Mathematical models are used to establish the exact path of a beam reflected by a plane mirror in terms of the mirror geometry descriptors. In particular, the mirror geometry descriptors (tilt angles) are determined as functions of the beam path in image space. This is also useful for determining scan patterns when the mirror is used as a scanning device. These formulations are readily adaptable to commercially available ray tracing programs.

In this paper, we present nonlinear pressure dynamics as an extension to a linear distributed parameters model of a deformable mirror. The original, undamped model is recalled and measurement results are shown supporting the need for a damping model which includes the pressure dynamics of the air gap behind the mirror membrane. We will derive the damping coefficients to match our measurement results. Based on the mew model, we will derive a modal feedforward and feedback control law for 88 actuators based on only 3 position sensors and show simulation results to support the algorithm's effectiveness.

Stereophotogrammetry typically employs a pair of cameras, or a single moving camera, to acquire pairs of images from different camera positions, in order to create a three dimensional ‘range map’ of the area being observed. Applications of this technique for building three-dimensional shape models include aerial surveying, remote sensing, machine vision, and robotics. Factors that would be expected to affect the quality of the range maps include the projection function (distortion) of the lenses and the contrast (modulation) and signal-to-noise ratio (SNR) of the acquired image pairs. Basic models of the precision with which the range can be measured assume a pinhole-camera model of the geometry, i.e. that the lenses provide perspective projection with zero distortion. Very-wide-angle or ‘fisheye’ lenses, however (for e.g. those used by robotic vehicles) typically exhibit projection functions that differ significantly from this assumption. To predict the stereophotogrammetric range precision for such applications, we extend the model to the case of an equidistant lens projection function suitable for a very-wide-angle lens. To predict the effects of contrast and SNR on range precision, we perform numerical simulations using stereo image pairs acquired by a stereo camera pair on NASA’s Mars rover Curiosity. Contrast is degraded and noise is added to these data in a controlled fashion and the effects on the quality of the resulting range maps are assessed.

Wide field of view optics paired with large starer infrared detector arrays can be notoriously difficult to place into focus. This paper will discuss the lessons learned in taking one such system from being more than 20x out of its focus specification to within focus in a single iteration. Traditionally the tight tolerances required for space borne applications forces the system designer to carefully consider many effects that may otherwise be negligible. These include changes in system tolerances between ambient to cryogenic temperature, lens boule property differences, test setup to properly mimic the flight thermal profile, lack of commercially available lasers with the proper wavelength, and several others. In this case, some key pieces of information were not provided when the system arrived at Northrop Grumman’s Azusa facility for unit integration and through-focus testing. The presented approach involves taking extremely out-of-focus responses from point sources at various focus positions and combining them with optical modeling parameters to determine how to best reposition the detector array to the best plane of focus. A successful implementation of the approach will be presented using data from a wide field-of-view infrared sensor.

Color aberrations in broadband imaging optics can be effectively corrected for by use of diffractive optical elements (DOE) such as kinoforms. Typically, the DOE groove width increases with wavelength range and is in the range of several ten to several hundreds of micrometers. Since the footprint diameter of a light bundle originating from a single object point at the diffractive surface is often in the range of millimeters, the number of grooves crossed by this light bundle can be small. In addition, the groove width varies and the grooves are curved. For DOE optimization and prediction of optical performance, optical design software is widely used being based on the ray trace formula, i. e. the law of refraction including DOEs. This ray trace formula relies on two assumptions. First, the footprint diameter of a light beam at the diffractive surface is assumed to be large compared to the groove width. Second, the local grating approximation is used saying that at the footprint area the groove width is constant and the grooves are straight lines. In realistic optical systems, these assumptions are often violated. Thus, the reliability of optical performance predictions such as MTF is in question. In the present paper, the authors re-examine the limits of the ray trace equation. The effect of a finite footprint diameter at the diffractive surface is investigated as well as variations of the groove width. Also, the Fraunhofer diffraction pattern of a light bundle after crossing a grating with a finite number of grooves is calculated.

The Point Spread Function (PSF) indirectly encodes the wavefront aberrations of an optical system and therefore is a metric of the system performance. Analysis of the PSF properties is useful in the case of diffractive optics where the wavefront emerging from the exit pupil is not necessarily continuous and consequently not well represented by traditional wavefront error descriptors such as Zernike polynomials. The discontinuities in the wavefront from diffractive optics occur in cases where step heights in the element are not multiples of the illumination wavelength. Examples include binary or N-step structures, multifocal elements where two or more foci are intentionally created or cases where other wavelengths besides the design wavelength are used. Here, a technique for expanding the electric field amplitude of the PSF into a series of orthogonal functions is explored. The expansion coefficients provide insight into the diffraction efficiency and aberration content of diffractive optical elements. Furthermore, this technique is more broadly applicable to elements with a finite number of diffractive zones, as well as decentered patterns.

This paper focuses on polarization imaging during optical clearing process in tissues due to refractive index matching of tissue structural components. We start with some single-dispersed tissue models, composed of large spheres, small spheres, and large cylinders, respectively. Along with the simulated refractive index matching inside and outside the scatterers, the linear polarized incident photons show similar decreased depolarization. It is worth noting that the circular polarized incident light show different polarization change for different scatterers, sensitive to scatterer size and shape. For small Rayleigh-like spherical scatterers, the circular depolarization also decreases with index matching. However, the depolarization by the larger scatterers can be enhanced, supported by the photon distribution change with the index matching in the backward detection. After some extreme points, the depolarization of circular polarized photons will be suppressed until almost disappear. Furthermore, by the simulation of hybrid-dispersed models, we can find out that the transmission of circular polarized photons during optical clearing, is more sensitive to the content of smaller scatterers in the turbid medium, and also has a close relationship with the proportion of the anisotropic scatterers. We also extract a character to describe the difference of linear and circular polarized photons. The value and the change of this character can help us to explain the main scatterers contributed to the polarization features of tissue-like medium during optical clearing. The above results indicate different polarization features for different scattering systems by optical clearing, which are potentially useful for studying optical clearing by polarization methods.

Performance-related effects of system level temperature changes can be a key consideration in the design of many types of optical instruments. This is especially true for space-based imagers, which may require complex thermal control systems to maintain alignment of the optical components. Structural-Thermal-Optical-Performance (STOP) analysis is a multi-disciplinary process that can be used to assess the performance of these optical systems when subjected to the expected design environment. This type of analysis can be very time consuming, which makes it difficult to use as a trade study tool early in the project life cycle. In many cases, only one or two iterations can be performed over the course of a project. This limits the design space to best practices since it may be too difficult, or take too long, to test new concepts analytically. In order to overcome this challenge, automation, and a standard procedure for performing these studies is essential. A methodology was developed within the framework of the Comet software tool that captures the basic inputs, outputs, and processes used in most STOP analyses. This resulted in a generic, reusable analysis template that can be used for design trades for a variety of optical systems. The template captures much of the upfront setup such as meshing, boundary conditions, data transfer, naming conventions, and post-processing, and therefore saves time for each subsequent project. A description of the methodology and the analysis template is presented, and results are described for a simple telescope optical system.

The position of the projection lens in a lens mount needs to be fixed using bolts in the alignment process. The lens mount is need bolts to fix lens in correct position. The bolt joint stress causes the mount and lens to deform. The bolt's number increase can help the bolt joint force effect decline, thus this project is design 8 bolts to fixed mount. The weight of each projection lens is about 2.5 kg, and the total lens assembly weighs about 35 kg. Thus, the effect of the gravity force on the lens surface needs to be considered. The lens bolt joint and gravity force will introduce optical aberration to the wavefront error of the system. The optical aberrations include two parts: lens surface deformation and lens-stress Optical Path Difference (OPD). This study applied the Finite Element Method (FEM) to calculate the lens surface deformation and lens stress distribution by the bolt joint and gravity force. The lens deformation in the optical axis direction can be fitted by a Zernike polynomial. The stress OPD is calculated using incident rays passing through the stress-affected glass parallel to the optical axis. The calculation results can be used to evaluate the effects of the bolt joint and gravity force on the projection lens assembly.

In this contribution we discuss a combined optical and thermal simulation approach which allows us to model the thermal load of the phosphor elements of phosphor converted LED packages with high accuracy. It relies on iterative optical and thermal simulations using ASAP, which is a ray-tracing tool, for the optical simulation parts and the open-source-software gmsh/GetDP for the thermal simulations. The simulation procedure starts with the determination of the absorption intensity of the blue LED light within the phosphor layer. This absorption intensity is the input parameter for the first thermal simulation step. The thermal simulation provides the temperature distribution inside the phosphor layer which again is the input parameter for the next optical simulation step. This iterative combination of optical and thermal simulations allows to consider also the temperature dependency of the optical properties (temperature dependent luminescence loss of the phosphor, thermo-optic coefficients…) of the respective materials. The consideration of temperature induced effects is a prerequisite for an accurate simulation of the optical performance of phosphor converted LEDs, like the CCT values or temperature induced color shifts upon operation. The iteration procedure is continued until the simulated temperature distribution of the phosphor layer becomes stable which is one possible stop criterion. The simulations are verified by experimental characterisation of LED packages fabricated in accordance with the simulation model. We show that using such an iterative simulation approach allows a much more appropriate prediction of the thermal load of phosphor converted LEDs than simple thermal simulations do.

This paper presents the optomechanical analysis of the thermal effect by the finite difference method (FDM) in refraction optical components. The incident rays through the FDM elements, the temperature, or the stress in the ray path are estimated by weighting. The weighting will introduce some error in the calculated optical path difference (OPD) and bring some high-frequency aberration into the optical simulation; therefore, the mesh design process must consider the optical ray path footprint. The incident and emergence rays’ footprints are associated at the lens surface by Patran software; those associated footprints will add into the mesh point at the lens surface. The incident rays separate into several sections; each section can find its nearest grid point in the lens FDM mesh. Thus, moving the nearest grid point to the incident ray section can reduce the weighting or interpolation error in OPD calculations. The calculation results can evaluate the thermal or stress effect in optical transmission components more accurately.

The uniformity of lattice arrangement plays an important role in industrial processing, science and technology studies and environmental pollution detection. However, there are very little papers to study surface structure by depolarization characteristics. In order to improve the efficiency and accuracy of material identification system by polarization technology, we developed a new method to decompose the Mueller matrix, we studied the mechanism of the scattering of electromagnetic wave, and analyzed the relationship between the characteristics of depolarization and mechanism of scattering. We used the Jones Matrix and Mueller Matrix to set up the physical model, and decomposed the Mueller-Jones Matrix by the characteristics of polarization, then got the depolarization coefficients (ωd) of the surfaces of the samples. By using this theory, we deduced the relation formula of Mueller matrix, Mueller-Jones matrix and Isotropic-Depolarizer matrix. Based on the polarized characteristics of the samples, we analyzed design method of material identification system and gave the results of the experimental test. Finally, we applied the theory of Fresnel formulas to verify the theoretical model. From the results, we found that the depolarization coefficients of the samples’ surfaces were related to the scattering, and in the whole measurement process, the depolarization coefficients of the samples were far different; the method could easily to distinguish the metal and nonmetal, and more quickly to analyze the surface roughness of the samples. Therefore, the depolarization technology had a great application value, and the paper had very important significance on the development of surface structure study.

Effects of glue bonding area and bonding thickness on an eight-inch BOROFLOAT® reflective mirror have been studied numerically and experimentally. The comparison of optical aberrations under the self-weight loading and temperature difference has also been investigated. RTV566 has been selected to bond the mirror with on a ring support mount. The optimum glue bonding area and bonding thickness for isolating the temperature variation have been obtained through a design optimization process and then been used practically. A laser interferometer with a wavelength of 632.8 nm has been used to observe the optical path difference pattern and aberrations. The influence of ambient temperature on the mirror with the optimum glue bonding area and thickness has been carried out. It is concluded that the optimum design of the glue for isolating the temperature variation has been attained numerically and verified successfully with the experimental observations.

Dust is one of the most critical issues in assembly of Compact Camera Module (CCM) for mobile phones. Defect due to dust entry or dust deposit severely degrades image quality. There have been lots of literatures about the compensating of dust defect on images by image processing, but the discussion about where the dust locates is still deficient. Dust may sneak in the CCM in any step of packaging process, so the analysis of the dust location may be useful for improving of the production line. This work develops an optical inspection algorithm to detect the location of dust inside CCM based on imaging optics. A planar light source with uniformly emission is designed as the capture target. A series of defocused images are then taken and analyzed. According to the dependence of the image defect on the capture distance, the location of the dust can be well defined. This inspection algorithm provides an easy and efficient way to help manufacturers improve their packaging process.

In this work, the photodegradation of a polymer optical fiber with Rhodamine doped cladding as a function of illumination time and excitation intensity is presented. To show the effect of photodegradation on different bulk geometries and environments, the photodegradation from a dye doped preform and a PMMA thick film is also evaluated. The reversible and the irreversible degradation of the florescent material were quantified under an established excitation scheme. To this purpose, a four-level system to model the photodegradation rates and its relation with the population of the states is presented and it is used to justify a possible underlying mechanism. The obtained results suggest an increase of one order of magnitude in the stability (lifetime) of the polymer optical fiber with respect to the preform or the thick film geometry stability.

In this study, we propose a fast rebuild technology for evaluating light quality in large areas. Outdoor light quality, which is measured by illuminance uniformity and the color rendering index, is difficult to conform after improvement. We develop an algorithm for a lighting quality mapping system and coordinates using a micro spectrometer and GPS tracker integrated with a quadcopter or unmanned aerial vehicle. After cruising at a constant altitude, lighting quality data is transmitted and immediately mapped to evaluate the light quality in a large area.

In this work we present a method used to study the spherical and chromatic aberrations contribution near the focal point of a refractive optical system. The actual focal position is measured by scanning a pinhole attached on the front of a power detector, which are scanned along the optical axis using a motorized stage with 1 μm resolution. Spherical aberration contribution was analyzed by changing the pupil aperture, by modifying the size of the input iris diaphragm and for each case, measuring the actual laser power vs the detector position. Chromatic aberration was analyzed by performing the same procedure but in this case we used an ultra-broad-band femtosecond laser. The results between ML and CW operation were compare. Experimental results are presented.

Photoelasticity is a stress measurement method extensively used in test laboratories of materials. This method can be a reference to validate numerical calculation of stress and strain distributions, however we need to evaluate errors and uncertainties to know the reproducibility of the method in order to compare with numerical calculation. Some transparent materials present birefringence when they are stressed. In a first approximation the birefringence depends of the stress in a linear way, the proportionality constant is known as stress-optic constant. When polychromatic light is used the wavelength becomes other important parameter for the method. Therefore the stress-optic constant is a source of error and uncertainty, also the resolution of the wavelength is a second source of error and uncertainty. In this work we present an evaluation of the sources of errors and uncertainties of the photoelasticity method for stress and strain measurements.

This paper presents the finite element and wavefront error analysis with reverse engineering of the primary mirror of a small space telescope experimental model. The experimental space telescope with 280mm diameter primary mirror has been assembled and aligned in 2011, but the measured system optical performance and wavefront error did not achieve the goal. In order to find out the root causes, static structure finite element analysis (FEA) has been applied to analyze the structure model of the primary mirror assembly. Several assuming effects which may cause deformation of the primary mirror have been proposed, such as gravity effect, flexures bonding effect, thermal expansion effect, etc. According to each assuming effect, we establish a corresponding model and boundary condition setup, and the numerical model will be analyzed by finite element method (FEM) software and opto-mechanical analysis software to obtain numerical wavefront error and Zernike polynomials. Now new assumption of the flexures bonding effect is proposed, and we adopt reverse engineering to verify this effect. Finally, the numerically synthetic system wavefront error will be compared with measured system wavefront error of the telescope. By analyzing and realizing these deformation effects of the primary mirror, the opto-mechanical design and telescope assembly workmanship will be refined, and improve the telescope optical performance.