Three-dimensional measurement is the base part for reverse engineering. The paper developed a new flexible and fast optical measurement method based on multi-view geometry theory. At first, feature points are detected and matched with improved SIFT algorithm. The Hellinger Kernel is used to estimate the histogram distance instead of traditional Euclidean distance, which is immunity to the weak texture image; then a new filter three-principle for filtering the calculation of essential matrix is designed, the essential matrix is calculated using the improved a Contrario Ransac filter method. One view point cloud is constructed accurately with two view images; after this, the overlapped features are used to eliminate the accumulated errors caused by added view images, which improved the camera’s position precision. At last, the method is verified with the application of dental restoration CAD/CAM, experiment results show that the proposed method is fast, accurate and flexible for tooth 3D measurement.
This paper presents a novel registration method by encoding feature point identification and spatial location to make the registration of 3D measurement easy. A new proposed decoding algorithm based on polar coordinate segmentation is first used for identification feature point, the feature points are then measured and constructed. The overlapped 3D measurement feature points within two views are used to unify coordinate system, so the feature points of each view are achieved for global spatial location. The object is finally measured with any view which only contains at least three feature points. The unconstrained 3D registration is acquired with the feature points matching between single measurement view and global spatial points. Our experiments show that the proposed method is convenient and effective, and greatly enhances the flexibility of 3D measurement applications.
The random-direction partial derivatives in optical deflection equations were transformed into numerical differences in
reference frames for tomography. The nonlinear deflection equations were transformed into linear tomography ones. A
detecting ray will turn its propagating direction when it runs through a heterogeneous refractive index field. Its deflecting
angle a is the function of refractive index n by n's first order partial derivative. So, the optical deflection equation
involves nonlinear first order partial derivative. This kind of detecting ray equations can't be resolved by tomography
algorithm directly. At first, the nonlinear partial derivative should be transformed into numerical difference. Here, a
practical transforming algorithm was put forward. The diagnosed field was divided into tiny foursquare grids. Each grid
and its refractive index were approximated to a correct cone with an irregular bottom. With the approximation, the space
partial increment calculation was much simplified at any grid, in any direction and to any detecting ray. It was assumed
that the refractive index distribution should be coplanar in the area between three grid centers of the three close-adjacent
grids. With the assumption, the refractive index partial increment could be calculated with a numerical difference
function of close-adjacent grid refractive indexes. With the approximation and assumption, the partial derivative was
transformed into numerical difference. As the result, partial derivative related to any detecting ray could be transformed
into numerical difference. Nonlinear deflection equations could be transformed into linear difference ones. So, the
deflected angles can directly be applied to reconstruction as projections.
A new deflection tomography system was put forward and named Auto-adapted Iterative Deflection Tomography
(AIDT). It was tested to approach accurate reconstruction of a high frequency field containing shock waves with
sufficient projections. A high frequency field was constructed with Gauss and rectangle window functions. It was
simulated to project in all directions with angle resolving rate per degree. Two cross projections was selected to simulate
reconstructing the model field by AIDT. Then, the number of projections was increased step by step in order to approach
the accurate values of the model. All reconstructed results were studied. As a result, all high frequency sections are
distorted much. With a few projections, such as two projections, the reconstructed results lost the basic characteristics of
the model. With projections increasing, the distortions get lighter and lighter. Near the critical projections, such as
twenty-four projections, the reconstructed field becomes similar to the model except some high frequency sections.
When eighty-four projections are employed, the reconstructed result is in accord with the model. In this case, the Mean
Square Error(MSE) is 0.00003609. But up to one hundred and eighty projections, the reconstructed result almost
stopped improving. In this case, the MSE is 0.00003231. As we know, these are most accurate reconstructions to now.
AIDT can accurately reconstruct high frequency fields with shock waves.
Now, spectra technology is widely used in the biomedicine research,so this study investigates variation of the
fluorescence spectra in different excitation wavelength, and the spectra of serum with different glucose concentration is
tested in the excitation wavelength of 240nm to 280nm. The experimental result shows that the correlation between the
serum fluorescence intensity and the excitation light is very close, when the excitation light is in the ultraviolet wave
band, the fluorescence of serum is intensive. There is a violent fluorescence emission wavelength, which is 300nm to
410nm, while the excitation wavelength ranges from 220nm to 290nm, and the peaks wavelength are 330nm and
370nm. From 240nm to 280nm, the serum fluorescence intensity increases synchronously with the glucose concentration,
and the relationship between the fluorescence peak wavelength and the glucose concentration is almost in line. In this
way the blood sugar concentration can be estimated by the fluorescence spectra peak wavelength when the excitation
wavelength is from 240nm to 280nm, which is effective. It provides experimental foundation for the wide use of spectra
technology in medical diagnose, and the effectiv method to test the blood sugar concentration.
It was demonstrated that the lowest sampling frequency <i>f</i><sub>min_sample</sub> doesn't exist in mathematics. With mathematical
analysis, the principles of sampling and reconstructing a continuous signal were strictly calculated. We found that the
spectra of sampling data at critical sampling frequency <i>f</i><sub>critical_sample</sub> should overlap at the highest frequency <i>f</i><sub>max</sub> of the
continuous signal. The <i>f</i><sub>critical_sample</sub> was defined as double of the <i>f</i><sub>max</sub>, viz. <i>f</i><sub>critical_sample</sub>=2<i>f</i><sub>max</sub>. As we know, the
reconstructed signal will be distorted with this kind of overlapped spectra. Here, we will further illustrate the theoretical
results. Aided with Fast Fourier Transform(FFT), the critical sampling and the process reconstructing continuous-time
signal from it were discussed by spectroscopy. A symmetrical frequency-limited spectrum <i>F</i>(ω) was constructed with
three modified rise-cosine pulses. Its corresponding time-domain signal <i>f(t)</i> was worked out theoretically. <i>f(t)</i> was
sampled with δ<sub>T</sub>(t). By modifying T, the critical sampling signal was obtained. With FFT, the spectrum F<sub>d</sub>(ω)of the
sampling signal was figured out. The calculated <i>F</i><sub>d</sub>(ω) was compared with the constructed F(ω), and was analyzed for
observing frequency alias. A cycle of <i>F</i><sub>d</sub>(ω) for restoring the continuous signal could be obtained when F<sub>d</sub>(ω) was
filtered by an ideal low-passed filter. With FFT, a continuous signal was reconstructed from it. As the results, the spectra
of sampling data at the <i>f</i><sub>critical_sample</sub>overlapped at the f<sub>max</sub>. The reconstructed signal distorted obviously. So, the lowest
sampling frequency <i>f</i><sub>min_sample </sub>doesn't exist. The sampling theorem couldn't include equal sign. It is unscientific to say
that the <i>f</i> <sub>min_sample </sub>equal to double of the <i>f</i><sub>max</sub>.
A new deflection tomography algorithm was suggested and tested with a simulated flow field. The programs
calculating deflection projection and inverse projection were worked out based on optical refraction principle and
mathematical, physical significance of tomography. With our home-made <i>Simple Self-correlative Algebraic
Reconstruction Technique </i>(SSART), a new deflection tomography algorithm was programmed and named <i>auto-adapted
deflection tomography system</i>. A section of a complex flow field was simulated with Gauss and rectangle window
functions. One positive and one negative Gauss peaks were constructed on the section in order to make the model
contain double-polar components. One square tower was constructed on the section in order to make the model contain
much more high-frequency waves. The deflection projections were figured out according to the tomography algorithm
with direction interval one degree. So, we got 180 direction projections in total. 12 projections were selected out by
direction step 15 degree, and 84 projections were picked out by direction interval 2 or 3 degree. The section was
reconstructed with the projections by SSART. The reconstructed results were compared with the model. The
reconstructive effect was estimated with Mean-square error(MSE) and Peak error(PE). As the result, the system could
reconstruct the simulated field accurately. With twelve projections, MSE was about from 0.0001 to 0.0006 at the end of
300 cycle iterations, and PE was about from 0.007 to 0.020. With selected 84 projections, the MSE was 0.00000999, and
PE was 0.00013142. So, the <i>auto-adapted deflection tomography system </i>can accurately reconstruct complex flow fields.
In this paper, the kinetic equation of photo-initiated reaction was set up by measuring the photoinitiator absorbency
and the exposure time during the exposure process based on the spectroscopic analysis and reaction kinetics. And an
effective and convenient computation model for quantum yields of photoinitiators was established through further
analysis of the exposure process. The kinetics curve of photoinitiator 1173 (HMPP) was determined according to this
method. The results show that the reaction is consistent with the kinetic model established in this paper. And the
quantum yield is 2.4% at the main absorption peak (247nm).
Traditional optical image processing system is mostly based on PC, and is restricted in many fields. A novel system of
optical image processing is advanced. It consists of two parts: image acquisition system and image processing system.
Image acquisition system is made up of FPGA, CMOS image sensor and image buffer memory. DSP is selected as the
key element of the image processing system. An extra image buffer memory and an image memory are also used.
Program of optical image processing is written into DSP. Images processed can also be transmitted to display interfaces,
such as LCD, TV, etc. The system can operate conveniently, smoothly and inerrably with high speed and precision.
The paper presents a novel fiber optic microbend sensor with intelligent self-healing function, which is based upon
the photocurable technology and the mode-coupling theory. In the research, a kind of photocurable material is developed
and injected into the flexible hollow-center fiber embodying the sensitive optic fiber. According to the theory of fiber
optic microbend sensors, the microbending mechanism causes part of the optical power to be radiated out of the fiber due
to the mode-coupling. Especially when the damage of the sensitive optic fiber occurs due to the extremely small bending
radius, the radiation power will increase rapidly. We use the radiation power as the curing light to initiate the
photopolymerization of the photocurable material surrounding the sensitive optic fiber. The scale and speed of the
photochemistry reaction mainly depend on the radiation power and the microbend degree. By this way, the photocurable
material can repair the damaged area in real time according to the damaged state. This paper describes the design and
performances of the intelligent self-healing fiber optic microbend sensor in detail. The experimental results reveal that
the sensor has the excellent sensing property and can adjust its repairing ability according to the damaged degree
In this paper, the fluorescence spectrum of serum and neural network theory was combined and used to analyze the blood
cholesterol concentration. Studies show that there is fluorescence spectrum in the wave band 425 to 600 nm with a peak
near 460nm when the excitation wavelength is 410nm; the shape of curves keeps almost consistent with cholesterol
concentration; there is no significant correlation between fluorescence intensity at 460nm and cholesterol concentration,
but random, which indicates that there are other fluorescence emission at 460nm . Based on the evident correlation
between serum fluorescence intensity and cholesterol concentration in the wave band of 450 to 470nm , a neural network
model was built to determine the cholesterol concentration. It provides a new spectral test method of cholesterol
Life sciences is an important field of scientific research nowadays .On this important subject to the human blood measure,
this paper puts forward applying infrared spectrum analysis technology to this research subject less likely to be set foot
of diagnosis on disease. This paper gives infrared spectrums of cholesterol serums of normal and abnormal bloods
sample within the range of certain frequency spectrum. By comparing the characteristic of the spectrums, we can
measure and judge whether the serum sample is normal or not. Results indicate the differences on the absorption rate,
position of absorption peak between normal and abnormal blood sample. A new method of medical diagnosis and
analyses is presented. Compared with the other existed blood measures methods, it is convenient and easy to popularize
for the serum infrared spectrum characteristic analysis method presented in this paper, meanwhile it has the merit of
analyses simple fast.
Blood spectrum examination has many superiorities, however , its spectrum signals often include the noise. The wavelet
transformation method has good partial analysis ability on the signal. In this paper, the author chooses the normal
person's blood serum and the high blood fat serum, carries them on the absorption spectrum examination. The author
takes the wavelet theory as the foundation, uses it in human body blood serum absorption spectrum signal
processing .Finally , it can smooth the noise well and make more useful information stand out . The normal person blood
serum renewedly structural spectrum signal appears 8 absorptions peaks at 207nm, 215nm,223nm, 230.5nm, 240nm,
267.5nm, 277nm and 284.5nm place, the high blood fat blood serum renewedly structural spectrum signal appears 9
absorption speaks at 203.5nm, 211.5nm, 219.5nm, 236nm,243.5nm, 267.5nm, 275nm, 282nm and 289nm place. From
above, the information of renewedly structural blood serum spectrum signal using the wavelet transformation method
in the wave length 200nm~300nm section increases obviously. The high blood fat blood serum sample spectrum's two
peaks positions gap between 219.5nm and the 236nm is obviously wider than the two peaks positions' gap of normal
person blood serum sample in this spectrum section. Not only so, the former owns a peak at 289nm place but the latter
This paper presents details of a novel photoelectric system for intelligent structural health monitoring in aircrafts.
Through light intensity-based experiments about loads and damages of an aircraft composite structure conducted in this
paper, the potential for structural health monitoring of the composite material is discussed. Firstly, the paper
demonstrates the design of a novel photoelectric system including an optical part and a circuit part. The former part
consists of a light resource group and fiber optical sensors. And the latter part of this system is composed of a monitoring
host and a computer, both of which work together under the instructions given by self-designed software. The schematic
hardware diagram and the flow chart of the main program of the software are specified in this paper. In order to assess
the monitoring effect, the loads experiments are carried out at different locations of a test object in which special optical
fibers are buried. Finally, the degrees of loads and damages are measured and the experimental results are discussed.
Results obtained offer feasibilities of employing the proposed photoelectric system as a monitoring device for load and
damage detection in intelligent composite structures.
With the increasing development of material technology and electronic
integration technology, optical fiber and its using in smart structure have become hot
in the field of material research. And liquid-core optical fiber is a special kind of
optical fiber, which is made using liquid material as core and polymer material as
optical layer and protective covering, and it has the characteristics of large core
diameter, high numerical aperture, large-scope and efficient spectrum transmission
and long life for using. So the liquid-core optical fiber is very suitable for spectrum
cure, ultraviolet solidification, fluorescence detection, criminal investigation and
evidence obtainment, etc, and especially as light transfer element in some new
structures for the measurement of some signals, such as concentration, voltage,
temperature, light intensity and so on. In this paper, the novel liquid-core optical fiber
is self-made, and then through the test of its light transmission performance in free
state, the relation between axial micro-bend and light-intensity loss are presented.
When the liquid-core optical fiber is micro-bent axially, along with the axial
displacement's increase, output power of light is reducing increasingly, and
approximately has linear relation to micro-displacement in a range. According to the
results liquid-core fiber-optic micro-bend sensor can be designed to measure
micro-displacement of the tested objects. Experimental data and analysis provide
experimental basis for further application of liquid-core optical fiber.
Composite material has been applied widely in aeronautics, astronautics and some other fields due to their high strength, light weight and antifatigue and etc. But in the application, composite material may be destroyed or damaged, which may have impact on its further applications. Therefore, study on the influence of behavior of composite material damage becomes a hot research. In this paper, the common composite material for aircraft is used as the test object, and a study is conducted to investigate the influence of vibration behavior of composite material damage. The authors adopt the method of light-carrier wave and time-average holography. Compared the interference fringes of composite materials before and after damage, the width of the interference fringes of hologram of the damaged composite material is narrower than that of the fringes before. It means that the off-plane displacement of each point on the test object is larger than before. Based on the elastic mechanics theory, the off-plane displacement is inverse to the bending stiffness, and the bending stiffness of the test object will decrease after it is damaged. In other words, the vibration property of the composite material changes after damages occur. The research results of the paper show that the results accord with the analysis of theory.
Based on current trends in research on techniques for repairing composite materials, this paper focuses on the compatibility between a light-cured repair material and composite materials. The repair material used in this study is intended to find applicability in techniques for repairing damaged composite materials. Test pieces of the composite material were excited by a sinusoidal acoustic source at a frequency of 1058 Hz. Time-average holographic interferograms were photographed in original, damaged, and repaired samples. By analyzing the three interferograms according to the principles of holographic interferometry, the utility of the light-cured repair material is shown.
According to the multiplicity and redundancy of the record of holography, a new method is presented. Single reference light and separable double object light or overlapped double multichannel holography of space and angle can be realized. The surface image holography supplied in this paper has simple light path, easy operation, clear reproduced image and good result of diffraction. If the noise is eliminated, the it can be generalized from double channel to multichannel, therefore the amount of information can be improved. It is a new way for the making of mould plate of moulded holography image and has a wide application prospect.
A new kind of optical fiber sensor, transmission moving-grating optical fiber sensor is presented. Optical fiber is used as light-transmitting element in this kind of sensor. Sensitive element is a couple of equal pitch gratings, the one is a fixed grating, the other is a moving grating. Light flux changes as the position of the two gratings change, then after transformed by the photoelectric conversion system, the signals are output as electronic signals. Because of its simple structure and convenient operating, this kind of sensor can be used to measure displacement, strain and other physical quantities. Theoretical analysis of this sensor and experiment results of displacement measurement are provided in this paper. The results indicate that theoretical analysis is identical with experiment results and the sensor has a certain measuring sensitivity.
Based on the rotating prism multiple holography and real- time method, we present a new technique which is a synthetic holographic interferometry. The usage of the technique can record both double-exposure hologram and single-exposure hologram on a single holofilm. The usage of rotating prism can modulate plane reference waves to record multiple holograms. When the multiple hologram is exactly restituted and the incident angle of plane reconstruction waves equals a modulated angle of plane reference wave, the reconstructed original image is at the same place as the original object. The place is used as a channel of real-time observation and the others are served to record double-exposure holograms. In this way, both single-exposure and double-exposure holographies can be realized on a holofilm. Observing simultaneously interferograms at standard state recorded by double exposure and `living fringe' provided by real-time method, we can compare the change of standard state with states of different times. The paper presents a synthetic holographic interferometry and provides a new method for precise real-time measurement.