Advanced optical imaging technology
2018, 47(6): 624001.
doi: 10.3788/IRLA201847.0624001
In recent years, with the rapid development of associated imaging technology, it has been widely applied in many fields and has attracted great attention. The polarization detection technology can distinguish different material objects and enhance the system ability of detecting and identifying. In this paper, with the advantages of polarization detection techniques and associated imaging techniques, the Walsh-Hadamard speckle was used to illuminate the scene, the scene reflection light was detected by time-sharing polarization, and the full Stokes polarization correlation imaging of the scene was realized. The corresponding experimental system was set up, and the imaging experiments of multi-material objects were carried out. Using the signals of different polarization states and illumination speckles, the Stokes parameters images of objects were obtained by calculating. The distinguish of different material objects and the objects with the same material and different structures in the same scene were realized. Through the evolutionary compression sampling recovery technology, the images were restored at different sampling ratios. The results show that the evolutionary compression sampling recovery technology can restore clear full polarization information at a lower sampling rate.
2018, 47(6): 624002.
doi: 10.3788/IRLA201847.0624002
In order to obtain more implosion movement information of inertial confinement fusion and measure the temporal-spatial characteristics of plasma during fusion combustion phase, the framing tube was studied whose exposure time was better than 30 ps, using electron beam pulse-dilation and composite lenses imaging technology. The reason of performance difference between two tubes was analyzed through the tubes structure, working principle and measurement. The study result shows that the MCP gated framing tube has better spatial resolution performance and the new framing tube has more excellent temporal resolution performance. The spatial resolution and exposure time of MCP gated framing tube is ~53 m(the modulation is 4%) and 97 ps, respectively. And, the new framing tube is ~74 m(the modulation is 3%) and 21 ps, respectively. The mass reliable data is provided to study inertial confinement fusion through the high temporal resolution framing imaging technology.
2017, 46(8): 824001.
doi: 10.3788/IRLA201746.0824001
Multi-aperture imaging is a new imaging method combining with compound eye concept, which has a small size, large field of view, high-resolution images reconstruction and other advantages. However, due to the low resolution of sub-images, the improvements for the image resolution and field of view are very limited. A novel imaging method which could achieve both super-resolution and large field of view was proposed. The random coded mask was designed based on the framework of compressive sensing and placed on each sub-aperture. Instead of directly imaging and converging on the image sensor, the incident light field of each sub-aperture would be modulated by the coded mask. Then, the random projections of the input object could be acquired by the low-dimension image sensor within a single exposure. Finally, the sparse representation-based optimization algorithm was applied to reconstruct super-resolution and large field of view images from all low-resolution sub-images, which had more object pixels than the number of pixels of the image sensor. Both the theoretical model and simulation results show the feasibility of the proposed method.
2017, 46(8): 824002.
doi: 10.3788/IRLA201746.0824002
The influence of intensity correlation order on correlated imaging for moving target was researched. The image quality of correlated imaging for tangential and axial moving target in different intensity correlation order was discussed by changing the signal light order and the reference light order.Based on the schematic of Nth-order lensless correlated imaging for moving target, analysis of the influence of different intensity correlation order was performed with emphasis on the correlated imaging mathematic model, and the simulation experiments were performed. The results suggest that it can not effectively eliminate the motion blur by changing the intensity correlation order, and the image quality will be better with the increase of signal light order. However, the best quality can be obtained by the lowest-order with background subtraction, and the image quality of axial moving target will decrease more serious. Moreover, this method greatly reduces system equivalent focal length and has a thin structure, which can provide theoretical guidance for the design and application of the micro-optical electromechanical system.
2016, 45(8): 824001.
doi: 10.3788/IRLA201645.0824001
Three dimensional super-resolution gated imaging(3D SRGI) is a novel scannerless 3D imaging technique, and has great potential in underwater imaging, remote surveillance and automatic navigation. The development of 3D SRGI was reviewed, and trapezoidal 3D SRGI and triangular 3D SRGI was compared from intensity states of range intensity profiles, 3D imaging step depth, signal-to-noise ratio, environmental noise sensitivity, range resolution, and range accuracy. For the improvement of 3D SRGI, advanced imaging methods were introduced including range-intensity coding imaging, real time 3D imaging and multi-pulse time delay integration imaging. Furthermore, the specific applications of 3D SRGI were summarized in low contrast target detection, target identification, and underwater 3D imaging. In addition, an overview on some recent 3D SRGI work was given in the Institute of Semiconductors, Chinese Academy of Sciences. The future development trends of three dimensional range-gated imaging are higher depth-to-range-resolution ratio and faster high-resolution 3D imaging.
2016, 45(8): 824002.
doi: 10.3788/IRLA201645.0824002
A 3D small-field imaging system was established by using the fringe projection technique to measure the small objects having large slopes and/or discontinuous surface. A stereo microscope was used to generate a small-field projecting field and to capture the deformed fringe patterns on the measured small objects. Three fringe sets having the optimum fringe numbers were coded into one major color channel to generate color fringe patterns having the maximum fringe contrast of the captured fringe images. Through one channel of the stereo microscope, a Digital Light Processing (DLP) projector projected these generated color fringe pattern images onto the measured objects surface. From another channel, the fringe patterns were deformed with regard to the object surface and captured by a color CCD camera. The absolute phase of each pixel could be calculated from the captured fringe patterns by using the optimum three-fringe numbers selection method. The relationship between the absolute phase and depth was established to move a white plate to several known positions by using an accurate linear translating stage, so the 3D shape data of the measured objects were obtained. Experimental results on measuring 3D shape of small objects show the accuracy and availability of the developed 3D imaging system.
2016, 45(8): 824003.
doi: 10.3788/IRLA201645.0824003
Conventional optical imaging require the image plane at the focal plane of the imaging lens group to get the maximum flux. So the focal length has great impact on imaging quality. In order to investigate the influence of focal length on quality of computational ghost imaging, the experiment of computational ghost imaging was constructed, and the probability density of the measurement of bucket detector was utilized to analyze the results of computational ghost imaging with different focal length and background light. The results show that the variation of focal length and background light have little effect on the quality of computational ghost imaging, which solve the problem that the defocus lead to the deterioration of quality caused by the inequality of two optical path in traditional ghost imaging. Computational ghost imaging can be realized without imaging lens and only using a bucket detector, thus avoiding the allocation of flux on the pixel dimension as well as improving the signal-to-noise ratio.Therefore, computational ghost imaging is very suitable for imaging detection under the extremely weak background.
2016, 45(8): 824004.
doi: 10.3788/IRLA201645.0824004
Color cameras are widely used in the printing industry, graphic arts, medical area, environment and many other applications. In order to save cost and maintain high colorimetric accuracy, a method that utilizing a single-channel pre-filter to calibrate color camera's spectral sensitivity curve was put forward. The pre-filter's simulation accuracy depended on the degree of matching Luther conditions, and it was impossible to match perfectly due to the limitation filter material, the film design, and the nonideal filter fabrication. The goal of this work was to design the target curve according to analyzing the influence factor of the simulate accuracy, using the continuously tunable monochromatic light source system to test the color CCD relative spectral response, selecting appropriate evaluation function model to simulate theoretical spectral transmittance, referring the CIE standard test colors and using CIE2000 color formula to evaluate the theoretical color error. This work shows that after increasing the pre-filter, the mean change of the color error is about 73%, and the color effect of the camera has been enhanced significantly.
2016, 45(8): 824005.
doi: 10.3788/IRLA201645.0824005
In order to stitch the sub-aperture data rapidly and precisely in microsphere profile inspection, the model of microsphere surface measurement was given, which was based on point diffraction interference. After analyzing the distribution of interference field lateral resolution in detail, a method of sub-aperture stitching based on mapping image matching was proposed. After equal-scale transformation of profile data, the homogenization of lateral resolution was achieved. The dimension of 3D point clouds data was reduced to a mapped 2D image for transforming the sub-aperture rotation-ship of the profile data to a translation relation on the CCD coordinate system. And the corresponding transformation offset between sub-apertures could be obtained by the feature points matching in ways of image matching algorithm, so the sub-aperture stitching could be realized. Finally, the feasibility and effectiveness of the proposed mapping image matching method for sub-aperture stitching was proved by the simulation experiment.
2016, 45(6): 624001.
doi: 10.3788/IRLA201645.0624001
Stimulated emission depletion (STED) is a kind of super resolution fluorescence microscopy imaging technology. It can break through the traditional optical diffraction limit, and make the far field optical resolution improved to less than 100 nm, which is widely used in biomedical field, and becomes one of the hotspots in optical imaging research. A STED microscope system based on ultra-continuous spectrum picoseconds pulsed white laser source was introduced, and super-resolution imaging was realized. The optimized results were discussed from the aspects of precise collimation, pulse delay and residual intensity of the STED light, therefore the best imaging effect was obtained. The experiments data of the about 25 nm diameter fluorescent microspheres imaging shows that the resolution of the system is about 60 nm, which is much higher than the diffraction limit. In addition, the system succeeds in realizing super resolution imaging of nuclear pore complexes, microtubules and microfilaments and a series of biological samples. Some obscure structures imaged in confocal microscopy can be legible in STED imaging.
2016, 45(6): 624002.
doi: 10.3788/IRLA201645.0624002
As a high-order approximation model to Radiative Transfer Equation, simplify spherical harmonic (SPN) approximation has become a hot research topic in optical molecular imaging research. However, low computational efficiency imposes restrictions on its wide applications. This paper presented a graphics processing units (GPU)-parallel accelerated strategy for solving SPN model. The proposed strategy adopted compute unified device architecture (CUDA) parallel processing architecture introduced by NVIDIA Company to build parallel acceleration of two most time-consuming modules, generation of stiffness matrix and solving linear equations. Based on the feature of CUDA, the strategy optimized the parallel computing in tasks distribution, use of memory units and data preprocessing. Simulations on phantom and digital mouse model are designed to evaluate the accelerating effect by comparing the time for system matrix generation and average time of each step iteration. Experimental results show that the overall speedup ratio is around 30 times, which exhibit the advantage and potential of the proposed strategy in optical molecular imaging.
2016, 45(5): 524001.
doi: 10.3788/IRLA201645.0524001
Image plane intersection interference imaging spectroscopy is a kind of compact imaging spectrometer technology, which has characteristics of small volume and light weight, and is used for small satellite remote sensing mission or airborne photoelectric reconnaissance. Image plane intersection interference imaging spectroscopy was studied. The design scheme of angle shear beam splitter was given based on Mach-Zehnder composed of prisms. Work principle and design method were discussed in detail. The angle shear of beam splitter based on Mach-Zehnder was analyzed under certain spectrum resolution combined design example. At same time, object characteristics of image plane intersection interference imaging system was studied. Image plane intersection interference imaging spectroscopy technology was verified in experiment.
2016, 45(4): 424001.
doi: 10.3788/IRLA201645.0424001
Frequency-domain photoacoustic imaging is a new imaging modality, which uses the output amplitude information periodically modulated by a continuous-wave laser as a light source to stimulate biological tissues and to produce photoacoustic signals processed at frequency-domain and used to image the tissues. Firstly, the principles, developments and research status of photoacoustic imaging and frequency-domain photoacoustic imaging were introduced, and then the specific test methods and basic reconstruction algorithms of the frequency-domain photoacoustic imaging filed were described. In order to make up for time domain photoacoustic imaging with high costs, great harmful, poor portability and so on shortcomings, two imaging modalities were proposed and two complete experimental system structure diagrams were exhibited, showing different features and developing directions of photoacoustic imaging with respect to the traditional domain-photoacoustic imaging. At last, the outlook of the frequency-domain photoacoustic imaging was made to provide some references and guidance for our research and development about photoacoustic imaging.
2016, 45(4): 424002.
doi: 10.3788/IRLA201645.0424002
According to some specific problems of conventional star simulator including the less simulation parameters, low accuracy and big difficulty of star simulation technology, by creatively introducing the LED luminous technology into the design of star simulator, a development scheme of novel star simulator based on the LED luminous technology was proposed. Combining with design results of collimating optical system, the overall mechanical structure of star simulator was designed in detail, to ensure that the designed simulator having characteristics of the largest possible weakening of temperature change, vibration and other external factors in the simulation environment. Control technology of star position accuracy, star brightness, star roundness, emitting uniformity of star light was researched and analyzed. Analysis and test results show that the designed star simulator owing the properties of angular distance precision between stars less than 3, a variety simulation of 5 continuous magnitudes, at the same time to meet multi-parameter simulation requirement about the star roundness, luminous uniformity and luminescence spectra. The proposed design method can provide a feasible technical solution for the development of higher level of star simulator.
2016, 45(4): 424003.
doi: 10.3788/IRLA201645.0424003
The theory that light can transmit information in a unique way has been proved by the experiment and theory of correlated imaging. In this paper, the principles of correlated imaging were discussed in semi-classical interpretations. In the view of pseudo-thermal light field, photoelectric detection and correlated computation, the imaging process was analyzed. Field of view, spatial resolution and contrast of the system were given. On this basis, the traditional linear correlation algorithm was improved to make the ghost image a mean square convergence unbiased estimation of the object transmission function. The corresponding computational ghost imaging experiment measurement indicates that under the same number, especially less than the Nyquist frequency, the PSNR is significantly improved and background noise is effectively suppressed compared with the traditional algorithm.
2016, 45(11): 1124001.
doi: 10.3788/IRLA201645.1124001
The Point Spread Function (PSF) is a typical analytical method of traditional imaging. Using it for reference, the theory of Correlated Imaging(GI) was r-deduced and the PSF of Ghost Image(GI) was derived. Based on this theory, the PSF and GI formula were derived when turbulent was considered in optical paths. Finally, numerical simulation was done and the result indicates that GI process can be described by PSF properly. The variation caused by distance, source size and turbulence intensity can be quantitatively analyzed.
2015, 44(5): 1638-1642.
The design of four spectrum imaging of a single sensor spectro-imaging system was presented. The prism was placed before lens set, departure at different direction of the objective radiation across prism, the separate spectro-image was formed at different place of focal plane. The F number of the spectro-imaging system whose working wavebands are 8.2-8.6 m, 9.4-9.8 m, 10.6-11.2 m and 11.2-12.2 m is 4, the focal length is 55 cm and the aperture diameter is 50 mm. The spot diagram diameter is less than 40 m. Vignetting was introduced to solve the superimposition between different spectrum. The aberration characteristic and the blur circle diameter distribution of the system was analyzed. The analysis results showed that the system had a good image quality and met with spectro-imaging requirements.
2015, 44(5): 1643-1646.
As a novel type Fourier transform imaging spectrometry, large aperture static imaging spectrometry has come forth in recent years, which has many advantages such as high throughput, multi-channeland so on. However, if there are certain registration error on the detector array and interferogram, it will have a greater impact on the restoring spectrum, and even affect the final application of the instrument. To solve this problem, according to the imaging prinple analysis of LASIS, a detector registration error calibration method was given, after verification, this method can well solve the problem of the detector registration error, and the accuracy of recovered spectrum was evidently improved. This study has important guiding significance for the development of large aperture static imaging spectrometer.
2015, 44(5): 1647-1653.
In order to study the effect of temperature on airborne imaging spectrometer optical performance, the characteristics of the instrument under temperature load onboard were analyzed, the mechanism and manifestations of temperature load were described, the thermal performance of the spectrometer was studied. Firstly, the characteristics of the temperature load under airborne was analyzed. Secondly, the least squares method and coordinate transformation method were taken as the theoretical basis for the preparation of the surface error and rigid displacement solver, combined with the finite element method to calculate the deformation and rigid body displacement of the mirror of the optical systems at a temperature load. Finally, a ray tracing was used to solve the mirror line position change due to displacement of the rigid body displacement, study its spectral drift, and calculate the effect of the rigid body displacement on the modulation transfer function(MTF). The results show that within the range 10 ℃, line drift is less than 1/3 of the required accuracy of spectral calibration, no further spectral calibration and correction is needed.
2014, 43(S1): 203-208.
In order to achieve a clear dynamic staring imaging, the imaging model of satellite real-time imaging to track the target was designed, body posture angular velocity relative orbital coordinate system were designed when satellite staring imaging, the coordinate transformation method was used to real-time compute the time of the line transfer process in the gazing, the method of Monte Carlo was used to statistical calculate the influence of imaging under the satellite's attitude point precision and stability in the mode of staring-imaging. Finally, the CMOS prototype and the minitype three-axis air bearing table constructed for attitude control were used to simulate the digital domain CMOS staring imaging.The results show that in the satellite staring imaging process, the integration time in the image plane which caused by satellite attitude change and attitude dynamic tracking is greater than the accuracy of the detector, analysis and simulation results show, in order to meet shift of less than or equal to the detection element size requirements, simulation platform dynamic tracking accuracy better than 0.002()/s, can achieve satellite getting 2 m clear resolution dynamic imaging in 500 km.
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