In order to realize the rapid, high-precision, and universal testing of concave aspheres, a non-null interferometry is proposed in this paper, which takes the asphere as a sphere and measures it directly with an interferometer. Combined with the corresponding data processing methods, the test results of the aspheric are obtained. Firstly, the detection theory of this method is introduced, the calculation and removal models of retrace error and adjustment error are established, and the data processing method of shape error is studied. Secondly, taking two concave aspherical surfaces with different parameters as an example, the retrace error and adjustment error are simulated, which verified the effectiveness of the method. Finally, a non-null interferometric experimental setup of concave aspheric surface is performed, and its shape error is successfully obtained. By comparing the results with autocollimation method and LUPHOScan method, it is found that the surface distribution and evaluation indicators of the results are highly consistent, which verifies the correctness of this method. This method provides an effective measurement method for concave aspheric surface with high precision, universality, and convenience.

A temperature control system that employs an incremental PID algorithm based on FPGA technology has been developed to decrease detector noise and dark current while ensure the CMOS detector of the spectrometer obtain more accorate spectrum curve. Considering the current temperature and the control parameters, the appropriate control quantity is calculated to ensure the detector realize the target temperature. Controlling the temperature change rate of the detector is realized through front stage control, effectively solving the problem of overshooting. By adding the anti-integral saturation algorithm and the transition link of the target value, the function of the temperature change rate of the detector is controllable, and the problem of overshoot is solved. Multiple environmental tests conducted on the entire machine indicate that the system can control the temperature of the detector to reach any desired temperature within a specified temperature difference range of 40 °C at room temperature. The sensor temperature has a margin of error of ±0.1 °C. Compared to the conventional analog PID control method, the proposed method offers significant advantages of high sensitivity and strong stability. At a temperature of −10 °C, the noise of the detector is substantially reduced.

Cytoendoscopy requires continuous amplification with a maximum magnification rate of about 500 times. Due to optical fiber illumination and stray light, the image has non-uniform illumination that changes with the magnification rate, which affects the observation and judgement of lesions by doctors. Therefore, we propose an image non-uniform illumination correction algorithm based on the illumination model of cytoendoscopy. According to the principle that image information is composed of illumination and reflection components, the algorithm obtains the illumination component of the image through a convolutional neural network, and realizes non-uniform illumination correction based on the two-dimensional Gamma function. Experiments show that the average gradient of the illumination channel and the discrete entropy of the image are 0.22 and 7.89, respectively, after the non-uniform illumination correction by the proposed method, which is superior to the traditional methods such as adaptive histogram equalization, homophobic filtering, single-scale Retinex and the WSI-FCN algorithm based on deep learning.

In this paper, an XNOR gate and NAND gate structure, utilizing a two-dimensional photonic crystal with a line defect and linear interference effect alongside waveguide coupling, has been designed. The band structure of the photonic crystal has been analyzed using the plane wave expansion method. The finite-difference time-domain method and the linear interference effect are used to simulate the stable electric field diagram and the normalized power of the XNOR gate and NAND gates on the Rsoft platform. The simulation results demonstrate that the XNOR gate that was designed possessed a contrast of 29.5 dB, a response time of 0.073 ps, and a data transmission rate of 13.7 Tbit/s. On the other hand, the designed NAND gate has a contrast of up to 24.15 dB, a response time of 0.08 ps, and a data transmission rate of 12.5 Tbit/s. With these parameters, the designed structure showcases a high contrast, short response time, and fast data transmission rate.

A theoretical analysis was conducted on the effect of stimulated Brillouin scattering on the laser output performance in a 2 µm thulium-doped fiber amplifier. The study examined the optical mode distribution, effective refractive index, effective mode field area, and normalized frequency of the double-clad thulium-doped fiber at 793 nm pump wavelength and 1.9−2.1 µm laser waveband. The stimulated Brillouin scattering characteristics, including the Brillouin frequency shift and the Brillouin gain spectrum, in the double-clad thulium-doped fiber were numerically simulated in the laser waveband of 1.9−2.1 µm. The influence of stimulated Brillouin scattering on the laser output performance of thulium-doped fiber amplifiers was investigated using the theoretical model of stimulated Brillouin scattering in gain fibers. In the DTDF-10/130 double-clad thulium-doped fiber, a 100W continuous wave with a wavelength of 793 nm is used as a pump to amplify a continuous signal wave that has a wavelength of 2 µm and carries a power of 0.01 W. The maximum output powers of the signal wave are 25.27 W, 31.08 W and 34.06 W for pump power filling factors are 0.01, 0.02 and 0.03, respectively. The corresponding optimal lengths for the double-clad fiber lengths are 2.66 m, 2.02 m and 1.75 m. Additionally, the stimulated Brillouin scattering generates a Stokes optical power of 1.68 W, 1.39 W and 1.14 W, respectively. It is evident from the results that the double-clad fiber with large pump power filling factor in the thulium-doped fiber amplifier can effectively reduce the fiber length, thus to minimizing the influence of stimulated Brillouin scattering on the output power of the signal laser. The numerical model can optimize the fiber length of the fiber amplifier, which is of great significance to improve experimental efficiency and reduce experimental costs.

Red lasers with a picosecond pulse width are widely used in various fields such as industrial, medical, scientific research and information industries due to their narrow pulse width and high peak power. This paper presents an all-solid-state laser, operating at 660 nm with picosecond pulse width, narrow band, and high conversion efficiency, which is demonstrated by the Acousto-Optic Mode-Locked (AOML) method. By carefully optimizing the cavity and implementing external frequency doubling with two LiB₃O₅ (LBO) crystals along with various techniques, we have successfully developed a mode-locked red laser source with a maximum output power of 8.6 W. The laser operates in a pulsed side-pumped regime and consists of a number of mode-locked pulses with a frequency of 100 MHz and a pulse width of 887 ps. The optical-to-optical conversion efficiency from 1319 nm to 660 nm can reach up to 41%.

In order to shorten the axial and radial dimensions of the 12-inch wafer detection imaging system, a solution combining the small Angle prism refraction path and the ultra-short object-image distance lens is proposed. A small Angle prism with better shape accuracy than 1/12λ (λ=632.8 nm) is designed to convert the optical path and realize the horizontal arrangement between the lighting system and the imaging lens. The radial size is only 80 mm, which greatly reduces the radial size of the whole system without affecting the imaging quality. At the same time, a small angle of 12° bright field lighting is realized. A symmetrical hybrid optical system with magnification of 0.264 is designed. A pure spherical system is used to obtain a large imaging field of view. The image height is 81.92 mm, and the object image distance is only 392.5 mm, which greatly reduces the axial size of the whole system. The design results show that the average optical transfer function of the whole imaging system is better than 0.4@100l p/mm, the relative distortion is better than 0.03%, and the uniformity of the image surface illuminance is better than 50%. The actual test results show that the actual imaging resolution is better than 18.88 μm, which reaches the ultimate resolution of the system. The uniformity of illumination of image surface is 43.3%, which meets the development requirement of uniformity better than 40%. The research results show that the ultra-thin and ultra-short object-image distance imaging system is reasonable and effective, which solves the problem of space size compression of the 12-inch wafer detection imaging system and reduces the development cost. It provides a reference for the development of the imaging system for detecting large objects in short distance.

Narrow linewidth fiber lasers, which are based on an oscillator seed source with multiple longitudinal-mode, offer substantial advantages for engineering applications and space-limited platform payloads. Additionally, they are considered ideal sub-modules for high-power spectral combinations. The time domain of this type of seed is unstable due to the self-pulse effect, causing significant spectral broadening and stimulated Raman scattering effects during the amplification process. These effects limit the further improvement in output power and affect the purity of laser spectra. This paper introduces four commonly used narrow linewidth seeds. The mechanism and suppression methods of the self-pulse effect in multi-longitudinal mode oscillator seeds were analyzed. Critical technologies essential for the optimization and relevant progress of the multi-longitudinal-mode oscillator seed source and amplifier stages are discussed in detail. A future development outlook is also presented. This paper serves as a useful reference for the design of narrow linewidth fiber lasers based on the multi-longitudinal-mode oscillator seed source.

Laser Induced Breakdown Spectroscopy (LIBS) is a new method for qualitative and quantitative analysis of the constituents of a material using plasma spectra produced by the interaction of a strong pulsed laser with the material. In the process of pulsed laser-induced plasma, different laser parameters (energy, pulse width, wavelength), environmental conditions during the detection process and the properties of the material itself have different degrees of influence on the physical mechanism of laser-induced plasma, which in turn affects the results of LIBS quantitative analysis. We review the physical mechanisms of LIBS technology in the current state, including the basic principles of LIBS, the differences in laser parameters, and the physical mechanisms involved in the differences in environmental and material properties. It provides a basis for a deeper understanding of laser-matter interactions and for improving the detection capabilities of LIBS.

In response to the demand for high imaging quality and high chromaticity in color digital cameras, this paper investigates the optical system design and camera spectral optimization methods of 3CMOS cameras based on Philips prisms. By modeling the optical path of the Philips prism, the structural parameters of the prism were optimized, reducing the volume of the system while ensuring total internal reflection and exit window size. Based on this method, the Philips prism 3CMOS camera optical system was designed, with a field of view angle of 45 ° and a relative aperture of 1/2.8. The system's MTF was greater than 0.4 in the full field of view and full band at Nyquist sampling frequency of 110 lp/mm. Subsequently, based on the fundamental principles of chromaticity, a vector imaging model for Philips prism cameras was established. The problem of thin film spectral shift caused by changes in light incidence angle was analyzed, and a correction model for spectral shift under wide beam conditions was proposed. Four sets of optical thin films in the camera were designed and optimized using this model. Through optical path simulation experiments and color error analysis, based on the optimized camera spectrum, the average color error of the system was reduced by 15.8%, and the color non-uniformity of the image plane was reduced by 60%. The results indicate that the optical system designed in this article has good imaging quality, and the optimized camera spectrum achieves good color performance and uniformity.

To address weak gas laser telemetry optical signals and strong interference from environmental factors, a Highly Sensitive Photoelectric Detection Circuit (HSPDC) for TDLAS laser telemetry has been designed and investigated using wavelength modulation technology. In addition, Furthermore, a noise suppression method for TDLAS signals based on this technology was determined. The photodiode ideal model is utilized to analyze the linear response characteristics of the photodetector circuit and determine the essential photodiode parameters. Based on the cascade amplification principle, the HSPDC is designed, simulated, and tested, achieving a lower limit of optical power detection of 0.11 nW, a signal attenuation of 0.79 dB (f=10 kHz). The cutoff frequency is one order of magnitude higher than the existing 108 V/A cross-impedance amplification circuit. Therefore, HSPDC is applicable for high-speed modulation of weak optical signals. The laser telemetry system exhibits excellent detection performance at a modulation frequency of 3 kHz, with a detection sensitivity of 88.66 mV/ppm, a detection limit of less than 0.565 ppm, and a linear fit R² of 0.9996. The study demonstrates that the HSPDC photoelectric detection circuit offers the advantages of fast response, high detection sensitivity and accuracy, rendering it ideal for gas laser telemetry applications.

Trace gases, as important constituents of the atmosphere, play an important role in the ecology of the planet. In order to realize the requirements of all-weather continuous measurement, wide-band and hyperspectral detection, a hyperspectral imaging spectrometer operating in occultation detection mode is designed in this paper. The system is a dual-channel structure with a common slit, the UV-visible channel adopts a single concave grating, and the infrared channel adopts a structure combining Littrow and immersion grating, which effectively reduces the volume. The software was used to optimize the optical structure, and the optimization results showed that the spectrometer operated in the range of 250-952 nm wavelengths, of which the UV-visible channel operated in the wavelength range of 250-675 nm, the spectral resolution was better than 1 nm, the MTFs were all higher than 0.58 at a Nyquist frequency of 20 lp/mm, and the RMS values at various wavelengths of the full-field-of-view were all less than 21 μm; The infrared channel operates in the wavelength band of 756-952 nm, the spectral resolution is better than 0.2 nm, the MTF is higher than 0.76 at the Nyquist frequency of 20 lp/mm, and the RMS value at each wavelength in the whole field of view is less than 6 μm , all of them meet the design requirements, and this hyperspectral imaging spectrometer system can realize occultation detection of trace gases . It can be seen that the hyperspectral imaging spectrometer system can realize the occultation detection of trace gases.

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.

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 developed a Modulation Transfer Function (MTF) calculation model under the influence of ghost images generated by secondary reflection. This paper first introduces 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, a calculation model for calculating the MTF under the influence of ghost images is constructed. After performing calculations and comparing them to simulation results, it was found that the maximum mean square error was less than 0.049373, which verifies the accuracy of the model. Furthermore, a detailed analysis was 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.

Liquid crystal wavefront correctors (LCWFCs) have the high development cost and customization difficulty as they are usually fabricated based on the process technology of liquid crystal displays. In the paper, to achieve specialized and low-cost development of LCWFCs, it is fabricated with the mask lithography method. Firstly, a 91 pixels passive liquid crystal driving electrode was designed and prepared based on mask lithography technology and then, packaged as a liquid crystal optical correction unit. Then, a driver connection circuit board was designed and prepared to connect the optical correction unit and the driving circuit board. Next, the response characteristics of the LCWFC were tested, and the results show that the phase modulation is 5.5λ, and the response time is 224 ms. Finally, the spherical waves are generated and the static tilt aberrations are corrected based on Zygo interferometer. The results show that the LCWFC can generate positive and negative defocused wavefronts. Further, after correction of the horizontal tilt aberration, the coefficient of the first term of the Zernike polynomials is decreased from 1.18 to 0.16. Therefore, the aberration is corrected with the amplitude of 86%. This work may provide new ideas for the development of LCWFCs, and then expanding their application fields and scenarios.

To improve both the efficiency and accuracy of point cloud registration, this study proposed an improved method based on point-by-point advance feature point extraction. Firstly, the point-by-point advance method extracts point cloud feature points rapidly, and greatly reduces the number of point clouds, while retaining the characteristics of the point cloud model. The KN-4PCS algorithm, using normal vector constraints, conducts a preliminary registration of the source and target point cloud. Finally, the fine registration is achieved with the two-way Kd-tree optimized LM-ICP algorithm. In the open point cloud data registration experiment of Stanford University, the average error is reduced by about 70.2% compared with the SAC-IA+ICP algorithm, and the registration time is reduced by about 86.2% and 81.9%, respectively. The algorithm maintains high accuracy and low time consumption even with varying degrees of Gaussian noise. In the point cloud registration experiment of indoor objects, the average registration error was measured to be 0.0742 mm with an average algorithm time of 0.572 s. The comparison and analysis of Stanford open data and real indoor scene object point cloud data shows that this method can effectively improve the efficiency, accuracy, and robustness of point cloud registration. Furthermore, this study establishes a strong foundation for indoor target recognition and pose estimation through the point cloud.

A method for correcting XY defocus aberrations, based on Hartmann-Shack wavefront sensor and two-dimensional beam-shaping light path, was presented due to the large percentage of defocus and 0° astigmatism aberrations with large PV values in high-energy laser beam. The first step is to derive an expression for XY defocus aberrations by linearly combining the defocus and 0° astigmatism terms of Zernike polynomials. The coefficients directly characterize the wavefront peak-to-valley (PV) values of X and Y defocus. At the same time, compensation for XY defocus wavefronts of the laser beam can be achieved by fine-tuning the mirror spacing in the two-dimensional shaping optics of the high-energy laser. Therefore, this study utilizes the Hartmann wavefront sensor to extract the coefficients of XY defocus aberrations from the laser beam. The computer dynamically adjusts the mirror spacing in the two-dimensional shaping optics based on these coefficient values to correct XY defocus aberrations and improve the beam quality of the output laser beam. The results of the experiment showcase a significant decrease in XY defocus aberrations from 5.2 μm and 1.1 μm to less than 0.5 μm, as well as a decrease in β factor from 3.1 to 1.8, resulting in substantial improvement in beam quality.

3D reconstruction is crucial for digitizing artifacts, and the accuracy of 3D point cloud registration is a significant metric for evaluating the reconstruction quality. In practice, artifact point cloud data includes numerous details, and using conventional downsampling methods may result in the loss of such details, thereby affecting registration accuracy. This paper proposes a method for downsampling and registering artifacts point clouds based on curvature features. First, 3D point clouds data of artifacts are obtained using linear matrix laser measurement. Next, the curvature values of all points are calculated, and a curvature threshold is set for point cloud classification. We downsample different point sets based on their feature attributes, with varying weights assigned to retain the shape features and details of the point cloud as much as possible. Finally, point cloud registration is achieved through the use of a rigid transformation model. Compared to the traditional global downsampling ICP method, the downsampling processing before point cloud registration reduces the point cloud data to 1/3 of the original size. The average distance decreases from approximately 0.89 mm to 0.59 mm, while the standard deviation decreases from about 0.29 mm to 0.18 mm. This approach guarantees the accuracy of downsampling and registration and is applicable to various artifacts point cloud data.

To address the issue of non-linear distortion in the Phase Generated Carrier (PGC) demodulation algorithm, we have developed an extrinsic Fabry-Perot Interferometer (EFPI) sensor demodulation system that is based on an improved PGC-Atan algorithm. The theoretical analysis focuses on the nonlinear factors affecting sine and cosine signals used in arctangent operation of the PGC-Atan algorithm. Such factors include deviations from optimal values of the phase modulation depth (C), companion amplitude modulation, and carrier phase delay. As a solution, we propose an improved PGC-Atan algorithm based on a correction coefficient (PGC-CC-Atan) suitable for external modulation or the case of low companion amplitude modulation scenarios. The PGC-CC-Atan algorithm generates a coefficient relating to C and carrier phase delay while excluding nonlinear parameters in the arctangent operation. Furthermore, an improved PGC-Atan algorithm that utilizes an elliptic fitting algorithm (PGC-EF-Atan) is proposed for internal modulation. The ellipse fitting technique is employed to fit the eclipse using the least squares method based on a matrix block decomposition. The pair of signals that are influenced by nonlinear factors are corrected and transformed into orthogonal signals utilizing three parameters of the ellipse. Finally, the correctness of the two improved algorithms is verified through simulations and experiments. The PGC demodulation system comprises a high dv/di VCSEL laser and a conventional cavity length F-P sensor. By comparing the demodulation performance of the PGC-Atan algorithm with that of the two improved algorithms, their effectiveness in suppressing nonlinear distortion is verified. Experimental results indicate that the two improved algorithms exhibit effective demodulation in the presence of nonlinear factors within a specific range of C values. The signal-to-noise and distortion ratio (SINAD) of demodulation result obtained from PGC-EF-Atan algorithm surpasses that of the PGC-CC-Atan algorithm by 11.602 dB, while the THD is reduced by 10.951%. Between the two improved algorithms, the PGC-EF-Atan algorithm possesses superior demodulation linearity, accuracy, and nonlinear distortion suppression performance.

To address the problem of limited field of view measurement in traditional monocular vision measurement systems, this paper proposes an omnidirectional spatial monocular vision measurement method based on a two-degree-of-freedom rotary table. First, calibrate the rotating axis parameters of the double-degree-of-freedom rotary table. Then, take pictures of the checkerboard calibration plate fixed with the two-degree-of-freedom rotary table using an auxiliary camera. Extract the position coordinates of the checkerboard corner points and convert them to the same camera coordinate system. The direction vector of the initial position axis parameter was obtained through PCA (principal component analysis) plane fitting, and the position parameter in the rotation axis parameter in the initial position was determined using the method of spatial least squares circle fitting. The camera data acquired at various angles is transformed into coordinate system one using the rotary table rotation angle and the Rodrigues formula. This enables measurement of the target in the horizontal and vertical omnidirectional space. Finally, verification of the measurement accuracy of the proposed method was conducted using a high-precision laser rangefinder. Additionally, experiments comparing the omnidirectional spatial measurement ability of the method with the binocular vision measurement system and wMPS measurement system were conducted. The results indicate that the method achieves a measurement accuracy comparable to that of a binocular vision system. However, it also surpasses the binocular vision system in term of measurement range, making it applicable for omnidirectional spatial measurements.

To improve the accuracy of palm surface reconstruction in flexible robot grasp sensing, this study conducts a COMSOL simulation to select a ring arrangement comprising of 7 fiber Bragg grating (FBG) flexible sensors packaged with polydimethylsiloxane (PDMS) on a 436 mm×436 mm×2 mm polypropylene plate. Assuming that the center and two corner ends of the plate were subjected to stress, respectively, we collected sensor data using a fiber grating demodulation instrument during the experiment. The data was continuously interpolated using cubic spline interpolation. Several planes Y intersected with the fitting ring which created a three-dimensional surface. We calculated the point function to obtain the point set and achieve a fitting visual display of the spatial surface. The plate experienced a minimum relative error of 0.549% in end displacement, with a maximum relative error of 8.300%. the center of the surface’s end yielded a minimum absolute error of 0.051 cm, and a maximum absolute error of 1.255 cm. When both corners at the end of the plate are under stress, a minimum relative error of 2.546%, and a maximum relative error of 14.289% arise in plate reconstruction end displacement. The minimum absolute error is 0.005 cm, and the maximum absolute error is 0.729 cm. These experimental results provide a foundation to implement palm grip sensing in flexible robots.

The existing multi-band imaging system poses issues of large volume, high power consumption, and difficulty in integrating design. To address these challenges, we proposed a solution in the form of a design methodology for a single sensor based three-band co-aperture imaging optical system. First, a 1×2 multi-band lens array in the aperture stop of the optical system is designed. This array effectively captures both the visible and short-wave infrared bands simultaneously in a single image plane. In addition, the imaging position deviation of the center wavelength of both bands are controlled to within one pixel, resulting in dual-band fusion imaging. To address the issue of different diffraction limits in multi-band imaging, we propose to use the joint optimization method to simultaneously control the off-axis offset and aperture size of the split channel lens array. In addition, we suggest utilizing a dual electric diaphragm to control the switching speed of the three imaging channels. Finally, a single sensor based three-band co-aperture optical system with a focal length of 30 mm and operating bands ranging from 480 to 900 nm, from 900 to 1700 nm, and from 480 to 1700 nm is designed. The system exhibits multiple advantages, such as excellent imaging quality, a compact structure, no moving optical elements, and a rapid switching speed of the imaging band, as indicated by the design and analysis results.

The aim of this study is to address the issue of degraded image quality in photoacoustic tomography (PAT) caused by the inhomogeneous light fluence, complex optical and acoustic properties of biological tissues, and non-ideal properties of ultrasonic detectors. This paper proposes a model-based method for reconstructing PAT images. A comprehensive forward imaging model is proposed to describe the physical process of imaging in non-ideal scenarios. The model takes into account variables such as the heterogeneity of light fluence, unsteady speed of sound, spatial and electrical impulse responses of ultrasonic transducers, limited-view scanning, and sparse sampling. The inverse problem of the imaging model is solved by alternate optimization, and images representing optical absorption and SoS distributions are reconstructed simultaneously. The study outcomes indicate that utilizing this method for image reconstruction enhances the structural similarity of the reconstructed images by about 83%, 56%, and 22%, in comparison with back projection, time-reversal, and short-lag spatial coherence techniques, respectively. Additionally, the peak signal-to-noise ratio can be improved by approximately 80%, 68% and 58%, respectively. This method considerably enhances the image quality of non-ideal imaging scenarios when compared to traditional techniques.

To develop a highly sensitive seawater salinity sensor, a long period fiber grating (LPFG) was successfully fabricated using CO₂ laser technology to function in close proximity to the dispersion turning point (DTP). An LPFG operating near DTP was fabricated in an 80 μm single mode fiber using CO₂ laser micromachining technology. This successful endeavor demonstrates the feasibility of developing LPFG with shorter grating period. LPFGs with varying periods were fabricated using a CO₂ laser to ensure that the cladding mode LP_1,9 was operating near DTP, resulting in higher refractive index sensitivity of LPFG. The average sensitivity of 0.279 nm/‰ can be achieved in the seawater with salinity ranging from 5.001 ‰ to 39.996 ‰, especially with the dual peak resonance LPFG at a period of 115.4 μm, thanks to the dual peak resonance effect. The dual peaks resonance LPFG seawater salinity sensor exhibits high sensitivity and a large attenuation loss, suggesting potential application in seawater salinity monitoring.

This study analyses the optical requirements of wide beam and high uniformity light beads, which are currently used in displays. Packaging micro light-emitting diode (LED) chips with a novel non-Lambertian distribution has facilitated the production of micro-LED chip light beads that are wide in beam and high in uniformity. The light output efficiency and beam angle of fixed beads were simulated using brackets made of copper, titanium, aluminium and silver, as well as materials that were completely reflecting and absorbing. The simulations were conducted at various fixture angles, packaging heights, sapphire thicknesses, and patterned sapphire substrate sizes. By adjusting the chip and packaging parameters, we can obtain one, two, or three light beams with SMD lamp beads characteristics that provide wide angles, high uniformity, and far-field light distribution. These characteristics can meet the current display requirements for LED and LCD.

In order to improve the visible light band (0.3 μm~0.9 μm) A simplified method for high-temperature calibration in the visible light band has been proposed to improve the efficiency of high-temperature calibration. First of all, a high-temperature calibration model of visible light band with exposure time variable is proposed. Through a large number of experimental data, it is found that the gray value of each channel of RGB camera not only changes linearly with the increase of exposure time, but also changes linearly with the increase of Black-body radiation brightness. Then, the specific form of high-temperature calibration model of visible light band is determined. Then, in order to solve the unknowns in the simplified high-temperature calibration model of visible light band, image data under two exposure times are collected under two Black-body radiation brightness, and then the image data is processed to obtain the high-temperature calibration curve of RGB camera under any exposure time. Finally, a comparison is made between the simplified visible light band high-temperature calibration method proposed in this article and the conventional visible light band high-temperature calibration method based on exposure time. The experimental results show that the maximum relative error between the calculated value of the R channel and the calibrated value is 3.38%, the maximum relative error between the calculated value of the G channel and the calibrated value is 2.56%, and the maximum relative error between the calculated value of the B channel and the calibrated value is −1.14%. Moreover, the relative error between the calculated value of each channel and the calibrated value does not exceed 3.50%. The mathematical model proposed in this article can effectively simplify the traditional high-temperature calibration method, thereby greatly shortening the high-temperature calibration time and improving the calibration efficiency of high-temperature calibration.

Compared with a single vortex beam, vortex array beams can expand the transmission capacity of information, and the study of their propagation properties is of great significance for their optical communication applications. In this paper, we select the helical Ince-Gaussian (HIG_n,n) modes of order n and use the power spectrum of the refractive index fluctuations in the marine atmosphere to simulate the turbulence of the marine atmosphere. The changes of intensity, phase, scintillation index and spot centroid wander of a one-dimensional array vortex beam in marine atmospheric turbulence have been investigated systematically by using the phase screen method. We find that (1) when either the turbulence intensity or atmospheric turbulence inner scale is increased, both the scintillation index and spot centroid wander standard deviation of HIG_n,n modes are enhanced; (2) the scintillation index of HIG_n,n mode with odd n decreases with increasing mode order, and is higher than that of HIG_n,n mode with even n; (3) the HIG_n,n mode with order n>1 has better stability than the LG_0,1 mode; and (4) the higher the mode order, the smaller the standard deviation of spot centroid wander of HIG_n,n mode. In addition, we have also comparatively studied the propagation performance of the linear array vortex beams (LAVBs) and HIG beams, and found that even though LAVBs have better propagation performance than HIG beams, the unique structures of HIG beams can be applied to different application scenarios. Finally, the effects of ellipticity parameter and elliptic ring number on the propagation of the HIG modes are explored and analyzed. The results show that increasing the ellipticity parameter or elliptic ring number is beneficial to improving the anti-turbulence ability of the HIG modes. The research results obtained in this paper are of guiding significance for the offshore application of vortex beams.

Small size parts have a small surface area and complex structure. The traditional mark splicing method needs to manually paste marks on the surface of parts, resulting in missing the measurement data of the surface and becoming holes. The feature splicing method requires the surface of parts to have easily distinguishable geometric or distance features, which are not suitable for rotating parts containing repetitive features. We propose a scanning measurement method without marks based on mechanical splicing, which does not need to paste marks or depend on the surface features of parts. First, the camera calibration method based on photogrammetry is used to reconstruct the high precision 3D coordinates of the target on the calibration board. By tracking the position of the encoded target, the rotation matrix corresponding to different angles of the turntable is established, and the direction vector of the rotation axis and the fixed point coordinates on the axis are solved. Then the synchronous calibration of the rotation axis and the camera is completed. Second, based on the accurate calibration of poses of two rotation axes, the rotation mosaic matrix is constructed by using the turntable angle to realize the rough registration of multi-view point clouds. Finally, based on the Normal Iterative Closest Point (NICP) algorithm, the fine registration of the point clouds is completed. Experimental results show that the angle error between the two rotation axes calibrated by the target tracking method is 0.023° lower than that of the traditional standard ball fitting method. After calibration, the average size error of the standard ball is less than 0.012 mm. In the automatic measurement of small-size parts, the point cloud splicing effect of the mechanical splicing method after fine registration is similar to that of the mark splicing method, and the splicing stability is higher. The mechanical splicing method is suitable for the 3D topography measurement of small-size parts where the marks cannot be pasted.

With the improvement of the spatial resolution and area array specifications of the cooled LWIR focal plane detector, the application range of the cooled LWIR thermal imager is becoming wider and wider, and the corresponding optical system needs to be improved to meet the needs of different fields. Compared with the MWIR optical zoom system, the LWIR optical zoom system has fewer available materials and is difficult to athermalize in high and low temperature environments. In this paper, the multi-field optical zoom system is realized by using mechanical compensation zoom technology, and the active compensation athermalization technology is used to make the system image clear from −40 °C to +65 °C, to realize the design of the four-field LWIR optical system with four lenses. The focal lengths of the four fields of view are 25 mm, 109 mm, 275 mm and 400mm, the zoom ratio is 15, the envelope of the optical system is 280 mm(L)×200 mm(W), and the total weight of the optical components is 618 g. The optical system has SWaP-C characteristics such as light weight, high performance, and low cost, and will be widely used in security fields such as auxiliary navigation, search, and tracking.

With the rapid development of inter-satellite communication systems, the requirements for data transmission accuracy are constantly increasing. As the core component, the spectral characteristics and surface shape accuracy of the beam splitter directly affect the transmission accuracy of the whole system. In this paper, based on the interference theory of thin film, Ta₂O₅ and SiO₂ were selected as the high and low refractive index film materials for the design of the film system, and electron beam evaporation was used to prepare a high-precision beam splitter on a quartz substrate. At the same time, a surface shape correction model was established based on the principle of film stress compensation to control the surface shape. Through the detection of a spectral analyzer, the transmittance of beam splitter is greater than 98% at 1563 nm and the reflectance is greater than 99% at 1540 nm within the incidence range of 21.5° to 23.5°. The surface shape was measured by laser interferometer, the reflective surface shape accuracy RMS is corrected from λ/10 to λ/90 (λ=632.8 nm), and the transmissive optical surface shape accuracy RMS is λ/90.

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.

Optical aberrations caused by the scattering of biological tissues limit the imaging performance of optical systems. We have explored a fluorescence confocal imaging technique that utilizes wavefront shaping indirectly, operating in the near-infrared II range. First, we synthesized a highly efficient fluorescent probe in the near-infrared II range, where reducing the scattering of biological tissue can enable high-contrast biopsy imaging. Second, the study investigate the adaptive optical method, utilizing indirect wavefront measurement. The indirect wavefront shaping technology was applied to the laser scanning confocal system, enabling the measurement and compensation of optical aberrations caused by biological tissues, and obtaining imaging of biological tissues with a high signal-to-noise ratio. Finally, an indirect wavefront shaping-based near-infrared II fluorescence confocal imaging system was deployed and relavant experiments were conducted. The experimental outcomes reveal that the system effectively compensates for the aberrations induced by air plates, scattering media and mouse skull, and increases the final signal intensity to 1.47, 1.95 and 2.85 times, respectively. As a result, the final imaging quality is significantly enhanced.

Remote sensing satellites play an crucial role in both national defense and civil exploration. However, the imaging quality of high-resolution remote sensing satellites is significantly affected by atmospheric turbulence. This paper focuses on the impact of camera aperture, satellite orbit altitude and atmospheric turbulence intensity on the imaging quality of space cameras during remote sensing satellite Earth detection. Firstly, the turbulence wavefront simulation method based on the spherical wave model and Kolmogorov turbulence theory is analyzed. Subsequently, the disturbed wavefront, impacted by the camera aperture, satellite orbit height and atmospheric turbulence intensity, is analyzed, and a universal formula is derived. In addition, an equation for imaging resolution, taking into account aperture, satellite orbit height and atmospheric coherence length, is developed. Finally, this study examines the effect of atmospheric turbulence on the modulation transfer function (MTF). The analysis focuses on the relative error of MTF concerning camera aperture, satellite orbit height and atmospheric coherence length, with reference to an MTF value of 0.15. This study provides a theoretical basis for designing, analyzing, and assessing high-resolution remote sensing satellites.

With the development of industrial manufacturing towards intelligence, precision and integration, on-machine verification of the machining process can provide timely feedback on measurement results, compensate and correct processing parameters, thereby aiding in enhancing machining accuracy and efficiency. Fringe structured light technology is a non-contact measurement method, which has developed rapidly in recent years. It has the characteristics of simple measurement principle, low costs, high measurement accuracy and easy integration, which provides a new solution for on-machine verification. However, the accuracy of structural for on-machine verification is compromised by the convoluted lighting in machining environments and metal parts’ high reflectivity, leading to inaccurate measurements. Applying high dynamic range (HDR) technology to structural light detection enables the measurement of metal parts in complex scenes and reduces the effect of high reflectivity. This paper introduces the measurement principle of structured light and summarizes the challenges of on-machine verification for HDR structured light. Subsequently, this paper provides a comprehensive review of HDR structured light technology. Based on the context of on-machine verification, the HDR technology using hardware equipment and the stripe algorithm are discussed and analyzed, respectively. Following this, different technologies are summarized according to the requirements of on-machine verification. The advantages and disadvantages of various methods are presented, and the applicability of on-machine verification is compared. Finally, the potential applications are analyzed, and the technological prospects will be proposed in combination with the research hotspots of advanced manufacturing technology and precision measurement in recent years.

In order to provide high-quality, intelligent, and healthy lighting sources, a linear dimming hybrid lighting system is constructed using three-primary-color LED light sources. An optimization method for dimming and color mixing is proposed. The light chromaticity and light intensity of the mixed light source are set by color temperature and brightness level, which makes the mixed lighting effect more in line with the demand of "human-centric lighting". In the intelligent optimization of the system, the color temperature is converted into CIE \begin{document}$ {u}'{v}' $\end{document} chromaticity coordinates, and the luminance is converted into brightness to make the optimization calculations more accurate. The system adopts the linear dimming method, effectively preventing the health and safety risks caused by light source flicker, and effectively solves the problem of large linear dimming chromaticity drift with an optimization algorithm. Experiments demonstate that the chromatic stability of the mixed light in the hybrid lighting system is maintained within the first step of the CIE \begin{document}${u}'{v}' $\end{document} chromaticity diagram between a color temperature range of 2000 K to 8000 K. Moreover, the system exhibits imperceptible color deviation over the entire range of light intensity adjustments at the corresponding color temperature. This finding also indicate that linear dimming hold a superior edge over pulse-width dimming method in keeping the optical chromaticity stable. Theoretical exploration and experimental results demonstrate that the mixed lighting system is straightforword and practical, with significant practical value.

In order to meet the requirements of the national synchrotron radiation source, the anisotropic wet-etching technology of small blazed angle monocrystalline silicon grating 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 0.5nm. This method can be applied to the fabrication of the medium wave soft X-ray band blazed grating, which can greatly reduce the difficulty and cost of fabrication while achieving high diffraction efficiency.

Phase retrieval and depth estimation are vital to three-dimensional measurement using structured light. Currently, conventional methods used for structured light analysis have limited efficiency and produce unreliable results. To enhance the reconstruction effect of structured light, this paper proposes a hybrid network for structured light phase and depth estimation based on Light Self-Limited Attention (LSLA). Specifically, a CNN-Transformer hybrid module is constructed and integrated into a U-shaped structure to harness the complementary benefits of CNN and Transformer. The network is assessed comparatively with other networks in tasks related to structured light phase estimation and depth estimation. The outcome of the experimental indicates that the suggested network achieves finer detail processing in phase and depth estimation compared to other networks. Specifically, in structured light phase anddepth estimation, its accuracy improves by 31% and 26%, respectively. Therefore, the proposed network improves the accuracy of deep neural networks in the aforementioned areas.

The high mismatch rate of the parallax discontinuity region and the repeated texture region has been a major issue affecting the measurement accuracy of binocular stereo matching. For these reasons, this paper proposes a stereo matching algorithm that utilize multi-feature fusion. Firstly, the weight of neighboring pixels is given using Gaussian weighting method, which optimizes the calculation accuracy of the Sum of Absolute Differences (SAD) algorithm. Based on the Census transformation, the binary chain code technique has been enhanced to fuse the average gray value of neighborhood pixels with the average gray value of gradient image, and then the judgment basis of the left and right image corresponding points is established, and the coding length is optimized. Secondly, an aggregation technique has been developed that combines the cross method and the improved guide filter to redistribute disparity values with the aim of minimizing error. Finally, the initial disparity is obtained by the Winner Take All (WTA) algorithm, and the final disparity results are obtained by the left-right consistency detection method, sub-pixel method, and then a stereo matching algorithm based on the multi-feature SAD Census transform is established. The experimental results show that the average error matching rate of the proposed algorithm is 4.18%, the average error of the 200−900 mm distance is less than 2%, and the maximum error of the actual 3D data measurement is 1.5%, all using the test of the Middlebury dataset. The experimental results verify the effectiveness of the proposed algorithm.

To achieve periodic closed-loop correction of multiple visible wavelength lasers, a laser beam combining system is being designed. This system involves independent monitoring and adjusting of beam pointing and position deviation. First, according to the application requirements of the system, the design indexes of the beam combining system and the overall beam combining scheme are proposed. Then, based on the overall beam combining scheme, we establish the beam control model for the beam combining system. Through numerical simulation experiments, we obtain the solution method for beam control of the beam combining system. The closed-loop beam combining system enables independent monitoring of the unit beam’s pointing and position deviation through the respective beam pointing and position monitoring device. The monitoring results are then used to calculate the control quantity of the beam adjusting device. The independent and efficient adjustment of beam pointing, and position deviation is achieved using a two-dimensional swing mirror and a one-dimensional platform, respectively. Finally, a closed-loop beam combining simulation experimental system with beam monitoring and adjustment device was built using tow laser beams of different wavelengths. The periodic closed-loop beam combining system was verified to have an effective beam combing effect. The experimental results demonstrate that over an extended operational period, both lasers achieve precise beam combining with the reference optical path. Furthermore, the beam combining pointing accuracy is better than ±7μrad, and the positioning accuracy is better than ±0.84 mm. The laser beam combining system developed in this study boast high beam combining accuracy, a fast correction speed, and excellent augmentability for multiple laser beams. Besides, it can accomplish periodic closed-loop beam combining of laser beams, ensuring long-term working stability of the combined laser.

Time of Flight (ToF) depth camera is one of the important means to obtain three-dimensional point cloud data, but ToF depth camera is limited by its own hardware and external environment, and its measurement data has certain errors. Aiming at the unsystematic error of ToF depth camera, this paper experimentally verifies that the color, distance, and relative motion of the measured target affect the data obtained by the depth camera, and the error effects are different. Based on the oscillation error and the fact that each signal can be expressed in the form of a Fourier series, a new measurement error model is proposed to correct the error caused by color and distance. For the error caused by relative motion, a three-dimensional motion blur function is established to recover it. Through the numerical analysis of the established calibration model, the residual error of distance and color is less than 4mm, and the error caused by relative motion is less than 0.7mm. The work done in this paper improves the quality of the measurement data of the ToF depth camera, and provides more accurate data support for 3D point cloud reconstruction and other work.

Shearography is a non-contact, full-field, and high-precision optical deformation measurement technology. There is a lot of random noise in the acquired speckle fringe pattern caused by environmental factors, which affects the measurement accuracy. The traditional denoising methods easily cause the fringe information to be lost or even damaged while filtering out the noise. To solve this problem, this paper proposes an image denoising method based on the combination of sine and cosine transform and bitonic filtering. In this method, the phase fringe image is firstly obtained by sine and cosine transform. Secondly, the two images are denoised by the bitonic filtering method respectively. Finally, the filtered two images are merged into the final phase fringe image. Experimental results show that for the filtered phase pattern, the speckle suppression index is 0.999 and the average retention index is 2.995, which prove that the proposed method can improve the quality of the phase pattern better than the traditional denoising method, and can preserve the details and edge information of the phase fringes to a large extent.

The development of smart cars puts forward higher requirements for intelligent light systems with projection functions. Compared with the vehicle light system using traditional technology, the vehicle light system using Micro LED projection display technology can make the system structure simpler and the light utilization rate higher, which is more conducive to miniaturization, energy saving and integration because of its good self-luminous characteristics. In this paper, we propose a light projection scheme based on Micro LED array, design a 200×150 white Micro LED array with a pixel size of 80 μm×80 μm as the display light source and the field of view angle is 16°×34° object image tilt, and optimize the tilt angle and optical system structure of the object surface. In addition, the reverse distortion processing method and the pixel grayscale modulation method are used to solve the problems of keystone distortion and illumination uniformity of the projected image of the vehicle light, and a projection experimental platform is built to verify the image correction method. The experimental results show that the keystone distortion coefficients of the corrected images in the x and y directions decrease from 0.0932 and 0.3680 to 0.0835 and 0.0373, respectively, and the uniformity of the illumination of the image surface increases from 83.2% to 93.2%. In this paper, the optimization design of the oblique projection vehicle lighting system based on Micro LED and its image correction method are used to realize the projection of the vehicle light with high luminous efficiency and low distortion.

With the increasingly crowded space resources in low orbit, space situational awareness is an important support for the normal operation of space assets, and optical observation is one of the important means. In this paper, the solar radiation, the earth radiation and the earth albedo radiation received by the space target are simulated by Monte Carlo simulation method, and the simulation program is written based on the unstructured tetrahedral grid, and the calculation results are compared and verified. Furthermore, for the orbit external heat flow received by the sun-synchronous orbit satellite, the grid with solar panels is used to analyze the orbit heat flow received by each surface with or without occlusion. The results show that the average heat flow value of -Y surface decreases by 53.79 W/m² after considering occlusion in the ground mode. The average surface heat flow value of +Y-Z side panel decreased by 32.05 W/m². The temperature characteristics of each surface are given based on the properties of surface materials, and the accuracy of the calculation is verified by combining with the on-orbit telemetry data of the solar panel temperature. Finally, the infrared radiation intensity in each direction of the two modes is calculated. The results show that the influence of heat flow on the surface is different under different observation modes. The temperature of the surface varies with time under the earth mode, while the heat flow on the surface is stable under the sun mode. Under the two modes, the temperature of the solar panel is higher, the radiation intensity is larger, and it has obvious infrared characteristics, which is convenient to carry out infrared observation.

Ultraviolet lasers play an important role in the study of ultraviolet resonance Raman spectroscopy. The Raman resonant Raman effect enhance Raman signals and reduces the detection limit of Raman measurement. This paper focuses on the study of an all-solid-state deep-ultraviolet laser with an output wavelength of 228 nm. The laser uses Nd:YVO₄ as a gain medium and electro-optic q-switched cavity dumping technique to achieve a fundamental frequency output of 914 nm in pulse widths of several nanoseconds. Then, the second-harmonic generation is achieved by LiB₃O₅(LBO), and the fourth-harmonic 228 nm UV laser is obtained by beta-barium-borate (BBO). The variation of fundamental and second harmonic laser power at different repetition rates is investigate. The average power of Nd:YVO₄ is saturated and decreases with increased repetition rate due to the low gain at 914 nm. The output efficiency of UV laser is optimized by adjusting the focus lens. At the pump power of 30 W, the highest average power of a 228nm UV laser is 84 mW at 10 kHz. The repetition rate of UV laser is continuously adjustable within the range of 5 kHz−25 kHz, and the pulse width is maintained at 2.8 to 2.9 ns which meets the application requirements in the field of UV spectroscopy detection technology.

The objective of this study is to explore the optimal detection location and the best prediction model of the brix value of Yongquan honey tangerines, which can provide a theoretical basis for the brix measurement and classification of honey tangerines. With the wavelength range of 390.2−981.3 nm hyperspectral imaging system was used to study the best location for detecting the brix of Yongquan honey tangerines, and the spectral information of the calyx, fruit stem, equator and global of Yongquan honey tangerines were combined with their brix values of corresponding parts to establish its prediction model. The original spectra from the different locations were pre-processed by standard normal variance transformation (SNV), multiple scattering correction (MSC), baseline calibration (Baseline) and convolutional smoothing (SG), respectively, and the partial least squares regression (PLSR) and least squares support vector machine (LSSVM) models were established based on the pre-processed spectral data. The best pre-processing methods for different parts of the honey tangerine were found, and the spectral data obtained from these pre-processing methods were analyzed using the competitive adaptive re-weighting algorithm (CARS) and uninformative variable elimination (UVE) to identify characteristic wavelengths. Finally, the PLSR and LSSVM models were established and compared based on the selected spectral data. The results show that the global MSC-CARS-LSSVM model demonstrates the most accurate prediction performance, with a correlation coefficient of Rp=0.955 and an RMSEP value of 0.395. Alternatively, the SNV-PLSR model of the equatorial location of honey tangerines was found to be the next more effective, with a correlation coefficient of Rp=0.936, and an RMSEP value of 0.37. The correlation coefficients of the two prediction models are similar, the equatorial location can be used as the optimal location for measuring the brix of honey tangerines. This study demonstrates that the use of varying segments of the orange impacts the accuracy of prediction models. Identifying the optimal location and prediction model can provide a theoretical basis for classifying oranges for brix testing.

Conventional imaging spectrometers generally have low variable power, which is not conducive to the extended application of large-field, long-slit, multi-channel optical systems. In space remote sensing, the radiation energy of the ultraviolet band is low, which requires the imaging spectrometer to have a smaller F-number. In order to meet the requirement of detecting small F-number of high variable power and high spectral resolution imaging spectrometer, a high spectral resolution Offner UV imaging spectrometer with high variable power is designed in this paper. An improved Offner structure with light and small size is adopted in the rear beam splitting system of the imaging spectrometer. Based on the requirements of variable power ratio and small F-number of the imaging spectrometer, the initial Offner structure parameters are derived theoretically. A meniscus lens is inserted in front of the image to increase the degree of freedom of optimization of the system and improve the imaging quality of the system. The resulting imaging spectrometer works in the 270~300 nm band with a long slit of 40 mm, a spectral resolution better than 0.6 nm, a spectral sampling of 0.15nm, the system variable power ratio less than 0.22, and an F number less than 2. the system modulation transfer function (MTF) is better than 0.9 at a cutoff frequency of 14 lp/mm, and the root mean square radius (RMS) of each field of view in each band is less than 12 μm. This study provides a design scheme for the UV-band hyperspectral detection imaging spectrometer with small F-number and high variable power.

With excellent optical properties and high carrier mobility, perovskite materials have become highly competitive materials in the field of space solar cells. However, space particle irradiation can change the structure and optical properties of materials, leading to a rapid degradation of device performance. In order to investigate the influence of electron irradiation on the structure and optical properties of CsPbBr₃ nanocrystals, this paper conducted electron irradiation experiments on CsPbBr₃ materials, characterized the microscopic morphology of CsPbBr₃ nanocrystals by high-resolution transmission electron microscopy method. Moreover, this paper investigated the change trend of crystal structure by X-ray diffraction analysis and X-ray photoelectron spectroscopy analysis. The results revealed electron irradiation caused the CsPbBr3 nanocrystals to become rough and significantly reduced in size. The nanocrystal became compact and formed nanocluster under high-dose electron irradiation. Furthermore, the optical properties of CsPbBr₃ materials were characterized using steady-state UV-Vis absorption spectra and photoluminescence spectra. The analysis of lattice expansion-induced bandgap changes after irradiation was performed using first principles calculations. It is demonstrated that electron irradiation deepened the color of nanocrystals and affected the light transmittance of CsPbBr₃ nanocrystalline, thereby enhancing the optical absorption performance of the samples. However, electron irradiation also led to the decomposition of CsPbBr3 nanocrystals, resulting in a significant reduction in luminescence intensity by 53.7%−78.6% after high-dose irradiation. These findings provide valuable data support for the study of spatial radiation damage mechanisms and the application of perovskite nanocrystals.

A novel photonic quasi-crystal fiber (PQF) sensor based on surface plasmon resonance (SPR) is designed for simultaneous detection of methane and hydrogen. In the sensor, Pd-WO₃ and cryptophane E doped polysiloxane films deposited on silver films are the hydrogen and methane sensing materials, respectively. The PQF-SPR sensor is analyzed numerically by the full-vector finite element method and excellent sensing performance is demonstrated. The maximum and average hydrogen sensitivities are 0.8 nm/% and 0.65 nm/% in the concentration range of 0% to 3.5% and the maximum and average methane sensitivities are 10 nm/% and 8.81 nm/% in the range between 0% and 3.5%. The sensor provides the capability of detecting multiple gases and has large potential in device miniaturization and remote monitoring.