Accurate and fast narcissus calculation based on sequential ray trace

Eliminating back reflections is critical in the design of a fundus camera with internal illuminating system. As there is very little light reflected from the retina, even excellent antireflective coatings are not sufficient suppression of ghost reflections, therefore the number of surfaces in the common optics in illuminating and imaging paths shall be minimised. Typically a single aspheric objective is used. In the paper an alternative approach, an objective with all spherical surfaces, is presented. As more surfaces are required, more sophisticated method is needed to get rid of back reflections. Typically back reflections analysis, comprise treating subsequent objective surfaces as mirrors, and reflections from the objective surfaces are traced back through the imaging path. This approach can be applied in both sequential and nonsequential ray tracing. It is good enough for system check but not very suitable for early optimisation process in the optical system design phase. There are also available standard ghost control merit function operands in the sequential ray-trace, for example in Zemax system, but these don’t allow back ray-trace in an alternative optical path, illumination vs. imaging. What is proposed in the paper, is a complete method to incorporate ghost reflected energy into the raytracing system merit function for sequential mode which is more efficient in optimisation process. Although developed for the purpose of specific case of fundus camera, the method might be utilised in a wider range of applications where ghost control is critical.

The act of performing a sequential trigonometric ray trace through an optical system is as simple as applying Snell's Laws of refraction and reflection, along with some form of the grating equation, to the geometric description of the lenses and mirrors which can comprise that system. The orderly incorporation of these physical laws into an algorithm, which at the same time incorporates all possible geometries which may occur in this optical system, will be the result of this paper. The ray/surface equations and other useful numerical techniques will be spelled out in detail so that this paper can be used as a starting point for their own ray tracing program when commercial optical design codes are either not available or inappropriate.

Light Emitting Diode, LED, has many advantages in many lighting applications, such as general illumination, street light, and auto lamp. In general, each application needs to do secondary optical design for its specific request. A secondary optical element can be separated into refractive and reflective part. In this paper, we present a design procedure of secondary optical design with intensity distribution of LED and sequential ray tracing. The method suits the both designs of refractive and reflective parts. In the first process, we integrate the series function of intensity distribution in spherical coordinate with a range of solid angle. In the second process, we calculate the redistribution parameters of luminous flux by the geometric parameters of LED, element, and detector. In the final process, we use ray tracing method to design the optical element by aspheric surface. The surface of the refractive part in secondary optical element could be Fresnel surface for reducing the thickness of element. For proving the design procedure, we design a secondary optical element of LED by this method with an illumination request.

Raman spectroscopy is a powerful tool for analytical measurements in many applications. Traditional Raman spectroscopic analyses require bulky equipment, considerable time of signal acquisition and manual sampling of substances under test. In this paper, we take a step from bulky and manual consuming laboratory testing towards lab-on-chip (LOC) analyses. We miniaturize the Raman spectroscopic system by combining a free-form reflector based polymer LOC with a customized Raman probe. By using the confocal detection principle, we aim to enhance the detection of the Raman signals from the substance of interest due to the suppression of the background Raman signal from the polymer of the chip. Next to the LOC we miniaturize the external optical components, surrounding the reflector embedding optofluidic chip, and assemble these in a Raman probe. We evaluate the misalignment tolerance of internal optics (LOC) and external optics (Raman probe) by non-sequential ray tracing which shows that off-axis misalignment is around ±400μm and the maximum working distance of our Raman probe is 71mm. Using this probe, the system could be implemented as a portable reader unit containing the external optics, in which a low-cost, robust and mass manufacturable microfluidic LOC containing a freeform reflector is inserted, to enable confocal Raman spectroscopy measurements.

We revisit the question of hemispherical power asymmetry in the WMAP and Planck temperature sky maps by measuring the local variance over the sky and on disks of various sizes. For the 2013 Planck sky map we find that none of the 1000 available isotropic Planck "Full Focal Plane" simulations have a larger variance asymmetry than that estimated from the data, suggesting the presence of an anisotropic signature formally significant at least at the $3.3\sigma$ level. For the WMAP 9-year data we find that 5 out of 1000 simulations have a larger asymmetry. The preferred direction for the asymmetry from the Planck data is $(l,b)=(212^\circ,-13^\circ)$, in good agreement with previous reports of the same hemispherical power asymmetry.

The goal of an in situ Long Trace Profiler (LTP) is to adjust the mirror to 0.1 μrad Root Mean Square (RMS) under thermal load. Here we introduce the measurement configuration for in situ LTP. To avoid lens aberration, the moving optical head keeps the optical paths constant, and the reference beam is used to the correct of the unavoidable air bearing errors. The window glass in this test has a rather high optical quality, with a flatness of 1/150 (RMS) over 120 × 20 mm. The optical quality of the window was specified to be ± 1 μrad slope distortion in an aperture length of 100 mm. The window glass deformation for the air pressure was calculated by the Finite Element Method (FEM) software (ANSYS). The window glass deformation results can be fitting by the Zernike polynomial, and then bring it into the sequential optical ray tracing software (ZEMAX), and evaluating the window glass effect on the LTP measurement results. By this approach, we found that this has a constant error. Thus, the window glass air pressure error can be effectively removed from the measurement result to reveal the real mirror profile. Using the in situ LTP measuring result and the data iteration process, the bendable mirror can control the optical surface locate profile and thereby minimize the thermal distort effect. The slope error will be reduced to 0.1 μrad at the thermal load.

We present in this work a numerical model for characterizing the scattering properties of the human lens. After analyzing the scattering properties of two main scattering particles actually described in the literature through FEM (finite element method) simulations, we have modified a Monte Carlo's bulk scattering algorithm for computing ray scattering in non-sequential ray tracing. We have implemented this ray scattering algorithm in a layered model of the human lens in order to calculate the scattering properties of the whole lens. We have tested our algorithm by simulating the classic experiment carried out by Van der Berg et al for measuring "in vitro" the angular distribution of forward scattered light by the human lens. The results show the ability of our model to simulate accurately the scattering properties of the human lens.

The motivation for Vehicular Visible Light Communication (VVLC) is the demand for automotive communication and the restricted bandwidth of Radio Frequency (RF) systems. VLC is a potential possibility for Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) Connectivity due to the wide use of Light-Emitting Diodes (LEDs). Within this work, a novel low-beam headlamp designed adheres to the ECE R112 standard. The proposed design comprises the LED, ellipsoid reflector, mirror, baffle, and lens from which the optical path and power are determined with the help of non-sequential ray tracing. After importing this data into MATLAB, the relevant Channel Impulse Response (CIR) and accurate path loss are determined. The total luminous intensity from the proposed headlamp is 308.5 lm, and the overall effectiveness is 56.13%. This non-sequential ray tracing result is analyzed in comparison with the path loss model proposed and a linear model. The proposed path loss obtained for this headlamp is -56 dB, approximately 14 dB less than the Lambertian model.

Focus on software

A nonsequential ray tracing method is described for treating systems where the order in which surfaces are hit depends on the ray being traced. These include systems with segmented mirrors and/or apertures, various types of prisms, e.g. corner cube reflectors and roof prisms, and systems containing concentrating collectors, waveguides, and resonators. Nonsequential (NS) surfaces are entered in any order using global coordinates, and can be nested with sequential surface subsystems. The material on both sides of each surface must be specified, as well as the refractive mode (i.e., whether a ray is to reflect, refract, or do either depending on whether or not the ray satisfies the conditions for total internal reflection). Analyses of selected systems using the Code VTM optical design program are presented as examples of this technique.

The Multi-Channel Photometric Survey Telescope (Mephisto) is a wide-field ground-based telescope with a 1.6 m primary mirror and 2◦ field of view (FOV). The telescope is capable of synchronous photometric imaging in blue, yellow, and red channels covering a wavelength range from 320 nm to 1000 nm by using large cubic splitters with dichroic coatings. A high-accuracy photometric survey requires higher requirements for the transmittance and reflectance of dichroic coatings. However, the light ray incident angle on the cubic splitter surface is 45°±6°, and the refractive index difference between the p-component and s-component of incident light causes an obvious p/s efficiency difference of both the reflection and transmission through the cubic, which will introduce extra error on the photometric accuracy. This paper proposes an effective method to calculate the uniformity of the imaging efficiency of the Mephisto. By sampling on the pupil plane with each FOV, the efficiency of each light ray can be calculated by the curve fitting method. The efficiency difference over the full focal plane is less than 2.5%, 1.5%, and 0.5% for the blue channel, yellow channel, and red channel respectively, introduced by the cube dichroic coatings and the filters, which can be used for the calibration. The method paves the way to solve coating uniformity for large aperture telescopes.

The Atacama Cosmology Telescope Polarimeter (ACTPol) is a polarization sensitive receiver for the 6-m Atacama Cosmology Telescope (ACT) and measures the small angular scale polarization anisotropies in the cosmic microwave background (CMB). The full focal plane is composed of three detector arrays, containing over 3000 transition edge sensors (TES detectors) in total. The first two detector arrays, observing at 146 GHz, were deployed in 2013 and 2014, respectively. The third and final array is composed of multichroic pixels sensitive to both 90 and 146 GHz and saw first light in February 2015. Fabricated at NIST, this dichroic array consists of 255 pixels, with a total of 1020 polarization sensitive bolometers and is coupled to the telescope with a monolithic array of broad-band silicon feedhorns. The detectors are read out using time-division SQUID multiplexing and cooled by a dilution refrigerator at 110 mK. We present an overview of the assembly and characterization of this multichroic array in the lab, and the initial detector performance in Chile. The detector array has a TES detector electrical yield of 85 %, a total array sensitivity of less than 10 $$\upmu $$ K $$\sqrt{\text {s}}$$ , and detector time constants and saturation powers suitable for ACT CMB observations.

This paper presents a simulation approach, with which results on multimode bending couplers are obtained much faster than with traditional methods. This is achieved by a two-stage simulation combining ray tracing and beam propagation method. Using this approach, design rules can be obtained faster with a simultaneous cross-check of the results. Hence, a more reliable prediction is achieved. The main challenge in the presented example is the exact ray tracing simulation of curved waveguides with program-own methods without selfprogrammed routines, which is solved by interlaced cylindrical volumes. Prior to the simulation approach, upcoming requirements for photonic networks for internet of things and industry 4.0 applications are discussed. Due to that, a paradigm shift - away from the traditional packaging levels to the new definition of device communication - is proposed in this work.

Ray tracing is an attractive technique for visualizing scientific data because it can produce high quality images that faithfully represent physically-based phenomena. Its embarrassingly parallel reputation makes it a natural candidate for visualizing large data sets on distributed memory clusters, especially for machines without specialized graphics hardware. Unfortunately, the traditional recursive ray tracing algorithm is exceptionally memory inefficient on large data, especially when using a shading model that generates incoherent secondary rays. As visualization moves through the petascale to the exascale, disk and memory efficiency will become increasingly important for performance, and traditional methods are inadequate. This paper presents a dynamic ray scheduling algorithm that effectively manages both ray state and data accesses. Our algorithm can render datasets that are larger than aggregate system memory, which existing statically scheduled ray tracers cannot render. For example, using 1024 cores of a supercomputing cluster, our unoptimized algorithm ray traces a 650GB dataset from an N-Body simulation with shadows and reflections, at about 1100 seconds per frame. For smaller problems that fit in aggregate memory, but are larger than typical shared memory, our algorithm is competitive with the best static scheduling algorithm.

The simulation of micro-optical systems, especially those including microlens arrays, is still a challenging task. There are of course traditional methods which can be applied under certain circumstances. This paper will discuss several geometrical optical and diffraction-based methods for the simulation of micro-optical systems. A simple paraxial geometrical optical matrix theory will be extended to the simulation of off-axis optical elements. Ray tracing will be used to model incoherent micro-optical systems. The propagation of Gaussian beams through off-axis optical systems using differential ray tracing will be discussed. The angular spectrum of plane waves will be used to propagate a scalar complex wave amplitude in free space simulating non-paraxial diffraction effects. Finally, a model will be proposed which combines ray tracing and wave propagation methods by converting a complex wave amplitude into rays and vice versa. In the case of wavefront warping a decomposition of the wave into elementary waves has to be performed. This combined model can take into account non-paraxial effects such as aberrations of optical elements and also diffraction effects.