This PDF file contains the front matter associated with SPIE Proceedings Volume 12769, including the Title Page, Copyright information, Table of Contents, and Conference Committee lists.

White Light Interferometry (WLI) is a widely used technique for surface recovery. However, it is extremely sensitive to various external disturbances, increasing the uncertainty on measurement results. In this paper, a time-domain guided filtering-based surface recovery algorithm is proposed for WLI. The reference signal is firstly simulated according to the spectral map of illuminator employed in the system. The correlation between the actual correlogram and the simulated one is then analyzed through the generalized cubic correlation delay estimation method. The corrected correlogram is obtained as a local linear transformation of the reference one that has been shifted, where the linear coefficients are estimated using least squares analysis. The surface height is then retrieved based on mapping relationship between the phase and frequency. The capability of the proposed method on noise suppression is investigated through simulation under different levels of additive noise. In the experiment, a step height standard (VLSI,181.0nm±2.1nm) is employed, which verifies the performance of the proposed method on measurement accuracy and reliability.

Absolute testing for metrology has always been one of the important development directions of precision measurement. The mask with binary code is an important structure for forming absolute positioning pulses in grating encoders. The increase in the number of codes is beneficial to the resolution of positioning, but design of codes has always existed the problem that the optimal design cannot be obtained when the number of codes increases. This paper proposes a design method of binary code based on the genetic algorithm, which can get the required binary code more quickly when the number of codes is greater than 150 or even higher. The specific method can randomly generate binary codes with their fitness factors, and the binary codes enter the algorithm as the parents based on the mutation, crossover, and selection. Then the reproduce binary codes will have higher and higher fitness factor. This method can quickly generate satisfactory binary codes with specified performance, thus providing high resolution at the nanometer level for absolute positioning measurement. This work provides help and reference for future absolute positioning measurements.

Spectral confocal technology is widely used in the field of object contour scanning with non-contact measurement. For high-speed collection of spectral confocal signal, the collection speed is not only related to the integration time of the photodetector but limited by the efficiency of reading out the spectral signal from the detector. In order to solve this problem, a spectral confocal signal collection method based on acquisition and tracking algorithm with variable window width is proposed to improve the data collection efficiency. The algorithm improves collection efficiency by only collecting the useful signals in the spectrum. The simulation results show that the signal collection efficiency with the proposed algorithm for the CMOS sensor is improved significantly compared to the conventional method. For smooth object surfaces, the data collection efficiency is improved above 44.5 times. It is proved that the proposed method in this paper providing a novel approach for implementing high-speed collection of spectral confocal signal.

As the semiconductor industry grows, sub-micron films are becoming more important and more versatile. Characterizations of film thickness is essential in order to determine the optimum process conditions to minimize defects on the product. Spectral interferometry can directly obtain axial information about the sample. However, if the optical thickness of the film is less than 1 μm, the frequency domain information of the upper and lower surfaces overlap each other and cannot be separated, making it impossible to introduce the film thickness. We propose a spectral interferometry method for obtaining thin film information by fitting Fourier transform spectra to the thickness of thin films up to 1 μm. We built a Michelson-type interferometric structure and measured to obtain the interference spectrum between the reflected light of a thin film sample on a silicon substrate and a reference mirror. The Fourier transform spectrum reflecting the axial information was obtained by using the Fourier transform of the interference spectrum, and then the optical range difference between the sample and the reference mirror was obtained by peak finding. Further, a fitting model of the Fourier transform spectrum is obtained. Finally, the film thickness is obtained by minimizing the error function. We used INTERCONNECT to simulate the system and verified that the scheme is effective. In addition, we measured several film samples with different thicknesses, which are consistent with commercial ellipsometry measurements.

High aspect ratio (HAR) microstructures are widely used in fields of microelectromechanical systems (MEMS) and three-dimensional integrated circuits (3D-IC). Depth of HAR structures, as one of the key functional features, largely determines both the performance of micro and nanostructured sensors and the process difficulty. In particular, the process trend of HAR exacerbates the scale effect and triggers defects such as filled voids and defects, resulting in poor depth uniformity, which greatly affects the actual performance of the device. Therefore, it is essential to develop a reliable method for accurately inspecting the depth of HAR microstructure, especially in-line inspection. However, traditional reflection spectroscopy measurements face a significant challenge due to the sharp attenuation of the optical signal returned from the bottom of the structures. In this study, we propose an optical measurement method that utilizes reflection spectroscopy to easily measure the depth of very deep HAR trenches. The system comprises flexible fiber optic rays, which effectively achieve a ultra-low numerical aperture (NA) during the measurement. This improvement enhances the interference contrast of the reflection spectra. Additionally, a telecentric lens with a camera is used to image the microregion and locate the measurement position. For demonstration, we measured a single trench using the homemade system, and successfully verified that the system can measure structures with a measurable high aspect ratio up to 50:1 and a measurable depth of over 400 μm. Overall, our proposed optical measurement method offers a reliable solution for inspecting the depth of HAR microstructures, enabling improved device performance and process control.

In the manufacturing process of aspherical and spherical optics, precise measurement of radius error, sag error, and form error are crucial. Interferometers and spherometers are utilized for accurate measurements. However, the traditional method of manually collecting and inputting measurement data to CNC machines for error compensation is time-consuming and inefficient. To tackle this issue, a closed-loop manufacturing approach is proposed to minimize defective workpieces and enhance production efficiency. The storage, collection, processing, and networking of data through a local area network (LAN) server for closed-loop error compensation can play a vital role in the manufacturing process. Furthermore, the integration of industrial robots allows uninterrupted manufacturing without the need for human operators, enabling continuous production for extended periods facilitated by automated guided robotic arms. These advancements streamline the manufacturing process, improve efficiency, reduce labor costs, and enhance the overall quality of spherical and aspherical optics production.

We present an improved dispersion-encoded full-range technique that is suitable for samples with a wide range of depths. Considering that the detection optical signal caused by the rough surface of the sample is weak, the signal is easily submerged by the disturbance term and the phase compensation is not accurate. In this paper, the DC is removed by subtracting the envelope of the interference spectrum, so that the DC broadening in the spatial domain is suppressed and the weak signal near the 0 optical path can be resolved. Considering the problem of unwrapping phase error caused by the inherent defects of the system, the accuracy of dispersion phase extraction is improved by evaluating the phase continuity and removing the greatly affected data. Using the proposed measurement method, the depth measurement range of the system is extended from 6mm to 12mm, and the full-depth image of the ceramic standard step block is measured experimentally.

Multiscale analysis and characterizations of metallic surface topographies is a crucial task in advanced manufacturing and precision engineering. In this paper, we present a multiscale measurement technique based on photometric stereo for accurately reconstructing surface topographies at different scales. Our system employs a zoom lens and LED illuminators, providing the flexibility to adjust the measurement scale. To ensure efficiency and accuracy during scale transition, a fast light source calibration method using a Lambertian sphere is proposed to obtain the position and orientation of the LED precisely and simultaneously. A surface reconstruction algorithm is designed through modeling the light propagation process, enabling the identification of surface features at different levels of detail. The system is calibrated using an Edmund USAF resolution target, which demonstrate the accuracy of our method with the minimum deviation as low as 4μm. The proposed approach is applied to investigate the multiscale surface topography produced by metal additive manufacturing (AM) technique, achieving an accurate representation from contour to roughness. The results are compared with those obtained from a commercial 3D scanner from Keyence, which validate the effectiveness of our method and show its great potential in quality control and optimization of manufacturing processes.

Recent advances in lensless imaging have demonstrated that the Fresnel zone aperture (FZA) camera can achieve incoherent imaging using four-step phase-shifting and perform synthetic aperture super-resolution reconstruction through Fourier ptychography. However, the reconstructed images are severely degraded due to the low signal-to-noise ratio of the imaging process. In this paper, we introduce total variation (TV) regularization to improve the quality of reconstruction in Fourier ptychography of the FZA camera. Numerical simulations and optical experiments verify that adding TV regularization to Fourier ptychography can increase the peak signal-to-noise ratio of the reconstructed images by 2 dB, enhancing the synthetic aperture super-resolution capability.

Line-shaped beam based Doppler distance sensors enable 3D inspection of rotating rough surfaces for instance in working lathes by a simultaneous, multipoint velocity and distance measurement. To minimize the systematic error of the measurement, this work presents a high-accuracy 3D model and calibration of the interferometric fringe volume of the sensors. The model is derived from the Gaussian beam expression and applied to describe fringe geometry distribution throughout the intersection volume of two paraxial Gaussian beams. A full-field fringe spacing calibration using a high-resolution matrix camera is performed with two line-shaped beams as a demonstration, which shows an average relative difference of below 0.6% to the modeling result.

A dual-beam Fizeau interferometry with both small and large aperture two measurement modes is proposed. The two modes of the interferometer were measured and analyzed using three-flat four-step absolute measurement and three-flat simulated sinusoidal phase grating. An integrated 4″-18″ aperture dual-beam Fizeau interferometer was used to perform experiments on large and small aperture by the above two measurement methods. The experimental results show that the absolute surface errors of the three flats are less than λ/20(PV) and λ/100(RMS), and the transfer function is better than 0.78 at the 1 mm-1 spatial frequency, which satisfies the specification.

In modern manufacturing, the in-process measurement of complex surface of cylindrical gear is critical and challenging, and is directly associated with subsequent assembly and terminal gear quality. 3D geometric measurements of gear are ones of the crucial fundamental quantities to ensure their conformity to design specifications serving a range of industries, from shipping, automotive and aerospace industries to house applications. In this paper, an automated sampling path planning model is designed in order to obtain a loss cost sampling path by consider of the complex surface of cylinder gear. The high-precision full information model of tooth flank is also being established, which depends on the measurement procedure and the measurement uncertainty. A series of experiment on several typical cylindrical gears were carried out to demonstrate this automated path planning technique and the final geometric measurement accuracy. On the other hand, an commercial 3D geometric measuring system was also introduced, which has two degrees of laser scanner. Those scanning paths generation have been proven to be amenable for practical purposes through many tests so that it might be applicable to achieve 3D geometric measurements of large gear

The near optical coaxial phase measuring deflectometry (NCPMD) is one of the phase measuring deflectometry (PDM) techniques which is typically used for specular surface form measurement. The NCPMD utilizing a plate beamsplitter to folding the optical axis of display screen to make it close to the optical axis of the imaging system which makes the system more compact and has significantly reduced volume compared with the traditional PMD configuration. The NCPDM can achieve compact configuration, light weight, and reduce measurement error caused by structure shadows of the off-axis configuration of traditional PDM. However, the plate beamsplitter will lead measurement errors to the NCPMD system due to the beamsplitter will inevitably inherited certain form errors on the two surfaces during manufacturing process. In this paper, a reflection error model of the NCPMD system is proposed, and the measurement error caused by the reflection effect of the plate beamsplitter is determined by considering the influence of the unevenness of the upper and lower surfaces of the plate beamsplitter. Simulation studies show that the proposed reflection model can accurately determine the measurement errors caused by the form errors of the beamsplitter, which can be effectively used for subsequent error compensation.

In this paper, we present a method of using computer-generated hologram (CGH) to measure the mid-spatial frequency error of large aperture lenses. To validate this test approach, we designed and fabricated a 450 mm × 450 mm reflective CGH for testing the 440 mm × 440 mm spatial filter lens with a focal length of 32500 mm. In our experiment, both the 0th and 1st order diffraction wavefront of CGH were measured, and the 0th order diffraction wavefront was used to calibrate the substrate error. The mid-spatial frequency error caused by the CGH fabrication errors were evaluated using the binary linear grating model and power spectral density theory (PSD). Experimental results and error analysis indicate that the measurement accuracy of PSD1 is ~0.9 nm RMS, which means the CGH test approach can be used to measure the mid-spatial frequency error of large aperture lenses.

In traditional metasurface structure design, it heavily relies on electromagnetic simulations to obtain transmission and phase spectral, followed by empirical adjustments. This iterative trial-and-error process, especially when dealing with multi-objective optimization tasks, demands intensive and time-consuming computations, which to a certain extent restricts the development of the metasurface research field. In this paper, a proposed method achieves rapid prediction of spectral responses corresponding to structural units by seeking analytical solutions within the constructed neural network model. The proposed deep learning-based method for predicting transmission and phase spectral of metasurface units consists of metasurface unit dataset construction and a ResNet-based network framework. In the dataset construction approach, an overhead view of the unit structure is extracted and transformed into a binary image, where scaling factors are coupled into the two-dimensional image to increase dimensionality. This enables the representation of different structures such as square pillars, elliptical cylinders, and varying sizes of metasurface units using the same data format, significantly enhancing network generalization. Within the network framework, ResNet is employed to predict the real and imaginary parts of the S21 parameter, which are then inverted to obtain transmission and phase information. The progressive training method employed in combination with this framework yields high prediction accuracy. The deep learning-based method for predicting transmission and phase spectral of dielectric metasurface units, as revealed in this paper, achieves a 7200-fold increase in prediction speed compared to traditional electromagnetic

The vibration of wafers can significantly impact the accuracy and efficiency of wafer inspection, especially when the wafer is placed vertically. And the larger the wafer size, the thinner the thickness, the more obvious its vibration. To improve the efficiency and accuracy of wafer inspection, and also to make wafer inspection more adaptable to the complex inspection environment and reduce the cost of inspection, this study through a large number of experiments to find out the main factors that lead to vibration of the vertically placed wafers, such as temperature changes, mechanical vibration, environmental disturbance, airflow disturbance, and fluid-solid coupling. The main method is to analyze the vibration law of the wafer through the vibration of the interference fringes produced when the wafer is affected by different disturbing factors during the interferometry process. After effectively controlling the above interference factors in the wafer inspection process, the practical data of wafer surface shape can be measured continuously and stably.

In the phase-shifting interferometry, the surface phase diagram is corrected by spectral analysis of the ‘intensity-phase pattern’ (the relationship between the interference intensity and the measured phase) of each phase-shifting image to achieve the purpose of reducing the vibration effect. This spectrum analysis algorithm is different from the previous methods. It does not determine the phase diagram, but corrects the phase diagram obtained by PSI measurement. It has few restrictions on the surface shape, and unlike the spatial Fourier method, it does not require high-density spatial carrier fringes, although at least a fringe of phase departure is recommended. The error between the influence of the simulated vibration signal on the phase and the influence of the actual measurement signal on the phase is less than 5 %.

Various dynamic goniometric systems are applied in modern practice to measure a plane angle in dynamics with high accuracy. As a rule, these systems are either designed to measure the angles of optical prisms, or they are verified/calibrated using optical polygons, that are standard angular measures. Optical null-indicators of various types are used in dynamics to bind the reflecting faces of the prism to the measuring system. Until recently the interference null-indicator could be regarded to provide the best measurement accuracy, but it has one significant drawback. This type of null-indicator is highly sensitive to the propagating wavefront quality and thus it cannot be used other than at short distances and in stable environment. For several years, the authors have been developing and researching various modifications of null-indicators based on the autocollimation principle, which are more robust considering the operating conditions. Preliminary tests of prototypes have shown that such devices are also capable of providing accuracy of angular measurements at the level of hundredths fractions of an arc second, as well as interference ones. It is known that quality of the reflecting surface may affect the high precision angle measurements conducted by optical non-contact means. When comparing the measurements involving null-indicators that implement different optical principles, this influence may become even more significant. The paper presents the experimental comparison research of interference and autocollimating null-indicator performance. Both null-indicators were installed simultaneously as a components of high precision laser dynamic goniometer. The 8- sided optical polygon with known flatness parameters of reflecting faces was used as a test object. In order to distinguish the measurement error determined by the reflecting surface flatness and null-indicator type from the total measurement error the cross-calibration procedure was carried out.

The dispersive interferometry provides an instantaneous surface measurement in a single camera frame, making it resistant to environmental disturbances and ideal for in-process surface metrology. It also benefits from the extended measurement ranges in both depth and lateral directions by incorporating hyperspectral imaging technology and cylindrical beam illumination, respectively. This paper reports on an in-house developed cylindrical lens-based dispersive interferometer for high-accuracy surface inspection, particularly for structured surfaces. The obtained spectral interferogram is analyzed using the fringe order algorithm, in which the phase slope method is used to calculate the initial height to resolve the fringe order ambiguity and eventually an improved height value can be obtained using the exacted phase of a single wavelength. Experiments demonstrate that the measurement noise of the developed interferometry system is less than 1 nm within the measurement range. A brass step sample made by a diamond turning machine was measured and the experimental results closely align with those given by the commercial white light interferometer -Talysurf CCI 3000.

Due to the excellent dynamic measurement capability of laser tracker, a combination of multiple laser trackers has the possibility of synchronously and dynamically measuring multiple targets. However, there is still an issue that measurement data from multiple laser trackers must be unified not only on the spatial coordinate system but also on the time reference. This paper studies a dynamic combined measurement method of multiple laser trackers. Firstly, the methods of the coordinate frames alignment, the time references unification and the uncertainty evaluation are studied. Secondly, the hardware and software designs of the dynamic combined measurement system are introduced in detail. Finally, the dynamic combined measurement of multiple laser trackers was applied to the test of the master-slave control delay time of the master-slave control RA equipment, and the experimental results demonstrate its feasibility.

When using Phase Measurement Deflectometry (PMD) to measure a surface with multiple levels of reflectivity, complete phase information can be obtained by reducing exposure. This enables point-to-point mapping of the imaging surface and projection surface. Through these operations, adjustments can be made to the intensity of the light source, resulting in the division of the light source into regions. The ultimate goal is to achieve high-precision phase measurement of objects with multiple levels of reflectivity. However, the adjustment of light intensity at the location of sudden changes in reflectivity can lead to mutual interference between adjacent¹ reflectivity regions. Due to the fact that the focusing surface of the camera is usually on the measuring surface, the position of the display is away from the focus. This results in a point on the imaging surface corresponding to diffuse plaques on the display. The intensity of the light source within the diffuse plaques can impact the imaging intensity. Therefore, imaging points located at the edge are highly susceptible to the influence of modulation intensity on both sides, resulting in darker low reflectivity areas at the edge, brighter high reflectivity areas at the edge, and even overexposure. In order to solve this problem, this paper analyzed the defocusing situation of the system and eliminates this influence through optical methods.

The utilization of film cooling holes design can ensure rapid cooling of the aero engines turbine to achieve effective blade protection. To achieve optimal cooling, geometric features such as aperture, hole spacing and cone angle of the film cooling holes are necessary to be measured. We propose a spectral interferometry system method, which can measure aperture and depth of the holes and surface topography of the engine blade, and calculate the geometric characteristics of the holes by processing this information by 3d point cloud. Comparing the measurement result of our system with the measurement result of film cooling holes slice, it can be obtained that the error of aperture and spacing of holes is about 20μm, the repeated measurement accuracy is 0.8μm, and the cone angle error is about 2°.

The measurement uncertainty is an important parameter to evaluate the reliability of the Rayleigh lidar in detecting atmospheric temperature. This presentation aims to study the atmospheric temperature measurement uncertainty of a floating platform-mounted Rayleigh lidar. A model was established for altitude correction considering the platform attitude, and the temperature uncertainty originating from the fluctuation in rolling and pitching angles was evaluated using the Monte Carlo method (MCM). The results show that the atmospheric temperature uncertainty due to platform fluctuation is confined to 10-2 K when the detection altitude is up to 65 km.

Absolute measurement has always been one of the important development directions of precision measurement, there are problems that the diffraction and mask working parameters are not considered in the positioning pulse analysis of the absolute code mask at present. Therefore, in order to solve the coupling optimal performance problem of absolute positioning code in actual work, an absolute code should be designed for working in the best parameter-model. In this paper, a multi-parameter model of absolute code working status is established, and the influence of working parameters on its positioning performance is analyzed respectively. The analysis shows that the distance and the angle between the mask and the grating, and the width of the unit code will affect the positioning accuracy. The three parameters restrict each other, and there is a coupling optimal solution. The optimal working state can be obtained through parameter analysis, so as to provide the design and installation parameter guidance of mask. The proposed research can help the practical application of absolute positioning measurement.

The rapid measurement and demodulation of speed-range information to realize high-speed dynamic target simultaneously is of great significance to the development of industrial manufacturing and precision measurement technology. In the fields of aerospace, industrial automation and machine tool processing, rapid and precise measurement of dynamic target speed distance information is a key method to realize precision measurement, in-situ measurement and running state detection. Frequency Modulated Continuous Wave (FMCW) laser precision measurement technology has the characteristics of no cooperation, high precision, wide measuring range, strong anti-interference ability, etc. It is widely used in industrial measurement field. FMCW laser measurement system synchronously to achieve high speed target still has technical shortcomings. The proposed FMCW velocity-distance synchronous measurement method uses the optical frequency comb as a reference rule to intercept and operate signals at equal frequency intervals. It fits the FMCW laser measurement dynamic target frequency change curve to achieve the frequency parameter estimation of target measurement signals. The problem that FMCW laser measurement of dynamic target is slow and spectrum broadening is serious can’t accurately obtain target speed-distance information is solved. The experimental results show that the proposed method can obtain the speed in the simulation experiment with the target speed of 100m/s and the distance of 100m, and the maximum distance errors are 0.011m/s and 0.00117m respectively. The standard deviation of speed and distance measurement of this method is not higher than 0.090403m/s and 22.46μm in the online high-speed turntable measurement experiment with the speed of 11m/s.

In the background-oriented schlieren (BOS), the 3D deflection caused by refractive index gradient is projected onto the camera imaging plane with one dimension leaved out, and sensed as a 2D displacement using the images of background with and without the flow field. In the reconstruction, instead of decomposing the 2D displacement as in previous studies, we project the elements in the BOS weight matrix to 2D. By doing so, this technique reduces memory usage and improves the reconstruction time as the number of rows in the weight matrix is decreased by a third, and the errors produced in 2D displacement decomposition are avoided.

In this paper we propose an algorithm for autocollimators with cylindrical surfaced reflectors. We discuss it’s flow and how it can be achieved. Optimal flow can contain the following steps in the order, they should be performed: noise filtering, line width reduction, line separation, clustering, determination of an angle for each line.

We present a coherence scanning interferometer based on a mode-locked femtosecond laser, enabling precise pulse alignment for cross-correlation interferogram acquisition. However, Nyquist's law necessitates step lengths below 1/8 of the central wavelength, while area-array detectors face limitations in pixel density and frame rate due to communication throughput. To overcome these challenges, we propose downsampling methods that preserve interferometric contrast. The simultaneous exposure method maintains a stationary state for exposure at each sampling point, mitigating contrast loss from phase shifts. The phase compensation technique reduces carrier frequency through acousto-optic modulators, preserving high-contrast interference signals without altering the scanning mechanism. Leveraging our optimized frequency domain analysis algorithm, both methods achieved nm-level measurement accuracy with μm-level scanning intervals, facilitating efficient profilometry.

In this paper, we mainly use the basic principle of Fizeau interferometer, because Fizeau type interferometer has the advantage of common optical path, which can reduce the influence of some system errors to a certain extent, and the requirements for environmental changes are relatively low, and then use zemax optical simulation software to simulate the cat's eye position, confocal position and confocal rotation 180 degree position in the three position absolute detection method, and establish the absolute measurement model . Through the combination of simulation and simulation, it is concluded that the measurement error mainly includes tilt error, translation error and defocus error. Among them, the tilt error and translation error have negligible impact on the system measurement results, and the defocus error has a greater impact on the measurement results. Finally, the defocus error is removed by a new higher-order defocus removal method.

Optical testing is constantly evolving, necessitating higher lateral resolution in interferometry. Achieving high resolution leads to longer processing times, significantly impacting testing efficiency. The unwrapping phase algorithm is crucial in interferometry, but its complex calculations can impede efficiency improvements. There are two types of algorithms for the unwrapping phase: path-dependent and path-independent. Path-dependent algorithms tend to be more efficient, and thus, we have chosen to utilize the accelerated path-dependent algorithm. Among these algorithms, Goldstein's algorithm is widely applied. This study uses CPU-GPU heterogeneous computing to parallelize and accelerate the Goldstein phase unwrapping algorithm while maintaining acceptable numerical error limits. Our proposal focuses on optimizing the serial Goldstein algorithm for GPU architectures by parallelizing and enhancing three key steps: residue identification, branch cutting, and integration. Specifically, our optimization approach leverages GPU shared memory and SIMD functionality. To assess the efficiency of our proposed method, we conducted tests on the unwrapped phase image with varying pixel sizes. The results demonstrate that as the pixel size increases, the performance gain from GPU computation becomes more pronounced compared to CPU computation. Using a 4096×4096 phase diagram on the RTX3070 laptop hardware, we achieved a 60x speed increase in the overall process compared to the CPU version. Therefore, employing this algorithm with the GPU can significantly expedite the phase unwrapping process and enhance the efficiency of interferometry.

White Light Scanning Interferometry (WLSI) is a mature and key method of non-contact three-dimensional (3D) morphometry. However, bat-wing is an inherent problem with WLSI, introducing systematic errors to the measurement results. In this paper, we proposed a filtering algorithm based on the convolutional neural networks (CNN) to solve the problem. A 450 nm standard step is tested to verify the effectiveness of the algorithm. The results show that the method can effectively suppress the batwing effect.

In order to solve the problem that the laser confocal vibration measurement method is susceptible to noise and interference signals. This paper proposes a laser confocal vibration signal processing method based on wavelet denoising. By using wavelet transform to denoise the laser confocal vibration signal, this method effectively eliminates noise and interference signals. The experiment shows that the use of wavelet transform can effectively improve the test results of laser confocal vibration measurement, achieving a measurement bandwidth of 100MHz and a nanometer-level amplitude resolution. This method provides ideas for expanding the application of the laser confocal vibration measurement in complex scenes.

To address the problem that the traditional multi-wavelength wavefront detection requires manual adjustment of mechanical devices and low automation, this paper proposes a multi-wavelength laser interferometer control system with the Fizeau-type interferometer principle as the background, using Visual Studio to establish the upper computer control interface on the computer and sending signals to the microcontroller through the serial port to control the interferometer. Among them, the main controls are the switching of fluorescence alignment plate in 1064nm laser, the translation drive of collimating lens within 2mm of Z-axis, the automatic adjustment of variable diaphragm and the variable adjustment of CCD. The system realizes the automatic switching of five wavelengths of the multi-wavelength laser interferometer by controlling the precision motor, which reduces the error caused by manual adjustment and improves the measurement accuracy and efficiency of the interferometer.

Traditional 3D human pose estimation algorithms are often influenced by the accuracy of 2D keypoint detection and camera calibration, and they struggle to handle low-resolution and occluded scenes. To address these challenges, we propose a multi-view 3D human pose estimation method that incorporates prior information. At the 2D pose extraction stage, we design a bottom-up detection network called HRPifPaf to achieve accurate human pose detection in low-resolution scenarios. It first constructs a high-resolution feature extraction module that combines features from different scales. Then, a joint prediction and association module combines confidence scores and scale factors with vector directions pointing to the main body parts of the joints. We also utilize a Kalman filter to optimize the final detection results. At the 3D pose synthesis stage, we propose a multi-camera parameter joint optimization calibration method that leverages prior information of the human skeleton to address challenges such as body occlusion and inaccurate camera intrinsic and extrinsic parameters, designing a comprehensive cost function based on reprojection error, and human body geometry constraints.

The measurement of the six degrees of freedom (6-DOF) is crucial in industrial manufacturing, enabling efficient operation of machinery. The combination of 6-DOF and the quaternion coordinate system offers a robust framework for accurately representing and controlling the motion and orientation of objects in 3D space. Electro-optical measurement systems are commonly used in these cases due to their advantages such as compact design, fast measurement speed, high stability, and accuracy, as well as the ability to directly measure displacement parameters of the object. The proposed autocollimator optic-electronic system is designed to provide accurate measurements of the position and motion coordinates of industrial objects. It consists of an autocollimator, reflector, radiation marks, lenses, CMOS matrix photoreceivers, and a computer for calculations. By combining the equations related to the quaternion coordinates, reflected images, and image distances, a system of equations is formed to determine the six motion coordinates of the object. The proposed autocollimator optic-electronic system offers a practical solution for accurate measurement of industrial objects' motion coordinates, optimizing both accuracy and efficiency. It can be applied in various applications where precise measurements are required. The autocollimator measuring system outperforms the three-point optic-electronic system in terms of measurement accuracy for all six coordinates encompassing rotational motion and linear displacement. The autocollimator system offers higher precision, particularly in linear displacements, angular rotation, and rotational axis position.

Aiming at the problem that high steepness aspheric optical components lack a versatile and efficient surface shape detection method in the grinding and rough polishing stages, swing-arm profilometer suitable for high steepness aspheric surface shape detection is proposed. The system can perform both high and low steepness aspheric specular inspections. We established the mathematical measurement model of the swing-arm profilometer, carried out the mechanical structure design, built the swing-arm profilometer prototype, and designed the error compensation algorithm. The system has the advantages of easy adjustment and high measurement efficiency. The swing-arm profilometer prototype is used to measure the standard spherical mirror and ellipsoidal mirror, and the measurement results show that the measuring device has good detection accuracy and repeatability, which can effectively improve the measurement and processing efficiency of aspheric optical components.

In interferometers, defects on the surface of optical elements can generate coherent noise, such as “Newton’s rings,” in interferograms, thereby affecting measurement accuracy. To address this issue, this paper proposes a method for extending the light source using a multimode fiber. By adjusting the parallel beam coupling into the multimode fiber, the coherent noise of the light source can be eliminated. The proposed method is verified in a Twyman-Green interferometer with a 25.4 mm diameter, employing a multimode fiber with a core diameter of 1 mm. Experimental results demonstrate a 36.9% reduction in scattering contrast and a 43% improvement in signal-to-noise ratio (SNR) of the interferometer when the fiber is moved ±1 mm perpendicular to the optical axis, while maintaining a fixed incidence angle of 1° to the optical axis. These findings confirm the effectiveness of the proposed method.

This article proposes an automatic calibration device for wavefront system error, which achieves three degrees of freedom random rotation of a spherical lens through hardware circuits and software algorithms. It is combined with tools such as a 4D interferometer to obtain wavefront information. Finally, the data is processed using MetroPro software to achieve fast and accurate error calibration. This device is easy to operate, efficient and stable, overcoming the problems of traditional manual calibration methods, and providing a reliable tool for the development of absolute measurement technology of wavefront aberration. The automated calibration motion platform in this article improves the shortcomings of traditional manual calibration and achieves rapid calibration of wavefront system errors, providing a reference for research and application in this field.

In photoacoustic tomography (PAT), image reconstruction refers to the formation process from photoacoustic signals to target images, which has an important influence on the image quality.At present, most reconstruction algorithms assume that the medium is homogeneous, which may cause distortion and artifacts in the reconstructed images. Therefore, considering the heterogeneity of the medium is important for accurate image reconstruction in PAT. The iterative reconstruction (IR) algorithm can incorporate the information of imaging system and media, and thus can provide high-quality image reconstruction. In this work, we investigate the IR algorithm in PAT with heterogeneous media based on point source response. We obtain the system matrix by calculating the photoacoustic signal of each point source in heterogeneous media based on the k-space pseudospectral method. The target image is reconstructed iteratively with the media information-coupled system matrix and the total variation (TV) regularization. We take a set of simulations to verify the effectiveness of the IR algorithm in heterogeneous media. The work provides a new method for accurate reconstruction of photoacoustic images.

Spectral confocal technology has widespread applications in the field of surface topography measurement. However, conventional spectral confocal sensors are limited to acquiring height information for one point at a time during the measurement process. Consequently, the need for point-by-point scanning compromises the efficiency of existing methodologies. To address this challenge, we propose a novel measurement method utilizing a Nipkow disk and spectral imaging technology. This innovative approach enables simultaneous acquisition of height information for multiple points. In this paper, a dispersive objective lens is designed by using Zemax OpticStudio optical design software, specifically tailored for simultaneous multi-point measurements. The dispersive lens group consists of five single lenses and one double cemented lens, working within the wavelength range of 450nm to 720nm. The dispersion range can reach 450μm, with a dispersion linearity coefficient of 0.998. The accuracy of the dispersive objective lens for multi-point measurement is validated through non-sequential mode simulations in Zemax OpticStudio. The results demonstrate a measurement linearity of 0.998 for each individual measurement point. This simulation experiment provides theoretical foundations and guidance for subsequent experimental endeavors.

The article proposes an approach to the determination of small-form objects against a complex background. The proposed approach uses a parallel data processing algorithm that includes the following main modules: a multi-criteria image filtering block built on an objective function that minimizes the weighted average sum of the average square of the first order finite difference, as well as the average square of the distance difference between the input implementation and the generated data; parallel separation of objects by analyzing local features, statistical analysis of histogram changes, building a mask of object detailing and frequency analysis; the formation of a feature mask and the search for similarity elements by analyzing the generated features. On the test data set, an example of determining small-sized objects on a complex background with their subsequent classification into class objects is presented. The data were obtained by a machine vision system installed on a robotic complex. Data on the required parameters of the formed machine vision systems are given, recommendations on the required parameters of the algorithms are presented.

The article proposes the use of three directions of development at once to solve the problem of dividing objects into classes. The first direction uses the formation of a computationally simple multi-criteria method for smoothing data in windows of complex adaptive forms, adapting the method of dividing objects into background/structure, and simplifying images. The approaches being developed are intended for implementation on low-computing devices with the ability to parallelize processes. The second direction being worked on is the formation of a model of the structure of a neuron organized on the basis of the use of memristor structures. The paper presents an approach to the formation of such structures, provides the characteristics of such devices, and describes methods for combining analog and digital parts to implement memory or control systems. The final direction discussed in the article is the formation of a neural network for the classification of simple objects based on a model of new neurons and data preprocessing. To test the approach proposed in the work, studies were carried out on a set of test data obtained by a sensor (simple sensor) system. The generated data array for evaluating efficiency is limited by a time window and has real noise (errors). The work provides assessments of effectiveness, recommendations for the selection of parameters and presents requirements for the type and form of the analyzed data.

The studies will be carried out using optical metrology methods on a Walter Helicheck inspection machine in reflected light and a number of images were stored to form a statistical sample. Established new indicators and criteria for grinding efficiency based on image processing of the helical groove of the end mill. As a result, recommendations for the selection of optical control techniques were made for the first time at the intermediate stage of technological preparation for production, in real time, and after processing. In this work, for the first time, we prove the possibility of determining the camera displacement pith distance during continuous scanning of the profile of a helical surface in a radial section, the measurement accuracy and recreating a three-dimensional model of the object. As a result of the work of the new algorithm using the Haar-wavelet with new indicators, it was established that the actual one is located inside the focal zone, which proves the possibility of applied application of the method of monitoring the shape of helical flute of end mills using computer vision. The measurement accuracy of the helical flute increased from 4 to 12% along its profile.

A system for determining the distance from the robot to the scene is useful for object tracking, and 3-D reconstructions may be desired for many manufacturing and robotic tasks. While the robot is processing materials, such as welding parts, milling, drilling, etc., fragments of materials fall on the camera installed on the robot, introducing unnecessary information when building a depth map, as well as the emergence of new lost areas, which leads to incorrect determination of the size of objects. There is a problem comprising a decrease in the accuracy of planning the movement trajectory caused by wrong sections on the depth map because of erroneous distance determination to objects. We present an approach combining defect detection and depth reconstruction algorithms. The first step for image defect detection is based on a convolutional auto-encoder (U-Net). The second step is a depth map reconstruction using a spatial reconstruction based on a geometric model with contour and texture analysis. We apply contour restoration and texture synthesis for image reconstruction. A method is proposed for restoring the boundaries of objects in an image based on constructing a composite curve by cubic splines. Our technique outperforms the state-of-the-art methods quantitatively in reconstruction accuracy on the RGB-D benchmark for evaluating manufacturing vision systems.

We present a new haze removal algorithm based on attention map-guided multi-scale image processing. The proposed method is based on the frequency-domain coefficient correction of a set of images followed by their fusion based on the Laplacian pyramid. A new stage is presented in obtaining a local-global estimate of high-contrast images, also used in the attention map-guided fusion model. The algorithm consists of the following steps: gamma correction with different gamma parameters; the weight map calculation by multiplying the saturation, contrast, and attention for each image; decomposition of the weight map into a Gaussian pyramid; 3-D block-rooting enhancement; decomposition of images after 3-D block-rooting and gamma correction into the Laplacian pyramid; merging by multiplying multi-scale images and weights. The experiment results on the dataset D-HAZE confirmed the high efficiency of the proposed enhancement method compared to the state-of-the-art techniques for industrial inspection systems.

The article proposes an approach to the formation of the trajectory of the spatial movement of a controlled object in a confined space using stationary vision systems. For its implementation, the following main steps are used in the work: 1. Preprocessing of data generated by the machine vision system. The task includes multicriteria image processing in order to minimize the noise component and determine the boundaries of objects. 2. An automated method for adaptive non-local separation of objects on borders, background and objects. 3. Execution of the task of adaptive nonlocal binarization. 4. Building a mask of stationary and current moving objects. 5. Formation of an equidistant displacement trajectory. 6. Checking the trajectory by moving in adjacent frames. 7. Prediction and remeasurement of the position of objects in the frame based on displacement vectors and correction of the object's movement trajectory. 7. Formation of a control team to move an object in a confined space using stationary vision systems. To test the effectiveness, studies were conducted on a set of test sequences. The studies were carried out on a group of cameras in the visible spectrum (1920x1080, RGB, 8 bits) covering the entire field of view. The adaptability of the application of the proposed approach in solving complex problems is showed.

This paper examines the construction of a control system for a manipulator with a load gripper suspended on flexible links. The movement of cargo in manipulators of this type occurs by changing the lengths of the links. The introduction of a video data analyzer and strain gauges into such a system will not only improve the quality of control, but also organize direct interaction between the operator and the load through tactile influence on the load. The article presents the structure and description of the construction of a video subsystem and a strain gauge data collection system, consisting of several neuro accelerators with RISC-V core controllers, a video camera system and original electric motor drivers on which the strain gauge data collection system is installed. A computer model of the dynamics of cargo movement has been obtained, the reliability of which has been confirmed by tests.