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'Braincell' circuits to solar orbits: the future of optics

03 Oct 2006

Subjects as diverse as automatic optimization of optical systems, the likely arrival of nanoelectronics at a "super-human" component density and the design of optics for a near-sun solar orbiter were discussed at a recent conference in London.

A resurrected Optical Designers' meeting took place at the end of September at Imperial College, London. An enthusiastic audience comprising academics, industrialists and consultants heard a cross-section of presentations from six software, hardware and systems developers.

Organizers Tina Kidger, of Kidger Optics, and Andy Wood, of Qioptiq, said they were very pleased that the quality and interest of the presentations had kept to the spirit of an earlier series of meetings begun in the 1980s.

The meeting was sponsored by Optical Research Associates, US, and Qioptiq, UK.

The presentations

• David Williamson, Nikon Research Corp. of America: Optical design for microlithography - is the singularity near?

In this case, the singularity means the point at which the density of transistors on an integrated circuit exceeds the equivalent density of synapses in the human brain. Williamson referred to the noted scientist and polymath Ray Kurzweil's observations about the singularity and its implications for improved artificial intelligence. Kurzweil said that "by 2020 we should be able to have the power of the human brain in a personal computer for $1000".

Williamson said that improved optics design, especially at the nanometer level, but also concerning soft X-rays, were permitting the writing of ever smaller components on semiconductor substrates, and would be a significant tool for maintaining the Moore's Law condition of improving computer performance.

"From its unlikely origins as a superior alternative to contact printing, and in spite of increasingly expensive photons and lenses or mirrors, optical projection remains the preferred lithographic technology," Williamson said. "Many competing technologies, such as proximity X-ray and projection e-beam have been attempted, but failed."

"The current contender is nano-imprint. We may speculate whether the traditional advantages of reduction projection optics will keep it dominant for at least another decade. If so, opportunities for innovation remain for the optical designer and modeler, as fundamental limits are being reached and physical optics effects become more significant."

• Stuart David, Optical Research Associates: Automatic optimization of non-imaging systems

"Non-imaging optimization has challenged optical design software vendors for many years. But thanks to the maturity of computers and new algorithms, NIO is now a powerful tool that can increase productivity and performance in robust optical systems," David said.

"Considering imaging versus non-imaging situations, there are two notable differences: the merit/error function and the noise," said David. "The number of different error functions for imaging systems is finite, including RMS spot size and MTF. In contrast, the number of different error functions for a non-imaging system is almost infinite, depending on system parameters."

ORA is releasing a new package - LightTools V5.4 (Beta) - which features the three main components required for optimizing a particular optical system: the "merit" [error] system; the variable properties; and the constraints. Applications include square illuminance, such as for the optimization of laptop display backlights.

• David Lingwood, Qioptiq: Wide angle hybrid magnifier for a microdisplay source

Lingwood described the design and manufacture of a binocular and occluded optical magnifier, which provides a 45° field-of-view from an OLED microdisplay source.

Whilst global optimization techniques and additional design parameters can improve aberration correction, Lingwood said that the best overall solution comes from applying sound optical design principles. Graphical techniques are also useful in the interpretation of optical performance.

One particular aim of the work was to identify an optical design solution that would require an extension of manufacturing capability in key areas. A notable feature of the design is the use of a surface relief diffractive structure to correct chromatic aberration. A pair of prototype magnifiers have now been manufactured.

• Iain Neil, optical technology consultant: Advances in mirror optics.

Iain Neil is setting up an optical design course at Strathclyde University, while his presentation was based on work at Media Lario Tech SpA.

"There are many types of mirrors but what I am particularly interested in is how they and their components are made," he told the meeting. "Much of the cost in today's mirrors is concerned with assembly and alignment rather than making the individual components themselves. Considering some systems that are used, such as in 8-13µm infrared scanning, this in particular contains multiple mirrors, in this case two spherical mirrors and a six sided rotor."

Metallic, electro-formed mirrors are becoming more commonplace for high energy lightweight applications. Silicon carbide mirrors are being proposed for space-based imaging systems. Electro-forming is known for its relatively low accuracy because the process is hard to control, so the shape of the mirror is less predictable.

Applications are in: automotive, such as a night driving system; unmanned aircraft / UAV and aerospace, and EUV-DUV lithography.

• Andy Harvey, Heriot-Watt University: Wavefront coding: a new dimension in optical design.

"Applications of wavefront coding are in lens design: for example, developing low-cost lenses for phone cameras or for microscopy with a larger depth of field," said Harvey.

According to Harvey, wavefront coding offers better control over aberrations, increased instrument depth of field, and focus-free operation. Other benefits include less focus-related aberration, more relaxed lens tolerancing, and reduced lens control and light intensity at the detector.

• Kevin Middleton, Rutherford Appleton Laboratory: Optical Design of the EUV Spectrometer for Solar Orbiter

The Solar Orbiter mission, currently scheduled for launch in 2015, will study the sun in unprecedented detail from a distance of only 0.2 a.u. (approx. 30 million km). Among the instruments on-board will be an imaging spectrometer in the extreme ultra-violet. Middleton reviewed the instrument's optical design, including aspects such as competing first-order optical layouts, performance trade-offs and the management of thermal loads.

Optical designers meetings - background

The UK Optical Designers Meetings were introduced by Professor Walter Welford and [the late] Dr Michael Kidger at Imperial College, London, in the early 1980s. The meetings were intended to enable young optical designers to meet with colleagues and discuss the latest research and developments.

Kidger continued to organise the meetings, followed by Jon Maxwell (Cooke Optics) and Richard Bingham, known for his work at the Royal Observatory, Herstmonceux.

After Richard Bingham's untimely death, there was a lapse of about two years, when it was decided that this important date in the optical design calendar should be reinstated. Tina Kidger of Kidger Optics Associates and Andy Wood of Qioptiq Ltd, worked together to invite the six speakers to contribute to the latest meeting and to invite original and new members of the optical design community to the meeting.

Next year's Optical Design Meeting will be held at (and sponsored by) the Rutherford Appleton Laboratory, on Wednesday, 19 September 2007. If you would like to be on the mailing list please contact either tina@kidger.com or andy.wood@uk.qioptiq.com.

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