Monocentric multiscale systems offer the advantages of miniaturization and a large field of view. In order to further realize the miniaturization and light weight of the large field-of-view system, we adopt the Galileo-type monocentric multiscale system form and design a monocentric multiscale system operating in the visible spectrum. The modulation transfer function of the system is greater than 0.3 at a frequency of 208 lp/mm, the root-mean-square radius of the full-field diffuse spot is smaller than the detector pixel size of 2.4 μm, and the imaging quality is close to the diffraction limit. The monocentric multiscale system structure has a couple of special characteristics: the relay lenses are closely arranged and the crosstalk stray light between the relay lenses seriously affects the imaging quality. To solve the problem, we apply the suppressing method the crosstalk stray light with the built-in stary light stop. On the basis, we carrying out the simulation and analysis of the stray light of the optical system. Analysis results show that the stray light coefficients are all reduced to less than 1×10⁻⁶ after the addition of the stray light stop, which verifies the crosstalk stray light suppression method.

A widely-wavelength-tunable Brillouin fiber laser (BFL) with improved optical signal-to-noise ratio (OSNR) based on parity-time (PT) symmetric and saturable absorption (SA) effect is present. This novel BFL realizes PT symmetry and SA effect through polarization-maintaining erbium-doped fiber PM-EDF Sagnac loop. By using the inherent birefringence characteristic of PM-EDF, two feedback loops in orthogonal polarization state are formed when the Strokes signal in injected. Which is composed of a PM-EDF and two polarization controllers (PCs). One of these loops provides gain in the clockwise direction with in the Sagnac loop, while the other loop generates loss in the counterclockwise direction. By adjusting the PCs to control the polarization state of the PM-EDF, a single-longitudinal-mode (SLM) BFL can be achieved, as the PT symmetry is broken when the SA participating gain and loss of stimulated Brillouin scattering (SBS) involving the SA effect are well-matched and the gain surpasses the coupling coefficient. Compared to previous BFLs, the proposed BFL has a more streamlined structure and a wider wavelength tunable range, at the same time, it is not being limited by the bandwidth of the erbium-doped fiber amplifier while still maintaining narrow linewidth SLM output. Additionally, thanks to SA effect of the PM-EDF's, the PT symmetric SBS gain contract is enhanced resulting in a higher optical signal-to noise (OSNR) The experimental results show that the laser has a wide tunable range of 1526.088 to 1565.498 nm, an improved OSNR of 77 dB, and a fine linewidth as small as 140.5 Hz.

Ghost images, as a type of stray light, are caused by residual reflected light between the optical surfaces. These images can degrade image clarity, annihilation targets, and severely affect the performance of optical systems. To investigate the impact of ghost images on optical system performance, we develope a Modulation Transfer Function (MTF) calculation model under the influence of ghost images generated by secondary reflection. We first introduce the method of analyzing and describing using the paraxial approximation. Then, starting from the definition of the MTF, and considering the influence of ghost image irradiance on the modulation of the image plane, an MTF calculation model under the influence of ghost images is constructed. By conducting a case study calculation on a system and comparing it with the simulation results, it is found that the maximum mean square error is less than 0.049373, which verifies the accuracy of the model. Furthermore, a detailed analysis is conducted, examining cases that exhibited larger errors and clarifying the range in which this calculation method can be applied. The research results indicate that the paraxial approximation method is both accurate and reliable when calculating the MTF under the influence of ghost images is accurate, and is applicable in most cases. This study serves as a valuable exploration in the ghost image analysis of optical systems.

The study of the radial structure and optical radiation characteristics of the cloud-ground lightning channel can provide a reference for the revealing of the microphysical mechanism of the formation and development of the cloud-ground lightning channel, and provide scientific guidance for the lightning protection. We carried out field observation experiments in the Qinghai Plateau region using a slit-less high-speed spectrograph. The clearly visible channel core was recorded in a cloud-ground lightning, and a weak luminescent region was found between the outer edge of the channel core and the external luminescent channel. Based on the spectral observation results, the optical radiation characteristics of the first return stroke and the third subsequent return stroke were compared and analyzed. The corona sheath model of the lightning channel is verified experimentally, the location of the connection point was determined, and the estimated striking distance of the two return strokes is 57 m and 53 m respectively, and the strongest point of the return discharge is confirmed at the connection point. It can be inferred that in the initial stage of the return stroke, the cloud ground lightning return stroke channel consists of the channel core , the weak luminescence region and the outer corona sheath from the inside to the outside, that is, the charge distribution along the radial direction of the lightning channel is uneven. The light radiation characteristics of lightning channel are closely related to the intensity and duration of discharge.

In order to meet the requirements of the national synchrotron radiation source, the anisotropic wet-etching technology of monocrystalline silicon grating with small blazed angle is studied, and the blazed grating suitable for the medium wave soft X-ray band is prepared. Based on the rigorously coupled wave theory, the structural parameters and process tolerance of the small blazed angle grating are designed. In the crystal alignment process, the crystal orientation of the silicon wafer is determined by ring-preetching, and then the grating mask is aligned with the crystal direction of monocrystalline silicon <111> based on the frequency doubling adjustment method. At the same time, the effect of the photoresist ashing technique and the active agent on the groove quality of the grating is investigated, and the scintillating gratings close to the ideal sawtooth groove shape are successfully prepared by the monocrystalline silicon anisotropic wet etching process. The experimental results show that the blazed angle of the prepared grating is 1°, the linear density is 1200 gr/mm, and the root mean square roughness of the blazed surface is less than 0.5 nm. This method can be applied to the fabrication of the medium wave soft X-ray blazed grating, which can greatly reduce the difficulty and cost of fabrication while achieving high diffraction efficiency.

As the pulse contains rich blood flow information of the humanbody, detecting the pulse and declucing the health status of human cardiovascular system are becoming a hot spot. In this study, PbS quantum dots with a size of 3 nm were synthesized using the hot injection method, and a PbS quantum dot photodetector was constructed on the surface of gold forked fingers electrode through spin coating. Based on the prepared PbS quantum dot photodetector, a data visualization pulse detection system was developed. Using the optoelectronic capacitance pulse wave recording method, we measured the same tester under different exercise states and different testers under the same exercise state, and displayed the measured data on the electronic display screen through circuit processing. The results show that under the illumination of 15.2 μW cm⁻² light intensity, its responsivity (R) and light detection rate (D*) are 0.33 A/W and 1.33×10¹² Jones under −3 V bias voltage, respectively. When used in the pulse measurement circuit, the system can effectively receive and measure the human pulse signal. It can be concluded that the pulse detection system based on the PbS quantum dot photodetector meets the application requirements in terms of sensitivity, stability, and reliability.

Bright-field imaging can provide cellular and histological morphological information, while fluorescence imaging can provide expression information of key proteins. Dual-modal correlation imaging based on both techniques is currently a common method for examining tissue samples in medical and scientific research. In clinical examination, however, correlation imaging between adjacent tissue slices is often used for observation. In such cases, both the tissue structure and the cellular level may be altered more or less, which is unfavorable when the sample volume is insufficient, the number of cells on the slices is limited, or precise point-to-point morphological information is required. Therefore, the development of single-slice dual-modal optical correlation imaging techniques which provides both tissue morphology and the distribution and expression of multiple target proteins on a single slice, can help to more accurately describe tumors and their microenvironment. This technique is particularly important in renal pathological testing where sample size is small. Renal pathology requires the use of bright-field imaging to obtain pathomorphological information of tissues and cells after hematoxylin-eosin staining, while the use of fluorescence imaging to obtain the distribution and expression of multiple target proteins is a mandatory molecular test for renal pathology screening. This paper focuses on the tissue sample processing methods that allow the coexistence of hematoxylin-eosin staining and immunofluorescence staining on the same renal slice. Improvements and comparative evaluations of the staining, de-colorizing and re-staining processes, as well as innovative fusion techniques for single-slice dual-modal imaging.

Non-uniformity correction is a crucial procedure for infrared imaging systems to achieve high quality infrared images. Currently, many large-aperture infrared radiation measurement system encounter numerous issues, such as non-uniformity correction being time-consuming and inadequate in-field applications. In this paper, a rapid and extensive dynamic non-uniformity correction algorithm is suggested for the requirement of continuous change of integration time in infrared radiation measurement system. The algorithm considers the impact of integration time effect and stray radiation of the optical system. The experimental verification was conducted by employing cooled mid-wave infrared radiation characteristic measurement system with a 25 mm aperture. The correction efficiency of the classical algorithm and the proposed algorithm are compared. The results indicate that the proposed algorithm is 3.4 times more efficient than the traditional non-uniformity correction algorithm. This paper evaluates the effect of the raw image and the two algorithms on the image correction using residual non-uniformity. Multiple integration times (0.6 ms, 3 ms and 3.5 ms) are used to simulate the continuous change of integration. The results indicate that the residual non-uniformity of the proposed algorithm is consistent and the corrected image has been effectively corrected.

In this study, we proposes an active polarization imaging method based on laser illumination to tackle the issue of low target detection contrast in strong light backgrounds, which is a challenge in conventional photoelectric detection. Through constructing a laser incident bidirectional reflection distribution model, a laser incident polarization bidirectional reflection distribution model and a target surface polarization model of laser illumination, the coupling relationship between the polarization characteristics of three typical target materials and the divergence angle of a laser beam is analyzed. Backlight observation experiments are conducted in a controlled darkroom to verify the impact of the scattering angle of the laser beam on the polarization characteristics of the target. The experimental results show an 86.11% increase in target contrast for active polarization imaging under strong light background compared to traditional passive intensity imaging. Additionally, the visible polarization characteristic of different target materials vary with different divergence angles, and the line polarization of metallic materials is higher than that of non-metallic materials. The experimental results are in good agreement with the theoretical analysis. The outdoor solar backlight observation experiment verifies the applicability of the research method in high-intensity light and long-distance settings. This study can lay a theoretical foundation for improving accurate target perception under a strong light background.

To address the bottleneck that makes the conventional polarization spectral imaging method difficult to apply to the ballistic platform, a fast multi-dimensional imaging guidance optical system based on array optics is proposed. The correlation model between channel resolution and telescopic magnification is constructed. The precise matching and efficient utilization of the parameters of the microlens array, spectral filter array, and micro-nano-polarization array detector are realized. Based on the conventional guidance head and commercial polarization detector, a multi-dimensional imaging guidance optical system with spherical dome is designed. The system adopts a 4×4 optical field segmentation layout, forming 16 spectral channels through the visible light band with a spectral resolution of 16 nm. A polarization spectral data cube in four polarization directions, such as 0°, 45°, 90°, and 135° is acquired efficiently under the conditions of a single optical path and a single detector. The system has an effective focal length of 150 mm and a structure length of 145 mm. Simulation results show that the full-field modulation transfer function of the system is close to the diffraction limit at the Nyquist frequency for 16 channels. The imaging quality meets the requirements of bullet-loaded target multi-dimensional detection and identification.

Hydroxyl (OH) is a widely existing product in the combustion reaction process. In combustion diagnosis technology, the two-dimensional spatial distribution based on hydroxyl is commonly used to characterize the structure of the flame front. Hydroxyl is an important parameter in characterizing the flame temperature, flame surface density, and heat release rate. The effective detection of hydroxyl in combustion flame is an important support for exploring the evolution of combustion dynamics and revealing the mechanism of random flame events. Planar laser-induced fluorescence (PLIF) has several advantages as an optical measurement method: high spatial and temporal resolution, non-intrusiveness, and component selection. PLIF successfully observed the structure of various combustion flames, such as Bunsen burner flame, turbulent flame, swirl flame, and supersonic flame, which provides an important reference for establishing combustion models. This paper starts with the basic principle of PLIF detection, this paper first reviews the development history and research status of PLIF technology in the field of combustion diagnosis. Secondly, it introduces the PLIF ultraviolet light source technology based on dye laser, optical parametric oscillation and Ti:sapphire tripling-frequency, and then discusses the characteristics of different technical routes. Finally, it prospects the development of UV laser technology for OH-PLIF.

Quantum Fisher information is used to witness the quantum phase transition in a non-Hermitian trapped ion system with balanced gain and loss, from the viewpoint of quantum parameter estimation. We formulate a general non-unitary dynamic of any two-level non-Hermitian system in the form of state vector. The sudden change in the dynamics of quantum Fisher information occurs at an exceptional point characterizing quantum criticality. The dynamical behaviors of quantum Fisher information are classified into two different ways which depends on whether the system is located in symmetry unbroken or broken phase regimes. In the phase regime where parity and time reversal symmetry are unbroken, the oscillatory evolution of quantum Fisher information is presented, achieving better quantum measurement precision. In the broken phase regime, quantum Fisher information undergoes the monotonically decreasing behavior. The maximum value of quantum estimation precision is obtained at the exceptional point. It is found that the two distinct kinds of behaviors can be verified by quantum entropy and coherence. Utilizing quantum Fisher information to witness phase transition in the non-Hermitian system is emphasized. The results may have potential applications to non-Hermitian quantum information technology.

In order to improve the image quality and variable range of focal length of liquid lens, by using dielectrophoretic and hydraulic driven, the double-interface liquid lens based on combination structure is designed, which mainly consists of dielectrophoretic double-liquid lens and PDMS membrane liquid lens. Firstly, the liquid lens model is established with Comsol software, the surface profile changes of droplets and PDMS membrane under different voltages are studied, then the surface profile data of two surfaces are derived. Secondly, the aspherical expression is used to fit with Matlab software, the interface profiles of droplets and PDMS membrane under different voltages and the corresponding aspherical coefficient are obtained. Finally, the corresponding double-interface combined liquid lens optical model is built with Zemax software, the image plane is selected as Gaussian image plane, then through the fabrication and the preliminary experimental research of the corresponding device, the simulation and experimental data are compared and analyzed. The results show that the variable range of focal length of the designed double-interface liquid lens based on the combined structure of the simulation is consistent with that of the experiment. Additionally, the zoom ratio can reach 2.1254 and the imaging resolution can reach 101.5937 lp/mm in the experiment. The double-interface liquid lens designed based on the combination structure has the advantages of simple compact structure, strong interface adjustability and high resolution imaging.

With its advantages of high torque ratio and stable low-speed operation, the Segmented Arc Permanent Magnet Synchronous Motor provides high-performance drive technology support for large-diameter astronomical telescope observations. Due to the existence of other internal and external interferences such as parameter distortion, harmonics, etc. during the operation of the motor, it is a challenge to improve the performance of the motor. To this end, this paper proposes an integral sliding mode controller based on a new reaching law and a hybrid control strategy that combines an expanded state observer and a load observer, aiming to optimize the traditional sliding mode control and enhance the anti-interference ability of the system. The parameters of the traditional reaching law are complicated and cannot suppress chattering well. The new reaching law simplifies the parameters and effectively overcomes the system chattering. Secondly, an expanded state observer is used to estimate the feedback speed, and then the q-axis current information and the estimated precise speed data are combined as the input of the load torque observer, which further improves the load observation performance and converts the load observation value into current for pre-processing. Feedback compensation is used to improve the anti-interference performance of the motor. Simulation and experimental results show that the proposed dual observer method can accurately observe the motor's speed and load, significantly enhancing the motor's ability to resist load disturbances; at the same time, the new sliding mode speed controller used reduces the motor speed overshoot, and suppresses the buffeting of the sliding mode to a certain extent, providing theoretical and experimental support for arc motors in high-precision observation applications of large-aperture astronomical telescopes.

In the digital grating displacement measurement technique, the CMOS pixel array of the camera is regarded as a ‘digitized’ grating. The micron-scale grating images can realize nanoscale displacement measurements by constructing the period difference between optical grating and digital grating. Combined with the detection light path of oblique incidence, it can be applied to the lithography machine’s focusing and leveling sensor to measure the wafer surface height accurately. In the actual measurement, the unexpected patterns on the wafer surface interfere with the reflection imaging of the optical grating, then affect the image processing results. In this paper, a process adaptability method for digital grating displacement measurement is proposed, which reconstructs the light intensity and recovers the light intensity curve from the CMOS image when interference patterns exist. The proposed method shows good stability when the large area pattern appears on the wafer substrate, and can adapt to multiple surface defects such as scratches, particles, stains and grooves. The experimental results show that the mean square error of the light intensity curve is significantly reduced and the method’s Z-direction error correction is within ±33 nm (±3σ=±41.2 nm) after reconstructing the light intensity. This method can enhance the process adaptability of the digital grating focusing and leveling sensor. Therefore, it can serve as a technical reference for the focusing and leveling method.

In order to precisely control the direction of laser beams, this paper analyzes the error caused by the grating tilt in the system based on the optical beam pointing algorithm of the dual liquid crystal polarization grating system. Firstly, a ray tracing method based on the diffraction grating equation is used to solve the outgoing beam pointing, introducing the incident beam pointing and grating tilt angle. The correctness and accuracy of this method are verified by comparing with simulation results. Secondly, by analyzing different situations of grating tilt, this article provides expressions for the grating attitude under different tilt conditions, and, in combination with the ray tracing method, obtains the expressions for the outgoing beam pointing for corresponding situations, analyzing the zeroing error and rotation error caused by grating tilt. The research results indicate that within the range of 0° to 0.3° grating tilt angle, the zeroing errors are within 0.25 mrad and 2 mrad respectively, and the rotation errors are around 85 mrad and 430 mrad respectively. This article describes a method for accurately calculating the pointing direction and grating tilt errors in the exit beam of a dual liquid crystal polarization grating system.

In order to solve the problems of low image exposure, low contrast and difficulty of feature extraction in real-time animal monitoring at night, we proposed a lightweight self-supervised deep neural network Zero-Denoise and an improved YOLOv8 model for image enhancement and accurate recognition of nocturnal animal targets. The first stage of rapid enhancement was performed by lightweight PDCE-Net. A new lighting loss function was proposed, and the second stage of re-enhancement was carried out in PRED-Net based on the Retinex principle and the maximum entropy theory, using the original image and fast enhancement image corrected by the parameter adjustable Gamma. Then, the YOLOv8 model was improved to recognize the re-enhanced image. Finally, experimental analysis was conducted on the LOL dataset and the self-built animal dataset to verify the improvement of the Zero-Denoise network and YOLOv8 model for nocturnal animal target monitoring. The experimental results show that the PSNR, SSIM, and MAE indicators of the Zero-Denoise network on the LOL dataset reached 28.53, 0.76, and 26.15, respectively. Combined with the improved YOLOv8, the mAP value of the baseline model on the self-built animal dataset increased by 7.1% compared to YOLOv8. Zero-Denoise and improved YOLOv8 can achieve good quality images of nocturnal animal targets, which can be helpful in further study of accurate methods of monitoring these targets.

Aiming at the wavefront detection without an ideal point beacon in the adaptive optical system under the strong turbulent environment, we propose a method to detect the optical field information of extended beacons using a Plenoptic sensor. The optical field imaging principle, wavefront phase reconstruction algorithm, and error influence rule of extended beacons were studied. The imaging process of the extended beacon on the optical field sensor was simplified through the equivalence method, and the optical field images were rearranged in a specific way. The image cross-correlation and Zernike mode methods were used to realize the wavefront reconstruction of the 0° field of view. Simulation studies are conducted on error-influencing factors such as different input aberration coefficients, the number of single-row microlens elements, and noise. The results show that when the input aberration is less than 6.5 λ, the wavefront reconstruction accuracy is about 0.08 λ. For the image detector with an image resolution of 1080×1080 and pixel size of 5.5 μm, the wavefront reconstruction accuracy is the highest when the number of single row microlens units is between 40 and 50, and the system noise hardly affects the accuracy. Finally, an extended beacon wavefront detection system was built to reconstruct the four aberrant wavefronts of 0° field of view by detecting the extended beacon. The wavefront reconstruction accuracy of the experimental system is about 0.04 λ, which meets the wavefront detection requirements of the adaptive optical system.

Beam arrays have great application value in free-space optical communication. The light intensity evolution and the on-axis scintillation index of radial Gaussian vortex beam array propagating through atmospheric turbulence are analyzed based on multi-phase screen simulation. The effect of initial beam parameters on the scintillation properties of radial Gaussian vortex beam array is studied, and the variation of the on-axis scintillation index values of radial Gaussian vortex beam array and a Gaussian vortex beam is compared. The results indicate that in the weak fluctuation regime, the on-axis scintillation index of Gaussian vortex beams remains within a numerical range of less than 1, while the on-axis scintillation index of radial Gaussian vortex beam arrays is around 1. In the medium fluctuation regime, the on-axis scintillation index of the radial Gaussian vortex beam array is smaller than that of a single Gaussian vortex beam. And the on-axis scintillation index of radial Gaussian vortex beam array decreases with the decrease of orbital angular momentum and the increase of radial array radius. The research results have certain theoretical significance and application value for vortex optical communication in turbulent atmospheric environments.

Liquid crystal optical phased array (LC OPA) is widely used in lidar, laser communication and laser weapons to scan and control laser beams. In order to realize the optimal design of LC OPA and high-precision control of laser beam, this paper focuses on the influence of working wavelength, number of pixels, pixel size and effective grey levels on beam pointing accuracy. Firstly, according to the principle of liquid crystal phase modulation, the effective scanning angle and diffraction efficiency of the period grating and the variable period grating methods are simulated and analyzed. Secondly, assuming the phase modulation is equally divided by the driving voltage, the variation law of the pointing error with the working wavelength, the number of pixels, the pixel size and the effective grey levels is simulated and analyzed, and the multivariable universal formula is derived. Thirdly, the pointing accuracy of the nonuniform phase modulation is simulated, analyzed, and compared with the results of the uniform phase modulation. Finally, the relationship between the effective grey levels and the pointing error is verified by experiments, and the validity of the empirical formula is preliminarily confirmed. The research results can provide a theoretical basis for the design of LC OPA.

In order to acquire and monitor the low frequency vibration signal, a two-dimensional vibration sensor with symmetrical circular flexure hinge is designed, which can work in the x and z axes. The mechanical characteristics of the sensing structure are analyzed theoretically. The model was established in Comsol for simulation analysisand the structure is optimized by finite element method. The hinge resonant frequency is designed as 420 Hz. The fiber Bragg grating is pasted on the surface of the hinge structure as a strain detection device, and the dynamic demodulation of FBG is realized by edge filter method. The performance of the sensor was tested with a standard shaking table. The experimental results show that the natural frequency of the sensor in x and z axes is 420 Hz, and the operating frequency range is 20−300 Hz. And the average sensitivity in the flat region is 1847.32 mV/g, the acceleration resolution is 5.41×10⁻⁴ g. The sensor demonstrated a lateral interference level of less than 5% in all two-dimensional orientations. The sensor designed in this paper is a two-dimensional vibration sensor, which is suitable for highly sensitive detection of low-frequency vibration signals, such as vibration detection of Bridges and tunnels and health monitoring of mechanical equipment.

In order to meet the needs of broad band, high diffraction efficiency and polarization independent, a double-layer trapezoidal polarization independent beam grating is proposed in this paper. Firstly, based on the strict coupled wave theory, a design model of polarimetric independent combined beam grating based on particle swarm optimization algorithm is established, and the efficiency characteristics are optimized by randomly generating characteristic wavelengths. Then, the effects of slot depth, width ratio, side Angle and other structural parameters on the diffraction efficiency and bandwidth of single-layer and double-layer trapezoidal grating are analyzed in detail. Finally, the electric field enhancement characteristics of the two structures are analyzed and discussed. The results show that the double-layer trapezoidal polarimetric beam independent grating achieves a theoretical diffraction efficiency of more than 99% in the bandwidth range of 51 nm (1038 nm−1089 nm), and has a larger process tolerance than the traditional single-layer trapezoidal structure, which meets the bandwidth of 30 nm and the high diffraction efficiency of 98% in the tolerance range, and has lower near-field enhancement of the grating. Can have a stronger resistance to laser damage. The proposed double-layer trapezoidal grating with wide band and high diffraction efficiency can improve the output power of laser system, and has great application value in the field of laser beam combination.

Segmented mirrors co-phase error detection is one of the hot topics in current scientific research. Co-phase detection technology based on broad-band light source solves the problem of long measurement times caused by the Shackle-Hartmann method due to the low target flow rates, which improves the detection accuracy and range of piston error. However, in the application of the current broad-band algorithm, the complex environment and the presence of disturbing factors such as camera perturbations will cause the acquired circular aperture diffraction images to contain a certain amount of noise, which will lead to the correlation coefficient value being lower than the set threshold, and reduce the accuracy of the method or even make it ineffective. To tackle this problem, the paper proposes integrating an algorithm based on Denoising Convolutional Neural Network (DnCNN) into the broad-band algorithm in order to realize the control of the noise interference and retain the phase information of the far-field image. First, the circular hole diffraction image obtained using MATLAB is used as the training data for DnCNN. After the training, the images with different noise levels are imported into the trained noise reduction model to obtain the noise reduced image as well as the peak signal-to-noise ratios of the circular hole diffraction images before and after noise reduction and the structural similarity between the two and the clear and noiseless image. The results indicate that the average structural similarity between the denoised image and the ideal clear image has significantly improved compared to before processing, and this achieves an ideal denoising effect, which effectively increases the ability of broad-band algorithms to cope with the effects of high noise conditions. This study has strong theoretical significance and application value for exploring the broad-band light source algorithm for applications in practical co-phase detection environments.

This paper reports a 4.7-μm mid-wave infrared quantum cascade laser based on double active regions, with a ridge width of 9.5 μm. It can achieve continuous single transverse mode operation at room temperature. By inserting 0.8-μm InP, the original single active region is transformed into a double active region structure, which can significantly reduce the peak temperature of the device's active region and suppress the generation of higher-order transverse modes. At a temperature of 288 K, the device with a double active region structure with a cavity length of 5 mm has a threshold current density of 1.14 kA/cm², a continuous output power of 0.706 W, a fast axis divergence angle of 27.3°, and a slow axis divergence angle of 18.1°. The devices with a double active region structure have no degradation in their maximum optical output power and show a significant improvement in the beam quality in the slow axis direction of the device when compared with conventional devices with a single active region structure. These results provide a solution to the problem of the slow axis beam quality of high-power medium wave quantum cascade lasers.

Traditional cleaning methods can not clean small pollution particles on the surface of cultural relics. Moreover, it can easily cause irreversible damage to the surface of cultural relics. In order to improve the ability to clean pollutants, laser cleaning technology has been gradually applied to the cleaning of different types of cultural relics. In this paper, we develop a nanosecond laser cleaning system to clean the simulated marble samples and marble fragments in the Palace Museum. The object of the cleanout is black crust pollutants. To avoid the yellowing effect, a dual wavelength combination of 1064 nm near-infrared and 355 nm ultraviolet was used for laser cleaning of simulated marble samples. When the energy density ratio of these two wavelengths is 3∶2, photos from the microscopic observation system show a good cleaning effect. This ratio (3∶2) is then applied to marble fragments samples. The spectrometer is utilized to evaluate the cleaning effect. The experimental results confirm the advantages of laser cleaning and also provide reference parameters and evaluation methods for laser cleaning of pollutants on marble surface. At the same time, it also offer insights for the application of laser cleaning technology to the cleaning of other stone artifacts.

To reduce the influence of cloud on the process of sea surface textural analysis in marine remote sensing images, this paper studies the removal of cloud interference by information entropy-low-pass filter combined mask. We first analyze the basic principle and limitations of the existing remote sensing image declouding algorithms, points out its inapplicability in remote sensing applications with high fidelity requirements, and then proposes a cloud interference removal technology based on information entropy-low-pass filtering combined mask. These include destriping procedures with improved moment matching of remote sensing images, local information entropy filtering, and joint low-frequency filtering as the correction parameters of each pixel in remote sensing images. The algorithm has the characteristics of low complexity and time efficiency. Experimental results show that, compared with the existing algorithms, the proposed method can greatly enhance the texture detail information of thin cloud areas and cloud edges at the same time under the premise of low computational complexity, and it can reach more than 7.8 in image information entropy, over 60 in contrast, and above 200 in mean gradient. In image details comparison, the proposed algorithms can improve the texture details without inducing artifacts and non-uniformity, which can further to meet the requirements of high fidelity for military remote sensing applications.

Long-period fiber gratings have the advantages of small size, corrosion resistance, anti-electromagnetic interference, and high sensitivity, making them widely used in biomedicine, the power industry, and aerospace. This paper proposes a long-period fiber grating sensor based on periodic microchannels. First, a series of linear structures were etched in the cladding of a single-mode fiber by femtosecond laser micromachining. Then, the laser-modified region was selectively eroded by selective chemical etching to obtain the periodic microchannel structure. Finally, the channels were filled with polydimethylsiloxane (PDMS) to improve the spectral quality. The experimental results show that the sensor has good sensitivity in the measurement of various parameters such as temperature, stress, refractive index, and bending: it has a temperature sensitivity of −55.19 pm/°C, a strain sensitivity of −3.19 pm/με, a maximum refractive index sensitivity of 540.28 nm/RIU, and a bending sensitivity of 2.65 dB/m⁻¹. All of the measurement parameters show good linear responses. The sensor has strong application prospects in the field of precision measurement and sensing.

Brain glioma is a typical and common brain tumor with low cure rate and high recurrence rate. Precise identification of tumor boundaries is an important prerequisite for reducing recurrence and improving prognosis. It has an important clinic significance for glioma to develop a rapid, high-sensitive and label-free diagnostic method. Raman spectroscopy can reflect the chemical and structural information of substance at the molecular level due to its fingerprint characteristics, which has already shown great prospects for the location and identification of glioma. Firstly, we introduce the different types of Raman spectroscopy technologies in this paper. Secondly, the research status of glioma based on Raman spectroscopy is reviewed. Finally, the future development of glioma through Raman spectroscopy is prospected.

To study the visible light polarization reflection characteristics of typical terrain target materials, an improved Blinn type shadow masking function is introduced according to traditional "V" surface structural defects. Additionally, the effects of mirror reflection, diffuse reflection, and volume scattering are comprehensively considered. A six-parameter two-dimensional reflection distribution function model for typical terrain target materials is established. Testing of polarization characteristics is conducted on target samples with different materials (polypropylene plastic sheet, 99 alumina ceramic sheet, iron sheet, green painted aluminum sheet) in the visible light 600 nm wavelength band. A genetic algorithm for parameter inversion is used. The experimental and simulation results show that compared with the traditional "V" shielding model, the polypropylene plastic plate model has the highest accuracy improvement and a 70.61% increase in RMSE percentage in the impact of observation angles on the polarization characteristics of the target material surface at an incidence angle of 50°, relative azimuth angle of 180°, and 0° to 60°. Compared with the two reference models, the DoLP model shows a significant improvement in accuracy at an incidence angle of 50°, observation angle of 50°, and relative azimuth angle of 90° to 270°. The model accuracy has improved by at least 24.73 percentage points. The minimum root mean square error of linear polarization is only 1.29%. For the material in this article, the polarization characteristics depend on the value of its complex refractive index. When the incident angle is determined, the observation angle is between 0° and 60°, and the relative azimuth angle is between 0° and 360°. The larger the n/k ratio, the higher the peak of the linear polarization degree. In the visible light band, the wavelength has little effect on the degree of linear polarization.

Solar glint is a significant factor influencing sea surface target detection. For land observation platforms, a sea surface glint suppression method based on the reconstruction of common characteristics of linearly polarized images is proposed using the polarization characteristics of glints. The proposed method uses a focal plane polarization camera to obtain four-channel linear polarized images, calculates the scene’s polarization information, and generates a glint suppression image. Based on suppressing scene glint with polarization information combined with the characteristics of linear polarization images, the light intensity components of the glint suppression image are decomposed into common and characteristic components, and new weight factors are given to obtain the reconstructed glint suppression image. The results of field polarization experiments show that the maximum relative decrease in the proportion of saturated pixels in the reconstructed glint suppression image compared to the intensity image was 79.07%, and the maximum relative increase in spatial frequency and contrast were 73.77% and 172.73%, respectively. The method proposed in this paper effectively suppresses the glint noise in the sea scene and performs well in restoring background detail information.

The development of third-generation infrared focal plane detectors allows them to respond simultaneously to two different bands of infrared radiation, and the dual-band image brings great benefits to target detection and identification. In this paper, for aerial detection applications, adopting 320×256 dual-color infrared cooled detector, a large-magnification-ratio cooled infrared dual-band zoom optical system with operating bands of 3.7−4.8 μm in the midwave and 7.7−9.5 μm in the longwave has been designed for infrared detection of targets. The optical system adopts a combination of transmissive and refractive structures to realize an optical four-field-of-view switching wide-range zoom, and in order to meet the 100% cold diaphragm efficiency, a secondary imaging mode is adopted. The four-field focal lengths of the optical system are 32 mm, 200 mm, 800 mm, and 1600 mm, and the zoom ratio is 50×. The experimental results show that the optical system is close to the diffraction limit at a modulation transfer function eigenfrequency of 17 lp/mm in each of the dual-band zoom states. The optical system has the characteristics of dual-band, large zoom ratio, large zoom range, fast switching of multiple fields of view, simple and compact structure, and high-quality imaging, which will be widely used in the security fields such as searching, reconnaissance, and so on.

Phase delay mirrors were designed and prepared to regulate femtosecond laser systems’ group-delay dispersion (GDD). This paper systematically investigates the principle of compensating group-delay dispersion by phase-delay mirrors. Nb₂O₅ and SiO₂ were used as the materials with high and low refractive indices. The group-delay dispersion curves were smoothed out by pairing the phase-delay mirrors with their complementary mirrors. The phase-delayed mirrors with phase modulation data of −800 GDD were prepared, and the reflectivity reached more than 99% in the range of 900 nm−1100 nm. The bandwidth adjustment problem of femtosecond laser systems is solved to meet the requirements of femtosecond lasers

Visual detection of sonar image is one of the important technologies in the field of resource exploration in complex waters and underwater foreign object target detection. Aiming at the problem of weak features and background information interference of small targets in sonar images, this paper proposes a weak feature confocal channel modulation algorithm for underwater sonar target detection. Firstly, in order to improve the model's ability to capture and characterize the information of weak targets, we design a weak target-specific activation strategy and introduce an a priori frame scale calibration mechanism to match the underlying semantic feature detection branch to improve the accuracy of small target detection; secondly, we apply the global information aggregation module to deeply excavate the global features of weak targets to avoid the redundant information from covering the small target's weak key features; lastly, in order to solve the problem of the traditional space pyramid Finally, in order to solve the problem of traditional spatial pyramid pooling which is easy to ignore the channel information, the confocal channel regulation pooling module is proposed to retain the effective channel domain small target information and overcome the interference of complex background information. Experiments show that the model in this paper achieves an average detection accuracy of 83.3% on nine types of weak targets in the underwater sonar dataset, which is 5.5% higher than the benchmark, among which the detection accuracy of iron bucket, human body model and cube is significantly improved by 24%, 8.6% and 7.3%, respectively, which effectively improves the problem of leakage and misdetection of weak targets in the underwater complex environment.

Aiming at the low accuracy of existing non-contact blood oxygen saturation measurement methods in dynamic head scenes, a denoising method based on improved adaptive noise complete set empirical mode decomposition and wavelet threshold is proposed to extract pulse wave signals with high signal-to-noise ratio. Firstly, in order to solve the problem of false components and mode aliasing in the early stage of decomposition and reconstruction, white Gaussian noise is added to the decomposition process to make it become an improved ICEEMDAN (ICEEMDAN), so as to reduce the residual noise in the modal components. Then, ICEEMDAN was used for mode decomposition of pulse wave signals of red and blue channels, and db8 wavelet basis function was used for 3-stage decomposition and reconstruction of components conforming to the spectrum range of blood oxygen, and the reconstructed signals were used for subsequent calculation of blood oxygen value. Finally, the experimental comparison and analysis of the blood oxygen saturation results measured in different dynamic head scenes show that the average error of blood oxygen saturation obtained in different head scenes is 0.73%, which is 1.93% lower than the average error of other algorithms. The denoising method proposed in this paper has good stability in different head scenes and can meet the needs of daily blood oxygen saturation measurement.

The teaching scan is cumbersome and has poor versatility when performing scan reconstruction. The current focus of viewpoint planning is still to automatically obtain the minimum set of viewpoints covering the model. To realize automated 3D scanning and reconstruction of parts of different complexity levels, this paper studies issues such as viewpoint redundancy, viewpoint occlusion, and binocular reconstruction constraints that may occur during viewpoint planning. First, given the problem that it is difficult to completely scan the model with existing viewpoint planning, Lloyd's algorithm was improved by analyzing the characteristics of surface structured light scanning and proposed using the energy function of Euclidean distance and normal vector deviation to perform Voronoi partitioning of the model to generate Initial scanning viewpoint. Then, to address the viewpoint redundancy problem, an iterative algorithm for splitting the initial scanning viewpoints is proposed. Finally, given the problem that the generated viewpoints are prone to occlusion, a line-of-sight de-occlusion strategy is proposed, and to improve the model coverage, a method of using panning viewpoints is proposed. The experimental results show that: under the optimal number of viewpoints, the coverage rate of automobile castings and transmission housing reaches more than 94%, the coverage rate of simple curved automobile sheet metal reaches more than 99.5%, and the automatic steering knuckle of the automobile is realized. Planning scanning meets the coverage and efficiency requirements of automatic viewpoint planning and the adaptability requirements for parts of different complexity.

Triangular mesh model registration is an important part of industrial automation detection software. The registration accuracy has an important influence on the shape and position tolerance of mechanical parts. Aiming at the problems of low accuracy and poor robustness of automatic registration of triangular mesh models, this paper proposes a segmentation method for enhanced features in automatic registration of triangular mesh models for mechanical parts. Firstly, the K value of the feature segmentation of the triangular mesh model is determined, and the seed points are determined by the Laplacian matrix for iterative initialization. Secondly, this paper uses the appropriate region shape agent and cost function to accelerate the process, and performs multi-source iterative clustering to obtain the feature segmentation results. Finally, based on the feature segmentation results of the triangular mesh model, the coarse registration based on the singular value decomposition method is performed, and the fine registration is performed according to the EM-ICP. Compared with the traditional feature descriptor coarse registration and ICP fine registration method, the experimental results show that the registration error of the proposed method is reduced by 25.2 %, and the automatic registration time is shortened by 62.6 %, which effectively improves the accuracy and efficiency of the automatic registration of the triangular mesh model.

Narrow linewidth lasers are the basic components of spectroscopy and precision metrology and other experiments. Because semiconductor laser is very sensitive to external optical feedback, the phase noise of semiconductor laser can be suppressed by using the high bandwidth of optical feedback, and then the linewidth can be narrowed. So we use fiber Bragg grating as feedback element and build a long external cavity feedback loop. In order to reduce the influence of external environment temperature fluctuation and air flow disturbance, we control the temperature of the fiber of the feedback optical path. Then the maximum temperature fluctuation within 1 hour is reduced from 0.039 °C to 0.003 °C, and the variance of temperature fluctuation is reduced by two orders of magnitude. In addition, we also test the effect of feedback bandwidth on laser linewidth. Although the bandwidth of the fiber Bragg grating used in our experiment is much larger than the free-running laser linewidth, we still observe that the laser linewidth is narrowed, and the smaller the bandwidth of the fiber Bragg grating, the narrower the laser linewidth. For this phenomenon, we believe that there should be a negative feedback mechanism in the feedback loop, which can stabilize the laser linewidth to a certain slope of the feedback spectrum, so the narrower the feedback bandwidth of the fiber grating, the larger the slope of the feedback spectrum, the more sensitive the feedback. In addition, by changing the feedback power of FBG in the range of 0~1 mW, we observed that at the reflected power of 0.8 mW, the optical feedback narrowed the laser linewidth from the free-running 100.5 kHz to the narrowest 11.5 kHz, and at the reflected power of 1 mW, phase noise in the range of 0.2 kHz to 2 MHz is suppressed by about 22 dB.

In order to improve the detection accuracy of Doppler asymmetric spatial heterodyne (DASH) interferometer in harsh temperatures, an Opto-mechanical-thermal integration analysis was carried out. Firstly, the correlation between the interference phase and temperature is established according to the working principle and the phase algorithm of the interferometer. Secondly, the optical mechanical thermal analysis model and thermal deformation data acquisition model are designed. The deformation data of the interference module and the imaging optical system at different temperatures are given by temperature load simulation analysis, and the phase error caused by thermal deformation is obtained by fitting. Finally, based on the wind speed error caused by thermal deformation of each component, a reasonable temperature control scheme is proposed. The results show that the interference module occupies the main cause, the temperature must be controlled within 20±0.05 °C, and the temperature control should be carried out for the temperature sensitive parts, and the wind speed error caused by the part is 3.8 m/s. The thermal drift of the magnification of the imaging optical system and the thermal drift of the relative position of the imaging optical system and the detector should occupy the secondary cause, which should be controlled within 20±2 °C, and the wind speed error caused by the part is 3.05 m/s. In summary, the wind measurement error caused by interference module, imaging optical system, imaging optical system and relative position of detector can be controlled within 6.85 m/s. The analysis scheme and temperature control measures presented in this paper can provide theoretical basis for DASH interferometer engineering applications.

Laser beam quality is one of the key indicators considered when measuring the performance of laser applications. To meet the application requirements of long-distance optoelectronic countermeasures, this paper researches the design of unstable resonators and beam quality improvement techniques for non-chain DF lasers. Three sets of positive branch confocal unstable resonators with different magnifications are designed. An experimental setup for an unstable inner cavity resonator is constructed with two convex mirror structures: transverse support and longitudinal support. The transverse support structure is equipped with a circulating water-cooling channel. Using 86.5% surrounding energy to define laser beam diameter, the laser beam quality is evaluated with beam quality factor β, and the energy and beam divergence for two support types of convex mirrors are compared. Research has found that, under the same conditions, the laser energy of unstable resonators with longitudinal support is 6% higher than that of the transverse support structure. Still, the far-field divergence angle is 9% larger than that of the transverse support structure. Although the water-cooled transverse support structure has energy shielding, its high thermal stability significantly improves the quality of the laser beam. A beam divergence of θ_0.865 = 0.63 mrad with beam quality factor β=1.83 is obtained at M=2.25 with a transverse support unstable resonator. The laser energy under this condition is 2.34 J, the laser pulse width is 88.2 ns, and the peak power reaches 26.5 MW.

Shared secret-key extraction from random channel characteristics is an effective approach to ensuring the physical layer security of atmospheric optical channels. The secret-key generation rate and disagreement rate are two issues that attract a lot of attention. Using the random characteristics of atmospheric turbulent optical channels as a shared source of randomness, a secret-key extraction scheme for multiple-input multiple-output (MIMO) atmospheric optical channels is proposed. The alternative singular value decomposition is used to decompose the channel matrix; the correlation between the two channel characteristic sequences obtained by the two legitimate parties is enhanced by carrying out a simple moving average; a channel quantization alternating scheme with a single threshold is used to quantize the resultant channel characteristic sequences. The two legitimate parties generate random controlling sequences for coding mapping based on differential diversity values, which are used in performing coding mapping of the quantized bits of the channel characteristic sequences generated by the channel quantization alternating scheme with a single threshold. The experimental results show that our scheme’s initial key disagreement rate can reach 5.2×10⁻⁴ at a signal-to-noise ratio of 30 dB, and that the generated random bit sequences have passed the National Institute of Standards and Technology (NIST) randomness test. This paper’s results are useful in the implementation of secret-key extraction from atmospheric MIMO optical channels.

The coal-fired boiler combustion process's economic, safety, and environmental performance holds great significance when constructing smart power plants. In coal-fired boiler combustion, H2S and CO are the two main high-temperature corrosive gases. They not only corrode the boiler near the wall surface but also pose severe harm to the atmospheric environment through their exhaust gases. Based on the near-infrared tunable diode laser absorption spectroscopy technology, combined with wavelength modulation spectroscopy and frequency division multiplexing technology, an unstaffed online real-time monitoring instrument for H₂S and CO gas concentrations in the main combustion zone of coal-fired boilers was developed. Gas absorption spectroscopy in the 6335−6341 cm⁻¹ range was simulated, and two near-infrared lasers near 1.5 μm were selected as the laser source. A high-temperature and corrosion-resistant Herriott-type multi-pass cell was developed to attain an effective optical path length of 15 m for the interaction between laser and gas. Hardware circuits and corresponding firmware programs were developed to attain secondary demodulation of the absorption spectroscopy signals of H₂S and CO and concentration inversion. The linearity and Allan variance experiments showed linear fitting correlation coefficients of 0.9998 and 0.9995. At 73 s and 53 s integration times, the minimum detection limits for H₂S and CO were 0.2×10⁻⁶ mol/mol and 0.344×10⁻⁶ mol/mol, respectively. Finally, the developed instrument was applied in the combustion atmosphere of the main combustion zone of a 300 MW coal-fired boiler under a four-corner tangential firing system, and synchronous measurements of H₂S and CO near the water-cooled wall were conducted. The results indicated a positive correlation between the concentrations of H₂S and CO in the boiler, with anaerobic combustion leading to an increase in the content of these gases and causing corrosion to the water-cooled wall.

The photonic integrated interferometric imaging system generally adds single-mode fiber arrays at the focal plane of the subaperture, and completes the large-field-of-view splicing imaging by receiving beams with different field-of-view angles, but the direct use of fiber arrays leads to the discontinuity of the imaging field-of-view, the focal length of the subaperture becomes longer, and the thickness is increased substantially. To address the above problems, this paper proposes a combination of microlens arrays and fiber optic arrays to subdivide the subaperture image plane to achieve a seamless splicing of the field of view, and through the combination of the telephoto objective lens and the three-lens spatial compression plate significantly reduces the overall thickness of the subaperture array. The design results show that by adding 65*65 microlens array in front of the fiber array to focus the beam twice to achieve the system field of view seamless splicing, the field of view is expanded 65 times, the full field of view is 0.0489 °, the efficiency of spatial optical coupling in the center of each fiber in the single-mode fiber array is not less than 40% when the visible light is incident, and after adding the spatial compression plate to compress the free-space light path, the overall thickness of the system achieves one order of magnitude compression. The system in the realization of photonic integrated interference imaging system large field of view seamless splicing imaging at the same time, for the solution of the problem of ultra-long focal length lens thickness is too large to provide a new way of thinking.

Laser communication utilizes light waves as the transmission medium. It offers many advantages, including high data rates, expansive bandwidth, compactness, robust interference resistance, and superior confidentiality. It has the critical capability to enable high-speed transmission and secure operation of space information networks. Prominent research institutions have committed to studying a series of challenges that need to be solved in the process of networking laser communication technology, including point-to-multipoint simultaneous laser communication, all-optical switching and forwarding of multi-channel signals within nodes, node dynamic random access, and network topology design. Numerous demonstration and verification experiments have been conducted, with a subset of these research results finding practical applications. Based on the analysis and discussion of space laser communication networking technology, this paper summarizes the development of laser communication networking technology both domestically and internationally, focusing on the application of laser communication networking technology in the fields of satellite constellations, satellite relays, and aviation networks; furthermore, it presents a review of pertinent domestic research methodologies, experimental validations, and technical solutions; finally, it predicts the development trend of laser communication networking technology and applications.

To address the issues of blurred edge details and poor contrast in multi-scale transform fused images obtained using remote sensing detection methods for mixed background features, an image fusion approach that combines the sparse representation of non-downsampled contour wavelet transform and a guided filter was utilised to enhance the quality and visual appearance of the fused images. This method involved several steps: Firstly, a multi-scale and multi-directional decomposition was performed on both spectral and polarimetric images using non-downsampled contour wavelet transform to isolate the feature information in each subband; secondly, the low-frequency subbands were fused using a sparse representation approach to minimize the loss of contrast in the fused image; additionally, the high-frequency subbands were fused through a bootstrap filter to enhance the detail information and the contours of the image; finally, the low-frequency and high-frequency fusion coefficients were inverted using non-downsampled contour wavelet inversion to generate the final fused image. Analysis indicates that this method has increased the contrast of the fused image by up to 54.5% relative to the original spectral image and by 15.4% compared to the polarimetric image. This has resulted in a fused image in which it is easier to distinguish objects in shadows within a mixed background. This method was used to fuse spectral and polarimetric images captured by a polarimetric spectral imager at different wavelengths, which resulted in true-colour reproduction. These true-colour restored images demonstrate that this fusion method retains environmental information within the mixed background while distinguishing the object from the background, effectively improving the image quality of polarization spectral remote sensing detection imaging. This approach enhances the integrity and authenticity of image information in polarization spectral remote sensing detection imaging, thereby expanding its application scope in remote sensing detection of complex environments and image recognition.

With the rapid advancement of spectral imaging technology, the use of multispectral filter array (MSFA) to collect the spatial and spectral information of multispectral images has become a research hotspot. The uses of the original data are limited because of its low sampling rate and strong spectral inter-correlation for reconstruction. Therefore, this paper proposes a multi-branch attention residual network model for spatial-spectral association based on an 8-band 4 × 4 MSFA with all-pass bands. First, the multi-branch model was used to learn the image features after interpolation in each band; second, the feature information of the eight bands and the all-pass band were united by the spatial channel attention model designed in this paper, and the application of multi-layer convolution and the convolutional attention module and the use of residual compensation effectively compensated the color difference of each band and enriched the edge texture-related feature information; finally, the preliminary interpolated full-pass band and the rest of the band feature information were used in feature learning by residual dense blocks without batch normalization on the spatial and spectral correlation of multispectral images to match the spectral information of each band. Experimental results show that the peak signal-to-noise ratio, structural similarity, and spectral angular similarity of the test image under the D65 light source outperform the state-of-the-art deep learning method by 3.46%, 0.27%, and 6%, respectively; in conclusion, this method not only reduces artifacts but also obtains more texture details.

The Terahertz wave possesses characteristics of high penetration, low energy, and fingerprint spectrum, etc., making it widely used in the detection field. Therefore, developing a Terahertz wave detection optical imaging system holds substantial significance and wide application prospects. Firstly, we refer to the structure of Tessar objective lens, which consists four lenses. The balance equations of aberration for the system were established through the application of the aberration theory of the paraxial optical system. Subsequently, we provide a solution function and method of the initial structure parameters of the system. Then, we combine it with optical design software to further correct the aberration of the system. Finally, we design a Terahertz wave detection optical imaging system with a large aperture. The optical system consists of four coaxial refractive lenses with a total focal length of 70 mm, an F-number of 1.4, and a full field of view angle of 8°. The value of modulation transfer function (MTF) in the range of full field of view angle is greater than 0.32 at the Nyquist frequency of 10 lp/mm, and the root mean square (RMS) radius of the diffused spot in each field of view is less than the airy disk radius. Finally, the paper analyzes and discusses the various tolerance types of the system. The results indicate that the Terahertz wave detection optical imaging system, designed in this paper, has a large aperture, a simple, compact form, a lightweight structure, excellent imaging performance and simple processing, which meets the design requirements, and it has important applications in the field of high-resolution detection and other fields within the Terahertz wave band.