In even the cleanest of environments, surfaces in optical systems are susceptible to the collection of dust. Because scattering from such contaminants can interfere with the intended operation of the system, it is important to consider their effects during the design via modeling and simulation. A standard developed by the Institute of Environmental Sciences and Technology (IEST) is most commonly used to define the typical sizes and density of particulates on a surface, which can then be used to create a BSDF profile of the contaminated surface. This BSDF profile can be applied to the smooth surfaces within a model to simulate the effects of the contaminants, making up a critical part of the stray light analysis for an optical system. The limitation of such an approach, however, is that the scattering events occur stochastically, with no spatial consistency. In this work a modeling approach is examined that considers the particulates to be stationary on the surface which is more realistic. With the particulates stationary, it is possible to isolate the effects of an individual particle, which can be especially useful for small scale systems. A variety of application designs are investigated through the use of computer simulation to demonstrate the advantages of the isolated contamination scattering approach.
Color uniformity is an important performance metric for many solid-state lighting systems, particularly those systems that use multiple light-emitting diodes (LEDs) to produce the desired illumination distribution. Once the optical design is done, however, it is important to understand how the color uniformity changes when LEDs from within a single color-bin are mixed. Can the design tolerate any LED within the color-bin? Are the inter-bin color variations noticeable in the beam distribution? Are they noticeable when looking back at the luminaire? This paper looks at this question using an exterior automotive stop lamp. The statistical variation of color uniformity is analyzed using assumed interbin statistical variation for the color of the LEDs.
Through the ongoing educational outreach activities of the NES/OSA, we have been invited on several occasions to present optics workshops to students of many ages and backgrounds. With a nearly-overwhelming plethora of optics topics that could be presented, we have decided to develop a curriculum on color science that can be presented in a workshop format. Color science was chosen due to the wealth of examples of the application of color within a student’s culture, society, technology, and experiences. The goal of the workshop is to teach basic color science by examining objects and events that the students can experience or interact with in their own lives. The curriculum can be scaled to match groups of different sizes and backgrounds as well as to fit within certain time constraints. Depending on logistics, a variety of hands-on demos can be presented, or the workshop can be fully tutorial-based. This curriculum has been presented several times and is constantly evolving based upon each experience. In this paper, we present the portions of the curriculum that have been developed to date. We discuss considerations for adding or removing sections to meet specific workshop constraints. We will also present the evolution of the curriculum from inception to its current state, highlighting the lessons learned from each presentation of the curriculum.
Color science is perhaps the most universally tangible discipline within the optical sciences for people of all ages. Excepting a small and relatively well-understood minority, we can see that the world around us consists of a multitude of colors; yet, describing the “what”, “why”, and “how” of these colors is not an easy task, especially without some sort of equally colorful visual aids. While static displays (e.g., poster boards, etc.) serve their purpose, there is a growing trend, aided by the recent permeation of small interactive devices into our society, for interactive and immersive learning. However, for the uninitiated, designing software and hardware for this purpose may not be within the purview of all optical scientists and engineers. Enter open source. Open source “anything” are those tools and designs -- hardware or software -- that are available and free to use, often without any restrictive licensing. Open source software may be familiar to some, but the open source hardware movement is relatively new. These are electronic circuit board designs that are provided for free and can be implemented in physical hardware by anyone. This movement has led to the availability of some relatively inexpensive, but quite capable, computing power for the creation of small devices. This paper will showcase the design and implementation of the software and hardware that was used to create an interactive demonstration kit for color. Its purpose is to introduce and demonstrate the concepts of color spectra, additive color, color rendering, and metamers.
White light-emitting diodes that use down-converting phosphors have been utilized in the illumination industry for
several years. In many cases, little information needs to be known about the physics and performance of the phosphor
itself to design, optimize, and simulate the light emission of the LED for the purpose of creating secondary optics.
However, the importance of accurately accounting for the effect of the phosphor cannot be overstated when designing
the LED package or when performing a tolerance analysis, for instance. The difficulties in gathering or measuring the
relevant performance metrics of the phosphors are significant barriers to achieving accurate predictions in illumination
This paper describes a simple, repeatable process to measure several phosphor performance metrics that are used, in
turn, to create a model of the same phosphor in a commercially-available illumination software package. The measured
values are used either as direct inputs or are used to derive the proper inputs for the software. Derivations and discussion
about the software model are included. The performance of the simulated phosphor will then be compared and
correlated to the physical measurements. Finally, a model of an LED that uses this phosphor model is built in software
and its simulated performance is compared to measured values.
Even the best optical designs can be ruined by unwanted light: flare in the form of ghost images and veiling glare. The
analysis of stray light in an opto-mechanical system is a step in the design process that is often limited to ghost image
analysis by the optical designer. In many large design groups, stray light analysis is traditionally performed by optical
engineers with very specialized analysis tools that are difficult to master. However, recent improvements in software
packages are now offering tools that allow less experienced designers access to tool sets that can perform flare and
veiling glare analysis for a substantial subset of optical design problems. This paper outlines an effective and efficient
design process for determining the types and magnitudes of stray light in an optical system and demonstrates its use on
an injection molded plastic lens assembly. We describe a capability that locates all of the optical paths and their relative
magnitudes through an optical system and separates them into one of three categories: image path, ghost paths, or veiling
glare. We then describe how to leverage this information to determine the most effective removal method for the "worst