Pathological change tends to alter tissue mechanical properties, e.g. tissue stiffness. Current elastography technology use tissue stiffness as a signature to diagnose and localize diseases. Our team focus on vibrational optical coherence elastography (OCE) for its capability to increase signal to noise ratio as well as its high resolution comparing other elastography modalities. The result highly relies on the stimulation frequency for vibrational mode might change as frequency varies. A proper frequency range is required however, there hasn’t been a consensus among the research groups. In order to find the proper frequencies, several parameters measured from real experiment are input in transient model of ANSYS to simulate vibrational pattern of the sample with driving frequencies vary from 100Hz to 1000Hz. An upper limit of frequency has been discovered finally.
A detailed image processing of laser speckle interferometry is proposed as an example for the course of postgraduate student. Several image processing methods were used together for dealing with optoelectronic imaging system, such as the partial differential equations (PDEs) are used to reduce the effect of noise, the thresholding segmentation also based on heat equation with PDEs, the central line is extracted based on image skeleton, and the branch is removed automatically, the phase level is calculated by spline interpolation method, and the fringe phase can be unwrapped. Finally, the imaging processing method was used to automatically measure the bubble in rubber with negative pressure which could be used in the tire detection.
Binocular vision imaging system, which has a small field of view, cannot reconstruct the 3-D shape of the dynamic object.
We found a linear array CCD binocular vision imaging system, which uses different calibration and reconstruct methods. On the basis of the binocular vision imaging system, the linear array CCD binocular vision imaging systems which has a wider field of view can reconstruct the 3-D morphology of objects in continuous motion, and the results are accurate. This research mainly introduces the composition and principle of linear array CCD binocular vision imaging system, including the calibration, capture, matching and reconstruction of the imaging system. The system consists of two linear array cameras which were placed in special arrangements and a horizontal moving platform that can pick up objects. The internal and external parameters of the camera are obtained by calibrating in advance. And then using the camera to capture images of moving objects, the results are then matched and 3-D reconstructed.
The linear array CCD binocular vision imaging systems can accurately measure the 3-D appearance of moving objects, this essay is of great significance to measure the 3-D morphology of moving objects.
Specialized courses play a significant role in the usage of basic knowledge in the practical application for engineering college students. The engineering data available has sharply increased since the beginning of the information age in the 20th century, providing much more approaches to study and practice. Therefore, how to guide students to make full use of resources for active engineering practice learning has become one of the key problems for specialized courses. This paper took the digital image processing course for opto-electronic information science and technology major as an example, discussed the teaching model of specialized course in the information age, put forward the "engineering resource oriented model", and fostered the ability of engineering students to use the basic knowledge to innovate and deal with specific project objectives. The fusion of engineering examples into practical training and teaching encourages students to practice independent engineering thinking.
In this paper, on the basis of considering the performance advantages of two-step method, we combines the stereo matching of binocular stereo vision with active laser scanning to calibrate the system. Above all, we select a reference camera coordinate system as the world coordinate system and unity the coordinates of two CCD cameras. And then obtain the new perspective projection matrix (PPM) of each camera after the epipolar rectification. By those, the corresponding epipolar equation of two cameras can be defined. So by utilizing the trigonometric parallax method, we can measure the space point position after distortion correction and achieve stereo matching calibration between two image points. Experiments verify that this method can improve accuracy and system stability is guaranteed. The stereo matching calibration has a simple process with low-cost, and simplifies regular maintenance work. It can acquire 3D coordinates only by planar checkerboard calibration without the need of designing specific standard target or using electronic theodolite. It is found that during the experiment two-step calibration error and lens distortion lead to the stratification of point cloud data. The proposed calibration method which combining active line laser scanning and binocular stereo vision has the both advantages of them. It has more flexible applicability. Theory analysis and experiment shows the method is reasonable.
Wavefront coding technique can extend the depth of filed (DOF) of the incoherent imaging system. Several rectangular separable phase masks (such as cubic type, exponential type, logarithmic type, sinusoidal type, rational type, et al) have been proposed and discussed, because they can extend the DOF up to ten times of the DOF of ordinary imaging system. But according to the research on them, researchers have pointed out that the images are damaged by the artifacts, which usually come from the non-linear phase transfer function (PTF) differences between the PTF used in the image restoration filter and the PTF related to real imaging condition. In order to alleviate the image artifacts in imaging systems with wavefront coding, an optimization model based on the PTF was proposed to make the PTF invariance with the defocus. Thereafter, an image restoration filter based on the average PTF in the designed depth of field was introduced along with the PTF-based optimization. The combination of the optimization and the image restoration proposed can alleviate the artifacts, which was confirmed by the imaging simulation of spoke target. The cubic phase mask (CPM) and exponential phase mask (EPM) were discussed as example.
A laser triangle scanning method and the structure of 3D-face measurement system were introduced. In presented system, a liner laser source was selected as an optical indicated signal in order to scanning a line
one times. The CCD image sensor was used to capture image of the laser line modulated by human face. The system parameters were obtained by system calibrated calculated. The lens parameters of image part of were calibrated with machine visual image method and the triangle structure parameters were calibrated with fine wire paralleled arranged. The CCD image part and line laser indicator were set with a linear motor carry which can achieve the line laser scanning form top of the head to neck. For the nose is ledge part and the eyes are sunk part, one CCD image sensor can not obtain the completed image of laser line. In this system, two CCD
image sensors were set symmetric at two sides of the laser indicator. In fact, this structure includes two laser
triangle measure units. Another novel design is there laser indicators were arranged in order to reduce the scanning time for it is difficult for human to keep static for longer time. The 3D data were calculated after
scanning. And further data processing include 3D coordinate refine, mesh calculate and surface show. Experiments show that this system has simply structure, high scanning speed and accurate. The scanning
range covers the whole head of adult, the typical resolution is 0.5mm.
Micro-sphere is the key element in ICF (Inertial Confinement Fusion).The relative position between micro-sphere and
cylindrical gold hohlraum is required to be critically accurate so that the motivation energy and transition efficiency of
the ICF can be significantly improved. Accurate detection of micro-target assembly (especially the center position error)
is necessary and indispensable to ascertain the qualities of ignitions. The micro-sphere and cylindrical gold hohlraum
have tiny dimensions and are flimsy and easy to deform. To resolve such problems, a non-contact method based on
digital image progressing is proposed to detect the center position error of micro-sphere in this paper. Canny operator is
employed to detect the gray-level gradient image. After removing the fake edge points, the images are transformed into
binary images by a dual-threshold. To increase the operation speed, a region of interest (ROI) containing only parts of the
detected target is selected by alternating manual work. A Hough transform is then selectively applied to the chosen
sub-area. The equations of the target circles and the lines can be gotten by fitting these edge points. The center position
error of micro-sphere can be obtained based on axial and radial position errors of micro-sphere. Experimental results
show that the proposed method is independent of binary thresholds and robust to additional noises. The standard
deviation of the center position error is about 2μm, and the maximum error (3σ) is less than 6μm.
Extending the depth of field (DOF) of incoherent optical systems has been an active research topic for many years, and
the extended depth of field (EDOF) system can be used in many fields. We developed a novel circular pure phase plate
to extend the DOF by a factor of 4 without decrease of optical power in image plane. The plate is divided into several
equal-area annular zones and placed in the exit pupil of a standard optical imaging system. The annular zones alternately
eliminate the influence of different defocus beside the ideal Gauss object plane. The comparisons of the MTF and PSF
curves between two systems show that the system employing the phase plate has a large DOF while preserving an
acceptable resolution. Also, the images captured by the system don't have to be restored by a digital filter before next
processing. And the simulation of imaging a spoke target in several defocused condition also confirms the EDOF of the
imaging system. The DOF can be adjusted by two parameters of the phase plate: defocus compensation parameter and
zone number. We gave the relation curves between system's performances and parameters of the plate.
The depth of field for optical imaging system is restricted according to its structure parameters. It is obviously when
optical microscopy is used, which depth of field is very small and it is lesser with larger amplification ratio. In the paper,
three main methods to extend the depth of field will be shown, and their merits and shortcomings will be analyzed. The
first method is to use optical mask. It is easy to achieve satisfied results with calculation simulation, but it is difficult to
produce this mask if it is complicated. The second method is to use image processing. Many images can be obtained
with scanning of imaging system in the direction of depth. Using image processing method, the information of each
image will be extracted, then to compose a new image with them. It is a hard work to capture these scanning images.
And it is difficult to achieve real time image. The last method is to combine the method of optical mask and image
processing. The larger depth of field for optical imaging methods can extend the image range that can be used in the
field of optical microscopy and scanning image system.
A color image of digital camera is obtained by interpolated CFA (Color Filter Array) data from single sensor digital
camera. Using JPEG compression method to interpolated data, the maximal compression ratio is less than 90:1. In this
paper, an improved compression method is discussed which applied JPEG compression to raw data after two luminance
components had been processed further. Results show that CPSNR of improved method is the highest among
conventional method and existing methods while the compression ratio is over 90:1. And another attractive result is the
image quality is better when the compression ratio up to 120:1, and the conventional JPEG compression method is
helpless at such compression ratio. The further work will be concentrate on its application with hardware support.
Film is one kind of important record median. Its quality will affect image quality directly. So, it is necessary to study how to assure its quality. Because the situation of film production in dark room, normal detect method could not satisfied the film. In order to avoid to damage film, an infrared detect system is studied. This system is design to set at the position of spreader head. If the defect of film could be found at this position, the beginner of film production line, worker could tread with it in time and reduce waster.
The infrared detect system include two sub systems. The two sub system need to detect one position all the time. One sub system is used to detect if there is defect. One CCD camera captures film image. The film image will be monitor by worker through screen. The screen should be set in light room. Another sub system is composed of object lens, image intensifier micro-channel plate and eye lens. If worker find defect from screen, he will inform another worker who worker in dark room. Another worker could find the defect through image intensifier system, and treat with it. The communication method between two workers is sound, not alarm light, because there is dark room. All of the two sub systems use infrared light as light source. The wavelength of light source is 940 nm, which is safe to film.
This system is designed for Lekai, the biggest film company of China. This system could find detect early and help worker to deal with it on site, because the detect position is the starting of film production line.
Wide film detect system, studied in the paper, is one kind of industry vision system. Wide film is useful recording medium, such as photograph, press and medicine. In the course of production, one main problem is the film is scathed by these transmit rolls. It will affect later imaging effect directly. How to assure its quality is an important task. Now, the film detection is a manual work and only some selected samples could be detected. The detection will be done after all production courses are finished. So, it is a difficult task to assure the film quality.
In the paper, a wide film detect system was studies. The film detection task could be real-time operated when the wide film detect system is assembled with production line. The film detect system, like other industry vision system, is composed of optical system, CCD sensor, image frame grabber, light source and computer. The detection principle is based on image processing method. One point need to be shown, that is a suit light source is very important to the whole detection system. The light source shouldn't damage the film and it must have enough power to assure the CCD sensor could detect. Infrared LED, which main wavelength is 940nm, was selected as source light. The detection speed is up to 90 m/min, detection width is 1300mm and detection resolution could up to 0.5mm at the operation direction and 0.05mm at the film width direction.
Surface Lambertian source is useful in the course studying the light transmission in biology organization. To simulate the source is necessary start point for researching light transmission characters in tissues. A new method for simulation Lambertian source will be introduced in the paper. Physical model and mathematical model were discussed. The physical model is base, which could be used for simulation other Lambertian objects. The mathematical model should be build in terms of simulated object, which is different from physical model. In order to assure the Lambertian characters of surface light source, the size of source and operation distance were studied by simulation. The simulation data show that this method could give satisfied results.
With the development of modern science and techology, MEMS becomes an important branch. The micro operating system becomes an interested spot. During the micromanipulation process, observing the micro components by optical microscope is a crucial technology.
Limited by the optical parameters, focus of the optical microscope is small. For example, focus of 10x object lens is about 10 micron. The observation of some bigger micro objects, which size is tens or hundreds of times of 10 micron, are certainly impossibe by one time imaging. Some researchers had tried to extend the focus by improving the structure of microscopy, but the results are not satisfying.
The optical microscope has CCD sensor as detector. Moving the object carrier, series adjusted focus images can be given. As the distance between CCD sensor and object lens is fixed, these images are with the same amplification ration. We can use computer to analysis these images for extending the focus.
Through series images to extend focus, core of this method is analyzing and processing these series images, and at last composing one image, which is clear at each vertical depth.
On this image, the position of each micro object can be measured easily. Sub-pixel processing technique makes the measure precision achieve micron degree. The distance, which is recorded while adjusting the object carrier, can help to locate the vertical position of micro object, experiments show that the locating precision could up to micron degree also.
Using this method avoids changing optical system hardware, and is easy achieved. Clear image can be got in the adjustable range of object carrier. The range of focus is extended. The precision can be up to micron degree on 3D direction. So the method is useful on observing and measuring of micro object, has theoretical and practical value.
There are many modern methods to measure large 3D curved surface, such as the method of flying time, the method of laser triangulation, the method of photogrammetry, the method of measurement with intersection of electronic-theodolites, the method of raster projection, and the method of Fourier transform profile. In this paper, these methods will be discussed respectively.
In the paper, a model of integrating sphere, which acts as a low- light-level source, is constructed on the basis of researching of the theory of integrating sphere and the method of Monte Carlo. The uniform distribution of photons is simulated by a large number of random numbers and the distribution of photons in the integrating sphere is molded. The method is practical to guide the design of integrating sphere. At last, the measurements to improve precise are discussed simultaneous.
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