Three-dimensional(3D)refractive index(RI)distribution is important to reveal the object’s inner structure.We implemented terahertz(THz)diffraction tomography with a continuous-wave single-frequency THz source for mea...Three-dimensional(3D)refractive index(RI)distribution is important to reveal the object’s inner structure.We implemented terahertz(THz)diffraction tomography with a continuous-wave single-frequency THz source for measuring 3D RI maps.The off-axis holographic interference configuration was employed to obtain the quantitative scattered field of the object under each rotation angle.The 3D reconstruction algorithm adopted the filtered backpropagation method,which can theoretically calculate the exact scattering potential from the measured scattered field.Based on the Rytov approximation,the 3D RI distribution of polystyrene foam spheres was achieved with high fidelity,which verified the feasibility of the proposed method.展开更多
The far-field imaging properties of a high index microsphere lens spatially separated from the object are experimentally studied. Our experimental results show that, for a Blu-ray disk whose spacing is 300 nm, the hig...The far-field imaging properties of a high index microsphere lens spatially separated from the object are experimentally studied. Our experimental results show that, for a Blu-ray disk whose spacing is 300 nm, the high index microsphere lens also can discern the patterns of the object sample when the distance between the lens and the object is up to 5.4 μm. When the distance is increased from 0 to 5.4 μm, for the microsphere lens with a diameter of 24 μm, the lateral magnification increases from 3.5× to 5.5×, while the field of view decreases from 5.1 to 3.0 μm. By varying the distance between the lens and the object, the optical image can be optimized. We also indicate that the far-field imaging capability of a high index microsphere lens is dependent on the electromagnetic field intensityprofile of the photonic nanojet under different positions of the microsphere lens.展开更多
The surfaces and refractive index of crystalline lens play an important role in the optical performance of human eye. On the basis of two eye models, which are widely applied at present, the effect of lens surfaces an...The surfaces and refractive index of crystalline lens play an important role in the optical performance of human eye. On the basis of two eye models, which are widely applied at present, the effect of lens surfaces and its refractive index distribution on optical imaging is analyzed with the optical design software ZEMAX （Zemax Development Co., San Diego, USA）. The result shows that good image quality can be provided by the aspheric lens surfaces or （and） the gradient-index （GRIN） distribution. It has great potential in the design of intraocular lens （IOL）. The eye models with an intraocular implantation are presented.展开更多
A kind of image distortion in Optical Coherence Tomography (OCT) resulted from average refractive index changes between structures of bio tissue is discussed for the first time.Analysis is given on following situation...A kind of image distortion in Optical Coherence Tomography (OCT) resulted from average refractive index changes between structures of bio tissue is discussed for the first time.Analysis is given on following situations:1) Exact refraction index changes between microstructures;2)The gradient of average refractive index change between different tissue layers is parallel to the probe beam;3) The gradient of average refractive index change is vertical to the probe beam.The results show that the image distortion of situation 1) is usually negligible;in situation 2) there is a spread or shrink effect without relative location error; however,in situation 3) there is a significant image error inducing relative location displacement between different structures.Preliminary design to eliminate the distortion is presented,the method of which mainly based on the image classification and pixel array re arrangement.展开更多
A new method of image processing of corona virus based on two and multiple beam interference is suggested. The method is based on measuring the fringe shift with respect to the background interference pattern. The int...A new method of image processing of corona virus based on two and multiple beam interference is suggested. The method is based on measuring the fringe shift with respect to the background interference pattern. The interested application of the corona virus image in confocal microscopy is getting depth information since it has the property of optical sectioning. An accurate measurement of the fringe shift is obtained using multiple beam interference since contrast is higher than that for two beam interference. The refractive index of the corona virus image is deduced from the fringe shift. A MATLAB code is used for the processing of all images.展开更多
High frame rate and highly sensitive imaging of refractive index changes on a surface is very promising for studying the dynamics of dissolution,mixing and biological processes without the need for labeling.Here,a hig...High frame rate and highly sensitive imaging of refractive index changes on a surface is very promising for studying the dynamics of dissolution,mixing and biological processes without the need for labeling.Here,a highly sensitive distributed feedback(DFB)dye laser sensor for high frame rate imaging refractometry without moving parts is presented.DFB dye lasers are low-cost and highly sensitive refractive index sensors.The unique multi-wavelength DFB laser structure presented here comprises several areas with different grating periods.Imagingin two dimensions of space is enabled by analyzinglaser light from all areasin parallelwith an imaging spectrometer.With this multi-resonance imaging refractometry method,the spatial position in one direction is identified from the horizontal,i.e.,spectral position of the multiple laser lines which is obtained from the spectrometer charged coupled device(CCD)array.The orthogonal spatial position is obtained from the vertical spatial position on the spectrometer CCD array as in established spatially resolved spectroscopy.Here,the imaging technique is demonstrated by monitoring the motion of small sucrose molecules upon dissolution of solid sucrose in water.The omission of moving parts improves the robustness of the imaging system and allows a very high frame rate of up to 12 Hz.展开更多
基金supported by the National Natural Science Foundation of China(Nos.62075001 and 61675010)the Science Foundation of Education Commission of Beijing(No.KZ202010005008)the Beijing Nova Program(No.XX2018072)。
文摘Three-dimensional(3D)refractive index(RI)distribution is important to reveal the object’s inner structure.We implemented terahertz(THz)diffraction tomography with a continuous-wave single-frequency THz source for measuring 3D RI maps.The off-axis holographic interference configuration was employed to obtain the quantitative scattered field of the object under each rotation angle.The 3D reconstruction algorithm adopted the filtered backpropagation method,which can theoretically calculate the exact scattering potential from the measured scattered field.Based on the Rytov approximation,the 3D RI distribution of polystyrene foam spheres was achieved with high fidelity,which verified the feasibility of the proposed method.
基金financial support for this research from the Doctoral Fund of Ministry of Education of China (No. 20133207110007)the National Natural Science Foundation of China (No. 61475073)
文摘The far-field imaging properties of a high index microsphere lens spatially separated from the object are experimentally studied. Our experimental results show that, for a Blu-ray disk whose spacing is 300 nm, the high index microsphere lens also can discern the patterns of the object sample when the distance between the lens and the object is up to 5.4 μm. When the distance is increased from 0 to 5.4 μm, for the microsphere lens with a diameter of 24 μm, the lateral magnification increases from 3.5× to 5.5×, while the field of view decreases from 5.1 to 3.0 μm. By varying the distance between the lens and the object, the optical image can be optimized. We also indicate that the far-field imaging capability of a high index microsphere lens is dependent on the electromagnetic field intensityprofile of the photonic nanojet under different positions of the microsphere lens.
基金the National Na-ture Science Foundation of China (No.60678048)the Nature Science Foundations of Jiangsu Province (No.BK2007207 and BS2007061).
文摘The surfaces and refractive index of crystalline lens play an important role in the optical performance of human eye. On the basis of two eye models, which are widely applied at present, the effect of lens surfaces and its refractive index distribution on optical imaging is analyzed with the optical design software ZEMAX （Zemax Development Co., San Diego, USA）. The result shows that good image quality can be provided by the aspheric lens surfaces or （and） the gradient-index （GRIN） distribution. It has great potential in the design of intraocular lens （IOL）. The eye models with an intraocular implantation are presented.
文摘A kind of image distortion in Optical Coherence Tomography (OCT) resulted from average refractive index changes between structures of bio tissue is discussed for the first time.Analysis is given on following situations:1) Exact refraction index changes between microstructures;2)The gradient of average refractive index change between different tissue layers is parallel to the probe beam;3) The gradient of average refractive index change is vertical to the probe beam.The results show that the image distortion of situation 1) is usually negligible;in situation 2) there is a spread or shrink effect without relative location error; however,in situation 3) there is a significant image error inducing relative location displacement between different structures.Preliminary design to eliminate the distortion is presented,the method of which mainly based on the image classification and pixel array re arrangement.
文摘A new method of image processing of corona virus based on two and multiple beam interference is suggested. The method is based on measuring the fringe shift with respect to the background interference pattern. The interested application of the corona virus image in confocal microscopy is getting depth information since it has the property of optical sectioning. An accurate measurement of the fringe shift is obtained using multiple beam interference since contrast is higher than that for two beam interference. The refractive index of the corona virus image is deduced from the fringe shift. A MATLAB code is used for the processing of all images.
基金The authors thank JS Clausen for assistance with electron beam lithography and CLC Smith,KT Sørensen and E Højlund-Nielsen for fruitful discussionsCV acknowledges support from the Danish Research Council for Technology and Production Sciences(Grant No.12-126676).
文摘High frame rate and highly sensitive imaging of refractive index changes on a surface is very promising for studying the dynamics of dissolution,mixing and biological processes without the need for labeling.Here,a highly sensitive distributed feedback(DFB)dye laser sensor for high frame rate imaging refractometry without moving parts is presented.DFB dye lasers are low-cost and highly sensitive refractive index sensors.The unique multi-wavelength DFB laser structure presented here comprises several areas with different grating periods.Imagingin two dimensions of space is enabled by analyzinglaser light from all areasin parallelwith an imaging spectrometer.With this multi-resonance imaging refractometry method,the spatial position in one direction is identified from the horizontal,i.e.,spectral position of the multiple laser lines which is obtained from the spectrometer charged coupled device(CCD)array.The orthogonal spatial position is obtained from the vertical spatial position on the spectrometer CCD array as in established spatially resolved spectroscopy.Here,the imaging technique is demonstrated by monitoring the motion of small sucrose molecules upon dissolution of solid sucrose in water.The omission of moving parts improves the robustness of the imaging system and allows a very high frame rate of up to 12 Hz.
