Design and analysis of an optical system is often a multidisciplinary task, and can involve the use of specialized software packages for imaging, mechanics, and illumination. This paper will present a case study on the design and analysis of a basic heads-up display (HUD) for automotive use. The emphasis will be on the special requirements of a HUD visual system and on the tools and techniques needed to accomplish the design. The first section of this paper will present an overview of the imaging design using commercially available imaging design software. Topics addressed in this section include modeling the windshield, visualizing the imaging performance, using constraints and freeform surfaces to improve the system, and meeting specific visual performance specifications with design/analysis methods. The second section will address the use of a CAD program to design a basic mechanical structure to support and protect the optics. This section will also discuss some of the issues and limitations involved in translating data between a CAD program and a lens design or illumination program. Typical issues that arise include the precision of optical surface prescriptions, surface and material properties, and the management of large data files. In the final section, the combined optical and mechanical package will be considered, using an illumination design program for stray light analysis. The stray light analysis will be directed primarily toward finding, visualizing, and quantifying unexpected ray paths. Techniques for sorting optical ray paths by path length, power, and elements or materials encountered will be discussed, along with methods for estimating the impact of stray light on the optical system performance.
The M-squared (M2) parameter for defining laser beam quality is a convenient metric to characterize the variation of the beam size and far field divergence of a “real” propagated optical beam, compared with that of an ideal Gaussian beam of the same wavelength. However, it can be problematic to use this parameter solely to characterize an input beam for propagation simulation software. Similar to RMS wavefront error or Strehl ratio, which can be used to define image quality, but do not characterize the shape of the wavefront, different factors can result in beams with identical M2 values, but very different propagation behavior. Beams that differ due to aberrations, non-Gaussian amplitude envelopes, and/or partial spatial coherence may have similar or identical M2 values, but very different far-field and/or near-field intensity and/or phase distributions. The situation is complicated further if the beam encounters non-ideal optics. In this paper, we investigate a number of beams that all have (approximately) the same M2. While M2 is invariant for propagation through an ideal optical system, we show that when an optical system introduces aberrations, it can alter different beams with the same, non-unity M2 in ways that differ significantly from one beam to another.
The performance of an optical system can be degraded by the intrusion of stray light form sources both inside and outside of the system field of view. Stray light, or 'veiling glare,' can be particularly distracting in visual systems such as Helmet Mounted Display (HMD) systems. This paper describes techniques used by the authors to map stray light sources positions in the far field for HMD systems and to quantitatively define their impact. The mapping can be performed over 4(pi) steradians both inside and outside the system field of view. Monte-Carlo ray tracing algorithms are utilized for determining that separates the veiling glare component from the desired optical signal components. Once the major veiling glare source positions are identified, methods to reduce veiling glare can be determined. A technique for reducing noise in the calculation due to the statistical nature of the Monte Carlo ray trace is also discussed.
This paper discusses techniques used to design and analyze the performance of a new series of modern injection-molded ophthalmic progressive addition lenses (PALs). Although essentially a singlet, the complicated front surface profile of PALs leads to significant design and analysis challenges.
Precision plastic optical systems frequently depart from traditional design geometries and often include integrated optical and mechanical features. Light can often propagate through the plastic "mechanical" features as easily as through the optical surfaces. This paper discusses modeling and analysis techniques that have been used successfully to quantitatively evaluate energy collection and stray radiation performance in several unusual plastic optical systems. Examples will include a fluid flow sensor and an injection molded plastic triplet imaging system.
Precision plastic optical systems frequently depart from traditional design geometries and often require unusual design methods to incorporate mechanical structures with optical surfaces, to evaluate radiometric performance, or to study stray light issues. This paper discusses modeling techniques that have been used successfully to design and analyze several unusual plastic optical systems. Examples include use the of non-sequential ray tracing in conventional optical design programs as well as solid-model-based design programs for the purposes of evaluating stray light and radiometry features associated with integrated optical and mechanical surfaces in molded components.
Narcissus has been understood by FLIR (Forward Looking Infrared) designers for many years. The purpose of this paper is not to elevate the engineering state-of-the-art, but rather, to give an overview of the problem starting with early FLIRs, look at what is being faced by current designers, and to extrapolate future trends.