. This technology is based on the visible light absorption of blood, which contains many important physiological information of the cardiovascular system. The light absorption of facial area can be indirectly reflected to gray value of the corresponding area image. In this paper, we acquire the respiration rate through the video signal captured by low-end imaging equipment. Firstly, the color CCD captures the facial area below the eyes and every frame of the video can be separated into three RGB channels. The blue channel is extracted as the research object. Then, we calculate the mean gray value for each image and draw the mean gray curve along the time. Fourier transform can get the frequency spectrogram of the graph, which is filtered through the Fourier filter. The extreme point is the value of the respiratory rate. Finally, an available interface program is designed and we have some volunteers tested. The correlation coefficient between the experimental data and the data provided by a reference instrument is 0.98. The consistency of the experimental results is very well. This technology costs so low that it will be widely used in medical and daily respiration rate measurement.
    SPIE Optical Engineering + Applications; 09/2013
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    ABSTRACT: A new cardiac rate measurement method is proposed. Through the beam splitter prism, the common-path optical system of transmitting and receiving signals is achieved. By the focusing effect of the lens, the small amplitude motion artifact is inhibited and the signal-to-noise is improved. The cardiac rate is obtained based on the PhotoPlethysmoGraphy (PPG). We use LED as the light source and use photoelectric diode as the receiving tube. The LED and the photoelectric diode are on the different sides of the beam splitter prism and they form the optical system. The signal processing and display unit is composed by the signal processing circuit, data acquisition device and computer. The light emitted by the modulated LED is collimated by the lens and irradiates the measurement target through the beam splitter prism. The light reflected by the target is focused on the receiving tube through the beam splitter prism and another lens. The signal received by the photoelectric diode is processed by the analog circuit and obtained by the data acquisition device. Through the filtering and Fast Fourier Transform, the cardiac rate is achieved. We get the real time cardiac rate by the moving average method. We experiment with 30 volunteers, containing different genders and different ages. We compare the signals captured by this method to a conventional PPG signal captured concurrently from a finger. The results of the experiments are all relatively agreeable and the biggest deviation value is about 2bmp.
    Proceedings of SPIE - The International Society for Optical Engineering 09/2013; · 0.20 Impact Factor
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    ABSTRACT: A method that remotely measures blood oxygen saturation through two cameras under regular lighting is proposed and experimentally demonstrated. Two narrow-band filters with their visible wavelength of 660nm and 520nm are mounted to two cameras respectively, which are then used to capture two photoplethysmographic (PPG) from the subject simultaneously. The data gathered from this system, including both blood oxygen saturation and heart rate, is compared to the output of a traditional figure blood volume pulse (BVP) senor that was employed on the subject at the same time. Result of the comparison showed that the data from the new, non-contact system is consistent and comparable with the BVP senor. Compared to other camera-based measuring method, which requires additional close-up lighting, this new method is achievable under regular lighting condition, therefore more stable and easier to implement. This is the first demonstration of an accurate video-based method for non-contact oxygen saturation measurements by using ambient light with their respective visible wavelength of 660nm and 520nm which is free from interference of the light in other bands.
    Optics Express 07/2013; 21(15):17464-71. · 3.53 Impact Factor
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    ABSTRACT: The modified generalized cubic phase mask (GCPM) has recently been applied in wavefront coding systems including infrared imaging and microscopy. In this paper, the stationary phase method is employed to analyze the GCPM characteristics. The SPA of the modulation transfer function (MTF) under misfocus aberration is derived for a wavefront coding system with a GCPM. The approximation corresponds with the Fast Fourier Transform (FFT) approach. On the basis of this approximation, we compare the characteristics of GCPM and cubic phase masks (CPM). A GCPM design approach based on stationary phase approximation is presented which helps to determine the initial parameter of phase mask, significantly decreasing the computational time required for numerical simulation.
    Optics Communications 07/2013; s 298–299:67–74. · 1.54 Impact Factor
  • Feng Wen, Yuejin Zhao, Xiaomei Yu
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    ABSTRACT: To measure glucose accurately, a high sensitivity piezoresistive four-set Wheatstone bridge structure microcantilevers glucose biosensor was developed. The microcantilevers with a piezoresistor were fabricated using a series of bulk silicon processes based on a silicon-on-insulator wafer. An improved Wheatstone bridge readout circuit with voltage closed-loop auto-zero and high-gain magnified functions is proposed. The sensing microcantilever gold-coated surface was functionalised by immobilising a self-assembled monolayer of 4-mercaptophenylboronic acid, the reference cantilever was not functionalised. The relationship between a piezoresistive bridgeout caused by the microcantilevers bending and glucose solution concentration was obtained at 5 and 15 mM. Experimental results demonstrated that the output voltage induced by microcantilevers bending is proportional to the glucose concentrations and the sensitivity is up to 0.1 V/mM.
    Micro & Nano Letters 06/2013; 8(6):298-301. · 0.80 Impact Factor
  • Feng Wen, Yuejin Zhao, Xiaomei Yu
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    ABSTRACT: A kind of novel reflective grating microcantilever based on SOI was designed and fabricated for biosensing. For measuring the extremely low deflections of the microcantilever, a high precision optical readout approach based on diffraction spectrum balancing feedback control was presented. The read out system include a PI M-038 precision motorized rotation stage, a CCD, a 650 nm laser, a fiber, a min fiber GRIN collimator and lens. The practical measurement resolution of the system is up to 1x10-4 deg, that is to say, for a length of 250um microcantilever, the tip measure resolution is up to 0.043nm.
    Nano-Bio Sensing, Imaging and Spectroscopy; 05/2013
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    ABSTRACT: We aim to study the short-wave infrared (SWIR), medium-wave infrared (MWIR), and long-wave infrared (LWIR) imaging ability based on optical readout bimaterial microcantilever focal plane array (FPA) uncooled infrared imaging system. First, the principle of the bimaterial microcantilever sensing and the fabrication of the microcantilever array are introduced. Second, the optical-thermal-mechanical sensing theories based on the FPA are given. Finally, an optical readout microcantilever FPA infrared imaging system is developed for SWIR, MWIR, and LWIR imaging experiments. The experimental results show that the system can acquire the clear images of the SWIR, MWIR, and LWIR targets.
    Optical Engineering 02/2013; · 0.96 Impact Factor
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    ABSTRACT: It has been shown that bimaterial microcantilevers can deform as their temperature changes owing to the absorption of infrared radiation. Considering the principle of the cantilever, there must be a temperature detection limit and the microcantilever will be invalid beyond a tolerable temperature. In the paper, we aim to prove the limit and provide an approach to obtain the tolerable target temperature for infrared imaging. A microcantilever array damage experiment using an infrared laser as target was conducted and a method based on optical reflection and CCD measurement principle was proposed to measure the cantilever's critical deflection angle. Furthermore, the tolerable target temperature based on the imaging system was calculated.
    Optics & Laser Technology 02/2013; · 1.65 Impact Factor
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    ABSTRACT: Students from China are always intelligent but lack of creativity. These are somewhat stereotypes. This is partially because of the reserved or implicit culture. In an objective point of view, it is also because of the limited education resources. In the single assessment criterion education circumstance, students chase for the high marks even without knowing their interests or aptitudes. In a 12-week open experimental course, Optoelectronic Instrument Experiments (OIE), we try to encourage the students to dig their aptitudes and bring them into full play to earn more credits for the course. Self-assessment and mutual-evaluation for technical proficiency, communication skills, collaboration and leadership are carried out for the final evaluation. We also communicate with the students the speciality and skill a qualified engineer needs. We hope to help them prepare themselves for engineering-related jobs in the further.
    Frontiers in Education Conference, 2013 IEEE; 01/2013
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    ABSTRACT: A novel passive single-channel THz imaging system employing a Cassegrain antenna of 390 mm in diameter and Schottky diodes as detecting part, and the cooperation of a high-speed line scanning mirror driven by a crank-rocker mechanism and a frame scanning mirror as two-dimensional optical-mechanical scanning part is described in this paper. The single frame imaging time of the system is only 20s, the field of view (FOV) is 30° × 36°, and the angle resolution is up to 0.6°. The experimental results show that the low cost, simple structure and efficient system can clearly image the human body, and effectively detect dangerous items concealed under the clothes.
    Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2013 38th International Conference on; 01/2013