Search Results (26)

Based on the widely used Gullstrand–Le Grand eye model, a scattering individual eye model was constructed with Zemax, which has individual ocular wavefront aberration and the scattering particles distributed in the eye. There are three main steps to build the model. Firstly, the Gullstand-Le Grand eye model was constructed, and converted into a non-sequential model. The axial lengths of all ocular components, and the corneal curvatures were input into the optical model. Secondly, a high-order aspheric surface-Zernike Fringe Sag surface was chosen to fit the wavefront aberrations measured with the ocular wavefront aberrometer. Thirdly, an embedded scattering lens within the crystalline lens was developed, of which parameters of scattering particles can be selected flexibly. The scattering individual eye model can be used to quantitatively investigate interaction between ocular aberrations and scattering light on retina image quality. The results demonstrated that when scattering particles were uniformly distributed across the optical pupil, MTFs at all spatial frequencies decreased proportionally with increasing particle density, independent of aberrations. When scattering particles were located in regions with smaller wavefront aberrations, the combined effect of scattering and aberrations synergistically degraded retinal image quality. In contrast, when particles were concentrated in zones of larger aberrations, the scattered light could partially compensate for the aberrational effects, leading to improved optical performance Full article

This study investigates a laser ranging technology scheme featuring a large divergence angle for both the emitted and received laser beams, focusing on applications where both the measured target and the ranging carrier are high-mobility platforms. A dual-concave beam-reducing lens design is adopted to reshape the original beam divergence angle of 10 mrad from the erbium glass laser into a ranging output beam divergence angle of 26 mrad, while maintaining the Gaussian energy distribution of the original laser beam. A φ500 μm photosensitive surface APD detector is used, and a combination of aspherical and spherical elements is employed in the receiving optical system to achieve a 30 mrad large field-of-view echo reception within the small photosensitive surface. This laser ranging system addresses the challenge of aiming and tracking for laser ranging between relatively high-speed moving objects and reduces the stability precision requirements for the ranging carrier platform. Full article

Infrared deflectometry is an efficient and accurate measuring method for curved surfaces fabricated via grinding or finish milling. The emitting properties and geometrical configurations of the infrared light source is a core component governing the measurement performance. In this paper, an infrared slit light source is designed based on the cavity structure of a polyimide heating film. This design ensures good stability and uniformity of the light source whilst effectively reducing background noise. Additionally, the light source can be applied as a calibration board for calibrating infrared cameras. The light source is aligned using a theodolite and cubic prism to control the positional deviations during scanning. Experimental results demonstrate that the proposed slit light source and calibration method can achieve a measurement accuracy of 1 µm RMS, which can meet the needs of rapid measurement in grinding. This approach provides a reliable, cost-effective, and efficient tool for surface quality assessments in optical workshops and has a broad application potential. Full article

The study of the refractive index of traditional lenses is one of the foundational topics in the field of optics. The refractive index of a lens determines its ability to refract and focus light, making it a key parameter in optical design and applications. For the measurement of the refractive index of blind samples of finished lenses, this paper proposes a measurement method based on the use of a focal length measuring instrument and an aspheric profilometer to measure the surface shape data of the front and back surfaces of the lens. This method combines curve fitting algorithms and curvature radius fitting algorithms, ultimately reconstructing the lens model using Zemax and back-calculating the refractive index of the lens. For the samples employed in this paper, the measurement accuracy of the focal length can achieve 1.06%, the fitting accuracy of the curvature radius can reach 0.138%, and the recovery accuracy of the refractive index can attain 6.303 × 10⁻⁴%. Full article

To overcome the limitations of phase sampling points in testing aspherical surface wavefronts using traditional interferometers, we propose a high-spatial-resolution method based on multi-directional orthogonal lateral shearing interferometry. In this study, we provide a detailed description of the methodology, which includes the theoretical foundations and experimental setup, along with the results from simulations and experiments. By establishing a relational model between the multi-directional differential wavefront and differential Zernike polynomials, we demonstrate high-spatial-resolution wavefront reconstruction using multi-directional orthogonal lateral shearing interferometry. Theoretical calculations and simulations of aspherical surface wavefront testing are followed by experimental verification on an aspherical surface with a known asphericity. Comparing the measurement results with those from the LuphoScan profilometer, we achieve a relative measurement error with an RMS precision better than λ/100. Full article

Optical aspheres are demanded with extremely high precision to meet functional requirements in space telescopes, extreme ultraviolet lithography, and other modern large optical systems. The nano-precision fabrication of optical aspheres requires high-precision measurements to guide deterministic optical processing. Null test is the preferred method for high-precision measurements. Null optics are required to compensate for the incident wavefront in the null test of optical aspheres. However, wavefront aberrations caused by the transmission flat or transmission sphere of interferometer and null optics can limit measurement accuracy and need to be separated. A nano-precision measurement method is proposed for the even optical aspheres of high order in this paper. A computer-generated hologram is used as a null optic to realize a null test on optical aspheres. Mapping distortion correction is performed on the measurement results to ensure that the transverse coordinates of the measurement results correspond correctly to those of the test surface. Absolute testing is applied to separate the wavefront aberrations caused by the computer-generated hologram and interferometer optics. Finally, the results obtained by this method were used to guide deterministic optical processing, enabling the nano-precision fabrication of optical aspheres. Full article

Aspherical surfaces, with their varying curvature, minimize aberrations and enhance clarity, making them essential in optics, aerospace, medical devices, and telecommunications. However, manufacturing these surfaces is challenging because of systematic errors in CNC equipment, tool wear, measurement inaccuracies, and environmental disturbances. These issues necessitate precise error compensation to achieve the desired surface shape. Traditional methods for spherical optics are inadequate for aspherical components, making accurate surface shape error detection and compensation crucial. This study integrates advanced metrology with optimized material removal functions in the grinding and polishing processes. By combining numerical control technology, computer technology, and data analysis, we developed CAM software (version 1) tailored for aspherical surfaces. This software uses a compensation correction algorithm to process error data and generate NC programs for machining. Our approach automates and digitizes the grinding and polishing process, improving efficiency and surface accuracy. This advancement enables high-precision mass production of rotationally symmetrical aspherical optical components, addressing existing manufacturing challenges and enhancing optical system performance. Full article

Three-dimensional reconstruction of the corneal surface provides a powerful tool for managing corneal diseases. This study proposes a novel method for reconstructing the corneal surface from elevation point clouds, using modal schemes capable of reproducing corneal shapes using surface polynomial functions. The multivariable polynomial fitting was performed using a non-dominated sorting multivariable genetic algorithm (NS-MVGA). Standard reconstruction methods using least-squares discrete fitting (LSQ) and sequential quadratic programming (SQP) were compared with the evolutionary algorithm-based approach. The study included 270 corneal surfaces of 135 eyes of 102 patients (ages 11–63) sorted in two groups: control (66 eyes of 33 patients) and keratoconus (KC) (69 eyes of 69 patients). Tomographic information (Sirius, Costruzione Strumenti Oftalmici, Italy) was processed using Matlab. The goodness of fit for each method was evaluated using mean squared error (MSE), measured at the same nodes where the elevation data were collected. Polynomial fitting based on NS-MVGA improves MSE values by 86% compared to LSQ-based methods in healthy patients. Moreover, this new method improves aberrated surface reconstruction by an average value of 56% if compared with LSQ-based methods in keratoconus patients. Finally, significant improvements were also found in morpho-geometric parameters, such as asphericity and corneal curvature radii. Full article

Background: Fitting of parametric model surfaces to corneal tomographic measurement data is required in order to extract characteristic surface parameters. The purpose of this study was to develop a method for evaluating the uncertainties in characteristic surface parameters using bootstrap techniques. Methods: We included 1684 measurements from a cataractous population performed with the tomographer Casia2. Both conoid and biconic surface models were fitted to the height data. The normalised fit error (height—reconstruction) was bootstrapped 100 times and added to the reconstructed height, extracting characteristic surface parameters (radii and asphericity for both cardinal meridians and axis of the flat meridian) for each bootstrap. The width of the 90% confidence interval of the 100 bootstraps was taken as uncertainty and quoted as a measure of the robustness of the surface fit. Results: As derived from bootstrapping, the mean uncertainty for the radii of curvature was 3 µm/7 µm for the conoid and 2.5 µm/3 µm for the biconic model for the corneal front/back surface, respectively. The corresponding uncertainties for the asphericity were 0.008/0.014 for the conoid and 0.001/0.001 for the biconic. The respective mean root mean squared fit error was systematically lower for the corneal front surface as compared to the back surface (1.4 µm/2.4 µm for the conoid and 1.4 µm/2.6 µm for the biconic). Conclusion: Bootstrapping techniques can be applied to extract uncertainties of characteristic model parameters and yield an estimate for robustness as an alternative to evaluating repeat measurements. Further studies are required to investigate whether bootstrap uncertainties accurately reproduce those from repeat measurement analysis. Full article

Herein, we discuss the synthesis, structural and spectroscopic characterization, and biological activity of five heteroligand copper(II) complexes with diethylnicotinamide and various fenamates, as follows: flufenamate (fluf), niflumate (nifl), tolfenamate (tolf), clonixinate (clon), mefenamate (mef) and N, N-diethylnicotinamide (dena). The complexes of composition: [Cu(fluf)₂(dena)₂(H₂O)₂] (1), [Cu(nifl)₂(dena)₂] (2), [Cu(tolf)₂(dena)₂(H₂O)₂] (3), [Cu(clon)₂(dena)₂] (4) and [Cu(mef)₂(dena)₂(H₂O)₂] (5), were synthesized, structurally (single-crystal X-ray diffraction) and spectroscopically characterized (IR, EA, UV-Vis and EPR). The studied complexes are monomeric, forming a distorted tetragonal bipyramidal stereochemistry around the central copper ion. The crystal structures of all five complexes were determined and refined with an aspheric model using the Hirshfeld atom refinement method. Hirshfeld surface analysis and fingerprint plots were used to investigate the intermolecular interactions in the crystalline state. The redox properties of the complexes were studied and evaluated via cyclic voltammetry. The complexes exhibited good superoxide scavenging activity as determined by an NBT assay along with a copper-based redox-cycling mechanism, resulting in the formation of ROS, which, in turn, predisposed the studied complexes for their anticancer activity. The ability of complexes 1–4 to interact with calf thymus DNA was investigated using absorption titrations, viscosity measurements and an ethidium-bromide-displacement-fluorescence-based method, suggesting mainly the intercalative binding of the complexes to DNA. The affinity of complexes 1–4 for bovine serum albumin was determined via fluorescence emission spectroscopy and was quantitatively characterized with the corresponding binding constants. The cytotoxic properties of complexes 1–4 were studied using the cancer cell lines A549, MCF-7 and U-118MG, as well as healthy MRC-5 cells. Complex 4 exhibited moderate anticancer activity on the MCF-7 cancer cells with IC₅₀ = 57 μM. Full article

A non-contact measurement method for measuring large aspheric surfaces with a laser tracker is proposed. Using an air-bearing probe eliminates the need to contact the optical surface and improves measurement efficiency and accuracy. Using this method, we measured the surface of an aspheric mirror 3 m in diameter and 13.6 m in the radius of curvature. The preliminary experimental result indicates that the error of surface measurement is 0.8 μm (RMS). Full article

With the rapid development of optical systems, aspheric reflective optics have become more and more widely used because of their advantages in obtaining better imaging quality. Meanwhile, the optical systems have higher requirements in terms of the surface precision of their optical elements. In this study, we proposed an improved profile-coating method to realize a two-dimensional surface correction method on a rotational symmetric hyperboloid mirror. This method used an irregular mask based on a planetary motion magnetron sputtering system to control film thickness distribution. Moreover, film thickness calibration with a step test was carried out to reduce the processing error of the mask. An optical profiler was used in the step test to quantitatively characterize film thickness distribution and a tilt correction was introduced to correct the test error. As a result, an improvement in figure error in the radial direction of 17.7 nm Root Mean Square (RMS) was achieved. According to these optimization methods, the mask was trimmed for film deposition on the spherical surface. Measurement results from the interferometer show that the figure error of film was 16.23 nm RMS, demonstrating the effectiveness of the optimized method for fabricating a rotational symmetric hyperboloid mirror. Full article

In order to verify the estimated wave-front ability of the phase retrieval, a method utilized in the measurement of the aspherical optical surfaces using the phase retrieval technology is described. This technique is based on the algorithm as a solution for the measurement of the aspherical optical surfaces, whose principle is sampling a number of the given defocus images and obtaining the phase information by solving the wave-front with Fourier optical diffractive theory and mathematics optimization. We set up an experimental arrangement used to measure the aspherical optical surfaces using the improved phase retrieval. In addition, we introduced the method of optical alignment in detail, which is very important for high-precision measurements. We obtained an agreement among the error distributions, the peak value, and the root-mean-square value of a ZYGO interferometer, which demonstrates that the improved phase retrieval method can effectively estimate the wave-front and the aberrations of aspherical optical surfaces. Full article

The tilted-wave interferometer (TWI) is a recent and promising technique for optically measuring aspheres and freeform surfaces and combines an elaborate experimental setup with sophisticated data analysis algorithms. There are, however, many parameters that influence its performance, and greater knowledge about the behavior of the TWI is needed before it can be established as a measurement standard. Virtual experiments are an appropriate tool for this purpose, and in this paper we present a digital twin of the TWI that was carefully designed for such experiments. The expensive numerical calculations involved combined with the existence of multiple influencing parameters limit the number of virtual experiments that are feasible, which poses a challenge to researchers. Experimental design is a statistical technique that allows virtual experiments to be planned such as to maximize information gain. We applied experimental design to virtual TWI experiments with the goal of identifying the main sources of uncertainty. The results from this work are presented here. Full article

An aspherical airborne camera has excellent performance in the field of photoelectric reconnaissance equipment. However, the image plane contrast of the optical system will be reduced by stray light originating from inside or outside of the optical system. In the present work, the self-designed aspheric airborne camera is manufactured with a baffle and vanes to reduce the impact of stray light on the camera imaging quality. TracePro software is used to analyze the stray light and establish an ABg mathematical model based on the scattering intensity measurement. The incident angle of the light parallel to the optical axis is set, and ray tracing is performed on the optical machine model to verify whether it conforms to the optical system design. The results showed that when the incident angle of the light source is greater than 0.5°, the point source transmittance (PST) value drops rapidly, and when the incident angle is 30°, the PST value of the system is in the order of 10⁻⁸. Stray light analysis verifies that the self-designed aspheric surface-based camera optomechanical structure has the ability to suppress stray light. The design of the baffle and vanes further enhances the ability of the optical system to suppress stray light, which can provide a reference for the design of a stray light elimination structure. Full article