2007 Vol. 28, No. 1
Display Method:
2007, 28(1): 1-6.
Abstract:
This paper reviews characteristics and performance of a 160×120 uncooled infrared focal plane array made from amorphous silicon microbolometers with a pixel-pitch of 25μm, integrated in a LCC package compatible with mass production. The 25μm pixel architecture profits from the low thermal time constant which characterizes our technology, to design a higher pixel thermal insulation and therefore to develop a 25μm version from the well mastered 35μm technology. Thanks to a new pixel design and by pushing the design rules even further, a high fill factor has been kept, without the use of complex, as well as expensive, two-level structure. The detector is described in terms of ROIC architecture, packaging, operability and electro-optical performances. A new read out integrated circuit structure has been designed for this detector. High level functions like gain, image flip and integration time could be operated through a serial link to minimize the number of electrical interconnections. A small LCC package has been developed enabling a mass production of detectors for compact hand held or helmet mounted cameras.
This paper reviews characteristics and performance of a 160×120 uncooled infrared focal plane array made from amorphous silicon microbolometers with a pixel-pitch of 25μm, integrated in a LCC package compatible with mass production. The 25μm pixel architecture profits from the low thermal time constant which characterizes our technology, to design a higher pixel thermal insulation and therefore to develop a 25μm version from the well mastered 35μm technology. Thanks to a new pixel design and by pushing the design rules even further, a high fill factor has been kept, without the use of complex, as well as expensive, two-level structure. The detector is described in terms of ROIC architecture, packaging, operability and electro-optical performances. A new read out integrated circuit structure has been designed for this detector. High level functions like gain, image flip and integration time could be operated through a serial link to minimize the number of electrical interconnections. A small LCC package has been developed enabling a mass production of detectors for compact hand held or helmet mounted cameras.
2007, 28(1): 7-11.
Abstract:
A miniaturized uncooled infrared image processing system is designed by adopting the structure of Field Programmable Gate Array (FPGA) embedded with NiosⅡ processor instead of Digital Signal Processor (DSP) +FPGA structure. A signal processing method based on pipelining model is proposed and applied in the system with the hardware and software development tools of NiosⅡ embedded processor. As indicated by the experiment result, the system can process the uncooled infrared image in real time. It has the merits of good performance and small volume.
A miniaturized uncooled infrared image processing system is designed by adopting the structure of Field Programmable Gate Array (FPGA) embedded with NiosⅡ processor instead of Digital Signal Processor (DSP) +FPGA structure. A signal processing method based on pipelining model is proposed and applied in the system with the hardware and software development tools of NiosⅡ embedded processor. As indicated by the experiment result, the system can process the uncooled infrared image in real time. It has the merits of good performance and small volume.
2007, 28(1): 12-15.
Abstract:
In order to realize the extension of spectral response of photocathode to short wave, the mechanism of Ga1-xAlxAs/GaAs photocathode, whose spectral response extends to short wave, is analyzed, a new concept of Quasi Energy Gap is presented，the rule that the energy gap of Ga1-lxAs/GaAs widens gradually with the increase of the aluminum composition x is discussed, and the short-wavelength threshold of spectral response for photocathode in different aluminum compositions is calculated. Accordingly, the image tube with wide spectral response was made by increasing the aluminum composition of photocathode material, and the corresponding spectral response curve is given. In comparison with the spectral response of the standard Gen. Ⅲ low-level-light image intensifier, the spectral response curve of the tube we made extends to short wavelength. The experimental result coincides with the theoretical design.
In order to realize the extension of spectral response of photocathode to short wave, the mechanism of Ga1-xAlxAs/GaAs photocathode, whose spectral response extends to short wave, is analyzed, a new concept of Quasi Energy Gap is presented，the rule that the energy gap of Ga1-lxAs/GaAs widens gradually with the increase of the aluminum composition x is discussed, and the short-wavelength threshold of spectral response for photocathode in different aluminum compositions is calculated. Accordingly, the image tube with wide spectral response was made by increasing the aluminum composition of photocathode material, and the corresponding spectral response curve is given. In comparison with the spectral response of the standard Gen. Ⅲ low-level-light image intensifier, the spectral response curve of the tube we made extends to short wavelength. The experimental result coincides with the theoretical design.
2007, 28(1): 16-19.
Abstract:
Glass composition of microchannel plate (MCP) is optimized to reduce the ion feedback noise of MCP and to improve the image quality and lifetime of image intensifier. The MCPs with optimized glass composition were fabricated by introducing different types and amounts of alkaline-metal oxide as well as adopting high-temperature hydrogen reduction technique. The transfer temperature for the glass is increased; it could be baked at the temperature of over 500℃ and remains stable in electrical performance. The result shows that the internal surface structure of the channel is improved, MCP′s resistance to electron scrub is enhanced, and the gas absorbing is decreased. At last, the further research is proposed.
Glass composition of microchannel plate (MCP) is optimized to reduce the ion feedback noise of MCP and to improve the image quality and lifetime of image intensifier. The MCPs with optimized glass composition were fabricated by introducing different types and amounts of alkaline-metal oxide as well as adopting high-temperature hydrogen reduction technique. The transfer temperature for the glass is increased; it could be baked at the temperature of over 500℃ and remains stable in electrical performance. The result shows that the internal surface structure of the channel is improved, MCP′s resistance to electron scrub is enhanced, and the gas absorbing is decreased. At last, the further research is proposed.
2007, 28(1): 20-23.
Abstract:
UV fingerprint identification camera system is a very useful tool in the field of criminal investigation. But its image quality is often influenced by the bright spot in the FOV center of the system. In this paper, the operation principle of fingerprint identification and camera system is described. The generation of the bright spot is analyzed and some methods are given to eliminate it. It is pointed out that the phenomenon is mainly caused by off-axis stray light from the system. The methods to eliminate the bright spot include, adopting an object lens with higher extinction performance, using a view-field diaphragm with proper diameter and position, or evaporating a UV absorbing film on the input window surface outside the active area. The experimental result shows that the methods meet the fingerprint identification and storage requirements in criminal investigation.
UV fingerprint identification camera system is a very useful tool in the field of criminal investigation. But its image quality is often influenced by the bright spot in the FOV center of the system. In this paper, the operation principle of fingerprint identification and camera system is described. The generation of the bright spot is analyzed and some methods are given to eliminate it. It is pointed out that the phenomenon is mainly caused by off-axis stray light from the system. The methods to eliminate the bright spot include, adopting an object lens with higher extinction performance, using a view-field diaphragm with proper diameter and position, or evaporating a UV absorbing film on the input window surface outside the active area. The experimental result shows that the methods meet the fingerprint identification and storage requirements in criminal investigation.
2007, 28(1): 24-29.
Abstract:
A noise reduction method of using multiple identical analog channels to oversample the CCD signal is investigated experimentally. This method is based on the irrelevant noise characters in each part of the CCD camera's analog channel. The noise distribution in the circuit is tested and the noise improving factors are 1.354 and 1.65 for the two parallel connections and three parallel connections respectively. The improving factor agrees with the theory value. Experiment shows that the improving factor decreases with the increase of the gain of the programmer gain amplifier in the analog channel. This phenomenon and the difference between the experiment value and the theory value of improving factor are analyzed. The power supply noise, higher AD conversion rate and temperature rising are the major factors of the difference.
A noise reduction method of using multiple identical analog channels to oversample the CCD signal is investigated experimentally. This method is based on the irrelevant noise characters in each part of the CCD camera's analog channel. The noise distribution in the circuit is tested and the noise improving factors are 1.354 and 1.65 for the two parallel connections and three parallel connections respectively. The improving factor agrees with the theory value. Experiment shows that the improving factor decreases with the increase of the gain of the programmer gain amplifier in the analog channel. This phenomenon and the difference between the experiment value and the theory value of improving factor are analyzed. The power supply noise, higher AD conversion rate and temperature rising are the major factors of the difference.
2007, 28(1): 30-32.
Abstract:
In free-space optical communication system, the resolution is a very important parameter, which affects the performance of the whole system. As a common detector in the sub-system of APT, PSD has some advantages, such as high resolution, no blind area, high-speed response, etc. The basic architecture of PSD and its detection theory are analyzed, the position resolution in spatial optical communication achieved with PSD is investigated, and the methods are presented to improve the position resolution of PSD. A set of experiment system was set up to analyze the resolution of PSD in sub-system of APT. Through the analysis of the data which we achieve, the average position resolution is up to 12.6μm which agrees with theoretical resolution quite well. The feasibility of PSD as a fine tracking detector in the sub-system of APT is proved.
In free-space optical communication system, the resolution is a very important parameter, which affects the performance of the whole system. As a common detector in the sub-system of APT, PSD has some advantages, such as high resolution, no blind area, high-speed response, etc. The basic architecture of PSD and its detection theory are analyzed, the position resolution in spatial optical communication achieved with PSD is investigated, and the methods are presented to improve the position resolution of PSD. A set of experiment system was set up to analyze the resolution of PSD in sub-system of APT. Through the analysis of the data which we achieve, the average position resolution is up to 12.6μm which agrees with theoretical resolution quite well. The feasibility of PSD as a fine tracking detector in the sub-system of APT is proved.
2007, 28(1): 33-37.
Abstract:
A method of maneuvering target prediction is presented for vehicle-mounted image tracking system. The target motion is divided into two parts, namely global motion and local motion, which are separately predicted according to their intrinsic dynamic behavior. The local motion prediction is described emphatically in this paper. A high-performance filtering tracker, which was then extended into a predictor to estimate the future moving state of target, was built up through the research on the maneuvering target tracking (MTT) technique, thereby the “interacting multiple-model(IMM) prediction algorithm” is put forward. As the simulation shows, this algorithm has high precision for predicton and good self-adaptive capability. Besides, the method of the prediction gate computation is given in this paper.
A method of maneuvering target prediction is presented for vehicle-mounted image tracking system. The target motion is divided into two parts, namely global motion and local motion, which are separately predicted according to their intrinsic dynamic behavior. The local motion prediction is described emphatically in this paper. A high-performance filtering tracker, which was then extended into a predictor to estimate the future moving state of target, was built up through the research on the maneuvering target tracking (MTT) technique, thereby the “interacting multiple-model(IMM) prediction algorithm” is put forward. As the simulation shows, this algorithm has high precision for predicton and good self-adaptive capability. Besides, the method of the prediction gate computation is given in this paper.
2007, 28(1): 38-42.
Abstract:
Zernike polynomials are used as interface for opto-mechanical analysis because the items of Zernike polynomials have corresponding meanings to Seidel aberrations, because the result of finite element analysis can not be directly used by optical software. At present, optical-axis component of nodal surface displacement to the original surface is fitted by Zernike polynomials, which is not accurate. Some algorithms of surface corrected displacement are described and compared. Each corrected displacement is compared with specific examples, and they are fitted by Zernike polynomials. From the difference of fitting coefficient, it is discovered that the corrected displacement must be adopted if the surface curvature is large. It is concluded that both axial and normal corrected displacements adopt the method from original nodes if the original surface equation is unknown, the axial corrected displacement uses the method from the deformed nodes and the normal corrected displacement makes use of the methods from original nodes if the original surface equation is known.
Zernike polynomials are used as interface for opto-mechanical analysis because the items of Zernike polynomials have corresponding meanings to Seidel aberrations, because the result of finite element analysis can not be directly used by optical software. At present, optical-axis component of nodal surface displacement to the original surface is fitted by Zernike polynomials, which is not accurate. Some algorithms of surface corrected displacement are described and compared. Each corrected displacement is compared with specific examples, and they are fitted by Zernike polynomials. From the difference of fitting coefficient, it is discovered that the corrected displacement must be adopted if the surface curvature is large. It is concluded that both axial and normal corrected displacements adopt the method from original nodes if the original surface equation is unknown, the axial corrected displacement uses the method from the deformed nodes and the normal corrected displacement makes use of the methods from original nodes if the original surface equation is known.
2007, 28(1): 43-46.
Abstract:
In order to achieve a proper structure and support for the primary mirror used in the space optic remote sensor and test the optical performance of a new optic material (SiC), 3D solid models were built for the primary mirror subassemblies. The mass and the center-of-mass of the primary mirror are analyzed for the different lightweight structures used on the backside of the mirror with the finite-element simulation method. Several finite-element models of the primary mirror were built with appropriate MPC boundary constraint. The effect of the mirror weight on its surface form accuracy during the fabrication and testing process is analyzed with finite-element method. The optimal structure for the mirror and its support were achieved through the comparison of simulation results and optimized lightweight design. The optimized weight reaches 75.6% of the original value, the RMS of the mirror surface is 12.53nm and the Pv value is 54.52nm. The result shows that the weight, stiffness and surface accuracy of the primary mirror meet the engineering requirement.
In order to achieve a proper structure and support for the primary mirror used in the space optic remote sensor and test the optical performance of a new optic material (SiC), 3D solid models were built for the primary mirror subassemblies. The mass and the center-of-mass of the primary mirror are analyzed for the different lightweight structures used on the backside of the mirror with the finite-element simulation method. Several finite-element models of the primary mirror were built with appropriate MPC boundary constraint. The effect of the mirror weight on its surface form accuracy during the fabrication and testing process is analyzed with finite-element method. The optimal structure for the mirror and its support were achieved through the comparison of simulation results and optimized lightweight design. The optimized weight reaches 75.6% of the original value, the RMS of the mirror surface is 12.53nm and the Pv value is 54.52nm. The result shows that the weight, stiffness and surface accuracy of the primary mirror meet the engineering requirement.
2007, 28(1): 47-50.
Abstract:
For fabricating the autostereoscopic liquid-crystal display panel, the backlight was changed and the front side of the panel was modified. A liquid-crystal device was inserted between the backlight and the TFT LCD panel. Every pixel in the device is a slit. By the Moire fringe (picket fence effect), the device and LCD panel were aligned. When driven with voltage, the backlight is converted into a large number of thin, bright, vertical illuminating lines, between which there is a dark space. Every light source corresponds to four columns of subpixels as the liquid-crystal display panel is illuminated. Sitting at the average viewing distance in front of the display, the observer′s left eye sees only the information on some columns of sub-pixels, and the right eye sees only what is on the other columns. Without voltages, the backlight functions just like the normal LCD, the module can display the normal two-dimension images. The front side of anti-glare polarizer is coated with an anti-reflective layer to avoid light diffusion. The autostereoscopic TFT liquid-crystal display module is a multi-view system, and can display stereo and plane images. The technology can be adopted in mass production.
For fabricating the autostereoscopic liquid-crystal display panel, the backlight was changed and the front side of the panel was modified. A liquid-crystal device was inserted between the backlight and the TFT LCD panel. Every pixel in the device is a slit. By the Moire fringe (picket fence effect), the device and LCD panel were aligned. When driven with voltage, the backlight is converted into a large number of thin, bright, vertical illuminating lines, between which there is a dark space. Every light source corresponds to four columns of subpixels as the liquid-crystal display panel is illuminated. Sitting at the average viewing distance in front of the display, the observer′s left eye sees only the information on some columns of sub-pixels, and the right eye sees only what is on the other columns. Without voltages, the backlight functions just like the normal LCD, the module can display the normal two-dimension images. The front side of anti-glare polarizer is coated with an anti-reflective layer to avoid light diffusion. The autostereoscopic TFT liquid-crystal display module is a multi-view system, and can display stereo and plane images. The technology can be adopted in mass production.
2007, 28(1): 51-54.
Abstract:
In order to study the influence of chemistry structure of FDLC film on optical property, the fluorinated diamond-like carbon(FDLC) films were deposited on the glass substrate with the method of PECVD, and analyzed by AES, FTIR and UV-VIS. The result shows that the deposited films are typical diamond-like structure and the fluorine in the films exists in the form of C-F2 key; the content of C-F2, increases in the first period and then reduces as the temperature continuously rises in the deposition process; the sp3 content of FDLC films decreases and the sp2 content increases when the fluorine content increases; the optical band gap has a close relationship with the content of sp2 key, and the more the sp2 content is, the smaller the optical band gap will be.
In order to study the influence of chemistry structure of FDLC film on optical property, the fluorinated diamond-like carbon(FDLC) films were deposited on the glass substrate with the method of PECVD, and analyzed by AES, FTIR and UV-VIS. The result shows that the deposited films are typical diamond-like structure and the fluorine in the films exists in the form of C-F2 key; the content of C-F2, increases in the first period and then reduces as the temperature continuously rises in the deposition process; the sp3 content of FDLC films decreases and the sp2 content increases when the fluorine content increases; the optical band gap has a close relationship with the content of sp2 key, and the more the sp2 content is, the smaller the optical band gap will be.
2007, 28(1): 55-57.
Abstract:
A spectral camera lens with the relative aperture of 1∶1 is introduced. The complicated Petzval structure is converted into a triplet structure based on aspheric surface. The primary optical properties are: f′=120mm, F=1, τ≥90%. The spatial frequency is greater than 20lp/mm when the MTF value of the optical system is equal to 0.85. The lens structure is optimized to facilitate the machining of the aspheric surface. Several kinds of aberration curves and the MTF data are given, and the further possible improvement for the optical system is explored.
A spectral camera lens with the relative aperture of 1∶1 is introduced. The complicated Petzval structure is converted into a triplet structure based on aspheric surface. The primary optical properties are: f′=120mm, F=1, τ≥90%. The spatial frequency is greater than 20lp/mm when the MTF value of the optical system is equal to 0.85. The lens structure is optimized to facilitate the machining of the aspheric surface. Several kinds of aberration curves and the MTF data are given, and the further possible improvement for the optical system is explored.
2007, 28(1): 58-62.
Abstract:
A zoom projection lens is designed to meet the requirements of different sizes of big rear-projection screen with the same light engine and screen location. Since the optical system to be designed should have a big relative aperture, middle field of view and small zoom ratio, the concept of zoom system is selected. The positive mechanical compensation configuration was adopted, the proper magnifications of the zoom configuration were chosen and the Gauss roots were derived. The appropriate primal configurations based on each subassembly are chosen. The optimization design is carried out with ZEMAX optical design software. The distortion of the zoom system is improved, and the modulation transfer function (MTF) is used to evaluate the system. The design and assessment results indicate that the optical performance and image quality of the zoom projection lens system meet the design specification, and can be used in big screen TV, ranging from 101.6cm to 177.8cm.
A zoom projection lens is designed to meet the requirements of different sizes of big rear-projection screen with the same light engine and screen location. Since the optical system to be designed should have a big relative aperture, middle field of view and small zoom ratio, the concept of zoom system is selected. The positive mechanical compensation configuration was adopted, the proper magnifications of the zoom configuration were chosen and the Gauss roots were derived. The appropriate primal configurations based on each subassembly are chosen. The optimization design is carried out with ZEMAX optical design software. The distortion of the zoom system is improved, and the modulation transfer function (MTF) is used to evaluate the system. The design and assessment results indicate that the optical performance and image quality of the zoom projection lens system meet the design specification, and can be used in big screen TV, ranging from 101.6cm to 177.8cm.
2007, 28(1): 63-67.
Abstract:
A mathematical parameter δ is adopted to assess the different space distribution in two laser fields. The effect of the pumping light space distribution on the quality of the ground-mode oscillating beam is analyzed by applying δ in the resonant cavity. The analysis for the effect shows that the ground-mode oscillating beam will drift off the Gauss distribution if the nonequilibrium gain distribution is caused by pumping light in the laser medium. With the parameterδ, the quantitative estimation was carried out for the effect of the pump light on the quality of oscillating beam. The investigation shows that the parameterδ, can directly represent the effect of pumping light distribution on the beam quality of laser, and the value of the parameterδ can be used to judge the pumping light distribution quality. As for the endpumping DPL with continuous operation, the most ideal distribution mode of the pumping light is the Gauss pumping light and its diameter is equal to that of the fundamentalmode Gauss oscillating beam of the resonant cavity.
A mathematical parameter δ is adopted to assess the different space distribution in two laser fields. The effect of the pumping light space distribution on the quality of the ground-mode oscillating beam is analyzed by applying δ in the resonant cavity. The analysis for the effect shows that the ground-mode oscillating beam will drift off the Gauss distribution if the nonequilibrium gain distribution is caused by pumping light in the laser medium. With the parameterδ, the quantitative estimation was carried out for the effect of the pump light on the quality of oscillating beam. The investigation shows that the parameterδ, can directly represent the effect of pumping light distribution on the beam quality of laser, and the value of the parameterδ can be used to judge the pumping light distribution quality. As for the endpumping DPL with continuous operation, the most ideal distribution mode of the pumping light is the Gauss pumping light and its diameter is equal to that of the fundamentalmode Gauss oscillating beam of the resonant cavity.
2007, 28(1): 68-71.
Abstract:
The spectrometer based on linear optical detector has the advantage of multispectrum channel detection and it plays an important role in massspectrometry. The wavelength calibration for the spectrometer is discussed. A concept of using laser induced breakthrough atomic spectrum to enrich characteristic wavelength spectrum for wavelength calibration is put forward. A concave grating spectrometer, a 2048 elements CCD and a low voltage mercury lamp were used to carry out laser induced breakthrough spectrum test with 5 samples, such as Cu, Al, Mg, Ca and Si. The selected 10 laser induced atomic spectrum wavelength data and the 10 characteristic spectrum lines achieved with mercury lamp were used to recalibrate the wavelengths of the grating spectrometer. The feasibility of the concept is effectively validated.
The spectrometer based on linear optical detector has the advantage of multispectrum channel detection and it plays an important role in massspectrometry. The wavelength calibration for the spectrometer is discussed. A concept of using laser induced breakthrough atomic spectrum to enrich characteristic wavelength spectrum for wavelength calibration is put forward. A concave grating spectrometer, a 2048 elements CCD and a low voltage mercury lamp were used to carry out laser induced breakthrough spectrum test with 5 samples, such as Cu, Al, Mg, Ca and Si. The selected 10 laser induced atomic spectrum wavelength data and the 10 characteristic spectrum lines achieved with mercury lamp were used to recalibrate the wavelengths of the grating spectrometer. The feasibility of the concept is effectively validated.
2007, 28(1): 72-76.
Abstract:
The comprehensive test technology for laser peak power parameter is investigated based on the characteristics of wavelength, power, and pulse width of pulse laser transmitted from laser transmitting sets operating in several common wavebands. Utilizing the self-developed universal test platform, the corresponding high sensitivity detectors are selected for different wavelengths, suitable attenuating plates are adopted for different power ranges, and the proper widening magnifications and fast discharge circuits are designed for narrower laser pulses with the advanced technology of multiband optronic detection, integrated assembled optical design and circuit design. Experimental results indicate that the technology is an effective way to implement the comprehensive test of the multiband laser peak power.
The comprehensive test technology for laser peak power parameter is investigated based on the characteristics of wavelength, power, and pulse width of pulse laser transmitted from laser transmitting sets operating in several common wavebands. Utilizing the self-developed universal test platform, the corresponding high sensitivity detectors are selected for different wavelengths, suitable attenuating plates are adopted for different power ranges, and the proper widening magnifications and fast discharge circuits are designed for narrower laser pulses with the advanced technology of multiband optronic detection, integrated assembled optical design and circuit design. Experimental results indicate that the technology is an effective way to implement the comprehensive test of the multiband laser peak power.
2007, 28(1): 77-81.
Abstract:
A novel high-sensitivity fiber Bragg grating (FBG) pressure sensor was designed, which was mainly composed of the setup of the opening loop and the aluminum-foil pipe. With the opening loop mechanism and the bandwidth code incorporated, the pressure sensor based on the bandwidth tuning principle of FBG is implemented for the temperature-independent pressure measurement. The experimental results indicate that the sensor is very sensitive to pressure, which is up to 2.50×103nm/MPa, and the experimental results agree with the theoretical analysis. The pressure sensitivity and measurement range can be designed and altered by changing the material and parameter of the opening loop and aluminum-foil pipe.
A novel high-sensitivity fiber Bragg grating (FBG) pressure sensor was designed, which was mainly composed of the setup of the opening loop and the aluminum-foil pipe. With the opening loop mechanism and the bandwidth code incorporated, the pressure sensor based on the bandwidth tuning principle of FBG is implemented for the temperature-independent pressure measurement. The experimental results indicate that the sensor is very sensitive to pressure, which is up to 2.50×103nm/MPa, and the experimental results agree with the theoretical analysis. The pressure sensitivity and measurement range can be designed and altered by changing the material and parameter of the opening loop and aluminum-foil pipe.
2007, 28(1): 82-85.
Abstract:
The split-step Fourier transform method (SSFM) and its simulation process are presented in detail. Matlab was used to simulate the soliton propagation in the optical fiber. The influence of optical fiber attenuation on soliton propagation is discussed. It is pointed out that two optical solitons will strongly affect each other if they are very close, which makes the soliton shape aberrant. The EDFA was adopted to compensate the power of the soliton and its result was reviewed. It is concluded that dispersion is the major limitation in the optical soliton communication, 980 nm laser is selected to pump the EDFA to obtain better result.
The split-step Fourier transform method (SSFM) and its simulation process are presented in detail. Matlab was used to simulate the soliton propagation in the optical fiber. The influence of optical fiber attenuation on soliton propagation is discussed. It is pointed out that two optical solitons will strongly affect each other if they are very close, which makes the soliton shape aberrant. The EDFA was adopted to compensate the power of the soliton and its result was reviewed. It is concluded that dispersion is the major limitation in the optical soliton communication, 980 nm laser is selected to pump the EDFA to obtain better result.
2007, 28(1): 86-91.
Abstract:
The fiber-optic sensor is a high sensitive sensor and signal detection technique is one of its key techniques. Some signal detection methods of fiber-optic sensors are summarized in this paper. The principle of the phenomena of phase induced signal fade in interferometric fiber-optic sensors is analyzed. The basic operation principles and characteristics of various anti-phase induced signal fade detection methods are introduced. Several typical methods are analyzed. Their main performances are evaluated and the future of the above mentioned methods is predicted.
The fiber-optic sensor is a high sensitive sensor and signal detection technique is one of its key techniques. Some signal detection methods of fiber-optic sensors are summarized in this paper. The principle of the phenomena of phase induced signal fade in interferometric fiber-optic sensors is analyzed. The basic operation principles and characteristics of various anti-phase induced signal fade detection methods are introduced. Several typical methods are analyzed. Their main performances are evaluated and the future of the above mentioned methods is predicted.
2007, 28(1): 92-96.
Abstract:
Vibration measurement by digital speckle pattern interferometry (DSPI) has the merits of high precision, no-contact and full-field measurement. Because the fringes achieved by the DSPI time-average vibration measurement are Bessel fringes, its quantificational analysis is difficult. The quasi-phase-shifting technique of Bessel fringes is used for the DSPI vibration quantificational analysis. A bias reference vibration at the same frequency is introduced into the reference beam as an object vibration. The Bessel fringes will shift when the phase of the bias reference vibration changes, which is equivalent to the phase-shifting of cosine fringes. So the Bessel fringes of DSPI vibration measurement can be analyzed quantitatively through the phase-shifting algorithm. A novel DSPI system for vibration quantificational analysis is developed. A low voltage phase-stepper and the measurement control electric circuit are designed and fabricated. The vibration testing results of a circumference fixed circular disc and a four-side mixed square copper piece are given. The vibration modality can be measured conveniently through this system, and the quality of the measurement result is good.
Vibration measurement by digital speckle pattern interferometry (DSPI) has the merits of high precision, no-contact and full-field measurement. Because the fringes achieved by the DSPI time-average vibration measurement are Bessel fringes, its quantificational analysis is difficult. The quasi-phase-shifting technique of Bessel fringes is used for the DSPI vibration quantificational analysis. A bias reference vibration at the same frequency is introduced into the reference beam as an object vibration. The Bessel fringes will shift when the phase of the bias reference vibration changes, which is equivalent to the phase-shifting of cosine fringes. So the Bessel fringes of DSPI vibration measurement can be analyzed quantitatively through the phase-shifting algorithm. A novel DSPI system for vibration quantificational analysis is developed. A low voltage phase-stepper and the measurement control electric circuit are designed and fabricated. The vibration testing results of a circumference fixed circular disc and a four-side mixed square copper piece are given. The vibration modality can be measured conveniently through this system, and the quality of the measurement result is good.
2007, 28(1): 97-101.
Abstract:
The vibration characteristic of loudspeakers is investigated experimentally, based on the self-mixing interference effect of semiconductor laser diode. As a target, a reflector with reflectivity of 95% is mounted on the loudspeaker, which is driven by a sine signal at 50Hz frequency, and a self-mixing interference signal is obtained with an extremely simple optical setup. Then the vibration amplitude of loudspeaker is figured out through the interference fringe counting method. The results show that the vibration amplitude, which responses to the driving voltage, exhibits good linearity in corresponding range. It is a fast, low-cost and easy to perform method that does not require special driving device or other optical apparatus. This experiment illustrates the effectiveness of the self-mixing technique in the field of vibration measurements.
The vibration characteristic of loudspeakers is investigated experimentally, based on the self-mixing interference effect of semiconductor laser diode. As a target, a reflector with reflectivity of 95% is mounted on the loudspeaker, which is driven by a sine signal at 50Hz frequency, and a self-mixing interference signal is obtained with an extremely simple optical setup. Then the vibration amplitude of loudspeaker is figured out through the interference fringe counting method. The results show that the vibration amplitude, which responses to the driving voltage, exhibits good linearity in corresponding range. It is a fast, low-cost and easy to perform method that does not require special driving device or other optical apparatus. This experiment illustrates the effectiveness of the self-mixing technique in the field of vibration measurements.
2007, 28(1): 102-104.
Abstract:
In order to monitor the cement grout density accurately and dynamically in grouting practice, a detection instrument incorporating a CR105 photomultiplier tube as optic sensor was designed. The instrument, which took Cs-137 as light source, CR105 photomultiplier tube as photosensitive device and 196KB single chip processor as micro-processor, realized γ ray detection and data processing through the customized signal process circuit, display circuit and modularized software. The experimental results show that the instrument can successfully monitor the density of the cement grout in harsh environment. The detector of the instrument functions properly when it is installed in the hot, damp and dusty construction site. The measurement is fast and accurate.
In order to monitor the cement grout density accurately and dynamically in grouting practice, a detection instrument incorporating a CR105 photomultiplier tube as optic sensor was designed. The instrument, which took Cs-137 as light source, CR105 photomultiplier tube as photosensitive device and 196KB single chip processor as micro-processor, realized γ ray detection and data processing through the customized signal process circuit, display circuit and modularized software. The experimental results show that the instrument can successfully monitor the density of the cement grout in harsh environment. The detector of the instrument functions properly when it is installed in the hot, damp and dusty construction site. The measurement is fast and accurate.
2007, 28(1): 105-108.
Abstract:
A grating spectrum detecting system was designed to detect the formaldehyde concentration effectively and quickly. The spectrum detecting system mainly consists of optical system, signal collection system and computer processing system. The hardware circuits of the whole system include the driving circuit of the photoelectric magnification tube, preamplified filtering circuit, analogy and digital conversion circuit, and data collection and transmission circuit. The experiment conditions for determination of formaldehyde concentration in the air detected by MBTH spectrophotometer are investigated. The factors affecting experiment results are analyzed,experimental results for spectrum detection are obtained, the relevant conclusions are analyzed and reviewed. The transmission spectrum of the formaldehyde analytical solution，in which the formaldehyde concentration is fixed, can be correctly probed by the designed weak-light detection system.
A grating spectrum detecting system was designed to detect the formaldehyde concentration effectively and quickly. The spectrum detecting system mainly consists of optical system, signal collection system and computer processing system. The hardware circuits of the whole system include the driving circuit of the photoelectric magnification tube, preamplified filtering circuit, analogy and digital conversion circuit, and data collection and transmission circuit. The experiment conditions for determination of formaldehyde concentration in the air detected by MBTH spectrophotometer are investigated. The factors affecting experiment results are analyzed,experimental results for spectrum detection are obtained, the relevant conclusions are analyzed and reviewed. The transmission spectrum of the formaldehyde analytical solution，in which the formaldehyde concentration is fixed, can be correctly probed by the designed weak-light detection system.
2007, 28(1): 109-114.
Abstract:
Based on the Hwey-Lan Liou eye model and the equivalent rule，crystal lens is replaced with accommodative intraocular lens (AIOL) for imaging at infinite distance. Based on the analysis of imaging quality of human eye, the displacement, medium refractive index, central thickness, structure, aspheric refractive surface of the AIOL are studied with ZEMAX to implement light ray tracing method. Simulation results indicate that the displacement of AIOL has the greatest impact on its tunability; while it is hardly affected by the medium refractive index, central thickness, and structure. The AIOL with aspheric surface has better tunability.
Based on the Hwey-Lan Liou eye model and the equivalent rule，crystal lens is replaced with accommodative intraocular lens (AIOL) for imaging at infinite distance. Based on the analysis of imaging quality of human eye, the displacement, medium refractive index, central thickness, structure, aspheric refractive surface of the AIOL are studied with ZEMAX to implement light ray tracing method. Simulation results indicate that the displacement of AIOL has the greatest impact on its tunability; while it is hardly affected by the medium refractive index, central thickness, and structure. The AIOL with aspheric surface has better tunability.
2007, 28(1): 115-120.
Abstract:
Based on the application difference in Rayleigh-Debye-Gans theory and CEM model, MCEM (modify cocentral ellipse model) is established to eliminate the influence of the orientation effect of the shape-cell particles on measurement result in light scattering cell particles. Based on the MCEM theory, the variation of the light scattering intensity distribution of cells is discussed systematically at the different incidence angles, the dynamic response relationship between the light-scattering intensity distribution and the relevant physical characteristic of the karyocyte at the different incidence angles was obtained. In addition, the scattering intensity distribution function of the karyocyte is acquired by fitting the scattering intensity distribution. The error analysis shows that the fitting result can be used in the numerical inversion calculation effectively for the light-scattering measurement of the real cell.
Based on the application difference in Rayleigh-Debye-Gans theory and CEM model, MCEM (modify cocentral ellipse model) is established to eliminate the influence of the orientation effect of the shape-cell particles on measurement result in light scattering cell particles. Based on the MCEM theory, the variation of the light scattering intensity distribution of cells is discussed systematically at the different incidence angles, the dynamic response relationship between the light-scattering intensity distribution and the relevant physical characteristic of the karyocyte at the different incidence angles was obtained. In addition, the scattering intensity distribution function of the karyocyte is acquired by fitting the scattering intensity distribution. The error analysis shows that the fitting result can be used in the numerical inversion calculation effectively for the light-scattering measurement of the real cell.
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