Zemax Simulation Research Articles

Novel Electrochemical Raman Spectroscopy Enabled by Water Immersion Objective.

Electrochemical Raman spectroscopy is a powerful molecular level diagnostic technique for in situ investigation of adsorption and reactions on various material surfaces. However, there is still a big room to improve the optical path to meet the increasing request of higher detection sensitivity and spatial resolution. Herein, we proposed a novel electrochemical Raman setup based on a water immersion objective. It dramatically reduces mismatch of the refractive index in the light path. Consequently, significant improvement in detection sensitivity and spatial resolution has been achieved from both Zemax simulation and the experimental results. Furthermore, the thickness of electrolyte layer could be expanded to 2 mm without any influence on the signal collection. Such a thick electrolyte layer allows a much normal electrochemical response during the spectroelectrochemical investigations of the methanol oxidation.

Design of a fiber-optic multiphoton microscopy handheld probe.

We have developed a fiber-optic multiphoton microscopy (MPM) system with handheld probe using femtosecond fiber laser. Here we present the detailed optical design and analysis of the handheld probe. The optical systems using Lightpath 352140 and 352150 as objective lens were analyzed. A custom objective module that includes Lightpath 355392 and two customized corrective lenses was designed. Their performances were compared by wavefront error, field curvature, astigmatism, F-θ error, and tolerance in Zemax simulation. Tolerance analysis predicted the focal spot size to be 1.13, 1.19 and 0.83 µm, respectively. Lightpath 352140 and 352150 were implemented in experiment and the measured lateral resolution was 1.22 and 1.3 µm, respectively, which matched with the prediction. MPM imaging by the handheld probe were conducted on leaf, fish scale and rat tail tendon. The MPM resolution can potentially be improved by the custom objective module.

Free-form surface design method for nonaxial-symmetrical reflectors producing arbitrary image patterns

A free-form (FF) surface design method is proposed for a nonaxial-symmetrical projector system comprising an FF reflector and a light source. The profile of the reflector is designed using a nonaxial-symmetrical FF (NFF) surface construction method such that each incident ray is directed in such a way as to form a user-specified image pattern on the target region of the image plane. The light ray paths within the projection system are analyzed using an exact analytical model and a skew-ray tracing approach. The validity of the proposed NFF design method is demonstrated by means of ZEMAX simulations. It is shown that the image pattern formed on the target region of the image plane is in good agreement with that specified by the user. The NFF method is mathematically straightforward and easily implemented in computer code. As such, it provides a useful tool for the design and analysis stages of optical systems design.

Design of free-form reflector for vehicle LED low-beam headlamp

A method is proposed for the design of a vehicle low-beam headlamp system comprising a reflector and an LED light source. In the proposed approach, the profile of the reflector is designed using a free-form (FF) surface construction method such that each incident ray is directed in such a way as to form a user-specified light pattern on the measuring plane. The light ray paths within the headlamp system are analyzed using an exact analytical model and a skew-ray tracing approach. The validity of the proposed FF design method is demonstrated by means of ZEMAX simulations. It is shown that the light pattern formed on the measuring plane is in good agreement with the target pattern specified by ECE R112. The FF design method is mathematically straightforward and easily implemented in computer code. As such, it provides a useful tool for the design and analysis tasks in optical systems design.

Free-form surface design method for a collimator TIR lens.

A free-form (FF) surface design method is proposed for a general axial-symmetrical collimator system consisting of a light source and a total internal reflection lens with two coupled FF boundary surfaces. The profiles of the boundary surfaces are designed using a FF surface construction method such that each incident ray is directed (refracted and reflected) in such a way as to form a specified image pattern on the target plane. The light ray paths within the system are analyzed using an exact analytical model and a skew-ray tracing approach. In addition, the validity of the proposed FF design method is demonstrated by means of ZEMAX simulations. It is shown that the illumination distribution formed on the target plane is in good agreement with that specified by the user. The proposed surface construction method is mathematically straightforward and easily implemented in computer code. As such, it provides a useful tool for the design and analysis of general axial-symmetrical optical systems.

Design and Performance of a Focus-Detection System for Use in Laser Micromachining

We describe a new approach for locating the focal position in laser micromachining. This approach is based on a feedback system that uses a charge-coupled device (CCD) camera, a beam splitter, and a mirror to focus a laser beam on the surface of a work piece. We tested the proposed method for locating the focal position by using Zemax simulations, as well as physically carrying out drilling processes. Compared with conventional methods, this approach is advantageous because: the implementation is simple, the specimen can easily be positioned at the focal position, and the dynamically adjustable scan amplitude and the CCD camera can be used to monitor the laser beam’s profile. The proposed technique will be particularly useful for locating the focal position on any surface in laser micromachining.

Developing a contact probe for rodent fundus imaging in a confocal scanning laser ophthalmoscope

Since significant ocular differences in both anatomical structure and optical properties exist between rodents and humans, clinical imaging devices for human use are not suitable for use on rodents. In this study, we develop a contact probe with a flexible surface that can closely fit the rodent cornea for fundus imaging with a confocal scanning laser ophthalmoscope. Both Zemax simulation and in vivo fundus imaging demonstrate that this contact probe can significantly improve both the imaging quality and the operational convenience.

High-quality and controllable hollow beam generation by a liquid-core optical fiber

We present the generation of high-quality and beam parameter controllable hollow beams with a liquid-core optical fiber (LCOF) filled with CS2 by adjusting off-axis orientation and LCOF structure. The dependences of the dark spot size (DSS), ring beam width (RBW) and transverse field intensity distribution of the hollow beam on the incidence angle of laser beam, the length and core diameter of the LCOF are investigated experimentally, and analyzed theoretically by using Zemax simulation. The results show that the quality of the hollow beam is related to the times of total internal reflection of skew rays in the fiber core; the DSS and RBW are closely controlled by the incidence angle and core diameter. High-quality thin-ring hollow beam is achieved experimentally by the LCOF of the core diameter of 100μm and the length of 1m with the incidence angle of less than 10°. The hollow beam generated has high stability, and is weakly dependent on the bending of the LCOF.

Jet printing of convex and concave polymer micro-lenses.

We describe a novel approach for fabricating customized convex as well as concave micro-lenses using substrates with sophisticated pinning architecture and utilizing a drop-on-demand jet printer. The polymeric lens material deposited on the wafer is cured by UV light irradiation yielding lenses with high quality surfaces. Surface shape and roughness of the cured polymer lenses are characterized by white light interferometry. Their optical quality is demonstrated by imaging an USAF1951 test chart. The evaluated modulation transfer function is compared to Zemax simulations as a benchmark for the fabricated lenses.

Design and characterization of high-performance autofocusing microscope with zoom in/out functions

Autofocusing is a critical function in on-line or off-line automated vision inspection in the manufacturing fields. Accordingly, design of high-performance autofocusing microscopes is an important issue. The present group recently developed a novel laser-based autofocusing microscope comprising two optical paths, which provided a large linear autofocusing range and a rapid response with no reduction in the focusing accuracy (Liu et al. in Appl Phys B 109:259–268, 2012). In the present study, the focusing response of the developed autofocusing microscope is further improved by replacing the two optical paths with one tunable optical zoom system. The proposed autofocusing microscope is characterized numerically by means of commercial software ZEMAX simulations and is then verified experimentally using a laboratory-built prototype. The simulation and experimental results show that compared to the developed autofocusing microscope with two optical paths, the proposed autofocusing microscope achieves a rapid focusing response (less than 3.5 s) under the same autofocusing range (±1500 μm) and focusing accuracy (focusing accuracy of ≤1 μm, repeatability of ±1 μm). Consequently, it confirms the proposed autofocusing microscope has potential for automated vision inspection and optical applications.

Simulation, fabrication, and characterization of a tunable electrowetting-based lens with a wedge-shaped PDMS dielectric layer

Microlenses with tunable focal length have wide applications in optofluidic devices. This work presents a numerical and experimental investigation on a tunable electrowetting-based concave lens. Optical properties such as focal length of the lens and visibility of images were investigated numerically and experimentally. A finite element analysis and a ZEMAX simulation were used for determination of surface profile and focal length of the lens. The results show that the theoretical surface profile and focal length of the lens are in good agreement with the experimental ones. The lens has a wide tuning focal length equal to 6.5 (cm). Because the polydimethylsiloxane (PDMS) layer is wedge shaped (as both the dielectric and hydrophobic layers), lower applied voltage is needed. A commercial program was used to find the focal length of the lens from maximum visibility value by tuning the applied voltage.

Design and experimental validation of novel enhanced-performance autofocusing microscope

Autofocusing is a critical operation in automated microscopy applications in the automated vision inspection, measurement and manufacturing fields. The present group recently developed a novel optics-based autofocusing microscope incorporating two achromatic lenses, which provided a large linear autofocusing range, a rapid response, and a high focusing accuracy (Liu et al. in Appl Phys B 109:259–268, 2012). In the present study, the focusing accuracy of the microscope is further improved by replacing the two achromatic lenses with two cylindrical lens assemblies. The autofocusing performance of the modified microscope is characterized numerically by means of ZEMAX simulations and is then verified experimentally using a laboratory-built prototype. The experimental results confirm that compared with the original microscope with achromatic lenses, the modified microscope achieves a greater focusing accuracy (focusing accuracy of ≤1 μm, repeatability of ±1 μm).

Zemax Simulations of Transition and Diffraction Radiation

Charged particle beam diagnostics is a key task in modern and future accelerator installations. The diagnostic tools are practically the "eyes" of the operators. Precision and resolution of the diagnostic equipment are crucial to define the performance. Transition and Diffraction Radiation (TR and DR) are widely used for electron beam parameter monitoring. However, the precision and resolution of those devices are determined by how well the production, transportation and detection of these phenomena are understood. This paper reports on initial simulations of TR and DR spatial characteristics. A good consistency with theory is demonstrated. Also, optical system alignment issues are discussed.

Common-Path Optical Coherence Tomography Using a Conical-Frustum-Tip Fiber Probe

We demonstrated an in-fiber common-path optical coherence tomography (OCT) system using a conical-frustum-tip fiber probe. The probe had a circularly truncated conical shape to increase reflection of reference light while preserving focus without additional lens components. We analyzed the intensity of reference light back-reflected from the probe using a ZEMAX simulation, and the optimal height of the conical-frustum lens was 1.0 μm. Compared to various other types of conical-frustum-tip fiber probes, the probe in this paper showed the best lateral resolution with a relatively high reflectivity. Experimental results are compared to simulations. This conical-frustum-tip probe provided a 3.7 times larger reflectivity than a conventional conical lens. Due to the increased reflection, the signal-to-noise ratio (SNR) of an OCT image was enhanced by up to 5.6 dB. Furthermore, the lateral resolution was less than 4.4 μm as verified by B-scan profiles of a resolution target card. This probe can be utilized as a forward-viewing endoscopic probe to enhance OCT image quality through an increase in SNR, sensitivity, a small size, and effective focusing without additional lens components.

Design and Optimization of 2D Laser Source Module for Compact Projector

In order to make projector compact and efficient, we propose that the 2D laser source module is consisted of VCSEL array and micro-lens array. It describes packaging structure design of VCSEL array and thermal resistance calculation. A thermal 3D analysis of 3 ×3 array based on the finite-element method (FEM) is presented. The analysis shows that the maximum internal temperature of a VCSEL array reaches 51°C. Then, it describes the principle of the micro-lens array. By ZEMAX simulation, in the micro-lens array illumination system, we have got the energy efficiency 67.3%, the light uniformity is 95.5%, respectively, on the micro-display chip at the distance of 65 mm. We have successfully built the complete 3-LCOS projection system based on the 2D source module. It can provide 1362 lm D65 light, and its total volume is 260 × 200 × 160 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> which is more compact than the commercial projector.

Enhanced irradiance distribution on solar cell using optimized variable-focus-parabolic concentrator

A solar cell concentrator system is proposed comprising a square solar cell and a variable-focus-parabolic (VFP) reflector in which the focal length varies as a function of the horizontal displacement of the incidence point relative to the vertical centerline of the solar cell. The light ray paths within the concentrator system are analyzed using an exact analytical model and a skew-ray tracing approach. The geometry of the VFP reflector is then optimized in such a way as to maximize the uniformity of the irradiance distribution on the solar cell given a circular focus spot and a square focus spot, respectively. The effectiveness of the optimized VFP reflector with a square focus spot is investigated by means of ZEMAX simulations. It is shown that the optimized VFP concentrator yields a significant improvement in the irradiance uniformity compared to that achieved using a conventional parabolic concentrator.

Design and analysis of reflector for uniform light-emitting diode illuminance

A light-emitting diode (LED) projection system is proposed, composed of an LED chip and a variable-focus-parabolic (VFP) reflector, in which the focal length varies as a function of the vertical displacement of the incidence point relative to the horizontal centerline of the LED chip. The light-ray paths within the projection system are analyzed using an exact analytical model and a skew-ray tracing approach. The profile of the proposed VFP reflector and the position of the LED chip are then optimized in such a way as to enhance the uniformity of the illuminance distribution on the target region of the image plane. The validity of the optimized design is demonstrated by means of ZEMAX simulations. It is shown that the optimized VFP projector system yields a significant improvement in illuminance uniformity compared to conventional spherical and parabolic projectors and therefore minimizes the glare effect.

An Optomechanical Model Eye for Ophthalmological Refractive Studies

To create an accurate, low-cost optomechanical model eye for investigation of refractive errors in clinical and basic research studies. An optomechanical fluid-filled eye model with dimensions consistent with the human eye was designed and fabricated. Optical simulations were performed on the optomechanical eye model, and the quantified resolution and refractive errors were compared with the widely used Navarro eye model using the ray-tracing software ZEMAX (Radiant Zemax, Redmond, WA). The resolution of the physical optomechanical eye model was then quantified with a complementary metal-oxide semiconductor imager using the image resolution software SFR Plus (Imatest, Boulder, CO). Refractive, manufacturing, and assembling errors were also assessed. A refractive intraocular lens (IOL) and a diffractive IOL were added to the optomechanical eye model for tests and analyses of a 1951 U.S. Air Force target chart. Resolution and aberrations of the optomechanical eye model and the Navarro eye model were qualitatively similar in ZEMAX simulations. Experimental testing found that the optomechanical eye model reproduced properties pertinent to human eyes, including resolution better than 20/20 visual acuity and a decrease in resolution as the field of view increased in size. The IOLs were also integrated into the optomechanical eye model to image objects at distances of 15, 10, and 3 feet, and they indicated a resolution of 22.8 cycles per degree at 15 feet. A life-sized optomechanical eye model with the flexibility to be patient-specific was designed and constructed. The model had the resolution of a healthy human eye and recreated normal refractive errors. This model may be useful in the evaluation of IOLs for cataract surgery.

Irregular surfaces - measurements and ZEMAX simulations

Surfaces produced on optical elements are loaded by different kinds of irregularities whose allowable amplitudes are prescribed by optical tolerances defined by an optical designer. An important feedback between realized and designed surfaces can be achieved using interferometry or profilometry measurements for instance. This article discusses different kinds of representation and visualization of those measurements in ZEMAX, enabling optical designer to evaluate an impact of the irregular surface on the optical system performance.

Aspheric spectacles for correcting presbyopia with myopia and astigmatism

The aim of this paper is to propose a method for designing aspheric spectacles capable of realizing good optical performance at both far and near vision for presbyopia. We have experimentally measured wavefront aberrations and axial lengths for eight myopic eyes. In consideration of the field of view (FOV), the rotation of the eyeball, and a small amount of accommodation retained for presbyopia, we constructed individual eye models and optimized all the spectacle-eye systems for visible wavelengths by Zemax's simulation. Finally, we evaluated the image quality by the modulation transfer function (MTF) and visual acuity (VA) with different pupil sizes (2, 2.8, 4 mm). Results show that when the pupil size is 2 mm or 2.8 mm, the spectacles designed for the full FOV (0° and ±4° FOV) provide a strong ability to transfer low contrast at both far and near vision, and the VA for all reaches 0.8, and up to 1.1 for eyes NO. 1, NO. 5, NO. 6, and NO. 8 for the 0° FOV. As the pupil size increases to 4 mm, the VA for all comes to 0.6 for the full FOV, indicating that presbyopia is able to acquire a good visual resolution at both far and near vision by the designed aspheric spectacles. Furthermore, we verified the visual continuity of the spectacle-eye systems by studying intermediate vision, which demonstrates that the method used in our design is accurate and practicable.