A laser transmitter and receiver are respectively arranged on the low-orbit space station and its companion satellite. Both the 935-nm short-wave infrared band vapor detection laser beam pulse pair and 765-nm near-infrared band laser beam pulse pair (located in the oxygen absorption A-band) are transmitted and received simultaneously. One detection wavelength of the 935-nm band pulse pair strongly absorbs water vapor and other reference wavelength exhibites relatively weak absorption of water vapor; one wavelength of the 765-nm band is strongly absorbed by oxygen and other wavelength is weakly absorbed by oxygen. An Abel transformation relation exists between the two-wavelength differential optical depth of the entire optical connection and differential extinction coefficient at the tangent point of the connection. Based on Abel integral transformation, the numerical calculation is performed using the ideal gas law and the atmospheric quasi-static equation, taken the atmospheric model as the initial condition. The 765-nm wavelength pair is used to invert the atmospheric pressure and temperature, whereas 935-nm wavelength pair is used to invert the atmospheric water vapor density. Simulation results and error distribution of the water vapor profile distribution are obtained. Results show that laser occultation has the potential to detect the level of water vapor in the troposphere-stratosphere (5--14 km).

A 4-dimethylamino-N''-meth-yl-4''-stilbazolium tosylate (DAST) crystal grown by spontaneous nucleation method can realize a tunable broadband THz radiation source. Effects of mass concentration of saturated growth solution on the crystal growth morphology and optical quality are investigated, and the vibration and rotation characteristics of the chromophore are analyzed by the Raman spectrum of the crystal. Using the high-energy and tunable dual-wavelength laser within the wavelength range of 1.3--1.5 μm as a pump source, the broadband THz radiation output in the range of 0.1--20.0 THz is achieved by the 0-phase matching external-cavity different frequency and galvano-optical fast scanning technology. The maximum output energy of each pulse is 3.59 μJ at 18.9 THz, and the energy conversion efficiency is 2.39×10 -4. Based on the broadband THz output spectrum, it is found that the absorption of THz wave by the DAST crystal is mainly caused by lattice vibration.

The change in environmental temperature can reduce the diffraction efficiency of diffractive optical elements (DOEs) and thus affect the imaging quality of a hybrid optical system. Based on the expression of diffraction efficiency at oblique incidence, the temperature change is considered in the design of the double-layer diffractive optical elements (DLDOEs). The mathematical model of microstructure height error and diffraction efficiency/polychromatic integral diffraction efficiency (PIDE) of the DLDOEs within a certain temperature range and at certain incident angles is developed. The DLDOE that works in a visible waveband is taken as an example. The result shows that when a range of environmental temperature is determined, the optimal relative microstructure height error corresponding to the maximum PIDE decreases with the increase of the incident angle range. For the DLDOEs working within the incident angle range of 0°--15° and the environmental temperature range of 40--80 ℃, the maximum PIDE is 96.81%, and the corresponding optimal relative microstructure height error is 4.42%. Accordingly, the proposed model can further improve the design theory of the manufacturing error of the DLDOEs.

Path loss is an important parameter to evaluate the transmission performance of the system. Based on the non-line-of-sight non-coplanar ultraviolet single-scatter transmission model, the traversing tiny unit method (TTUM) is used to simulate the single-scatter path loss of wireless ultraviolet communication in mobile scenes, and the influence of the geometric parameters of the transceiver and the relative position change of the transceiver node on the path loss of the system is analyzed. The results show that path loss increases with the increase of the moving distance of the receiver in the other directions except 180°; with the increase of transceiver elevation angle, path loss increases, and the effect of transmitter elevation angle on path loss is more significant; when the field of view angle is large, the change of beam divergence angle has little effect on path loss, and change of field of view angle has a more obvious effect on path loss in non-coplanar case and large moving distance, while it has little effect in other cases.

In the quantum-classical signal simultaneous transmission scheme sharing a same few-mode fiber based on mode division multiplexing, the mode coupling effect in the optical fiber will lead to crosstalk between channels, resulting in bit error. In this paper, a segmented link model of few-mode fiber is constructed, and the magnitude of mode coupling strength due to fiber splicing error is studied, based on which the system quantum bit error rate (QBER) formula is deduced in the presence of mode coupling. By comparing the coupling strength of each mode, the optimal transmission mode of quantum signal in the scheme is determined. The effects of mismatch distance, torsion angle, and fiber length on the QBER are discussed. The results show that the three factors that affect the coupling strength of link mode are positively correlated with the QBER, and the quantum-classical signal simultaneous transmission system with small fiber splicing error in short distance can effectively reduce the QBER.

To address the problems of complex and rich details of face features and heavy work and high cost of reconstructing high-precision three-dimensional (3D) face models, a high-precision 3D face reconstruction algorithm based on the gradient light image is proposed. Six different illumination modes are established using a spherical light device, and specular and diffuse reflection lights are separated using the polarization characteristic. Using a unidirectional gradient light image, specular and diffuse normal maps are obtained by calculation based on relationship between the reflection and normal directions by employing the bidirectional reflectance distribution function (BRDF). The obtained maps are merged and mapped to the low-precision mode to reconstruct a high-precision 3D face model. The experimental results show that the proposed method has low computational complexity and high reconstruction accuracy. Based on the obtained results, it is best to use the high-pass filtering with a window size of 7×7 enhanced specular and diffuse reflection normal maps to achieve the best reconstruction at 2∶1 map ratio fusion. The proposed model can be refined to microscale.

The analysis of the morphological characteristics of retinal vessels is helpful in diagnosing retinal diseases. To segment retinal vessels more accurately, this paper proposes a new method based on a two-stream network. First, the whole vessel and small vessels are segmented using a convolutional neural network with an encoder-decoder structure. Subsequently, the two prediction maps are fused after the artifacts and noises are removed from the fusion image. The final vascular segmentation is then obtained. Because of the separate segmentation of small vessels, the proposed method can more effectively segment small vessel pixels that make it difficult to recognize the edges and low-contrast areas of retinal vessels. Experimental results show that the sensitivity of the proposed method on DRIVE, STARE, and CHASE_DB1 datasets is 0.8062, 0.8308, and 0.8135, respectively. The performance of the proposed method is better than that of other methods.

Based on the multi-objective optimization method, an optimal filter with good values for each evaluation parameter is obtained. This is achieved according to the cumulative scoring method of optimal ordering for several parameters often used to evaluate the performance of multi-spectral cameras such as peak signal to noise ratio (PNSR), goodness of fit coefficient (GFC), CIE color difference index(CIEDE2000) and mean square error (MSE) and their corresponding maximum or minimum values. Compared with the previous study, the number of filters to be selected increases from 45 to 1035; however, the number of reflectivity samples of the imaging scene increases from 24 to 1269. The results show that the performance of the optimal filter is better when the number of filters and the reflectivity vector space increase. At the same time, the values of the three parameters of the spectral transmittance vector matrix of the optimal filter, namely the condition number (Cond), the peak uniformity index (UF), and the adjacent filter overlap index (OLP), are also more stable. The experimental results can provide a reference for the quantitative selection of wideband multispectral filters via the vector matrix of the filter.

Photothermal optical coherence tomography (PT-OCT) imaging technology is applied to the three-dimensional imaging of tumor tissues. An algorithm, which uses the cross-correlation to extract the signal and calculates average amplitude for solving optical path difference imaging, is proposed to suppress noise and enhance image contrast. The agar sample and the mouse ear model are imaged successively in the validation experiment. Compared with the ordinary OCT and the PT-OCT based on the phase difference algorithm, the proposed method can be used for the mouse ear imaging with more details of capillaries, and the enhancement of the imaging effect of tomographic image can be obtained. In the experiment of imaging tumor model, the three-dimensional (3D) PT-OCT images are acquired from the excised tissues which are observed from different angles and different cut surfaces by the proposed method and the corresponding imaging range is 4 mm×4 mm×3 mm. The distribution of capillaries can be clearly identified. PT-OCT has the advantages of convenient, rapid, non-invasive, high-resolution, and 3D imaging, making it more applicable in clinical diagnosis and treatment of tumors.

This study analyze two multiplicative errors of parallel object-side differential axial measurements method under the surface reflectance change and illumination non-uniformity condition, and an error correction model is proposed. The mathematical expression of the image gray matrix which can characterize multiplicative disturbance interference is constructed, and the multiplicative disturbance interference errors can be eliminated via logarithmic difference, which corrects the errors. The verification of the error correction model is then achieved by analyzing two comparative experiments. In the experiments, the morphometry of the step sample with 4.739 μm height and 50 μm period is measured. The relative error of the measurement is reduced from 2.91% before correction to 0.78% after correction. Under low-magnification objective lens and illumination inhomogeneity measurement condition, a fast three-dimensional morphology experiment is conducted on coins with uneven surface reflectance. The relative deviation of the measurement result is 1.62% compared with those obtained by optical surface profiler. Both the experimental analyses demonstrate that the proposed method can successfully correct the effects of multiplicative errors and improve the adaptability. The proposed method can provide microtopography detection for on-line detection of intelligent manufacturing with high applicability, efficiency, and precision.

Based on the Ronchi-Talbot effect and moire fringe technique, the focal length measurement method using divergent light and unequal-period grating is used for the measurement of the focal length of lens with a small aperture and long focal length. The long focal length of a plano-concave lens as a lens to be measured with a processing error in the curvature radius is measured. When the true curvature radius of the lens is unknown, first, the influence of the curvature radius error (of the lens to be measured) on the focal length detection accuracy is analyzed, and the position of the lens in the whole detection system is determined. Then, the focal length of the lens is measured, and multiple groups of measured focal length values are calculated separately. By comparison, it can be found that when the curvature radius remains unknown, the repeatability and stability of the focal length measurement are consistent. The measured focal lengths are in the range of 33200--33270 mm. The repeatability precision is greater than 0.055%, and measurement accuracy is better than one-fifth of the focal depth. These results prove that the proposed method is reliable and efficient in the focal length measurement of small-aperture lenses with long focal length.

A multi-camera three-dimensional (3D) measurement system using an image stitching method based on flexible calibration target positioning is proposed. In order to expand the measuring range of the 3D shape measurement system, a laser projector is used to project large fringe images, followed with distributed multiple cameras to grab images of each field of view (FOV). The first step of calibration process is to establish the mapping relationship from the image coordinates and absolute phase to the world coordinates by using the reference camera with a small planar calibration target. Then, with the FOV of adjacent cameras partially overlapping, the flexible calibration target positioning is applied to calibrate mapping relationships of the image coordinates from adjacent cameras. After that, the image coordinates of all the other cameras are converted to the image coordinates of the reference camera by the new image stitching method. Finally, the reference camera coordinates are transformed to the world coordinates. The experimental results show that the accuracy of this method is slightly lower than the local measuring method with a single camera. However, the accuracy loss is not so severe, meeting the requirement for industrial on-line measurement. This method does not require expensive auxiliary measuring instruments or manufacturing large calibration targets with high precision, thus offering a low-cost and easy alternative for multi-camera 3D shape measurement systems.

Based on the transmission characteristics of the surface plasmonic polaritons in sub-wavelength structures, a metal-insulator-metal (MIM) waveguide coupled dual T-shaped cavity with metallic baffle structure is proposed . Under the action of near-field coupling, the narrow discrete state formed by a single T-shaped cavity and the wide continuous state formed by a single baffle form the asymmetric double Fano formant through complex interference cancellation. Based on the coupled mode theory, the mechanism of Fano resonance of a MIM waveguide coupled single T-shaped cavity with single baffle structure is studied, and the structure is simulated by the finite element analysis. On this basis, the formation process of quadruple Fano resonance with double T-shaped cavity structure is studied, and the influence of upper and lower T-shaped cavity structure parameters on Fano formant is analyzed. The results show that the Fano formans generated by the upper and lower T-shaped cavities do not affect each other, and two Fano formans can be tuned independently by a single T-shaped cavity, so the MIM waveguide coupled double T-shaped cavity structure containing metal baffle can achieve four Fano formans that can be tuned independently. This structure can provide an effective theoretical reference for the design of differential sensor and wavelength division multiplexer.

The accuracy of existing image-based methods for aerial imaging of flat-view images is limited. In this paper, a dynamic receptive field-based single-stage object detection algorithm is proposed to address this problem. First, the feature pyramid network is constructed by using SE-ResNeXt. This network is used as the backbone network to extract features efficiently. A bottom-up short connection path and a global context upsampling module are proposed to enhance the structural and semantic features of the detection layer. A dynamic receptive field-based detection subnet is designed to dynamically select the receptive field of an appropriate scale for object detection. Experimental evaluation is conducted on a realistic aerial dataset, and the results are compared with those of other related algorithms. The results show that the improved algorithm performs better on the dataset, and the performance score is evidently increased. It also exhibits good detection capability in scene images such as dim light, down view, oblique view, and dense objects.

Considering that the fully-convolutional siamese network algorithm for object tracking (Siamfc) algorithm is prone to tracking failure in cases such as heavy occlusion, rotation, illumination variation, scale variation, a siamese neural-network object-tracking algorithm with the distractor-aware model is proposed. First, the low-layer structural and high-layer semantic features were extracted from siamese networks; then, they were effectively fused to improve the representation ability of the feature. Second, the template adaptive strategy was used to update the template online to improve tracking accuracy in cases of occlusion and rotation. Simultaneously, the distractor-aware model based on color histogram features was introduced into the algorithm. The target response map was obtained by weighted fusion to estimate the position of the target while the adjacent frame scale adaptive strategy was used to estimate the optimal scale. To verify the effectiveness of the proposed algorithm, its performance was compared with those of various tracking methods on open-source datasets. Experimental results on the standard test dataset of the 2015 th object tracking show that the overall tracking accuracy and success rate of the proposed algorithm are 0.945 and 0.929, which is 2.9% and 2.8% higher than those of the Siamfc algorithm, respectively. Further, the proposed algorithm performs with high accuracy and success rate in the aerial test dataset of an unmanned aerial vehicle (UAV).

In this paper, an arbitrary waveform generation scheme of enhanced high-order harmonics based on injection locking technology is proposed. In this scheme, a series of higher and even order harmonic is enlarged and improved by injection locking technology. The high-order rectangular and triangular waves can be obtained by time domain superimposing the high-order harmonics and the first and third harmonics generated by nonlinear modulation. Also, a high-order sawtooth wave and reversed sawtooth wave can be obtained by time domain synthesizing the even-order harmonics of injection locking enhancing and the first and third harmonics generated by nonlinear modulation. In the experiments, a fifth-order triangular wave, a fifth-order rectangular wave, a third-order sawtooth wave, and a third-order reversed sawtooth wave with frequency of 5 GHz were successfully generated. Hence, the theoretical and experimental results show that compared to that of the same third-order waveform that simultaneous generating, root mean square error of the fifth-order triangular wave and the rectangular wave increased by 10%--37%. Moreover, it is found that the higher-order approximation waveform can be obtained by increasing the number of injection locking branches.

A multizone aspheric contact lens was designed to control myopia progression as well as correct myopia and astigmatism. An eye model of -3 D (Dioptre) myopia combined with -1.5 D astigmatism was constructed in Zemax software, based on which the anterior surface parameters of the contact lens were optimized. A multizone contact lens with a diameter of 14.4 mm and a central thickness of 0.06678 mm was obtained. The imaging performance and the relative peripheral myopic shift of the eye model with the designed contact lens were analyzed. The modulation transfer function (MTF) values at 50 cycle/mm are higher than 0.7 under 3 mm (in diameter) pupil for 0°--7° field of view (FOV) for distance vision, indicating that both myopia and astigmatism are corrected. Moreover, the MTFs remain relatively stable when the contact lens rotates within 30° or decentres within 0.7 mm. In addition, the myopic defocus of the model eye with the designed contact lens is up to -9.5 D at 25° FOV under 3 mm pupil, and around -6 D under 6 mm pupil for 0°-30° FOV. The results have indicated that the designed contact lens can provide greater peripheral myopic defocus, exhibiting highly potential to control the myopia progression.

Multi-parameter joint optimization is a trend in lithography resolution enhancement techniques. A multi-parameter joint optimization method for lithography based on the 3D topography difference of photoresist was proposed herein. By using the error of photoresist pattern at multiple depth positions as an objective function, the light source, the mask, the wavefront of the projection objective lens, the defocusing amount, and the exposure dose were jointly optimized, which improved the quality of the 3D topography of photoresist pattern. To obtain higher optimization efficiency, the adaptive differential evolution algorithm was adopted to optimize the light source and the mask, and different optimization methods were employed based on the characteristics of other parameters. The simulation results of dense lines, complex mask patterns with cross gate structure, and typical patterns in the static random access memory show that the maximum possible focal depth is 237 nm, 115 nm, and 144.8 nm, and the maximum exposure latitude is 18.5%, 12.4%, and 16.4%, respectively. Compared with the joint optimization technology of light source mask projection objective lens based on aerial image, the proposed method provides much larger process window.

In this paper, a metal-dielectric-metal nanoantenna array structure that supports multiple modes is designed. The mode properties and mediation for fluorescence emission of the proposed structure are analyzed. The transmission spectrum and electric field distribution of the proposed structure were simulated by the finite-difference time-domain method. Moreover, the mode properties of the localized surface plasmon mode and magnetic plasmon polaritons resonance mode, and the mode changes modulated by the excitation light polarization were analyzed. A dipole source was placed in the dielectric layer to simulate the luminescence process which the nanoantenna array structure regulating fluorescent molecule. The simulation results show that the radiation and non-radiation decay rate enhancement factors, quantum efficiency, and polarization characteristics of the fluorescence molecule are effectively modulated by the proposed structure. Besides, the emission spectrum can be tuned within a certain wavelength range by changing the polarization direction of excitation light.

EPR (Einstein-Podolsky-Rosen) steering is a special quantum phenomenon, which allows one side of the entanglement system to steer the other side, and has potential application value in one-way secure quantum network communication, quantum secret sharing and other quantum protocols. Based on the continuous variable (CV) bipartite entanglement swapping, covariance matrixes are reconstructed by asymmetric modulation or noise addition into one of the swapped mode. The EPR steering characteristics between two parts of the final output are analyzed and compared. The characteristic difference of the bipartite EPR steering between the two modes and the relationship of the EPR steering parameters with the classic modulation factor and the size of the noise are studied. The theoretical research results provide a feasible reference for the realization of the security of quantum communication.

Synthetic aperture lidar (SAL) can obtain high-resolution and high-data-rate images for remote target with small optical aperture under large forward squint angle condition. Thus, SAL can be an important mode of optic imaging detection. In this study, the working mode, system scheme, performance parameters, and key technologies of SAL with 100 mm diameter, 20 km detection range, and 0.05 m resolution are analyzed. A concept of a diffractive optical system conforming to the dome is proposed to reduce the aerodynamic influence and volume and weight of the equipment. The laser beam broadening and one-dimensional beam scanning method based on frequency scanning change is studied, and the beam pattern simulation results are presented by using the model of microwave phased array antenna. The results show that the SAL imaging detection technology based on curved-conformal diffractive optical system is feasible.

The resonant light absorption and scattering properties of gold nanospheroids were quantitatively studied for their application in photothermal therapy (PPTT) and biological imaging via the T-matrix method with a size-dependent dielectric function. The size parameters, including the minor and major semi-axes, of these Au nanospheroids were accordingly optimized; for the common wavelengths used in PPTT and biological imaging, the optimized nanospheroids exhibited the maximum absorption and scattering at 1064 nm and 1310 nm, respectively, within the range of specified size parameters. The comparison of these results with those obtained by optimized gold nanoshells demonstrated the obvious advantage of these gold nanospheroids for PPTT and biological imaging applications.

Based on the actual optical system parameters of the calibration spectrometer (SCS), the source of the radiance non-uniformity of the solar diffuser (SD) attenuated by the solar attenuation screen (SAC) is analyzed. Based on the physical model of the SD spectral radiance in orbit while calibration, combined with part of the parameters measured in the laboratory, the variation law of the SD’s radiance versus the angle of incidence (AOI) during the calibration measuring in a year is obtained. And comparing with the variation law of the SD radiance versus AOI set on SCS mearsured with a small divergence solar simulator as the source for illuminating in the laboratory, the correctness of the physical model of spectral radiance at the calibration time of the SD in orbit is verified. The emission radiance obtained by the illuminating SD can achieve energy non-uniformity in the SCS focal plane of better than 0.47%/(°), which satisfies the requirement that the SCS relative radiation calibration has a focal plane uniformity better than 99.5% at the working area of the radiation source. Finally, according to the actual application state, the uncertainty of the on-board spectral radiance standard surface source value formed by the SAC+SD method can be better than 2.13%.

Cerebral ischemia is one of the common diseases in neurosurgery, and a rapid and accurate method for cerebral ischemia detection is urgently needed. Transmissive terahertz time-domain spectroscopy is applied to detect cerebral ischemic tissue. In order to reduce the impact of individual differences, the degree of ischemia of brain tissue is studied by calculating the relative difference of the terahertz absorption coefficients between left and right brains. It is found that with the increase of ischemia time, the relative difference of absorption coefficient between left and right brains of fresh tissue first increases and then decreases, which is mainly caused by the increase of water content and the decrease of cell density in the ischemic area; meanwhile, the relative difference of absorption coefficient between left and right brains of paraffin-embedded cerebral ischemic tissue gradually decreases, which is mainly due to the gradual decrease of cell density in the ischemic region. The results show that the terahertz time-domain spectroscopy system can be used to detect the earliest 2 h cerebral ischemia, which provides an effective technical means for the early label free rapid diagnosis of cerebral ischemia.

In this study, the color space uniformity of a new color appearance model CAM16 is analyzed and evaluated. The vision uniformity of the color space of the CAM16 model is insufficient, which will affect the cross-media color reproduction accuracy and result in color difference with respect to the same colors under different viewing conditions. Therefore, a BFD color difference dataset is used to optimize the model for ensuring visual uniformity, and an optimized color appearance model CAM16-J'a'b' is proposed. Subsequently, the optimized color space is subjected to a uniformity test based on international Munsell color system. The results denote an improvement in the uniformity of the optimized color space, thereby providing a reference for cross-media color reproduction research.