ZEMAX Software Research Articles

Design and analysis of aspherical double-liquid lens based on planar electrode

In order to study an aspherical liquid lens with simple structure and easy realization, an aspherical double-liquid lens based on planar electrode is designed based on the dielectrophoretic effect. The droplet in the dielectric electrophoretic liquid lens is polarized in the electric field and moves towards the higher electric field strength under the action of the dielectrophoresis force. With the change of the applied voltage, the dielectrophoresis force also changes, thus the contact angle of the droplet at the solid-liquid interface changes. Firstly, the models of the aspherical double-liquid lens under different voltages are established with Comsol software, and the interfacial profile data are obtained. Then the aspherical coefficients and the surface type of the fitted interface are obtained with Matlab software. Finally, the corresponding optical model of double-liquid lens is established with Zemax software. The variable range of focal lengths and root mean square (RMS) radii of the aspherical double-liquid lens at different voltages are obtained. In order to further study the characteristics of the aspherical double-liquid lens, it is compared with a spherical double-liquid lens model. Based on the contact angle theory of liquid lens and Gaussian optics theory, the relationship between the interfacial curvature radius of the spherical liquid lens and the applied voltage, and the relationship between the focal length and the applied voltage are obtained, respectively. The liquid material, cavity structure and droplet are the same as those of the aspherical lens. The corresponding spherical double-liquid lens model is established according to the two expressions relating to Zemax, and the voltage value is the same as that of the aspherical lens. Thus, the variable ranges of focal length and RMS radius in the spot diagram of the spherical double-liquid lenses at different voltages are obtained. Then, they are compared with those of aspherical double-liquid lens, and the results show that the variable range of focal length of the aspherical double-liquid lens is larger than that of the spherical double-liquid lens, and the imaging quality of the former is better than that of the latter. Moreover, through the device fabrication and preliminary experimental analysis of the aspherical double-liquid lens, the imaging resolution can reach 40.318 lp/mm. The aspherical double-liquid lens proposed in this work has the characteristics of simple structure and easy realization, which can provide a new scheme for high-quality imaging of liquid lens and its applications, and can expand the application scope of liquid lens.

High precision ray tracing method for space camera in optical design

Ray tracing plays a key role in lens design area, and it is an important tool to study the problems in physics like optics. Nowadays, ray tracing becomes ubiquitous and is widely used in optical automatic design, such as aberration analysis, optimization, and tolerance calculation. With the impulse of application requirements, optical systems like space camera develop towards large scale, high degree of accuracy and complication. The magnitude of aberrations increases exponentially with the growth of focal length and aperture, even a minor perturbation error can result in severe degeneration of image quality. As a consequence, the stringent requirements for precision, accuracy and stability of ray tracing turn higher. Reliable commercial software, for example, America’s Zemax, has high precision in ray tracing, because of commercial purpose, the process of ray tracing is a black box. It is now more important to understand what error factors are formed for ray tracing, and how these running errors can be reduced effectively. In this paper, from floating point arithmetic perspective, an error model for ray tracing is provided. This error model is suitable for not only meridional rays, but also skew rays. Starting from IEEE Standard for Binary Floating-Point Arithmetic, presentation error and rounding error are analyzed, followed by the computation process of ray’s intersection point with a quadratic surface, then rounding error expression for the intersection point is presented. In addition, error expression for distance along the ray from the reference surface to the next surface is also induced. These two error expressions are called error model, and it clearly indicates that spatial coordinates on the reference surface, direction vector and distance between the two adjacent surfaces are the main error sources. Based on the error model, some of effective measures, for instance, reprojection, spatial transformation, and direction vector’s normalization are taken to reduce the rounding error. Moreover, in the process of solving quadratic equation, conjugate number method is utilized in order to avoid increasing substantially in relative error called catastrophic cancellation. Numerical experiments and classical optical design for space camera are also given. From numerical computing view, two precision tests based on Multiple Precision Floating-Point Reliable (MPFR) library are introduced to verify our method mathematically. The experimental results show that our algorithm has the same precision (14 significant digits) as MPFR, while the existing method fails to pass tests, and has only 8 significant digits at most. Moreover, both the Cassegrain space camera and off-axis three-mirror-anastigmat space camera are used to illustrate our method’s accuracy. Experimental results indicate that our method has higher precision, more than 5 to 6 orders of magnitudes than the existing method. In addition, our algorithm has higher precision than the commercial optical design software Zemax, and residuals are 3 orders of magnitudes on average less than Zemax.

Design of a digital PCR optical detection system with multiple fluorescent microdroplets.

The need for accurate nucleic acid testing is increasing with the spread of the global pandemic. Problems such as low efficiency and precision and large volume exist because the number of existing digital polymerase chain reaction (PCR) testing instrument channels is low. In order to solve these problems, a four channel micro drop digital PCR system was designed. The collimating lens set and objective lens of the LED light source are designed in ZEMAX software, and the entire optical path is simulated. It is verified that the light energy utilization rate of the system is over 93% and that stray light interference is marginal.

Ranging accuracy improvement by using a spiral phase plate in a time-of-flight underwater lidar system

We report on an investigation of spatial coherence filtering using a spiral phase plate (SPP) to reduce the amount of scattered light collected in an underwater lidar. This approach exploits the difference in spatial coherence between target-reflected light and scattered light as a means of separating and filtering out the multiple-scattered clutters. An underwater target was illuminated by a Gaussian beam, and both the target-reflected light and scattered light passed through an SPP. The spatially coherent target-reflected component formed a ring-shaped vortex beam, while the spatially incoherent scattered component was unaffected and remained a centrally stronger distribution obeying the Mie scattering law. A mask was placed behind the SPP which allowed only the light on the vortex ring to pass through. Therefore, an all-optical spatial coherence filter composed of an SPP and a mask provides an effective way to reject undesired scattered light without affecting the target-reflected light. A numerical simulation based on Zemax software was carried out and showed that the approach reduces the power of received scattered light without changing the power of received target-reflected light. Experimental results showed that the approach reduced the temporal broadening and excessive delay of the returned pulse caused by forward scattering, therefore reducing the ranging error. Moreover, using a vortex beam with a bigger topological charge improved the ranging accuracy more obviously, especially in turbid water. When the attenuation length was 12.5, by using a 40th-order SPP, the ranging error was reduced from 18 cm to 5.3 cm with a diffuse target.

Enhancement of a Single-Axis Femtosecond Laser Scanning System by Using Two Galvanometers to Improve the Telecentricity and the Effective Scanning Length on Laser Process

The galvanometer scanning system plays a crucial role in modern laser material processing. With the development of this industry, the requirements for galvanometer scanners are getting higher and higher, especially to overcome the inherent disadvantages that still exist, such as image distortion, marking speed and accuracy in state-of-the-art scanning systems. In this paper, a single-axis optical scanner using two galvanometers in combination with one f-theta telecentric lens and a 343 nm femtosecond pulse laser source is proposed as a new approach for enhancing the precision of laser micromachining technology. The additional second galvanometer is used to manipulate the output laser beam of the first galvanometer to the path with less lens aberration to enhance the telecentricity correction and the effective scanning area. This is based on the international standard regulation ISO (the International Organization for Standardization) 11145:2018 requirements in optics and photonics, in which an important criterion is for the roundness of the focused beam spot to be greater than 87% to determine the effective working length of the proposed scanning system compared to the conventional scanning system. It is demonstrated by optical simulations and real optical experiments that the effective working length can be increased by 3.6 mm, corresponding to 8.1% of the effective scanning field, to achieve a laser material processing system with ISO standard. The damped least squares (DLS) algorithm in optical design software ZEMAX is used to optimize the deflected angle of the two galvanometers to obtain the optimal incident position of the f-theta lens.

Optical Design of an Integrated Paschen–Runge Spectrometer by Using a Multigrating Structure

An integrated direct-reading spectrometer scheme using seven concave gratings is proposed. At present, the optical design simulation has been completed, and the subsequent physical design may be carried out according to the simulation results. Ray-tracing software (Zemax) is used to divide the spectrum on the grating into seven bands, and an area array detector is used to receive the spectral signals simultaneously, which reduces the volume of the spectrometer and improves the spectral consistency. Using this method, a spectrometer covering 230–440 nm is designed, and the spectral resolution of the center wavelength corresponding to the seven grating windows of 230–260 nm, 260–290 nm, 290–320 nm, 320–350 nm, 350–380 nm, 380–410 nm, and 410–440 nm can reach 0.0974 nm, 0.0652 nm, 0.0361 nm, 0.0157 nm, 0.0838 nm, 0.0872 nm, and 0.1471 nm.

Design of a measurement system for measuring geometric errors of a workpiece table during two-axis synchronous motion

With the increasing customer demand for high-precision workpieces, the accuracy performance of CNC machine tools has become an increasingly important hot topic for almost all machine tool manufacturers. For fine surface finish workpieces, the performance of multi-axis synchronous motion has a significant impact on lathe processing. Accordingly, it is necessary to calibrate and identify the geometric errors of the workpiece table during multiple-axis synchronous motion. Therefore, this study proposes a novel noncontact optical measurement system for measuring the geometric errors of the workpiece table while the two axes are moving simultaneously. In addition, the horizontal CNC lathe machine iTC-2000LM, produced by Tongtai machine & tool Co., Ltd., was taken as the research vehicle. The proposed measurement system comprises an optics module composed of several reflectors, lenses, and cubic beam splitters; a sensing module composed of multiple two-dimensional position-sensitive detectors (PSDs); and a laser. Based on the principle of geometric optics theory and the optical triangulation method, complete mathematical models that describe the geometric errors of the workpiece table during two-axis synchronous motion were established using the skew-ray tracing method. Additionally, the essential features of the proposed measurement system were verified using the optical design software Zemax. Finally, a laboratory prototype system was constructed to experimentally verify the proposed measurement system. As mentioned above, the main contribution of this study is to design a novel and highly efficient measurement system with established measurement mathematical models and experimental verifications.

Refractive shift prediction of DNA supramolecular hydrogels as artificial vitreous substitutes

Vitreous substitutes are sufficient for tamponade after pars plana vitrectomy. However, these substitutes (silicone oil and gas) are weak in the refractive aspect. DNA supramolecular hydrogel, a novel vitreous substitute, exhibits good biocompatibility. This study calculated the theoretical refractive shifts after the DNA supramolecular hydrogels were tamponed in the vitreous cavity in schematic eyes. Navarro and Liou–Brennan schematic eyes with relaxed accommodation were modeled using ZEMAX software. The refractive index representing the vitreous contents was changed to simulate a DNA supramolecular hydrogel tamponade in the vitreous cavity. The results of the theoretical refraction and power of the required spectacles to correct refractive error were output by the software. The same procedures were performed for other commonly used vitreous substitutes. The theoretical refractions of DNA supramolecular hydrogels were 60.368 and 60.189 D in Navarro and Liou–Brennan schematic eyes, which were only 0.229 and 0.154 D lower than that of the natural vitreous body, respectively. The power of the corresponding spectacles was less than 0.25 D. The refractive property of DNA supramolecular hydrogels was confirmed to be similar to that of a natural vitreous body. Hence, it is considered a promising vitreous substitute.

MEMS mirror based omnidirectional scanning for lidar optical systems

Lidar 3D vision system is currently one of the most effective technical means for high-precision perception of three-dimensional image information of the surrounding environment. Microelectron-mechanical systems (MEMS) micromirror lidar has advantages of miniaturization, fast scanning speed, and relatively low price. The MEMS micromirror scanning method has become the best choice for laser scanning 3D image sensors. However, due to the small size of the MEMS micromirror, it can only scan a small angle range, which limits its industrial applications. In this paper, combined with MEMS micro-mirror spiral scanning form, we design a new type of omnidirectional optical system that can realize MEMS lidar omnidirectional scanning imaging. The overall optical system is composed of the catadioptric prism, the MEMS micromirror, and the compensation prism. The overall system can achieve 360° omnidirectional scanning imaging with a horizontal resolution of 0.1°; a vertical field view with a 0.5° resolution. The design results are analyzed by the optical design software (Zemax). The point diagram shows that the emitted light spots are circular and evenly distributed. The divergence angle is less than 1mrad, which can well meet the actual needs and solve the problems of solid-state, miniaturization, and omnidirectional scanning imaging of lidar.

High-quality telecentric projection lens for vein visualization

Subject of study. A design of high-quality telecentric projection lenses that can be integrated into a miniprojector for projecting vein images onto human skin surfaces was investigated. Method. A numerical method based on Zemax software was used to design the lens. The required corrections were performed computationally to obtain a lens with components of similar diameter, significantly simplifying the mechanical structure, thus enabling easy and economical mass production. Main results. The new telecentric projection lens comprises seven spherical lenses, with a focal length and f-number of 20 mm and 2.51, respectively. The obtained value of the modulation transfer function (MTF) is extremely high: approximately 0.8 at 47 lines/mm and higher than 0.5 at 100 lines/mm. Relative distortion of the lens is less than 0.5% for the entire field of view. Owing to a unique technological feature, the fabricated projection lens demonstrated the measured MTF that was practically equal to the value calculated in the design. Practical significance. Using this projection lens in the vein finder enables the projection of sharp and precise images of veins onto the skin surface. Therefore, this device can help medical personnel in performing accurate and safe venipuncture. Owing to its low cost, compactness, and high quality of image formation, this projection lens is suitable for commercial purposes and for different applications of image formation.

Study the Field of View Influence on the Monchromatic and Polychromatic Image Quality of a Human Eye

In this paper, the effect of the eye field of view (known as F.O.V.) on the performance and quality of the image of the human eye is studied, analyzed, and presented in detail. The image quality of the retinal is numerically analyzed using the eye model of Liou and Brennan with this polymer contact lens. The image, which is in digital form were collected from various sources such as from photos, text structure, manuscripts, and graphics. These images were obtained from scanned documents or from a scene. The color fringing which is chromatic aberration addition to polychromatic effect was studied and analyzed. The Point Spreads Function or (known as PSF) as well as The Modulation Transfers Function (known as MTF) were measured as the most appropriate measure of image quality. The calculations of the image quality were made by using Zemax software. Then, the result of the calculation demonstrates the value of correcting the chromatic aberration. The results presented in this paper had shown that the form of image is so precise to the eye (F.O.V.). The image quality is degraded as (F.O.V.) increase due to the increment in spherical aberration and distortion aberration respectively. In conclusion, then Zemax software that was used in this study assist the researcher potential to design human eye and correct the aberration by using external optics.

An Off-Axis Flight Vision Display System Design Using Machine Learning

We propose an off-axis flight vision display system design with a free-form surface using machine learning to simulate the visual distance variation during take-off and landing training for pilots. This design is realized by ray tracing using ZEMAX software, where we build and optimize a series of initial systems that meet the corresponding optical specifications. A deep neural network is used to train the regression model, which is specifically designed to predict the fitted polynomial model for the free-form surface of the system. Our results demonstrate that the design of a flight visual display system can be transformed into a machine learning problem and further optimized by training and learning with abundant data, providing an avenue to design more powerful and complex imaging optical systems.

Analysis and Optimization of Acoustic Sensor Based on Fiber Fabry-Pérot Etalon

Fiber optic sensors have been extensively studied in recent years. Due to the advantages of high sensitivity, compact structure, and anti-electromagnetic interference, the sensors based on the Fabry-Pérot (FP) cavity have become a research hotspot. The Fabry-Pérot etalon (FPE) acoustic sensor consists of two Plano-Concave Lenses coated with a highly reflective film, the Graded Index Lenses (GRIN) lenses, the optical fibers and a glass tube. Acoustic detection is realized by detecting the small change in the refractive index of the cavity medium caused by sound pressure, and the phase modulation technology realizes the modulation and demodulation of the acoustic signal. Matlab is used to analyze the influence of refractive index changes on the resonance spectrum and sensitivity curve, so the cavity mirrors with the reflectivity of 99% are selected. The structure of the FPE sensor is optimized using Zemax software. The optimal length of the sensor is 29.973 mm and the diameter is 6 mm. The high quality factor values of experiment and simulation are both 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> . At the same time, the experimental results show that the sensor has a response in the range of 50 Hz-20 kHz, with a high Signal-to-Noise Ratio (SNR) of 61.97 dB when the sound pressure is 19.795 Pa, and the sensitivity response is linear, reaching 0.19013 V/Pa. The research results provide useful guidance for the optimal design of the sensor, and the correctness of the theory is verified by the performance test of the optical acoustic sensor.

Improved performance in microsphere-assisted 2D and 3D imaging by polystyrene microspheres semi-immersed in SU-8 resist

In this work, we introduce a method to improve the performance of microsphere-assisted imaging by optimizing the refractive index of immersion media. In the method, polystyrene (PS) microspheres are semi-immersed in water, spin-on-glass, SU-8 resist, and S1805 resist. We experimentally find that the distortion of the image observed by a PS microsphere semi-immersed in SU-8 resist is the smallest while the resolution of the semi-immersed microsphere is the highest. ZEMAX software simulations show that PS microspheres semi-immersed in SU-8 resist have the smallest distortion and spherical aberration. Moreover, numerical simulations also reveal that they have the strongest peak intensity, the narrowest waist, and the shortest focal length of the photonic nanojet. When the semi-immersed PS microsphere is used in microsphere-assisted microscopy, a 200-nm-diameter hexagonally close-packed (hcp) silica nanoparticle array can be clearly distinguished. When they are used in microsphere-assisted interference microscopy, a 250-nm-diameter hcp silica nanoparticle array can be resolved.

Realizing the imaging simulation of reflective polarization volume gratings.

Near-eye holographic waveguide display system using novel reflective polarized volume gratings (RPVG) have lately gotten a lot of interest. However, from polarization characteristics to imaging simulation, there is no systematic approach based on RPVG. Here, a full methodology for solving this problem using the rigorous coupled wave analysis (RCWA) model is presented. This self-built RCWA model is used to examine the optical behavior of RPVG. This excellent portability of the RCWA model makes it possible for RPVG as a diffractive optical element, which is integrated into the commercial optical software Zemax via a self-compiled dynamic link library (DLL), and a full-color imaging simulation of the based-RPVG waveguide display system is obtained. Our work provides an instructive imaging analysis method using the RPVG for holographic waveguide display.

Numerical Simulation of Performance Improvement of Underwater Lidar by Using a Spiral Phase Plate as Spatial Filter

In turbid water, target reflected lidar signal is easily buried in &#x201C;clutter&#x201D; due to scattering. We proposed an underwater laser ranging model applying an optical vortex in the receiver to separate the scattering clutter from the target reflected signal. A spiral phase plate (SPP) was placed in front of the detector to convert the target reflected Gaussian beam to an optical vortex. While the scattering clutters were not able to be converted due to the loss of spatial coherence. Therefore, the target reflected signal and scattering clutters were spatially separated by the SPP. An underwater laser detection simulation using Zemax software was carried out. The numerical simulation showed that when the SPP was placed in front of the receiver, the contrast of signal to clutter of the detection was improved by blocking the scattering clutters which had a Gaussian distribution at the center on the detection plane. The effects of beam divergence and orbital angular momentum (OAM) order to the lidar performance were also analyzed.

Design Study of a Large-Angle Optical Scanning System for MEMS LIDAR

MEMS-based LIDAR has the advantages of fast-scanning, simple structure, small volume, and light weight, which make it a hot topic for 3D imaging. In order to overcome the limited scanning angle of the current MEMS mirrors, a large angle MEMS-based optical scanning system was designed using telephoto structure. In this design an f-θ lens group is used for flat field scanning and a symmetrical cemented lens group is used for angle expansion. The principle of this system is discussed in detail and an optical design is implemented by ZEMAX software. The designed system realized a scanning angle as large as 57° and is in excellent linear relation with the tilt angle of the MEMS mirror. At the target distance of 100 m, the maximum RMS radius of the light spot is only 7 cm. This optical scanning system shows a significant application potentiality for 3D imaging LIDAR.

Simulation of photic effects after cataract surgery for off-axis light sources.

Photopsia is a phenomenon that sometimes disturbs patients after cataract surgery. To evaluate the impact of the edge design of intraocular lenses (IOL) on the location, shape and relative intensity of photic effects at the retina caused by photopsia in pseudophakic eyes, photopsia was simulated using ZEMAX software. The structural parameters of the pseudophakic eye model are based on the Liou-Brennan eye model parameters with a pupil diameter of 4.5 mm. The IOLs implanted in the eye model have a power of 21 diopter (D) with optical diameter of 6 mm and 7 mm. From the ray-tracing analysis, covering variations of incident ray angle of 50° to 90° from temporally, a photic image is detected at the fovea at specific ray angles of 77.5° (6 mm IOL) and 78.2° (7 mm IOL). This photic image disappears when a thin IOL with an edge thickness of 0 mm or a thick IOL with absorbing edges is replaced in the eye model. With an anti-reflective edge, this photic image remains, but with a fully reflecting edge it disappears at the critical angles and appears with different shapes at other angles. The intensity of this photic image can be reduced by changing the edge design to a frosted surface. Most of the photic patterns in IOLs are not observed with absorbing and thin edge designs. IOLs with anti-reflecting and fully reflecting edges generate disturbing photic effects at different angles on the fovea. IOLs with frosted edges reduce the contrast of the photic effects and make them less disturbing for patients.

Elliptical-Shaped Fresnel Lens Design through Gaussian Source Distribution

A novel three-dimensional elliptical-shaped Fresnel lens (ESFL) analytical model is presented to evaluate and maximize the solar energy concentration of Fresnel-lens-based solar concentrators. AutoCAD, Zemax and Ansys software were used for the ESFL design, performance evaluation and temperature calculation, respectively. Contrary to the previous modeling processes, based on the edge-ray principle with an acceptance half-angle of ±0.27° as the key defining parameter, the present model uses, instead, a Gaussian distribution to define the solar source in Zemax. The results were validated through the numerical analysis of published experimental data from a flat Fresnel lens. An in-depth study of the influence of several ESFL factors, such as focal length, arch height and aspect ratio, on its output performance is carried out. Moreover, the evaluation of the ESFL output performance as a function of the number/size of the grooves is also analyzed. Compared to the typical 1–16 grooves per millimeter reported in the previous literature, this mathematical parametric modeling allowed a substantial reduction in grooves/mm to 0.3–0.4, which may enable an easy mass production of ESFL. The concentrated solar distribution of the optimal ESFL configuration was then compared to that of the best flat Fresnel lens configuration, under the same focusing conditions. Due to the elliptical shape of the lens, the chromatic aberration effect was largely reduced, resulting in higher concentrated solar flux and temperature. Over 2360 K and 1360 K maximum temperatures were found for ESFL and flat Fresnel lenses, respectively, demonstrating the great potential of the three-dimensional curved-shaped Fresnel lens on renewable solar energy applications that require high concentrations of solar fluxes and temperatures.

Design of three-dimensional imaging lidar optical system for large field of view scanning

Three-dimensional (3D) lidar has been widely used in various fields. The MEMS scanning system is one of its most important components, while the limitation of scanning angle is the main obstacle to improve the demerit for its application in various fields. In this paper, a folded large field of view scanning optical system is proposed. The structure and parameters of the system are determined by theoretical derivation of ray tracing. The optical design software Zemax is used to design the system. After optimization, the final structure performs well in collimation and beam expansion. The results show that the scan angle can be expanded from ±5° to ±26.5°, and finally the parallel light scanning is realized. The spot diagram at a distance of 100 mm from the exit surface shows that the maximum radius of the spot is 0.506 mm with a uniformly distributed spot. The maximum radius of the spot at 100 m is 19 cm, and the diffusion angle is less than 2 mrad. The energy concentration in the spot range is greater than 90% with a high system energy concentration, and the parallelism is good. This design overcomes the shortcoming of the small mechanical scanning angle of the MEMS lidar, and has good performance in collimation and beam expansion. It provides a design method for large-scale application of MEMS lidar.