Stray light has a significant effect on the overall performance of telescopes,particularly for infrared solar telescopes,in which internal thermal radiation causes additional stray light sources.We establish a 3-dimen...Stray light has a significant effect on the overall performance of telescopes,particularly for infrared solar telescopes,in which internal thermal radiation causes additional stray light sources.We establish a 3-dimensional model using stray light theory and the real opto-mechanical structure of the Accurate Infrared Magnetic field measurements of the Sun(AIMS)telescope.We use the stray light ratio(i.e.,the ratio of stray light energy reaching the detector to the light energy used for observations)to evaluate the imaging performance of the telescope.We analyze both thermal and non-thermal sources of stray light to comprehensively study the visible,8-10μm,and Fourier transform infrared systems of the telescope,finding stray light ratios of 9.31×10^(-6)in the visible system,2.83×10^(-4)in the 8-10μm system,and 1.54×10^(-4)in the Fourier transform infrared system.This verifies that the opto-mechanical system design of the telescope can effectively suppress stray light,benefiting both imaging and magnetic field observations.展开更多
Null compensation interferometry is the primary testing method for the manufacture of ultra-high-precision aspheric mirrors.The crosstalk fringes generated by stray light in interferometry can affect accuracy and pote...Null compensation interferometry is the primary testing method for the manufacture of ultra-high-precision aspheric mirrors.The crosstalk fringes generated by stray light in interferometry can affect accuracy and potentially prevent the testing from proceeding normally.Position errors include the decenter error,tilt error,and distance error.During the testing process,position errors will impact the testing accuracy and the crosstalk fringes generated by stray light.To determine the specific impact of position errors,we use the concept of Hindle shell testing of a convex aspheric mirror,and propose the simulation method of crosstalk fringes in null compensation interferometry.We also propose evaluation indices of crosstalk fringes in interferometry and simulate the influence of position errors on the crosstalk fringes.This work aims to help improve the design of compensation interferometry schemes,enhance the feasibility of the design,reduce engineering risks,and improve efficiency.展开更多
An extreme ultraviolet solar corona multispectral imager can allow direct observation of high temperature coronal plasma,which is related to solar flares,coronal mass ejections and other significant coronal activities...An extreme ultraviolet solar corona multispectral imager can allow direct observation of high temperature coronal plasma,which is related to solar flares,coronal mass ejections and other significant coronal activities.This manuscript proposes a novel end-to-end computational design method for an extreme ultraviolet(EUV)solar corona multispectral imager operating at wavelengths near 100 nm,including a stray light suppression design and computational image recovery.To suppress the strong stray light from the solar disk,an outer opto-mechanical structure is designed to protect the imaging component of the system.Considering the low reflectivity(less than 70%)and strong-scattering(roughness)of existing extreme ultraviolet optical elements,the imaging component comprises only a primary mirror and a curved grating.A Lyot aperture is used to further suppress any residual stray light.Finally,a deep learning computational imaging method is used to correct the individual multi-wavelength images from the original recorded multi-slit data.In results and data,this can achieve a far-field angular resolution below 7",and spectral resolution below 0.05 nm.The field of view is±3 R_(☉)along the multi-slit moving direction,where R☉represents the radius of the solar disk.The ratio of the corona's stray light intensity to the solar center's irradiation intensity is less than 10-6 at the circle of 1.3 R_(☉).展开更多
The compound diffractive telescope is a novel space optical system which combines the structure of compound eyes with diffractive optics and so it has a lighter weight, a wider field of view （FOV）, a lower cost as w...The compound diffractive telescope is a novel space optical system which combines the structure of compound eyes with diffractive optics and so it has a lighter weight, a wider field of view （FOV）, a lower cost as well as looser fabrication tolerance. In this paper, the design of a compound diffractive telescope composed of one primary lens and twenty-one eyepieces is introduced. Then the influence of diffraction orders on the performance of the system is analysed. A modified phase function model of diffractive optics is proposed to analyse the modulation transfer function （MTF） curves for 0° FOV, which provides a more accurate prediction of the performance of the system. In addition, an optimized mechanism is also proposed to suppress stray light. The star image and resolution tests show that the system can achieve diffraction limit imaging within ±2° of FOV and 4-4 mm of eccentricity. Finally, a series of pictures of an object are taken from different channels, and the splicing of pictures from adjacent FOVs is demonstrated. In summary, the designed system has been proved to have great potential applications.展开更多
This article describes a novel configuration design for a re-imaging off-axis catadioptric space infrared optical system,and in order to satisfy the signal noise ratio requirements of the system,the stray light of the...This article describes a novel configuration design for a re-imaging off-axis catadioptric space infrared optical system,and in order to satisfy the signal noise ratio requirements of the system,the stray light of the system is necessary to analyze and restrain. The optical system with a focal length of 1 200 mm,an entrance pupil diameter of 600 mm,an F-number of 2,a field of view of 3°× 0. 15°,a working wave band of 8 μm-10 μm,and the image quality of the optical system almost approach to diffraction limits in all field of view.Then the mathematical models of stray light are built,and the suppressive structure is established to eliminate the effect of stray light. Finally,TraceP ro is used to analyze and simulate stray light with and without the suppressive structure,and also get the results of the PST curves. The results indicate that appropriate optical system and suppressive structure can highly reduce the stray light of the space infrared optical system.展开更多
The Advanced Geosynchronous Radiation Imager(AGRI)onboard China’s Fengyun(FY)-4 satellites,which provides observational data across various wavelengths from visible to infrared(IR),holds great potential for diverse a...The Advanced Geosynchronous Radiation Imager(AGRI)onboard China’s Fengyun(FY)-4 satellites,which provides observational data across various wavelengths from visible to infrared(IR),holds great potential for diverse applications.However,the FY-4A AGRI mid-wave IR(MWIR)band(3.75µm)is often contaminated by stray light in the midnight hours during the 1-2 months before and after the vernal or autumnal equinoxes.In this study,a U-Net-based deep learning model was employed to generate an expedient MWIR band from the FY-4A AGRI long-wave IR band.Validation using normal radiance measurements revealed that MWIR brightness temperatures generated by the deep learning model are very close to those observed by the FY-4A AGRI,with mean absolute error of 1.48 K,root mean square error of 2.39 K,and a correlation coefficient of 0.99.When applying the model to periods of stray light contamination,the brightness temperature anomalies found in the FY-4A AGRI MWIR band are effectively eliminated.The findings of this study could support various scientific applications that necessitate use of the MWIR band during midnight hours,such as identification of fog/low stratus cloud.展开更多
A set of system based on personal computer for the bi-directional reflectance distribution function (BRDF) measurement was developed, whose laser wavelengths cover 0.6328, 1.34, 3.39, and 10.6 μm from visible to infr...A set of system based on personal computer for the bi-directional reflectance distribution function (BRDF) measurement was developed, whose laser wavelengths cover 0.6328, 1.34, 3.39, and 10.6 μm from visible to infrared. Stray light in BRDF measurement system was analyzed. It can be reduced and suppressed by the design of the system light path in BRDF measurement system, the choice of the measuring scheme, the processing to the optoelectronic signal, and the radiation control of the optical components and mechanical equipments. So the minimum measurable value of BRDF is less than 10-5/sr.展开更多
This letter shows that the human eye fundus tissue has higher reflectivity at the near-infrared （NIR） wavelength, and that some aberrations exist at the pre-optical system from cornea to vitreous. We design a NIR fu...This letter shows that the human eye fundus tissue has higher reflectivity at the near-infrared （NIR） wavelength, and that some aberrations exist at the pre-optical system from cornea to vitreous. We design a NIR fundus camera with inner focusing, which can be applied to the -10 D to 10 D range of vision and has the advantage of ensuring the stability of image when is focused. Considered as Liou＇s eye aberration model, we correct the integrated aberration to ensure a 100 lp/mm resolution when we complete the assembly and calibration of the fundus camera. Kohler illumination is also applied to obtain uniform fundus illumination. Moreover, we put forward a novel method for stray light elimination based on polarization switch, which inhibits ghost image formation near the focal plane when the illumination beam is reflected by the eyepiece surface. The result shows that this method is effective in ensuring an illumination uniformity of 80%, with the advantage of simple structure and easy assembly.展开更多
This research proposes a simple and practical method to make low-stray-light gratings, where the substrate shifts about a 1 mm distance in the direction parallel or perpendicular to the exposure interference fringes. ...This research proposes a simple and practical method to make low-stray-light gratings, where the substrate shifts about a 1 mm distance in the direction parallel or perpendicular to the exposure interference fringes. When the substrate shifts, a reference grating next to the substrate is used to adjust in real time the phase of the exposure interference fringes relative to the substrate. Shifting eliminates the exposure defects and therefore decreases the stray light of gratings. Several gratings are successfully made by using this method, which have straighter grooves,smoother surfaces, and lower stray light than gratings made in conventional interference lithography.展开更多
Purpose The Einstein Probe(EP)satellite is a science mission of the Chinese Academy of Sciences,which is dedicated to time-domain astronomy and high-energy astrophysics.The X-ray baffle is a crucial component of follo...Purpose The Einstein Probe(EP)satellite is a science mission of the Chinese Academy of Sciences,which is dedicated to time-domain astronomy and high-energy astrophysics.The X-ray baffle is a crucial component of follow-up X-ray telescope(FXT),which is an important payload onboard EP.It was designed to efficiently reduce stray light,especially single reflection on the hyperboloid of Wolter-I Mirrors.Methods In this paper,based on the parameters of FXT's mirror module and the detector,the design parameters of the X-ray baffle are optimized through preliminary design and detailed ray-tracing simulation.Fabrication involved precision laser cutting,roll forming,laser welding and integration processes.The thermal stability and mechanical environment adaptability were validated through thermal cycling and mechanical vibration tests.Finally,the X-ray baffle was mounted onto the mirror module with alignment precisely controlled using optical methods.Results The height of the X-ray baffle ranges from 60 to 120 mm from the outside to the inside;the aperture corresponds to each layer of the mirror module.In order to reduce weight and reduce light occlusion,the thickness of each thin shell is 0.125 mm.The ray-tracing simulation results with X-ray baffle are shown that the stray light is effectively reduced in the effective region of the detector.The Eigen-frequency change of the X-ray baffle after the thermal cycle test and mechanical vibration tests is only 0.52%and 0.77%,respectively.The results proved that X-ray baffle has a high thermo-mechanical reliability.The half power diameter(HPD)of the mirror module remained unchanged on-axis with/without X-ray baffle.Conclusion The introduction of X-ray baffle is expected to be highly significantly reduce stray light.展开更多
It has been more than half a century since the release of the first Shimadzu UV-VIS （UV-visible） spectrophotometer QB-50 in 1952, and during this time more than 160,000 UV-VIS spectrometers have been produced and in...It has been more than half a century since the release of the first Shimadzu UV-VIS （UV-visible） spectrophotometer QB-50 in 1952, and during this time more than 160,000 UV-VIS spectrometers have been produced and installed in a wide variety of different applications. A lot of technical innovations have been implemented to improve the performance and significantly reduce the stray light levels. The latest innovation during development of sophisticated spectrophotometers is based on a new holographic exposure method and optimized etching process which has made it possible to produce both high-efficient and exceptionally low stray light gratings. These LO-RAY-LIGH~ gratings have guaranteed values of stray light at the intermediate position between zero-order and first-order lights. The values are measured by Shimadzu＇s laser stray-light-measuring system. The latest development in the series of UV-VIS spectrophotometers is the UV-2700 which is a true double beam double monochromator system in a compact design for high-precision spectral analysis of a wide range of samples including organic and inorganic compounds, biological samples, optical materials and photovoltaics. The high performance optical system is designed with ＂LO-RAY-LIGH＂ diffraction gratings, featuring highest efficiency and exceptionally low stray light. The spectrophotometer operates in the wavelength range from 185 nm to 900 nm and allows highly sophisticated applications such as direct measurement of high density samples up to 8 absorbance units without dilution.展开更多
The spectral radiation characteristic of a non-luminous flame is analyzed. The apparatus and the calibration procedure based on infrared emission spectrometry for measurements of the flame are introduced. The influenc...The spectral radiation characteristic of a non-luminous flame is analyzed. The apparatus and the calibration procedure based on infrared emission spectrometry for measurements of the flame are introduced. The influence of background radiation and stray light on the measurement results could be reduced and suppressed by the design of thermolator and digital lock-in technique. A blackbody cavity was used as reference emission source to calibrate the system that completed absolute measurement. The spectral mea- surement range is 1-20μm. The least measuring distance and the lowest power detected at the entrance pupil are 550 mm and 10^-9 W/cm^2, respectively. The experimental results show that the measure error is less than 10%.展开更多
Based on the analysis for the main elements of the total modulation transfer function （MTF） of imager on geostationary platform, the precise evaluation for its low spatial frequency spectrum has been achieved. Meanw...Based on the analysis for the main elements of the total modulation transfer function （MTF） of imager on geostationary platform, the precise evaluation for its low spatial frequency spectrum has been achieved. Meanwhile, it is pointed out that the main cause of imagery spatial resolution lower than the designed value is the ＂slight defocus＂ of imager focal plane array （FPA）. The validation method for visible imagery spatial resolution is proposed based on the analysis of defocused optical system model and edge-spread-function （ESF）, the relative error is less than 7% after alleviating stray light effects. This method has been applied in the in-orbit ground testing of FY-2C geostationary meteorological satellite successfully.展开更多
Near-field holography（NFH）, with its virtues of precise critical dimensions and high throughput, has a great potential for the realization of soft x-ray diffraction gratings. We show that NFH with reflections reduce...Near-field holography（NFH）, with its virtues of precise critical dimensions and high throughput, has a great potential for the realization of soft x-ray diffraction gratings. We show that NFH with reflections reduced by the integration of antireflective coatings（ARCs） simplifies the NFH process relative to that of setups using refractive index liquids. Based on the proposed NFH with ARCs, gold-coated laminar gratings were fabricated using NFH and subsequent ion beam etching. The efficiency angular spectrum shows that the stray light of the gratings is reduced one level of magnitude by the suppression of interface reflections during NFH.展开更多
基金supported by National Natural Science Foundation of China(12473086 and 11427901)National Key Research and Development Program of China(2021YFA1600500)Youth Innovation Promotion Association of the Chinese Academy of Sciences(2022057).
文摘Stray light has a significant effect on the overall performance of telescopes,particularly for infrared solar telescopes,in which internal thermal radiation causes additional stray light sources.We establish a 3-dimensional model using stray light theory and the real opto-mechanical structure of the Accurate Infrared Magnetic field measurements of the Sun(AIMS)telescope.We use the stray light ratio(i.e.,the ratio of stray light energy reaching the detector to the light energy used for observations)to evaluate the imaging performance of the telescope.We analyze both thermal and non-thermal sources of stray light to comprehensively study the visible,8-10μm,and Fourier transform infrared systems of the telescope,finding stray light ratios of 9.31×10^(-6)in the visible system,2.83×10^(-4)in the 8-10μm system,and 1.54×10^(-4)in the Fourier transform infrared system.This verifies that the opto-mechanical system design of the telescope can effectively suppress stray light,benefiting both imaging and magnetic field observations.
基金the National Key Research and Development Program of China(2022YFB3403404)the Youth Innovation Promotion Association,CAS(2022213)the National Natural Science Foundation of China(62127901 and 62305334).
文摘Null compensation interferometry is the primary testing method for the manufacture of ultra-high-precision aspheric mirrors.The crosstalk fringes generated by stray light in interferometry can affect accuracy and potentially prevent the testing from proceeding normally.Position errors include the decenter error,tilt error,and distance error.During the testing process,position errors will impact the testing accuracy and the crosstalk fringes generated by stray light.To determine the specific impact of position errors,we use the concept of Hindle shell testing of a convex aspheric mirror,and propose the simulation method of crosstalk fringes in null compensation interferometry.We also propose evaluation indices of crosstalk fringes in interferometry and simulate the influence of position errors on the crosstalk fringes.This work aims to help improve the design of compensation interferometry schemes,enhance the feasibility of the design,reduce engineering risks,and improve efficiency.
基金This study is partially supported by the National Natural Science Foundation of China(NSFC)(62005120,62125504).
文摘An extreme ultraviolet solar corona multispectral imager can allow direct observation of high temperature coronal plasma,which is related to solar flares,coronal mass ejections and other significant coronal activities.This manuscript proposes a novel end-to-end computational design method for an extreme ultraviolet(EUV)solar corona multispectral imager operating at wavelengths near 100 nm,including a stray light suppression design and computational image recovery.To suppress the strong stray light from the solar disk,an outer opto-mechanical structure is designed to protect the imaging component of the system.Considering the low reflectivity(less than 70%)and strong-scattering(roughness)of existing extreme ultraviolet optical elements,the imaging component comprises only a primary mirror and a curved grating.A Lyot aperture is used to further suppress any residual stray light.Finally,a deep learning computational imaging method is used to correct the individual multi-wavelength images from the original recorded multi-slit data.In results and data,this can achieve a far-field angular resolution below 7",and spectral resolution below 0.05 nm.The field of view is±3 R_(☉)along the multi-slit moving direction,where R☉represents the radius of the solar disk.The ratio of the corona's stray light intensity to the solar center's irradiation intensity is less than 10-6 at the circle of 1.3 R_(☉).
基金Project supported by the National High Technology Research and Development Program of China (Grant No. 2006AA12Z127)the National Natural Science Foundation of China (Grant No. 10704072)the Innovation Program of Chinese Academy of Sciences
文摘The compound diffractive telescope is a novel space optical system which combines the structure of compound eyes with diffractive optics and so it has a lighter weight, a wider field of view （FOV）, a lower cost as well as looser fabrication tolerance. In this paper, the design of a compound diffractive telescope composed of one primary lens and twenty-one eyepieces is introduced. Then the influence of diffraction orders on the performance of the system is analysed. A modified phase function model of diffractive optics is proposed to analyse the modulation transfer function （MTF） curves for 0° FOV, which provides a more accurate prediction of the performance of the system. In addition, an optimized mechanism is also proposed to suppress stray light. The star image and resolution tests show that the system can achieve diffraction limit imaging within ±2° of FOV and 4-4 mm of eccentricity. Finally, a series of pictures of an object are taken from different channels, and the splicing of pictures from adjacent FOVs is demonstrated. In summary, the designed system has been proved to have great potential applications.
基金Sponsored by the National High Technology Research and Development Program of China(Grant No.863-2-5-1-13B)
文摘This article describes a novel configuration design for a re-imaging off-axis catadioptric space infrared optical system,and in order to satisfy the signal noise ratio requirements of the system,the stray light of the system is necessary to analyze and restrain. The optical system with a focal length of 1 200 mm,an entrance pupil diameter of 600 mm,an F-number of 2,a field of view of 3°× 0. 15°,a working wave band of 8 μm-10 μm,and the image quality of the optical system almost approach to diffraction limits in all field of view.Then the mathematical models of stray light are built,and the suppressive structure is established to eliminate the effect of stray light. Finally,TraceP ro is used to analyze and simulate stray light with and without the suppressive structure,and also get the results of the PST curves. The results indicate that appropriate optical system and suppressive structure can highly reduce the stray light of the space infrared optical system.
基金Supported by the National Natural Science Foundation of China(42305177 and 42175006)Beijige Foundation(BJG202210)Open Research Program of the State Key Laboratory of Severe Weather(2023LASW-B16).
文摘The Advanced Geosynchronous Radiation Imager(AGRI)onboard China’s Fengyun(FY)-4 satellites,which provides observational data across various wavelengths from visible to infrared(IR),holds great potential for diverse applications.However,the FY-4A AGRI mid-wave IR(MWIR)band(3.75µm)is often contaminated by stray light in the midnight hours during the 1-2 months before and after the vernal or autumnal equinoxes.In this study,a U-Net-based deep learning model was employed to generate an expedient MWIR band from the FY-4A AGRI long-wave IR band.Validation using normal radiance measurements revealed that MWIR brightness temperatures generated by the deep learning model are very close to those observed by the FY-4A AGRI,with mean absolute error of 1.48 K,root mean square error of 2.39 K,and a correlation coefficient of 0.99.When applying the model to periods of stray light contamination,the brightness temperature anomalies found in the FY-4A AGRI MWIR band are effectively eliminated.The findings of this study could support various scientific applications that necessitate use of the MWIR band during midnight hours,such as identification of fog/low stratus cloud.
基金This work was supported by the Scientific Research Foundation of Harbin Institute of Technology project (HIT. MD. 2001.17).
文摘A set of system based on personal computer for the bi-directional reflectance distribution function (BRDF) measurement was developed, whose laser wavelengths cover 0.6328, 1.34, 3.39, and 10.6 μm from visible to infrared. Stray light in BRDF measurement system was analyzed. It can be reduced and suppressed by the design of the system light path in BRDF measurement system, the choice of the measuring scheme, the processing to the optoelectronic signal, and the radiation control of the optical components and mechanical equipments. So the minimum measurable value of BRDF is less than 10-5/sr.
基金supported by the National Natural Science Foundation of China(Nos.60977008and60678048)the National Ministry Education Fund for Doctoral of China(No.20103219110014)the Chinese Academy of Sciences Key Laboratory Fund(No.2008DP173445)
文摘This letter shows that the human eye fundus tissue has higher reflectivity at the near-infrared （NIR） wavelength, and that some aberrations exist at the pre-optical system from cornea to vitreous. We design a NIR fundus camera with inner focusing, which can be applied to the -10 D to 10 D range of vision and has the advantage of ensuring the stability of image when is focused. Considered as Liou＇s eye aberration model, we correct the integrated aberration to ensure a 100 lp/mm resolution when we complete the assembly and calibration of the fundus camera. Kohler illumination is also applied to obtain uniform fundus illumination. Moreover, we put forward a novel method for stray light elimination based on polarization switch, which inhibits ghost image formation near the focal plane when the illumination beam is reflected by the eyepiece surface. The result shows that this method is effective in ensuring an illumination uniformity of 80%, with the advantage of simple structure and easy assembly.
基金supported by the National Natural Science Foundation of China under Grant No.51427805
文摘This research proposes a simple and practical method to make low-stray-light gratings, where the substrate shifts about a 1 mm distance in the direction parallel or perpendicular to the exposure interference fringes. When the substrate shifts, a reference grating next to the substrate is used to adjust in real time the phase of the exposure interference fringes relative to the substrate. Shifting eliminates the exposure defects and therefore decreases the stray light of gratings. Several gratings are successfully made by using this method, which have straighter grooves,smoother surfaces, and lower stray light than gratings made in conventional interference lithography.
基金supported by the Natural Science Basic Research Program of Shaanxi Province(2024JC-YBMS-532)the Natural Science Basic Research Program of Shaanxi Province(2023-JC-ZD-40)+1 种基金the Natural Science Basic Research Program of Shaanxi Province(2024JC-YBQN-0003)the Natural Science Basic Research Program of Shaanxi Province(2024JC-YBQN-0686).
文摘Purpose The Einstein Probe(EP)satellite is a science mission of the Chinese Academy of Sciences,which is dedicated to time-domain astronomy and high-energy astrophysics.The X-ray baffle is a crucial component of follow-up X-ray telescope(FXT),which is an important payload onboard EP.It was designed to efficiently reduce stray light,especially single reflection on the hyperboloid of Wolter-I Mirrors.Methods In this paper,based on the parameters of FXT's mirror module and the detector,the design parameters of the X-ray baffle are optimized through preliminary design and detailed ray-tracing simulation.Fabrication involved precision laser cutting,roll forming,laser welding and integration processes.The thermal stability and mechanical environment adaptability were validated through thermal cycling and mechanical vibration tests.Finally,the X-ray baffle was mounted onto the mirror module with alignment precisely controlled using optical methods.Results The height of the X-ray baffle ranges from 60 to 120 mm from the outside to the inside;the aperture corresponds to each layer of the mirror module.In order to reduce weight and reduce light occlusion,the thickness of each thin shell is 0.125 mm.The ray-tracing simulation results with X-ray baffle are shown that the stray light is effectively reduced in the effective region of the detector.The Eigen-frequency change of the X-ray baffle after the thermal cycle test and mechanical vibration tests is only 0.52%and 0.77%,respectively.The results proved that X-ray baffle has a high thermo-mechanical reliability.The half power diameter(HPD)of the mirror module remained unchanged on-axis with/without X-ray baffle.Conclusion The introduction of X-ray baffle is expected to be highly significantly reduce stray light.
文摘It has been more than half a century since the release of the first Shimadzu UV-VIS （UV-visible） spectrophotometer QB-50 in 1952, and during this time more than 160,000 UV-VIS spectrometers have been produced and installed in a wide variety of different applications. A lot of technical innovations have been implemented to improve the performance and significantly reduce the stray light levels. The latest innovation during development of sophisticated spectrophotometers is based on a new holographic exposure method and optimized etching process which has made it possible to produce both high-efficient and exceptionally low stray light gratings. These LO-RAY-LIGH~ gratings have guaranteed values of stray light at the intermediate position between zero-order and first-order lights. The values are measured by Shimadzu＇s laser stray-light-measuring system. The latest development in the series of UV-VIS spectrophotometers is the UV-2700 which is a true double beam double monochromator system in a compact design for high-precision spectral analysis of a wide range of samples including organic and inorganic compounds, biological samples, optical materials and photovoltaics. The high performance optical system is designed with ＂LO-RAY-LIGH＂ diffraction gratings, featuring highest efficiency and exceptionally low stray light. The spectrophotometer operates in the wavelength range from 185 nm to 900 nm and allows highly sophisticated applications such as direct measurement of high density samples up to 8 absorbance units without dilution.
文摘The spectral radiation characteristic of a non-luminous flame is analyzed. The apparatus and the calibration procedure based on infrared emission spectrometry for measurements of the flame are introduced. The influence of background radiation and stray light on the measurement results could be reduced and suppressed by the design of thermolator and digital lock-in technique. A blackbody cavity was used as reference emission source to calibrate the system that completed absolute measurement. The spectral mea- surement range is 1-20μm. The least measuring distance and the lowest power detected at the entrance pupil are 550 mm and 10^-9 W/cm^2, respectively. The experimental results show that the measure error is less than 10%.
基金This work was supported by the National Natural Science Foundation of China under Grant No. 40401040.
文摘Based on the analysis for the main elements of the total modulation transfer function （MTF） of imager on geostationary platform, the precise evaluation for its low spatial frequency spectrum has been achieved. Meanwhile, it is pointed out that the main cause of imagery spatial resolution lower than the designed value is the ＂slight defocus＂ of imager focal plane array （FPA）. The validation method for visible imagery spatial resolution is proposed based on the analysis of defocused optical system model and edge-spread-function （ESF）, the relative error is less than 7% after alleviating stray light effects. This method has been applied in the in-orbit ground testing of FY-2C geostationary meteorological satellite successfully.
基金supported by the Sino-German Center for Research Promotion (No.GZ 983)the German Science Foundation DFG (No.IRTG 2101)+1 种基金the Joint Fund of the National Natural Science Foundation of Chinathe China Academy of Engineering Physics (No.U1230104)
文摘Near-field holography（NFH）, with its virtues of precise critical dimensions and high throughput, has a great potential for the realization of soft x-ray diffraction gratings. We show that NFH with reflections reduced by the integration of antireflective coatings（ARCs） simplifies the NFH process relative to that of setups using refractive index liquids. Based on the proposed NFH with ARCs, gold-coated laminar gratings were fabricated using NFH and subsequent ion beam etching. The efficiency angular spectrum shows that the stray light of the gratings is reduced one level of magnitude by the suppression of interface reflections during NFH.
