This PDF file contains the front matter associated with SPIE Proceedings Volume 7157, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

A phase-shifting interferometry (PSI) using a multi-longitudinal-mode blue laser diode was developed. Since the longitudinal modes of a laser diode are located almost at even interval and changes synchronously with the injection current, by setting an optical path difference between two arms of an interferometer in such a way that makes the contrast of interferogram to be a maximum, the phase shift required for PSI can be obtained by changing the injection current. Moreover, in such a condition, the PSI system works even mode hops occur. Theory and experimental results for measuring the transmitted wavefront of an aspheric DVD pickup lens are presented.

A tunable optical filter (TOF) based acetylene sensing system is proposed in this paper. By modulating the wavelength of TOF within the width of one absorption line of acetylene, both the sensitivity and selective sensing properties of the system for sensing acetylene have been much improved. Approximate linear calibration curves in sensing acetylene is obtained by experiments. The minimum detectable acetylene concentration of 5ppm is also achieved by experiments. The proposed system has great potential in developing mixed-gas sensing system.

The stabilization of a multiplexed optical fiber interferometer system for on-line displacement precision measurement with a simple electric feedback loop is presented. Based on the characteristics of fiber Bragg gratings, the multiplexed optical fiber interferometer system includes two independent optical fiber Michelson interferometers of which the optical path is almost overlapped. One interferometer is used for the stabilization while the other interferometer is used for the measurement. A feed back signal from the feedback loop is driving a tube PZT on which one arm of the fiber interferometer is wounded. The phase-shift in the two arms of the interferometer resulting from the temperature fluctuations and other types of environmental disturbances is compensated. The bandwidth of the feedback loop is 5kHz. This makes the multiplexed fiber interferometer system stable enough for the on-line precision measurement. An active phase tracking technique is applied for signal processing to achieve high resolution. The measurement resolution of the system is less than 2nm.

A new type of fiber optical current sensor was designed. The sensing head was made by holding a fiber Bragg grating (FBG) on a giant magnetostrictive material (GMM) rod along the axial direction. The sensing head was put into one of the air gap of two silicon plate magnetic cores wound by enameled cable. In order to improve the linearity of the sensor, another silicon plate core with coil was inserted into the other air gap to provide a biased magnetic field for the Terfenol-D rod. The Terfenol-D rod was elongated in the magnetic field varying with the measured current and the strain caused the shift of the center wavelength of FBG. In certain biased magnetic field, the relationship between the measured current and the wavelength shift is linear. Experimental results show that the linear tuning range of FBG is 0.07nm when the measured current of the winding is 0~3A. The corresponding measurable current of straight conductor is 0~ 2313.07A on the assumption that the distance between the axis of the straight conductor and the GMM rod is 10mm.

CdTe/CdS core-shell quantum dots (QDs) with 12 nm in diameters were synthesized in water, and Au nanoparticles (AuNPs) with 25nm in diameters were prepared by reduction of sodium citrate. Compared with the fluorescent of CdTe core QDs, the fluorescent of CdTe/CdS core-shell QDs was increased about one times, which suggested the advantage of CdTe/CdS core-shell QDs in fluorescence application. It was confirmed that the fluorescence emission spectrum of CdTe/CdS QDs and the UV-Vis absorption spectrum of AuNPs had an obvious overlap, which indicated that a novel DNA probe based on fluorescence resonance energy transfer (FRET) from CdTe/CdS QDs donors to AuNPs acceptors could be designed. 3'-SH-DNA were assembled onto the surface of AuNPs by Au-S bond (Au-DNA), and CdTe/CdS QDs were linked to 5'-NH2-DNA (partly complementary with 3'-SH-DNA) by Schiff's reaction (CdTe/CdS-DNA). Then, the distance between donors and acceptors of DNA probe was controlled within 1-10 nm by hybridization of CdTe/CdS-DNA and Au-DNA, which resulted in a FRET from CdTe/CdS QDs to AuNPs according to Forster theory, so the fluorescent of probe was extremely decreased compared with CdTe/CdS-DNA. The detection ability of this novel probe was investigated by fluorescence emission spectrum when target DNA (completely complementary with 3'-SH-DNA) existed.

Oxygen detection techniques are essential for marine environment and ecology researches. In this paper, the development of luminescence intensity-based sensor system for dissolved oxygen (DO) measurement is presented. The sensor film consists of tris(2,2-bipyridyl)ruthenium(II) (Ru(bpy)3Cl2) as photosensitive indicator which is immobilized within the mixture of tetraethoxylsiane (TEOS) and methyl triethoxysilane (MTEOS) membrane. The laboratory experimental results show that the ratio of the fluorescence intensity of the sensor correlates well with DO concentration from 0 to 32.96 mg/l. Depending on the charge-coupled device (CCD) camera used, the proposed system can monitor the 0.9×0.9 cm areas with 9×9 μm resolutions and it can be used for oxygen distribution measurement in spatial and temporal scale for undersea monitoring applications.

In order to detect the plant's nitrogen content in real-time, a wireless crop growth monitor is developed. It is made up of a sensor and a controller. The sensor consists of an optical part and a circuit part. The optical part is made up of 4 optical channels and 4 photo-detectors. 2 channels receive the sunlight and the other 2 receive the reflected light from the crop canopy. The intensity of sunlight and the reflected light is measured at the wavebands of 610 nm and 1220 nm respectively. The circuit part is made up of power supply unit, 4 amplifiers and a wireless module. The controller has functions such as keyboard input, LCD display, data storage, data upload and so on. Both hardware and software are introduced in this report. Calibration tests show that the optical part has a high accuracy and the wireless transmission also has a good performance.

An estimation model of the soil organic matter content has been built based on NIR spectroscopy and a portable soil organic matter detector based on optical sensor is developed. The detector uses a micro processor 89S52 as the Micro Controller Unit (MCU) and consists of an optical system and a control system. The optical system includes a 850nm near-infrared lamp-house, a lamp-house driving-circuit, a Y type optical fiber, a probe, and a photoelectric sensor. The control system includes an amplified circuit, an A/D circuit, a display circuit with LCD, and a storage circuit with USB interface. Firstly the single waveband optical signal from the near-infrared lamp-house is transferred to the surface of the target soil via the incidence fibers. Then the reflected optical signal is collected and transferred to photoelectric sensor, where the optical signal is conveyed to the electrical signal. Subsequently, the obtained electrical signal is processed by 89S52 MCU. Finally, the calculated soil organic matter content is displayed on the LCD and stored in the USB disk. The calibration experiment using the estimation model of the soil organic matter is conducted. The decision coefficient (R2) reaches 0.9839 between the measured data by the soil organic matter sensor and by the laboratory chemistry method.

The growth status of crops varies in different parts of any field. Currently, the most frequently used method to measure the crop growth status is based on the reflectance of visible light and near infra red (NIR), for the reason that using visible light exclusively is not satisfactory. However, the efficiency of multi-spectral detectors is so low that it has been a bottle-neck in the application of precision agriculture. Hence, to improve the efficiency of detecting crop growth status is vital to the development and popularization of precision agriculture. A multi-spectral camera, which is sensitive to NIR, red and green lights is introduced in this article to solve this problem, with a CMOS device as the imaging unit, an FPGA as the controlling unit and a CompactFlash card as the storage unit. The FPGA is logically divided into several independent modules, which are CMOS controlling module, RAM controlling module and MCU controlling module, so as to implement the function of controlling the whole system. The CMOS controlling module which is functionally the signal generating module is used to generate the waveforms for the CMOS imaging device and to control the on-chip AD converter. The RAM controlling module and CF card controlling module are respectively used to control the storage of the digital data into RAM and into CompactFlash card. Moreover, this paper includes the design of the hardware and the configuration of the CMOS device which is used to optimize the results of the pictures taken. At last, the work to be done to optimize the camera is introduced.

The structure and working mechanism of a photoconductive photodetector are compared with a p⁺-i-n⁺ (PIN) photodiode and a metal-semiconductor-metal (MSM) photodetector which is regarded as two back-to-back Schottky barrier photodiodes. Because a photoconductive photodetector has the features of high critical field strength, especially no junction capacitance and no dead zone, it has the main merits of high signal-noise ratio, ultrafast response and high quantum efficiency. We fabricate two photoconductive photodetectors in a lateral configuration on a semi-insulating (SI) gallium arsenide (GaAs) wafer, which wavelength range of response is from UV to 1.73μm due to two-photon absorption. It is shown by the volt-ampere characteristics curve that the dark leakage current of 30μm-gap SI GaAs photoconductive photodetector at a bias field of 66 V/cm is less than 1.2 μA. Our experiment has demonstrated that SI GaAs photoconductive photodetectors are noteworthily superior to high-speed Si PIN photodetectors to measure ultrashort pulse lasers with the properties of ultrafast response, ultrawide spectral range, high signal-noise ratio and ease of fabrication.

Bi₄Ge₃O₁₂ magneto-optic crystal was chosen as sensitive materials, and a current sensor based on Faraday rotation of materials was designed. A ferromagnetic collector with an air gap and feedback windings were utilized in the sensor to construct a closed-loop current sensor. The magneto-optic crystal showed stronger magneto-optic effect and smaller temperature coefficient when it was exposed to the light, which was produced by a semiconductor laser with a working wavelength of 655nm. The ferromagnetic collector was used to collect the magnetic field generated by the measured current. The collector could greatly reduce the influence of the position variation of the conductor on the output. The measurement system was a closed-loop system due to introducing the negative feedback coil to the measuring system, so the linear range, linearity, temperature stability and dynamic characteristic index of the sensor were improved greatly. The principle of this sensor was introduced in detail. The structure of this sensitive component, as well as the signal conditioning circuit, was given. Some experimental data and the interpretation of these data were presented.

Intra-body Body Communication (IBC) is a communication technology in which human body is used as a signal transmission medium. Due to its unique characters, IBC technology is proposed as a novel and promising technology for personal area network (PAN), computer network access, implant biomedical monitoring, human energy transmission, etc. In this paper, investigation has been done in the computer simulation of the electrostatic coupling IBC by using the developed finite-element models, in which (1) the incidence and reflection of electronic signal in the upper arm model were analyzed by using the theory of electromagnetic wave, (2) the finite-element models of electrostatic coupling IBC were developed by using the electromagnetic analysis package of ANSYS software, (3) the signal attenuation of electrostatic coupling IBC were simulated under the conditions of different signal frequency, electrodes direction, electrodes size and transmission distance. Finally, some important conclusions are deduced on the basis of simulation results.

We describe and validate an automated methodology based on PPI to extract endmembers from images and distinct the according endmembers. Four main steps are:1)project the raw image cube to its most spectral dimensions and non-noise components by minimum noise fraction (MNF) technology; 2) use the set of spectrally distinct pixels produced by MNF as skewers for PPI, generates a list of candidates from which final endmembers can be selected; 3) an automatic selection procedure based on K-means clustering is consequently performed to determined the centriod of endmenbers. 4) linear spectral mixing model (LSMM) is used to estimate mixing coefficient. And root mean square error (RMSE) reflects the accuracy of decomposition. We use the methodology to investigate the unique properties of hyperspectral data and how spectral information can be used to identify mineralogy with the Airborne Visible/infrared imaging Spectrometer (AVIRIS) hyperspectral data from Cuprite, Nevada.

Fiber-optic temperature sensors offer unique advantages, such as immunity to electromagnetic interferences, stability, repeatability, durability against harsh environments, high sensitivity and resolution, and fast response. Therefore, optical fiber sensors have been widely adopted and applied in various areas for temperature measurements. It has been demonstrated that by using multimode interferences in a segment of multimode fiber, wavelength-encoded fiber optic temperature sensing can be achieved. The advantages of this kind of temperature sensors include the extremely simple structure and the ability for high-temperature measurements. In this work, we investigate the interference of core mode and cladding modes in double cladding fibers. Analysis and simulations are carried out in order to identify the optimal parameters of the temperature sensor. Practical design of the multimode interference based optical fiber temperature sensors is investigated, and sensing probes are fabricated and tested. The design details, temperature measurement experiments, and test results are presented in this paper.

By monitoring of the emitted signal from a sample while varying the excitation wavelength, emission wavelength or both of them, fluorescence spectroscopy has become a powerful diagnostic technology. Fluorescence spectrometers can be used to measure and record the fluorescence spectra of a given sample, and have been successfully applied in different areas including biology, biochemistry, chemistry, medicine, environmental science, material science, food industry, and pharmaceutical industry. In order to increase the flexibility and applicability of conventional fluorescence spectrometers, we design an optic fiber probe for conducting the UV/Vis excitation light to a sample under study, and for collecting the fluorescence produced by the sample. Different excitation/emission fiber bundle arrangements have been fabricated and their performances have been evaluated and compared. Fiber adaptors which can be used for different commercial fluorescence spectrometers are also developed. In order to achieve space-resolved fluorescence spectroscopic measurements, we connect the fiber probe to a microscope which is mounted on a 3D traverse stage. Experiments and measurement results using the space-resolved fiber optic fluorescence spectrometer are presented in this paper.

A wavelength encoded optical fiber sensor using a three-segmented fiber structure is proposed. The device consists of a coreless silica fiber (CSF) which is coated with a thin film and spliced between two standard single-mode fibers (SMFs), forming a SMF-CSF-SMF (SCS) structure. When light is transmitted from the SMF into the CSF, the LP01 mode in the SMF is coupled to the LP0n modes, and a multimode interference occurs in the CSF. These modes interact with the thin film, hence the thickness and refractive index of the thin film can affect the modal interference. We analyze the transmission spectra of the SCS structure to obtain the characteristics of the sensor including sensing sensitivity. Numerical simulations are carried out by using the Beam Propagation Method (BPM) to investigate the multimode interference in the SCS. Two different conditions are considered in our studies: 1) changing the refractive index of a fixed-thickness film, and 2) varying the film thickness with certain refractive index. It has been found that the wavelength corresponding to the minimum output power increases 0.33509 nm when the refractive index changes every 0.01 from 1.33 up to 1.40, and 6.760 nm when the thickness enhances form 0 to 1000 nm. The trend of the raise is mostly linear for the former simulation, but gets slower and slower for the latter. The SCS structure can serve as a fiber platform for non-labeling bio-sensing when a bio-film is coated to the CSF.

The observed object images are seriously blurred because of the influence of atmospheric turbulence. The deconvolution is required for object reconstruction from turbulence degraded images. The wavelet transform provides a multiresolution approach to image analysis and processing. We consider a wavelet-based adaptive edge-preserving regularization deconvolution (WbARD) scheme for image restoration problems. This is accomplished by first casting the classical image restoration problem into the wavelet domain. We consider the behavior of the blur operator in the atrous wavelet domain. Then, we are able to adapt quite easily to scale-varying and orientation-varying features in the image while simultaneously retaining the edge preservation properties of the regularization. Experimental results show that the WbARD algorithm produces good performance in comparison to standard direct restoration approaches for turbulencedegraded images.

Side polished fiber Bragg grating (SPFBG) is made as a side of cladding of a FBG is polished just to remain several micrometers by the a side polishing method, such as a method with a motor-driven polishing wheel. The response of Bragg wavelength of SPFBG to the refractive index of material overlaid on the polished area of SPFBG was investigated by both theoretical calculation and experiments. Both calculation and experiments showed that the Bragg wavelength of side polished FBG would shift to the longer as the refractive index of the overlaid material increased. The sensitivity of SPFBG to the refractive index of material overlaid on the side polished area could be used for wavelength tuning of FBG or as refractive index sensor.

In this paper, we consider a SPR sensor based on D-type optical fiber with bimetallic combination. In pursuit of both higher sensitivity and larger operating range, firstly, we separately analyze the influence of parameters such as the length of coating L, the incident angle θ and the thickness of Au-coating layer d. when the optimum parameters of sensor are determined, we analyze the performance of the sensor with different bimetallic combination consist of Au, Ag, Cu and Al. Lastly, we can get a conclusion that the sensor with L=5mm,d=25nm, θ=88° and Au-Ag at x=0.8 can provide the best performance in terms of the sensitivity and operating range.

In this paper, we present a demodulation of Fabry-Perot pressure sensor method based on radial basis function network(RBF). RBF network is a kind of three layers frontal feedback neural network with single connotative layer. It is proved that RBF is able to approach random continuous function with random precision. The cavity length variation is simulated from 473 to 483 µm with the step of 0.5 µm and the simulation result shows that the relative error of this new method is less than 0.02% and the maximum absolute error is less than 0.1 µm. The MEMS Fabry-Perot pressure sensor is also demodulated by the experiment. In the experiment, we change the pressure from 0 to 2 MPa with the step of 0.1 MPa. The experimental result shows that its linearity of the cavity length versus pressure achieves 0.98858 and the standard deviation between measured pressures and real pressures is less than 0.05 Mpa. By the experiment we can see that, this RBF network method can obtain upper precision and can reach the practice demand. This new method adapts to the practice demand with its higher resolution and less calculation time.

Marine plankton play an important role in ocean web structure and global environment change. As an alternative to traditional sampling methods, real time imaging systems are particularly useful in studying the abundance and behavior of plankton in the appropriate spatial and temporal scales at high sampling rate. In this paper, the design of a noninvasive, high resolution, low power consumption optical imaging device is presented. The device is designed in a compact size and this makes it suitable to be deployed on underwater vehicle platforms for plankton monitoring. The reported imaging system is a balanced compromise of object distance, focal length of the lens, and the coverage of the sampling area. The results of laboratory evaluation of the combination of different parameters of the optical lens for plankton monitoring are presented. Light illumination based on light emitting diode (LED) is investigated. It is showed that the system is capable of obtaining relatively good resolution images at high sampling rate that allow quantification of the plankton in the appropriate spatial and temporal scales.

We propose a POTDR setup and investigate the Rayleigh scatter and Fresnel refection. A piezoelectric polarization controller (PPC) is applied in this setup. Based on the transfer matrix theory of the PPC, the state of polarization (SOP) of the Fresnel reflection is analyzed under different temperature. In the experiment, we find that when any part of the fiber is affected by the temperature, the SOP of Fresnel reflection will be changed.

This article is to introduce a newly developed method to measure three-dimensional displacement by only a single camera. To measure the 3-D displacement of the two objects A and B, two lighting diodes are fixed on object A. A convex and a translucent screen are fixed on object B, a CCD camera is joined together with the screen. The lighting diodes project two faculae on the screen throgh the lens. The position of the faculae can be detected by the CCD camera. The 3-D displacement of A and B can be calculated according to the position of faculae.

Satellite serving offers a potential for extending the life of satellites and reducing launching and operating costs. Proximity operations are necessary for purpose of satellite serving. As the primary measurement system, optical system can provide the information of relative navigation in near field. The paper has two main contributions. Firstly, we summarize use of optical systems for guidance and navigation in the missions of proximity operations in aerospace. Their characteristics vary from the manned missions, which are performed by astronauts on-orbit, through semi-autonomous missions, wherein human operators on the ground segment issue high level directives and sensor-guided systems on the space segment guide the execution, to the full-autonomous missions, which are executed using unmanned space robotic systems. It comes to light that future space operations will be more autonomous. Secondly, we present a concept and framework of a vision system for satellite proximity operations, which is semi-autonomous and can treat with uncooperative satellites. The vision system uses visible and infrared sensors synchronously to acquire images, which solves the problem of data integrity introduced by ambient illumination and direct sunlight for visible sensor. The vision system uses natural features on the satellite surfaces instead of artificial markers for its operation, computes relative motion and structure of the target, and tracks features in image sequences. Selected algorithms of the system have been characterized in ground environment; they are undergoing systematic sets of adaptation for space.

The ultrafast photoconductive characteristics of GaAs bulk were investigated by the optical-pump terahertz-probe spectroscopy (OPTP) at room temperature. In our experiment, a significant decrease of the terahertz transmittance has been observed when the time delay between the optical pump pulse and the terahertz probe pulse was adjusted. It can be concluded that the electronic states of the GaAs became metallic, when the optical excitation occurred on the surface of the GaAs material. Since we expect only the free carrier response in the terahertz range, the decrease of the transmittance is obviously assigned to the appearance of the high electronic conductivity due to the increasing free carriers. Furthermore, it was found that transmittance of the terahertz radiation decreased with the increase of the optical pump power due to the more optical generated carriers under the higher power. We can also find that the carrier recombination time of the GaAs became shorter while the power of the optical pump was lowered.

Planar Microtoroid cavities with ultrahigh quality factor have very strong confined function to the electromagnetic wave coupled into them due to their novel ring-like structures. Therefore, they have very good applications in high sensitivity sensors and other micro optics components. In this paper, the Planar Microtoroid cavity and its coupling system constructed together with the tapered fiber are introduced. Then, micro sensors based on the above coupling system are designed. These sensors measure environmental parameters by means of monitoring the changes in the transmission spectrum of the high finesse Planar Microtoroid cavities, obtaining fine resolution and high accuracy due to their ultrahigh quality factor (Q) performance. The sensitive mechanism and the feasibility are demonstrated through optical and mechanical software simulation. With software BeamPROP, the evident resonance and strengthened phenomenon to the electromagnetic wave coupled into the micro-cavity are shown, which have a big relation with the light frequency. The results indicate that, Planar Microtoroid cavity is very promising in designing new micro sensors.

Phase retrieval technique is one of the most important methods to measure the wavefront in adaptive optics. In this paper, a linear phase retrieval (LPR) technique used in close-loop adaptive optics (AO) is introduced. The performance of a close-loop AO system based on the LPR sensor is researched using numerical simulations first. Then an AO experimental system based on LPR sensor is set up with a 32-element piezoelectric deformable mirror (DM). The static phase aberration correction experiment is carried out to research the valid range of phase aberration that can be corrected and the dynamic characteristic. Both the numerical simulation results and the experimental results show that the LPR technique can be used in adaptive optics to correct the small phase aberration successfully. The dynamic characteristic shows that the LPR sensor may be used in real-time AO system in future.

The architectures of CCD and CMOS image sensors are introduced briefly, followed by comparison of their performances in detail. At last, the future development trends of CCD and CMOS image sensors are prospected. It is pointed out that CCD and CMOS image sensors will remain complementary and competition, and flourish the image sensor market together in predictable future.

A fiber optical microphone with temperature insensitivity is described in this paper. A sensor system achieves acoustic vibration signal by attaching a Fiber Bragg Grating (FBG) to a diaphragm which can response to acoustic vibrations. Broadband light is launched into the FBG through a coupler and the light reflected by the FBG is directed to another matched FBG which works as a wavelength demodulator. Vibration of the diaphragm causes stress changes to the FBG, and introduces variations of the FBG wavelength. Therefore, acoustic vibrations can be detected by measuring the FBG wavelength variations. In this study, a pair of matched FBGs is employed for both wavelength demodulation and temperature compensation. These features not only make the fiber optical microphone achieve a stable operation, but also improve the entire frequency range of demodulation. Compared with traditional microphones, the fiber optical microphone can achieve low noise and a superior performance of anti-electromagnetic interference.

The magnetostrictive transducer is the most important part of the optic-fiber magnetic field sensor, and the optic-fiber/giant magnetostrictive(GMS) film coupled structure is a novel coupling form of the magnetostrictive transducer. Always we analyze the coupled structure based on the entire coupled structure being sputtered GMS material without tail-fibers. In practical application, the coupled structure has tail-fibers without films at two ends. When the entire coupled structure is immersed in the detected magnetic field, the detected magnetic field causes the GMS film strain then causing optic-fiber strain. This strain transmission process is different from it in the coupled structure entirely with GMS films without tail-fibers. The strain transmission relationship can be calculated theoretically in the coupled structure without tail-fibers, but it's complicated to theoretically calculate the strain transmission relationship in the coupled structure with tail-fibers. After large numbers of calculations and analyses by ANSYS software, we figure out some relationships of the two strain transmission processes in the respective structures and the stress distribution in the tail-fibers. These results are helpful to the practical application of the optic-fiber/ GMS film coupled structure.

The novel FBG temperature sensor eliminating lateral strain cross-sensitivity was present and theoretically analyzed. The temperature sensor characteristic of the FBG based on the method for eliminating lateral strain was researched from room temperature to 190°C, and the FBG was pressed by lateral force during rising temperature. The lateral force resulted in the birefringence of the FBG, and the FBG exited two different reflective spectra meeting with the Bragg condition. The change spacing of the peak value between two reflective spectra is used to eliminate lateral strain crosssensitivity to temperature, and amend the temperature sensitivity coefficient and the change temperature value.

A method using fiber Fabry-Perot tunable filter to achieve FBG sensor's Bragg wavelength is described. The system has the capability to interrogate large number of DFB sensors, whilst obtaining absolute Bragg wavelength with pm resolution. A demonstration system with 4 strain sensors is presented, which obtains DFB sensor's absolute strain value and achieves sub-microstrain resolution at 300Hz interrogating rate.

This paper introduces the design of a novel time-resolved fluorometer based on immunochromatograghy. Different from the other time-resolved fluorometers, it tests the immunochromatographic strip which is labeled with lanthanide ions and their chelates. This instrument can provide a rapid, quantitative measurement of analytes present in samples without any washing steps and it can be used to carry out point-of-care test (POCT). The immunochromatograghy-based timeresolved fluorometer is composed of a specific optical sensor, a scanning stage, a signal processing system and a computer control system. The light from UV LED is focused on the test strip by a condense lens group in the optical sensor. If the labels are present in samples, the fluorescence at 613nm will be exited (when Eu³⁺chelate is used for marking substance). After a delay of some microseconds, the fluorescence will be collected by the optical sensor and converted into electronic signal by a photomultiplier tube (PMT). The concentration of the sample can be calculated through the standard working curve of this instrument. By testing, the sensitivity is several ng/ml level (when Eu³⁺chelate is used for marking substance), test linear range is from several ng/ml to 10³ ng/ml, in which correlation coefficient is 99.97%.

Whispering gallery modes (WGM) in a cylindrical micro-cavity of a silica optical fiber are excited with a tapered fiber of ~7μm in diameter by evanescence field, and the WGM spectra of the cylindrical micro-cavity with different diameters (300μm, 400μm and 500μm) are measured. The resonant positions and their separations of the spectra are assigned precisely by an asymptotic formula. Considering the fiber dispersion and the errors induced from it, the values of the resonant position and its separation achieved from assignment within the experimental spectra range (1290~1320 nm) match well with a theoretical calculation and a measured accuracy of the refractive index of the micro-cavity can be as high as 10^-5, which indicates that a dispersion sensor can be formed by measuring the dispersive features of WGM in a cylindrical micro-cavity.

Toxoplasma Gondii infection is widespread in humans worldwide and reported infection rates range from 3%-70%, depending on the populations or geographic areas, and it has been recognized as a potential food safety hazard in our daily life. A magnetic molecular beacon probe (mMBP), based on theory of fluorescence resonance energy transfer (FRET), was currently reported to detect Toxoplasma Gondii DNA. Nano-sized Fe₃O₄ were primarily prepared by coprecipitation method in aqueous phase with NaOH as precipitator, and was used as magnetic core. The qualified coreshell magnetic quantum dots (mQDs), i.e. CdTe(symbol)Fe₃O₄, were then achieved by layer-by-layer method when mol ratio of Fe₃O₄/CdTe is 1/3, pH at 6.0, 30 °C, and reactant solution was refluxed for 30 min, the size of mQDs were determined to be 12-15 nm via transmission electron microscopy (TEM). Over 70% overlap between emission spectrum of mQDs and absorbance spectrum of BHQ-2 was observed, this result suggests the synthesized mQDs and BHQ-2 can be utilized as energy donor and energy acceptor, respectively. The sensing probe was fabricated and a stem-loop Toxoplasma Gondii DNA oligonucleotide was labeled with mQDs at the 5' end and BHQ-2 at 3' end, respectively. Target Toxoplasma gondii DNA was detected under conditions of 37 °C, hybridization for 2h, at pH8.0 in Tris-HCl buffer. About 30% recovery of fluorescence intensity was observed via fluorescence spectrum (FS) after the Toxoplasma gondii DNA was added, which suggested that the Toxoplasma Gondii DNA was successfully detected. Specificity investigation of the mMBP indicated that relative low recovery of fluorescence intensity was obtained when the target DNA with one-base pair mismatch was added, this result indicated the high specificity of the sensing probe. Our research simultaneously indicated that mMBP can be conveniently separated from the unhybridized stem-loop DNA and target DNA, which will be meaningful in DNA sensing and purification process.

Star tracker is a high precise, high reliable attitude measurement component of spacecrafts, which plays a very important role in attitude measurement and control system. Unfortunately, in low light level, in order to obtain good quality image, the common CCD needs more time to integral light. This leads low data output and update slowly. In this paper, the star tracker based on a novel electronic multiply CCD (EMCCD) is introduced. EMCCD has very high sensitivity. The application of EMCCD is very finite in space explore field, although it has been applied by some country. At first, the detection sensitivity of EMCCD is analyzed, based on the signal detection theory in noise and optimal SNR threshold detection principle, and the detection sensitivity model is established. And then, the main noise sources of EMCCD are analyzed. Finally, as an example, a specific detection sensitivity calculation of EMCCD star tracker is provided with given optical parameters and exposure time.

In order to detect the liquid leak, many researchers present different methods. However, traditional detection methods are electrical methods, which are costly and unsafe. In this study, we present a LPG sensing system for leak detection of oil storage tanks. Since LPG is sensitive to external refractive index changes LPGs can be used as sensors to detect oil leak.

The vegetation eco-environment is one of the import constituent elements for the human eco-environment. This article assesses the vegetation ecol-environment quality(VEQ) over part of the Qingjiang region by using TM remote sensing image and principal component analysis (PCA) method. There are various geographical and ecological features having effect on eco-environment of Qingjiang region, Hubei province. The paper gives an evaluation index system of VEQ by analyzing regional geographical and ecological features, which are composed of 5 factors on vegetation cover, topography & geomorphology, moisture, land cover and hydrothermal regime. These factors are extracted from the TM remote sensed data. The PCA method is used to calculate the weight of every index. Based on these indices, an integrated evaluation model of eco-environment quality is built. With the model, the study region is evaluated and divided into five VEQ evaluation classified ranks. It is concluded that the VEQ in our study region is good as a whole and the leading VEQ rank is II and III have occupied the proportion of 76.09%.

In the design of Erbium Doped Fiber Amplifier (EDFA), improving flat-gain has great important significance. The working principle and gain characteristics of EDFA are introduced briefly, the influence of the factors such as Erbium doped fiber (EDF) length and pump power on the gain of EDFA is analyzed in detail, and the simulation experiments were carried out with Optisystem software. The result shows that, when pump power is constant, with EDF length departing the optimal value, the gain of each channel decreases at different degrees; when EDF length is constant, with pump power departing the optimal value, the gain of each channel changes at different degrees. Moreover, Er³⁺ concentration has significant effect on the gain, and there is an optimal Er³⁺ concentration to get the largest gain.

Star tracker is the most precision attitude measurement instrument of spacecrafts, which plays a very important role in attitude measurement and control system. The technology of star tracker based on CCD is very popular. Unfortunately, with a CCD system, a single integration period for the entire sensor is necessitated. This leads low data output and update slowly. Moreover, CCD star tracker is not proper to micro-spacecraft because its volume, weight and energy consume cannot further decrease. Thus, the novel electron-multiplying CCD (EMCCD) is starting their way in space applications field. Centroiding algorithm is a subpixel position determination method proper to star position calculation because of its high accuracy and simplicity. But its position accuracy is affected by various kinds of noise. In this paper, the subpixel position accuracy of centroiding algorithm is analyzed. The focus is on the estimation of the attainable accuracy in the application of EMCCD detector, and analysis of the EMCCD noise influence on the star subpixel position accuracy to find the methods of improving it. The analysis shows that the main contributors to the errors of subpixel position come from dark noise, read noise and photon shot noise. Simulation experiment results show that the subpixel position accuracy can attain 1/45 pixel, which

An optical fiber hydrogen sensor based on the measuring principle of surface plasma resonance is introduced. The structure of the hydrogen-sensitive head which is coated with Pd-Ag alloy film on the surface of the etched optical fiber is investigated theoretically. When hydrogen gas is absorbed into the Pd thin layer of the sensing head, the Pd hydride is formed and then the refraction index of the etched optical fiber surface will be changed with different hydrogen gas concentration. The surface plasma wave is stimulated by the light wave in optical fiber and the surface plasma resonance occurs between the thin metal layer and the medium surface of hydrogen gas. The Pd-Ag alloy film thickness versus the sensitivity of hydrogen sensing head is analyzed and optimized via the numerical method. The sensing head which is based on surface plasma resonance is manufactured and used in the experiment system of hydrogen gas detecting, and the experiment results demonstrate that the detecting system has high sensitivity with the hydrogen concentration in the range of 0%-4%, the accuracy, resolution and response time are respectively 5%, 0.1% and 30s. This sensor structure can be applied to detecting the low concentration of hydrogen gas.

Base on the heat transfer theory, the thermal models of thermooptic variable optical attenuator based on side-polished fiber surrounded by thermooptic polymer with electrode inside were built. The finite element method has been used to compute and analyze thermal distributions of the thermooptic models. The thermal distributions of both the models with single stick electrode or helical electrode were analyzed in three directions. According to the analysis, the helical electrode is a suitable electrode structure for thermooptic variable optical attenuator based on side-polished fiber.

Object tracking technology combined with image stabilization is called tracking technology based on image stabilization. Moving objects affect stabilization compensation in tracking algorithm based on image stabilization. The middle value method, former background method and dynamic clustering method are not useful for rotate or non-rigid objects. Fuzzy Clustering of feature points is proposed to solve these problems. First background and objectives membership value of the pixel are calculated, and then pixels are classified to background and target categories accurately by defining membership threshold of the background and targets. Experimental results show that fuzzy clustering algorithm resolves the moving target interference problem in image sequence and realizes steady tracking of object. It is proved to be more robust and less sensitive to the numbers of initial clustering.

Camera systems are often unsteady on platform of airborne, car borne and ship borne. Stabilization algorithm can be used to eliminate impact of vibration. But image sequence after processing is different from original sequence. If there is a moving target in camera field, feature points on the target must be indentified and made sure corresponding relationship in processed sequence. To solve the problem that moving target features position and correspondence are difficult to identify in image sequence after image stabilization processing, background updating difference moving target detection algorithm based on motion analysis is proposed. It uses subsample mean and subsample variance and introduces the concept of background gray probability to identify feature points of moving target in the steady image sequence. In addition, to solve the problem of incomplete motion track of feature points caused by obstruction or weak target detection algorithm, partial limit incomplete smooth track algorithm is proposed. It is used to identify correspondence of feature points on the moving target, and to solve temporary occlusion of moving object. Experimental results show that moving target features position and correspondence can be identified quickly through the two algorithms. Single-frame processing speed can reach an average of 27 ms with DSP6416 processor. Image stabilization algorithm and the two algorithms can be combined to realize real-time tracking based on image stabilization.

A wavelength division multiplexed linear fiber laser sensor array system using four distributed feedback fiber lasers (DFB FLs)is reported. The characteristics of frequency noise are investigated experimentally. Results show the interaction between neighboring (in wavelength space) fiber lasers spaced ~2.4nm is so weak that the influence of crosstalk could be omitted. With optimization of pump sequence, all the fiber laser sensors would reach the system minimum detectable frequency noise. A further discussion about the influence of transmission fiber is also included.

Since the 1990s, with the development of technology of VLSI, CMOS image sensors have been developed increasingly. The architecture and working principle of CMOS image sensors are introduced. The main advantages of CMOS image sensors with respect to CCD are analyzed. The key technical problems of CMOS image sensor are discussed, and the related solving ways are given. The research status of CMOS image sensors is reviewed. At last, the development trends of CMOS image sensor are prospected.

In this paper, a simple single-backward configuration with a section of un-pump fiber is presented to achieve a stable L-band superfluorescent fiber source (SFS). The effects of the structural parameters on the output characteristics of the L-band SFS in terms of output spectrum, mean wavelength, and linewidth are theoretically examined. By selecting suitable structure parameters, an L-band SFS with mean wavelength insensitive to pump power is achieved under a pump power of 190mW, corresponding to a mean wavelength of 1583.20nm, an output power of 47mW, and a spectral linewidth of 49.6nm. The proposed L-band SFS design shows its tremendous advantages as simple structure and good performances that make it be useful in WDM system, fiber optic gyroscopes and fiber sensor systems applications.

As an optical sensor and controller in wavelength division multiplexing (WDM) system, the acousto-optic tunable filter (AOTF) is one of powerfully several potential sensing candidates. The AOTF can easily achieve dynamically to add/ drop arbitrary wavelength by changing the RF frequency in its range of working wavelength. In this paper, the reason of the signal crosstalk is given and its characteristic of sidelobe is firstly analyzed on the momentum matching condition. The coupling equations with multiple acoustic waves traveling simultaneously are presented. The analytic solution of the diffraction efficiency for the two acoustic frequencies is given, and its impact on the device performances is discussed. The result is correspondence with experimental results. In addition, because the TeO₂ AOTF has a specific structure based on its design principal, it is shown whether the sidelobes on the diffractive efficiency curve appear is mainly decided by the bandwidth of the AOTF and the mismatching factors. For a definite device bandwidth, if the total momentum mismatch is lower than a definite value, the device has no sidelobe. Then, the feasibility of the TeO₂ AOTF as an OADM in WDM system has superiority on signal crosstalk.

We report the experimental demonstration of a novel label-free optical immunosensor based on porous silicon microcavity for the detection of Hydroxysafflor yellow A (HYSA). HYSA antibodies were immobilized into the porous silicon using standard amino-silane and glutaraldehyde chemistry. We monitor the shift of the resonance dip in the reflectance spectrum when HYSA-BSA is attached to the porous silicon microcavity. The label-free immunosensor is simple and exhibit excellent sensitivity for HYSA antibodies with a sensitivity of 0.91nm/ng.

The method with sensing of MIG welding pool surface is studied in this paper.The distributing of arc action spectrum, pool reflecting action spectrum and pool radiating action spectrum are analyzed. The radiation is weaker at interzone 500-700nm. So, the structured light source is confirmed to semiconductor laser at wavelength 650nm. Narrow band filter and neutral density filter are mounted on CCD, they are good for restrained the influence of arc. The pool width is studied on small current by experimented, deforming and distributing of structured light are confirmed. The form and sort of splash are studied, the method of reducing and protecting splash are also studied. Welding current is selected properly to restrained splash. Incident angle of structured light is 30 degree. The MIG pool image is captured by CCD. Deformed structured light fringes are reflected the information of the concave or convex of the pool.

The PA absorption property of NO₂ is tentatively surveyed under the condition of room temperature. Laser radiation of 438.0nm is used as excitation source. It is shown that owing to the enhancement of V-T transfer energy with buffer gas pressure, the intensity of the PA signal increases when the pressure of NO₂ maintains at 665Pa and the pressure of the buffer gas is increased. But the PA signal is almost invariable when the buffer gas pressure is more than 3×10⁴Pa. The quantity of NO₂ is changeless are responsible for this phenomena. The PA signal shows itself as linearity variation with NO₂ concentration. Trace concentrations of NO₂ are detected under ambient conditions. The detection limit of 6.4ppm is obtained on the basis of SNR=1 with the homemade apparatus. But one can expect much lower value of the detection limit of this method by improving the detection setup. The velocity of the sound in NO₂ gas is measured from the PA signal. It is about 270m/s. It also finds that the sound velocity varies slightly with the buffer gas pressure.

In order to acquire sequence images in PIV measurement system of continuous clashing flow of water, two laser flashers, the red one and the green one, are used in PIV measurement system. After the digital camera is triggered, the two flashers flash in a short interval during the exposure period. The red light and the green light illuminate the same region so that the image records the movements of tracing particles in two colors. Using digital image process technology, two images, the red one and the green one, can be obtained from the original image. Based on the two images, the flow field parameters can be calculated. The method possesses predominant advantages: high speed field can be measured using an ordinary camera and the two images have determinate time labels, so the moving direction of the particles can be determined easily. The main steps of the method include the transition from Bayer matrix to RGB matrix, the pretreatment of the images, the analyzation of the velocity and the arrangement of the results.

A spectroscopy-based detector is developed to measure the nitrogen and chlorophyll content of tomato leaves and then to predict the growth condition of tomato plants in greenhouse. The detector uses two wavebands, 527 nm and 762 nm, since it is proved that these wavebands are sensitive to nitrogen and chlorophyll content in plant leaves by previous field test. The detector contains: A Y-type optic fiber, two silicon photocells, a signal processing unit, and a MCU. Light reflection from tomato leaves is transmitted by the Y-type optic fiber to the surface of the silicon photo cells, which transfer optical signal into electrical signal. Then the analog signal is amplified to conform to the TTL level signal standard and finally converted to digital signal by MAX186. After that, the MCU carries on a series of actions, including data calculating, displaying and storage. Using the measured data, the Normalized Difference Vegetation Index (NDVI) is calculated to estimate the nitrogen and chlorophyll content in plant leaves. The result is directly displayed on an LCD screen. Users have an option in saving data, either into a USB-memory stick or into a database over the PC serial port. The detector is portable, inexpensive, and convenient, which make it meet farmers' need in China. The performance test shows that the growth model works very well, and the device has high accuracy in predicting the growth condition of tomato plants in greenhouse.

Shack-Hartmann wavefront sensor (SHWFS) is widely used in adaptive optics systems. Its centroid detecting error is one of the main error sources in adaptive optical systems. There are many factors affecting the detecting accuracy such as photon shot noise, readout noise, background level of CCD camera and number of detecting pixels. It is very effective to enhance the centroid accuracy by setting the threshold for the images of the SHWFS. But in daytime, the sky background is strong and changes very fast. The threshold cannot be chosen automatically either. In this paper, a new method based on the morphologic filter and ant colony algorithm is proposed to improve the SHWFS centroid detecting accuracy. The principle of the morphologic filter and the ant colony algorithm is introduced and the simulation results are also presented. The results show the proposed method can enhance SHWFS centroid accuracy very well.

A novel single-ended reflecting long period fiber grating (LPFG) sensor with thin metal film overlay and the sensing system is described. An all-fiber reflection based surface plasma resonance (SPR) LPFG sensor with three-layer structure (core, cladding and metal) is established experimentally and fabricated with a pulsed CO₂ laser writing system and vacuum evaporation coating system. Different nm-thick thin metal films are deposited on the reflected LPFG sensor for the excitation of surface plasma waves (SPWs) and the characteristics of the reflection resonance spectra of the LPFG sensor for measuring refractive index of fluids are studied. It is found that different thicknesses of different metal films show different measuring sensitivity. Through the comparison of the resonance wavelength obtained in air, water, alcohol, glycerin and their mixture solution, different sensitivities of the reflected SPR-LPFG sensor have been achieved. The proposed SPR-LPFG sensing scheme offers an efficient platform for achieving high performance fiber sensors for the measurement of ambient refractive index.

Field information acquisition plays an important part in Precision Agriculture System. Spatial and temporal variation of grain yield in a field is important field information. It can guide farmers in a reasonable means of production in order to save input and improve efficiency. Thus a grain yield monitor is developed based on photoelectrical sensor. The monitor consists of a LED, a photoelectrical transducer, cables, signal processing circuit, acquisition circuit, etc. The LED and the photoelectrical transducer are equipped in the left and right sides of the clean grain elevator of the combine harvester, respectively. When harvested wheat is threshed, clean grain is lifted to the grain tank by the lifting plates of the elevator, and the grain in a plate will switch off the light from the LED to the transducer. The height of the grain in a plate has a high correlation with the switching off time of the transducer. To measure the switching off time makes it possible to estimate grain yield. The signal processing circuit and acquisition circuit are used to monitor whether the light from the LED is switched off and then to measure the switching off time. And the yield can be calculated from the measured time based on a calibration model. The performance test shows the developed grain yield monitor is practical.

Degenerate four-wave mixing (DFWM) is a nonlinear optical process that has been developed as a detective tool for making quantitative measurements of gas dynamic properties in the various environments. This technique can be used to measure temperature and species concentration in both flames and plasma environments. The resulting coherent signal beam makes DFWM particularly attractive for luminous and harsh environments, compared to incoherent techniques, such as laser-induced fluorescence (LIF). Forward DFWM with self-stability of spilt-beam system has been demonstrated in iodine vapor. It's found that there exists no LIF because of collision quenching at atmospheric pressure and room temperature. But observed vivid DFWM spectroscopy (554-556nm) of iodine vapor at 0^oC and room temperature. Furthermore, DFWM can probe non-fluorescing species. We describe a novel advanced sensor method for measuring temperature of gas flows using DFWM. This technique without suffering of severe quenching problems at atmospheric pressure is of importance to trace atom, molecular and radical in combustion diagnosis.

A set of coupled mode equations for a multi-channel array acousto-optic interaction is put forward, and its solutions are derived. The principal diffraction and inter-modulation of multi-channel acoustic waves and their effects on diffracted light beams are analyzed. The multi-channel array Bragg acousto-optic device is made. The experimental results indicate that the multi-channel acousto-optic modulators can modulate the light beam of every channel simultaneously.

Natural light is very important element in the quality of vision. Solar light pipes are effective method to induce sunlight into the room need to be illuminated especially for corridor, some places natural sunlight cannot arrive. Solar light pipes are also effective ways to reduce electricity consumption for lighting; it can transmit sunlight from outdoor to the room without generating excessive heat. The performance of two top lighting solar light pipes and one side lighting solar light pipe were investigated at the same time under sunny conditions in winter in Beijing. The results showed that side lighting solar light pipes have better performance than that of top lighting one. Side lighting light pipe has better performance than top lighting light pipe if there are no shelters around the top dome under sunny conditions in winter in Beijing. Solar altitude is the main reason to give an effect on the performance of light pipes. The experimental results also showed that top lighting solar light pipes with "snow type" diffuser has better performance compare with the "diamond type" one. Solar azimuth can also affect the illuminance for whole day to all solar light pipes. So if the sunlight collector can following with the sun, this problem can be resolved, that is, automatic sun trackers are needed, but the cost will become too much at the same time. Different regions and different seasons had to select different types of solar light pipes to achieve maximum output of illuminance in the room. Design of the solar light pipes must adjust measures to local conditions. Solar light pipes will be popularized in the near future in China because have many advantages to improve energy efficiency in buildings.

With a newly-developed 16-sample wavelength-shifting algorithm, Fizeau phase-shifting interferometry with a laser diode (LD) suppresses alignment errors in a test plate. This phase-shifting algorithm includes the elimination of phase errors due to changes in laser power by LD currents. The measurement phase errors on a 16-sample phase-extraction algorithm are numerically and experimentally estimated. The surface-profile measurement of a plane-parallel plate is experimentally shown free from systematic errors.

When a diffuser is illuminated by the coherent light with intensity distributions obeying a negative power law, speckle fields with fractal properties are produced. Such a random field is called fractal speckles. Fractal speckles have extremely long spatial correlation functions of the intensity distributions in comparison with ordinary speckles. It implies that fractal speckles may extend measurement ranges in various metrological applications based on the spatial correlation of speckles. We report the generation of fractal speckles using computer-generated holograms based on the method of stationary phase and the iterative Fourier transform algorithm, and its application to speckle correlometry is discussed.

Toxoplasma gondii is a microscopic parasite that may infect humans, so there is an increasing concern on the early detection of latent Toxoplasma gondii infection in recent years. We currently report a rapid and sensitive method for Toxoplasma gondii based on molecular beacon (MB) probe. The probe based on fluorescence resonance energy transfer (FRET) with a stem-loop DNA oligonucleotide was labeled with CdTe/ZnS quantum dots (energy donor) at 5' end and BHQ-2 (energy acceptor) at 3' end, respectively. The probe was synthesized in PBS buffer at pH 8.2, room temperature for 24 h. Then target DNA was injected under the condition of 37°C, hybridization for 2 h, in Tris-HCl buffer. The data from fluorescence spectrum (FS) showed that ca 65% of emitted fluorescence was quenched, and about 50% recovery of fluorescence intensity was observed after adding target DNA, which indicated that the target DNA was successfully detected by MB probe. The detecting limitation was determined as ca 5 nM. Moreover, specificity of the probe was investigated by adding target DNA with one-base-pair mismatch, the low fluorescence recovery indicated the high specificity. The results showed that the current sensing probe will be a useful and convenient tool in Toxoplasma gondii early detection.