Characteristic parameters of infrared photodetectors can not only represent the detection performance, but also can act as the key basis to improve the device performance in the development process. The measurement and analysis of characteristic parameters are important means to adequately evaluate the infrared-sensitive materials, fabrication technology and device performance. The definition, measuring and calculation methods of characteristic parameters of single-element infrared photodetectors are systematically reviewed, especially the analysis method of characteristic parameters. The analysis of characteristic parameters is that, device characteristics which cannot be directly measured can be analyzed from the directly-measured characteristics. Characteristic parameters such as activation energy, surface leakage current and lateral diffusion length of the carrier are analyzed based on directly-measured dark current. This work has enriched the evaluation and optimization methods of infrared photodetectors.

Dirac semimetal is a new kind of topological quantum material, which has attracted extensive attention due to its rich and interesting optical properties. In this paper, an one-dimensional photonic crystal based on Dirac semimetal Cd3As2, CdTe dielectric film and air defect layer is designed. The evolutions of the reflectance and transmittance of the photonic crystal with temperature, incident wavelength and incident angle are simulated and revealed by using the transfer matrix theory. The results show that the photonic crystal can produce a photonic band gap in the mid infrared band by using appropriate structural parameters. As the temperature increases, the width of the photonic band gap gradually becomes narrow, the reflectance and transmittance in the wavelengths of photonic band gap gradually decrease. At the oblique incidence, both the band edges and the central wavelength of photonic band gap shift toward short wavelength as the incident angle increases. When the incident light is p-polarized, the width of band gap gradually decreases. When the incident light is s-polarized, the width of band gap nearly keeps unchanged.

The optical beat method can be used to measure the wavelength stability of frequency-stabilized He-Ne laser and evaluate the wavelength uncertainty. A portable wavelength evaluation system for 633 nm laser used in measurement site is reported. The principle of beat frequency measurement technology, the basic structure of laser wavelength evaluation system and the comparison results with non-portable traditional beat frequency system are introduced. The wavelength evaluation system improves the traditional optical beat optical path and integrates it into a portable measurement system. The system uses a newly designed integrated optical beat module, a miniaturized high-precision frequency meter and a spectrum monitoring instrument to achieve the generation, counting and monitoring of beat signal with high signal-to-noise ratio, and independently develops the beat measurement data acquisition, processing and analysis software. The experimental results show that the system can realize the stability and uncertainty evaluation of laser wavelength in the measurement site, and improve the convenience and efficiency of field measurement.

With the rapid development of semiconductor array pumped Nd∶YAG solid laser,the application range is gradually widened.Its volume、energy and environmental adaptability have gradually become import indicators to measure the performance of laser.In order to meet the requirements of laser irradiation field, a miniaturized,high-energy,non-temperatuer controlled side-pump Nd∶YAG electro-optic Q-switched laser was developed in a wide temperature range-40～60℃.Multiple multi-wavelength(3-λ) arrays are used as pump sources,5mm×64mmNd∶YAG crystal round rod is used as working material,and LN crystal is used as electro-optic Q-switch.In the wide temperature range,the laser works normally,and the laser energy can be kept above 55mJ at 20Hz and 60mJ at 1Hz when the single pulse output.The size of the whole machine is 140mm×60mm×39.5mm, which can meet the development requirements of laser miniaturization,light weight and strong environmental adaptability.

In a distributed detection system, the positioning accuracy of the time difference of arrival (TDOA) method is directly restricted by the measurement accuracy of delay difference when the SNR of received signals is low. Here, an optimized TDOA localization algorithm is proposed based on multi-antenna signal combining. The combined signal is used to accurately calculate the delay difference between every two signals. Simulation results show that the proposed algorithm can reduce the positioning error by one order of magnitude compared with the traditional Gauss-Newton iterative method in the case of low SNR. A stable distributed optical fiber link is established, and further experimental results show that the positioning accuracy of the proposed algorithm can reach 1.6meters when the SNR is 1.1dB, and the positioning error is reduced by 86.8% compared with the traditional algorithm. The proposed algorithm will greatly expand the application scope of the TDOA localization method.

Aiming at the difficulty of quality detection of cigarette filters implanted with capsules, a non-destructive quality detection technology based on terahertz spectral information was proposed. According to the parameters of offset and transmittance, a capsules detection model is established to realize real-time and high-speed detection of different quality problems such as leaking, cracked, and offset beads. The results show that the detection speed of the system can reach 1000 pieces/min, and the detection accuracy exceeds 94%.

Static light scattering contains characteristic information of particle size, so static light scattering method is an effective means to measure the particle size of suspended matter in water body rapidly. However, the measurement accuracy of the static light scattering method for small particle size measurement is insufficient because the lateral and backward scattered light of particles is weak and not easily detected, and the forward scattering is affected by the Airy spot and there is a blind area for measurement. A low-level anisotropic scanning light scattering measurement method for small particle size suspensions in water is proposed, using a photomultiplier tube as the detector and a multi-angle continuous scanning method to detect the light scattering information of particles: by shortening the distance from the detector to the sample cell, the intensity of scattered light at the same angular resolution is increased, and the sensitivity of lateral and backward scattered light detection is improved; by deviating the detector from the excitation optical axis By avoiding the blind area of Airy spot, the forward large-angle scattered light detection can be achieved without changing the precision of the small-angle measurement of the front angle. On this basis, the method is combined with the meter scattering model to achieve the particle size measurement of small particle size suspensions. Experiments on different particle size samples show that the method can accurately measure the particle size of particles in the range of 350 nm to 2μm, and the relative errors of measurement of D50 for 2μm, 1.5μm, 500nm and 350nm specimens do not exceed 5.61%, all of which are lower than the relative errors of specimen uncertainty, and are better than the measurement results of laser particle size meters in the laboratory.

In the study of the autonomous navigation of outdoor intelligent mobile robots, bionic polarization navigation technology has gradually attracted attentions due to its characteristics that it is not easily affected by accumulated errors and electromagnetic interference. In order to improve the accuracy and enhance the robustness, a heading angle extraction method suitable for urban and haze weather is proposed for bionic polarization navigation. The image intensity information that is not easily affected by occlusion and haze factors is introduced, and the optimization cost is constructed for the image intensity information and the polarized skylight information respectively, and joint optimization is carried out to obtain the optimal heading angle. Outdoor experimental tests show that the information fusion method performs well in scenarios such as haze or sky occlusion. The standard deviation is 0.10~0.24° in the hazing scene, which is 83.1~99.7% higher than that of the single polarized skylight heading angle extraction method; the standard deviation in the sky occlusion scene is 0.04 ~0.09°, which is 90.9~96.7% higher than the single polarized skylight heading angle extraction method.

The focusing mechanism is an important guarantee to acquire remote sensing images for space camera. Synchronous accuracy on both ends of the focal plane is difficult to be eliminated, and it will affect sensing images. So synchronous accuracy analysis of double cam focusing mechanism and screw female focusing mechanism is important. First, it introduces working principle of two types of focusing mechanism, and then analyzes the sources of the synchronous error on both ends of the focal plane of two types of focusing mechanism, in the end, the synchronous accuracy of two types of focusing mechanism is tested. The calculation results show that the error of synchronous motion on both ends of the focal plane of two types by Statistical Method and Monte Carlo Method. Test results accord with the results of calculation. And the maximum error of synchronism is 20μm, the focusing mechanism of two types meets the requirements of practical application quite well.

To meet the need for rapid, high-precision measurement of the radius of curvature for large quantities of spherical optics, a radius measurement method based on differential confocal detection is proposed in this study. Firstly, scan a templet whose radius is known on its confocal position axially to obtain the fitted linear function; Secondly, replace the templet to the test sample in sequence, capture the differential confocal intensity without scan, map the single intensity to defocus with the linear function; Finally, calculate the radius under test by defocus and radius of template. Simulation and experiments show that the measurement accuracy is 12.2 ppm, and the measurement efficiency is 59 times higher than the traditional differential confocal scanning measurement. The measurement proposed only needs scanning once and replacing Sn N times to realize fast, high-precision, radius detection of N pieces of spherical surface. The proposed measurement provides a new way for high-efficiency and high-precision measurement of large quantities of spherical lenses.

Based on the theory of polarization interference, a method for measuring phase retardation and thickness of a wave plate in a wide spectral range is proposed. The relationships of the intersection wavelengths of spectral transmission curve and median transmission line are analyzed by matrix optics method, and the formulas for calculating the phase retardation and thickness of the wave plate are given. Error is also analyzed and it is shown that the maximum error of the measurement of phase retardation and thickness are 3.38°and 0.66μm respectively. The experiment results measured by a spectrophotometer show the validity of this method. The method can measure multiple physical parameters of the wave plate simultaneously, and has some advantages, such as, has no strict requirement for the directions of transmission axes of the polarizer and the analyzer and the fast axis of the wave plate, has no damage and pollution to the wave plate. The method has some application value in the fields of wave plate fabrication and quality evaluation before using a wave plate.

Aiming at the need of calibration detection of array camera, a radiometric calibration device of multi-light source array camera is developed in this work. By calculating the attenuation efficiency of the integrating sphere and testing the attenuation curve of the optical energy, the optical transfer curve of the system can be obtained. It employs a wide range measuring device to realize the real-time measurement of the system's light intensity change, and uses a variety of light sources combined with the attenuating wheel set to achieve the continuous output of the test light source with a wide dynamic range of 1.728×10-5~54Lux, respectively to meet the multi-parameter detection requirements of low-light array camera, high-light array camera and other array cameras. Finally, the multi-parameter detection experiment and calibration analysis of array camera are carried out in this work. The experimental results show that the device in this paper can realize real-time monitoring of illuminance characteristics and detect the quality of various array cameras for a long time, and can determine the operating environment and use scope of array cameras.

Czerny-Turner type grating spectral detection technology has become a hot spot in modern spectral instrument research due to its uniform dispersion, high sensitivity, and wide spectral detection range. It is widely used in biology, medicine, materials science and other fields, but is limited by astigmatism It is difficult to further improve the imaging quality and resolution of the system. In order to solve the above problems, a high-resolution Czerny-Turner spectral detection technology based on toric mirror is proposed. The astigmatism is corrected by the different focal lengths of the toric mirror in the meridional and sagittal directions. On the premise of ensuring the advantages of high sensitivity and wide band of the C-T spectrometer, the imaging quality and the system resolution are improved. Theoretical analysis and experimental results show that the prototype of toric mirror destigmatism spectrometer based on spectral splicing technology of 10nm scanning interval reaches 0.020nm in the working band range of 400~800nm. This technique provides a feasible way to improve the resolution of C-T spectrometer.

To achieve precise measurement of micro angle, a method of angular displacement measurement based on least square fitting wave vector estimation is proposed , the method uses the holographic theory and sampling theorem to record two holograms by secondary exposure, and calculates the relative parameters of the measured optical phase information by angle spectrum analysis, estimates the angular displacement relationship between the two wave vectors. The feasibility and accuracy of this method are verified by computer simulation, and the effects of pixel size, pixel number, and signal-to-noise ratio on measurement accuracy are analyzed. The consistency between theoretical calculation results and experimental results is verified by experiments. The experiment shows that when the number of CCD pixels is not less than 1000 pixels, the pixel size is not less than 4.6 μm, and the signal-to-noise ratio is not less than 20dB, the measurement method can achieve accurate measurement within the range of 3.9 °, and the mean error of measurement is controlled within 2.5×10-7rad, the standard deviation of measurement was controlled within 2.0×10-7rad.

Progressive additional lenses have emerged with their unique advantages, and are widely used by people. In order to detect it quickly and accurately, a progressive additional lens diopter detection method with low cost, simple device and easy operation is proposed. This method is based on the transmission fringe deflection method, and the distribution of diopter of the whole lens can be quickly obtained by calculating the deflection of light angle caused by the lens. The advantages and disadvantages of diopter detection methods are summarized. Firstly, the principle of transmission fringe deflection method is analyzed and studied. Secondly, the experimental device based on transmission fringe deflection method is constructed, and the camera calibration and phase calculation technology in the system are introduced. Finally, the diopter detection experiment of progressive additional lens is carried out, the results are analyzed and compared with VM-2000. The results show that this method can effectively and quickly detect the diopter distribution of progressive additional lenses, and can also be extended to other lenses.

Based on the principle of the Pockels effect, the electro-optical sensing unit and the electric field modulation mechanism in the AC-DC hybrid strong electric field sensor are designed and tested. Reasonably design the structure of the electro-optical sensor unit, select and prepare related devices. The test platform was built, and the test results showed that the input and output of the electro-optical sensor unit had good linearity, had a fast response to the change of the electric field waveform, and had good frequency characteristics. Its performance met the needs of measuring the modulated electric field waveform. The electro-optical sensing unit and the electric field modulation mechanism are used to construct a sensor to measure the strong AC and DC electric field.

In close range industrial photogrammetry, the automatic focusing of lens will lead to the fluctuation of camera parameters, resulting in the reduction of measurement accuracy. In order to solve this problem, a layered camera calibration method is proposed. The camera calibration technology based on plane checkerboard is analyzed, the automatic focusing principle of digital SLR camera and how it affects the change of camera principal distance are expounded, and the basic idea of the layered camera calibration method is emphatically analyzed. The layered camera calibration experiment reveals the variation law of the camera internal parameters and distortion coefficients with the calibration distances. The result of accuracy evaluation experiment shows that selecting appropriate camera internal parameters according to the photographing distance can significantly improve the accuracy of close range industrial photogrammetry.

As an important information transmission carrier, infrared images are corrupted by stripe noise for the difference in the response of the infrared focal plane array detection units and the non-uniformity of read-out circuit, which is harmful for the next analysis and research. In order to improve destriping results of convolutional neural network, infrared images destriping method based on wavelet dilated residual U-Net is proposed. The network first decomposes noisy image into vertical component,diagonal component, horizontal component and low frequency component by Haar discrete wavelet transform; Then mappings between noisy image and stripe noise are obtained sequentially through the coarse destriping and fine destriping network; The noise component is removed from input components to gain destriped components; Finally, destriped image is reconstructed by inverse Haar discrete wavelet transform.Experimental results illustrate that the method can remove stripe noise and preserve image details.

Explore the method of improving the U-net++ network and adding multi-channel feature fusion based on ultrasound images to achieve accurate and efficient automatic detection of intestinal endometriosis. The proposed neural network is improved on the segmentation network based on U-net++, adopting an end-to-end structure, inputting ultrasound image and its edge extraction image, and outputting the detection result of intestinal endometriosis.The experimental data were obtained from the endoscopic endoscopy images of 166 patients with intestinal endometriosis in Shenzhen People's Hospital. 133 cases were randomly selected as training samples and 33 test samples.In the network training process, the ten-fold cross-validation method is used for verification. The results show that On the 33 test set samples, the final average detection rate, precision rate, and recall rate of this method were 90.9%, 72.4%, and 89.8%, respectively. The improved neural network and multi-channel feature fusion input method can automatically detect the intestinal endometriosis area, and the detection has high robustness and accuracy, which can be used as a reference to assist doctors in clinical decision-making and intervention.

The shapes of the multiple sclerosis of magnetic resonance imaging images are usually very different, it leads to poor performance of traditional segmentation methods of multiple sclerosis automatic. In terms of this issue, a segmentation method of medical images based on attention dilated U-Net is proposed. Firstly, the dense dilated residual block is used instead of traditional convolutional layer in the cascade connection structure of the U-Net, in order to adjust the receptive field of each scale adaptively, so that the important information in each scale is extracted. Secondly, an attention model is add between the encoder and the decoder of same scale feature maps, in order to increase the feature map weight of the interest of region in each scale, and reduce the weight of the rest region, so that the information redundancy is prevented. Finally, a mixed loss function is used to train the networks on multi-scale feature maps, in order to solve the imbalanced classification problem of multiple sclerosis segmentation. Compared experimental results demonstrate the precision of proposed method increases 10.8% compared with U-Net.