Volume 2, Issue 1

The modern miniature camera lens is the most prolific design manufactured today, yet its design form and origins are often not well understood. This paper illuminates the ancestry of the modern miniature camera lens by developing the lens form from ‘scratch.’ Starting with the Wollaston meniscus of 1812, the lens is designed progressively, employing incremental design decisions aimed at correcting limiting aberrations at each step. The result demonstrates an ancestry that is distinctly different than that of the common large-format objective lenses.

The optimization method damped least squares method (DLS) was almost completed late in the 1960s. DLS has been overwhelming in the local optimization technology. After that, various efforts were made to seek the global optimization. They came into the world after 1990 and the Global Explorer (GE) was one of them invented by the author to find plural solutions, each of which has the local minimum of the merit function. The robustness of the designed lens is also an important factor as well as the performance of the lens; both of these requirements are balanced in the process of optimization with GE2 (the second version of GE). An idea is also proposed to modify GE2 for aspherical lens systems. A design example is shown.

There are many good books for optical designers, so we decided not to repeat basic and classical issues, but to answer frequently asked questions which students have put to us during our long-time teaching experience in optical design on different levels – from very beginners to advanced professionals from the EU who came for the project SMETHODS to improve their design skills. This tutorial is divided into two parts: general questions and examples, when students ask how to design some popular schemes.

Much publicity has been given to the art and science of choosing glass types for the reduction of secondary color, particularly for systems (such as achromats) in which all the elements are in contact. Although it has long been recognized that airspaces between elements can influence chromatic aberration and can even be used to reduce or correct secondary color, comparatively, little emphasis has been placed on this in the published literature. This tutorial is intended to call attention to the induced component of secondary color and suggests methods for improving color correction.

In order to best assess the importance of new technologies to optical design, it is useful to consider what the limits are to what can be done with ‘old’ technologies. That may show where something new is needed to overcome the limitations of existing optical designs. This article will give a survey of some remarkable high-performance designs, some of which are extremely simple, and most of which only use technology that has already been around for decades. Each of these designs has some limitation that would be nice to overcome. One new technology that will probably revolutionize optical design will be curved surfaces on image chips.

Axially asymmetric optical systems treated in this paper contain both freeform surfaces and spheres. In these systems, freeform surfaces need to be allocated at the most effective position. The problem can be elegantly solved with the method of traveling freeform surfaces. The purpose of this paper is to show that the sensitivity control can be included in this design process.

This paper discusses extrinsic aberrations in optical systems and provides formulas for their computation. Extrinsic aberrations result when two optical systems are combined, and there is a mismatch between the exit pupil of the first system and the entrance pupil of the second system. Some significant aberration corrections can take place as a result of extrinsic aberrations.

Advances in slow-servo single point diamond turning enables fabrication of freeform optical elements. Freeform optical elements, which are by definition rotationally non-symmetric, will have a profound importance in the future of optical technology. Historically, orthogonal polynomials added onto conic sections have been extensively used for description of optical surface shapes. More recently, local shape descriptors, specifically radial basis functions, have been investigated for optical shape description. In this paper, we reveal an efficient and accurate localized hybrid method combining in one implementation assets of both radial basis functions and ϕ-polynomials for freeform shape description, uniquely applicable across any aperture shape. Initial results show that the proposed method yields subnanometer accuracy with as few as 25 terms of ϕ-polynomials. Subnanometer accuracy is required for the stringent conditions of lithography and related precision optics applications. Less stringent conditions are also shown to be achieved with as few as 16 terms ϕ-polynomials.

Stemming from the exceptional results obtained with the pathfinding NTT telescope commissioned in 1989, the current generation of large astronomical telescopes, including the VLT, Gemini, Subaru, LBT, VST, and many more, use an active primary mirror in conjunction with the position of the secondary mirror to optimize performance with a cycle time typically measured in minutes over the course of acquiring a long exposure image. Recent discoveries, based in research enabled by the nodal aberration theory (NAT), have created a complete, linear model for the effect of, and the interaction of, the alignment compensators used during an exposure when an active primary mirror has a role in the process of maintaining performance in combination with the rotation of the secondary mirror around a specific external pivot point. This scenario, presented in the context of NAT, clearly illustrates important, limiting interactions between the secondary mirror position and the primary mirror astigmatic figure residual created through active control. It also points to the need for the wavefront sensor algorithm to anticipate that the astigmatic field will be binodal. The science of weak galactic lensing is exceptionally sensitive to binodal astigmatism, making this aberration field an urgent area of research.

We review the motivations and intended benefits of orthogonalized representations of aspheric shapes and demonstrate unexpected gains for design purposes. Leaving aside improvements in ‘design for manufacturability’, we show that local optimization within standard design codes can find solutions with better optical performance when orthogonal descriptions are employed. Our examples include rotationally symmetric systems as well as systems with no global axis of symmetry and even a system of freeform surfaces (i.e., with no individual axes of symmetry).

A new form of field corrector for astronomical telescopes with paraboloid primary mirrors is described. Like an earlier design by Wynne, it consists of four spaced lens elements with spherical surfaces only. In commonly occurring circumstances, the new design gives better image sharpness than does Wynne’s. The new system outperforms Wynne’s system for any probable wavelength range, when the field of view exceeds ~50 arc-minutes. Wynne’s original system tends to work better for narrower fields of view with a larger wavelength range. Also, the new system is closer to being telecentric than Wynne’s, which is of interest to the developers of multifiber-fed systems. Further, the geometry of the new system should yield a modestly reduced manufacturing cost.